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SAN FRANCISCO MUNICIPAL RAILWAY FLEET ENGINEERING

ALTERNATIVE FUEL PILOT PROGRAM

INITIAL 6 MONTH EVALUATION RESULTS

for

2 CNG 40-FOOT BUSES

2 HYBRID/ELECTRIC 40-FOOT BUSES

2 CLEAN DIESEL W/ PM FILTER 40-FOOT BUSES

2 CLEAN DIESEL CONTROL 40-FOOT BUSES

 

Working Draft

May 2002

 

ABSTRACT

The San Francisco Municipal Railway (Muni) is committed to reducing air pollution in San Francisco.  One of the most significant ways that Muni helps to reduce pollution is to provide safe, reliable public transportation.  With more people on transit, fewer cars on the road means less pollution.  Muni also demonstrates its commitment to clean air by operating low-pollution vehicles.  Fifty-three percent of Muni's active revenue fleet is pollution-free, including 203 rail vehicles and 332 electric trolley buses that generate zero pollution.  Forty percent of Muni's buses are zero-emissions buses.  Almost all of the electricity on which those vehicles run is generated by hydropower, a clean source of energy.  Most of the diesel buses in Muni's fleet are new, and thus generate lower emissions.  By December 31, 2002, the remainder of the diesel buses will be rebuilt with kits that reduce soot emissions.  The diesel buses which have not been rebuilt will be retired from the active fleet.  Muni operates 18 vehicles that are powered by compressed natural gas (CNG) in its non-revenue fleet.  Muni is continuously seeking new ways to reduce pollution.

Some of Muni's emissions-reduction programs were borne out of an agreement between the San Francisco County Transportation Authority (SFCTA) and Muni.  In March 2001, the SFCTA attached a set of 11 conditions to TA Resolution 01-08, which authorized Muni's purchase of 95 diesel motor coaches.  Those conditions are included in the Muni Bus Purchase Proposal, commonly referred to as the "11-Point Agreement."  A copy of this agreement is included in Appendix A.  The highlight of the 11-point agreement is this 6-month review of Muni's Alternative Fuels Pilot Program (AFPP).

The AFPP is designed to allow Muni to identify the most appropriate low emissions bus technology to work within the constraints of San Francisco's unique terrain and duty cycle performance demands.  Additionally, the program will allow Muni to identify associated facility support requirements.

Data will be collected for 24 months on eight (8) buses representing four (4) categories of transit bus technology.  This data will be examined to determine the impact of the various characteristics of each technology to Muni, such as performance, emissions, reliability factors, cost per mile, capital costs for the buses and facilities improvements, any safety concerns, and operator and passenger feedback.  Results of similar studies may also be integrated in Muni's analysis and recommendations.

This 6-month preliminary report and update will feature an overview and summary of the pilot project, with summary discussions and graphical data representation.  Additionally, each data collection category will contain an evaluation procedure documenting the technical details related to the collection and analysis of the data gathered during the AFPP.  Once the study is finished, Muni can then determine the viability and impact of each technology.  These results will impact future bus procurements. The AFPP is designed to ensure that Muni will become experienced at adapting to and operating with the newest and least polluting bus technologies while posing the least risk to Muni's ability to meet service standards required by Proposition E.


TABLE OF CONTENTS

EXECUTIVE SUMMARY

INTRODUCTION

EMISSIONS

TAILPIPE EMISSIONS

EXHAUST ODOR

EXHAUST OPACITY

VEHICLE NOISE LEVELS

PERFORMANCE

ACCELERATION AND TOP SPEED

OPERATION TIMES

FUEL ECONOMY

RANGE

OPERATIONS

OPERATOR FEEDBACK

PASSENGER FEEDBACK

MAINTENANCE

RELIABILITY

20-HOUR PERFORMANCE

MAINTENANCE FEEDBACK

COST

OPERATING COST

CAPITAL COST

FACILITY COMPLIANCE

VEHICLE SAFETY CONCERNS

APPENDIX A

APPENDIX B

APPENDIX C

 

INDEX OF TABLES

 

TABLE 1:  AFPP VEHICLE SPECIFICATIONS

TABLE 2:  Exhaust Opacity Levels

TABLE 3:  Exterior Noise Level Summary (Graph)

TABLE 4:  Exterior Noise Level Overview (Graph)

TABLE 5:  Interior Noise Level Summary (Graph)

TABLE 6:  Interior Noise Level Overview (Graph)

TABLE 7:  Top Speed Summary (Graph)

TABLE 8:  Relative Top Speed (Graph)

TABLE 9:  Acceleration Times Summary (Graph)

TABLE 10: Relative Acceleration (Graph)

TABLE 11: Average Time Between Each Stop (Graph)

TABLE 12: Average Total Trip Time Between Stops (Graph)

TABLE 13: Fuel Economy

TABLE 14: Vehicle Range

TABLE 15: Driving Characteristics

TABLE 16: Reliability Rates

TABLE 17: Maintenance Survey - Relative Reliability Rates

TABLE 18: Fuel Cost Per Mile

TABLE 19: Maintenance Cost Per Mile

TABLE 20: Total Cost Per Mile

TABLE 21: New Bus Cost Summary

TABLE 22: Infrastructure Requirements Comparison

TABLE 23: Incremental Facility Costs Comparison


EXECUTIVE SUMMARY

The Alternative Fuel Pilot Program (AFPP) has finished evaluating Compressed Natural Gas (CNG), Hybrid, and exhaust after-treatment (PM filter) vehicle technologies during the initial six months in revenue service at Muni.  This program was designed to provide recommendations regarding future Muni motor coach procurements.  San Francisco's unique and challenging transit environment, featuring the City's famous hills, commitment to "transit first" principles, and potential for emergency service requirements in the event of another earthquake, requires a site-specific evaluation of alternative transit technologies.  The test buses were compared to unmodified conventional diesel buses in 19 different categories.  These categories are grouped into the general areas of:  EMISSIONS; PERFORMANCE; OPERATIONS; MAINTENANCE; COST; and SAFETY CONCERNS.

 

The University of California at Davis - Institute of Transportation Studies (ITS) was contracted by Muni to compare the emissions and energy efficiency of the different AFPP technologies.  This comparison was primarily made with a chassis dynamometer[1] using an ITS-designed San Francisco simulation which, for the first time, tested heavy duty vehicle emissions on hills.  Results of this testing are found in the UC Davis-ITS Preliminary Chassis Dynamometer Test Results for Four Types of Advanced Technology Buses presentation, attached at Appendix C.  The detailed UC Davis-ITS Preliminary Chassis Dynamometer Test Results for Four Types of Advanced Technology Buses Report will be available from UC Davis through Muni fleet engineering on June 1, 2002.

ITS and Muni evaluated CNG, hybrid, and exhaust particulate (PM) filter vehicle technologies during their initial six months in revenue service.  San Francisco's unique and challenging transit environment, including the City's famous hills, and commitment to "transit-first" principles required an on-sight evaluation as well as "laboratory" testing on the chassis dynamometer. 

The test buses were compared to unmodified conventional diesel buses in 19 different categories.  These categories are further grouped below into the general areas of:  emissions; performance; operations; maintenance; cost; and safety concerns.

Emissions

 Tailpipe emissions

Researchers at the Institute of Transportation Studies, University of California Davis analyzed the Phase One emissions testing which took place over a period of 6 months.  Eighteen months of testing will continue until the full program concludes, in July 2003.  ITS-Davis staff explained that testing of advanced technology buses is a complex and evolving science.  The tests conducted for Muni thus far were intended to 1) confirm that results were consistent with those reported by other advanced bus technology testing programs and 2) facilitate development of new tests suited to San Francisco's unique terrain and driving conditions. With these caveats, UC Davis offered the following preliminary results of based on the standard emissions tests:

a) the magnitude of emissions were generally consistent with those found in other studies of advanced technology buses operating, 

b)   as is typical of emissions testing, there was a large range of emissions values for each bus,

c) the hybrid, CNG, and diesel buses with traps offered greatly reduced PM emissions compared to conventional diesel buses,

d)   PM emission of CNG, hybrid, and diesel bus with trap were similar and sometimes at the detectable limits of the analyzers, 

e) the CNG buses demonstrated the lowest NOx emissions followed by the hybrid and diesel buses,

f)   CNG buses had the highest CO emissions of any bus,

g) the diesel buses exhibited the best fuel economy and the CNG bus the poorest.  Unlike other testing, the hybrid bus had poorer fuel economy than the diesel.  This can be attributed to the diesel's unexpectedly high fuel economy.

However, these results may not be indicative of the in-use emissions in San Francisco.  San Francisco's unique grade and operations characteristics (such as average speed and idling duration) are not captured in the traditional test cycles discussed above.  ITS-Davis created a preliminary SF specific test cycle using bus speed and road grade information collected on three diverse Muni routes.  Limited testing on the SF Cycle indicates that the fuel economy differences between buses may be less in SF than predicted by the conventional cycles. 

There were several test protocol difficulties that need to be addressed with California Truck Testing Services, the contracted emissions testing facility, prior to the next round of testing. Diesel bus emissions and fuel economy in particular were inconsistent, and there were difficulties with hybrid bus testing.  The testing that was conducted in the first six months of Phase One is insufficient for staff to recommend one type of alternative fuel over another.  The staff of ITS-Davis agrees that more testing is required over the remaining 18 months of the pilot program, in order to achieve more meaningful results. ITS-Davis recommends that they actively participate in the data collection and emissions testing in this next phase.  Comprehensive bus operations and topography data collection could commence in July 2002, and the next round of emissions testing would occur in October 2002.

Visual quality of exhaust

Vehicle exhaust odor was not noticeable by passengers on any of the AFPP buses.  Exhaust opacity, or visual quality, was outstanding on all of the technologies.

Vehicle noise levels

Exterior noise was significantly lower on the Hybrids.  In general, interior noise was lowest on the Hybrids and CNG buses.  PM filters lowered the interior and exterior noise levels of the conventional diesels.

Performance

Performance indicators included top speed and acceleration on different grades, average time between stops, fuel economy, and fuel range.  Grades of up to 21% were used in these performance evaluations.[2]  The following performance indicators were observed:

1) Hybrid buses accelerated faster than any of the other technologies, regardless of grade.  In general, the PM filter buses have the best top speed performance on all grades, followed by the CNG buses.  Preliminary results indicate that PM filters did not degrade the performance of conventional diesel buses. 

2) In challenging operating conditions hybrids gained time on each line trip, while the CNG buses lost time compared to the diesel buses.[3] 

3) The PM filter buses have the best fuel economy and range.  The CNG buses are the least fuel efficient, and hybrid buses have the shortest fuel range.[4],[5]

Operations

Both operators and passengers were surveyed informally for their opinions regarding the alternative technologies.

1) Operators of the AFPP buses preferred the PM filter buses.  However, hybrids were said to be smoother while performing just as well.  Both CNG and hybrid buses were said to have better braking.  In general, operators did not feel that CNG buses were well-suited for hills or high passenger loads.

2) Riders want dependable service first and foremost, but would prefer to ride clean-fuel buses whenever possible.  Riders are generally concerned with all kinds of emissions, but don't view Muni as a major source of pollution.  Most riders feel that a different fuel source probably means a cleaner burning engine.[6]  

Maintenance

Muni moves the equivalent of San Francisco's entire population every day.  Vehicle reliability is crucial. 

1) During their initial 6 months in operation, the PM filter buses were four (4) times more reliable than CNG buses, and 10 times more reliable than the hybrids.[7]  The PM filter buses accumulated more than three (3) times the mileage during their first 6 months compared to the CNG and hybrid buses, partly due to the relatively low reliability rates found so far in the alternative technologies.  Six months is not a sufficient time period in which to test reliability.

2) Mechanics working on the AFPP felt that many maintenance issues could be resolved as their knowledge of the new technology improved. 

Cost

Ongoing operational costs and onetime capital costs were analyzed.  Operational costs include fuel[8] and technology-specific maintenance.[9]  For the purposes of this report both are calculated in terms of cost per mile.  Capital costs include the incremental cost of the vehicles and necessary fueling and facility modifications.

1) Fuel only cost per mile is highest for the CNG buses, and lowest for the PM filter buses.  Technology-specific maintenance costs were also highest for the CNG buses and significantly lowest for the PM filter buses.  Combining fuel and maintenance costs produce the same results.

2) Muni conventional diesel buses with PM filters cost approximately $330,000.[10]  Hybrids currently cost about $120-170,000 more per bus than a Muni diesel bus with PM trap.  CNG buses cost approximately $45-60,000 more per bus than Muni diesel buses with PM traps.  In order to meet CARB emissions standards in 2004, diesel buses must be equipped with aftertreatment technology that will reduce NOx.  The aftertreatment technology that Muni will be testing (EGR) costs approximately $10,000 for each bus.[11]  The cost of CNG buses has dropped as more buses are being manufactured.  An order of 15 hybrid buses would cost approximately $450-500,000 at this time.  However, the price is expected to decline as the technology gains popularity.[12]  Currently, there are 34 hybrid buses in operation in the United States.  In the state of California, eight (8) are in operation, including the two (2) that Muni owns.  In January 2002, Muni requested a federal earmark of $1.5 million for the purchase of alternative fuel buses in the FY03 Congressional appropriations process.  Two other sources of funding are the Program Manager and Regional Funds from the Transportation Fund for Clean Air.  Any public agency can apply for funds from these sources.  The Program Manager fund contains approximately $950,000.  Muni received $500,000 from this fund in FY02 for CNG facilities.  Regional funds total approximately $8 million, but individual annual grants cannot exceed $1 million.  Muni will be submitting an application for funding from the Regional account in May/June 2002.[13] 

3) None of Muni's current facilities are safety compliant with CNG buses.  Fueling and maintenance facilities must be specifically tailored for CNG.  To support a fleet larger than 15 CNG buses, Muni would need to spend roughly $7 million for capital costs associated with one facility.  For additional capacity, the cost to Muni would be an additional $5 million, bringing the total cost to $12 million for capital costs associated with modifications to two facilities.  It is noted, however, that one facility could provide enough capacity for a large purchase of CNG buses.  Capital costs associated with facility modifications for a large purchase of hybrid buses would be about $1.05 million. 

Safety

The safety category is primarily concerned with the hazards of CNG vehicle operation on bridges, through tunnels, under electric trolley contact wires, and inside terminals.  Secondary concerns include threats from intentional harm, and earthquake conditions.

Hazards

In general, the hazard potential from CNG buses during operation is extremely low.  However, it is strongly recommended that certain areas be evaluated further.  Other areas include streets with low trolley wires, where the possibility of an explosion exists in which an errant wire may strike a CNG tank on the top of a passing bus.[14]  Hazards in long tunnels such as Broadway and Stockton present other areas for further evaluation, and should be avoided in the meantime.  A comprehensive safety evaluation and certification must be in place before the procurement of CNG buses or modification of facilities. 

Terrorism

Muni buses operate around City Hall, the Federal Building, the United Nations plaza, the TransAmerica Building, and on the Golden Gate Bridge, which may be considered terrorist targets for various reasons.  Given the volatility of CNG relative to diesel fuel, CNG buses could be considered a target for terrorism.[15] 

Earthquakes

The US Geological Survey states that there is a 67% probability that San Francisco will one day experience another Richter-magnitude 7 earthquake.  During the 1989 Loma Prieta earthquake, electricity and natural gas supplies were unreliable in San Francisco.  Fifty-three percent of Muni's entire fleet is currently electric powered.  In the event of an emergency, with gas and electric supplies cut or reduced, a reliable fuel source will be crucial.  The Independent Oversight Committee (IOC) has suggested that the use of liquefied natural gas (LNG) would obviate the risk of service interruption in the event of an earthquake.  San Francisco's solid waste hauler, NorCal Waste Systems is in the process of converting its fleet to LNG.

Summary

The preliminary results of the AFPP indicate that Muni should continue its testing program.  The past six months of testing has yielded preliminary, and not reliable, emissions results.[16]  Muni may also consider the testing of new technologies, such as LNG, the use of oxidation catalysts, and other aftertreatments in Phase Two of testing.

Muni should also consider the impact of regulations on its future procurements.  California is mandating new emissions standards in 2004-2006.  Even more stringent regulations will be imposed in 2007 by the federal Environmental Protection Agency.  Natural gas buses do meet the 2004 CARB mandate.  Currently, neither conventional nor hybrid diesel buses meet the 2004 mandate although aftertreatment technology and new hybrid certification standards may enable diesel buses to meet the new standards.  Diesel, hybrid, and CNG currently do not meet 2007 standards.

 

INTRODUCTION

BACKGROUND

The mission of the Alternative Fuel Pilot Program (AFPP) is to objectively evaluate alternative fuel technologies so that Muni can make an informed decision when considering propulsion technologies for future vehicle procurements.

This program is designed to determine what additional considerations must be addressed as well as considering which alternative fuel technology is most appropriate for use in San Francisco's unique transit environment.  The AFPP will last for a total of 24 months.  An Independent Oversight Committee, headed by personnel from the City and County of San Francisco Clean Cities Program, acts in the interest of the many citizen groups and environmental organizations that worked to develop the fundamentals of the AFPP.  Preliminary and final recommendations developed by Muni, as well as contingency plans if testing or project scheduling falls behind, will be addressed by this oversight committee.  Should results from similar studies (performed by other transit agencies) be incorporated into Muni's analysis, these studies will be current and evaluated for appropriateness by the Independent Oversight Committee (IOC) prior to inclusion.[17]

PROGRAM MISSION

The goal of this program is to objectively evaluate the performance, reliability, emissions, safety, operating and capital costs of compressed natural gas (CNG) bus, hybrid bus, and exhaust particulate matter (PM) filter bus technologies.  These technologies will be evaluated for 24 months, using conventional diesel buses as a control/base measurement.

PROGRAM OBJECTIVES

The program is set up using the following guidelines:

  Evaluations of new, alternative technology will provide San Francisco specific information so as to lay the foundation for future vehicle procurements.[18]

  Alternative technologies being evaluated include: two (2) CNG buses, two (2) hybrid buses, two (2) exhaust PM filter technology clean-diesel buses, and two (2) conventional clean-diesel control group buses.

  Evaluations of supplemental emissions technology will provide information on the impact of adding California Air Resources Board (CARB) mandated PM filters to clean-diesel buses in the fleet so that they too will exhibit dramatically reduced emissions.  Note that Muni is going ahead with this retrofit on the entire clean-diesel fleet four (4) years ahead of CARB's schedule.

  Fleet engineering will produce periodic and quarterly reports, as well as project summaries/recommendations after six (6) months, 12 months, and after 24 months of testing.

APPROACH

The eight (8) AFPP buses are stored and operated out of Muni's Kirkland and Woods divisions, and maintained at Muni's Marin Street division.  The diesel buses are fueled at Kirkland and Woods, while the CNG buses are fueled at an off-site CNG station.[19]  Three (3) maintenance personnel and up to 50 operators have been specifically trained on the AFPP buses, as well as in the record keeping techniques required for the testing.

DATA COLLECTION

  Tailpipe emission data

  Exhaust odor

  Exhaust opacity

  Interior noise levels

  Exterior noise levels

  Acceleration performance on grades

  Top speed performance on grades

  20-Hour performance

  Total operational trip time and average time between stops

  Fuel economy

  Fuel range

  Operator feedback

  Passenger feedback

  Maintenance feedback

  Reliability rate

  Capital costs

  Operating costs

  Facility compliance

  Safety concerns

 

 

TABLE 1

AFPP VEHICLE SPECIFICATIONS

 

YEAR MAKE ENGINE HP TORQUE (lb*ft) FUEL TRANSMISSION REAR AXLE RATIO FUEL CAPACITY CHASSIS TYPE
2001 Neoplan Detroit Diesel Series 50G 275 890 CNG Allison B500R 5.25 24,000 scf Low-floor
2001 Orion Detroit Diesel Series 30 230 620 Ulra Low Sulfur Diesel (ULSD) None - Electric Motor Drives Rear Axle 8.10 100 gallons Low-floor
1999 NABI Cummins ISM 280W/PM Filter 280 900 Ulra Low Sulfur Diesel (ULSD) Allison B400R 4.56 150 gallons High-floor
1999 NABI[20] Cummins ISM 280 <280 900 Ulra Low Sulfur Diesel (ULSD) Allison B400R 4.56 150 gallons High-floor

 

EMISSIONS

  Tailpipe Emissions

  Exhaust Odor

  Exhaust Opacity

  Vehicle Noise Levels

TAILPIPE EMISSIONS

Category leader:  San Francisco specific results were inconclusive.

SUMMARY

The University of California at Davis - Institute of Transportation Studies (ITS) was contracted by Muni to compare the emissions and energy efficiency of the different AFPP technologies.

 

ITS-Davis staff and Muni evaluated CNG, hybrid, and PM filter vehicle technologies during their initial six months in revenue service. This comparison was primarily made with a chassis dynamometer[21] using an ITS-designed San Francisco simulation which, for the first time ever, tested heavy duty vehicle emissions on hills.

Researchers at the ITS-Davis oversaw Phase One emissions testing over a period of 6 months.  Eighteen months of testing will continue until the full program concludes, in July 2003.  ITS-Davis staff explained that testing of advanced technology buses is a complex and evolving science.  The tests conducted for Muni thus far were intended to 1) confirm that results were consistent with those reported by other advanced bus technology testing programs and 2) facilitate development of new tests suited to San Francisco's unique terrain and driving conditions. With these caveats, UC Davis offered the following preliminary results based on the standard emissions tests:

a) the magnitude of emissions were consistent with those found in studies of advanced technology buses operating,

b)   as is typical of emissions testing, there was a large range of emissions values for each bus,

c) the hybrid, CNG, and diesel buses with traps offered greatly reduced PM emissions compared to conventional diesel buses,[22]

d)   PM emission of CNG, hybrid, and diesel bus with trap were similar and sometimes at the detectable limits of the analyzers,

e) the CNG buses demonstrated the lowest NOx emissions followed by the hybrid and diesel buses,[23]

f)   CNG buses had the highest CO emissions of any bus,[24]

g) the diesel buses exhibited the best fuel economy and the CNG bus the poorest.  Unlike other testing, the hybrid bus had poorer fuel economy than the diesel.  This can be attributed to the diesel's unexpectedly high fuel economy.

However, these results may not be indicative of the in-use emissions in San Francisco.  San Francisco's unique grade and operations characteristics (such as average speed and idling duration) are not captured in the traditional test cycles discussed above.  ITS-Davis created a preliminary SF specific test cycle using bus speed and road grade information collected on three diverse Muni routes.  Limited testing on the SF Cycle indicates that the differences between buses may be less in SF than predicted by the conventional cycles.

Other lessons learned:  There were several test protocol difficulties that need to be addressed with California Truck Testing Services (CaTTS), the contracted emissions testing facility, prior to the next round of testing.  The testing that was conducted in the first six months of Phase One is insufficient for staff to recommend one type of alternative fuel over another.  The staff of ITS-Davis agrees that more testing is required over the remaining 18 months of the pilot program, in order to achieve more meaningful results.  ITS-Davis recommends that they actively participate in the data collection and emissions testing in this next phase.  Comprehensive bus operations and topography data collection could commence in July 2002, and the next round of emissions testing would occur in October 2002.

 

Next steps:  Comprehensive bus operations and topography data collection could commence in July 2002, and the next round of emissions testing would occur in October 2002.  If possible, on-road emissions testing should be used to collect data in addition to chassis dynamometer data.

RESULTS

Results of this testing are found in the UC Davis-ITS Preliminary Chassis Dynamometer Test Results for Four Types of Advanced Technology Buses presentation, attached at Appendix C.  The detailed UC Davis-ITS Preliminary Chassis Dynamometer Test Results for Four Types of Advanced Technology Buses Report will be available from UC Davis through Muni fleet engineering on June 1, 2002.

The objective of ITS-Davis was to measure and compare the mass emissions (carbon monoxide, oxides of nitrogen, hydrocarbons, and particulate matter) and energy efficiency of AFPP buses.

Specific tasks handled by UC Davis included:

  Managing chassis dynamometer-based testing.

  Oversight of emission testing using conventional driving cycle test protocols: the Central Business District (CBD) and New York Bus (NY Bus) Cycles, which have been used extensively in previous research.[25]

  Comparison of the emission test results to those from other large advanced technology bus testing projects.

  To design a San Francisco specific test, conduct preliminary testing on this cycle, and compare the results of this cycle to the results from other cycles.

Phase 1 Uncertainties:

  Typical variation between tests

  Representativeness of test procedure

  Passenger load

  Correction for State of Charge[26]

  SF driving cycle inconsistency

  Sulfur interference with trap

  Testing complexity

 

EXHAUST ODOR

Category leader:  Inconclusive due to confusing survey questionnaire.

 

SUMMARY

Passengers were surveyed for their opinions regarding each technology's exhaust odor as part of the passenger survey.  This is a quality of life issue similar to exhaust opacity.  Results from this survey question are inconclusive.  In general, none of the technologies seems to have a noticeable exhaust odor.

Next steps:  The exhaust odor question should be refined further, and the survey re-administered to a larger sample of passengers. 

RESULTS

Inconclusive.  According to the preliminary survey designer and administrator the survey language must be revised:  "People who think I'm asking 'can you tell right now' say NO. People who think I'm asking 'could you tell if you put your nose up to (the exhaust)' say YES. The question needs to get better so we can see if we are measuring actual perception, or mental perception."[27]

EVALUATION CRITERIA

1. EXHAUST ODOR

1.1.   Evaluation:  Data is collected for each alternative bus technology and a qualitative comparison is made using the Muni's conventional clean-diesel bus fleet as the standard.  Passenger feedback surveys are primarily used to evaluate exhaust odor.

1.2.   Test Procedure:  The surveys are verbally given to passengers while the test bus is in revenue service.  Surveys shall be given to a large number of passengers in order to better represent public opinion.

1.3.   Significant Variables:

1.3.1.   Language:  The survey is given in English only, which may prevent many Muni riders from providing feedback.

1.3.2.   Runs:  The survey is only given on a specific runs only; the survey is only given in certain parts of the city at certain times of the day.

1.4.   Test Personnel:  Test personnel who are clearly identified as being employed by Muni administer the surveys.

EXHAUST OPACITY

Category leader:  All.

SUMMARY

Exhaust opacity is a method of evaluating the visual appeal of a vehicle's exhaust.  This is a quality of life indicator similar to exhaust odor.  Although quantified opacity results differ slightly between each technology pair, the difference between the highest and lowest measured exhaust opacity levels on the test buses is insignificant.  None of the test buses produce visible exhaust smoke under normal operating conditions and the hybrid's exhaust opacity could not be measured.

Other lessons learned:  As anticipated, adding a PM filter to a conventional diesel engine lowered the exhaust opacity.  However, due to Muni's recent conversion to ultra low sulfur diesel (ULSD) fuel,[28] the PM filters in the test program may not be performing to maximum potential with the new fuel.  This because the relatively high sulfur content of the previous fuel tends to partially plug the filter for a period of time.  Once properly cleaned and combined with dedicated use of ULSD, greater opacity reductions are predicted for the diesel powered buses with PM filters (conventional diesel and hybrid).

Next steps:  Since the exhaust gas tester could not measure hybrid exhaust opacity, data should be recollected in order to verify actual levels.  Exhaust particulate filters should all be properly serviced and cleaned by the manufacturers prior to retesting.[29]

RESULTS

Relatively high exhaust opacity levels are an indication of darker exhaust smoke.  The control group conventional diesel buses have the highest exhaust opacity.  The hybrid bus exhaust opacity is apparently so low that it could not be measured with Muni's opacity measurement equipment.[30]  The CNG buses and PM filter equipped diesel buses fall in between the control group diesels and the hybrids.  Overall average levels range from 2.6% to less than 1%[31]

TABLE 2

EXHAUST OPACITY LEVELS:

Vehicle: Exhaust Opacity (%):
CNG 2.45
Hybrid < 1.0
Conventional Diesel with Exhaust Particulate Filter 1.2
Conventional Diesel 2.6

EVALUATION CRITERIA

2. TAILPIPE EXHAUST OPACITY

2.1.   Evaluation:  Data is collected for each bus technology pair and a relative comparison is made using the unmodified diesel bus pair as the standard.  The average percent opacity for each technology type determines the final result for that pair.

2.2.   Definitions:  The visual quality of a vehicle's tailpipe exhaust is measured by a smokemeter in units of percent visual opacity.

2.2.1.   Zero percent (0%) opacity defines clear.  100% opacity defines black.

2.3.   Test Procedure:

2.3.1.   Prior to Testing:  Warm up and calibrate opacimeter.

2.3.2.   Measurement:  Snap accelerate the engine for three (3) seconds, maintain engine speed for the following two (2) seconds, return the engine to idle speed.  Repeat five (5) times.

2.3.3.   Final result:  The average of five (5) opacity reading determines the final result for that vehicle.

2.4.   Vehicle Conditions:

2.4.1.   Operating Temperature:  Test engine should be allowed to reach operating temperature prior to testing.  For purposes of this test, operating temperature has been reached if engine oil temperature is 140 F or above.

2.4.2.   Engine Inspection:  There are no exhaust leaks or misadjusted engine settings.

2.5.   Data Collection Equipment:  An exhaust gas tester is used to analyze the content of black, white and blue exhaust smoke from the test engines.

VEHICLE NOISE LEVELS

Category leader:  Hybrid.

 

SUMMARY

There are two sub-categories for vehicle noise in this evaluation:  Exterior noise and interior noise.  An average of the two highest noise levels measured in each category are represented in these results.

Exterior noise levels are lowest on the hybrids, and highest on the CNG buses.  Interior noise levels are lowest on the CNG and hybrid buses, and highest on the conventional diesel buses. 

Some of the results are misleading.  For example, when the CNG buses are in service, the exterior noise levels are not offensive.  Similarly, the measurably low interior noise levels found on the hybrid buses are misleading.  Qualitatively, the interior noise levels for passengers in the very rear of the hybrids are unacceptably loud.

The exterior noise levels of the CNG buses, and the interior noise levels of the hybrids can be significantly reduced in future purchases through cooling system and noise insulation modifications.  However, it is unlikely that any of the other technologies will be able to match the low exterior noise levels produced by the hybrid buses due to the nature of the technology and layout differences between hybrid technology and conventional bus technology.[32]

Other lessons learned:  Adding PM filters to the conventional diesel buses appears to decrease both interior and exterior noise levels.

Next steps:  Noise level data should be collected while the vehicles are in service in order to supplement data taken under controlled, extreme test conditions.

RESULTS

TABLE 3

 

TABLE 4

 

TABLE 5

TABLE 6

Exterior noise levels for each technology differed significantly.  In general, the hybrid buses produce the least amount of noise, and the CNG buses produce the most exterior noise.  The conventional diesel buses fall in between the alternative technologies when it comes to exterior noise, and they are louder than the alternative technologies inside.  The exterior noise level results for the CNG buses are not as representative of actual operating conditions as the results for the other test buses.  In this case, test conditions require the engine's cooling fan to operate continuously, yet in service the CNG engine cooling fan rarely engages.

Interior noise is clearly split between conventional technology and alternative technology.  The CNG and Hybrid buses are considerably quieter for passengers and operator than the conventional diesel buses. 

Differences in vehicle noise, both interior and exterior, can be greatly influenced by vehicle specifications.  For example, interior noise was greatly raised by the ventilation system on the NABI diesel buses. 

EVALUATION CRITERIA

3. NOISE EMISSIONS

3.1.   Evaluation:

3.1.1.   Technology:  Data is collected for each bus technology pair and a relative comparison is made using the unmodified diesel bus pair as the standard.  The highest overall set of vehicle values for each technology type determines the final results.

3.1.2.   Vehicle:  For each vehicle, at least three (3) readings are taken for each specific measurement.  The two (2) highest readings for each measurement location or condition, within one (1) dBA of each other, are averaged to determine the final noise result for each measurement.  For example, if the curbside idle readings are 67.6 dBA, 67.8 dBA, and 68.0 dBA, then the final result will be 67.9 dBA.  Three (3) significant figures are used to express the final result of all subsets.

3.2.   Definitions:

3.2.1.   Set is defined here as all of the results for a single vehicle in each main noise category: interior and exterior.

3.2.2.   Subset is defined here as a singe category within the main categories of internal and external noise.  For example, noise level results for the driver's area is a subset of interior noise levels.

3.3.   Test Procedure:

3.3.1.   Exterior Noise:  Exterior noise levels are measured on both vehicle curbside and vehicle street side.[33]  The three (3) categories measured are:  Idle; pull-away; and pass-by.  Society of Automotive Engineers (SAE) J366 FEB87 Exterior Sound Level for Trucks and Buses measurement procedure is followed.  In reference to J366 FEB87 section 4.3.3:  The sound level for each side of the vehicle shall be the average of the (2) two highest readings within (1) dBA of each other, rather than within (2) dB of each other.

3.3.2.   Interior Noise:  Interior noise levels are measured at four (4) points in the vehicle:  At the driver area, at the very front seats, at the rear doors, and at the very rear of the vehicle.  All readings are taken at seated head level.  All readings are taken in the middle of the passenger isle, except for the driver area reading.  The driver area reading is taken at head level directly above the operator's seat cushion.  The sound level meter microphone is pointed toward the front of the vehicle during all readings.  Readings are collected as the vehicles are accelerated from zero (0) to 30 mph.  The same city street is used for all measurements.

3.4.   Site Conditions:

3.4.1.   Ambient Noise:  All data is collected in dry weather and still wind conditions.

3.5.   Vehicle Conditions:

3.5.1.   Fans:  Engine cooling fans are configured to provide maximum cooling at all times during testing.  For interior noise testing, all interior fans and heaters are set to provide maximum output.

3.5.2.   Chassis:  All windows, hatches, and doors are closed.

3.5.3.   Passengers:  The vehicle is empty with the exception of test personnel (3.8) and equipment (3.7).

3.6.   Significant Variables:  Every effort is made to eliminate data that may be influenced by an intermittent ambient noise.  If such a noise occurs, it will void the measurement.  Examples of random ambient noise are:  Extremely loud street conditions, a plane flying overhead, or a car horn.

3.7.   Data Collection Equipment:  An SAE J366 approved digital sound level meter is used to determine vehicle noise levels.

3.7.1.   Settings:  Sound meter is set to the "A" scale, fast response.  Meter reading units are decibels (dB), with a resolution of one-tenth of a dB.  The meter's hold feature is used to determine maximum readings.[34]  Every effort is made to disregard readings which may be the result of a sudden ambient noise condition (3.6).  This may cause the meter's hold feature to display the result of the ambient noise spike.

3.7.2.   Repeatability:  The same sound meter is used for all vehicles.  Sound meter is self-calibrating.  Sound meter calibration is verified with an external sound meter calibration device.

3.8.   Test Personnel:  Personnel consist of one (1) driver and one (1) data collector.  The data collector witnesses the test equipment readings and records test results.

3.8.1.   Driver:  The test driver is given simple, consistent verbal and visual commands.  Upon seeing the command to accelerate, the driver will press the throttle pedal immediately to the floor.  The throttle shall remain fully depressed throughout the acceleration run.  Every effort is made to eliminate performance variation caused by different driving styles

 

 

PERFORMANCE

  Acceleration and Top Speed

  Operation Times

  Fuel Economy

  Range

ACCELERATION AND TOP SPEED

Category leader:  Conventional diesel.

Alternative leader:  Hybrid.

SUMMARY

Test buses carrying the equivalent of 85 passengers were tested for top speed and acceleration on 0-21% grades.  The conventional diesel buses have relatively superior top speed performance regardless of grade.  As grade increases, the top speed performance of the hybrid buses improves, while the top speed performance of the CNG buses decreases.

The hybrid buses accelerate faster than any of the other technologies on every grade, with the exception of the 16% grade[35] where they were nearly identical with the acceleration rate of the diesel buses equipped with PM filters.  CNG buses accelerate at a slower rate than the other test buses in every category.[36]

Overall, the hybrid buses are ideally configured for hill climbing and acceleration.  The CNG buses are well suited for level ground, high-speed applications.  The conventional diesel buses perform well in all operating conditions, providing operating flexibility.

Other lessons learned:  Adding PM filters to conventional diesel buses seemed to generally improved both top speed and acceleration.

Next steps:  Future procurements should specify certain performance goals based on the results of this testing, since performance can be greatly influenced by vehicle specifications.

RESULTS

TABLE 7

TABLE 8

TABLE 9

TABLE 10

EVALUATION CRITERIA

4. PERFORMANCE

4.1.   Evaluation:  Data is collected for each bus technology pair in each top speed and acceleration subcategory and a relative comparison is made using the unmodified diesel bus pair as the standard.  The best complete set of results between each bus technology pair determines the final result for each technology type.  Grades ranging from 0% to 21% are used to determine performance on flat ground, medium hills, and steep hills.  Muni's maximum grade of 21% is found on the Hyde Street cable car line.[37]  The second most extreme Muni line grade is found on the 1-California trolley coach line as it leaves Chinatown.[38]

4.2.   Definitions:

4.2.1.   Set is defined here as all of the top speed and acceleration results for a single vehicle.

4.2.2.   Subset is defined here as a singe category within the main categories of top speed and acceleration.  For example, a performance subset is 0-40 mph acceleration on a 0% grade.

4.2.3.   Full passenger load is defined here as not being able to accept additional passengers onto the bus.  This assumes that all passengers are behind the yellow passenger line in front, and are not standing directly in the rear door area.

4.3.   Test Procedure:

4.3.1.   Top Speed:  Top speed runs on 0% and 2% grades begin with rolling starts.  Both grade locations cover sufficient distance to allow the vehicle to reach terminal speeds.  Top speed runs for all but 0% and 2% grades begin with the vehicle's front bumper at the base of each hill.  Vehicle speed is zero (0) at the start of all but the 0% and 2% grade runs.  For 0% grade, starting speed is 55 mph.[39]  For the 2% grade, starting speed is 45 mph.[40]

4.3.2.   Acceleration:  Acceleration runs begin with both axles completely on the test grade; the measured angle of the vehicle's passenger isle is identical to the angle of the grade.

4.3.3.   Driver Commands:  The test driver is given simple, consistent verbal commands.  Upon hearing the command to accelerate, the driver will press the throttle pedal immediately to the floor.  Data recording will not start until the throttle pedal hits the floor.  The throttle remains fully depressed throughout each acceleration run.  Every effort is made to eliminate performance variation caused by different driving styles.

4.3.4.   Determination of Speed:  When the predetermined terminal test speed is attained, either the vehicle speed is taken (during top speed determination), or the stopwatch is stopped (for acceleration times).

4.3.5.   Determination of Subset Results:  Three (3) readings are taken for each performance data subset.  The two (2) best performance readings in that subset are then averaged to determine the final result for that particular subset.  For example, if the top speed readings for a particular subset are 59 mph, 60 mph, and 62 mph, then the final result for that subset will be 61 mph.  Two (2) significant figures are used to express the final result of all subsets, primarily due to measurement resolution.

4.4.   Site Conditions:

4.4.1.   Data is collected in dry weather conditions.  Extreme weather temperatures and wind are avoided during testing.

4.4.2.   There is no interference from traffic or other variables that could effect the consistency of the data collected for all test vehicles.

4.5.   Vehicle Conditions:

4.5.1.   Starting Vehicle Weight:  Each vehicle's fuel supply and other fluids are completely full at the beginning of each performance test set.

4.5.2.   Test Vehicle Weight:  In addition to the starting vehicle weight (4.5.1), each vehicle carries a simulated full passenger load of 85 passengers, not including the driver, during each test set.  It is assumed that each passenger weighs 150 pounds, and therefore the total passenger load for testing equals 85*150=12,750 pounds.

4.5.3.   Determination of Full Passenger Load:  Full passenger loads were determined by auditing 40-foot bus passenger loads during peak commute hours on the 71-Haight motor coach line.  It was determined that 85 passengers represented an average full passenger load.  Passenger loads as high as 97 people were found on a 40-foot bus operating the 71-Haight line.  However, for this analysis 90+ passenger loads do not fit the theoretical definition of a full passenger load (4.2.3).  In general terms, an 85-person passenger load on a 40-foot Muni motor coach represents a bus with a passenger in every seat, a standee for each seated passenger, plus another five (5) passengers.

4.5.4.   Justification for Exceeding Gross Vehicle Weight (GVW):  GVW is the manufacturers' recommended maximum total vehicle weight including passengers.  This weight is exceeded for all AFPP buses when they are loaded with 12,750 pounds for testing.  Vehicle weights in excess of GVW are common for Muni's 40-foot buses when in revenue service, especially during commute hours and special events.  Of AFPP test vehicles: the conventional diesel bus can carry 78 passenger before reaching GVW; the hybrid bus can carry 73 passengers before reaching GVW; the CNG bus can carry 58 passengers before reaching GVW.[41]  Rather than evaluate the AFPP buses using an unrealistic standard for San Francisco, it was determined that actual passenger loads be used (4.5.3).  In reality, if a bus has room for additional passengers, Muni patrons expect the bus operator to allow them to board.  In other words, the physical space inside of a bus is what actually dictates passenger loads when a bus is in service, not the weight that the bus is carrying.  Examples of passenger load conditions that potentially exceed even the 85 passengers per bus that defined AFPP test conditions: standard daily commute hours; special event and holiday operation;[42] and emergency/disaster evacuation.

4.5.5.   Simulating a Passenger Load:  Full passenger loads are simulated by filling the test bus with plastic water containers equal to the weight of 85 passengers (4.5.2).  Both the weight of the water and the container were taken into account when calculating the total simulated passenger load.  The simulated passenger load is equally spaced throughout the interior of the vehicle, including the seats, in an identical manner for each vehicle.  The containers are then secured so that they remain immobile throughout the test.

4.6.   Significant Variables: 4.6.1.   Parasitic Engine Forces:  Vehicle cooling fans are monitored during all test sets in order to establish that parasitic engine forces remained consistent.  In all cases, normal fan operation shall be "off."  Data point outliers have occurred, although not noticeably on the hybrids, if the engine-cooling fan engaged during a particular subset.  If fan activation occurs, the vehicle is allowed to cool to below thermostatically controlled temperatures by idling the vehicle.  Only data collected with the cooling fan off is used in the test analysis.  It should be noted that even when not activated, cooling fans can spin due to mechanical drag or other related forces.  This relatively slow spin is considered to be "fan off" in terms of the elimination of parasitic engine forces.

4.6.2.   Wind:  For all 0% grade evaluations, each of the three (3) data points represents an average of two (2) runs, with the second run being made in the opposite direction of the first.  This provision is made in an attempt to limit the effect of wind force on the test results.

4.7.   Data Collection Equipment:

4.7.1.   Stopwatch:  During acceleration testing, a digital stopwatch is used to determine acceleration times.  The same digital stopwatch is used for all vehicles.  Stopwatch resolution is +/- 0.01 seconds.

4.7.2.   Speedometer:  Analog Speedometer Readings:  Data collector is to make every effort to eliminate parallax for all test readings.  The speedometer reading was verified prior to any testing.  This verification was done by correlating the analog speedometer reading with the onboard digital telemetry reading.  The predetermined speed mark on the speedometer is defined as the center of that mark lined up to the center of the gauge dial indicator.  Combined probability of speedometer error = +/- 1%.

4.7.3.   Protractor:  Test grades were found using a calibrated digital protractor.  The device units are degrees, so a conversion factor was used to determine grade.  Protractor resolution is +/- 0.1 degrees, or +/- 0.175% grade.

4.8.   Test Personnel:  Personnel consistes of one (1) driver and one (1) data collector.  The data collector operates the timing equipment, witnesses the required vehicle speeds, and recorded test results.

OPERATION TIMES

Category leader:  Hybrid.

 

SUMMARY

This category evaluated the in-service average time between bus stops for each technology type.  Since there is a chassis mix between low-floor buses and high-floor buses, stop dwell times differ significantly.  Therefore, total trip time for each technology is based upon the high-floor control group's average dwell time.  Overall, the hybrid buses had the shortest average time between bus stops, and gain roughly 6% of total trip time when compared to the control group.

CNG buses had the slowest overall line times.  This is likely due to the extreme grades found in certain sections of the 19-Polk line, which hampers the performance of the CNG buses.[43]

Other lessons learned:  Low-floor buses, like the CNG and Hybrid buses in this test, were found to have much lower stop dwell times than high-floor buses.  In general, low-floor buses, regardless of the propulsion technology, can reduce trip times.

Next steps:  Data from additional routes is necessary in order to make a more accurate analysis of operational times.

RESULTS

TABLE 11

 

TABLE 12

EVALUATION CRITERIA

5. OPERATION TIMES

5.1.   Evaluation: Data is collected for each bus technology pair, with the exception of the unmodified diesel bus pair, and a relative comparison is made using the PM filer equipped diesel bus pair as the standard.  For purposes of this category, the PM filter and unmodified diesel bus pairs are considered together as the control group.

5.1.1.   Data Collection:  The alternative propulsion vehicles in the AFPP are low-floor buses, while the conventional diesel buses have high floor configurations.  Therefore, operational dwell times are not representative of the different propulsion technologies being evaluated.  Every effort is made to eliminate this unwanted variable by using the following evaluation compensations:

5.1.1.1.   Isolating Dwell Time:  In addition to total trip time, time between stop data is collected.  Therefore, the summation of times between stops, subtracted from the total trip time, equals the total dwell time.

5.1.1.2.   Corrected Total Trip Time:  The control group (high-floor) average dwell time for a particular run is multiplied by a particular test vehicle's number of stops, and added to the same test vehicle's total time between stops to arrive at a "high floor total trip time" for that test vehicle.

5.1.1.3.   Average Time Between Stops:  Average time between stops is considered directly comparable between technologies for any identical run, since there are roughly 200-300 stops per run to be averaged.  These times have nothing to do with the high or low floor configurations.

5.1.2.   Unique Conditions:  Any condition that proves unique to one vehicle during data collection of operation times is either removed from the data set or the particular run is thrown out.  An example of this would be a truck that completely blocks the road during one trip.  In this case, the data collector will note the estimated delay time to the second and subtract this from the recorded time for that segment and total trip.

5.1.3.   Passenger Counts:  Passenger loads are recorded for every designated stop the test bus makes.  These load counts will ensure that comparable passenger loads are used for operation time analysis.

5.2.   Site Conditions:

5.2.1.   Comparable Days:  Every effort is made to collect data on identical runs when the vehicle test conditions are most likely to be similar between vehicle types.  For example, Fridays or days when the there is a Farmer's Market on a particular test run are avoided due to unusually high vehicle and pedestrian traffic on those days.

5.2.2.   Line Compatibility:  Data cannot be collected on any line where the buses have difficulty navigating for any reason.  All AFPP vehicles have proven compatible with every line evaluated during the initial 6 months.

5.3.   Vehicle Conditions:

5.3.1.   Inspection:  A thorough inspection and evaluation is performed of the vehicle's systems prior to testing.  For example, the brakes must function properly.

5.3.2.   Operator Approval:  The operator must feel like the vehicle performs well for its technology type.

5.3.3.   Propulsion System:  There must not be any propulsion system maintenance codes present.  Fuel and all other fluids must be full.

5.4.   Data Collection Equipment:  A digital stopwatch is used to determine time between stops to one-tenth (0.10) of a second.  The stopwatch digital clock is used to determine total trip times to the second.

5.4.1.   The same digital stopwatch and digital clock is used for all vehicles.

5.4.2.   The stopwatch timer has resolution to one-hundredth (0.01)of a second.  Times are rounded to the nearest one-tenth (0.10) of a second.

5.5.   Test Personnel:  Personnel consist of one (1) driver, and two (2) data collectors.  The first data collector operates the timing equipment and records test results.  The second data collector records passenger count data at every designated stop the vehicle makes.

5.6.   Significant variables:  The same operator must drive for every technology type on a given run, in an attempt to reduce driver related variables.

FUEL ECONOMY

Category leader:  Conventional diesel.

Alternative leader:  Hybrid.

SUMMARY

Fuel economy for each technology was evaluated in terms of diesel gallons.  By converting CNG energy to its diesel equivalent, a direct comparison was possible between the different fuels evaluated in this report.

The conventional diesel buses are over 26% more fuel efficient than the hybrid buses.  The hybrid buses are 25% more fuel efficient than the CNG buses.  Overall, conventional diesel technology is over 58% more fuel efficient than the CNG buses.

The relatively low fuel economy result from the hybrids is somewhat surprising.  However, while numbers differ, the general on-road results pattern (conventional diesel leading, followed by hybrid followed by CNG) is consistent with that found during chassis dynamometer emissions testing.[44]  It should be noted that unlike their passenger car counterparts, which are well known for their superior fuel economy, hybrid transit buses are configured and optimized very differently than these passenger car hybrids.  Furthermore, data collection was interrupted during the hybrid and unmodified conventional diesel evaluations, which potentially compromised the long term fuel economy data for the hybrids.  Therefore, the hybrid data reported here represents only short-term fuel economy for the hybrid buses, and could change during the remaining course of the program.

Other lessons learned:  Due to Muni's early switch from ~120 ppm sulfur CARB-2 diesel fuel to ~15 ppm sulfur ULSD[45] fuel during the initial evaluation period, fuel economy reported here for diesel fueled buses with PM filters may not be optimized due to excess sulfur in the filter.  Once the PM filters have been properly serviced by the filter manufacturers, fuel economy for those buses is expected to increase.

Next steps:  Hybrid bus data should be recollected to better reflect long term fuel economy.  All PM filters should be factory serviced due to Muni's conversion to ULSD fuel, and data should be recollected on those vehicles.

RESULTS

TABLE 13

FUEL ECONOMY:

Vehicle: Fuel Mileage (miles per diesel gallon)[46]:
CNG 2.4
Hybrid 3.0[47]
Conventional Diesel with PM Filter 3.8

EVALUATION CRITERIA

6. FUEL ECONOMY

6.1.   Evaluation:  Data is collected for each bus technology pair, with the exception of the unmodified diesel bus pair, and a relative comparison is made using the PM filter equipped diesel bus pair as the standard.  Fuel records are kept for fuel added and odometer mileage at the time of each fueling.  Total mileage (mi) during measured segment divided by total fuel used during that segment (DGE) equals miles per diesel gallon (mi/DGE).

6.2.   Definitions:  Due to the dissimilar physical states of fuel being evaluated (gas and liquid), energy content is used to compare fuel economy.  Fuel economy results are represented in units of miles per diesel gallon equivalent (mi/DGE).

6.2.1.   DGE:  Diesel fuel energy content is measured in this study in units of diesel gallon equivalents (DGE).  One (1) DGE is defined as 139,000 BTU's.  Diesel fuel referenced here is ultra low sulfur diesel (ULSD).  ULSD is defined as having less than or equal to 15 parts per million (ppm) sulfur content.

6.2.2.   GGE:  Compressed natural gas (CNG) is measured in this study in units of gasoline gallon equivalents (GGE) and Therms.  One (1) GGE is defined here as 128,000 BTU's.  1.086 GGE = 1.000 DGE.  One (1) Therm = 100,000 BTU.  1.39 Therms = 1.00 DGE.

6.3.   Significant Variables:

6.3.1.   Hybrid Diesel-Electric Bus Correction Factor:  Every effort is made to treat the hybrid technology as "transparent" in terms of daily operation.  For example: The hybrids are simply started before going into service, allowed to idle while the operator makes seat/mirror adjustments and performs a pre-trip inspection, and they are then driven into service.  Likewise, at the end of a run, the buses will be fueled (if required) and parked.  Because of this transparent treatment, no provisions are made for battery state of charge (SOC) variations during normal operations.  In keeping with the theory of transparent operation, fuel economy numbers for the hybrid buses are "in-use" numbers, and not necessarily actual fuel economy.  In order to determine actual fuel economy for the hybrids, one would need to correct for battery state of charge.

6.3.2.   Loads and Operating Conditions:  Passenger loads and operating conditions varied during fuel economy data collection.  Load and operating variability can influence fuel economy data.

RANGE

Category leader:  Conventional diesel.

Alternative leader:  CNG.

 

SUMMARY

Range is the measure of how far a vehicle can travel per full fuel load.  Useful range is clearly less than this maximum range number, since running out of fuel is unacceptable when the bus is in-service.  The conventional diesel buses with PM filers can travel more than 20% farther than the CNG buses.  Hybrid range data collection was interrupted, so the range number reported here is estimated (based on 100 gallon fuel tank and 3.0 mpg fuel economy).  Based on this estimate, the CNG buses can likely travel up to 30% farther than the hybrid buses.[48]  Overall, the conventional diesel buses with PM filers can travel 22% farther than the CNG buses.

Other lessons learned:  The CNG range data is based on the fuel system pressure dropping to minimum recommended operating levels.  It should be noted that the CNG buses could continue on after this point.[49]  The hybrid range data is estimated based upon fuel economy data.  Furthermore, true hybrid range data must be calculated once actual range data is corrected with battery state of charge data.

Next steps:  Hybrid range data should be recollected.

RESULTS

TABLE 14

VEHICLE RANGE:

Vehicle: Range (miles):
CNG 392
Hybrid 300[50]
Conventional Diesel with PM Filter 480

EVALUATION CRITERIA

7. RANGE

7.1.   Evaluation:  Data is collected for each bus technology pair, with the exception of the unmodified diesel bus pair, and a relative comparison is made using the PM filter equipped diesel bus pair as the standard.  Records are kept for odometer mileage at the time of full fueling.  The vehicle then operates at all times either in revenue service or otherwise on surface streets in San Francisco.  Freeway miles accumulated during range evaluation are avoided or are kept to a minimum.  Total mileage (mi) accumulated at the time of fuel starvation equals vehicle range.  Note that the usable range should generally be considered 25 miles less than the actual range.

7.2.   Definitions: 

7.2.1.   Vehicle Range:  Range is defined here as the distance (mi) traveled per full vehicle fuel load at the time the vehicle runs out of fuel.

7.2.2.   Out of Fuel:  Running out of fuel, is further defined as the vehicle's engine running out of fuel; fuel starvation.  Fuel starvation occurs when it is confirmed the engine cannot draw any fuel from the vehicle's gas supply.  This definition is needed for the following reasons:

7.2.2.1.   For CNG, full fueling is defined as 3600 psi on the fueling station pump gauge.

7.2.2.2.   Muni's CNG buses are considered out of fuel in this evaluation if the vehicle's supply fuel pressure reaches 200 psi.  At this point a driver warning alarm is sounded due to the possibility of fuel starvation caused by low primary fuel supply pressure.44

7.2.2.3.   The diesel fuel systems in this evaluation may not be able to draw the entire fuel supply; after the point of fuel starvation there may still be residual fuel in the fuel tank.  This lowers the useable volume of the fuel tank to below specified tank capacity, and differentiates actual range from theoretical range.

7.3.   Significant Variables:  Passenger loads and operating conditions may vary during range evaluation.  Load and operating variation can have an influence on range data.

OPERATIONS

  Operator Feedback

  Passenger Feedback

OPERATOR FEEDBACK

Category leader:  Conventional diesel.

Alternative leader:  Hybrid.

 

SUMMARY

All operators of the test buses were asked to fill out driver surveys following each run (a run is a set of round trips on a specified line).  Seven (7) operators responded, representing roughly 17% of AFPP trained operators.[51]  The majority of operators that responded prefer the conventional diesel buses that they are familiar with.  Of note was that none of the operators responded as preferring the hybrid buses, however, the majority of operators feel that the hybrid buses perform roughly the same or better than conventional diesel buses.  Hill climbing performance and acceleration from a stop were emphasized as the shortcomings of the CNG buses.  Noise level and braking effort were preferred on both the CNG and hybrid buses, and the overall smoothness of the hybrid buses when accelerating and stopping impressed the operators.[52] 

Other lessons learned:  Greater run variety is needed in order to obtain more feedback.  Of the standard motor coach fleet, operators prefer the 1999 NABI diesels.

Next steps:  The buses should be evaluated by a larger number of operators, from a larger number of different lines. 

RESULTS

TABLE 15

DRIVING CHARACTERISTICS - COMPARED TO CONVENTIONAL DIESEL BUSES:

Comparable Feature: Majority Response for CNG Majority Response for Hybrid
Engine Power Same Same
Initial Acceleration No Majority Same
Performance on Hills Not As Good Same
Performance in City Traffic No Majority Same
On Time Performance No Majority Same
Maneuverability No Majority No Majority
Smooth Propulsion System No Majority Better
Braking/stopping Better Better
Noise Better Better
Safety Same Same
Reliability Same Same
Passenger Acceptance Same Same

The following questions and answers are taken from the CNG section of the written surveys.  All responses are listed:

Q - Any problems related to CNG engine?

A - No CNG specific problems were reported by operators.

Q - Should Muni buy CNG buses?

A - "No."

A - "Not to be recommended."

A - "No."

A - "Not if hybrids available."

General CNG comments from written surveys:[53]

" will not pull hills." 

"Bus are very low, slow on the take off, bouncing " 

"Please note for the record that this equipment is wholly inadequate.  It is too slow and underpowered for the express line that I had to work today."

"It's a good bus for tour traps.  But not for city lines."  "Unsatisfactory" 

"My assessment is it is a excellent coach.  But not for San Francisco bus lines.  We have lots of hills, which hampers this coach.  Slow acceleration on hills and in traffic." 

"New equipment always seems better because it is new." 

"I don't feel the CNG bus would be good for Muni.  It was very slow, underpowered and heavy to steer.  It might be good for commuter freeway lines but it would add 25% to our running times." 

"Fair." 

"When I drove the bus it had 5,000 miles and felt like it had 200,000 miles.  I noticed that it was losing speed and power from when I tested it and the bus only had 1,000 miles."

The following questions and answers are taken from the hybrid section of the written surveys.  All responses are listed:

Q - Any problems related to the hybrid propulsion system?

A - The only hybrid propulsion system problem that was reported was that the interior noise was unacceptably high.[54]

Q - Should Muni buy hybrid buses?

A - "Not on hills."

A - "No."

A - "Buy some."

A - "Yes."

A - "Yes."

A - "If the (interior) noise can be minimized then maybe yes."

General hybrid comments from written survey:44

"Coach is not for SF operation." 

"Should perform on some lines without grade." 

"The public is very intrigued by a non-polluting electric bus that doesn't need to be on wires." 

"At this stage, it's too early to give comment."

EVALUATION CRITERIA

8. OPERATOR FEEDBACK

8.1.   Evaluation:  Data is collected for each bus alternative technology pair and a relative comparison is made using the Muni's conventional diesel bus fleet as the standard.  Operator feedback is primarily collected using evaluation surveys.  Operators of the test buses are asked to complete the surveys at the completion of each service run in a test bus.  The second form of operator feedback is in written form, such as a letter or email.

8.2.   Significant Variables:  While all operators of test buses are asked to provide feedback, individual time spent driving the test buses differs significantly.  This is generally due to the training schedules, the availability of the test buses, operator schedules, and the different runs that the buses are assigned to for different phases of the testing program.

PASSENGER FEEDBACK

Category leader:  Inconclusive, due to limited data collection.

 

SUMMARY

In order to gauge passenger opinions regarding the alternative technologies in this program, a preliminary seven (7) question survey was designed.  The survey has been tested briefly in the field.  Based on a very limited sample of 18 surveys and follow up discussions, some potential trends have already been noticed.[55]

1) Riders are generally concerned with all kinds of emissions but don't view Muni as a major source of urban emissions.

2) Most riders feel that a different fuel source probably means a cleaner burning bus; and they can tell that these buses look different than the rest of the fleet.

3) Riders want dependable service first and foremost, but would prefer to ride cleaner buses whenever possible.

Other lessons learned:  These in-field survey tests have revealed that some questions may need to be refined if we are going to measure any significant preference for alternative technology buses compared to conventional diesel buses.

Next steps:  Refine the survey and continue to administer throughout the 24-month AFPP.

RESULTS

Results to date are inconclusive due to limited data.

During the ongoing testing the intent is to survey Muni's ridership in an effort to measure rider opinions in a three main areas:

1) Are Muni riders concerned with emissions from Muni buses and do they view Muni as a significant source of urban emissions?

2) Do Muni riders understand the technical difference between alternative technology buses and diesel buses; can they detect a difference (look, feel, smell)?

3) Do Muni riders have a significant preference for alternative technology buses compared to diesel buses.

EVALUATION CRITERIA

9. PASSENGER FEEDBACK

9.1.   Evaluation:  Data is collected for each bus alternative technology and a relative comparison is made using the Muni's conventional diesel bus fleet as the standard.  Passenger feedback is primarily collected using evaluation surveys.

9.2.   Test Procedure:  The surveys are verbally given to passengers while the test bus is in revenue service.  The goal is to eventually administer the surveys to a large number of passengers in order to better represent public opinion.

9.3.   Significant Variables:

9.3.1.   Language:  The survey is given in English only, which may prevent many Muni riders from providing feedback.

9.3.2.   Runs:  The survey is given on a specific runs only; the survey is only given in certain parts of the city at certain times of the day.

9.4.   Test Personnel:  Test personnel who are clearly identified as Muni employees administer the surveys.

 

 

 

MAINTENANCE

  Reliability

  20-Hour Performance

  Maintenance Feedback

RELIABILITY

Category leader:  Conventional diesel.

Alternative leader:  CNG.

SUMMARY

The average number of miles that a vehicle travels between failures is the measure of reliability that is used in this analysis.  The clear reliability advantage goes to conventional diesel technology.  CNG and hybrid technologies have proven significantly unreliable in service when compared to the control group.  Results are broken down into propulsion system and chassis categories.  

While conventional diesel technology appears over four (4) times more reliable than CNG technology, and over ten (10) times more reliable than hybrid technology, it should be noted that these alternative technologies are new to Muni, and these results were anticipated during the initial 6-month period.  However, Muni's reliability rates for these new technologies are very close to New York City Transit's (NYCT) reported reliability rates for these technology types during their first six (6) months in service.[56]  Regardless, poor reliability rates directly translate to poor service, it also correlates to low test mileage accumulation, which compounds analysis difficulties.  The PM filters required cleaning one (1) time during the initial 6 months of testing.  Reliability rates for the PM filters will be unknown until additional data has been collected.

Other lessons learned:  Six (6) months is not enough time to build up sufficient vehicle mileage on the alternative technology buses to perform an accurate analysis of reliability.  While this report is primarily concerned with the evaluation of alternative fuels and propulsion technologies, it should be noted that the additional weight added by CNG fuel tanks and hybrid battery loads reduces the number of passengers that a bus can hold before reaching its maximum allowable gross vehicle weight (GVW).  Of AFPP test vehicles: the conventional diesel bus can carry 78 passenger before reaching GVW; the hybrid bus can carry 73 passengers before reaching GVW; the CNG bus can carry 58 passengers before reaching GVW.[57]  Additional vehicle weight can also increase brake wear rates, however, hybrid brake wear rates seem to be better due to hybrid system's supplemental regenerative (electric) braking.

Next steps:  It is crucial to the analysis of reliability rates that the vehicles build up additional mileage.  Engine oil samples should be analyzed in order to help predict long-term engine wear patterns.

RESULTS

TABLE 16

RELIABILITY RATES DURING INITIAL 6-MONTHS:

Evaluation: CNG Hybrid Conventional Diesel
Propulsion System MDBF (mi)
1549
541
4872
Chassis MDBF (mi)
581
1470
716
Total MDBF (mi)
443
429
696
Total Combined In-Service 6-Month Mileage
9294
10288
24360

EVALUATION CRITERIA

10. RELIABILITY

10.1.   Evaluation:  Data is collected for each bus technology pair and a relative comparison is made using the conventional diesel bus group as the standard.  All records for the first six (6) months in service are evaluated for each technology pair in order to determine the total reliability of each technology.[58]  PM filters were installed on test buses following their initial six (6) months in service, so the 6-month reliability of the PM filters alone will be evaluated separately.  This study is primarily concerned with the evaluation of different propulsion systems and configurations, so chassis reliability rates are evaluated separately.  A relatively high mileage number result is this study's measure of relatively superior reliability.  In other words, a more reliable vehicle can accumulate relatively more miles between in-service failures.

10.2.   Definitions:

10.2.1.   Reliability:  Mean Distance Between Failure (MDBF) is the measure of reliability used in this study.  Reliability for this study is further defined by two (2) categories:  Propulsion system failures and chassis failures. 

10.2.2.   Propulsion system is defined to include engine, transmission, system generator, traction motor, rear axle, fuel system, batteries, cooling system, and all accessories associated with the normal operation of one of these systems. 

10.2.3.   Chassis failures encompass all non-propulsion system areas of the vehicle, including but not limited to:  Doors, suspension, foundation brakes, windows, tires, and lighting.

10.2.4.   Failure:  Chassis or propulsion system failure is defined as any event or problem that produces a road call or will not allow a vehicle to go into service.

10.3.   Test Procedure:

10.3.1.   Repair Records:  All unscheduled vehicle repairs are recorded.  Vehicle mileage at the time of an unscheduled repair is used to determine MDBF.

10.3.2.   Road Calls:  All road calls are noted in the repair records, and are differentiated from failures that prevent a vehicle from going into service.

10.3.3.   Out of Fuel:  Propulsion system failure includes fuel starvation if there remains sufficient fuel to supply the engine.  However, this is not to be confused with an out of fuel condition, where there is no more fuel available for the engine.  Although an out of fuel condition requires a road call, the event is not included in this evaluation of reliability.  This is due to the fact that each vehicle in this study has sufficient fuel capacity to operate for more than 24 hours in revenue service without refueling.

10.4.   Significant Variables:  There are many factors that contribute to a vehicle's reliability.  Examples of the variables involved include, but are not limited to:  Driving technique; maintenance; passenger loads; grade conditions; weather conditions; and road conditions.  In general, the level of equal distribution of these variables between the test buses is proportional to combined vehicle mileage, assuming all test buses accumulate roughly equal mileage.

20-HOUR PERFORMANCE

Category leader:  Inconclusive, due to non-ideal test conditions.

SUMMARY

This category considers the reliability of the buses as they operate continuously for 20 hours in peak ambient temperature conditions.  Data was not available for this initial 6-month report, primarily due to the relatively mild winter temperatures in San Francisco during this time.

Other lessons learned:  All test buses proved reliable when operated continuously in relatively mild ambient temperature conditions.

Next steps:  Be prepared to collect 20-hour performance data when conditions are ideal for testing.

EVALUATION CRITERIA

11. 20-HOUR PERFORMANCE

11.1.   Evaluation:  Data is collected for each bus technology pair and a relative comparison is made using the unmodified diesel bus pair as the standard.  This is a pass or fail category in the AFPP.  The evaluation consists of operating all test vehicles on a characteristic route, while run continuously in peak ambient temperatures for 20 hours.  At the end of 20 hours in operation, the vehicle must pass the following criteria:

11.1.1.   Operator Evaluation:  The operator must feel like the vehicle performs roughly the same at the beginning and end of the 20-hour performance run.

11.1.2.   Diagnostic Codes:  Propulsion system maintenance codes cannot be present when the vehicle is inspected following the 20-hour performance run.  If there is a code, it could signify a problem with the engine or propulsion equipment.

11.1.3.   Maintenance Inspection:  The vehicle propulsion system must not display any fluid leaks, air leaks, noises, signs of overheating, looseness in mountings or attachments, or other form of wear or problem when the vehicle is inspected following the 20-hour performance run.

11.2.   Test Procedure:

11.2.1.   Operation:  The test will assume normal vehicle operations.

11.2.2.   Terminal Breaks:  The vehicle is only turned off during the operator's terminal breaks.

11.3.   Site Conditions: This test is performed during dry and peak ambient temperatures conditions.

11.4.   Vehicle Conditions:  A thorough inspection and evaluation is performed of the vehicle's propulsion system prior to testing.

11.4.1.   Operator Acceptance:  The operator must feel like the vehicle performs well for its technology type before 20-hour testing begins.

11.4.2.   Diagnostic Codes:  Propulsion system maintenance codes cannot be present when the vehicle is inspected prior to the 20-hour performance run.

11.4.3.   Maintenance Inspection:  The vehicle propulsion system must not display any fluid leaks, air leaks, noises, signs of overheating, looseness in mountings or attachments, or other form of wear or problem when the vehicle is inspected prior to the 20-hour performance run.

11.4.4.   Fluids:  Fuel and all other fluids must be full or at proper levels.

11.5.   Significant Variables:  Passenger loads and operating conditions vary during 20-hour performance data collection.  Load and operating variability can influence reliability data.

11.6.   Data Collection Equipment:  Standard vehicle maintenance and diagnostic equipment is used to diagnose and inspect the vehicle.

MAINTENANCE FEEDBACK

Category leader:  All.

SUMMARY

Three mechanics, with 39 years combined experience with Muni function as the primary maintenance team for the test vehicles.  They were surveyed for their opinions regarding the maintenance of the different technologies represented in the program.  The mechanics all agreed that overall build quality and maintenance practices determine reliability rates.  While acknowledging that the alternative technologies are not yet reliable at the 6-month point in the program, all were in agreement that the technologies would become generally more reliable as they accumulated additional miles.  Each mechanic felt that the most important element in successful maintenance of the alternative vehicles was to have proper training, tools, and maintenance areas provided prior to receiving a new procurement of buses.  Maintenance division supervisors, and Local 1414 have also placed a strong emphasis on this point.[59]

Other lessons learned:  Reliability comments come from mechanics that have volunteered for the AFPP.  Their optimistic comments do not necessarily represent the opinions of other Muni mechanics that were not interested in applying for the AFPP positions

RESULTS

TABLE 17

MAINTENANCE SURVEY - RELATIVE RELIABILITY RATES:

Technology Reliability:  1 = Most 5= Least
Conventional diesel 1.7
Conventional diesel w/ PM filter 2
CNG 2.5
Hybrid 3

The following comments are taken from written surveys:

Reliability:

Daily reliability:

Each of the three (3) AFPP mechanics stated that reliability is directly related to the build quality of the entire vehicle.  One comment was that if all motor coaches are maintained identically by Muni, they should therefore be equally reliable in daily service.  Another comment was that the CNG engine and fuel system may not be as reliable on a daily basis as conventional technology.

Long-term reliability:

The AFPP mechanics were split regarding which technology would be most reliable in the long-term.  One stated that conventional diesel technology will have the same reliability as past motor coach fleets.  Two stated that hybrid technology will have the same reliability as past motor coach fleets.  In response to the hybrid bus reliability problems during the initial 6-months, it was thought that hybrid buses will become more reliable as this new technology is developed.

Relative reliability:

AFPP mechanics stated that the CNG buses are generally more reliable than the hybrid buses, but neither CNG or hybrid technology has proven reliable to date.  Furthermore: "We do not have the proper tools, place and safety precautions in place to work on CNG coaches, until that has been done, I believe hybrids are more realistic.  I would also believe fuel cells to be the future of transit."

Safety comments:

CNG:

If appropriate training is provided, Muni mechanics will have every reason to feel comfortable and safe working on CNG buses.  Two (2) AFPP mechanics stated that, in reality, CNG buses may not receive the same level of maintenance attention as conventional diesel buses due to safety concerns - even if appropriate training is provided.

Hybrid:

Each of the three (3) AFPP mechanics stated that if appropriate training is provided, Muni mechanics will have every reason to feel comfortable and safe working on hybrid buses.

Technology specific comments:

CNG:

Two (2) AFPP mechanics stated that whether the buses are different or not makes no difference as long as appropriate training, tools, and infrastructure are provided.

Hybrid:

Two (2) AFPP mechanics stated that Muni should use hybrids to transition its motor coach fleet to be on par with Muni's trolley bus and light rail vehicle (LRV) fleets by using the most modern forms of electric bus propulsion technology currently available.

EVALUATION CRITERIA

12. MAINTENANCE FEEDBACK

12.1.   Evaluation:  Data is collected for each bus technology pair and a relative comparison is made using Muni's conventional diesel fleet as the standard.  Maintenance feedback is primarily collected using evaluation surveys.  Maintainers of the test buses are asked to complete the surveys at six (6) month intervals throughout the program.  The second form of maintenance feedback is in written form, such as a letter or email.

12.2.   Significant Variables:  From two (2) to three (3) maintainers are assigned to the test buses at any one time.  Therefore, feedback from maintenance supervisors familiar with the test buses is encouraged in order to increase the number of responses.

COST

  Operating cost

  Capital cost

OPERATING COST

Category leader:  Conventional diesel.

Alternative leader:  Hybrid.

 

SUMMARY

Operational cost was split into three (3) subcategories:  Fuel cost per mile, maintenance cost per mile (which includes repair and routine maintenance costs), and total vehicle cost per mile.  Based on fuel alone, the conventional diesels appear to be over 22% less expensive to operate when compared to the estimated fuel cost per mile for the hybrid buses, and 40% less expensive to operate when compared to the CNG bus fuel cost per mile.  Fuel prices are based on the cost that Muni pays for diesel fuel[60] and what Sacramento RT pays for CNG.

Maintenance cost results here are not representative of life-cycle costs due to the fact that the alternative buses are a new experience for Muni, and the conventional diesel buses represented here are not entirely different than all of Muni's past diesel buses.  In addition, 6 months is not sufficient time to accurately predict life-cycle maintenance costs, and these results are inconclusive.  In general, the conventional diesel buses were the least expensive per mile to maintain, followed by the hybrid buses, and finally the CNG buses.

While no long-term projections have been calculated due to the limited data available after 6 months of testing, it should be noted that the cost to replace hybrid propulsion system batteries, roughly every two (2) years, is about $10,000 per bus, or $60,000 over the 12-year life expectancy of each hybrid bus.[61]

Other lessons learned:  Fuel prices are constantly changing, and it is therefore difficult to predict long term fuel pricing.  Maintenance data is greatly influenced by the fact that these alternative technologies are new to Muni, and require additional time to establish the repair patterns found with the conventional diesel buses.

Next steps:  Fuel economy data should be recollected for all test vehicles, and fuel cost per mile should be recalculated based on these revised fuel efficiency numbers.  Additional miles are needed on the alternative buses in order to make a meaningful analysis of maintenance costs and life cycle cost estimates.

 

RESULTS

TABLE 18

FUEL COST PER MILE:

Vehicle: Fuel Price: (DGE)[62] MPG:[63] Fuel Cost per Mile:
CNG $0.95 2.4 $0.40
Hybrid $0.92 3.0[64] $0.31
Conventional diesel with PM Filter $0.92 3.8 $0.24

TABEL 19

MAINTENANCE COST PER MILE:

Vehicle: Propulsion System Maintenance Cost per Mile: Chassis Maintenance Cost per Mile: Maintenance Cost per Mile:
CNG
$0.59
$0.66
$1.25
Hybrid
$0.28
$0.42
$0.69
Conventional diesel with PM Filter
$0.08
$0.50
$0.58

TABLE 20

TOTAL COST PER MILE:

Vehicle: Total Propulsion System Cost Per Mile: Total Cost Per Mile (Fuel + Maintenance):
CNG
$0.99
$1.65
Hybrid
$0.59
$1.00
Conventional diesel with Particulate Filter
$0.32
$0.82

Other operating costs, not included in the primary cost analysis or tables, concerns the effect of vehicle performance differences while in-service, and the cost of special operation and maintenance training.

Limited data concerning the San Francisco operational performance differences between the various bus technologies forced cost calculations based on the annual operational costs for a narrow range of bus performance factors (10% slower, 5% slower, and 6% faster).  The basic analysis sought to quantify how these seemingly minor increases or decreases in bus performance could affect operating costs over the course of a year.  This analysis defined two sets of line assignments: for a fleet of 80 buses on the road at one time; and for a fleet of 60 on the road at one time.  These line selections were based on directives within the 11 Point Agreement.[65]  One set of routes was determined by environmental justice demographic considerations, and one set was defined by topographic considerations, whereby relatively flat or mild grade routes were selected to better accommodate alternative fuel buses.  Both line assignments demonstrated that a single percentage point in bus performance can cost over $200,000 annually.

One might reasonably expect that a five percent (5%) loss or gain in coach operating performance would not be a significant factor when comparing bus technologies, and that slower buses and the resulting service impacts could be absorbed into the existing schedules.  However, Muni's service is presently very tight and there are very few "slack" periods where slower running times could be absorbed into the current system without reducing service capacity, daily frequencies, peak-hour-headways and hours of service.  Individually a six percent increase in performance or a five percent decrease in performance and running times does not seem significant.  However the detailed analysis estimates the potential, cumulative cost of an 11% difference between the bus technologies.  The analysis indicates that (assuming service capacity and operation costs remain constant) the cumulative annual cost of adopting a bus that is 5% slower and concurrently rejecting a bus that is 6% faster translates into between two (2) and three (3) million dollars annually.

In order to arrive at a baseline cost figure, the annual revenue hours for each motor coach line were determined and multiplied by $91.26 (the motor coach variable cost per hour stated in National Transportation Database).  This figure is the Federal Transit Administration's (FTA's) official measure of bus costs.  It includes most operational and maintenance costs, but excludes administration and overhead (A&O) costs, and it does not differentiate between a standard (40') and articulated (60') coaches. In order to account for a slower buses, with decreased performance measures, the baseline annual revenue hours figure for each motor coach line must be factored upwards by the performance difference. Conversely, in order to account for faster buses with increased performance measures, each motor coach's annual revenue hours figures must be factored downward by the performance difference.  The revised costs were then determined by multiplying the revised hours of service figures with the $91.26 hourly cost.

It is assumed that once better data is collected concerning the performance differences observed while in Muni service, these factors can then be plugged back into this analysis, or the information could be given to Muni scheduling, so that real schedules based on observed run times could be generated.

EVALUATION CRITERIA

13. OPERATING COST

13.1.   Evaluation:  Data is collected for each bus technology pair and a relative comparison is made using the unmodified diesel bus pair as the standard.  Operating cost is evaluated in terms of the cost per mile for each technology pair.  The total cost for each technology pair is divided by the total number of miles for each pair.  Operating cost for test vehicles include, but are not limited to, costs associated with:  fuel used; maintenance labor; maintenance parts; all non-fuel system fluids; body repair labor; and body repair parts.  All records for the first six (6) months in service are evaluated for each technology pair in order to determine the total cost for each technology.  All warranty work is included, even if this cost is not directly paid by Muni.  This study is primarily concerned with the evaluation of different propulsion systems and configurations, so chassis related costs are evaluated separately.

13.2.   Significant Variables:  There are many factors that contribute to operating costs.  Examples of the variables involved include:  Driving technique; maintenance; operating conditions; fuel pricing; market changes; and vehicle age.

CAPITAL COST

Category leader:  Conventional diesel.

Alternative leader:  Hybrid.

SUMMARY

This category considers the incremental cost involved with purchasing alternative technologies as well as the necessary infrastructure costs related to supporting these alternative technologies.  In general, the hybrid buses are 17-52% more expensive to purchase than conventional diesels, but they incur significantly less incremental facility costs at $1.05 million.  The CNG buses are only 14-18% more expensive to procure, but the incremental facility costs are estimated to be approx. $7 million for one facility and $12 million for two facilities.[66]

Other lessons learned:  The majority of CNG fueling infrastructure cannot be converted in order to support future hydrogen fueling needs, such as those now thought to be required for hydrogen fuel cell powered electric buses.[67]  Diesel PM filter ash/waste will have to be managed for Muni's entire diesel fleet.[68]

Next steps:  Further research should be done in order to refine these cost estimates.

RESULTS

The incremental cost of purchasing alternative technology vehicles is due to several factors, including low production volumes, and additional propulsion related equipment and subsystem costs.

TABLE 21

NEW BUS COST SUMMARY59

Vehicle Type (all standard 40') or Technology: Procurement Size: Cost (each):
CNG Any $375k - $390k
Hybrid 15 $450k - $500k
Hybrid 80+ $385k - $425k
Diesel w/PM Filter Any $330k
PM Filter[69] Any $10k

The incremental facility cost is due to the fact that Muni diesel facilities require modifications in order to safely accommodate CNG vehicles.[70]  These modifications were required prior to large-scale implementation of alternative fuel buses at Muni.  Many capital costs, such as those related to facility redundancy, are relativ to the number of vehicles procured.

Because of such high risks that are typically associated with handling natural gas equipment, the natural gas industry has been maintaining one of the highest quality and safety assurance standards/precautions for equipment and infrastructure.  Implementing these safety precautions in natural gas infrastructure have reduced the probability of accidents and the impact of such accidents at various transit agencies over the last couple decades.

What follows is a detailed comparison and evaluation of CNG and hybrid maintenance facility requirements and costs.

 

TABLE 22

INFRASTRUCTURE REQUIREMENTS COMPARISON:

Requirement CNG Technology: Hybrid Technology:
Fueling Time Per CNG bus, fueling takes 4-5 minutes at a dedicated facility.  First coach may fuel faster, 3-4 min, with the last coach in line taking longer, 5-6 minutes. Otherwise it takes 45 minutes to 1 hour per bus at a retail facility, + the time to drive coaches there & back; this is feasible only for a 15-coach procurement, and then only as a redundancy to a Muni-owned fueling facility. Hybrid fueling takes 2.5-3.5 minutes to fill the 100-gal tank, at the uniform rate for pumping diesel.  It takes 4-5 minutes to fuel larger tanks on conventional 40-ft diesel coaches: 150 gal NABI tank, and 140 Neoplan tank.  However, since the MC fuel tanks will usually all be "topped off" rather than filled from empty, time gained from smaller tank size is not a factor during normal operation. 
Fueling Facility CNG fueling facility is orders of magnitude more complex than diesel, requiring more maintenance attention and affecting overall reliability.  Life cycle of buffer tanks may require replacement at some TBD interval.  However, ASME div 1 storage vessels should not need to be replaced. Less complex and smaller footprint fueling facility.  Diesel tanks require replacement only when they are known to be leaking.  Old tanks at Woods lasted 25 years; new tanks are expected to last longer.
Vehicle Roof Access CNG tanks are typically on roof of coach.  Tanks are rated to about 5,000 psi, but are generally filled to 3,600 psi.  There is no venting on a CNG bus.  Some roof access and an overhead crane is required to service the tanks for at least one maintenance bay. 46 lead-acid batteries in 2 units are on roof of hybrid.  Batteries are all replaced, roughly every 2 years.  An overhead crane will be required for at least one maintenance bay.  Other alternative may be ultra-capacitors, a solid unit that does not need to be replaced as often.
Clearances and Weight Facility must allow head room for coach lift; CNG is generally taller than conventional diesel coach, or a hybrid coach.  CNG coach (fueled) is up to 10% heavier than either hybrid or conventional diesel. Facility must allow head room for coach lift.  Hybrid coach (fueled) is up to 9% heavier than conventional diesel.
Non-Fuel Fluids CNG requires a separate type of oil, and therefore requires separate oil lubrication lines, and bulk oil storage tanks with associated leak detection system. Hybrid oil is the same as conventional diesel.
Gas Venting and

Toxic Waste Disposal

Gas recovery facility required, for work on CNG tanks.  Conceivably, all coaches could be de-fueled before maintenance activities to preclude building a CNG facility; but routine venting to atmosphere could be considered a neighborhood nuisance and an potentially unsafe regular practice; recapturing gas at a gas recovery station would be preferable, but would require a separate facility & storage tanks, and add time to the maintenance cycle.  A de-fueling station generally consists of pump and storage tanks or the CNG can be pumped back into the PG&E pipeline. Toxic waste (lead & acid) management, recycling and tracking is a concern.  A hazardous waste stream would be generated.  A recycling arrangement could be reached with the battery manufacturer. 
Fumes CNG safety may be a concern to existing and future facilities neighbors, and environmental issues must be addressed before Muni can secure federal funds for this project; gas venting is a consideration at the Sacramento facility, with adjacent land uses; also a concern in San Bernardino, adjacent to a school.  Compressor noise must be attenuated for workplace sound control, and vibration mitigation is also required. Battery storage, and battery charging:  There are controls and ventilation required for lead-acid fumes.  Ultra-capacitors (instead of batteries) would eliminate these concerns.  Expanded electronics and/or battery shop would be required.
Training More building maintenance staff required, and a continuous training program.  Or, the fueling facility could be maintained by a 3rd party. Standard facility maintenance skills would be required.
Security Greater vulnerability to terrorist threat; therefore, greater security required.[71] No additional level of security required.
Earthquake In the event of a natural disaster, the PG&E gas line might be compromised, interrupting Muni's ability to fuel CNG coaches. Only diesel coaches would be available for emergency response, unless CNG storage were built. Diesel fueled hybrid buses can operate in the event of a disaster scenario.
Table Summary Maintenance facility must be constructed in order to maintain fueled CNG coaches.  Alternatively, CNG coaches could be de-fueled & pushed into maintenance bays before undergoing any maintenance activities.  This would be an onerous operational alternative for more than a few coaches. Maintenance facility could be deferred, if maintenance activities could be shifted to 1099 Marin St, or another conventional facility.

TABLE 23

INCREMENTAL FACILITY COST COMPARISON - BASED ON THE COST ASSOCIATED WITH BUILDING AND CONVERTING CONVENTIONAL DIESEL FACITLITIES:

Item CNG Technology: Hybrid Technology:
Fuel & Maintenance Modifications (3 fuel lanes + 16 maintenance bays) $5.5M $0.8M
PG&E Hookup (TBD)[72] 0.0
De-Fueling Station (1 coach at a time) $0.3M 0.0
Safety Certification $0.5M $0.1M
Employee Training (stationary engineers or a new class) $0.5M $0.1M
Battery Conditioner 0.0 $0.05M
Service Vehicles $0.1M 0.0
SUBTOTAL:

Incremental Capital Cost for Islais Creek Facility

$6.9M $1.05M
Redundant Fuel Station at Woods division[73] $5.0M 0.0
Natural Gas Storage Tank TBD[74] 0.0
TOTAL:

Incremental Capital Cost for Both Islais Creek and Woods Facilities

$11.9M $1.05M

 

TABLE 24

THIRD-PARTY TURNKEY FUELING INFRASTRUCTURE RESPONSES TO Muni'S INQUIRY[75]

Name of Firm: Approx Facility Cost: Fuel Cost per Diesel Gallon Equivalent (DGE): Time to Construct: Comment:
ENRG $750K - $1.25M No cost provided; project cost amortized over a 10-year fueling agreement. 6-9 months

(independent of the larger facility project) +

6-9 month Muni review, safety certification and approval cycle = 12-18 months total

750-1000 DGE/hr delivery = 5-6 min fill time per bus;

minimum 30-80 bus fleet for ENRG to participate

Trillium USA $4.5M $0.33 - $0.68 per DGE for operation and maintenance + amortized purchase cost and profit;

appears not to include electric power, at $0.05-$0.13/DGE; $0.56/DGE gas[76]

Commodity cost:  $0.61-$0.69/DGE[77]

7 months (assuming no Muni special requirements, soil conditions or unforeseen conditions) + 6-9 month Muni review, safety cert & approval cycle = 13-16 months total 80-bus fleet,

5 minute fill time per bus,

3 lanes

Pinnacle CNG Co. $2M $0.44-$0.85 per DGE to operate and maintain the facility, + amortized purchase cost and profit; depends on volume pumped and other factors

($375,804-$725,985 annual cost); price does NOT include gas69 or electric power

6-12 months (assuming no special site coordination difficulties) + 6-9 month Muni review, safety cert & approval cycle =

12-21 months total

80-bus fleet; assumes 5 minute fill time per bus;

number of fuel lanes not indicated.

Trillium USA $1.5M N/A   15-bus fleet; assumes slower timed fill rate for night servicing.
Pinnacle CNG Co. $500K N/A   15-bus fleet; assumes 45min fill time per bus
PG&E Clean Air Transportation N/A N/A N/A Do not build turnkey facilities
Bevilacqua Knight, Inc. N/A N/A 7-14 months + 6-9 mo Muni cycle = 13-23 mo total Do not build turnkey facilities

 

EVALUATION CRITERIA

14. CAPITAL COST

14.1.   Evaluation:  Capital cost is primarily concerned with two (2) categories:  Incremental vehicle cost; and incremental support facility cost.  Vehicle vendors shall be surveyed regarding alternative technology incremental purchase costs.  Muni Construction Division and Project Integration is to form an Alternative Fuels Facility Task Force (AFFTaC) in order to identify the capital costs necessary in order for Muni facilities to be in compliance with the operational, maintenance, safety, and regulatory requirements associated with alternative technology vehicles.

14.2.   Definitions: 

14.2.1.   Incremental vehicle cost is defined here as the differential cost of alternative technology compared to the purchase cost of conventional diesel transit bus technology.  This can be a positive or negative cost.

14.2.2.   Incremental facility cost is defined here as the additional cost required to modify Muni's existing motor coach facilities in order to support each alternative vehicle technology.  This cost is then divided by the potential number of vehicles to be purchased in each alternative technology category during life of the facility.

14.3.   Significant Variables:  There are many variables associated with this cost analysis including, but not limited to:  Analysis of required level of facility support; analysis of required level of safety requirements; product availability and general market changes; level of manufacturer or provider support desired; differential cost represented by other transit agencies surveyed.

14.4.   Test Personnel: 

14.4.1.   Vehicle Cost:  Muni fleet engineering personnel shall audit industry sources in order to determine incremental vehicle costs.  Sources are to include:  Vehicle manufacturers; propulsion system providers; alternative sub-system providers; alternative technology transit agencies.

14.4.2.   Facility Cost:  Muni personnel representing the following areas shall contribute to AFFTaC report on the facility implications of alternative technology vehicles:  Accessibility services; capital planning and grants; capital planning and legislative affairs; construction electrical/facilities/mechanical design; construction project management; environmental and occupational health; facilities subcommittee; finance; fleet engineering; system safety. 

 

FACILITY COMPLIANCE

Category leader:  PM filter and hybrid.

SUMMARY

In order to accommodate fueling and maintaining alternative fuel buses, Muni must construct special facilities and/or modify their existing diesel infrastructure due to non-compliance with relevant codes and industry standards.  Maintenance facility provisions for CNG are related to safety concerns, while hybrid facility provisions are primarily related to the storage and disposal of batteries.  This analysis focuses on CNG concerns.

Most of the codes and standards were developed around the fact that storing and handling compressed natural gas will accidentally, through human error or equipment malfunction, leak gas into the surrounding atmosphere.  Because natural gas is lighter than air,[78] leaking gas will quickly raise.  In an enclosed storage or maintenance facility, leaking gas will tend to accumulate near the ceiling.  Depending on the volume of the leaking gas, the concentration of accumulated gas near the ceiling could quickly reach the gas' lower or upper flammable limits[79] thus igniting or even causing an explosion in the presence of an ignition source such as a heater or spark.  High temperature elements such as open flame heaters in diesel bus garages will most likely cause the initial ignition of the accumulated natural gas.  Depending on the surrounding area, storing of natural gas buses in an outside open space will definitely reduce, but may not completely eliminate, the risk of igniting accumulated gas in that area.

RESULTS

Because of the volatility of natural gas, fueling and maintaining natural gas buses require safety precautions that do not typically exist in diesel facilities.  In addition, diesel facilities typically include items that are considered safety hazards for natural gas buses.  For example, the ceiling-mounted open flame radiant tube heaters found inside the Woods division maintenance area, although very efficient and practical in diesel facilities, could be a risk hazard if a natural gas bus is stored or maintained in that facility.  Natural gas bus facilities use similar heaters that are specially configured for natural gas buses.  Other examples of non-compliant or non-exiting systems in Woods include: ventilation, fire detection, and lighting systems.

A general list of items that should be considered prior to introducing alternative fuel vehicles into diesel infrastructure includes, but is not limited to, the following items:[80] 

a) Gas Detection and Alarm System

b)   Heating, Ventilation, and Air-Conditioning and System (HVAC)

c) Lighting System

d)   Electrical and Mechanical Systems

e) Fire Fighting (extinguishing) System

f)   Non-Sparking or Explosion Proof Equipment (fans, motors, light fixtures, etc.)

g) Structural/Architect

h) Training (operation and maintenance)

i) Fueling Infrastructure

j) Personnel Protective Equipment

k) Fire Department Personnel Training

l) Emergency Response and Evacuation Procedures

m)  Community Relations

A more detailed list based on fire, safety, and building standards/codes have been adopted by many local officials as the governing codes for construction/modification of alternative fuel facilities.  This set of codes includes:

a) National Fire Protection Association (NFPA) 30A: Automotive and Marine Service Station Code

b)   NFPA 52: Compressed Natural Gas (CNG) Vehicular Fuel System Code

c) NFPA 59A: Standard for the Production, Storage, and Handling of Liquefied Natural Gas (LNG)

d)   NFPA 68: Guide for Venting of Deflagrations

e) NFPA 88B: Standard for Repair Garages

In addition, each community normally develops specific rules and regulations that must also be considered during the planning, design, and construction of natural gas facilities.[81]

EVALUATION CRITERIA

15. FACILITY EVALUATION

15.1.   Evaluation:  All motor coach facilities shall be audited for compliance with the different alternative technologies represented in this study.  This aspect of the study is concerned with the compliance of existing facilities, rather than the potential incremental capital costs associated with modifying existing and planned facilities.[82]  The present state of each motor coach facility and its equipment is rated as compliant or non-compliant for each vehicle technology.  Examples of general facility evaluation categories include, but are not limited to:  compatibility with lighter-than-air flammable gases; provisions for propulsion system battery storage; and provisions for proper hazardous material disposal.

15.2.   Test Personnel:  Both Muni personnel and an outside consulting agency shall individually inspect existing Muni motor coach facilities. 

15.2.1.   Muni Personnel:  Inspections of each Muni motor coach facility for compliance with alternative technologies shall be performed by personnel:  Certified in natural gas facility evaluation; familiar with alternative technology transit facilities; certified in electric vehicle technology and high-voltage power systems; and trained regarding service techniques specific to exhaust after-treatment technology.

15.2.2.   Consultant:  Personnel shall evaluate Muni motor coach facilities for alternative technology compliance based on at least the following fire, safety, and building codes:  National Fire Protection Association (NFPA) 30A - Automotive and Marine Service Station Code; NFPA 52 - CNG Vehicle Fuel System Code; NFPA 59A - Standard for the Production, Storage, and Handling of Liquefied Natural Gas (LNG); NFPA 88B - Standard for Repair Garages.

VEHICLE SAFETY CONCERNS

Category winner:  Inconclusive, due to need for additional analysis.

SUMMARY

The safety category was primarily concerned with the hazards of AFPP vehicle operation on bridges, through tunnels, under electric trolley contact wires, and inside terminals.  Secondary concerns include threats from intentional harm, and earthquake conditions.  In general, the hazard potential from CNG buses during operation is low.  However, it is strongly recommended that certain areas be evaluated further. 

Muni buses operate around City Hall, the Federal Building, the United Nations plaza, the TransAmerica Building, and on the Golden Gate Bridge, which may be considered terrorist targets for various reasons.  Given the volatility of CNG relative to diesel fuel, CNG buses could be considered a target for terrorism, but Muni considers the likelihood of an incident to be extremely low.[83]  The US Geological Survey states that there is a 67% probability that San Francisco will one day experience another Richter-magnitude 7 earthquake.[84]  During the 1989 Loma Prieta earthquake, electricity and natural gas supplies were unreliable in San Francisco.  Fifty-three percent of Muni's entire fleet is currently electric powered.  In the event of an emergency, with gas and electric supplies cut or reduced, a reliable fuel source will be crucial.

Forty percent (40% or 21/52) of Muni's individual standard motor coach lines present a specific CNG bus safety concern. The following 21 Muni lines should be carefully considered before CNG bus service due to vehicle/infrastructure related safety concerns that should be thoroughly investigated:  1 California; three (3) 9 San Bruno Express lines; 10 Townsend; two (2) 28 19th Avenue lines; 29 Sunset; two (2) 30 Stockton lines; five (5) 38 Geary lines; 41 Union; 45 Union-Stockton; 80 Gateway Express; 82 Levi Plaza Express; 91 Owl; 108 Treasure Island.

Until further safety analysis can be performed, CNG bus operation through San Francisco tunnels is not recommended.  While most of the tunnels have natural ventilation due to grade or traffic flow, and any accumulation of small release of natural gas would not likely reach the potentially flammable ranges, an complete engineering/safety study should be performed prior to proclaiming CNG compatibility with San Francisco's tunnels.

Other lessons learned:  The San Francisco Fire Department (SFFD) will require accident response training specific to the CNG buses.

Next steps:  One area that warrants further evaluation is the Transbay Terminal.[85]  Other areas include streets with low trolley contact wires, where the possibility of an explosion exists in which an errant wire may strike a CNG tank on the top of a passing bus.  Hazards in long tunnels such as Broadway, Stockton, and Macarthur present other areas for further evaluation.  A comprehensive safety evaluation and certification must be in place before the procurement of CNG buses or modification of facilities.  Completion of a preliminary Operational Hazard Analysis should be made as soon as possible.

RESULTS

Muni safety representatives conducted a preliminary safety review of CNG facilities requirements.  The recommendation was that all safety issues be addressed prior to the acquisition of the CNG fleet and final design of the CNG facility.  Representatives also advised that further comprehensive operational hazard analysis will likely identify additional safety issues.  These issues may involve policy considerations, resources, and funds needed to mitigate identified hazards.  Specifically, the safety requirements that were identified include:

  Completion of a preliminary Operational Hazard Analysis as soon as possible:  The analysis must include, as a minimum. fleet, facility, and system integration elements including city infrastructure and operational requirements.  The analysis should also include, as a minimum: CNG gas ventilation in tunnels, citywide network of overhead trolley contact wires, and CNG gas ventilation in facility.

  Development of a Safety Certification program for the fleet, facility and integration of the CNG equipment and systems.  Timing of the safety certification is critical.  If the CNG facility is not certified at the time the CNG bus certification is approved, then additional safety requirements must be developed and certified in order to support the safe operation of the CNG bus fleet

  Establishment of the necessary minimum employee qualifications and necessary security requirements. 

  Establishment of the necessary security requirements and development of a Security Certification program.

  Re-evaluation of the safety risk of electric wire/CNG.  Based on Muni's current usage and volume of its overhead line system and support structure, the safety representatives strongly recommended the re-evaluation of the Federal Department of Transportation's classification of an electric wire/CNG risk as "4C".[86]  Muni has a formal risk assessment program in place for Third Street Light Rail project and Metro East facility that should be the basis for a formal risk assessment of this issue. 

  Coordination of Emergency Response. An assessment of city emergency response resources should be incorporated into the overall hazard analysis along with the safety certification program.

This list was not intended to be exhaustive.  Further issues may present themselves in the remaining 18 months of the AFPP.  Safety representatives will add new requirements to this list as the need arises.

Details regarding CNG compliance with bridges, tunnels, low electric trolley contact wires, the Transbay Terminal, and earthquake conditions are listed below.  Lines that are associated with these areas of San Francisco are listed in parenthesis following each specific area.

Bridges:

Golden Gate Bridge

(76 Marin Headlands)

Only vehicles that are required to display hazardous warning signs are not permitted to use the bridge.[87]  Since a CNG transit bus is not required to display a hazardous warning sign, it is permitted to cross.

Bay Bridge

(108 Treasure Island)

A vehicle with an onboard fuel supply equivalent to 120 gasoline gallons ,as is generally the case with CNG transit buses, is permitted to use the bridge.[88]  It should be noted that the Yerba Buena Tunnel, which connects the western span of the Bay Bridge to the eastern span, is not CNG compliant.  The lower (eastbound) deck is a also a concern due to the numerous overhead pockets. 

Mission Creek Bridge[89]

(15 3rd Street; 91 Owl)

This is an open top and sides bridge that presents no hazard potential related to CNG bus operation.

Islais Creek Bridge[90]

(15 3rd Street; 91 Owl)

This is an open top and sides bridge that presents no hazard potential related to CNG bus operation.

Tunnels:

Broadway Tunnel:

(30X Marina Express)

The Broadway Tunnel is made up of a relatively long pair of tunnels that has a ventilation fan in each bore.  However, these fans only operate one at a time, between 7:30 am and 3:30 pm on weekdays, and 6:00 am to 2:00 pm on weekends.  The fan in the north bore is rated at 100,000 cfm, while the fan in the south bore is rated to 30,000 cfm.[91]

Stockton Tunnel:

(9X. 9AX, 9BX San Bruno Express lines; 30 Stockton; 45 Union-Stockton, 91 Owl)

The Stockton tunnel is a relatively long tunnel that has mechanical no provision for natural gas accident avoidance.  However, there is significant natural ventilation in this tunnel.

Geary Tunnel:

(38 Geary Ft. Miley; 38 Geary Pt. Lobos; 38L Geary Limited; 38 Geary Ocean Beach Owl; 38 Geary East of 33rd Avenue Owl)

The Geary tunnel has no mechanical provision for natural gas accident avoidance.  However, there is significant natural ventilation in this tunnel.

Douglas Macarthur Tunnel:

(28 19th Avenue; 28L 19th Avenue Limited, 91 Owl)

The Macarthur tunnel is a relatively long tunnel that has no provision for natural gas accident avoidance.

Golden Gate Bridge Toll Plaza Tunnel:

(28 19th Avenue; 29 Sunset)

The Golden Gate Bridge Toll Plaza tunnel has no provision for natural gas accident avoidance.  The tunnel is roughly 50 yards long, and could be considered essentially an extended overpass.  Of the six (6) San Francisco tunnels, the toll plaza tunnel is the least likely to provide an opportunity for a natural gas related accident.[92]

Yerba Buena Island Tunnel:

(108 Treasure Island line)

The Yerba Buena Island Tunnel has no provision for natural gas accident avoidance.  However, as stated in the Bay Bridge section (above) of these results, passage across the Bay Bridge is allowed based on the relatively small amount of fuel CNG buses carry.  It is therefore implied that operation through the tunnel is also acceptable.

In general, as long as a properly functioning CNG bus is driving through any of these tunnels, there is little cause for safety concern.  However, one must consider special conditions.  One must consider special conditions that may cause safety concern when a natural gas buses are operated in one of San Francisco's tunnels:  What if there is a large CNG release in a tunnel?  What if there is a series of small releases, in a tunnel, from numerous buses over a short time frame?  What if external sources of CH4 find there way into the tunnel such as those routinely in San Francisco when a sewer main ruptures.  It is clear that the tunnels then need modifications: Methane detectors (integrated detectors with tunnel ventilation equipment); and non-sparking mechanical equipment and electric services.[93]

Low Trolley Wires:

Davis Street between Clay Street and Sacramento Street:

(1 California; 80X Gateway Express; 82X Levi Plaza Express; 41 Union)

The trolley wires are under a pedestrian walkway.

1st Street and Fremont Streets between Mission Street and Howard Street:

(10 Townsend; 76 Marin Headlands)

The trolley wires are under the Transbay terminal.

The concern with low trolley contact wires is that they could act as a source of ignition if there were a natural gas leak on roof mounted natural gas fuel cylinders.  Natural gas released under pressure may be trapped in the cupola housing the natural gas cylinders on the roof of a CNG bus.  The escaped gas can possibly accumulate in the cupola, increasing the hazard if an ignition source is available.[94]  San Francisco's many trolley wires operate using roughly 600 volts.  On Davis Street and below the Transbay Terminal, the wires come within 2 feet of the cupola on the top of Muni's CNG buses.  Furthermore, low barometric conditions magnify the possibility of current jumping from the contact wire to a bus.  It should be noted that Muni's low-floor CNG buses are considerably taller than any of the other motor coaches in Muni's fleet, due to their roof mounted fuel cylinders.  The trolley wires on Davis Street and under the Transbay Terminal are roughly 13.5 feet above the street.  In terms of both vehicle and system, a trolley wire related CNG bus hazardous event may occur at some time in the life of an individual bus, and may occur several times in the life of the electric trolley wire system.  However, the hazard severity would be negligible, with less than minor injury, less than minor system damage, and less than minor environmental damage.[95]

Transbay Terminal:

(108 Treasure Island)

Most, if not all, diesel facilities require some modifications to accommodate compressed natural gas vehicles.  Because of this, further analysis of the Transbay Terminal and its compatibility with natural gas buses is warranted.  Operators report poor ventilation inside the Transbay terminal, and often take their breaks outside of the terminal for this reason.

Earthquake concerns:

The 1989 Loma Prieta Earthquake struck at 5:04 p.m. on October 17.  The epicenter of the earthquake was the Santa Cruz Mountains, about 56 miles south-southeast of San Francisco.  While the main regions of destruction were in the Santa Cruz Mountains, along the coasts of Santa Cruz and Monterey counties, and in San Benito County, certain areas of San Francisco and Alameda County were also hit.  When the earthquake hit, most of San Francisco lost electricity.  There were hundreds of natural gas leaks.  During the evening of the earthquake, and the following day, 36 structure fires were reported to the San Francisco Fire Department. Of these fires, 34 were directly or indirectly related to the earthquake and aftershocks.  It has been speculated that the failure of electric service may have been beneficial in reducing the number of potential fires, due to the loss of a possible ignition source for the natural gas.  However, natural gas was responsible for some of the fires following the Loma Prieta earthquake.  Reportedly 500 dispatches were transmitted by midnight of October 17, and of these, roughly 400 were investigations of natural gas odors.[96]  The USGS states that "Events of magnitude 7 or larger, each with a probability of 20 to 30 percent are expected at three locations in Northern California." The locations in Northern California are the San Francisco segment of the San Andreas fault, and the northern and southern segments of the Hayward fault in the East Bay.  "A magnitude of 7 shock on any one of these fault segments will probably cause considerably more damage than the recent Loma Prieta event because of their proximity to larger population centers."[97]  On July 20, 1990, the USGS further revised their probability factor for a Richter-magnitude 7 earthquake to 67%.  This latest revision makes another major earthquake inevitable as far as SFFD planning is concerned.82

EVALUATION CRITERIA

16. SAFETY EVALUATION

16.1.   Evaluation:  This evaluation category focuses on safety from a vehicle perspective.  Data is collected for each bus technology and a relative comparison is made using the Muni's conventional diesel bus fleet as the standard.  The vehicles are evaluated in terms of the hazard potential associated with categories including, but not limited to:  Tunnels; overhead electric trolley wires; bridges; transportation terminals; intentional harm; and natural disasters.  Levels of vehicle safety are difficult to quantify.  Due to the potentially severe consequences associated with hazardous conditions, every effort is made to evaluate vehicle safety using a wide range of techniques:  Safety codes; knowledge and experience from similar alternative technology users; statements from local agencies and departments; analysis of previous accidents.

16.2.   Significant Variables:  Due to the fact that a safety evaluation is generally concerned with either the intermittent occurrence of known hazards, and the possibility of unknown hazards, there are virtually endless variables that have an effect on the analysis of potential vehicle hazards.  Compounding the variability of this safety analysis is the fact that simultaneous occurrences of multiple non-hazardous conditions may together create a new hazard.  One school of thought that states that there is no such thing as an "accident."  While this is debatable, the fact remains that controlling all of the variables involved in an accident is the key to safety.  Every attempt is made in this study to identify known safety variables, so as to better advise regarding accident prevention.

16.3.   Test Personnel:  Many different sources are used in the evaluation of alternative transit vehicle safety in San Francisco:

16.3.1.   Muni:  Safety personnel are asked to evaluate alternative vehicle safety independently of other evaluation efforts for these vehicles.

16.3.2.   Bridges:  Bridge managers and maintenance supervisors are surveyed for alternative vehicle compliance statements based on their particular bridge.

16.3.3.   Tunnels:  Bureau of Street and Sewer Repair personnel, and Presidio alternative fuel personnel are surveyed for alternative vehicle compliance statements based on their particular tunnels.

16.3.4.   Overhead Electric Trolley Wires:  Federal Transportation Agency's (FTA's) Transportation Safety Institute (TSI) is asked to provide assistance in evaluating the hazard potential of low trolley wires as they relate to roof mounted CNG fuel containers.  TSI has previously analyzed this potential hazard in Cleveland and Boston.

16.3.5.   Intentional Harm:  Agencies to be surveyed for alternative vehicle compliance with potential acts of extreme vandalism and terrorism include:  San Francisco Fire Department (SFFD); San Francisco Police Department (SFPD); California Highway Patrol (CHP); and New York City Transit Authority (NYCTA).


APPENDIX A

 

"11-POINT AGREEMENT"

 

Muni Bus Purchase Proposal

Developed in cooperation with Municipal Transportation Agency

and Department of Environment staff

 

Background

 

Muni operates a fleet of 455 diesel motor coaches. Many vehicles are operating beyond their approved 12 year life span, resulting in breakdowns and delays in service to passengers. There is consensus that Muni's older vehicles are highly polluting models that should be removed from service as quickly as possible.

In 1997, Muni received approval from the San Francisco County Transportation Authority to replace approximately half of its fleet (235 vehicles, including 135 40' motor coaches and 100 60' articulated coaches) with diesel buses. The proposed contract with Neoplan also included a future potential option to purchase 175 vehicles.

Environmental groups including the Union of Concerned Scientists, the Natural Resources Defense Council and the SF League of Conservation Voters initially opposed the purchase of diesel buses. At the time, Supervisor Ammiano sponsored negotiations with Muni and the environmental coalition which culminated in an agreement by Muni to acquire and test 2 CNG and 2 hybrid-electric motor coaches for an alternative fuel pilot program and for Muni to develop a plan for potential electrification of diesel routes. The Transportation Authority approved the proposed bus purchase but provided direction to implement the alternative fuel pilot program. Due to several factors, Muni's pilot program had not commenced road tests as of the beginning of 2001.

On the heals of a contentious decision to adopt the diesel fuel path in response to the CARB Transit Bus Emissions Regulations in late 2000, Muni prepared to approach the Transportation Authority in January of 2001 for approval to exercise its Neoplan option to replace 175 vehicles. The environmental coalition that opposed Muni's diesel fuel path choice, which included the Union of Concerned Scientists, the American Lung Association, Our Children's Earth, the Planning and Conservation League and Bayview Hunters Point Community Advocates, geared up to oppose approval of new diesel buses.

Negotiations

Supervisor Ammiano requested that Muni negotiate a one month deferral of the option with Neoplan so that the various sides could discuss a potential compromise. Discussions occurred over approximately a three week period and included representatives of each of the environmental organizations, Rescue Muni (supporting Muni's position) and city staff from Muni, the Department of the Environment, the City Attorney's Office and the Department of Public Health.

The discussions revealed underlying differences of opinion as to whether purchasing natural gas technology would pose a risk to the reliability of Muni service and the extent to which purchasing diesel versus alternative fuel bus technology would reduce air pollution in the City.

The following proposed bus purchase is the product of these negotiations and has the support of Supervisor Ammiano, Muni and Rescue Muni. Parts of the plan are also supported by staff of the Department of the Environment. While praising the progress made during the negotiations, the environmental coalition does not support the final proposal due to objections about the number of diesel buses contemplated and the failure to commit immediately to CNG technology.

 

 

Proposed Muni Bus Purchase Plan

This proposal assumes release of local match dollars sufficient to purchase a total of 95 diesel motor coaches equipped with particulate trap emission controls. Assuming successful completion of prototype testing of CNG and diesel-electric hybrid buses scheduled to begin this month, Muni will purchase either CNG or diesel-electric hybrid buses for the remainder of Muni's motor coach replacement plan, which will require at least 105 additional vehicles.

The proposal also includes:

  a schedule for installing pollution controls on the remainder of Muni's diesel fleet that is more aggressive than that required by state regulations;

  retrofit of Muni facilities to handle lighter-than-air fuels pending identification of funding;

  development of an electric trolley coach expansion plan for up to 6 bus lines;

  commencement of testing and/or in-service use of a variety of alternative fuel bus technologies within 24 months, including fuel cell buses;

  deployment of Muni's cleanest vehicles in the City's most polluted neighborhoods; and

  interdepartmental planning to incorporate health needs of the Bayview Hunters Point communities in future transportation planning.

The plan is designed to ensure that Muni will, as an organization, become experienced at adapting to and operating the newest and least polluting bus technologies available in the future. The plan is also designed to pose the least risk to Muni's ability to meet the service standards required by Proposition E. Major elements of the plan are subject to future approval by the Municipal Transportation Agency Board, the San Francisco County Transportation Authority and the San Francisco Board of Supervisors.

I.   Approve purchase of 95 diesel buses; defer purchase of 80 buses

The older 60-foot articulated buses in Muni's fleet are on average over 18 years old, six years past their useful life, as defined by FTA standards.

Muni will purchase 24 60' articulated buses and an additional 71 standard 40' diesel coaches under this plan. Muni will defer the purchase of the remaining 80 diesel buses pending the outcome of prototype testing of compressed natural gas (CNG) and diesel hybrid-electric motor coaches.

II.   Commence prototype testing of 2 CNG and 2 hybrid-electric buses to inform the purchase of 80 40-foot coaches

Starting March, 2001, Muni will commence prototype testing of 2 CNG and 2 diesel-electric hybrid buses, with independent oversight by the Department of the Environment, an independent consultant and a peer review panel with representatives from transit agencies that successfully operate CNG buses. The prototype program will last for 8 months prior to issuance of the resulting RFP for the purchase of 40-foot coaches (3/01-10/01); prototype testing will continue for an additional 18 months thereafter.

III.   Commence specification and procurement by developing an RFP for 80 CNG or diesel-electric hybrid buses

Concurrent with the prototype testing, Muni will begin developing specifications and an RFP for 80 CNG or diesel-electric hybrid 40-foot coaches.

If prototype testing is successful, CNG or diesel-electric hybrid buses will be operated along the following proposed routes which Muni has determined offer the best topography and service levels for these technologies: lines 2, 16AX/BX, 17, 23, 28, 47, 80X, 81X, 82X, 88, 89.

Muni's research has found that agencies with lower ridership and lighter duty cycles are generally more successful with CNG technology.  Agencies with high ridership and heavy urban duty cycles have been less successful; these agencies consistently cite higher-than-anticipated operating and maintenance costs for CNG technology.

This research supports Muni's assertion that a comprehensive testing of CNG and diesel-electric hybrid technology in the San Francisco operating environment is essential prior to making a commitment to invest in CNG or diesel-electric vehicles and infrastructure.

IV.   Acquire a minimum of 15 CNG 40-foot coaches for revenue service, subject to satisfactory completion of prototype testing and acquisition of fueling infrastructure

To gain revenue service experience with lighter than air alternative fuels, Muni will purchase a minimum of 15 CNG 40-foot coaches for in-service use, subject to satisfactory completion of prototype testing and acquisition of fueling infrastructure. Installation of fueling infrastructure must be free, with guarantees of CNG fuel at or below the cost of diesel or the Transportation Authority must identify funding for fueling infrastructure.

If prototype testing of CNG and diesel-electric hybrid coaches indicates the same reliability and the minimum conditions described above are met, Muni will favor the purchase of CNG buses for the remaining 65 40' coaches; otherwise Muni will seek Transportation Authority and Board of Supervisors approval to purchase 65 40' diesel-electric hybrid buses. Muni will only approach the Transportation Authority seeking approval of the option to purchase 80 diesel coaches in the event that prototype testing fails.

V.   Purchase CNG or diesel-electric hybrid coaches to replace 30' Orion motor coaches, contingent on successful prototype testing

 

Muni is in the early stages of planning to replace 25 30' Orion coaches. Subject to successful prototype testing, Muni will purchase either CNG or diesel-electric hybrid buses to replace these coaches.

VI.   Accommodate maintenance of vehicles fueled by lighter than air fuel through the redesign of Islais Creek maintenance facility and part of the Woods maintenance facility

Subject to availability of funds, Muni will re-engineer the final design of the proposed Islais Creek maintenance facility and retrofit part of the existing Woods maintenance facility to accommodate fueling and related infrastructure required to operate motor coaches fueled by lighter than air fuels (e.g., natural gas, hydrogen, etc.).

It is expected that the next significant change in transit bus technology will be toward hydrogen-based fuel cells and that this change could occur within a decade. Since the Islais Creek maintenance facility is projected to serve Muni for 30 to 50 years, re-engineering of the final facility design to accommodate lighter than air fuels is considered cost-effective.

Muni is in the process of applying for funds for preliminary facility engineering and design for incorporation of CNG technology. These federal and state funds, whose funding cycles begin annually in March, can be used either for conversion of an existing facility or re-design of Muni's future facility, Islais Creek.

VII.   Develop electric trolley coach expansion plan

Although the initial capital investment in the overhead system for electric trolley buses is high, there are future life-cycle savings due to the less costly operation of trolley coaches (reduced maintenance and power expenses) and the longer life expectancy of the trolley coaches. There are also environmental benefits associated with trolley coach operation, especially with respect to pollution and noise reduction.

Muni will develop an electrification plan and timeline for converting up to 6 bus lines and report at least annually to the Transportation Authority regarding progress on planning and implementation.

Muni's analysis determines 2006 as being an aggressive and optimistic timeline for a line to be electrified and in revenue service. The Transportation Authority and the environmental coalition will prioritize identifying funding and participating in building community support for electrification of bus lines.

VIII.   Participate in a fuel cell pilot program

Due to the fact that approximately half of Muni's fleet is electrified, Muni is not currently required to participate in a fuel cell bus pilot program under California Air Resources Board rules for transit agencies, despite having selected the diesel path under CARB rules.

Muni will participate in a fuel cell pilot program, either through the Fuel Cell Partnership or in cooperation with AC Transit within 24 months pending resolution of funding questions.

IX. Deploy the cleanest alternative fuel and/or diesel buses in neighborhoods most afflicted by multiple pollutant sources

In recognition of the significant levels of pollution afflicting several San Francisco neighborhoods, Muni will deploy its cleanest alternative fuel and/or diesel buses fitted with particulate traps in the most seriously polluted neighborhoods. All neighborhoods will eventually benefit from substantially cleaner bus technology.

X. Determine ways that the health needs in the Bayview Hunters Point communities can be incorporated into future transportation planning

Muni will work in close cooperation with the Department of Public Health, the Department of the Environment, community leaders, and advocates from the Bayview Hunters Point communities to develop a set of health-based criteria to be used by planners and community representatives as an evaluation metric for clean air transit strategies. Muni will also identify desirable transit alternatives not provided by existing services that could meet community health needs and work with community leaders and advocates to advertise and market future improvements to public transportation in this area.

 

XI. Retrofit diesel buses purchased since 1997 with particulate traps and convert to low-sulfur diesel fuel by the end of 2002

Under the diesel fuel path requirements of CARB Transit Bus Emissions Regulations, Muni would normally be required to install particulate traps on its entire diesel fleet by the end of 2007. Under this agreement, Muni will retrofit diesel buses purchased since 1997 with particulate traps and convert to low-sulfur diesel fuel by the end of 2002.

 


APPENDIX B

 DEFINITIONS, ACRONYMS, AND ABBREVIATIONS

AFFTaC: (Muni) Alternative Fuels Facility Taskforce Committee.

AFPP:  Alternative Fuel Pilot Program.

ASME:  American Society of Mechanical Engineers.

Bki:  Bevilacqua-Knight, Inc.

BTU:  British Thermal Units of energy.

CARB:  California Air Resources Board.

CARB-2 diesel fuel:  Defined as ~120 ppm sulfur content.

CaTTS:  California Truck Testing Services; chassis dynamometer.

cfm:  Cubic feet per minute.

CHP:  California Highway Patrol.

Clean-diesel:  Industry term for 1997 and newer 4-cycle diesel engines.

CNG:  Compressed Natural Gas.

CO:  Carbon monoxide.

Cummins:  Cummins Engine Company, Inc.

dBA:  Decibels measured on the A-weighted sound level scale.

DDC:  Detroit Diesel Corporation.

DGE:  Diesel Gallon energy Equivalent.

Dwell:  Amount of time spent with doors open at bus stop.

ENRG:  ENRG Clean Transportation.

Failure:  Any event requiring a road call or forfeit of passenger

service.

FTA:  Federal Transit Administration.

GGE:  Gasoline Gallon energy Equivalent.

Grade:  The percent inclination of a hill.

GVW:  Gross Vehicle Weight; total maximum allowable vehicle weight

(bus+load).

Hybrid:  Electric motor, batteries, and internal combustion engine

Combined as one propulsion system package.

In-use:  In reference to data that is collected while vehicle is in

service.

IOC:  Independent Oversight Committee for AFPP.

ITS:  Institute of Transportation Studies at the University of

California, Davis.

Kirkland:  Muni motor coach division on North Point at Stockton.

LFL:  Lower Flammability Limit.

LNG:  Liquid Natural Gas.

Marin Street:  Muni motor coach division on Marin Street at Indiana.

MDBF:  Mean distance between failures.

MPH:  Miles per hour.

SFMTA:  Municipal Transportation Agency.

MTC:  Metropolitan Transportation Commission.

Muni:  San Francisco Municipal Railway.

NABI:  North American Bus Industries.

Neoplan: Neoplan USA Corporation bus manufacturer.

NOx:  Oxides of nitrogen.

Opacity:  Measurement of exhaust or smoke visual quality.

Orion:  Orion Bus Industries.

Parallax:  Measurement-taking error caused by reading an analog dial

from a side, rather than directly in front.

Pinnacle:  Pinnacle Natural Gas Co.

PM:  Exhaust Particulate Matter; also Periodic Maintenance.

ppm:  Parts per million.

Propulsion system:  Engine and either motor or transmission that

together power the vehicle's drive wheels.

Protractor:  Device used to measure angles and grades. 

psi:  Pounds per square inch pressure.

Regenerative braking:  Electric braking that supplements the

mechanical/foundation brakes.

Road call:  Vehicle on-road failure preventing continuation of service.

Run:  Set of specific trip times on a specific line.

SAE:  Society of Automotive Engineers.

SFCTA:  San Francisco County Transportation Authority.

SFFD:  San Francisco Fire Department.

SFPD:  San Francisco Police Department.

SOC:  State of charge for the hybrid bus propulsion batteries.

Specific gravity:  Weight of a gas or liquid relative to air or water.

Terminal speed:  Maximum speed at which vehicle accelerate equals zero.

Transparent:  When vehicle is thought to be indistinguishable to

operator, operations, or during maintenance procedures from other

similar vehicles.

Trillium:  Trillium USA.

Turnkey:  Ready for immediate use.

UC Davis:  University of California at Davis.

ULSD:  Ultra Low Sulfur Diesel fuel.

Ultra-capacitor:  Electrical energy storage device sometimes used in

place of batteries.

UFL:  Upper Flammability Limit.

USGS:  United States Geological Survey.

Woods:  Muni motor coach division on Indiana Street between 22nd and 23rd

Streets.

30-foot bus:  Muni 9000 Series.  Standard coach mainly used in narrow

residential areas.

40-foot bus:  Muni 8000, 8100, 8200, 8800, 8900, 9200 Series.  Standard

coach making up majority of Muni bus fleet.

60-foot bus:  Muni 6200, 6300 Series.  Articulated coach easily

identified by "accordion" middle section.


APPENDIX C

An Acrobat PDF (400kb) version of Appendix C will allow you to view slides more easily.

PRELIMINARY CHASSIS DYNAMOMETER TEST RESULTS

FOR FOUR TYPES OF ADVANCED TECHNOLOGY BUSES

Notes:  Driving cycles are speed-time traces that represent vehicle operation.  Differences in facilities and vehicle design (i.e., vehicle weight, engine size, and programming) result in variation between our findings and others, however, results from other alternative vehicle projects are presented to confirm that the results are reasonable

Notes:  The CBD is a geometric cycle that consists of 14 identical peaks.  Each peak is an acceleration to 20mph, a cruise, and then a deceleration to idle. The cycle is approximately 2 miles long, takes 600 seconds to complete, and has an average speed of 12.6 mph.  The severe decelerations are not typical of the Muni operations we observed thus far.  The CBD Cycle may not reflect real-world hybrid bus performance because regenerative braking that may occur in reality (i.e. during slower decelerations) does not take place during the CBD Cycle's steep decelerations.

Notes:  Closer but still not SF.  The New York Bus Cycle (NY Bus) was developed from speed-time data collected from heavy-duty vehicles (both trucks and transit buses) in New York City, but the cycle was statistically generated using Monte Carlo simulation. This cycle (Figure 2) is 571 seconds in length, covers a distance of approximately 0.6 miles, and has an average speed of 3.7 mph.  Although this average speed is lower than we observed for San Francisco, the NY Bus Cycle does offer a variety of acceleration and deceleration rates more typical of in-use operation.  These rates are less severe than those in the CBD, which allows the regenerative braking system of hybrid vehicles to capture vehicle inertial energy.

Notes:  San Francisco has unique terrain and operating characteristics that are not reflected in either the NY Bus or CBD Cycles.  Driving cycles were created specifically for San Francisco by collecting vehicle characteristics (e.g. vehicle speed, engine speed, and power) from the alternative fueled buses operating on three Muni routes.  The data were obtained by logging engine data bus signals via the communications ports in the buses.  Data were collected on three routes at non-peak times on weekdays. Traffic counts were used to verify that the traffic conditions were similar for each data collection. Three sections of the route data were selected which represented diverse Muni bus operations. One route section was relatively flat with high pedestrian concentrations and frequent stops and starts.  The second section had long, steep upgrades with few stops.  The third route section was dominated by moderate downgrades and had few stops. 

Note:  All averages for replications on tests.  So each point varies by factor of 4.

Note:  Two tests not are not enough.  A larger average is needed.

Notes:  Fuel economy was compared on the basis of diesel fuel consumption in units of miles per gallon.

In order to compare the fuel economy of the CNG bus, CNG fuel consumption was converted to diesel gallons equivalent using a conversion factor of 137 cubic feet of natural gas per gallon of diesel fuel.  Fuel economy from the diesel bus and the diesel bus with trap were expected to be similar since properly operating traps do not affect fuel economy.  The results of the SF 3- Route Cycle are consistent with this.  However, the buses with traps were more than 20% less efficient on the NY Bus Cycle.  This decrease in fuel economy may be attributed to sulfur in the fuel interfering with the traps and creating a backpressure.  Muni is in the process of switching to a low sulfur fuel which will enable optimal performance of the particulate traps.  Currently, Muni does use CARB 2 diesel fuel which has a sulfur level of 120 ppm or less.  That fuel was run through the buses when they were tested, but the residual sulfur was in the trap. It is possible that the levels of sulfur in the trap differed between the tests on the buses with the diesel than on the diesel with trap.

Notes:  Fuel economy was compared on the basis of diesel fuel consumption in units of miles per gallon. In order to compare the fuel economy of the CNG bus, CNG fuel consumption was converted to diesel gallons equivalent using a conversion factor of 137 cubic feet of natural gas per gallon of diesel fuel.  Fuel economy from the diesel bus and the diesel bus with trap were expected to be similar since properly operating traps do not affect fuel economy.  The results of the SF 3- Route Cycle are consistent with this.  However, the buses with traps were more than 20% less efficient on the NY Bus Cycle.  This decrease in fuel economy may be attributed to sulfur in the fuel interfering with the traps and creating a backpressure.  Muni is in the process of switching to a low sulfur fuel which will enable optimal performance of the particulate traps.  Muni recently converted from using CARB-2 diesel fuel which has a sulfur level of 120 ppm or less.  That fuel was not run through the buses when they were tested, but the residual sulfur was in the trap.  It is possible that the levels of sulfur in the trap differed between the tests on the buses with the diesel than on the diesel with trap.


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[1]  The heavy-duty chassis dynamometer in Richmond, CA. is one of five such facilities in North America.

[2]  The Hyde Street cable car line has Muni’s most extreme grade at 21%.  Motor coaches are expected to operate on this line if cable car operation is not possible.

[3] Faster and slower running times impact operating costs.  For example, a bus that runs on hilly lines (19, 23, 29, 44,48,and 54 lines) and completes its run time 6% faster than scheduled saves $3.2 million annually compared to a bus that runs 5% slower on those same lines.  A bus that runs 6% faster on flat lines (2, 17, 23, 28, 47, and 88 lines) saves $2.3 million annually compared to a bus that runs 5% slower on those same lines.  A detailed analysis of this and other operating costs is found in this report’s Cost: Operating Cost section.

[4] This data is consistent with testing undertaken by the Sacramento Regional Transit District.

[5] Muni will be testing the effects of Exhaust Gas Recirculation (EGR) equipment on emissions and fuel economy on 15 of its conventional diesel buses, in 2002-03.  The Bay Area Air Quality Management District (BAAQMD) recently awarded Muni a grant to test the efficacy of NOx reduction equipment (EGRs) and PM filters on these 15 Muni buses.

[6] Survey results are based on a very limited sample of 18 surveys and follow up discussions with passengers.

[7]  All service reliability statistics are based on the first 6 months that all buses were in service at Muni, regardless of the model year of the bus.  Muni did not compare the service reliability of new 2001 buses to broken-in 1999 buses.  Instead, Muni used service reliability data for the 1999 NABI conventional diesels, based on records from their initial 6 months in service with Muni. 

[8]  Fuel evaluations were made by converting natural gas into its diesel gallon energy equivalent.

[9]  Technology specific maintenance is defined as any maintenance activity pertaining to the propulsion and fuel systems of the vehicles, as well as any other subsystem associated with these areas.

[10]  Muni paid approximately $320,000 for each of its newest Neoplan coaches.  A PM filter would cost approximately $10,000.

[11]  The BAAQMD recently approve a grant for Muni to test EGR technology on 15 of its conventional diesel buses.

[12]  Source: John Haake, Southwest Regional Sales Manager of Orion Bus Industries, 707-838-8352.  Mr. Haake also stated that with larger quantities or when production becomes standard the pricing should be between $385,000-425,000.

[13] The Regional account funds alternative fuel vehicles but not infrastructure.

[14] Boston and Cleveland have similar concerns with CNG buses passing under overhead trolley wires.  In those cities, the probability of a hazardous event occurring on a system that is working within design specifications has been assessed as “4C” by the US Department of Transportation Federal Transit Administration’s Office of Safety and Security rating on mil-std-992D, using standard hazard assessment evaluation techniques.

[15]  For example, the large gasoline fuel tanker trucks that one can find throughout San Francisco have greater potential for damage if targeted.  It should also be noted that New York’s CNG buses still operate daily, but security for all facilities has been increased.

[16]  New York City tested alternative bus technologies on its streets for two years before deciding to include a combination in their fleet.

[17]  The AFPP Independent Oversight Committee (IOC) and program timeline were established through Supervisor Ammiano’s office as part of the 11-point agreement.  See Appendix A.

[18]  2004 California Air Resources Board (CARB) engine emissions certification standards, specifically NOx levels, may not be met by diesel powered engines used conventionally.  Furthermore, it is unclear whether either natural gas or diesel fuel, used in a conventional transit bus, will be able to meet 2007+ standards.  At a certain point, neither fuel will be able to meet CARB emissions standards, since any form of an internal combustion engine cannot be considered zero-emission – which is where vehicle emissions standards are headed.

[19]  The Trillium USA CNG fuel station at San Francisco International Airport, and the Olympian/ENRG fueling station on 3rd Street at 23rd Street are the only local facilities capable of the high pressures required for Muni’s CNG buses while allowing adequate vehicle accessibility.

[20]  One pair of NABI buses remains unmodified in order to provide a control group for the study.  It should be noted that while Muni’s 2000 Neoplan standard diesel buses are more current than the NABI buses, they were not available for testing purposes when the AFPP began.  Now that they are available, it is recommended that they be used as the AFPP control group.  However, note that the 2000 Neoplan diesels and 1999 NABI diesel engines are covered by the same CARB emissions certification standards.

[21]  The California Truck Testing Services (CaTTS) heavy-duty chassis dynamometer in Richmond, CA. is one of five such facilities in North America.

[22]  PM is the term used for a mixture of solid particles and liquid droplets found in the air.  These particles can cause health problems in the respiratory system.

[23]  NOx, is gas that reacts with carbon monoxide and hydrocarbons to form smog.  Long-term exposure to NO2 may cause lung problems.  NOx also contributes to the formation of acid rain.

[24]  Carbon monoxide (CO) is an odorless, colorless gas that interferes with the delivery of oxygen in the blood to the rest of the body.  It is produced by the incomplete combustion of fuels.  CO combines with NOx and hydrocarbons (HC) to create smog.

[25]  Driving cycles are speed-time traces that represent vehicle operation.

[26]  State of charge (SOC) is a parameter related to the hybrid batteries.  SOC must be the same at the beginning and end of an emissions cycle, or else corrected for in the final analysis of that cycle.

[27]  Survey results are based on a very limited sample of 18 surveys and follow up discussions with passengers.

[28]  Ultra low sulfur diesel (ULSD) has sulfur content of ~15 ppm or less.  The California Air Resources Board (CARB) has mandated its use by transit agencies by July 1, 2002.  Muni converted in January 2002.

[29]  Excess sulfur (due to Muni’s previous use of 120 ppm sulfur diesel fuel before converting to ~15 ppm ultra low sulfur diesel fuel) is actually cooked off of the filter elements by the manufacturers in order to ensure optimized emissions, fuel economy, and exhaust opacity results with ULSD fuel.

[30]  Setting the machine to manual trigger may help to capture the data.

[31]  This is the lowest measured level during testing. 

[32]  The engine-transmission layout on both CNG and diesel bus technologies is considered a conventional motor coach layout, as opposed to the hybrid technology, which offers sound reduction due to its use of a small-engine/generator/electric motor layout.

[33]  Streetside is the driver’s side of the bus.  Curbside is the side of the bus with passenger doors.

[34]  The hold feature allows the instrument to capture the highest noise level reading during testing, rather than dynamic readings.

[35]  This is the most extreme acceleration test grade.

[36]  Since engine power and torque curves are almost identical between the control group buses and the CNG buses, and axle ratio for the CNG bus is less, the difference in performance is likely a function of the extra 3000 pounds that the CNG bus carries in fuel storage.  Note that Liguid Natural Gas (LNG) vehicles virtually eliminate this weight differential.

[37]  Hyde Street between Bay and Francisco.

[38]  These high grades are not served by motor coaches during normal operation.  This is due to the superior hill climbing ability of both cable cars and electric trolley coaches.  However, motor coaches are required to operate on these lines during a power outage, prolonged street blockage or any activity that removes required cable car or trolley bus street infrastructure.  For example: cable or track maintenance, or overhead trolley wire work.

[39]  If vehicle speed is less than 55 mph, then the vehicle is at its limit prior to taking top speed data for this grade.

[40]  If vehicle speed is less than 45 mph, then the vehicle is at its limit prior to taking top speed data on this grade.

[41]  All vehicle weights are based on full fuel loads.  An average passenger weight is assumed to be 150 pounds.

[42]  Muni’s free New Year’s Eve service is an example of holiday operation where extreme passenger loads are common.

[43]  Extreme grades are found on the Potrero Hill and Hunter’s Point sections of the 19-Polk line.

[44]  See previous section of this report: Emissions: Tailpipe Exhaust Emissions.  In theory, the on-road and dynamometer numbers should have been closer.  Work is being done to identify possible reasons for this discrepancy.  Perhaps this is the difference between the laboratory and actual in-use data.  Other possible explanations could be that the sulfated PM filters could have influenced fuel economy differently as they became more and more “clogged” with ~120 ppm sulfur fuel (the fuel economy data was taken months before the chassis dynamometer tests).  Furthermore, other studies have shown hybrid buses to be as fuel efficient, or more so, than the other technologies.  Since both chassis dynamometer and on-road results found the hybrids to be in between conventional diesel and CNG technologies, additional data is clearly called for here.

[45]  Ultra low sulfur diesel fuel.  CARB has mandated its use by July 1, 2002 for all transit agencies running diesel fueled buses.

[46]  See the discussion of diesel gallon equivalents of energy (dge) in this report’s Evaluation Criteria section 6.2.

[47]  Fuel economy data for the hybrids is based upon limited data due to interrupted data collection.

[48]  The CNG buses carry 24,000 scf of gas, as opposed to the 18,000 scf most CNG buses carry.  Therefore, Muni considers this to be the maximum possible range for this bus configuration, since there’s simply no more room for more fuel storage on the roof.  However, 390 miles is more than adequate range, and in fact, could possibly be reduced in order to reduce vehicle weight.  Likewise, hybrid range can be increased from 300 miles by specifying a larger fuel tank.

[49]  Once reaching about 200 psi primary fuel supply pressure, the CNG buses would experience ever-decreasing power for a short distance before final fuel starvation.

[50]  Range data for the hybrids is based upon limited data due to an interruption during data collection.

 

[51]  A larger response to the surveys is clearly required during the remaining AFPP.

[52]  Hybrid buses do not have transmissions, and therefore, do not shift gears.  Hybrid bus speed varies proportionally with the speed of its drive motor.  This same motor allows for regenerative (electric) braking, which helps to provide smoother deceleration.

[53]  Chassis issues and comments regarding systems not related to CNG or hybrid technology were omitted.

[54]  Note that while this comment seems to contradict the 81.9 dBA rear seat area noise level measured on the hybrid buses, it is agreed that the rear seat area seems too loud qualitatively.  See this report’s section on Emissions: Vehicle Noise Levels.

[55]  Eighteen (18) test surveys were administered by the preliminary survey designer. The trend assumptions above are his alone and based heavily on the follow-up conversations with riders on the alternative technology vehicles. These assumptions have not been statistically justified given the limited data collected.

[56]  NYCT Operating Experience with Hybrid Transit Buses, as presented at the SAE Truck and Bus Meeting in Chicago, November 13, 2001. NYCT Experience with Clean Fuel Technologies, as presented at the World Bank Sustainable Transport Meeting , January 16, 2002.

[57]  All vehicle weights are based on full fuel loads.  An average passenger weight is assumed to be 150 pounds.

[58]  1999 NABI conventional diesel reliability rates are based on records from their initial 6 months in service with Muni.

[59]  Local Lodge #1414 - International Association of Machinists and Aerospace Workers.  Contact John Moran, Business Representative/Organizer, 800-231-1305.

[60]  Ultra low sulfur diesel, mandated by California Air Resources Board by July 1, 2002.

[61]  Hybrid propulsion system battery is still being determined.  New hybrid bus products may use ultracapacitors in place of the propulsion systems batteries found on Muni’s hybrids.  These devices should not require replacement at the same rate as conventional batteries.

[62]  Diesel Gallon Equivalent of energy. 

[63]  Hybrid and PM filter bus MPG numbers reflect the fact that these vehicles may have had low fuel economy due to Muni’s previous use of ~120 ppm sulfur diesel fuel, which may have caused additional exhaust backpressure in the PM filters of these vehicles due to the PM filters not completely burning off the excess sulfur after Muni converted to ~15 ppm ultra low sulfur diesel fuel.

[64]  Hybrid fuel economy based is on ~150 mile data set. Data collection was interrupted during the hybrid evaluation of fuel economy.  The hybrid data represents only the short-term fuel economy of the hybrid buses, so fuel cost per mile is estimated based on this limited data.

[65]  See Appendix A.

[66]  Source of vehicle cost information: Orion Bus Industries, John Haake, Southwest Regional Manager (707-838-8352).  Source for incremental facility cost information: Muni Alternative Fuels Facility Taskforce Committee (AFFTaC).

[67]  A fuel cell derives energy from a fuel source such as hydrogen and provides it as electricity.  The by-product from the process of combining hydrogen fuel with oxygen to provide electricity is H2O (steam).

[68]  Muni’s entire fleet of 1999 and newer diesel buses will be retrofitted with PM filters within the next year.  The PM filters are mandated by CARB for 1996 and newer diesel buses beginning in 2005.

 

[69]  Estimate based on including all related costs in addition to hardware.

[70]  See the Facility Compliance section of this report.

[71]  See this report’s Safety section summary.

[72]  According to PG&E, the Trillium USA CNG facility at SFO is similar in size to one that would be necessary to serve 80 transit buses.  PG&E’s charge to connect their natural gas transmission system was approximately $18,000.  It should be noted that these charges are dependent on a number of factors which have yet to be determined. Muni will need to submit a formal request for service before PG&E can developed even order of magnitude costs for the project.  Actual costs are dependent on site, distance to PG&E main, and capacity of main, and are being evaluated for the Islais site; cost may be rolled into a 3rd-party gas provider contract.  PG&E information provided by Bill Zeller, PG&E Clean Air Transportation department (415-257-3353).

[73]  This retrofit is estimated to be 50% more costly than incremental capital costs associated with building a new facility.

[74]  Storage of large volumes of natural gas may not be feasible in San Francisco.

[75]  See Appendix A, point IV.

[76]  $0.04-$0.10 per therm to pump and compress gas, based on LAMTA data, equates to roughly $0.05-$0.13 per DGE.

[77]  No third-party provider surveyed discussed tying price of gas to price of diesel.  Assumptions: Average Muni bus travels 90 miles per day; 36 DGE per CNG coach daily (avg); 65 of 80 coaches would be in service on weekdays and weekends, as preferred alternative technology vehicles; 854,100 DGE consumed annually by an 80-coach CNG fleet.

 

[78] Natural gas has a specific gravity 0.6 vs. 1.0 for air.

[79] The flammability range for natural gas is 5-15% by volume.

[80] Note that this list is a general guideline, not design criteria.

[81]  Facility compliance summary and results primarily based on February 1, 2001 analysis report on Muni’s Woods Division maintenance area by Yazeed Khayyat, Manager, Advanced Bus Technologies, Parsons Brinckerhoff Transit & Rail Systems, Inc. (973-565-4891).

[82]  See this report’s section: Cost: Capital Cost.

[83]  For example, the large gasoline fuel tanker trucks that one can find throughout San Francisco have greater destructive potential as a target.  It should also be noted that New York’s CNG buses still operate daily.  However, the New York Police Department (NYPD) has expressed concern over CNG buses and facilities.  Security for all transit facilities has been increased in the New York City area.  NY information provided by Dana Lowell, Assistant Chief Maintenance Officer, R&D, Dept. of Buses, New York City Transit (718-927-8629).  A strong pre-trip inspection program, sound safety critical items purchased with the bus and hardening of fueling areas as well as the main CNG feeds will help to mitigate potential terrorist issues.  Once this is accomplished, operator training is the key issue.  The concern is along the lines of a bomb strapped to the CNG tanks themselves, which can generally be controlled with good security and inspection procedures.  It should be noted that Israel, while having a significant problem with bus bombings in general, has not had a problem with their CNG buses.  This could be because terrorists do not target them (it is more difficult to produce the intense fire that is generated with a diesel fuel burn after the initial explosion) or that more intense pre-trip inspections are performed on CNG buses prior to roll out, and they limit the CNG buses to "safe" routes.  The San Francisco concern is more related to the fueling areas and fuel storage areas (cascade area), as well as the main CNG service feed into the property.  These areas are less protected and would create a larger impact than a single vehicle.

[84]  United States Geological Survey report "The Loma Prieta Earthquake of October 17, 1989."

[85]  The 108 Treasure Island line operates inside the Transbay Terminal.

[86] Boston and Cleveland have similar concerns with CNG buses passing under overhead trolley wires.  In those cities, the probability of a hazardous event occurring on a system that is working within design specifications has been assessed as “4C,” based on US Department of Transportation Federal Transit Administration Office of Safety and Security rating on mil-std-882D, using standard hazard assessment evaluation techniques>  The 4C rating states that in terms of both vehicle and system, a trolley wire related CNG bus hazardous event may occur at some time in the life of an individual bus, and may occur several times in the life of the electric trolley wire system.  However, the hazard severity would be negligible, with less than minor injury, less than minor system damage, and less than minor environmental damage.  A San Francisco specific evaluation by proper outside authorities is recommended.

[87] Kerry Witt, Golden Gate Bridge Manager (415-921-5858)

[88] Richard Olander, Superintendent of Maintenance for the Bay Bridge (510-286-6956)

[89] On 4rd Street near King Street

[90] On 3rd Street near Cesar Chavez Street

[91] Philip Tellis, Senior Stationary Engineer for the Bureau of Street and Sewer Repair (415-695-2032)

[92] It should be noted that the five (5) CNG powered Presidio “PresidiGo” Shuttles use this tunnel as part of their normal green-line service.  These shuttles are 29-foot, 24 passenger vehicles.  Mark Helmbrecht, Presidio Trust (415-561-5300). http://www.presidiotrust.gov/shuttle/

[93]  Comments made informally in 8/14/2001 email between instructor James Tucci (TSI) and student Marty Mellera (Muni) during a follow up to a Natural Gas Safety Course put on by the Federal Transportation Safety Institute (TSI).

[94]  Gas accumulation under the cupola housing is a concern, so the cupola housing should be vented to prevent gas accumulation and provided with a monitoring system to prevent accumulation from reaching the LFL through the bus procurement specifications.

[95]  These comments are based on an explanation of the “4C” hazard rating referenced in footnote #72.  More frequent cylinder inspection and leak detection monitors in the tank storage bays of the buses should be put in place, particularly if trolley wire relocation or route avoidance are not possible.

[96] San Francisco Fire Department report “Operations of the San Francisco Fire Department Following the Earthquake and Fire of October 17, 1989.”  Frederick F. Postel, Chief of Department.  Compiled and Edited by Dave Fowler, October 17, 1990.

[97] United States Geological Survey report "The Loma Prieta Earthquake of October 17, 1989."

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