Alternative Fuel Transit Buses

8/8/2019 Alternative Fuel Transit Buses

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DARTs LNG Bus FleetDARTs LNG Bus FleetFinal ResultsFinal Results

Transit BusesAlternative

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Alternative Fuel Transit Bus Evaluation

by

Kevin Chandler, BattellePaul Norton, National Renewable Energy LaboratoryNigel Clark, West Virginia University

October 2000

The authors wish to acknowledge the help and cooperation of the staff,in particular Rocky Rogers and Darryl Spencer, at the host site, DallasArea Rapid Transit. The authors also acknowledge the editorial contri-butions of Vincent Brown at Battelle and Stefanie Woodward at NREL.

World Wide Web: http://www.afdc.doe.govNational Alternative Fuels Hotline: 1-800-423-1DOE

DALLAS AREA RAPID TRANSITS(DART) LNG BUS FLEET:

Final Results


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Notice

This report was prepared as an account of work sponsored by an agency ofthe United States government. Neither the United States government nor anyagency thereof, nor any of their employees, makes any warranty, express or

implied, or assumes any legal liability or responsibility for the accuracy, com-pleteness, or usefulness of any information, apparatus, product, or processdisclosed, or represents that its use would not infringe privately ownedrights. Reference herein to any specific commercial product, process, or ser-vice by trade name, trademark, manufacturer, or otherwise does not neces-sarily constitute or imply its endorsement, recommendation, or favoring bythe United States government or any agency thereof. The views and opinionsof authors expressed herein do not necessarily state or reflect those of theUnited States government or any agency thereof.

Available electronically at http://www.doe.gov/bridge

Available for a processing fee to U.S. Department of Energyand its contractors, in paper, from:

U.S. Department of EnergyOffice of Scientific and Technical InformationP.O. Box 62Oak Ridge, TN 37831-0062phone: 865.576.8401fax: 865.576.5728email: [email protected]

Available for sale to the public, in paper, from:

U.S. Department of CommerceNational Technical Information Service5285 Port Royal RoadSpringfield, VA 22161phone: 800.553.6847fax: 703.605.6900email: [email protected] ordering: http://www.ntis.gov/ordering.ht


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Executive Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .v

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

Alternative Fuel Projects at DOE and NREL . . . . . . . . . . . . . . . . . . . . . .2The Transit Bus Evaluation Project . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

Host Site Profile: Dallas Area Rapid Transit . . . . . . . . . . . . . . . . . . . . . .2

DARTs LNG Buses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

DARTs Involvement in Air Quality Improvement . . . . . . . . . . . . . . . .5

Project Design and Data Collection . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

DARTs Facilities and Bulk Fuel Storage . . . . . . . . . . . . . . . . . . . . . . . . .7

Project Start-Up at DART . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

LNG Engine Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

Range and Fuel Gauge Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

Other Fueling Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

Evaluation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

Bus Use in Transit Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

Average Speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

Monthly Miles Driven . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

Fuel Economy, Maintenance, and Costs . . . . . . . . . . . . . . . . . . . . . . . .14

Fuel Economy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

Fuel Cost per Gallon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

Fuel Cost per Mile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

Engine Oil Consumption and Cost . . . . . . . . . . . . . . . . . . . . . . . . . . .15Factors Affecting Maintenance Costs . . . . . . . . . . . . . . . . . . . . . . . . . .16

Maintenance Costs by Vehicle System . . . . . . . . . . . . . . . . . . . . . . . . .16

Roadcalls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

Warranty Costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

Overall Maintenance Costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

Overall Operating Costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

Emissions Testing Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

LNG Technology Progress in Transit . . . . . . . . . . . . . . . . . . . . . . . . . . .22

Roadcalls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

Maintenance Costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23Fuel Economy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

Emissions Testing Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

Summary and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26

Future LNG Operations at DART . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

Contacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28

References and Related Reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29

Appendix A. Fleet Summary Statistics . . . . . . . . . . . . . . . . . . . . . . . . .31

Appendix B. Emissions Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . .37ii

Table of Contents


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In 1998, Dallas Area Rapid Transit(DART), a public transit agency in Dallas,Texas, began operating a large fleet ofheavy-duty buses powered by liquefied

natural gas (LNG). As part of a $16 mil-lion commitment to alternative fuels,DART operates 139 LNG buses servicedby two new LNG fueling stations.

The U.S. Department of Energy (DOE) Officeof Heavy Vehicle Technologies sponsored aresearch project to collect and analyze dataon the performance and operation costs of15 of DARTs LNG buses in revenue service,compared with the performance of 5 dieselbuses operating on comparable routes.

Objective

The objective of the DOE research project,managed by the National Renewable EnergyLaboratory, was to provide transportationprofessionals with quantitative, unbiasedinformation on the cost, maintenance, oper-ational, and emissions characteristics of LNGas one alternative to conventional dieselfuel for heavy-duty transit bus applications.

In addition, this information should benefitdecision makers by providing a real-worldaccount of the obstacles overcome and thelessons learned in adapting alternativefuel buses to a transit site previouslydesigned for diesel buses. It also identi-fies technology areas where futureresearch and development efforts shouldbe focused. The field study at DART waspart of DOEs ongoing Alternative FuelTransit Bus Evaluation Project.

Methods

Data were gathered daily from fueland maintenance tracking systems formore than 1 year. The data parametersincluded

Fuel consumption

Mileage and dispatching records

Engine oil additions and oil/filterchanges

Preventive maintenance action records

Records of unscheduled maintenance(such as roadcalls) and warranty repairs

The data collection was designed to

cause as little disruption for DART aspossible. The original evaluation fleetsconsisted of 10 LNG buses and 5 similardiesel buses. Five additional LNG buseswere added to the evaluation after thestart-up period.

Results

Some early start-up issues requiredthe LNG buses to operate on restrictedroutes and schedules, but after these

issues were resolved, the LNG anddiesel fleets performed the work DARTexpected during the evaluation period.

The LNG buses emitted less nitrogenoxides and particulate matter than thediesel buses. By most other measures ofoperation, the diesel buses performedbetter than the LNG buses. The LNGbuses had lower energy equivalent fueleconomy, higher fuel costs per mile dri-ven, and higher engine and fuel system

maintenance costs per mile driven thanthe diesel buses.

Overall, the operating cost comparisonwas mixed. The operating costs forthe original LNG buses averaged about3% higher than for the diesel buses.The 10 original LNG buses averaged$0.799 per mile, and the diesel busesaveraged $0.773, giving the dieselbuses an advantage of $0.026 per mile.

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However, the new LNG buses showedthe lowest operating cost per mile,at $0.713about 8% less than thediesel buses.

Lessons LearnedThe LNG bus evaluation project providedDART, DOE, and other participants theopportunity to learn many lessons aboutalternative fuels:

Transit agency employees should learnall they can about potential problemswith alternative fuels in field opera-tions. Agencies should plan for unex-pected contingencies and exercisepatience through the start-up process.

Critical vehicle systems should undergoengineering design validation and/orperformance tests before vehicles areput into service.

Transit agencies need to be committedto success and to invest the personalenergy, infrastructure, and financialresources needed to make alternativefuel programs work.

The LNG industry needs to improve itsown technology support infrastructure,and be able to respond to the needs oflarge fleets of LNG vehicles.

All critical systems need to be inte-grated through strong communicationand accurate information within thetransit agency.

Obstacles Overcome

Early in the deployment of the LNGbuses, DART experienced problems with

operating range, fuel mileage, fuel filling,and reliability. DART also resolved prob-lems with methane sensors, fire suppres-sion systems, electronics, and multiplex-ing systems. (Some of these problemsalso occurred with the diesel fleet.)

Cummins resolved several problemswith early failure of engine components(e.g., turbocharger, spark plugs, and

wastegate). Some engine problems withthe DART LNG buses persisted throughthe end of the study period. Designwork continues on the LNG buses.

The original LNG buses were designedwith a three-tank system that provideda range of only 250 miles in service(277 miles in track tests), well belowDARTs goal of 400 miles. At DARTsrequest, the manufacturer, NovaBUS,added a fourth LNG tank, whichprovided an acceptable range of358 miles in service (380 miles intrack tests).

Other obstacles overcome included

ensuring full tanks at each fueling stop,redesigning the LNG fueling nozzle toprevent leaking, exploring the use of abreakaway hose to prevent damage fromdriveaways during fueling, and a starterlockout switch at the fueling door.

By spring 2000, DART had resolvednearly all the problems with the LNGbuses by applying the lessons learnedfrom start-up and by cooperating withmanufacturers and component suppli-

ers. The LNG buses have operated onall routes (except a few of the longest)originating from the Northwest facility.

Future LNG Operations at DART

DARTs two facilities for fueling andservicing LNG buses have room togrow. New procurements for buseshave a provision for LNG buses. DARTcontinues to evaluate the operation ofits LNG fleet.

DART continues to work on optimizingthe LNG bus operations. DART isworking with Cummins and ZF (thetransmission vendor) to raise the fueleconomy 5%10% by optimizing theshift points of the transmission and byimproving engine component design.DART is also working to optimize theonboard LNG fuel tank system.


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Dallas Area Rapid Transit (DART),a transit agency based in Dallas,Texas, has been operating lique-fied natural gas (LNG) busesfrom its Northwest facility sinceNovember 1998. The LNG busfleet now includes 139 LNGbuses in service. BetweenFebruary 1999 and January 2000,data on DARTs LNG and dieselbuses were collected for evalua-

tion as part of the U.S. Depart-ment of Energy (DOE)/NationalRenewable Energy Laboratory(NREL) Alternative Fuel TransitBus Evaluation Project.

The purpose of this report isto provide transportationprofessionals with summaryinformation on the cost,maintenance, operational,and emissions characteristics

of LNG as one alternative toconventional diesel fuel fortransit bus applications. Thereport should also benefitdecision makers by providinga real-world account of theobstacles overcome and thelessons learned in adaptingalternative fuel buses to a sitepreviously geared towarddiesel buses. It also identifiestechnology areas where future

research and development effortsshould be focused.

This report summarizes theresults of the LNG study at DART.Further technical background,research methods, data, anddetailed discussions are pre-sented in a companion document(DARTs LNG Bus Fleet FinalData Report, NREL, June 2000).

OverviewWhat Is LNG Fuel and How Is It Processed?

Liquefied natural gas is a naturally occurring mixture of hydro-carbons (mainly methane, or CH4), that has been purified andcondensed to liquid form by cooling cryogenically to -260F (-162C).At atmospheric pressure, it occupies only 1/600 the volume of naturalgas in vapor form.

Methane is the simplest molecule of the fossil fuels and can be

burned very cleanly. It has an octane rating of 130 and excellentproperties for spark-ignited internal combustion engines.

Because it must be kept at such cold temperatures, LNG is storedin double-wall, vacuum-insulated pressure vessels. Compared to the

fuel tanks required for using compressed natural gas (CNG) in vehiclesoperating over similar ranges, LNG fuel tanks are smaller and lighter.However, they are larger, heavier, and more expensive than dieselfuel tanks.

Compared to conventional fuels, LNGs flammability is limited. It isnontoxic, odorless, noncorrosive, and noncarcinogenic. It presents

no threat to soil, surface water, or groundwater.

LNG is used primarily for international trade in natural gas and formeeting seasonal demands for natural gas. It is produced mainly atLNG storage locations operated by natural gas suppliers, and at cryo-genic extraction plants in gas-producing states. Only a handful oflarge-scale liquefaction facilities in the United States provide LNGfuel for transportation.

This information was adapted from the following Web sites. Eachoffers further information about LNG:

Natural Gas Vehicle Coalition: http://www.ngvc.org/qa.html

Alternative Fuels Data Center: http://www.afdc.doe.gov

Zeus Development Corp./LNG Express:http://www.lngexpress.com/welcome.htm

CH-IV Cryogenics: http://www.ch-iv.com/lng/lngfact.htm


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Alternative Fuel Projects atDOE and NREL

On behalf of DOE, NREL (a DOEnational laboratory) managed thedata collection, analysis, andreporting activities for the DARTLNG bus evaluation.

NREL and participating companiesacross the United States are evalu-ating several types of alternativefuels. These fuels have includedLNG, compressed natural gas(CNG), biodiesel, ethanol,methanol, and propane (liquefiedpetroleum gas).

One of NRELs missions is toassess the performance and eco-nomics of alternative fuel vehicles(AFVs) objectively so that

Fleet managers can makeinformed decisions when pur-chasing AFVs.

AFVs can be used more widelyand successfully to reduce U.S.consumption of imported petro-

leum and to benefit users andthe environment.

The Transit Bus EvaluationProject

The overall objective of theongoing DOE/NREL AlternativeFuel Transit Bus Evaluation Projectis to compare heavy-duty busesusing an alternative fuel with thoseusing conventional diesel fuel.

Specifically, the program seeks toprovide comprehensive, unbiasedevaluations of the newest genera-tion of alternative fuel engine andvehicle technologies.

Heavy-duty alternative fuel transitbuses have been evaluatedthrough data collection andanalysis since 1993. The transitbus program includes 15 demon-

stration sites and continues toadd new sites for further datacollection and evaluation.

Sites have been selected accord-ing to the kind of alternative fueltechnology in use, the types ofbuses and engines, the availabilityof diesel comparison (control)vehicles, and the transit agencysinterest in using alternative fuels.

After analysis, peer review, andDOE approval, results from eachnew site are published separately.

Host Site Profile: Dallas AreaRapid Transit

The participating host site forthis study was DART, a publictransit agency based in Dallas,Texas. DART operates more

than 1,000 buses, railcars, andvans. Its buses cover more than130 local and express routes ina 700 square mile servicearea that includes Dallas and12 suburban cities.

DART estimates that it servesmore than 200,000 passengersdaily, including rail (seeFigure 1). DART is a leader inbusiness development and

environmental-minded policy,and won the 1997 Transit Agencyof the Year award from theAmerican Public TransportationAssociation.

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Produced for theU.S. DepartmentofEnergy(DOE)

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DARTs LNG Bus FleetDARTs LNG Bus FleetStart-Up ReportStart-Up Report


FuelAlternative

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DARTs LNG Bus FleetDARTs LNG Bus FleetFinal ResultsFinal Results


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Final Results

DARTs LNG BusesDARTs fleet now includes 139 LNGbuses. The first of the 110 LNGbuses ordered from NovaBUS(Roswell, New Mexico) were

delivered to DART in early 1998,and began operating in November1998. Before any buses weredelivered, DART decided toincrease the LNG bus order from40 to 90 during the second yearof the contract and from 20 to 40during the third year.

Because of lower than expectedrange and fuel economy, DARTrequested that NovaBUS add a

fourth LNG tank on each bus toincrease the range of the LNG

3

buses to 380 miles. (The LNGbuses were originally designedwith a three-tank system.) The49 LNG buses already in Dallaswere modified at DART and

NovaBus installed the fourthLNG tank in the 90 LNG busesdelivered after April 1999. Figure 2shows an LNG bus at DART.Figure 3 shows one of the dieselbuses evaluated.

In part because of operatingrange, fuel economy, andother engine-related issues, theDART contract with NovaBUSwas changed in July 1999 so

the last 60 LNG buses (of the200 ordered) would be diesel.

Figure 1. DART bus and rail operations in Dallas,Texas

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the addition of the fourth LNGtank on each bus, and severalmodifications to the fuel gaugesonboard the buses and to LNGstation operating procedures, the

range problem was resolved bySeptember 1999.

As shown in Table 1, the10 alternative fuel buses originallyplanned for evaluation in thisstudy were model year 1998NovaBUS RTS-style busesequipped with CumminsL10-280G engines. The 5 dieselbuses used for comparison werealso model year 1998 NovaBUS

RTS-style buses, but they usedCummins M11-280 engines.The comparison of engines wasdeemed acceptable based onthe similar maximum torque andhorsepower of these models andon previous discussions withCummins. Drivers reported nodriving differences between theDART fleet NovaBUS LNG andthe diesel buses.

The diesel buses in the evalua-tion started operating in May1998. The LNG and diesel buseswere used to transport passen-gers along all routes served byDARTs Northwest facility.

To better understand fuel econ-omy and optimized operationof the LNG buses, 5 more LNGbuses were added to the evalua-tion. These buses had design

enhancements to improveoperating range and were placedinto service in June 1999.(Throughout this report, theoriginal 10 LNG buses will bereferred to as the original LNGbuses; the additional 5 buseswill be referred to as the newLNG buses.)

Thus, 140 LNG buses wereplanned in the final order. DARTneeded more time to resolveproblems before adding moreLNG buses to the fleet. DART

has had great success with theprogram infrastructure, but themobile side of the operations wasdisappointing in the beginning.

DART never accepted the firstLNG bus in the order (the pilotbus) because it needed designchanges. The LNG fleet at DARTthus stood at 139 buses. With

Figure 2. DART LNG bus on the road in Dallas, Texas

Figure 3. One of DARTs diesel buses

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Unless otherwise noted, all data forLNG buses in this report are from

the original set of 10 LNG buses.

The LNG buses cost about$40,000 more than the dieselbuses DART ordered at the sametime. The LNG buses costapproximately $330,000 each(including the fourth LNG tank);the diesel buses cost about$290,000 each.

DARTs Involvement in Air

Quality ImprovementDARTs LNG program planningfor fueling and bus orderingbegan in 1995. Two LNG fuelingstations were planned, one atNorthwest and one at South OakCliff. The LNG fueling station atNorthwest was completed in1998 (with modifications in1999 to optimize automaticcontrols), and the station at

South Oak Cliff was completed in1999 and started operating in

early 2000. Overall, DART in-vested approximately $16 millionbetween 1995 and 2000 for LNGbuses and facilities.

DART has a long-standing com-mitment to environmentalimprovement. In addition tothe 139 LNG buses, DART oper-ates 2 CNG buses, 20 CNG trol-leys, 200 CNG paratransit vans,and 148 CNG automobiles and

trucks. Overall, 41% of DARTsmotor fuel fleet is powered bynatural gas.

Project Design andData Collection

Data were gathered from DARTsfuel and maintenance trackingsystems daily. The data parame-ters included

Table 1. Vehicle Descriptions for DART Evaluation Buses

Description Diesel Control LNG

Number of Buses 5 10 original, 5 new

Chassis Manufacturer/Model NovaBUS, 40 foot NovaBUS, 40 footChassis Model Year 1998 1998, 1999

Engine Manufacturer/ Cummins M11-280, 1998 Cummins L10-280G, 1998

Model, Year

Engine Ratings 280 hp @ 2000 rpm 280 hp @ 2100 rpm

Max. Horsepower 900 lb-ft @ 1200 rpm 900 lb-ft @ 1300 rpm

Max. Torque

Fuel System 125 gallons 4 LNG MVE, Inc. tanks,

Storage Capacity 221 LNG gallons (132

diesel equivalent gallons)

Transmission ZF 5HP590 ZF 5HP590

Manufacturer/Model

Catalytic Converter Used (Y/N) Yes Yes

Curb Weight (lbs) 28,740 30,920

Gross Vehicle Weight (GVW) 39,500 39,500


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Diesel fuel consumption byvehicle and fill

LNG fuel consumption byvehicle and fill

Mileage data from each vehicle Dispatching logs

Engine oil additions and oil/filter changes

Preventive maintenance action(PMA) work orders, parts lists,labor records, and relateddocuments

Records of unscheduledmaintenance (e.g., roadcalls

[RCs]) Records of repairs covered by

manufacturer warranty

The data collection was designedto cause as little disruption forDART as possible. Data were sentfrom the transit site to an NRELcontractor for analysis. DARTgenerally sent copies (electronicand/or paper) of data that hadalready been collected as part ofnormal business operations.

DART staff had access to all databeing collected from their siteand other data available fromthe project. Summaries of thedata collected, evaluations, and

analyses were distributed to des-ignated staff at DART for reviewand input.

The study design included thetracking of safety incidents affect-ing the vehicles or occurring atDARTs fueling station or in themaintenance facilities. However,no such incidents were reportedduring the data collection period.


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the dispensers in the fuelinglanes. The Northwest LNG fuelingfacility was designed to service amaximum of 210 LNG busesnightly. Figure 7 shows thestation receiving bulk fuel froma Lone Star Energy tanker truck.

The station has a cooldowncycle that is required before LNG

fueling. This cycle consists ofrecirculating the LNG in thepiping from the fuel storagetanks to the dispensers (about300 feet of piping) and the hoseat the dispenser (about 65 feetper dispenser).

The cooldown cycle can take1230 minutes. The operation ofthe LNG fueling station is con-trolled from a computer at theshift managers station in themaintenance shop. The LNGbuses are cleaned and fueled atthe same islands as the dieselbuses (three lanes and three setsof dispensers).

The fueling process at DARTbegins when the bus enters thefueling island. Each bus isequipped with an electronichubodometer that communicatesdirectly with the Fleetwatchtracking system at the fuelingisland. The Fleetwatch systemelectronically records the typeand amount of fuel, engine oil,and other fluids added to thebus. The data are periodically

uploaded to the DART networkcomputer system. Once fuelinghas begun at the Northweststation, LNG can be pumpedat 50 gpm onboard the buses(see Figure 8).

A sister LNG fueling station atDARTs South Oak Cliff facilitywas also installed by Lone StarEnergy Company. It has two20,000-gallon tanks, threepumps, and three dispensers.

The station was constructed afterthe Northwest station, and thedesign was modified to incorpo-rate lessons learned.

The cost for the two LNG stationsand the maintenance facilitymodifications at Northwest andSouth Oak Cliff was about $7.5million for design, construction,and start-up.

CourtesyofKe

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Figure 5. LNG fueling station at Northwest as seen from the street

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Figure 6. Northwest fueling station, showing canopy where fuel lines run fromtank to fueling lanes

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Figure 7. DART fueling station receiving bulk LNG from supply

Figure 8. LNG fueling hosesconnected to DART bus

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What Is a Diesel Equivalent Gallon?

Because LNG contains less energy per gallon than diesel fuel, compar-ing simple miles per gallons of LNG and diesel trucks would not accu-rately compare their true fuel efficiencies. Diesel equivalent gallons

are commonly used to solve this problem. A diesel equivalent gallonis the quantity of LNG (or any other fuel) that contains the sameenergy as a gallon of diesel fuel. Because 1.67 gallons of LNG containthe same energy as 1 gallon of diesel fuel, 1.67 gallons of LNG are1 diesel equivalent gallon.

1 gallonof diesel

1.67 gallonsof LNG

has thesame

energy as

Alternative Fue

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Final Results

9

The first LNG bus was deliveredto DART in January 1998, andbegan limited operations in theDallas region. The LNG programofficially started in November1998, when the first LNG busesbegan in revenue service. Earlyin the deployment of the LNGbuses, however, DART experi-enced problems with operatingrange, fuel mileage, fuel filling,

and reliability. These problemswere partly related to the largesize of DARTs LNG fleet and thecapacity of the LNG industry torespond quickly to problems inthe field. In addition to engine-and fuel-related issues, DARTresolved problems with methanesensors, fire suppression systems,electronics, and multiplexingsystems. (Some of the sameproblems also occurred with

the diesel fleet.)

By spring 2000, DART hadresolved nearly all the problemswith the LNG buses by applyingthe lessons learned from start-up and by cooperating withmanufacturers and componentsuppliers. The LNG buseshave been operating with norestrictions on all routes at theNorthwest facility, except for a

few of the longest routes.

LNG Engine Issues

Cummins resolved several prob-lems with early failure of enginecomponents (e.g., turbocharger,spark plugs, and wastegate.)Some engine problems with theDART LNG buses persistedthrough the end of the studyperiod. Cummins is addressing

issues with spark plugs andwires, cylinder head design, theturbo actuator, coils, valves, andthe wastegate. Design work con-tinues to optimize the powertrain and increase fuel economyon the LNG buses.

Range and Fuel Gauge Issues

DART dispatches most buses

on two runs during a standardoperating day, with no middayrefueling. When the LNG busesfirst began to operate, the rangewas significantly lower than therequired 400 miles. The expectedfuel economy for the LNG buseswas approximately 2.2 mpg. Inservice for DART, the LNG buseshad a fuel economy of approxi-mately 1.6 mpg, which is in line

Project Start-Up at DART


17/47

Alternative Fuel

Transit Buses

Final Results

10

with the industry average forLNG buses operating in arough transit duty cycle (i.e.,nearly 50% idle time and verylow average speed).

The LNG buses were originallydesigned with a three-tanksystem that provided 154 usableLNG gallons. At 1.62 mpg,this provided a range of only250 miles in service (277 milesin track tests). In July 1999, DARTasked NovaBUS to add a fourthLNG tank, which made the totalusable LNG capacity 221 gallons.This gave the LNG buses a rangeof 358 miles in service (380 miles

in track tests), which has beenacceptable for DARTs service.

The desire to maximize rangerequired ensuring a full fillof LNG onboard the buses.Originally, the fuel level indicatorcould show nearly full when onefuel tank was nearly empty. Thissituation occurred when one

LNG tank had higher pressure(higher resistance to having LNGflow in) or was hotter than theother tanks. This would cause theother tanks to fill first and the

fuel nozzle would occasionallyshut down automatically becauseof back pressure before filling thehigher pressure tank.

To ensure all tanks were filledwith fuel, a level indicator andpressure indicator for each tankwere installed at the fuel fill loca-tion on each bus (Figure 9). Thefueler can thus easily see whethera tank is not filled completelyand can restart the fueling

process. As a last resort, the fuel-er can start the vent filling proce-dure by manually opening thevent valve for each tank that isnot full. Because each vent valveis on the end of a tank, the fuelermay have to crawl under the busto open and close the valve. Thisadds 10 to 15 minutes to thefueling process.

Other Fueling Issues

The nozzle used for transferringLNG into the bus sometimesleaked and needed to be rebuilt.Leaking causes ice to form on thenozzle, which makes connectingand disconnecting the nozzle dif-ficult, and damages the seal onthe nozzle. The nozzle wasredesigned by the vendor, J.C.Carter, and by the end of datacollection seemed to work better.

Another fueling issue has beenthe need for a breakaway fuelinghose to prevent damage and fuelloss when the bus is driven awayfrom the fuel station while theLNG hose is still connected.This occurred five times at theNorthwest station, causing signifi-cant damage to the dispenser.One possible solution is to add abreakaway fitting (standard

Figure 9. Fuel level and pressure indicators on LNG buses at DART

CourtesyofDART/PIX

091

80


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Alternative Fue

Transit Buses

Final Results

11

Lessons Learned at Start-Up*

Transit agency employees should learn all they can about thealternative fuel being introduced, the vehicles involved in the

project, and potential problems with alternative fuels in fieldoperations. Agencies should do extensive advance planning,

including planning for unexpected contingencies, and exercisepatience through the start-up process.

Critical vehicle systems should undergo engineering designvalidation and/or performance tests before vehicles are putinto service.

Transit agencies need to be committed to success and to invest

the personal energy, infrastructure, and financial resources tomake alternative fuel programs work.

The LNG industry needs to improve its own technology supportinfrastructure, and be able to respond to the needs of largefleets of LNG vehicles. The support required for 100-plus LNG

vehicles in revenue service is far greater than the supportrequired for a few or a dozen in a demonstration project.

All critical systems, including engines, onboard andstationary fuel equipment, chassis, and day-to-dayoperations, need to be integrated through the use of

strong communication and accurate informationwithin the transit agency.

35thSt.

Craig

Ave

.

AltBlvd.

NT

Y

A

U

EOF

ENERG

DEP

ARTM

E

NITEDSTAT

SOFAER

IC

MProducedforthe

U.S.DepartmentofEnergy(DOE)

bytheNationalRenewable

EnergyLaboratory(NREL),

aU.S.DOEnationallaboratory

Colu

cciPkwy.

DARTsLNGBusFleet

DARTsLNGBusFleetFinalResults

FinalResults

TransitBuses

AlternativeFuel

AlternativeFuel

equipment in CNG, diesel, andgasoline fueling systems) to thehose. Another option is to addan electrical circuit to disablethe starter on the bus when the

fueling door is open.

*A report that focuses on DARTs start-up experi-

ence is available from the National Alternative

Fuels Hotline (1-800-423-1363) or on the World

Wide Web (http://www.afdc.doe.gov).


19/47

Alternative Fuel

Transit Buses

Final Results

12

however, showed the lowestoperating cost per mile, at$0.713about 8% lower thanthe diesel buses.

Bus Use in Transit Service

The buses and data collectionperiods used in this study areshown in Table 2.

The fuel and maintenance datafor all vehicles were collectedbetween the start of service andJanuary 2000. The analyses andevaluation in this report focus ononly the data periods shown inTable 2. The maintenance dataperiods were chosen to matchsimilar vehicle lifetimes for thediesel and LNG buses. Thevehicle lifetimes began after the

first PMA and then run for about1 year of service (except for thenew LNG buses, which ran for7 months). This was done torepresent the same operationaltime frame for each fleetbeing evaluated.

The diesel and LNG buses atDART are used 6 days a week,12 or more hours a day. Somebuses also run on Sunday. Early

By the end of the evaluationperiod, both the LNG and thediesel fleets were doing thework DART expected. The majordifference in operations was thatearly on, the period of restrictedoperation for the LNG busesmeant that the diesel buses wereoperated for more miles than theLNG buses.

The LNG buses emitted lessnitrogen oxides and particulatematter than the diesel buses. Bymost other measures of opera-tion, the diesel buses performedbetter than the LNG buses. TheLNG buses had a lower energyequivalent fuel economy, higherfuel costs per mile driven, andhigher engine and fuel systemmaintenance costs per mile

driven than the diesel buses.

Overall, the operating cost com-parison was mixed. The operat-ing costs for the original LNGbuses averaged about 3% higherthan for the diesel buses. TheLNG buses averaged $0.799 permile. The diesel buses averaged$0.773 per mile, giving the dieselbuses an advantage of $0.026per mile. The new LNG buses,

Evaluation Results

Table 2. Evaluation Vehicles and Data Evaluation Periods

Bus Fleet Bus Numbers Start of Fuel Data Maintenance

Service Period Data Period

Diesel 42204224 May 1998 Feb 99Jan 00 Jun 98Jun 99

Original LNG 43204329 Nov 1998 Feb 99Jan 00 Jan 99Jan 00

New LNG 4502, 4513, 4535, 4536, 4539 Jun 1999 Jun 99Jan 00 Jun 99Jan 00


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Alternative Fue

Transit Buses

Final Results

13

during the start of operationof the LNG buses, the reducedrange caused the LNG buses tobe used on only a few routesduring the week and not much

on the weekends. Once therange problems were resolvedwith the fourth LNG tank andoptimization of the LNG system,all the LNG buses could be usedin the same way the diesel buseswere used. Once the rangerestriction was lifted, all buseswere randomly dispatched onone or two routes. Only a few ofthe longest routes were restrictedto diesel buses.

Average Speed

Because the LNG buses hadshorter range in the beginning,they were restricted from someof the routes. Therefore, theiraverage speed was slightly higher(14.4 mph), compared to theaverage speed for the dieselbuses (13.7 mph). Once thefourth LNG tank was installed

and optimized, the LNG buseswere operated on all routes fromthe Northwest facility, except asmentioned. With the increasedrange, the LNG and diesel bueshad the same average speed.

Monthly Miles Driven

The LNG buses traveled as muchas 34% fewer miles each monththan the diesel buses during the

period of restricted operation.Figure 10 shows the monthlyaverage mileage per bus foreach fleet during the evaluationperiod (February 1999 throughJanuary 2000). Figure 11 showsthe monthly average miles perbus. The diesel buses averaged4,321 monthly miles per busand the original LNG busesaveraged 3,232 monthly miles

x

x x xx x

x

Figure 10. Monthly average mileage per bus

Feb-99

0

1000

2000

3000

4000

5000

6000

Mar-99 Apr-99 May-99 Jun-99 Jul-99 Aug-99 Sep-99 Oct-99 Nov-99 Dec-99 Jan-00

New LNGDiesel LNG x

4320

4321

4322

4323

4324

4325

4326

4327

4328

4329

AVG

4502

4513

4535

4536

4539

AVG

4220

4221

4222

4223

4224

AVG

DieselOriginal LNG New LNG

Average monthly miles driven

OriginalLNG

NewL

NG

Diesel

0 1000 2000 3000 4000 5000

Figure 11. Average monthly miles driven per bus


21/47

Alternative Fuel

Transit Buses

Final Results

14

per bus, 25% lower during theevaluation period. The new LNGbuses had the fourth LNG tankand full range since starting oper-ation in June 1999; hence, their

average monthly miles per busare in line with those of thediesel buses at 4,486 miles. Theoriginal LNG buses had a lowerrange than the diesel buses andsaw lower vehicle usage untilSeptember 1999 when the fourthLNG tank was installed. After Sep-tember 1999, the original LNGbus monthly mileage quicklyincreased to the level of thediesel buses.

Fuel Economy, Maintenance,and Costs

The LNG buses used more fuelper mile, so even though theLNG fuel cost was lower (on anenergy equivalent basis) than thecomparable diesel fuel, fuel costfor DART was 32% more per milefor the LNG buses than for thediesel buses in the evaluation.

Fuel Economy

Figure 12 shows the fueleconomy for the diesel, originalLNG, and new LNG buses. Adiesel equivalent gallon is thequantity of LNG that containsthe same energy as 1 gallon ofdiesel fuel. Diesel equivalentgallons have been calculatedbased on a standard LNG gallon

divided by 1.67, the conversionfactor for pure methane. LNG atthis site is essentially all methane(at least 98%, as required bycontract), according to the fuelsupplier, Lone Star Energy.

On average, the LNG bus fueleconomy was 28% lower than thediesel bus fuel economy on adiesel equivalent gallon basis.

4320

4321

4322

4323

4324

4325

4326

4327

4328

4329

AVG

4502

4513

4535

4536

4539

AVG

4220

4221

4222

4223

4224

AVG

Miles per diesel gallon

Miles per LNG gallon

Miles per dieselequivalent gallon

Miles per gallon

Diesel equivalent gallons were calculated based ona standard LNG gallon and divided by 1.67 (theconversion factor for pure methane). The LNG usedduring the evaluation was confirmed by DARTsfuel supplier to be essentially pure methane.See sidebar page 9.

OriginalLNG

NewL

NG

Diesel

0 1 2 3 4

Figure 12. Fuel economy


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Alternative Fue

Transit Buses

Final Results

15

Based on past experience withnatural gas vehicles in heavy-duty transit operation, the fueleconomy difference is within theexpected range of 15% to 30%

lower. The newer LNG buseswith four LNG tanks had thesame average fuel economy asthe evaluation LNG buses.

Fuel economy measurementsmade at DART as part of theemissions testing on a chassisdynamometer (described in detailin Appendix H ofDARTs LNGBus Fleet Final Data Report,June 2000) show average LNG

bus fuel economy of 14% lowerthan the average diesel bus fueleconomy on an energy equivalentbasis over the Central BusinessDistrict (CBD) driving cycle. Thisis substantially better than the28% difference seen in actualoperation.

The driving cycle for the buseshas been different in servicethan that tested by West Virginia

University (WVU) for emissions.Also, air conditioning was notrunning during the WVU testingand there was little idle timeduring the emissions testing. Inservice, the diesel and LNG busestypically spend 50% or more ofthe time idling with their air con-ditioning running. The naturalgas engines are spark-ignited andhave higher fuel consumption atidle/low speed than the diesel(compression-ignition) engines.

Fuel Cost per Gallon

Diesel fuel costs rose significantlyduring 1999, from $0.70 (February1999) to $1.09 per gallon inJanuary 2000. The average dieselfuel cost used for the evaluationwas $0.90 per gallon. The averagecost for LNG fuel used for the

evaluation was $0.49 per LNGgallon ($0.82 per diesel equiva-lent gallon).

Fuel Cost per Mile

Fuel consumption cost for theLNG buses was 32% higherthan for the diesel busesLNGwas $0.314 per mile and dieselwas $0.238 per mile. The fuelcosts, coupled with the differencein energy equivalent fuel econ-omies, make up the fuel cost permile. Fuel costs in the future fordiesel and LNG could be differentthan the average fuel costs used

in this evaluation, depending onchanging fuel prices and changesin LNG vehicle fuel efficiency.

Engine Oil Consumptionand Cost

The DART LNG buses consumed2.03 quarts of engine oil per1,000 miles; the diesel busesconsumed 18% less (1.72 quartsper 1,000 miles).

Engine oil cost for the LNGengines was 31% higher perquart than for the dieselengines$0.85 per quart forthe LNG engines and $0.65 perquart for the diesel engines.The higher cost oil for the LNGengines is due to the low ashcontent specified by Cumminsand the low volume purchaseof this oil by DART.

The oil cost per 1,000 miles forthe diesel engines was $1; for theLNG engines it was $2. However,per-mile engine oil consumptioncosts were very low compared tofuel and maintenance costs.


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Alternative Fuel

Transit Buses

Final Results

16

Factors Affecting MaintenanceCosts

Maintenance costs for theDART evaluation were affectedby several unusual factors, most

notably that the NovaBUS vehi-cles were the first new busespurchased by DART in morethan 10 years, and the first DARTever ordered from that manufac-turer. Thus, the maintenancestaff had to adapt to a numberof new technologies in thediesel and LNG buses. Newsystems such as multiplexing ofcontrols onboard the bus(instead of using hard wiring),computer-controlled engine andtransmission technologies (bothnew to DART), antilock brakesystems, and a new axle modelwere some of the systems DARTengineers and maintenance staffhad to learn and troubleshoot ina short time (see Figure 13).Added to these technologies andprocedures were the LNG fuelsystems, which were new to

DARTs transit bus operation.

Phasing the arrival of the newbuses also affected maintenancecost values. The diesel buseswere put into service 6 monthsbefore the LNG buses. Therefore,

the troubleshooting and adjust-ments for the diesel busesoccurred earlier on the learningcurve for the DART staff. Issuesthat were resolved with NovaBUSand component suppliers duringthe first months of diesel busoperation resulted in lowermaintenance costs for the LNGbuses, because the changes hadalready been put in place, orbecause the time required to

make adjustments was reduced.Similarly, the cost for trouble-shooting the 5 new LNGbuses was lower than for theoriginal 10.

Maintenance Costs by VehicleSystem

Figure 14 shows the relativeshare of the major systems con-tributing to maintenance costs.

The portion of the maintenancecosts for engine- and fuel-relatedsystems was 8% higher for theLNG buses than for the dieselbuses.

The top four categories rankedby cost are the same for thediesel, original LNG, and newLNG buses:

1.Cab, body, and accessories

(includes body repairs, repairsfollowing accidents, glass,painting, cab and sheet metalrepairs, seats, accessory repairs(such as radios), farebox, andhubodometer)

2.Engine- and fuel-related(includes exhaust, fuel, engine,non-lighting electrical, airintake, and cooling repairs)

Figure 13. DART maintenance staff inspecting LNG fuel system

CourtesyofDART/PIX

09176


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Alternative Fue

Transit Buses

Final Results

17

3.PMA inspection (includes onlylabor for inspections duringpreventive maintenance)

4.Brakes

The diesel bus maintenance costswere higher than expected forsystems unrelated to the engine-and fuel-related systems. Onlythe engine- and fuel-relatedsystems would be expected toshow differences between theLNG and diesel buses. In thiscase, several systems unrelatedto the drivetrain requiredsignificant maintenance for thediesel buses. In the followingdiscussion, only the per-mileresults from the similar vehiclelifetimes are covered.

Brief summaries of the differ-ences seen between the dieseland LNG fleets, and some of theircauses, are as follows:

Cab, body, and accessories sys-tems Diesel bus maintenancecosts were about 17% higher

because of problems withaccessories such as surveillanceequipment.

Engine- and fuel-related sys-tems The original LNG buseshad maintenance costs 33%higher than the diesel buses;the new LNG buses 10%. Thenew LNG buses had a lowermaintenance cost differencethan the original LNG buses

because of lower labor costs fortroubleshooting.

Exhaust system The mainte-nance costs were 59% lower forthe original LNG buses and80% lower for the new LNGbuses than for the diesel buses.

Fuel system The LNG mainte-nance costs were much higherthan the diesel buses (3 times

higher for the original LNGbuses and 2.4 times higherfor the new LNG buses). MostLNG bus maintenance for thefuel system was for labor to

troubleshoot problems such aslow power and fuel leaks.

Engine system Costs wereabout 40% higher for the origi-nal LNG buses and 3% lowerfor the new LNG buses.

Non-lighting electrical sys-tems Costs were 39% higherfor the original LNG buses and56% higher for the new LNGbuses. The parts and labor

costs were higher. Most partscosts for the original LNGbuses were due to spark plugsand wires changed as part ofpreventive maintenance.

Air intake system The costswere low and nearly the samefor the diesel and the originalLNG buses. For the new LNGbuses, the cost was about halfthat of the diesel buses.

Cooling system The costswere nearly the same for the

diesel and the original LNGbuses. For the new LNG buses,the cost was about half that of

the diesel buses.

PMA inspections As expected,

costs were essentially the same

for the study fleets. There

should be no extra costs for

inspections on any of the study

fleets, because the vehicleswere in approximately the

same service.

Brake system Both study

fleets of LNG buses had about

the same costs for brake

system maintenance. The

diesel buses required more

labor to troubleshoot the

antilock brake systems.

Cab, Body,Accessories

38%

Brakes11%

Diesel

PMA13%

Engine, Fuel17%

All Other Maintenance21%


40%Brakes8%

New LNG

PMA16%

Engine, Fuel25%

All OtherMaintenance

11%


35%

Brakes7%

Original LNG

PMA14%

Engine, Fuel25%

All OtherMaintenance

19%

Figure 14. Share of maintenance cosacross major systems


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Alternative Fuel

Transit Buses

Final Results

18

Lighting system The mainte-nance costs were about 34%lower for the original LNGbuses and 70% lower for thenew LNG buses than for the

diesel buses. Tire systems All tire costs

were covered under a leasearrangement, with a consistentcost of $0.0051 per mile fortire replacements.

Transmission The mainte-nance costs were about 73%higher for the original LNGbuses and 55% lower for thenew LNG buses than for the

diesel buses. The originalLNG buses had higher costsbecause of higher parts costsand occasional unscheduledmaintenance.

HVAC systems The originalLNG buses had maintenancecosts 12% lower than thediesel buses; the new LNGbuses 76% lower. The dieseland original LNG buses

required significant labor hoursfor troubleshooting problemswith the air conditioningmotors and problems that weremostly covered under warranty.

Air system Most repairs forthe air system are assigned tothe brakes, door, and suspen-sion systems. These were lowoverall but slightly higher forthe diesel buses.

Frame, steering, and suspen-sion systems The diesel busmaintenance costs were nearlydouble those for the LNGbuses. These higher costswere caused mostly by bumpermodule replacements due tominor accidents and labor forproblems with radius rodreplacements covered bythe warranty.

Axle, wheel, and drive shaftsystems Maintenance costsfor the study buses were low.

Roadcalls

An RC is defined in this reportas an on-road failure of an in-service transit bus that requires areplacement bus to be dispatchedto complete the route. If the failedbus is fixed on the road and putback into service immediately, thisis not considered an RC.

Figure 15 shows average milesbetween RCs for the diesel and

LNG buses for all data. Thischart shows that the trend foreach study fleet is upward andindicates the progress DART hasmade toward troubleshootingand resolving start-up problems.

The low miles between RCs forthe diesel buses were caused bysystems other than the engine-and fuel-related systems, and theLNG buses have had many more

engine- and fuel-related issues. Forengine- and fuel-related systems,both sets of LNG buses had milesbetween RC results that were50% lower than the diesel buses.

Warranty Costs

On a cost per bus basis across alldata collected, the diesel buseshad the highest costs for warrantyrepairs ($17,101.54). The per-bus

costs were lower for the originalLNG buses, at $10,660.65. Thenew LNG buses had the lowestper-bus costs, at $8,674.57.

This trend is consistent withDART and NovaBUS workingthrough the maintenance prob-lems of the buses as they arrived.In this analysis the diesel buseswere put into service 6 months


26/47

Alternative Fue

Transit Buses

Final Results

19

before the first LNG buses and ayear before the new LNG buses.

The highest warranty costsystems for each fleet were asfollows:

Diesel body, cab, accessories;HVAC; non-lighting electrical;axles, wheels, drive shaft;and frame, steering, andsuspension

Original LNG engine/fuel-related; body, cab, accessories;non-lighting electrical; HVAC;fuel; and axles, wheels, anddrive shaft

New LNG body, cab, acces-sories; non-lighting electrical;exhaust; and engine/fuel related

Overall Maintenance Costs

The following analysis coverstotal maintenance costs forsimilar vehicle lifetime periodswith no warranty work included.Similar vehicle lifetimes werechosen to represent the period

beginning after the first PMA andrunning for about 1 year. Focus-ing on only the similar vehiclelifetime results, the vehicle usagehas been 17% higher for thediesel buses.

Figure 16 shows the total mainte-nance costs per bus across theoriginal LNG, new LNG, anddiesel fleets evaluated. Theoriginal LNG buses showed

significantly lower parts costsper bus than the diesel buses.The labor hours were also lowerfor the original LNG buses.(Labor costs were calculatedusing a constant average rate of$50 per hour.)

The original LNG buses had atotal maintenance cost per mile9% lower than the diesel buses.

x

xx x x x

xx x

x xx x x

x

New LNG AvgDSL Avg LNG Avg

May-98

0

1000

2000

3000

4000

5000

6000

July-98 Sep-98 Nov-98 Jan-99 Mar-99 May-99 July-99 Sep-99 Nov-99 Jan-00

x

Figure 15. Average miles between RCs for diesel, original LNG,and new LNG buses (does not include out-of-fuel RCs)

This difference was caused bymaintenance of accessorysystems. Engine- and fuel-relatedsystems maintenance costswere significantly higher forthe original LNG buses, as

discussed earlier.

Total maintenance costs per milefor the new LNG buses weremuch lower than for the dieselbuses. These costs were lowerbecause in the accessory systemsmany of the problems with thediesel buses were resolved forthe LNG buses. Also, the preven-tive maintenance costs werelower because the data evalua-

tion period was shorter than thefull year used for the diesel andoriginal LNG bus evaluation.

Overall Operating Costs

Figure 17 provides a summary ofoperating costs for the diesel,original LNG, and new LNGstudy groups of buses. Theseresults are only for the similar


27/47

Alternative Fuel

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Final Results

20

vehicle lifetime data periods.Total operating costs include fueland maintenance costs, andexclude driver labor. Engine oilcosts were low (maximum $0.002

per mile).

Overall, the three fleets analyzed

had very similar operating costs,ranging from a low of $0.713 permile for the new LNG buses to

$0.773 for the diesel buses, and toa high of $0.799 for the originalLNG buses.

This means that the original LNGbuses had operating costs 3%

higher than the diesel buses. Thenew LNG buses had operatingcosts 8% lower than the dieselbuses. The total maintenancecosts were higher for the dieselbuses as explained earlier; how-ever, for the engine- and fuel-related systems, the original LNGbuses had costs 33% higher, andthe new LNG buses had costs10% higher than the diesel buses.

In Calculating the Overall

Operating Costs:

Vehicle and fueling station capi-tal costs and driver labor werenot included

Actual fuel costs during thestudy were used:

Diesel: $0.90 per gallon

LNG: $0.85 per diesel energyequivalent gallon

Maintenance costs did notinclude warranty repairs paidfor by the manufacturers

Maintenance labor cost was

assumed to be $50 per hour

Emissions Testing Results

Emissions tests on the diesel andoriginal LNG buses were con-ducted by the WVU Department ofMechanical and Aerospace Engi-neering using one of its trans-portable heavy-duty chassis dyna-mometer emissions laboratories.(These laboratories were devel-

oped under DOE sponsorship.)WVU used the CBD speed-versus-time cycle to evaluate each bus.

Tests were conducted in Februaryand March 1999. Results areshown in Figure 18. The LNGbuses had less of all four regu-lated emissions than the dieselbuses. The LNG buses were muchlower in carbon monoxide andparticulate matter emissions than

the diesel buses. Although thenitrogen oxide emissions werequite variable, on average, theLNG buses had 17% lowernitrogen oxide emissions thanthe diesel buses. The LNG busesalso had significantly lowernon-methane hydrocarbons thanthe diesel buses (assumed to benon-methane). Both fleets wereequipped with oxidation catalysts.

Avg Milesper Bus


Avg Parts Costper Bus in $

Avg Labor Hoursper Bus

Total MaintenanceCost per Mile in $

80,000

70,000

60,000

50,000

40,000

30,000

20,000

10,000

0

10,000

8,000

6,000

4,000

2,000

0

500

400

300

200

100

0

1.0

0.8

0.6

0.4

0.2

0

Figure 16. Total maintenance costs per bus


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Alternative Fue

Transit Buses

Final Results

21

In general, the diesel buses hadrelatively low emissions resultsbecause oxidation catalysts wereused. However, the LNG busemissions were still significantly

lower than those of the cleandiesel buses.

The average miles per dieselequivalent gallon obtainedduring emissions testing for theLNG buses were much higherthan the result obtained fromin-use fuel economy data. Asdiscussed in the fuel economysection, however, the CBD cycleused in emissions testing differed

from the actual revenue serviceduty cycle for the diesel and LNGbuses. In addition, the CBD cycledoes not take into account peri-ods of idling with auxiliary loadssuch as air conditioning.

Figure 17. Overall operating costs per mile in $

Fuel Costper Mile

Total Costper Mile


MaintenanceCost per Mile

0 0.25 0.50 0.75 1.0

Cost per Mile in $

NOx, g/mi PM x 10, g/mi HC/NHMC x 10, g/mi CO, g/mi CO2/100, g/mi MPEG

30

20

10

0

Diesel

a

Original LNG

a. PM values for LNG were below the detectable limit (


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Alternative Fuel

Transit Buses

Final Results

22

LNG Technology Progress in Transit

LNG transit bus technology wasevaluated in the originalDOE/NREL evaluation reportfrom 1996 (Alternative FuelTransit Buses, Final Results from

the National Renewable Energy

Laboratory Vehicle Evaluation

Program). In this report, LNGtransit buses were studied atHouston Metro (Houston, Texas)and Tri-Met (Portland, Oregon).

One conclusion was that, becausethe LNG technology evaluated atthese sites was considered earlydevelopment equipment, anotherLNG site evaluation was neededto investigate operating costs andreliability on more mature LNGfuel system technology that didnot use a cryogenic pump

onboard the bus. Houston Metroused the Detroit Diesel (DDC)6V92TA PING (pilot injection nat-ural gas) dual-fuel (natural gasand diesel fuel together) enginefor LNG operations. This engineis no longer available from DDC,and Houston Metro has phasedmost of them out. Tri-Met usedthe Cummins L10-240G enginefor LNG operations. This engine

used open loop natural gas fuelsystem technology, and is nolonger available from Cummins.

The LNG technology beingplanned at DART was the newestavailable in the industry usingthe Cummins L10-280G engineand a fuel system from MVE, Inc.

Table 3.Vehicle Descriptions for LNG Evaluation Buses

Description Houston Metro Tri-Met DART

Number of LNG Buses 10 10 10

Chassis Manufacturer/Model Mercedes, 40 foot Flxible, 40 foot Nova Bus, 40 foot

Chassis Model Year 1992 1993 1998, 1999

Engine Manufacturer/Model DDC 6V92TA PING Cummins L10-240G Cummins L10-280G

Engine Ratings

Max. Horsepower 277 hp @ 2100 rpm 240 hp @ 2100 rpm 280 hp @ 2100 rpm

Max. Torque 840 lb-ft @ 1200 rpm 750 lb-ft @ 1300 rpm 900 lb-ft @ 1300 rpm

Fuel System 70 gallons 174 gallons LNG 221 gallons LNG

Storage Capacity 43 gallons diesel

Transmission Allison, HTB-748 Voith, D-863 ADR ZF 5HP590

Manufacturer/Model

Catalytic Converter Used (Y/N) No Yes Yes

Curb Weight (lbs) 30,560 30,030 31,000

Gross Vehicle Weight (GVW) 39,500 39,500 39,500


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Final Results

23

without a cryogenic pump. Boththe engine and the fuel systemhad been used in several vehicleapplications. DART also chose tobuy diesel buses that would

match the LNG technology busesalmost identically, excluding theengine and the fuel system. Thissection investigates how theDART LNG results compare to theearlier technology at HoustonMetro and Tri-Met. Table 3 showsa summary of vehicle descrip-tions for Houston Metro, Tri-Met,and DART LNG buses.

Roadcalls

Figure 19 shows mileage betweenRCs for Houston Metro, Tri-Met,and DART during the evaluationperiod. The first set of barsshows RCs for all systems(including the door, wheelchairlifts, and other features); thesecond set is for the engine-and fuel-related systems (engine,fuel, non-lighting electrical, airintake, and cooling). In the early

LNG fleets at Houston Metro andTri-Met, the diesel buses traveledsignificantly further between RCs.At DART, the distance betweenRCs was essentially the same forthe diesel and the LNG buses.The engine- and fuel-related sys-tems results show that the DARTLNG buses ran a much longerdistance between RCs than theHouston Metro or Tri-Met LNGbuses. However, these systems

resulted in more RCs for LNGthan for diesel at all three sites.

Maintenance Costs

Figure 20 shows total operatingcosts by vehicle group at DART,Tri-Met, and Houston Metro. Forengine- and fuel-related systemsmaintenance (the bottom portionof the stacked bars), costs for the

Houston Metro LNG buses were3.8 times (280%) higher than forthe diesel buses at HoustonMetro. At Tri-Met, engine- andfuel-related maintenance costsfor the LNG buses were 1.6 times(60%) higher than for the diesel

buses. At DART, the engine andfuel-related maintenance costs

Figure 19. Miles between roadcalls

Houston

LNGDiesel

0 2000 4000 8000 100006000 12000 14000 16000 18000 20000

Tri-Met

DART

Houston

Tri-Met

DART

Engine- and Fuel-Related Systems Only

Entire Bus

$0.00

Other Maint.Eng/Fuel Maint.

$0.20

$0.40

$0.60

$0.80

$1.00

$1.20

DART Diesel DART LNG Tri-Met Diesel Tri-Met LNG Houston Diesel Houston LNG

Fuel & Oil

Figure 20. Operational costs per mile ($)


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were only 1.3 times (33%)higher than for the diesel buses.(The maintenance data for allthree sites were calculated witha constant labor rate of $50 per

hour. For the 1996 report, $25per hour was used.) The engine-and fuel-related maintenancecosts for LNG buses were signifi-cantly lower at DART than atHouston Metro or Tri-Met.

The overall maintenance costs atHouston Metro and Tri-Met weresignificantly higher for the LNGbuses than for the diesel controlbuses. At DART, the LNG and

diesel bus maintenance costswere comparable.

Fuel Economy

Figure 21 shows fuel economyresults for Houston Metro,Tri-Met, and DART for the LNGand diesel buses at each site.Houston Metro LNG busesshowed a 13% lower fueleconomy on a diesel equivalent

gallon basis. The Houston MetroLNG buses had the best fueleconomy, but the dual-fuelLNG/diesel buses were not oper-ated in LNG mode often. The

dual-fuel buses could operate ondiesel only, and were rarely usedin the dual-fuel mode. Therewere problems with the dual-fueloperation of the LNG buses atHouston. The Tri-Met LNG buseshad a fuel economy 30% lowerthan the diesel buses at Tri-Met.This result is consistent with theDART LNG buses having a fueleconomy 28% lower than thediesel buses at DART. However,

this is a similar fuel economydifference for an LNG bus witha higher horsepower engine(240 hp at Tri-Met and 280 hpat DART).

Emissions Testing Results

For emissions testing results fromWVUs mobile chassis dynamome-ter, results from early natural gasengines were generally erratic

because of the open loop fuelcontrol design. This was truefor Houston Metro and Tri-MetLNG buses. For the spark-ignitedCummins engine at Tri-Met, theLNG buses showed extremelylow particulate matter results(0.02 to 0.03 g/mi compared tothe diesel buses that averaged1.96 to 2.18 g/mi). Carbondioxide emissions were aboutthe same for the LNG and diesel

buses (2430 g/mi). However,carbon monoxide and nitrogenoxide could be low for the LNGbuses, but could also be veryhigh. On average, the carbonmonoxide results for the LNGbuses were about the same as thediesel buses (10 g/mi), but wereas low as 0.01 g/mi and as high as58.8 g/mi. On average, the older

Houston Metro Tri-Met DART

$0.00

LNGDiesel

$0.50

$1.00

$1.50

$2.00

$2.50

$3.00

$3.50

$4.00

$4.50

Figure 21. Fuel economy results in miles per diesel equivalent gallon


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technology nitrogen oxide resultsfor the LNG buses were about20% higher than the average forthe diesel buses (41 to 45 g/mifor diesel buses), but were as low

as 31 g/mi and as high as 67 g/mi.The wide swings in emissionsresults were attributed to thetune of the engine or improperlyfunctioning fuel control on theLNG buses.

For the DART LNG and dieselbuses on the CBD cycle, theemissions results were muchmore consistent and generallylower for the LNG buses. The

LNG buses at DART had anaverage of 0.23 g/mi for carbonmonoxide, 21.3 g/mi nitrogenoxide, and particulate matterthat was lower than thedetectable limit of WVUsequipment,


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Some engine problemscontinue to cause difficultiesfor the DART LNG buses.Cummins is still working onthese problems even thoughthe L10 engine has been dis-continued as a commercialproduct. The resolution ofproblems with the L10 isapplicable to the C8.3G,Cummins current heavy-dutynatural gas engine for thetransit market. Cummins isaddressing issues with sparkplugs and wires, cylinder headdesign, turbo actuator, coils,and wastegate.

Emissions testing results fromWVU showed that the dieselengines at DART were veryclean. The LNG emissions werecleaner yet. This emissions test-

ing at DART was a state-of-the-art comparison for transit with1998 technology.

Total operating costs for theLNG buses were only 3%higher than the diesel buses.However, the maintenance costsfor the engine- and fuel-relatedsystems were 33% higher for theLNG buses than for the dieselbuses. The fuel costs were 32%

higher for the LNG buses thanfor the diesel buses.

Miles between RCs for the LNGand diesel buses overall wereabout the same. The LNG buseshad 50% fewer miles betweenRCs for the engine- and fuel-related systems compared tothe engine- and fuel-relatedsystem RCs on the diesel buses.

Based on the evaluation of theDART LNG transit buses, we canconclude several major points:

DART has had significantproblems, especially relatedto range, with start-up of LNGoperations. The buses werespecified to have a 400-milerange and could achieve only277 miles. A fourth LNG tank

was added for onboard storageof LNG. This fourth tank pro-vided enough fuel to achieve arange of 380 miles, whichDART deemed acceptable. Sev-eral other problems with earlyfailure of engine components(turbocharger, spark plugs,exhaust valve, and wastegate),fuel system (leaks), the fuelingstation nozzle, and other sys-tems have nearly all been

resolved through a team effortat DART and with the vendors.

As of the end of the studyperiod, the LNG buses werebeing treated the same as thediesel buses in meeting thedaily pullout requirements.

The drivers report that theLNG buses are well matched inperformance to diesel; drivershave difficulty telling the busesapart.

The fuel economy has beensteady at 1.62 miles per LNGgallon or 2.70 miles per dieselequivalent gallon. DART, ZF,and Cummins continue toexplore ways to increase fueleconomy by 5% to 10%.

Summary and Conclusions


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The South Oak Cliff facility willhouse and maintain nearly halfthe current LNG fleet. Fifty LNGbuses were moved to South OakCliff in May 2000, and the newLNG fueling facility there is oper-ational. Both the Northwest andSouth Oak Cliff operations facili-ties have room to increase theirLNG fleets.

New procurements for buses atDART have a provision for LNGbuses. DART continues to evalu-ate the operation of its LNG fleet.

DART continues to work on opti-mizing the LNG bus operations.

One issue for LNG operationsis that DART has invested

Future LNG Operations at DART

The problems with range andthe size of the LNG fleet atDART challenged the LNG andnatural gas vehicle industries.A consortium of industry part-

ners on an LNG task forceovercame the problems. At theend of the study, all 139 LNGbuses were making pulloutnearly every day.

The two LNG fueling stationsare working well for DART.Some problems have beenexperienced with fueling noz-zle leaks and driveaways withdamage to the dispensing sys-tem. The nozzle has beenredesigned and seems to bemanaging leaks better. DART isstill exploring breakaway fittingand hose designs. The newLNG station at South Oak Cliffdoes not have the extensivelength of piping (300 feet)from the storage tanks to thefueling island that Northwesthas. This has resulted in amuch higher available fueling

rate, as high as 70 gpm.

In 1996, DOE/NREL publishedan evaluation report on LNGtransit bus technology thatincluded buses at HoustonMetro and Tri-Met. The technol-

ogy was considered early devel-opment equipment, and thereport concluded that anotherLNG site evaluation was neededto investigate the operatingcosts and reliability on moremature LNG fuel system tech-nology. DART was chosen as thesite because the technologythen being planned there wasthe newest in the industry.

The results of the DART LNGbus evaluation show that emis-sions, reliability, and mainte-nance costs have generallyimproved from earlier LNG busdesigns. The overall reliabilityand maintenance costs werecomparable with diesel; thesesame costs for the engine- andfuel-related systems haveimproved compared with dieseltechnology, but are not yet at

the same level.

$16 million for buses and facilities.The two LNG fueling stations havesignificant capacity left: 139 LNGbuses of a maximum 350 LNGbuses that could be filled nightly,or 40% of capacity. DART has theopportunity to use more of thecapacity of its fuel stations andcontinue to reduce emissions byusing LNG.


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Contacts

DART

Michael HubbellVice President, Maintenance4209 Main StreetDallas, TX 75266-7258214/828-6780

DART

Rocky RogersAssistant Vice PresidentTechnical Services4209 Main StreetDallas, TX 75266-7258214/828-6721

DART

Darryl SpencerFleet Systems EngineerP.O. Box 660163

Dallas, TX 75266-7258214/828-6804

NREL

Paul NortonSenior Engineer1617 Cole BoulevardGolden, CO 80401303/275-4424

BATTELLE

Kevin ChandlerProject Manager505 King AvenueColumbus, OH 43201614/424-5127

LONE STAR ENERGY COMPANY

(Now a part of Blue Fuels)Stanley T. TaylorGeneral Manager300 South St. Paul StreetSuite 750 ECDallas, TX 75201214/875-3854

CUMMINS SOUTHERN PLAINS, INC.

Jason RubleRegional Sales Manager

600 N. Watson RoadP. O. Box 90027Arlington, TX 76004-3027817/640-6896

NOVABUS

Dan MoatsEngineering Project Manager42 Earl Cummings Loop WestP.O. Box 5670 (R.I.A.C.)Roswell, NM 88202-5670

505/347-7350

CHART-APPLIED TECHNOLOGIES

George LauxSenior Account RepresentativeP.O. Box 12066Spring, TX 77391281/890-6228

WEST VIRGINIA UNIVERSITY

Nigel ClarkDepartment of Mechanical &Aerospace EngineeringMorgantown, WV 26506-6106304/293-3111 ext. 2311


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References and Related Reports

Battelle, 2000,DARTs LNG Bus Fleet Final Data Report, National RenewableEnergy Laboratory, Golden, CO.

Battelle, 2000,DARTs LNG Bus Fleet, Start-Up Experience, National RenewableEnergy Laboratory, Golden, CO, NREL/BR-540-28124.

Chandler, K., Norton, P., Clark, N., 2000,Raleys LNG Truck Fleet, FinalResults, National Renewable Energy Laboratory, Golden, CO, NREL/BR-540-27678.

Battelle, 1999, Waste Managements LNG Truck Fleet, Start-Up Experience,National Renewable Energy Laboratory, Golden, CO, NREL/BR-540-26617.

Battelle, 1999,Raleys LNG Truck Site, Final Data Report, Battelle, Columbus,OH.

Chandler, K., Norton, P., Clark, N., 1999, Update from the NREL AlternativeFuel Transit Bus Evaluation Program,American Public Transit Association,1999 Bus Conference, Cleveland, OH.

Chandler, K., Norton, P., Clark, N., 1999,Interim Results from Alternative FuelTruck Evaluation Project, SAE International, Warrendale, PA, SAE Pub. #1999-01-1505.

Clark, N., Lyons, D., Rapp, L., Gautam, M., Wang, W., Norton, P., White, C.,Chandler, K., 1998,Emissions from Trucks and Buses Powered by Cummins

L-10 Natural Gas Engines, SAE International, Warrendale, PA, SAE Pub.#981393.

Battelle, 1998,Dual-Fuel Truck Fleet, Start Up Experience, National RenewableEnergy Laboratory (NREL), Golden, CO, NREL/BR-540-25118.

Battelle, 1998, Using CNG Trucks in National Parks, National RenewableEnergy Laboratory (NREL), Golden, CO, NREL/BR-540-24744.

Chandler, Norton, Clark, 1998,Alternative Fuel Truck Evaluation Project Design and Preliminary Results, SAE International, Warrendale, PA, SAE Pub.#981392.

Norton, P., Vertin, K., Bailey, B., Clark, N., Lyons, D., Goguen, S., Eberhardt, J.,

1998,Emissions from Trucks Using Fischer-Tropsch Diesel Fuel, SAE Interna-tional, Warrendale, PA, SAE Pub. #982426.

Clark, N., Gautam, M., Lyons, D., Bata, R., Wang, W., Norton, P., Chandler, K.,1997,Natural Gas and Diesel Transit Bus Emissions: Review and RecentData, SAE International, Warrendale, PA, SAE Pub. #973203.

Battelle, 1997,Raleys LNG Truck Fleet, Start-Up Experience, NationalRenewable Energy Laboratory, Golden, CO, NREL/BR-540-23402.

Battelle, 1996,Alternative Fuel Transit Buses, The Pierce Transit SuccessStory, National Renewable Energy Laboratory, Golden, CO, NREL/SP-425-21606.


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Chandler, K., Malcosky, N., Motta, R., Norton, P., Kelly, K., Schumacher, L.,Lyons, D., 1996,Alternative Fuel Transit Bus Evaluation Program Results,SAE International, Warrendale, PA, SAE Pub. #961082.

Motta, R., Norton, P., Kelly, K., Chandler, K., Schumacher, L., Clark, N., 1996,Alternative Fuel Transit Buses, Final Results from the National Renewable

Energy Laboratory Vehicle Evaluation Program, National Renewable EnergyLaboratory, Golden, CO, NREL/TP-425-20513.

Chandler, K., Malcosky, N., Motta, R., Kelly, K., Norton, P., Schumacher, L.,1996,Final Alternative Fuel Transit Bus Evaluation Results, Battelle,Columbus, OH.

Wang, W., Gautam, M., Sun, X., Bata, R., Clark, N., Palmer, G., Lyons, D., 1993,Emissions Comparisons of Twenty-Six Heavy-Duty Vehicles Operated on Con-ventional Alternative Fuels, SAE International, Warrendale, PA, SAE Pub.#932952.

Bata, R., Clark, N., Gautam, M., Howell, A., Long, T., Loth, J., Lyons, D., Palmer,M., Rapp, B., Smith, J., Wang, W., 1991, The First Transportable Heavy Duty

Vehicle Emissions Testing Laboratory, SAE International, Warrendale, PA, SAEPub. #912668.


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Appendix AFleet Summary

Statistics


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Diesel LNG LNGControl 4300 4500

Fleet Mileage 243,606 402,618 143,429

Total Parts Cost 33,807.74 54,219.93 17,228.68

Total Labor Hours 1925.6 2809.1 797.8

Average Labor Cost 96,280.00 140,454.50 39,887.50(@ $50.00 per hour)

Total Maintenance Cost 130,087.74 194,674.43 57,116.18

Total Maintenance Cost per Mile 0.534 0.484 0.398

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Number of Vehicles 5 10 5

Period Used for Fuel and Oil Op Analysis 2/99-1/00 2/99-1/00 6/9-1/00

Total Number of Months in Period 12 12 8

Fuel and Oil Analysis Base Fleet Mileage 218,672 369,563 171,358

Period Used for Maintenance Op Analysis 6/98 - 5/99 1/99 - 1/00 7/99 - 1/00

Total Number of Months in Period 12 12 6

Maintenance Analysis Base Fleet Mileage 243,606 402,618 143,429

Average Monthly Mileage per Vehicle 4,321 3,232 4,486

Fleet Fuel Usage in Diesel #2 Equiv. Gal. 57,849 136,743 63,415

Representative Fleet MPG 3.78 1.62 1.62

Representative Fleet MPG (energy equiv) 3.78 2.70 2.70

Ratio of MPG (AF/DC) 0.71 0.71

Average Fuel Cost as Reported (with tax) 0.90 0.51 0.51

per Gal D2 per Gal LNG per Gal LNG

Average Fuel Cost per Energy Equivalent 0.90 0.85 0.85

Fuel Cost per Mile 0.238 0.314 0.314

Number of Make-Up Oil Quarts per Mile 0.002 0.002 0.001

Oil Cost per Quart 0.65 0.85 0.85

Oil Cost per Mile 0.001 0.002 0.001

Total Scheduled Repair Cost per Mile 0.114 0.115 0.102

Total Unscheduled Repair cost per Mile 0.420 0.368 0.296

Total Maintenance Cost per Mile 0.534 0.484 0.398

Total Operating Cost per Mile 0.773 0.799 0.713

Dallas Area Rapid Transit (Dallas, TX) Fleet Summary Statistics

Fleet Operations and Economics

Maintenance Costs


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Fleet Mileage 243,606 402,618 143,429

Total Engine/Fuel-Related Systems(ATA VMRS 30,31,32,33,41,42,43,44,45)

Parts Cost 6,471.72 12,121.26 5,330.47

Labor Hours 315.8 739.7 182.6

Average Labor Cost 15,791.50 36,985.00 9,127.50

Total Cost (for system) 22,263.22 49,106.26 14,457.97

Total Cost (for system) per Mile 0.0914 0.1220 0.1008

Exhaust System Repairs (ATA VMRS 43)

Parts Cost 102.44 120.38 35.87

Labor Hours 19.6 12.2 2.0

Average Labor Cost 981.00 608.50 100.00

Total Cost (for system) 1,083.44 728.88 135.87


Fuel System Repairs (ATA NVMRS 44)

Parts Cost 87.16 623.43 601.01

Labor Hours 22.3 106.3 21.6

Average Labor Cost 1,112.50 5,312.50 1.077.50



Power Plant (Engine) Repairs (ATA VMRS 45)

Parts Cost 3,375.43 4,062.19 1,406.39

Labor Hours 82.1 262.1 57.8




Electrical System Repairs (ATA VMRS 30-Electrical General, 31-Charging,32-Cranking, 33-Ignition)

Parts Cost 1,082.18 5,325.12 2,801.24

Labor Hours 134.7 254.0 88.0




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Breakdown of Maintenance Costs by Vehicle System Similar Vehicle Lifetimes


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Air Intake System Repairs (ATA VMRS 41)

Parts Cost 1,325.24 1,667.41 354.74


Average Labor Cost 1,112.50 1,222.50 275.00

Total Cost (for system) 2,437.74 2,889.91 629.74


Cooling System Repairs (ATA VMRS 42)

Parts Cost 499.27 322.73 131.21





Brake System Repairs (ATA VMRS 13)

Parts Cost 1,434.07 4,077.77 1,585.65

Labor Hours 218.3 200.2 54.5




Transmission Repairs (ATA VMRS 27)

Parts Cost 1,037.26 2,519.44 526.34





Cab, Body and Accessories Systems Repairs(ATA VMRS 02-Cab and Sheet Metal, 50-Accessories, 71-Body)

Parts Cost 18,216.03 26,623.77 7,949.59

Labor Hours 636.1 837.4 303.5




Breakdown of Maintenance Costs by Vehicle System (continued)


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Inspections Only No Parts Replacements (101)

Parts Cost 0.00 0.00 0.00

Labor Hours 347.8 564.0 184.4




HVAC System Repairs (ATA VMRS 01)

Parts Cost 875.61 940.82 191.17

Labor Hours 88.4 133.8 10.7




Air System Repairs (ATA VMRS 10)

Parts Cost 671.46 804.23 82.25





Lighting System Repairs (ATA VMRS 34)

Parts Cost 1,674.18 2,183.68 193.53

Labor Hours 132.5 137.3 25.2




Frame, Steering, and Suspension Repairs(ATA VMRS 14-Frame, 15-Steering, 16-Suspension)

Parts Cost 3,381.82 4,131.46 1,190.47

Labor Hours 71.7 32.5 15.0




Breakdown of Maintenance Costs by Vehicle System (continued)


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Axle, Wheel, and Drive Shaft Repairs(ATA VMRS 11-Front Axle, 18-Wheels, 22-Rear Axle, 24-Drive Shaft

Parts Cost 45.59 817.50 179.21


Average Labor Cost 575.00 1,172.50 175.00

Total Cost (for system) 620.59 1,990.00 354.21


Tire Repairs (ATA VMRS 17)

Parts Cost 0.00 0.00 0.00

Labor Hours 24.8 23.3 13.0


Documents

Alternative Fuel Transit Buses