U.S. Department of Energy

Office of Transportation Technologies

Office of Energy Efficiency and Renewable Energy

T OF ENERGY

DEPARTMEN

U

E

NITED STAT S OFA

ERICA

M
Federal Alternative Motor Fuels Programs

Fifth Annual Report to Congress

September 1996

U.S. Department of Energy

Office of Transportation Technologies

Office of Energy Efficiency and Renewable Energy

Alternative Fuels Data Center Internet Address -

http://www.afdc.doe.gov

T OF ENERGY

DEPARTMEN

U

E

NITED STAT S OFA

ERICA

M
The U.S. Department of Energy

gratefully acknowledges the 

cooperation of the participating

Federal agencies in the Alternative

Motor Fuels Programs—the General

Services Administration; the

National Highway Traffic Safety

Administration and the Federal

Transit Administration (which 

are both entities within the U.S.

Department of Transportation); the

Environmental Protection Agency;

and the many other Federal agencies

that are operating these vehicles and

supplying valuable information on

their operation. The Department also

acknowledges the participation and

cooperation of the vehicle and

engine manufacturers, fuel suppliers,

private fleet operators, and state and

local transit companies. The many

organizations involved have worked

to make this program a success.

ii

Acknowledgments

“. . . the displacement of energy

derived from imported oil with

alternative fuels will help to

achieve energy security and

improve air quality.”

— Alternative Motor

Fuels Act of 1988
Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Establishing the Programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

The Program Partnership . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

Light-Duty Vehicles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

Emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

Performance and Reliability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28

Fuel Economy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29

Cost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33

Transit Buses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35

Emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37

Performance and Reliability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42

Fuel Economy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43

Cost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49

Heavy-Duty Vehicles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51

Emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .54

Performance and Reliability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .60

Fuel Economy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61

Cost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .64

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66

Aftermarket Vehicle Conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69

Program Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .70

Emissions Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .72

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .76

Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77

Infrastructure Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .79

Refueling Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .79

Maintenance Facilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .80

Vehicle Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .82

Where We Are . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .82

Vehicle Availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83

Alternative Fuel Vehicles in Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83

Information Dissemination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .85

The Alternative Fuels Data Center . . . . . . . . . . . . . . . . . . . . . . . . . . . .85

Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1

Contents

iii
Abstract

This annual report to Congress 

presents the current status of the 

U.S. Department of Energy’s alternative fuel vehicle demonstration and

performance tracking programs

being conducted across the country

in accordance with the Energy Policy

and Conservation Act (42 U.S.C.

6374, et seq.). These programs,

which comprise the most comprehensive data collection effort ever

undertaken on alternative transportation fuels and alternative fuel vehicles, are beginning their sixth year.

This report summarizes tests and

results from the fifth year. Even

though present interest in electric

vehicles is quite high, they are not

currently included in these vehicle

demonstration and performance

tracking programs, and the annual

report does not include information

on them.

Since the inception of the programs,

great strides have been made in

developing commercially viable

alternative fuel vehicle technologies,

these achievements having been

accomplished in large part as a 

result of the Department of Energy’s

direct encouragement and support.

However as is the case in the commercialization of all new technologies, some performance problems

have been experienced on vehicles

involved in early demonstration

efforts. 

Substantial improvements have 

been recorded in vehicle practicality,

safety, and performance in real-world

demonstrations, especially during the

past year. An aspect of particular

interest is emissions output. To date,

results from light-duty alternative

fuel vehicles procured from original

equipment manufacturers and operating in the Federal fleet have demonstrated superior in-service emissions

performance. In addition, heavy-duty

alternative fuel vehicles have demonstrated dramatic reductions in particulate emissions. On the other hand,

emissions results from vehicles converted to run on alternative fuel have

not been as promising. These and

other findings are available through

the Department of Energy’s Alternative Fuel Data Center World Wide

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

Although the technologies available

today are already commercially

viable in some markets, further

improvements in infrastructure 

and economics will result in greater

market expansion and an attendant

increase in the number of vehicles

deployed. To this end, the

Department of Energy plans to continue its efforts to foster additional

growth toward technically and economically viable alternatives to

petroleum-based transportation fuels. 

Through these and other alternative

fuels programs, and with the assistance of its staff and technology 

1

Executive Summary
partners around the country, the 

U.S. Department of Energy continues to make significant contributions

toward achieving the national goals

of increasing energy security, reducing trade deficits, creating more

domestic jobs and industries, and

promoting cleaner air.

Summary of Results

Light-Duty Vehicles

The Federal light-duty vehicle

demonstration program studies emissions, vehicle performance, and fuel

economy on passenger cars, minivans, and light vans and trucks that

operate on alternative fuels. This

effort is focused on meeting the

requirements of section 400 AA of

the Energy Policy and Conservation

Act (The Act). At the Federal level,

alternative fuel vehicles are required

to be purchased from the original

equipment manufacturers and placed

in service throughout the Federal

fleet.

The number of alternative fuel vehicles in the Federal fleet has grown to

nearly 20,000. For cost effectiveness,

and to minimize the impact on 

day-to-day government operations,

data are collected only on a sample

of this number. The light-duty vehicle test program is currently collecting data from 337 vehicles that operate on one of the alternative fuels,

plus 146 vehicles that operate only

on reformulated gasoline (the control

group).

New models added in program 

year 1995 include the 1995 Dodge

Caravan, a dedicated compressed

natural gas vehicle, and the 1995

2

Executive Summary

The Fuels Being Tested

In all, the three programs being managed by the U.S. Department of

Energy are testing five kinds of alternative fuels—methanol, ethanol,

compressed natural gas, liquefied natural gas, and propane—plus

biodiesel. What are these fuels and why are we testing them?

Methanol. Methanol is an alcohol derived primarily from natural gas,

but it can also be derived from biomass or coal. Thus the potential

domestic resource base for methanol is vast. Methanol’s combustion

holds the promise of producing less carbon monoxide and non-methane

hydrocarbons than gasoline and less particulate matter than diesel. It

may also be converted into methyl tertiary butyl ether for a high-octane,

oxygenated additive with gasoline.

Ethanol. Ethanol is an alcohol derived from biomass (corn, sugar cane,

grasses, trees, and agricultural waste). The potential domestic resource

base for ethanol is also vast. Ethanol’s combustion promises emissions

similar to those from methanol. And, like methanol, it also can be used

to make a high-octane, oxygenated ether.

Compressed Natural Gas and Liquefied Natural Gas. Natural gas is 

primarily methane (approximately 93 percent) with a mixture of other

gaseous hydrocarbons. It is derived from gas wells or in conjunction

with crude oil production. The United States has proven natural gas

reserves of approximately 170 trillion cubic feet; current natural gas

consumption is primarily (89 percent) derived from domestic sources,

with the remainder coming mainly from Canada. Relative to gasoline,

the combustion of natural gas promises to cut emissions of carbon

monoxide and non-methane hydrocarbons. The difference between 

the compressed and liquefied versions of natural gas lies in the phase 

in which they are stored. To obtain the liquefied version, the gas must

be cooled considerably and stored in insulated tanks.

Propane. This is a gas composed primarily of the three-carbon 

molecule propane and other gaseous hydrocarbons. It is extracted 

from natural gas or refinery gas streams. Its emissions are expected to

be similar to those of natural gas.

Biodiesel. As tested in this program, biodiesel (B20) is actually a lowlevel blend of 20 percent diesel derived from biomass, microalgae, or

agricultural waste and 80 percent conventional diesel. Although it has

properties similar to conventional diesel fuels, its potential value derives

from the fact that its production can be based on a domestic and renewable resource. However, only B100 (neat biodeisel) is currently considered by the U.S. Department of Energy to be an alternative fuel under

the definition contained in the Act.
Dodge Intrepid, a flexible-fuel 

vehicle operating on 85 percent

methanol. Information obtained 

from the analysis of light-duty 

vehicle data through August 1995

includes emissions, performance and

reliability, fuel economy, and cost.

Emissions

Emissions measurement is the single

most comprehensive part of the test

program for light-duty vehicles. 

The effort being undertaken is also

the most extensive and carefully 

controlled study of emissions of

alternative fuel vehicles in the world. 

Phase I testing began in 1991 and

lasted through 1994. To obtain results

from a wider range of alternative fuel

vehicles at a higher level of statistical

reliability, the number and types of

vehicles tested were greatly increased

under Phase II of the program.

Average emissions from the fourcylinder methanol Dodge Spirits are

well below the Federal emissions

standards for non-methane hydrocarbons, carbon monoxide, and oxides

of nitrogen. The regulated exhaust

emissions from the ethanol tests 

on the variable fuel vehicles were 

15 percent to 20 percent lower than

those from the reformulated gasoline

tests on the same vehicles. Analysis

from the first round of testing of the

Dodge B250 vans indicates notably

lower emissions of regulated exhaust

pollutants from the compressed natural gas vehicles in contrast to those

produced by the standard gasoline

vehicles. The exhaust emissions from

the flexible-fuel Ford Econoline vans

tested on methanol were lower than,

or similar to, the exhaust emissions

of those same vehicles when tested

on reformulated gasoline.

The urban ozone-forming potential

calculated from the alternative fuel

vehicle emissions was substantially

less than their reformulated gasoline

counterparts. Urban ozone-forming

potential was reduced 25 percent,

40 percent, 50 percent, and 80 percent

for the ethanol Chevrolet Luminas,

the methanol Dodge Spirits, the

methanol Ford Econoline vans, and

the compressed natural gas Dodge

B250 vans, respectively. These results

are illustrated in Figure 1.

Performance and Reliability

Information has been collected

regarding the performance and reliability of alternative fuel vehicles, and

their standard gasoline counterparts,

for nearly four years. As expected,

drivers reported more performance

3

Executive Summary

Figure 1. Reduction in light-duty vehicle urban ozone-forming potential

attributable to alternative fuels

M65-B034401
problems, on average, for the earlymodel alternative fuel vehicles than

for the later-model vehicles. From the

drivers’ perspective, the performance

of alternative fuel vehicles in general

has improved with time, and is now

nearly equal to the accepted performance level of gasoline vehicles.

Fuel Economy

Testing of vehicles on a chassis

dynamometer, and analysis of refueling records from actual daily use,

have resulted in two sources of fuel

economy information. In the first

case, information is obtained on 

each vehicle at the time of emissions

testing on a chassis dynamometer. In

the second case, actual in-use fuel

economy is calculated using refueling records maintained in the

Department of Energy’s Alternative

Fuels Data Center at the National

Renewable Energy Laboratory.

During actual use, vehicle fuel economy varies considerably because of

individuals’ driving styles and a

number of other factors, such as 

the type of driving (stop-and-go city

driving, highway driving, deliveries,

or a combination of all three), climate, and altitude. On an equivalent

energy basis, vehicles operating on

alternative fuels tend to achieve levels of fuel economy that are similar

to those achieved by standard vehicles operating on gasoline.

Cost

Total vehicle cost includes initial

acquisition, insurance, maintenance,

fuel, and oil.

The information available to date 

on alternative fuel vehicles in the

Federal light-duty vehicle demonstration program indicates the cost of

acquiring those vehicles ranges up to

25 percent higher than the cost of

comparable gasoline vehicles. For

flexible-fuel vehicles in particular,

the price increases range between 

$0 to $800, depending on the manufacturer. For compressed natural gas

vehicles, the price increase can be 

as much as $5,000 per vehicle.

In September 1995, retail pump fuel

prices across the country ranged

from approximately $1.60 to $1.87

per gallon of 85 percent ethanol,

$2.00 to $2.88 per gallon of 

85 percent methanol, $0.60 to $1.14

per gallon of compressed natural gas,

and $1.10 to $1.18 per gallon of 

regular unleaded gasoline. These

price ranges account for differences

in fuel energy content and reflect the

alternative fuel cost on a per-gallonof-gasoline equivalent basis.

Most maintenance on General

Services Administration vehicles is

done under warranty at no cost to 

the fleet operator (except for lost

time in service). Therefore, data on

the actual cost of maintenance, and 

a summary of average maintenance

costs per mile, are not yet available.

Analysis of information available to

date indicates that the number of

unscheduled repairs on alternative

fuel vehicles decreases with each

new model year. This evidence,

along with growing experience,

increases the confidence that in the

long-term, average maintenance

costs for alternative fuel vehicles 

will approach those of standard 

gasoline vehicles.

4

Executive Summary
Transit Buses

The Federal transit bus demonstration

program (section 400 CC of the Act)

is designed to provide a comprehensive study of the alternative fuels currently used by the transit bus industry. The following eight metropolitan

areas were selected for program participation: Houston, Texas; Miami,

Florida; Minneapolis, Minnesota;

New York, New York; Peoria, Illinois;

St. Louis, Missouri; Tacoma,

Washington; and Portland, Oregon.

Buses used by the transit agencies 

of these municipalities are being

operated on, and are undergoing a

number of tests on, four different

alternative fuels—compressed natural

gas, liquefied natural gas, methanol,

ethanol—plus B20 (a low-level blend

of 20 percent biodiesel and 80 percent conventional diesel fuel). Only

B100 (neat biodiesel) is considered

an alternative fuel under the Act.

The alternative fuel engines included

in the transit bus demonstration program are: Detroit Diesel 6V92TA

methanol engine; Detroit Diesel

6V92TA ethanol engine; Detroit

Diesel 6V92TA pilot ignition natural

gas engine; Cummins L10G natural

gas engine. All transit buses are 

35-foot or 40-foot models manufactured by Mercedes, Flxible, Gillig,

TMC, and BIA.

Emissions

With funding from the U.S. Department of Energy, West Virginia

University’s Department of Mechanical and Aerospace Engineering

designed and constructed a transportable chassis dynamometer to test

emissions levels from heavy-duty

vehicles. The transportability of this

chassis dynamometer allows a large

number of emissions tests on transit

buses and heavy-duty vehicles to be

conducted around the country on site.

During 1995, West Virginia

University personnel traveled to 

transit agency facilities in New York

City, Miami, Peoria, St. Louis,

Minneapolis, Tacoma, and 

Portland, Oregon, to test transit

buses included in the Federal 

demonstration program.

These tests conducted by West

Virginia University show that emissions of particulate matter are

reduced to nearly zero in engines

fueled with compressed natural gas.

This is an important and attractive

feature of this fuel that reduces the

amount of black smoke emanating

from city buses. Transit buses fueled

by ethanol and methanol also emit

lower particulate matter levels than

otherwise identical diesel buses 

(see Figure 2).

The tests conducted to date show

that emissions of hydrocarbons, carbon monoxide, and oxides of nitrogen from alternative fuel transit

buses vary more than expected. In

some cases, emissions were lowered,

but high-emitting alternative fuel

vehicles were also found. To identify

the sources of the problems, teams 

of experts were brought together to

diagnose and repair high emitters.

These teams were comprised of 

representatives from the National

Renewable Energy Laboratory, West

Virginia University, the engine manufacturers, and their affected transit

agencies. This work helped explain

5

Executive Summary
the causes for high emissions and

resulted in dramatic reductions at

two transit sites.

West Virginia University’s emissions

testing activities have helped to

underscore two very important

points. First, by participating in

demonstration programs, transit

agencies can play an important role

in developing technologies that will

help to improve air quality. Second,

the diagnosis and repair of high

emitters have shown that, even

though the use of alternative fuels

may reduce emissions, engine technology and proper vehicle maintenance are also crucial factors.

Performance and Reliability

A common measure of transit bus

reliability is the number of road 

calls that are required for every

1,000 miles each vehicle travels.

Information on the road calls per

1,000 miles of operation for vehicles

in the Federal transit bus demonstration program show the alternative

fuels to be quite similar to their

diesel counterparts in most locations.

Fuel Economy

Fuel economy and fuel costs are 

very important to transit agencies

because these elements represent 

a significant portion of the total

expense of operating a transit bus.

Approximately half the total cost

(excluding driver costs) of operating

a diesel transit bus is directly attributable to fuel economy and fuel cost. 

The average fuel economy for 

liquefied natural gas/diesel dualfuel transit buses was approximately

16 percent less than the average fuel

economy for their diesel counterparts. Most of this reduction in fuel

economy is likely attributable to

problems with the engine. 

The average fuel economy of the

compressed natural gas transit buses

from dynamometer and on-road tests

is about 10 percent to 20 percent

lower than the corresponding average fuel economy for their diesel

counterparts. This reduction is within

the expected range, as the compressed natural gas engines use a

spark-ignited design as opposed to

the more efficient compressionignition design of the diesel engines.

With regard to the fuel economy 

of alcohol transit buses, the results to

date indicate that the vehicles at all

the sites are performing very well,

delivering fuel economy comparable

to that of their diesel counterparts 

on an energy equivalent basis.

6

Executive Summary

Figure 2. Summary of heavy-duty

vehicle particulate emissions results

M65-B034402
Cost

There are incremental costs associated with operating alternative fuel

transit buses. These costs can be

aggregated into increased capital 

outlays and increased operating

expenses. Increased capital outlays

are attributable to the additional costs

(if any) of acquiring alternative fuel

transit buses and modifying facilities. 

Increased operating expenses are 

due to a larger number of factors. 

A breakdown of the estimated total

operating costs for a typical large

transit agency such as the ones participating in the Federal transit bus

demonstration program includes 

driver labor, vehicle maintenance,

administration, and fuel expense.

Driver labor costs represent more

than half the total.

One common measure, fuel cost 

per mile, is calculated using average

in-use fuel economy and the actual

fuel cost paid by the transit agencies.

For transit buses operating on compressed natural gas, the fuel and

maintenance costs per mile are about

the same as those for transit buses

operating on diesel. However, for

transit buses operating on an alcohol

fuel or B20 (a low-level biodiesel

blend not considered by the U.S.

Department of Energy to be an alternative fuel under the Act), the same

costs are up to twice as high as those

for transit buses operating on diesel.

The fuel and maintenance costs for

transit buses operating on dual-fuel

liquefied natural gas/diesel are about 

25 percent higher than for their 

diesel counterparts.

Heavy-Duty Vehicles

The Federal heavy-duty demonstration program (section 400 BB of the

Act) includes two types of vehicles:

medium-sized commercial delivery

vans and large trucks (such as linehaul tractor trailers and garbage

packers). In total, some 170 delivery

vans and large trucks are included 

in the program. With regard to the

medium-sized delivery vans, vehicles

in two commercial delivery fleets 

are included: Federal Express and

United Parcel Service. The Federal

Express vehicles are evaluated in the

CleanFleet project, which is coordinated by Battelle Memorial Institute.

The U.S. Department of Energy also

manages a grant program that supports states in their purchases of

heavy-duty alternative fuel vehicles.

The vehicles in the grant program are

located all across the country, representing vehicle vocations that range

from street sweepers to school buses.

Emissions

During 1995, West Virginia

University used its transportable

chassis dynamometer to measure

emissions from the New York City

Department of Sanitation’s compressed natural gas garbage packers,

Archer Daniels Midland’s ethanol

line-haul trucks in Illinois, Hennepin

County’s ethanol snowplows in

Minnesota, and AG Processing

Corporation’s line haul trucks operating on B20, the biodiesel blend, and

diesel. A number of diesel control

vehicles with the same engine configurations were also tested at each of

the sites. Particulate emissions results

from this test program on heavy-duty

trucks are summarized in Figure 2.

7

Executive Summary
The use of alternative fuels in heavyduty trucks can substantially reduce

particulate matter emissions. The

average of particulate matter from

the ethanol trucks in the Federal

heavy-duty demonstration program 

is less than 50 percent of the corresponding value for their diesel 

counterparts. On the other hand, the

average particulate matter emissions

from the compressed natural gas

vehicles is very low. In six of eleven

tests performed to date, particulate

matter levels are essentially zero (i.e.,

too low to measure), and the diesel 

vehicles average approximately 

0.7 grams per mile. 

Emissions information has also been

obtained from the Federal Express

CleanFleet project. In this project,

36 delivery vans (actually mediumduty vehicles) were emissions tested

at each of three different mileage

levels.

The CleanFleet compressed natural

gas vehicles emitted an average of 

65 percent to 80 percent less carbon

monoxide than otherwise identical

vehicles running on gasoline. These

vehicles also had 70 percent to 

95 percent lower non-methane

hydrocarbon emissions. Emissions 

of oxides of nitrogen were mixed.

The difference in emissions from

delivery vans operating on propane

and those from their counterparts

operating on gasoline became more

pronounced with increasing mileage.

Generally, the average emissions levels from the propane vans remained

relatively constant, but the gasoline

control vans exhibited increasing values with increasing mileage.

The overall results from the Ford

vans running on 85 percent methanol

were highly variable; but, in general,

these vehicles tend to exhibit lower

average carbon monoxide emissions

than their gasoline counterparts.

Performance and Reliability

Vehicle performance for heavy-duty

trucks and commercial delivery vans

encompasses such factors as acceleration, hill climbing, driveability, and

driver acceptance. To directly assess

the performance of heavy-duty trucks

operating on alternative fuels, acceleration and hill climbing capability

of a compressed natural gas line-haul

truck operated by Vons Grocery

Company, and a diesel counterpart,

were measured. Acceleration for the

two trucks was nearly identical.

Fuel Economy

All fuel economy data for the

CleanFleet delivery vans have 

been collected and analyzed. The

Chevrolet propane and compressed

natural gas vans and Dodge compressed natural gas vans achieved 

10 percent to 15 percent lower in-use

fuel economy than their gasoline

counterparts on an energy equivalent

basis. The fuel economy achieved by

all the Ford vehicles (compressed

natural gas, propane, and 85 percent

methanol) was within a few percentage points of the fuel economy

achieved by their gasoline counterparts on an energy equivalent basis.

So far, most of the alternative fuel

large trucks have exhibited both 

in-use and dynamometer fuel 

economy comparable to their 

diesel counterparts.

8

Executive Summary
Cost

As expected, equipping a prototype

or early-production heavy-duty truck

to use alternative fuels is more expensive than equipping a similar truck to

operate on diesel. As the heavy-duty

alternative fuel market develops, such

costs are expected to decrease. 

In principle, no alternative fuel engine

should be inherently more expensive

to manufacture than a diesel engine.

In contrast, the fuel tanks for compressed natural gas will probably continue to be more expensive. However,

this is a relatively small part of the

total cost of the vehicle. 

A small incremental cost for the fuel

system could easily be recovered in

lower fuel costs. Fuel cost is generally a large part of the total operating

cost of a trucking company—second

only to personnel costs. As noted

previously, the cost of alternative

fuels varies from one fuel to another,

both regionally and over time.

Federal and state taxes also figure

heavily into fuel cost.

Virtually all the heavy-duty, alternative fuel vehicles in the Federal

demonstration program cost more 

to maintain than their diesel counterparts. Most of the vehicles in the

program represent prototype, fieldtest technology, and part of the 

reason for deploying and tracking

them is to work out the bugs in the

technology so they can be moved

closer to commercialization. Higher

maintenance costs are to be expected

for such vehicles. As alternative fuel

engine manufacturers accumulate

experience through such programs,

the reliability of the engines will

increase and maintenance costs

should approach those of their 

diesel counterparts.

Aftermarket 

Vehicle Conversions

The Energy Policy Act of 1992 

(42 U.S.C. 13212 (a) and (b)), which

amends the Act, specifies minimum

purchase requirements for alternative

fuel vehicles in the Federal fleet.

Although alternative fuel vehicles

have been under development for

more than ten years, their availability

from the automotive manufacturers

was not sufficient in calendar year

1992 to allow the various Federal

agencies to meet the requirements of

the Act. “Aftermarket conversions”

were chosen to fill the gap until a

sufficient number of original equipment models could be made available at a reasonable cost.

The conversion effort has succeeded

in helping the Federal government

meet the requirements of the Act during a period of otherwise uncertain

supply. Original equipment availability has since improved, however.

At this time, light-duty vehicles may

be converted to operate on one of

two alternative fuels—natural gas or

liquefied petroleum gas (propane).

Each aftermarket vehicle conversion

is protected by a warranty that covers

all installed conversion system parts

and associated labor for three years

or 36,000 miles, whichever comes

first. As required by the provisions 

of the Act, subcontractors signed

individual warranty agreements with

Chrysler, Ford, and General Motors.

9

Executive Summary
The first light-duty vehicle conversions were completed during the

summer of 1994. Conversion activities are continuing through the date

of this writing.

Most light-duty vehicle conversions

(more than 92 percent) are bi-fuel

conversions, which means that the

vehicle may operate on either gasoline or the designated alternative

fuel. The average total cost for each

compressed natural gas conversion 

in the program is about $4,500. The

average total cost for each liquefied

petroleum gas conversion, on the

other hand, is about $2,700.

Emission Results

Aftermarket conversions can play 

an important role in the transition to

more widespread use of alternative

fuel vehicles. However, the emissions performance to date of these

relatively advanced conversion systems raises questions about their

overall emissions contribution to 

the environment. There are plans 

for further testing in 1996 to help

answer these questions.

Infrastructure Support

To meet the demands that the

increasing numbers of alternative

fuel vehicles are placing on the 

U.S. marketplace, an associated

infrastructure has developed. This

infrastructure, consisting of refueling

sites and maintenance and storage

facilities, is the fabric that holds the

components of the alternative fuel

industry together. Growth of this

infrastructure has been stimulated 

by various legislative incentives,

such as the Alternative Motor Fuels

Act of 1988, the Clean Air Act

Amendments of 1990, the Energy

Policy Act of 1992, and Executive

Order 12844. Also, the Department

of Energy has promoted infrastructure development within the context

of its Clean Cities program.

Expanded development of refueling

sites faces a number of hurdles,

depending on the alternative fuel of

interest. For methanol and ethanol

refueling stations, it is relatively easy

to install a new in-ground or aboveground fuel storage tank. Special

attention must be given to the choice

of materials used.

For compressed natural gas, all such

options are more expensive than

those for alcohol fuels. A slow-fill

system uses a small compressor and

has the lowest cost. A fast-fill system, on the other hand, requires a

large and expensive compressor station. Most public access compressed

natural gas stations are fast-fill, but

they can cost $200,000 to $300,000

to build.

All of the above considerations 

notwithstanding, the number of 

alternative fuel refueling stations

continues to increase. As of 

August 1, 1995, there were more

than 1,100 compressed natural gas

stations, 88 methanol stations, and

36 ethanol stations. The total number

of alcohol and natural gas refueling

sites for alternative fuels has more

than quadrupled in the past five

years. The Liquefied Petroleum Gas

Clean Fuels Coalition recently estimated that there are now as many as

11,000 sites where propane can be

obtained for this purpose.

10

Executive Summary
Transit bus agencies and heavy-duty

fleet operators generally install their

own fueling stations and do not use

public facilities.

The General Services Administration

reports that, as a rule, alternative fuel

vehicle maintenance was sometimes

difficult in the early years of the program (1991–1992), but is no longer

the problem it once was.

The infrastructure for alternative fuel

vehicles is growing at a pace that

parallels the number of alternative

fuel vehicles being deployed. No 

significant impediment to further

expansion is evident.

Vehicle Availability

The number of light-duty alternative

fuel vehicles operating in U.S.

Federal and non-Federal fleets has

increased steadily over the past several years. The Energy Information

Administration projects an increase

in ethanol flexible-fuel vehicles to

nearly 32,000 units in the near future

because of an announcement that

Chevrolet will manufacture an

ethanol-compatible pickup truck.

Light-duty vehicles fueled by liquefied petroleum gas are estimated to

be the largest group of vehicles in

the United States operating on a 

fuel other than gasoline. The best

information currently available 

puts the total at approximately

217,000 units.

In January 1995, a survey of transit

bus agencies was conducted by the

American Public Transit Association.

The survey results indicate that, of

the more than 52,000 buses currently

in operation around the country,

about 3 percent of them now operate

on alternative fuels.

In 1995, the light-duty manufacturers

offered six compressed natural gas

models (including dedicated minivans, pickups, a dedicated van, a 

bi-fuel van, and a bi-fuel pickup),

two 85 percent ethanol flexible-fuel

sedans, and one liquefied petroleum

gas heavy-duty truck. The models

available in 1996 will include one 

85 percent ethanol sedan, six compressed natural gas vehicles (including dedicated minivans, pickups,

vans, and sedans), a bi-fuel van, a 

bi-fuel pickup, and one liquefied

petroleum gas medium-duty truck.

The Energy Policy Act (42 U.S.C.

13212 (b) (1) (A)) mandates 

that 25 percent of all new vehicle

purchases made in fiscal year 1996

by the Federal government must be

alternative fuel vehicles. Based on

projected vehicle acquisitions, the

General Services Administration 

will be required to purchase approximately 8,600 units.

Information Dissemination

Information dissemination is an

important component in the

Department of Energy’s program to

expand the use of alternative fuels in

the United States. Accurate, timely,

and readily available information can

only help to hasten public acceptance

and adoption of alternative fuels 

and alternative fuel vehicles. The

legislation requiring these activities

includes the Alternative Motor Fuels

Act of 1988, the Clean Air Act

Amendments of 1990, the Energy

Policy Act of 1992, and Executive

Order 12844.

11

Executive Summary
To make the best possible use of all

the information being collected

through the various vehicle demonstration programs, the Office of

Alternative Fuels in the Department

of Energy’s Office of Transportation

Technologies established the

Alternative Fuels Data Center at 

the National Renewable Energy

Laboratory. This center serves as 

the focal point for the information

collected in all the vehicle demonstration programs. The Alternative

Fuels Data Center maintains information on line in computerized databases, although hard copies are available as well, that are distributed

through the National Alternative

Fuels Hotline (1-800-423-1DOE).

Several methods are available for

accessing information in the

Alternative Fuels Data Center. The

primary method is via the World

Wide Web on the Internet

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

12

Executive Summary
Establishing the Programs

In 1988, Congress passed the

Alternative Motor Fuels Act, Public

Law 100-94, which added sections

400 AA–400 EE to the Energy

Policy and Conservation Act (42

U.S.C. 6374 et seq.) (the Act).

Recognizing that displacing energy

derived from imported oil with alternative fuels will help achieve energy

security and improve air quality, the

lawmakers designed this legislation

to encourage the development of

vehicles that could run on alternative

fuels such as methanol, ethanol,

and natural gas.

With the additions noted above,

the Act directs the U.S. Department

of Energy to cooperate with other

Federal agencies to acquire and operate vehicles that use alternative fuels.

It also requires the Department of

Energy to conduct a study of the performance, fuel economy, emissions,

and costs of these vehicles in comparison with those that run on conventional fuels, and to provide

Congress an annual report of that

study (42 U.S.C. 6374 (b) (1) and

(3)) (the sidebar on page 15 summarizes the provisions of the Alternative

Motor Fuels Act). This is the fifth

annual report on the study program

set up by the Department of Energy.

The Programs

In 1990, under the provisions of 

the Act, the Department of Energy

cooperated with other Federal agencies to establish a nationwide effort

(Figure 3) encompassing three 

programs of study: • The Alternative Fuels Light-Duty

Demonstration Program. In this

program, established under section

400 AA of the Act (42 U.S.C.

6374), the General Services

Administration, in conjunction

with the Department of Energy,

annually purchases a practicable

number of passenger cars and

light-duty trucks and vans for use

in the fleets of various agencies 

of the Federal government. The

Department of Energy cooperates

with vehicle manufacturers, vehicle dealerships, government agencies, test laboratories, and others 

to collect and analyze data on a

selected subset of these vehicles

and compares these data with data

collected from vehicles operating

on gasoline. The vehicles are operated at various locations across 

the nation to capture the effects of

climatic conditions and altitude on

vehicle operation and maintenance.

This program studies vehicles 

that operate on methanol, ethanol,

compressed natural gas, and gasoline. Those operating on methanol

or ethanol are actually flexiblefuel vehicles, which means they

can operate on their designated

alcohol, on gasoline, or on any

mixture of the alcohol (up to 

85 percent) and gasoline. Those

operating on compressed natural

gas or gasoline are dedicated vehicles, which means they operate 13

Background
only on the fuel for which they 

are designated. Those dedicated

vehicles operating on gasoline are

control vehicles that serve as a

baseline for comparison.

• The Alternative Fuels Transit Bus

Demonstration Program. In this

program, established under section

400 CC of the Act (42 U.S.C.

6374b), the Department of Energy

cooperates with test laboratories,

engine and chassis manufacturers,

government agencies, transit

authorities, and others to test the

operation and maintenance of alternative fuel transit buses in eight

municipalities across the nation.

Vehicles are tested with engines

and fuel systems designed to run

on methanol, ethanol, liquefied

natural gas and compressed natural gas. Standard diesel transit

buses running on B20 are also

tested (B20 is a low-level

biodiesel blend not currently considered by the Department of

Energy to be an alternative fuel

under the provisions of the Act).

Transit buses running on conventional diesel fuels are used as a

basis for comparison. Some of the

transit buses that run on liquefied

natural gas require diesel fuel as a

pilot ignition source. All the other

types of alternative fuel transit

buses are dedicated to run on the

fuel for which they are designed.

The transit bus test program

should prove quite valuable for

transit authorities. According to a

survey conducted by the American

Public Transit Association, the

transit bus sector of the market is

well ahead of other sectors in the

market penetration of alternative

fuel vehicles. Approximately

1,600 transit buses in the United

States run on alternative fuels,

representing about 3 percent of

the bus market. Until the inception

of the Department of Energy’s

program, no systematic data had

been collected on operation and

maintenance of these vehicles.

Also, a transit bus is an ideal

application of alternative fuels

because it is centrally refueled

(requiring less infrastructure

development), and because extra

space is generally available on a

bus to store the sometimes bulky

fuel tanks. This suggests that the

market for alternative fuel vehicles

could grow faster for transit buses

than for smaller vehicles, a possibility that makes good data all the 

more crucial.

• The Alternative Fuels Truck

Commercial Application Program.

Also known as the alternative fuels

heavy-duty vehicle demonstration

program, it was established under

section 400 BB of the Act (42

14

Background

Figure 3. Alternative fuel vehicles

included in the Department of Energy’s

demonstration and performance tracking programs are located in the states

highlighted in green.

M65-B034403
U.S.C. 6374a). Under this program, the Department of Energy is

cooperating with municipalities,

state and local governments, other

Federal agencies, and private fleet

operators to test the real-life operation and maintenance of two types

of vehicles running on alternative

fuels: commercial delivery vans

and heavy trucks.

The program tests trucks and vans

running on methanol, ethanol,

compressed natural gas, and

propane. (In general, the vehicles

are dedicated to running on a specific type of fuel.) It compares the

data from these vehicles with data

from control vehicles operating on

unleaded or reformulated gasoline

for the delivery vans, and diesel

fuel for the heavy trucks.

Because large trucks are typically

very expensive, the cost of the test

vehicles is shared with private fleet

owners, or with state or local governments. The heavy-duty trucks

included in the program are modified to run on methanol, ethanol,

compressed natural gas, or biodiesel. The goal is to help develop

new alternative fuel engines and

trucks (most heavy-duty alternative fuel engine development is

still in the prototype stage).

For commercial vans, two 

delivery fleets are being tracked:

the Federal Express CleanFleet,

and the United Parcel Service

fleet. The Federal Express

CleanFleet includes vehicles operating on compressed natural gas,

propane, and 85 percent methanol.

The only alternative fuel used by

vehicles in the United Parcel

Service fleet is compressed 

natural gas. Data are being collected from these vehicles and

compared with information collected from vehicles using similar

engines, but operating on gasoline.

The Program Partnership

Although the Act assigns to the

Department of Energy the responsibility for testing the vehicles and

reporting the results to Congress,

these programs are truly a partnership among a variety of entities ranging from automobile manufacturers

to Federal agencies to national laboratories to cities to private fleet operators. Each has an important role 

to play and a vested interest in 

seeing the job come to a successful

conclusion:

• The Department of Energy manages the programs and cooperates

with other Federal agencies, state

and local governments, and private companies to ensure the

smooth operation of the programs.

• The National Renewable Energy

Laboratory is the field manager

for the testing programs. The laboratory coordinates the testing

efforts, collects all the data at 

its Alternative Fuels Data Center,

analyzes and summarizes the data,

and makes the information available to all interested and qualified

parties.

• The General Services Administration purchases light-duty vehicles to be used in the programs

and distributes them to the various

Federal agencies, which use them

in their fleets, and participate in

the testing programs.

15

Background

The Alternative Motor

Fuels Act of 1988

In 1988 Congress passed the

Alternative Motor Fuels Act,

which added Sections 400 AA–

400 EE to the Energy Policy and

Conservation Act (the Act). The

Alternative Motor Fuels Act

encourages—

(1) the development and widespread use of methanol,

ethanol, and natural gas 

as transportation fuels by

consumers; and,

(2) the production of methanol,

ethanol, and natural gas 

powered motor vehicles.

The Act directs the Secretary 

of Energy to cooperate with 

other agencies to conduct a study

of alternative-fueled vehicles,

which shall address—

(i) the performance of such

vehicles, including performance in cold weather and at

high altitude;

(ii) the fuel economy, safety, and

emissions of such vehicles;

and,

(iii) a comparison of the operation and maintenance costs

of such vehicles to the operation and maintenance costs

of other passenger automobiles and light-duty trucks.

The Act also directs the Secretary

of Energy to provide a report on

this study to the Committees 

on Commerce, Science and

Transportation and Governmental

Affairs of the Senate, and to the

Committee on Commerce of the

House of Representatives, within

one year after the first such vehicles are acquired, and annually

thereafter.
• The Environmental Protection

Agency sets regulations for emissions and defines standard methods for measuring those emissions.

• Original equipment manufacturers—such as General Motors,

Chrysler, Ford, Detroit Diesel

Corporation, and Cummins—

design and modify engines and

vehicles to operate on alternative

fuels. They also help test the

engines and vehicles and collect

data, which they send to the

Alternative Fuels Data Center.

• Several municipal transit agencies

take part in the transit bus program, maintaining, refueling, and

repairing buses that run on alternative fuels. They then forward

their records on transit bus operation and maintenance to the

Alternative Fuels Data Center. The

transit agencies also cooperate

with test laboratories that visit

their facilities to measure the

emissions and fuel economy of

the transit buses.

• Some municipalities cooperate 

in the program for testing heavyduty vehicles. Most are interested

in exploring options to relieve pollution, and thus help prove and

test the vehicle. As an example of

municipal applications, garbage

trucks are operated and maintained that run on alternative fuels.

Information on these vehicles is

forwarded to the Alternative Fuels

Data Center for compilation.

• Various Federal agencies also

cooperate with the Department of

Energy and the General Services

Administration by planning the

purchase of alternative fuel vehicles for their fleets and using

some of these vehicles in the 

test programs.

• The program for heavy-duty vehicles collects data from two companies that use alternative fuel

delivery vans in their commercial

fleets.

• Private test laboratories in several

states have contracted with the

Department of Energy to test the

emissions and fuel economy of

vehicles being used in the program. They use dynamometers 

to perform standardized tests; 

collect, analyze, and reduce the

data; and send the data to the

Alternative Fuels Data Center for

compilation and further analysis

and reduction.

• West Virginia University staff

members travel to the various

municipalities, taking part in the

programs for heavy-duty vehicles

and transit buses. The university

uses its transportable chassis

dynamometer to measure the

emissions and fuel economy of

the trucks and transit buses.

• Drivers of many of the test 

vehicles gather data on refueling,

mileage in real-world situations,

and problems encountered.

16

Background
Overview

The Federal light-duty vehicle evaluation program studies emissions,

vehicle performance, and fuel economy on passenger cars, minivans,

and light vans and trucks that operate 

on alternative fuels. This effort is

focused on meeting the requirements

of section 400 AA of the Energy

Policy and Conservation Act (the

Act). At the Federal level, the

General Services Administration, in

cooperation with the Department of

Energy, purchases alternative fuel

vehicles from the original equipment

manufacturers under the requirements of the Act, and provides such 

vehicles throughout the Federal fleet.

A number of the General Services

Administration’s vehicles are 

included in the light-duty vehicle

evaluation program.

U.S. automobile manufacturers currently provide light-duty vehicles that

operate on compressed natural gas 

or alcohol fuels (85 percent ethanol

and 85 percent methanol). Vehicles

designed to operate on compressed

natural gas can be “dedicated,” meaning they can only be operated on 

that fuel, or “bi-fuel.” The bi-fuel

compressed natural gas vehicles are

equipped to carry both gasoline and

natural gas, and can switch between

operation on the two fuels.

A number of vehicle design modifications are required to enable the

various vehicle models to operate on

a gaseous fuel. The changes include

replacing the fuel tank with highpressure gas cylinders, installing a

new fuel injection system, changing

the engine to make it compatible

with the gaseous fuel, and adding

other equipment related to fuel 

management, such as pressure 

relief devices.

All compressed natural gas vehicles

in the General Services Administration fleet, and included in 

the light-duty vehicle evaluation 

program, are dedicated vehicles.

In contrast, the

alcohol-fuel

vehicles in the

Federal fleet

are also known

as “flexiblefuel” vehicles.

As implied in 

its name, a

flexible-fuel

vehicle can 

run on gasoline

alone or on

various blends

of alcohol 

and gasoline,

depending on the vehicle design, up

to a maximum of 85 percent ethanol

or methanol. Relatively minor

design modifications are needed to

turn a standard gasoline vehicle into

one that can operate on an alcohol

fuel. Changes include using alcoholresistant materials in the fuel system, adding a fuel sensor, and

This minivan runs on compressed 

natural gas.

17

Light-Duty

Vehicles

Photo by Warren Gretz, NREL/PIX 03314
18

Figure 5. Locations of light-duty

vehicles in the 1995 evaluation fleet

Figure 4. Light-duty vehicles in 

the 1995 evaluation fleet

replacing the engine microprocessor

with one designed to control the

varying fuel blends. All alcohol

vehicles currently in the Federal

light-duty vehicle evaluation program are flexible-fuel vehicles.

Based on its budget, and

on vehicle availability,

the General Services

Administration purchases

as many alternative fuel

vehicles as possible for its

annual vehicle replacement

program. These vehicles

are leased to Federal agencies and their contractors

for normal Federal service.

In addition to its alternative fuel vehicle purchase

requirements, the Act requires various data to be collected from a sample of vehicles in the Federal fleet.

The number of alternative fuel vehicles in the Federal fleet has grown 

to nearly 20,000. For cost effectiveness, and to minimize the impact on

day-to-day government operations,

data are collected only on a sample

of this number. The light-duty vehicle program is currently collecting

data from 337 vehicles that operate

on one of the alternative fuels, plus 

146 vehicles that operate only on

gasoline (the control group). The

number of test vehicles in the program fueled with each of the alternative fuels is depicted in Figure 4. 

The sample includes different vehicle models located at various sites

around the country (see Figure 5) 

to allow the program to assess the

impact of higher altitudes on emissions and the impact of climatic 

conditions on various aspects of

vehicle performance.

The automobile manufacturers’ alternative fuel vehicle offerings have

been altered each model year. To

keep up with vehicle design changes

and technical advances, the lightduty vehicle test program adds new

models to the data collection effort

each year. New models added in 

program year 1995 include the 

1995 Dodge Caravan, a dedicated

compressed natural gas vehicle, and

the 1995 Dodge Intrepid, a flexiblefuel vehicle operating on 85 percent

methanol.

The General Services Administration

has followed a policy of removing

passenger cars from service after

three years, and vans and trucks 

after six years. In accordance with

this policy, some 1992 Chevrolet

Luminas operating on ethanol were

removed from the program in 1995.

Fourteen of these vehicles continue

in service. Additional modifications

Light-Duty Vehicles

M65-B034404

M65-B034405
19

Figure 6. Mileage accumulation 

on light-duty vehicles in the 

demonstration program

were made to the test fleet in 1995 to

improve the overall program design

and to more adequately reflect available vehicle models, as well as usage

of each alternative fuel.

As the light-duty vehicle evaluation

program progresses and evolves each

year, experience with alternative fuel

vehicles continues to grow. This

growth in experience is evidenced 

by the number of cumulative miles

traveled by all vehicles in the program over time (see Figure 6).

In addition, data are collected 

directly from vehicle drivers, the

General Services Administration,

and emissions laboratories. Drivers

report mileage, fuel usage, and performance problems. Maintenance 

and repair data are extracted from

General Services Administration

records. Periodically, as vehicles

reach various mileage levels, a 

subset of the vehicles is removed

from service for emissions testing.

Laboratories approved by the

Environmental Protection Agency

perform these tests.

The following sections summarize

information obtained from the analysis of light-duty vehicle data through

August 1995. Included are discussions on emissions, performance and

reliability, fuel economy, and cost.

Light-Duty Vehicles

B20 = 20 percent biodiesel blend

B35 = 35 percent biodiesel blend

B100 = neat biodiesel

CBD = Central Business District

CNG = Compressed natural gas

CO = Carbon monoxide

E50 = 50 percent ethanol

E85 = 85 percent ethanol

E93 = 93 percent ethanol, 5 percent 

methanol, and 2 percent kerosene

E95 = 95 percent ethanol

g/mile = grams per mile

HC = Hydrocarbons

LNG = Liquefied natural gas

M50 = 50 percent methanol

M85 = 85 percent methanol

M100 = 100 percent methanol

NMHC = non-methane hydrocarbons

NOx = Oxides of nitrogen

OMNMHCE = Organic material nonmethane hydrocarbon equivalent

PM = Particulate matter

RF-A = Industry average standard 

unleaded test gasoline

RFG = Reformulated gasoline

WVU = West Virginia University

Abbreviations

M65-B034406
20

Emissions

Emissions measurement is the single

most comprehensive part of the test

program for light-duty vehicles. The

effort undertaken in the Federal program is also the most extensive and

carefully controlled study of emissions of alternative fuel vehicles in

the world. The data collection activities, which are essential to fully

ascertain the long-term emissions 

of light-duty vehicles operating on

alternative fuels, are divided into 

two parts: Phase I and Phase II.

Phase I Emissions Testing

Phase I testing began in 1991 and

lasted through 1994. Eighteen vehicles were tested during this phase:

seven flexible-fuel Luminas, two

gasoline Luminas, seven flexible-fuel

Tauruses, and two gasoline Tauruses.

Each vehicle was tested at odometer

readings of approximately 4,000 and

10,000 miles, and subsequently at

approximate 10,000-mile intervals.

Nationally recognized facilities 

tested the vehicles using chassis

dynamometers (see sidebar, page 21)

to measure exhaust emissions

according to the Federal Test

Procedure—Code of Federal

Regulations, Title 40, Part 86,

Emissions Certification and Test

Procedures. Testing on these vehicles

was concluded when the General

Services Administration removed 

the vehicles from its fleet.

The Third Annual Report to

Congress presented the detailed

emissions results from Phase I.

Because of the small number of

vehicles tested, the availability of

only 85 percent methanol vehicles,

and the variability of the results

obtained, the conclusions presented

were limited. Phase II was designed

to build on information obtained in

Phase I.

Phase II Emissions Testing

To obtain results from a wider range

of alternative fuels at a higher level

of statistical reliability, the number

and type of vehicles tested were

greatly increased. In addition, a full

suite of speciated exhaust emissions

results was obtained on approximately 15 percent of these vehicles

(see sidebar on page 22).

For Phase II, a competitive procurement was used to select the privately

owned laboratories that were to 

Light-Duty Vehicles

Reformulated Gasoline

Spurred by the need for cleaner air and lower vehicle emissions, and

working in concert with the automotive industry, refiners created a

cleaner burning gasoline late in the 1980s. The term “reformulated

gasoline” was coined in 1989 in response to proposals to include clean

fuels requirements in the Clean Air Act Amendments. Today, the sale

of reformulated gasoline is mandated in the nine smoggiest cities in the

country, plus any cities that voluntarily opt in to the program.

Compared to standard gasoline, reformulated gasoline has a lower

organic sulfur content, reduced aromatic concentrations, and a lower

vapor pressure. It also has added oxygenates, which reduce carbon

monoxide emissions while improving the octane quality of the gasoline. The most common oxygenates are ethanol, methyl tertiary butyl

ether (a methanol-based ether), and ethyl tertiary butyl ether (an

ethanol-based ether).

To compare alternative fuels to clean-burning gasoline, reformulated

gasoline was used as the base case in the light-duty emissions study.

Both the State of California and the Federal Government have issued

standards for reformulated gasoline. California-certified reformulated

gasoline is used for the emissions testing presented in this report.
21

Light-Duty Vehicles

Emissions Testing Procedures

Before testing begins, the laboratory puts each vehicle through a detailed preconditioning procedure. This

ensures that the vehicle is running only on the test fuel and that each car tested has the same recent driving history. The vehicle is then allowed to cool for 12 to 36 hours before testing. The Federal Test Procedure includes

three tests: an evaporative emissions test while the vehicle is cold, a tailpipe emissions test while it is going

through a driving cycle, then another evaporative emissions test after it has gone through the driving cycle and is

at operating temperature.

For the evaporative emissions tests, operators put the vehicle in a sealed enclosure and measure the hydrocarbons that leak from the vehicle. Tailpipe emissions are measured while the vehicle is on a chassis dynamometer,

a system that uses rollers to simulate driving conditions within a laboratory. This tests lasts about 40 minutes.

Beginning with a cold start, a driver closely follows a predetermined speed versus time curve while the

dynamometer puts varying loads on the tires. This simulates the loads on a car during actual driving. After about

22 minutes, the driver turns the vehicle off for 10 minutes, restarts it, and follows another speed versus time

curve while the dynamometer again varies the load on the tires. During the test, the system automatically 

measures emissions and fuel economy.

Immediately following

the first round of testing,

the laboratories subjected

the vehicles to an inspection and maintenance

240 procedure to test

emissions. This is a chassis dynamometer test

similar to the Federal

Test Procedure, except

that it lasts for only four

minutes. Originally

designed for private

vehicles, this test was

done with the vehicle at

operating temperature

because cars were

warmed up when they

came in for emissions

testing. To determine the

value of the inspection

and maintenance 240 test

for low-emissions alternative fuel vehicles, the

program correlated its

results with those of the

40-minute test.

With a chassis dynamometer, the drive wheels of a test vehicle are supported by rollers that

simulate driving conditions. Fuel economy and emissions are measured while driving on

the dynamometer.

Photo by Warren Gretz, NREL/PIX 03322
An exhaust sample being connected to

a gas chromatograph for a detailed

hydrocarbon analysis

perform emissions testing. The selection criteria included technical expertise (including experience in testing 

alternative fuel vehicles), proximity

to the test fleets, and cost.

Environmental Research &

Development was selected to test

vehicles from the Washington, D.C.,

and New York regions; Automotive

Testing Laboratories, Inc., to test

vehicles from the Detroit and

Chicago regions; and ManTech

Environmental to test vehicles from

the Denver region. The Denver test

site allows for a high-altitude comparison on emissions performance.

The laboratories test the vehicles at

the same approximate odometer

readings as in Phase I, using chassis

dynamometers and the Federal Test

Procedure. They also use the

22

Light-Duty Vehicles

Hydrocarbon Speciation

All hydrocarbons are not created equal. Although the Environmental

Protection Agency has specific emissions certification standards for

hydrocarbons, there is also a wide array of other compounds in vehicle

exhausts that are classified as hydrocarbons. Some hydrocarbons, such

as benzene and 1,3-butadiene, are considered to be more toxic than others. Individual hydrocarbon compounds are also assigned reactivity factors, which indicate their likelihood of reacting with oxides of nitrogen

in the atmosphere to form smog. Other compound gases—known as

aldehydes and alcohols—are oxygenated derivatives of hydrocarbons.

They are of interest because they may directly affect human health, or

may contribute to the formation of ozone.

The Environmental Protection Agency’s emissions regulations on

hydrocarbons take some of these factors into account. For instance,

because methane has a very low photochemical reactivity factor, the

hydrocarbon certification standards are written in terms of non-methane

hydrocarbons. In the case of alcohol fuels (methanol and ethanol), the

most recent hydrocarbon regulations include non-methane hydrocarbons, plus a fraction of the aldehydes and alcohols. This value is known

as organic material non-methane hydrocarbon equivalent.

The Federal emissions testing program is furthering the understanding of the differences in

hydrocarbons from various alternative and conventional fuels by measuring and evaluating the

relative levels of aldehydes, alcohols, and

methane in the exhaust emissions. This analysis

requires special equipment—gas chromatographs, liquid chromatographs, and alcohol

impingers—which are not usually found in a

basic emissions test facility.

The most comprehensive analysis of hydrocarbons is called hydrocarbon speciation. In this

analysis, hundreds of hydrocarbon compounds

found in the vehicle emissions are quantified.

The results from hydrocarbon speciation analysis

are being used in the Federal emissions testing program to compare the

relative potential for hydrocarbon emissions from the various fuels to

form smog, based on reactivity factors specified by the California Air

Resources Board. This information is also being used as input for the

research and development efforts at the National Renewable Energy

Laboratory, which is involved in modeling atmospheric reactions.

Photo by Warren Gretz, NREL/PIX 03321
Environmental Protection Agency’s

inspection and maintenance 240 test

procedure (see sidebar, page 21).

Phase II also differs from Phase I in

that several types of vehicles are now

being tested: flexible-fuel vehicles

capable of running on 85 percent

ethanol or 85 percent methanol; dedicated vehicles running on compressed natural gas; and control vehicles running on gasoline. In the

emissions testing program, reformulated gasoline, California Phase II

Certification Fuel (see sidebar on

page 20), is used as the basis of

comparison to alternative fuels.

To compare emission levels at various fuel-mixing ratios, flexible-fuel

vehicles have been tested on three

fuels: a mixture containing 85 percent alcohol and 15 percent reformulated gasoline, a mixture containing

50 percent alcohol and 50 percent

reformulated gasoline, and 100 percent reformulated gasoline. The

selection of alcohol used in the mixtures depends on whether the vehicle

is designed to run on ethanol or

methanol.

Vehicles dedicated to operating on

compressed natural gas are tested on

fuel blended from tightly controlled

constituent gases (93.05 percent

methane, 3.41 percent ethane, 0.65

percent propane, etc.). This test fuel

is designed to represent an industryaverage product.

Exhaust emissions from vehicles

operating on alternative fuels and

reformulated gasoline are compared

to the Federal standards, which 

mandate the maximum allowable

levels on a grams per mile basis. The

regulated components are hydrocarbons, carbon monoxide, and oxides

of nitrogen.

Between 1994 and 1998, new standards are being phased in. These

standards regulate total hydrocarbons

and non-methane hydrocarbons for

gasoline vehicles, and organic material non-methane hydrocarbon equivalents (which include aldehydes and

unburned alcohol) for alcohol vehicles. Methane is not included in the

hydrocarbon regulations because it 

is non-reactive and does not add to

photochemical smog. However,

methane is considered to be a highly

potent greenhouse gas—far more

active than carbon dioxide.

By 1998, the previous standards,

known as Tier 0, will be completely

replaced by the new standards,

known as Tier 1. Figure 7 shows the

Tier 0 and Tier 1 emissions standards

for light-duty cars and trucks.

23

Light-Duty Vehicles

Figure 7. Tier 0 and Tier 1 emissions

standards for light-duty vehicles. 

(Note that NMHC is not regulated 

in the Tier 0 standards.)

M65-B034407
Phase II Preliminary 

Emissions Results

As of August 1, 1995, 803 emissions tests had been conducted on 

215 alternative fuel vehicles, and 

287 emissions tests had been conducted on 175 gasoline control vehicles. These totals include tests on

multiple fuels, and repeat tests on

individual vehicles. Table A-1 in the

Appendix lists the numbers of each

vehicle model tested and the number

of tests conducted on each model. 

As part of the experimental design,

each alcohol fuel vehicle is tested 

on each of three fuel combinations

every time the vehicle is brought in

for testing.

The first round of testing on the 

initial Phase II vehicles is complete,

as is about half of the second round.

The first round of testing was also

begun in 1995 on three new vehicle

models representing the latest alternative fuel offerings from Chrysler,

Ford, and General Motors. An extensive engineering and statistical

analysis on the first-round data is in

progress. The results of this analysis

will be subjected to peer review by

experts in the alternative fuels and

automotive industries. Some preliminary findings are presented below.

Results from Methanol Dodge Spirits

The most extensive testing to 

date has been conducted on Dodge

Spirits: 319 emissions tests on 

76 methanol flexible-fuel models,

and 126 tests on 72 standard gasoline

models. As shown in Figure 8, the

preliminary average emissions from

these four-cylinder passenger cars

are all below the Tier 1 standards for

non-methane hydrocarbons, carbon

monoxide, and oxides of nitrogen.

On average, flexible-fuel Dodge

Spirits tested on 85 percent methanol

or 50 percent methanol showed a

modest reduction (approximately 

10 percent) in non-methane hydrocarbons in comparison to the corresponding values obtained on reformulated gasoline. The Dodge Spirits

emitted very similar levels of carbon

monoxide and oxides of nitrogen

when tested on alcohol compared to

the same levels emitted when tested

on reformulated gasoline.

Because non-methane hydrocarbons

represent a class of pollutants rather

than one specific compound, further

analysis is required. To provide the

necessary additional information, a

full hydrocarbon speciation analysis

was performed on approximately 

15 percent of the exhaust measurements from Dodge Spirits (see sidebar on page 22). Preliminary results

show that the hydrocarbon profiles

for the alcohol fuels are much 

24

Light-Duty Vehicles

Figure 8. Emissions results

from methanol flexible-fuel 

Dodge Spirits

M65-B034408
25

Light-Duty Vehicles

different than those for reformulated

gasoline. For instance, the average

levels of benzene and 1,3-butadiene

(hydrocarbon compounds considered

to be air toxics) are far lower than

the corresponding levels from the

reformulated gasoline. On the other

hand, the average formaldehyde

emissions from the methanol tests

were substantially higher than those

from the reformulated gasoline.

Finally, hydrocarbon speciation

allows for a relative comparison to

be made between fuels on the potential for exhaust hydrocarbons to react

in the atmosphere to form ozone.

Early results of this type indicate that

the exhaust hydrocarbons emitted

from the flexible-fuel Dodge Spirits

have, on average, approximately 

40 percent lower ozone-forming

potential than those emitted from 

the same vehicles operating on reformulated gasoline.

Results from Ethanol 

Chevrolet Luminas

As of August 1, 1995, 101 emissions

tests had been conducted on 25 variable-fuel Chevrolet Luminas, and 

48 tests had been conducted on 24

standard gasoline Chevrolet Luminas.

The preliminary average emissions

from the six-cylinder Chevrolet

Luminas were all below the Tier 1

emissions standards for non-methane

hydrocarbons, carbon monoxide, and

oxides of nitrogen (see Figure 9).

On average, the regulated exhaust

emissions from the ethanol tests 

on the variable-fuel vehicles were 

15 percent to 20 percent lower than

those from the reformulated gasoline

tests on the same vehicles. Because

the three test fuels (85 percent

ethanol, 50 percent ethanol, and

reformulated gasoline) for these

vehicles were blended to have 

similar vapor pressures (nominal 

7 pounds per square inch), very 

little difference in average evaporative emissions was observed.

Preliminary results from full hydrocarbon speciation of exhaust measurements on approximately 15 percent of the Chevrolet Luminas show

a substantially different hydrocarbon

profile between ethanol and reformulated gasoline. Average emissions 

of air toxics, such as benzene and

1,3-butadiene, were approximately 

80 percent lower from the ethanol

tests than from the reformulated

gasoline tests. Ethanol formaldehyde

emissions were up slightly on average, and ethanol acetaldehyde emissions were far higher, on average, in

comparison to the corresponding

average emissions from the reformulated gasoline tests. The potential for 

the hydrocarbon emissions to 

form ozone, expressed in average

Figure 9. Emissions results from

ethanol flexible-fuel Chevrolet Luminas

M65-B034409
26

Light-Duty Vehicles

milligrams of ozone per mile, was

approximately 25 percent lower, on

average, from the ethanol tests than

from the reformulated gasoline tests.

Results from Dodge B250 Vans

As of August 1, 1995, 66 emissions

tests had been performed on 52 dedicated compressed natural gas Dodge

B250 vans, and 60 tests had been

performed on 47 standard gasoline

Dodge B250 vans (the control

group).

On average, preliminary analysis

from the first round of testing indicates notably lower emissions of regulated exhaust pollutants from the

compressed natural gas vehicles, in

contrast to those produced by the

standard gasoline vehicles. Nonmethane hydrocarbons were approximately 70 percent lower, carbon

monoxide was approximately 

40 percent lower, and oxides of

nitrogen were approximately 

30 percent lower, on average, than

the corresponding levels observed

for the standard gasoline vehicles.

The average results, along with the

appropriate Federal standards, are

depicted in Figure 10.

To address concerns over natural gas

fuel system leaks, an enhanced test

procedure for CNG vehicles was

developed. A leak test similar to the

standard evaporative test performed

on all liquid fuel vehicles (see sidebar on page 21) was added.

The leak tests performed on the

compressed natural gas vehicles

showed that some vehicles did, in

fact, have small fuel leaks, but the

amounts were comparable to, or

lower than, the total hydrocarbons

evaporating from the standard 

gasoline vehicles. While the vehicle

manufacturer has been informed of

this finding, the size of the leaks is

not expected to pose a safety risk.

The full speciation of exhaust hydrocarbons from four of the compressed

natural gas vehicles and five of the

gasoline vehicles indicates that the

compressed natural gas hydrocarbon

profile is very different from that of

reformulated gasoline. On average,

emissions of toxic hydrocarbons,

such as benzene and 1,3-butadiene,

were approximately 95 percent lower

in the tests on compressed natural

gas vehicles than in the tests on

reformulated gasoline vehicles. The

average formaldehyde emissions

were 10 percent higher in the tests

on compressed natural gas vehicles

than in the tests on reformulated

gasoline vehicles, but one of the four

compressed natural gas vehicles had 

Figure 10. Emissions results from gasoline and compressed natural gas Dodge

B250 vans

M65-B0344010
much higher formaldehyde emissions than all the others, which

increased the overall average. On

average, formaldehyde emissions

from the compressed natural gas

vans would otherwise have also been

lower than those from reformulated

gasoline vans. The potential for

hydrocarbon emissions to form

ozone, expressed in average milligrams of ozone per mile, was

approximately 80 percent lower in

the tests on compressed natural gas

vehicles than in the tests on reformulated gasoline vehicles.

Results from Methanol 

Ford Econoline Vans

The first round of testing of

methanol flexible-fuel Ford

Econoline vans was completed during 1995. This included 62 tests on

16 flexible-fuel vans and 23 tests on

18 standard gasoline vans. The average exhaust emissions results from

these full-size passenger vans were

all below the respective Tier 1 standards (see Figure 11). On average,

the exhaust emissions from the 

flexible-fuel van tested on methanol

were lower than or similar to the

exhaust emissions of those same

vehicles when tested on reformulated

gasoline. Non-methane hydrocarbons

were approximately 10 percent

lower, carbon monoxide was approximately 30 percent lower, and oxides

of nitrogen were about the same.

Full speciation of the exhaust hydrocarbons from approximately 15 percent of the tests on Ford Econolines

indicates, once again, that the

methanol hydrocarbon profile is 

very different than the reformulated

gasoline hydrocarbon profile. On

average, emissions of toxic hydrocarbons, such as benzene and 1,3-butadiene, were between 60 percent and

80 percent lower in the methanol

tests than in the reformulated gasoline tests on the same vehicles. The

average formaldehyde emissions

were approximately five times higher

in methanol tests than in the reformulated gasoline tests on the same vehicles. The potential for hydrocarbon

emissions to form ozone, expressed

in average milligrams of ozone per

mile, was approximately 50 percent

lower in the methanol tests than in

the reformulated gasoline tests on the

same vehicles. The relative difference

between the methanol and reformulated gasoline hydrocarbon profiles

obtained from the exhaust emissions

of these vehicles is comparable to the

corresponding difference between the

methanol and reformulated gasoline

hydrocarbon profiles obtained from

the exhaust emissions of flexible-fuel

Dodge Spirits.

27

Light-Duty Vehicles

Figure 11. Emissions results from

methanol flexible-fuel Ford Econoline

vans

M65-B0344011
28

Light-Duty Vehicles

Performance and Reliability

The light-duty vehicle evaluation

program has been collecting information on the performance and reliability of alternative fuel vehicles, and

their standard gasoline counterparts,

for nearly four years. Two types of

information are being collected and

evaluated: driver complaints about

various aspects of vehicle performance, and unscheduled repair 

data, which indicate general vehicle

reliability.

Drivers were asked to report whether

they experienced any of a number of

common performance-related problems when they drove their vehicles.

To date, complaints have included

hard-starting vehicles, illumination

of check-engine light indicators,

poor idle quality, hesitation, lack 

of power, engine ping, and vehicle

stalling (after starting or in traffic).

As expected, drivers reported more

performance problems, on average,

for the early-model alternative fuel

vehicles than for the later-model

vehicles (see Figure 12). From the

drivers’ perspective, the performance

of alternative fuel vehicles in general

has improved with time, and it

appears to be approaching the

accepted performance level of 

gasoline vehicles.

Unscheduled repairs, which were

also relatively frequent on the early

model alternative fuel vehicles,

are much less so on later models. 

Figure 13, which shows a comparison of average unscheduled repairs

over time for compressed natural gas

and methanol vehicles, is indicative

of this decline. Such improvements

Figure 13. Reported unscheduled

repairs (reported with less than 

10,000 miles on vehicles)*

* Does not include data from 1992 compressed natural gas Chevrolet pickup trucks,

which were recalled.

Figure 12. Driver complaints by

model year (reported with less than

10,000 miles on vehicles)*

* Does not include data from 1992 compressed natural gas Chevrolet pickup trucks,

which were recalled. Also, there were no 

driver complaints on the single 1992 

gasoline-powered model in the program.

M65-B0344012 M65-B0344013
in the unscheduled repair record 

are believed to result from a combination of vehicle design changes and

increased familiarity with alternative

fuel vehicles on the part of repair

technicians. In most cases, fuelsystem-related repairs are covered 

by the manufacturer’s warranty, so

excess downtime is the real cost to

fleet operators.

In the future, the number of repairs

may be further reduced as vehicle

designs continue to be optimized,

and as replacement parts become

more widely available. Conversely,

quantity stocking of replacement

parts will become more costeffective as the number of alternative fuel vehicles increases.

Fuel Economy

Testing of vehicles on a chassis

dynamometer and analysis of refueling records from actual daily use

have resulted in two sources of fuel

economy information. In both

instances, the calculation of fuel

economy to reflect alternative fuel

consumption is corrected to “equivalent gallons” of gasoline. One gallon

of unleaded gasoline has the same

average energy content as 1.77 gallons of 85 percent methanol, or 

1.42 gallons of 85 percent ethanol,

with the average energy content of

unleaded gasoline being 115,000 Btu

per gallon (see Figure 14).

Fuel economy information is

obtained on each vehicle at the time

of emissions testing on a chassis

dynamometer. The fuel economy

tests generate a single number that 

is based on a specific “city” driving

cycle. Closely controlling the fuel

and operating conditions, the test

laboratories take measurements on 

a number of similar vehicles, which

are then averaged to obtain a single

value. These average values are

shown as points in Figure 15.

Actual in-use fuel economy is also

calculated using refueling records

maintained in the U.S. Department

of Energy’s Alternative Fuels Data

Center at the National Renewable

Energy Laboratory. During actual

use, vehicle fuel economy varies

considerably because of individual

driving style and a number of other

factors, such as the type of driving

(stop-and-go city driving, highway

driving, deliveries, or a combination

of all three), climate, and altitude.

Determination of in-use fuel economy is further complicated by the

fact that alcohol vehicles, being 

flexible-fuel vehicles, may be fueled

with either alcohol fuel or gasoline at

any particular refueling. The gasoline

29

Light-Duty Vehicles

Figure 14. Energy content 

comparison

M65-B0344014
will mix with the alcohol fuel left in

the tank to create a unique blend. To

compensate for this situation, in-use

fuel economy calculations are based

only on instances for which alcohol

fuels are used in three consecutive

refuels.

A range of results for in-use fuel

economy is shown as a line in 

Figure 15 for various vehicle models

in the light-duty evaluation program.

In most cases, the figure shows that,

on an equivalent energy basis, vehicles operating on alternative fuels

tend to achieve levels of fuel economy similar to those achieved by

standard vehicles operating on 

gasoline.

Cost

Obviously, there are costs associated

with owning and operating any lightduty vehicle. Total vehicle cost

includes initial acquisition, insurance,

maintenance, fuel, and oil. The distribution of costs for operating a gasoline-fueled fleet vehicle is depicted in

Figure 16. This distribution represents cost over the life of a vehicle,

with each component being a composite average for fleets across the

United States. These average costs

are based on vehicles having been in

service an average of 27 months, and

having cost an average of $15,000 

at the time of initial acquisition.

Differences such as self-insurance for

government and some private fleets,

and how some types of maintenance

and repairs are logged, affect the distribution of vehicle costs.

Comparable distributions are likely

to be different for a fleet of alternative fuel vehicles. Differences in initial acquisition costs, depreciation

costs, and fuel and maintenance

costs are expected to affect the overall cost of operating alternative fuel

vehicles. For a typical gasolinefueled fleet, the items included in

operating costs (fuel, oil, maintenance, and tires) represent less than

27 percent of the total costs associated with vehicle operation and ownership. The corresponding percentage of total cost that operating cost

represents for alternative fuel vehicles is expected to be somewhat

higher. However, even if fuel cost for

alternative fuel vehicles is 50 percent

more than for gasoline vehicles,

operating costs would increase to 

30

Light-Duty Vehicles

Figure 15. Fuel economy by 

vehicle type

M65-B0344015
only about 33 percent of the total.

The factors that contribute to higher

owning and operating costs for alternative fuel vehicles are discussed in

more detail below.

Incremental Acquisition Cost

The information available to date 

on alternative fuel vehicles in the

Federal light-duty vehicle evaluation

program indicates the cost of acquiring those vehicles ranges up to 

25 percent higher than the cost of

comparable gasoline vehicles. This

price difference is primarily due to

the equipment modifications necessary to enable a gasoline model to

operate on an alternative fuel. For

flexible-fuel vehicles in particular,

the price increases range between $0

and $800, depending on the manufacturer. Most of this increase is due

to the special fuel system materials

required for the alcohol fuels.

For compressed natural gas vehicles,

the price increase can be as much as

$5,000 per vehicle. The bulk of this

cost increase is attributable to the

different fuel storage and intake systems that are necessary to accommodate a gaseous fuel. As the demand

for compressed natural gas vehicles

increases, the manufacturers will

continue to optimize their vehicle

designs, which should result in a

reduction in the price differential.

One automobile manufacturer

recently announced a reduction of

$750 in the price of its most popular

compressed natural gas model.

As is the case for standard gasoline

vehicles, the acquisition price for any

alternative fuel vehicle will vary

depending on the model and options

desired. Also, as the initial purchases

of alternative fuel vehicles expand,

a resale market may begin to grow,

with the expectation that some of the

additional acquisition costs may be

recoverable.

Comparative Fuel Costs

Fluctuations in wholesale prices,

and different state and local tax

structures, result in a wide variation

in fuel costs across the country.

Wholesale fuel prices vary as much

as $0.20 per equivalent

gallon among cities. State

and local taxes can add as

much as $0.40 per equivalent gallon in certain

locales. Some states and

communities offer incentives to purchasers of

alternative fuels that

include reduced tax rates,

taxing only the gasoline

portion of an alcohol fuel,

and taxing all fuels at the

same rate as gasoline.

In September 1995, retail pump

prices across the country ranged

from approximately $1.60 to $1.87

per gallon of 85 percent ethanol,

$2.00 to $2.88 per gallon of 85 percent methanol, $0.60 to $1.14 per

gallon of compressed natural gas,

and $1.10 to $1.18 per gallon of regular unleaded gasoline. These price

ranges account for differences in fuel

energy content and reflect the alternative fuel cost on a per-gallon-ofgasoline-equivalent basis. They also

account for differentials attributable

to local variations in taxes or fuel

purchasing incentives. 

31

Light-Duty Vehicles

Figure 16. Distribution of operating

costs for composite U.S. fleet

Source: PHH Vehicle Management Services

M65-B0344016
There are a number of industry

sources, including Oxy-Fuel News,

21st Century Fuels, and New Fuels

Report, which track the wholesale

and retail prices of the various 

alternative motor fuels. The U.S.

Department of Energy’s Energy

Information Administration also 

produces weekly and monthly publications containing information on

fuel prices around the country. Many

state fuel purchasing incentives are

itemized in the Department of

Energy’s publication entitled Guide

to Alternative Fuel Vehicle Incentives

and Laws.

Variations in fuel costs, as well as

variations in fuel economy for various vehicle models, result in a wide

range of fuel costs per mile driven.

The range of fuel costs per mile for

the alternative fuel and gasoline

vehicles in the Federal light-duty

evaluation program is shown in

Figure 17. For sedans in the program, the average cost per mile for

ethanol and methanol is somewhat

higher than for gasoline, but for

vans, compressed natural gas is competitive with gasoline in average cost

per mile. The actual cost per mile for

any specific vehicle is affected by

factors such as the driving cycle of

the vehicle, the driving style of the

operator, and the local price of fuel.

Comparative Oil Costs

Oil cost is a function of both price

and the frequency of oil change.

Because automobile manufacturers

recommend more frequent oil

changes for alcohol-fuel vehicles,

the oil cost for these vehicles is 

generally higher than for gasoline

vehicles. Typical oil costs are about

$0.013 per mile for alcohol-fuel

vehicles, and $0.007 cents per 

mile for gasoline vehicles. The 

manufacturer-recommended oilchange schedule is the same for

vehicles fueled with compressed natural gas and those fueled with gasoline. Therefore, assuming comparability of prices, these vehicles would

realize similar oil costs. All vehicles

in the Federal light-duty evaluation

program had their oil changed

according to the manufacturers’ recommended oil-change-interval

schedules.

Comparative 

Maintenance Costs

Most maintenance on General

Services Administration vehicles is

performed under warranty at no cost

to the fleet operator (except for lost

32

Light-Duty Vehicles

Figure 17. Range of fuel costs 

per mile (alternative fuel costs are

stated on the basis of equivalent 

gallons of gasoline)

M65-B0344017
time in service). Therefore, data on

the actual cost of maintenance, and a

summary of average maintenance

costs per mile, are not available. In

general, maintenance costs are

expected to be marginally higher for

alternative fuel vehicles than for

gasoline vehicles. One reason is that

parts cost more for models that are in

relatively limited production (which

is the case for most alternative fuel

vehicles). Also, experience with the

vehicles in the Federal light-duty

evaluation program indicates that

some maintenance costs are unique

to alternative fuel vehicles. Although

fuel pump and injector problems

were common for the early models,

they are decreasing as manufacturers

gain experience and improve the

overall vehicle design.

As previously noted, analysis of

information available to date indicates that the number of unscheduled

repairs (as opposed to the cost of

repairs) on alternative fuel vehicles

decreases with each new model year.

This evidence, along with growing

experience, increases the confidence

that in the long term, average maintenance costs for alternative fuel

vehicles will approach those of 

standard gasoline vehicles.

Summary

Sustained progress is being made

toward accomplishing the goals 

of the Federal light-duty vehicle

demonstration program. A substantial body of evidence pertaining 

to emissions, performance and 

reliability, fuel economy, and costs

has been accumulated.

The information collected to date

suggests that original equipment,

light-duty alternative fuel vehicles

emit fewer pollutants into the atmosphere than, and achieve fuel economy results similar to, their gasoline

counterparts. The available evidence

also points to extended improvements in light-duty alternative fuel

vehicle technology. In particular,

enhancements to vehicle designs

have led to performance and reliability levels approaching those of conventional gasoline vehicles. Finally,

the most current information indicates that the overall costs of owning

and operating light-duty alternative

fuel vehicles continue to exceed the

corresponding costs of owning and

operating light-duty gasoline vehicles. This difference, however, is

expected to diminish as the market

demand for alternative fuel vehicles

increases.

33

Light-Duty Vehicles
34
35

Figure 19. The number of transit buses

in the program operating on each type

of fuel

Overview

The Federal transit bus evaluation

program (section 400 CC of the

Energy Policy and Conservation Act)

is designed to provide a comprehensive study of the alternative fuels currently used by the transit bus industry. The program focuses on the

emissions levels, fuel economy,

reliability, and operating costs of 

the various fuels and engines.

To obtain the detailed information

necessary to make valid comparisons, transit agencies that meet the

following criteria have been selected

to participate in the program:

• The transit agency must have

alternative fuel buses that represent the most current technology

available

• The transit agency must have control buses that are identical to the

alternative fuel buses except for

the fuel they use

• The transit agency must be willing

to supply detailed data on the

buses for several years.

The following eight metropolitan

areas were selected for program participation: Houston, Texas; Miami,

Florida; Minneapolis, Minnesota;

New York, New York; Peoria,

Illinois, St. Louis, Missouri; Tacoma,

Washington; and Portland, Oregon

(see Figure 18). Transit buses used

by the transit agencies of these eight

municipalities are being operated,

and are undergoing a number of 

tests, on four different alternative

fuels—compressed natural gas,

liquefied natural gas, methanol,

and ethanol—plus B20, a blend of

20 percent biodiesel and 80 percent

conventional diesel fuel

(B20 is not considered by

the Department of Energy

to be an alternative fuel

under the Act). Figure 19

shows the numbers and

percentages of transit

buses in the program operating on each fuel type.

The goal of the Federal

transit bus evaluation program is to test emissions

and collect operating data

on a minimum of five

transit buses at each location running

on a single alternative fuel, as well

as a minimum of five standard transit

Transit Buses

Figure 18. The eight metropolitan areas

that currently participate in the Federal

transit bus evaluation program

M65-B0344018 M65-B0344019
buses running on diesel (the control

group). In St. Louis, however, five

transit buses operating on B20, a

biodiesel blend not considered to be

an alternative fuel under the Act, and

five transit buses operating on standard diesel are being tracked. Table

A-2 in the Appendix provides a summary of all the transit buses 

at the various sites included in the

evaluation program.

With regard to data collection and

dissemination, a subcontractor

obtains information on maintenance,

fuel usage, added oil, and various

costs from each transit agency. The

subcontractor then processes the

data, converts them into a standard

form, submits them to the U.S.

Department of Energy’s Alternative

Fuels Data Center at the National

Renewable Energy Laboratory, and

analyzes the results. The Alternative

Fuels Data Center then makes the

information available to the public

through reports, as well as a series of

database queries, all designed to present the information in a concise and

logical format.

In addition to the operating data collected on the demonstration transit

buses at each site, West Virginia

University personnel visit each location to conduct emissions tests on the

transit buses using the university’s

transportable chassis dynamometer

(shown in the photo to the left; discussion follows below). These data

are also processed and forwarded to

the Alternative Fuels Data Center for

analysis, retention, and dissemination.

The alternative fuel engines included

in the transit bus evaluation program

are:

• Detroit Diesel 6V92TA methanol

engine

• Detroit Diesel 6V92TA ethanol

engine

• Detroit Diesel 6V92TA pilot 

ignition natural gas engine

• Cummins L10G natural gas

engine.

36

Transit Buses

West Virginia University’s transportable chassis dynamometer

This colorful transit bus runs on

ethanol fuel in the Peoria area.

Photo courtesy of West Virginia University/PIX 03319 Photo courtesy of Greater Peoria Mass Transit District/PIX 03320
The biodiesel transit buses use 

B20 in an unaltered Detroit Diesel

6V92TA engine. Each engine has a

horsepower rating between 240 and

280. All transit buses are 35-foot or

40-foot models manufactured by

Mercedes, Flxible, Gillig, TMC,

or BIA.

Detroit Diesel Corporation and

Cummins have made extensive

efforts to develop heavy-duty engines

that run on alternative fuels and to

introduce them into the transit bus

market. The earliest of these engines

were placed in the field as demonstration units to validate the concept

of operation on alternative fuels, and

to identify areas of improvement.

Since that time, both companies have

enhanced their engines and emissions

control systems.

Emissions

With funding from the U.S.

Department of Energy, West 

Virginia University’s Department 

of Mechanical and Aerospace

Engineering designed and constructed a transportable chassis

dynamometer to test emissions levels

from heavy-duty vehicles. The portability of this chassis dynamometer

allows a large number of emissions

tests on transit buses and heavy-duty

vehicles to be conducted on site

around the country. Before the unit

was built, other options were considered, such as transporting vehicles to

stationary dynamometers, or removing engines and transporting them to

facilities. Both options were rejected

because of expense and vehicle

downtime.

West Virginia University maintains

an up-to-date description of the

dynamometer’s design and operating

characteristics, as well as all details

of the emissions test procedures.

Typically, this transportable chassis

dynamometer is set up on the

grounds of the test fleet or local transit agency, and heavy-duty trucks or

transit buses are tested using the fuel

resident in the vehicle at the time of

the test. The dynamometer may be

set up to operate inside or outside,

depending on the space available at

the transit agency. To test emissions

on the transit buses in the Federal

evaluation program, West Virginia

University uses the standard Central

Business District test cycle, a driving

cycle devised to simulate speeds,

loads, and conditions experienced by

transit buses during a typical route

through a city’s Central Business

District (see Figure 20).

During 1995, West Virginia

University personnel traveled to 

transit agency facilities in New York

City, Miami, Peoria, St. Louis,

Minneapolis, Tacoma, and Portland

to test transit buses included in 

the Federal evaluation program.

37

Transit Buses

Figure 20. Central Business District

chassis dynamometer driving cycle

M65-B0344020
Summaries of the results from emissions tests performed on 24 compressed natural gas, 10 methanol, 10

ethanol, and comparable numbers of

diesel buses (the control group) are

provided in the sections below.

Comparing exhaust emissions 

levels between heavy-duty vehicle

technologies is a complex and 

evolving matter. Both the engine certification and chassis dynamometer

testing have shown that alternative

fuels have the potential to substantially reduce emissions levels, but

emissions also may vary widely

depending on engine technology and

vehicle condition. Test results from

the most recent offerings of compressed natural gas and alcohol fuel

engines, suggest that emissions can

be reduced significantly. Although

efforts are continually being made to

include the latest technologies available in the Federal evaluation program, many transit buses tested over

the past several years represent early

versions of alternative fuel engines

that were originally part of either a

manufacturer’s demonstration project, or were deployed to help develop alternative fuel technology. Each

manufacturer has updated its engine

designs based on results from these

studies.

In general, the results of emissions

testing vehicles in the Federal transit

bus evaluation program are highly

variable. Early testing showed that

some of the alternative fuel transit

buses exhibited high levels of

hydrocarbons and carbon monoxide.

In cooperation with the engine manufacturers, it was discovered that

many of these vehicles were either

improperly tuned or had problems

with fuel injectors, catalytic converters, or mixing valves. Recently, dramatic reductions in hydrocarbons

and carbon monoxide emissions

were achieved on compressed natural

gas buses in Miami and Tacoma after

manufacturer representatives performed problem diagnosis on the

high-emitting vehicles and corrected

the problems they discovered.

The variability in hydrocarbons and

carbon monoxide notwithstanding,

alternative fuel transit buses appear

to be particularly well suited to

reducing emissions of particulate

matter and oxides of nitrogen. This

feature is quite important, as Federal

emissions standards for these components are becoming more stringent

(see Table 1). Representatives from

the heavy-duty engine manufacturers,

the U.S. Environmental Protection

Agency, and the California Air

Resources Board have signed a statement of principles aimed at reducing

emissions of oxides of nitrogen to

38

Transit Buses

Table 1. U. S. Environmental Protection Agency Heavy-Duty Engine

Emissions Certification Standards (in grams per brake horsepowerhour) for Urban Transit Buses

CO NOx HC PM

1991–92 15.5 5.0 1.3 0.25

1993 15.5 5.0 1.3 0.10

1994–95 15.5 5.0 1.3 0.07

1996–97 15.5 5.0 1.3 0.05

1998 15.5 4.0 1.3 0.05
2.0 grams per brake horsepower-hour

by the year 2004, while not lowering

the standards for particulate matter.

West Virginia University’s emissions

testing activities have helped to

underscore two very important

points. First, by participating in

demonstration programs, transit

agencies can play an important role

in developing technologies that will

help to improve air quality. Second,

the diagnosis and repair of high

emitters have shown that even

though the use of alternative fuels

may reduce emissions, engine technology and proper vehicle maintenance are also crucial factors.

Compressed Natural Gas

Most compressed natural gas transit

buses tested so far have been early

versions of the Cummins L10G

engine that were not certified by the

Environmental Protection Agency.

Cummins has since made several

improvements to enhance engine

performance and reduce emissions

levels. Later versions of this engine

have been certified by the California

Air Resources Board. Several L10G

engines used in New York City transit buses were upgraded to the certified configuration and tested in 1994.

For various exhaust constituents,

Figure 21 shows the average, minimum, and maximum emissions measured on transit buses equipped with

Cummins L10G engines. A comparison is shown between engines fueled

with compressed natural gas and

those fueled with diesel. Although

the data are somewhat scattered,

several general conclusions can 

be drawn. The most obvious result is

that emissions of particulate matter

are reduced to nearly zero in engines

fueled with compressed natural gas.

This is an important and attractive

feature of this fuel that reduces the

amount of black smoke emanating

from city transit buses. Figure 21

also shows that transit buses

equipped with the Cummins L10G

compressed natural gas engines certified by the California Air Resources

Board (CNG 260) exhibit lower carbon monoxide and oxides of nitrogen emissions, on average, than

either the original compressed natural gas transit buses (CNG 240) or

their diesel counterparts. Average

total hydrocarbon emissions from the

compressed natural gas transit buses

are higher than those for diesel transit buses. However, total hydrocarbon emissions from compressed 

39

Figure 21. Compressed natural gas

versus diesel transit bus emissions

(Cummins L10G engines)

* Total hydrocarbons.

** Early production engines, not certified by 

California Air Resources Board.

✝ Certified by California Air Resources 

Board.

✝✝ Particulate matter values were magnified 

10 times to show results on the same scale.

Transit Buses

M65-B0344021
natural gas vehicles typically comprise 90 percent to 95 percent

methane.

Environmental Protection Agency and

California Air Resources Board regulations are written in terms of nonmethane hydrocarbons, because

methane is considered to be non-reactive in the atmosphere (meaning that

it does not contribute to the formation

of photochemical smog). However,

methane is a potent greenhouse gas—

far more active than carbon dioxide.

Non-methane hydrocarbon emissions

from the compressed natural gas transit buses were not measured directly,

but they can be projected to be at

similar or lower levels than those for

transit diesel buses.

Later versions of the Cummins

L10G engine (CNG 260) have been

optimized for emissions control, and

the first tests on the newer engines

included in the Federal demonstration program show substantial 

reductions in the levels of carbon

monoxide and oxides of nitrogen.

On the early generation CNG 240

engines that were high emitters, a

cooperative effort with the engine

manufacturer was recently completed. West Virginia University’s

transportable chassis dynamometer

was used as a diagnostic tool to assist

the engine manufacturers in locating

problems. With this effort, relatively

small adjustments or repairs to the

air/fuel mixing valve achieved dramatic reductions in carbon monoxide

and oxides of nitrogen.

A key feature of the newest compressed natural gas engines is electronic “feedback” control of the

air/fuel ratio, which measures the

oxygen content in the exhaust. Plans

are being made now to include some

of these new-technology engines in

the Federal transit bus evaluation

program and to test their exhaust

emissions output as they are put 

into service.

Alcohol

The average, minimum, and 

maximum results from chassis

dynamometer emissions tests on

ethanol and methanol transit buses

powered by Detroit Diesel 6V92TA

engines are shown in Figure 22. The

results from these alternative fuel

transit buses are quite variable, both

from one vehicle to another and from

one site to another.

On average, transit buses fueled by

ethanol and methanol emit particulate matter levels similar to those

40

Transit Buses

Figure 22. Alcohol versus diesel 

transit bus emissions (Detroit Diesel

Corporation 6V92 engines)

* Particulate matter values were magnified 

10 times to show results on the same scale.

M65-B0344022
emitted by otherwise identical 

diesel transit buses equipped with

particulate traps. These same levels

are much lower, on average, than the

particulate matter levels emitted by

diesel transit buses without traps.

Although the particulate traps were

effective in reducing particulate 

matter emissions from diesel transit

buses, they were eventually removed

from the market and from these vehicles because of maintenance and

durability problems.

Most of the ethanol, and all of the

methanol, transit buses emitted lower

levels of oxides of nitrogen than did

their diesel counterparts. On the

other hand, the alcohol fuel transit

buses emitted higher amounts of

hydrocarbons and carbon monoxide,

on average, than did their diesel

counterparts. Newer methanol transit

buses with Detroit Diesel 6V92TA

engines operating in New York City

exhibited consistently lower carbon

monoxide and hydrocarbon emissions than either their diesel counterparts, or the older alcohol fuel 

transit buses.

Contrary to some of the test results

just noted, certification information

on the Detroit Diesel 6V92TA

engine indicates emissions reductions should be achieved in all four

exhaust constituents (hydrocarbons,

carbon monoxide, oxides of nitrogen, and particulate matter). Possible

causes (including faulty catalytic

converters) for the increased hydrocarbon and carbon monoxide emissions levels recorded for the transit

buses in the Federal evaluation 

program are being investigated.

Detroit Diesel has made recent

improvements to the fuel injectors,

which may also help reduce exhaust

emissions levels, and has agreed to

work to identify the causes of the

higher carbon monoxide and hydrocarbon emissions recorded on the

older transit buses in the program.

41

Transit Buses

Figure 23. Cumulative mileage on all

alternative fuel and control vehicles in

the Federal transit bus demonstration

program to date

Miles to Go Before We’re Done 

The goal of the program is to gather 18 months of data on ten transit

buses of each fuel type, with those vehicles being equally divided

between two locations. This data collection effort is not complete.

Some sites have finished submitting data; others are still doing so.

Significant differences between sites often emerge as a result of different experience with the transit buses, different operating conditions, and

different reporting procedures. In addition, the manufacturers are constantly updating their engines. Care should therefore be taken in drawing final conclusions about a particular alternative fuel or engine based

on the results thus far.

Although Figure 23 shows that almost 4,000,000 total miles have been

accumulated on the test vehicles, Figure 24 shows considerable variation in mileage accumulation among the sites. All the current sites

should complete their mileage accumulation by mid-1996.

M65-B0344023
42

Transit Buses

Biodiesel Blend

It was recently discovered that problems had occurred at the St. Louis

transit site in mixing the neat

biodiesel with the diesel fuel to create B20, the biodiesel blend. As a

result, emissions tests were invalidated. Tests will be repeated in 1996

with a new batch of properly blended

fuel. Again, the Department of

Energy does not consider B20 to 

be an alternative fuel under the 

provisions of the Energy Policy Act

of 1992.

Performance and Reliability

A common measure of transit bus

reliability is the number of road calls

that are required for every 1,000

miles a vehicle travels. When the driver is prevented from completing his

or her route because of a problem

with the transit bus, and a call for a

replacement vehicle is made, a road

call is recorded. Road calls encompass all types of events, from engine

failure to simply running out of fuel.

Information on the road calls per

1,000 miles of operation for vehicles

in the Federal transit bus evaluation

program is shown in Figure 25. A

comparison among transit buses

operating on different fuels at various locations is provided.

Liquefied Natural Gas

Figure 25 indicates that the dual-fuel

transit buses in Houston operating on

liquefied natural gas and diesel are

experiencing considerably more road

calls than their diesel counterparts.

The higher count for the dual-fuel

vehicles is largely due to running 

out of fuel or to the system detecting

a fuel leak and shutting down the

transit bus.

Houston’s dual-fuel transit buses

experienced more than ten times the

rate of road calls for “out of fuel”

than did their diesel counterparts,

because dual-fuel transit buses have

a relatively small diesel tank. If a

fuel problem develops with the 

Figure 24. Total mileage on alternative

fuel transit buses in the program

Figure 25. Road calls per 1,000 miles

of operation

* Biodiesel blends other than B100 are not 

considered by the U.S. Department of 

Energy to be alternative fuels at this time.

** Miami alternative fuel transit buses 

have accumulated relatively low mileage 

compared to the other CNG site (Tacoma). 

See Figure 24.

St Louis *Biodiesel blend

Miami M100

Minneapolis E95

Peoria

Tacoma

E95/E93

CNG

**Miami CNG

Houston

LNG/Diesel

Dual-fuel

M65-B0344024 M65-B0344025
liquefied natural gas, the dual-fuel

engines are designed to run on diesel

as a backup. In this case, the transit

bus would run out of diesel in a short

time because the diesel fuel tank

alone is not large enough to run the

transit bus independently for long

periods of time.

As a check on the difficulties experienced in Houston, an additional location with transit buses running on

liquefied natural gas has recently

been added to the transit bus evaluation program. The engines in these

vehicles are different from those in

the Houston vehicles, and as road

call information is gathered, comparisons of the two types of engines will

be presented.

Other Fuels

In Miami, transit buses running on

compressed natural gas experienced

a higher rate of road calls per 1,000

miles traveled than did their diesel

counterparts. In Tacoma, the rates 

for the two types of transit buses

were about the same. The total

mileage accumulated on the Miami

compressed natural gas transit buses

is relatively limited; therefore,

greater weight is given to the

Tacoma data. These findings underscore the need to gather information

on each alternative fuel at more than

one location, and to average data

over many miles.

In Peoria, road calls per 1,000 miles

for transit buses operating on 95 percent ethanol are comparable to the

rate observed for diesel transit buses

(the control group) equipped with

particulate traps. The Peoria transit

buses—both diesel and ethanol—had

the lowest road call rates of any vehicles at any location in the Federal

transit bus evaluation program.

In Miami, transit buses operating on 

100 percent methanol have a somewhat higher road call rate than their

diesel counterparts. This difference is

primarily due to problems with the

fuel systems and engine stalling.

Again, however, this information is

based on a relatively small mileage

accumulation—less than 200,000

miles. A second location—New York

(Triboro)—with more transit buses

running on 100 percent methanol,

was recently added to the Federal

evaluation program in hopes of

obtaining data over a larger number

of miles traveled. Data from New

York will be compared to the Miami

results as they become available.

Fuel Economy

Fuel economy and fuel costs are very

important to transit agencies because

these elements represent a significant

portion of the total expense of operating a transit bus. Approximately

half the total cost (excluding driver

wages) of operating a diesel transit

bus is directly attributable to fuel

economy and fuel cost. In contrast,

these items represent more than half

the total cost of operating some 

alternative fuel transit buses.

As in the case of light-duty vehicles,

fuel economy for transit buses can 

be determined in two ways: as 

direct measurements from engine

dynamometer tests, and from actual

in-use service. Figure 26 shows the

average fuel economy from engine

dynamometer tests, as well as a 

range of in-use fuel economy, for 

43

Transit Buses
44

Transit Buses

the vehicles included in the Federal

transit bus evaluation program. A

comparison is made among the various types of fuels used at different

program locations. Expressing fuel

economy in miles per equivalent gallon of diesel facilitates a direct comparison of the relative energy efficiency of the various alternative fuels.

As illustrated in Figure 26, fuel

economy varies between fuels, and

from one site to the next. This variability may result from differences in

driving cycles among transit bus

types and among locations.

On the other hand, the dynamometer

results, which were obtained using

the Central Business District driving

cycle, are relatively constant. This

observation partly confirms the

above suggestion that variability in

the in-use results is due to differences in driving cycle. However,

because the dynamometer fuel economy values are consistently below

the average in-use values, the 

Central Business District driving

cycle may not be representative 

of the actual driving cycles of the

transit buses in the program.

As a follow-on to the above 

discussion about the fuel economy

achieved by the vehicles in the

Federal transit bus evaluation 

program, additional comments and

analytical comparisons can be made.

The first have to do with the liquefied natural gas engines in the transit

buses operated in Houston. These

engines operate on a compressionignition cycle; that is, diesel is used

as a “pilot ignition” source to ignite

the natural gas. The average fuel

economy for these transit buses was

calculated by summing the amount

of liquefied natural gas (in diesel

equivalent gallons) and diesel burned

in the transit buses over time, and

dividing that sum by the total miles

logged. The resulting number (3.1

miles per diesel equivalent gallon)

was approximately 16 percent less

than the average fuel economy for

the diesel counterparts. The lower

fuel economy for liquefied natural

gas transit buses may be partly 

attributed to the extra weight

(approximately 860 pounds), but 

is more likely to be the result of

problems with the engine, or with

external factors such as driving

cycles.

It is interesting to note that, when 

the dual-fuel transit buses were 

Figure 26. Average fuel economy for

transit buses*, expressed as miles per

diesel equivalent gallon

* Information from the Houston LNG transit

buses is not shown because only a single

point average is available as opposed to the

range of values available for other types of

buses.

M65-B0344026
45

Transit Buses

operating in their “backup” mode of

diesel only, the fuel economy was

within 4 percent of that of the diesel

transit buses (the control group).

This indicates that the extra weight

of the dual-fuel transit buses is not

the major deterrent to fuel economy.

A second point of note has to do

with the compressed natural gas

engines in transit buses operated at

Miami and Tacoma. These are sparkignited throttle engines. The diesel

engines, in contrast, are unthrottled

compression-ignition engines. When

a diesel compression-ignition engine

is redesigned into a spark-ignition

engine running on compressed natural gas (as is the case with all the

compressed natural gas engines in

the Federal evaluation program transit buses), there is an inherent reduction in efficiency (fuel economy)

because of pumping losses. Pumping

losses represent the amount of 

energy required for the engine to

draw in air during the intake cycle.

An unthrottled diesel engine exhibits

minimal pumping losses, whereas a

spark-ignited engine with a throttle

realizes significant pumping losses.

Also, the compressed natural gas

engines have a lower compression

ratio than their diesel counterparts:

10.5:1 for the compressed natural

gas engines versus 16.3:1 for the

diesel engines.

An additional deterrent to fuel economy in the compressed natural gas

transit buses is their weight—about

3,900 pounds more than otherwise

identical diesel transit buses. This

weight penalty, which is largely

attributable to the fuel tanks, results

in about a 15 percent increase in 

the curb weight of a transit bus (the

standard diesel transit buses have 

a curb weight of approximately

27,000 pounds).

Because all the above factors are

expected to adversely affect energy

efficiency, the reported difference in

fuel economy between the compressed natural gas and diesel transit

buses is not surprising. The average

fuel economy of the compressed 

natural gas transit buses from

dynamometer tests is about 10 percent to 20 percent lower than the

corresponding average fuel economy

for their diesel counterparts.

Third, with regard to fuel economy

of alcohol transit buses, there are

also adverse weight factors to consider. The alcohol option results in a

weight penalty of between 1,000 and

1,500 pounds, depending on fuel

tank capacity. In specific regard to

the alcohol transit buses operated in

Miami, another 1,200 pounds is

attributed to options and specifications unrelated to the engine or fuel

system. Alcohol transit buses also

have very high compression ratios

(more than 20 to 1), which also tend

to lower fuel economy because of

friction losses (for example, piston

side loading). Consequently, even

before data began to be collected 

on these transit buses, they were

expected to exhibit lower fuel economy, on average, than their diesel

counterparts.

Despite these considerations, the

results to date indicate that the alcohol fuel transit buses at all the sites

are performing very well, delivering
fuel economy comparable to that of

their diesel counterparts. A possible

explanation is that the weight and

compression ratio penalties may not

be as significant as the pumping

losses caused by throttling. The 

95 percent ethanol and the 100 percent methanol engines at

Peoria, Minneapolis, and

Miami are powered by

unthrottled compressionignition engines, so they

do not suffer from the

same pumping loss penalties as the compressed natural gas buses. Also, the

standard diesel transit

buses (control group) at

Peoria are equipped with

particulate traps, which 

are known to lower fuel

economy slightly.

In summary, most fuel economy

results to date are in line with expectations, with the possible exceptions

of the numbers reported for liquefied

natural gas dual-fuel engines. Data

collection efforts are continuing, and

updates to the profiles noted above

are anticipated.

Cost

The incremental costs associated

with operating alternative fuel transit

buses can be aggregated into two

categories: increased capital outlays

and increased operating expenses.

Increased capital outlays are attributable to the additional costs (if any)

of acquiring alternative fuel transit

buses and modifying facilities.

Increased operating expenses are 

due to a larger number of factors.

Figure 27 shows a breakdown of 

the total operating costs for a typical

large transit agency such as the ones

participating in the Federal transit 

bus evaluation program. Driver labor

costs represent more than half of the

total. Operating components likely 

to be affected by the introduction of

alternative fuel transit buses are vehicle maintenance, facility maintenance,

and fuels and lubricants availability

and cost. Together, however, these

components represent only about a

third of the total operating expense.

Comparative Facility Costs

Because transit buses are centrally

stored and refueled at facilities

owned and operated by transit agencies, the capital and operating costs

associated with any changes to those

facilities to accommodate alternative

fuel transit buses become an important part of the total cost of doing

business. The price for new facilities,

or modifications to existing facilities,

varies widely, even when only one

type of alternative fuel vehicle is

involved. The cost is likely to be

highest when compressed natural gas

or liquefied natural gas is the alternative fuel of choice. The necessary

changes can include installation of

new refueling stations, as well as

installation of monitoring and ventilation equipment. Construction and

equipment installation costs are

affected, in turn, by the size of the

agency involved, and by the state and

local building codes. Some representative incremental capital costs are

shown in Table 2.

46

Figure 27. Total operating costs for 

a large transit agency

Transit Buses

M65-B0344027
Incremental Acquisition Costs

At the time of this writing, transit

buses operating on alternative fuels

are more expensive to purchase than

those operating on diesel. Higher

engine costs represent a significant

portion of the higher purchase price.

Because alternative fuel engines are

in relatively limited production, the

manufacturers charge $25,000 to

$30,000 more for them than for standard diesel engines. As their production volumes increase, though, the

cost of alternative fuel engines will

begin to approach those of their

diesel counterparts. Yet it is unclear

whether the price of alternative fuel

engines for transit buses will ever

equal that of comparable diesel

engines. Transit buses operating on

biodiesel blends (which are not considered by the Department of Energy

to be alternative fuels under the provisions of the Act) are the exception

to this rule, because they are automatically outfitted with conventional

diesel engines (hence, there is no

incremental acquisition cost).

In addition to being equipped with

more expensive engines, the fuel

tanks on alternative fuel transit buses

cost more than their conventional

diesel counterparts. The incremental

amount can range from $5,000 for a

bus operating on 95 percent ethanol

to around $20,000 for one operating

on compressed natural gas. Again,

fuel tanks add no expense to the 

cost of buses operating on biodiesel

blends.

Comparative Fuel Costs

In 1995, the price paid for a gallon

of diesel fuel by the transit agencies

with vehicles in the Federal transit

bus demonstration program ranged

from about $0.47 to about $0.65.

The corresponding price for an 

alternative fuel on an equivalentgallon-of-diesel basis was even 

more variable, depending on the 

fuel of interest. With a range of

47

Source: Battelle Memorial Institute;

based on previous reports completed

for the Federal Transit Administration

and the American Trucking Association

by Battelle Memorial Institute and

Gannett Fleming.

Transit Buses

Table 2. Incremental Facility Costs for a Fleet of 160 Alternative Fuel Transit Buses (In millions of 1994 dollars)

LNG CNG Alcohols* Propane** Biodiesel blend***

Fueling Facility $0.9 $1.5 $0.1 $0.2 NC

Maintenance Facility $1.2 $1.1 NC NC** NC

Bus Storage Facility $1.4 $1.2 NC NC** NC

Total $3.5 $3.8 $0.1 $0.2 NC

NC No change if facility is certified for gasoline

* Methanol and ethanol

** The installation of propane gas detection systems in areas where propane-fueled vehicles are parked or maintained may be required by 

local authorities or considered to be good practice by facility design engineers. Increased ventilation to handle possible propane releases 

may also be included in the facility design. Often, the operation of such increased ventilation is tied to the gas detection system.

*** Only neat biodiesel (B100) is currently considered by the Department of Energy to be an alternative fuel under the provisions of the Act.
$0.55 to $0.69 per diesel equivalent

gallon, compressed natural gas was

the cheapest. This price excludes the

cost of electricity needed to compress the fuel. 

One hundred percent methanol cost

$1.72 per diesel equivalent gallon.

The price paid for 95 percent ethanol

was $1.83 per diesel equivalent gallon, making it the most costly of the

fuels used.

Some additional variations were

noted on a regional basis. Early 

in 1994, the Peoria transit agency

switched from using 95 percent

ethanol to 93 percent ethanol 

(93 percent ethanol, 5 percent

methanol, and 2 percent kerosene) 

to take advantage of a $0.43 per gallon “blenders’ credit,” which lowered

its fuel cost to $1.21 per diesel

equivalent gallon. B20, the biodiesel

blend used in Missouri (not considered by the Department of Energy to

be an alternative fuel at this time),

cost about $1.00 per diesel equivalent gallon, and the liquefied natural

gas and diesel combination used in

Houston cost about $0.80 per diesel

equivalent gallon.

In general, the prices of alternative

fuels are more variable and more

expensive than those of diesel, not

only from one region to another,

but also from one period of time 

to another.

Comparative 

Maintenance Costs

Maintenance costs are continually

being tracked for all the vehicles in

the Federal transit bus evaluation program. Copies of all the work orders,

as well as lists of the parts replaced,

are received from the transit agency

involved. This information is coded

by the type of work performed (for

example, scheduled maintenance,

unscheduled maintenance, road calls,

and configuration changes to the

buses), and various vehicle subsystems are identified (for example,

engine type and fuel system).

A few words of caution are necessary

about using the maintenance data. As

more miles are logged on the transit

buses, a better maintenance profile

emerges. Maintenance records of

low-mileage vehicles cannot be

extrapolated. Also, comparisons of

maintenance records from different

agencies should be avoided, because

of differences in the way in which

maintenance incidences are defined

and recorded. Finally, the maintenance cost data do not include 

48

Figure 28. Transit bus fuel and 

maintenance costs per mile traveled

(Note: Maintenance costs for the 

transit buses at St. Louis include only

costs related to the engine/fuel system.)

* Biodiesel blends other than B100 are not 

currently considered by the U.S. Department

of Energy to be alternative fuels

Houston-Diesel

Houston-LNG/Diesel

Miami-Diesel

Miami-CNG

Tacoma-Diesel

Tacoma-CNG

Peoria-Diesel

Peoria-E95

Peoria-E93

Minneapolis-Diesel

Minneapolis-E95

Miami-Diesel

Miami-M100

St. Louis-Diesel

*St. Louis-Biodiesel blend

Transit Buses

M65-B0344028
warranty repair work performed on

the transit buses because the agencies

do not bear the cost of this activity.

Some general comments can be

made regarding the cost of maintaining vehicles in the Federal transit bus

evaluation program. According to the

data available, maintenance costs for

the Houston transit buses operating

on a combination of liquefied natural

gas and diesel are considerably 

higher than those of their diesel

counterparts. This is partly due to

difficulties with the gas injectors and

with contaminants in the fuel. Fuel

system leaks are also a source of

concern. However, as of this writing,

all problems are being rectified by 

the engine manufacturers and by

Houston Metro. The maintenance

costs of transit buses operating on all

the other alternative fuels at all other

locations are comparable to those 

of their diesel counterparts.

Cost per Mile Traveled

Figure 28 shows the fuel and maintenance costs per mile traveled for the

vehicles in the transit bus demonstration program. The fuel cost per mile

was calculated using average in-use

fuel economy and the actual fuel cost

paid by the transit agencies. For transit buses operating on compressed

natural gas, the fuel and maintenance

costs per mile are about the same as

those for transit buses operating on

diesel.

However, for transit buses operating

on an alcohol fuel or B20 (a biodiesel blend that is not, at this time,

considered by the Department of

Energy to be an alternative fuel), the

same costs are up to twice as high as

those for transit buses operating on

diesel. The fuel and maintenance

costs for transit buses operating on

liquefied natural gas/diesel are about

25 percent higher than for their

diesel counterparts.

Summary

Transit buses potentially represent

one of the best applications for alternative fuels, and the transit bus data

collection efforts have been some of

the most successful in the Federal

alternative fuel evaluation programs.

The transit bus evaluation program

has accumulated a respected body 

of evidence on the emissions, performance and reliability, fuel economy,

and cost of alternative fuel buses.

This information is leading to the

continued development and proliferation of this technology.

Depending on the alternative fuel,

the emissions results for the transit

buses in the program are still highly

variable. However, a few general

conclusions can be drawn. All the

alternative fuels did emit decreased

levels of particulate matter, which

has been linked to detrimental human

health effects. With compressed natural gas, particulate matter emissions

are almost zero. Compressed natural

gas vehicles have also shown the

potential to have very low carbon

monoxide, non-methane hydrocarbons, and, to a lesser extent, nitrogen

oxide emissions. However, the level

of technology of the engine and the

maintenance on the engine have been

shown to be equally important factors in reducing exhaust emissions.

49

Transit Buses
50

In most cases, the reliability of the

alternative fuel transit buses in the

program proved to be similar to the

reliability of the diesel control transit

buses. This is a positive sign, considering the relative immaturity of this

market versus the diesel market. The

exceptions are the liquefied natural

gas dual-fuel transit buses in Houston

(the engines in these buses are no

longer in production), and the compressed natural gas transit buses in

Miami, which have very low mileage.

Similar compressed natural gas transit

buses in Tacoma have much higher

mileage, and have proven reliable.

At this time, no fuel has been 

shown to have both a low up-front

capital cost and a low operating cost.

The alcohol and B20 (a low-level

biodiesel blend that the Department

of Energy does not consider to be an

alternative fuel under the provisions

of the Act) transit buses have a low

to moderate up-front cost, but higher

operating costs resulting from the

relatively high fuel prices. The compressed natural gas transit buses, on

the other hand, have a high up-front

cost for acquisition and infrastructure, but their operating costs are

similar to those of diesel transit

buses. As time goes on and production volumes increase, the price of

alternative fuel transit buses should

decrease, although it is unclear how

close they will come to the cost of a 

diesel transit bus.

Transit Buses
Overview

The Federal heavy-duty demonstration program (section 400 BB of 

the Energy Policy and Conservation

Act) includes two types of vehicles:

medium-size commercial delivery

vans and large trucks (such as tractor

trailers and garbage packers). In total,

some 170 delivery vans and large

trucks are included in the program,

and Figure 29 identifies their service

locations. Actual vehicle descriptions

and their service functions are listed

in Table A-3 in the Appendix.

Delivery vans in two commercial

delivery fleets are included: the

Federal Express fleet and the United

Parcel Service fleet. The Federal

Express vehicles are evaluated in the

CleanFleet project, which is coordinated by Battelle Memorial Institute.

The CleanFleet project has been

completed, and the final report is

being prepared. Delivery vans operating on several alternative fuels

were tracked, including those running on compressed natural gas,

propane, and 85 percent methanol, as

well as some standard reformulated

gasoline vehicles (the control group).

The update provided below summarizes the findings available to date

from this study.

The United Parcel Service project

covers only delivery vans operating

on compressed natural gas. Some

standard reformulated gasoline 

vans were also tracked for comparison purposes (the control group).

Because large trucks are very 

expensive to acquire and operate,

only a limited number of these vehicles are being tracked in the Federal

demonstration program. In addition,

because there are so few emissionscertified production engines available

for large trucks that operate on alternative fuels, most (but not all) of 

the vehicles currently included in 

the program are powered by preproduction field-test engines. In 

contrast, the transit bus evaluation

program includes only emissioncertified production engines. These

demonstrations serve the dual 

purpose of allowing the technology

to be refined, while demonstrating 

its viability.

Heavy-Duty

Vehicles

Figure 29. Locations of heavy-duty

vehicles in the Federal demonstration

program

51

M65-B0344029
Cummins L10G engine

The sidebar at the left highlights 

the actual alternative fuel engines

available for large trucks that are

currently in production or preproduction by original equipment

manufacturers. All but one of these

engines are dedicated to run on 

natural gas.

To put as many large trucks in the

Federal demonstration program as

possible, the U.S. Department of

Energy has funded approximately

half the acquisition and operation

costs of those included. The remainder of the funding has been provided

by a variety of entities, including

state and local government agencies,

public utility companies, fuel suppliers, special interest groups (such as

the Minnesota Corn Growers and the

Iowa Soybean Association), and host

fleets. In many cases, two or more

organizations have joined forces to

provide the non-Federal portion of

the funding.

In contrast to the delivery vans, the

large trucks included in the program

are used in various specialized functions (called “vocations”), such as

52

Heavy-Duty Vehicles

Heavy-Duty Alternative Fuel Engine Availability

Several original equipment manufacturers now have alternative fuel heavy-duty engines in

production. Below is a list of the engines made by each of these companies and their use.

Production

Horsepower

Manufacturer Model Fuel Range Vocations

Detroit Diesel 6V92 E95 250-275 Bus, heavy truck

Detroit Diesel 6V92 M100 250-275 Bus, heavy truck

Detroit Diesel Series 50 Natural gas 250-275 Bus, garbage packer

Detroit Diesel Series 30 Natural gas 210 Medium truck

Cummins B5.9 Natural gas 195 Medium truck,

school bus

Cummins L10G Natural gas 240-260 Bus, heavy truck,

garbage packer

Caterpillar 3306 Natural gas 250 Bus, medium truck,

garbage packer

Hercules GTA 5.6 Natural gas 190 Bus, medium truck

The natural gas engines can run on either compressed natural gas or liquefied natural gas.

In addition to the engines that are currently in production, several companies have heavyduty engines that are in the pre-production development and demonstration phase. The

pre-production engines are listed below. 

Pre-Production

Horsepower

Manufacturer Model Fuel Range Vocations

Detroit Diesel Series 60 Natural gas 370-450 Heavy truck

Detroit Diesel Series 50 Natural gas 300 Heavy truck

Detroit Diesel Series 50 Propane 250-275 Bus, Heavy truck

Detroit Diesel Series 40 Natural gas Unknown Medium truck, school bus

Cummins L10G Natural gas 300 Heavy truck, garbage

packer

Cummins Mll Natural gas 340 Heavy truck

Cummins C8.3 Natural gas 250 Bus, medium truck

Caterpillar 3406 Natural gas 350 Heavy truck

Navistar* T444 Natural gas 210 Medium truck

Mack E7 Natural gas 300 Heavy truck

John Deere 6081 Natural gas 250 Bus

* Developed jointly with Detroit Diesel Corporation. 

This engine is the same as the DDC Series 30 natural gas engine.

Most of these engines are designed to be used in transit buses or large trucks

such as tractor-trailer line-haul trucks or large municipal trucks (such as dump

trucks and plows). However, some engines (with the vocations labeled “medium truck” above) are being targeted for the lighter end of the heavy-duty

vehicle spectrum. Representative vocations for these include delivery trucks,

lighter municipal trucks, and 20-foot box trucks. Some of these medium truck

engines are also being built for school buses.

Photo courtesy of Cummins Engine Company/PIX 03318
picking up refuse or transporting

goods over long distances (known as

line-haul operation). The driving

cycles of large trucks are distinctly

different, depending on their vocations. Consequently, an effort has

been made to include as many such

vocations as possible in the mix of

trucks included in this program.

Figure 30 shows the current numbers

of large trucks by vocation.

For each vehicle (whether van or

truck) in this demonstration program,

data are being collected on performance, fuel and oil consumption, and

any problems encountered. In the case

of vehicles powered by pre-production

engines, such information is being

reported directly to the manufacturers

to facilitate technological improvements, which, in turn, will eventually

be included in the program.

In addition, vehicles powered by

emissions-certified production

engines are being emissions tested,

with tests performed at

regular mileage intervals.

Emissions results are

being collected on the

alternative fuel vehicles

and the vehicles operating

on conventional fuels,

which serve as the control

group. Unleaded reformulated gasoline is the conventional fuel for commercial delivery vans; diesel is

the standard for large

trucks.

Finally, the demonstration program

described above is not the only effort

under way to

foster the use of

alternative fuels

in heavy-duty

applications.

The U.S.

Department of

Energy also

manages a grant

program that

53

Figure 30. Numbers of large trucks

by vocation

Heavy-Duty Vehicles

The Vons natural gas truck in service

Delivering Groceries by Natural Gas

From October 1992 through December 1994, the

Vons Grocery Company truck number 9207 drove

into El Monte, California, hooked up a trailer loaded

with thousands of pounds of groceries, and headed

north over Tejon Pass on Interstate 5 to deliver those

groceries to Bakersfield. This truck was unique

among the 180 Vons trucks based out of

the El Monte distribution center—it was

powered by compressed natural gas. The

Vons natural gas truck operated successfully for 14 months, racking up more than

50,000 kilometers (30,000 miles) of service, and its performance was comparable

to that of its diesel-powered cousins.

Caterpillar, Inc., developed a natural gas

version of its popular model 3406, 350

horsepower engine for this particular project, and the Vons truck gave it the opportunity to field test its new engine and

refine its design. Caterpillar is now using

the natural gas truck used in the Vons

demonstration to refine the 3406 natural

gas engine.

Photo by Warren Gretz, NREL/PIX 03317

M65-B0344030
supports states in their purchases of

heavy-duty alternative fuel vehicles.

The vehicles in the grant program

are located across the country, representing vehicle vocations that range

from street sweepers to school buses.

The locations of these vehicles are

shown in Figure 31, with additional

details being given in Tables 4

through 7 in the Appendix.

Emissions

As with the transit buses, emissions

data were obtained on heavy-duty

vehicles using the test equipment and

procedures developed by West

Virginia University.

Large Trucks

During 1995, the university used its

transportable chassis dynamometer

to measure emissions from the New

York City Department of Sanitation’s

compressed natural gas garbage

packers, Archer Daniels Midland’s

ethanol line-haul trucks in Illinois,

Hennepin County’s ethanol snowplows in Minnesota, and AG

Processing Corporation’s line-haul

trucks operating on a blend of

biodiesel and diesel (biodiesel blends

other than B100 are not considered

by the U.S. Department of Energy 

to be alternative fuels under the 

provisions of the Act). A number 

of diesel control vehicles with the

same engine configurations were

also tested at each of the sites.

Many of the basic engine configurations deployed in vehicles in the

Federal heavy-duty demonstration

program, such as the Cummins

L10GG compressed natural gas

engine and the Detroit Diesel

Corporation alcohol 6V92 engines,

are the same as those in the vehicles

in the Federal transit bus evaluation

program.

Although the same engine model

may be used for large trucks and

transit buses, several important 

differences still exist. An engine

designed for large truck applications

will generally have higher horse

power and different speed-torque

maps, and will be certified under 

different emissions standards than

the same engine model designed for

transit bus operation (see Table 3). 

In addition, many of the large heavyduty trucks in the program have

manual transmissions and are driven

54

Figure 31. Locations of heavy-duty

vehicles in the U.S. Department of

Energy grant program

* At this time, soydiesel is not considered 

by the U.S. Department of Energy to be 

an alternative fuel

CNG

Ethanol

Methanol

LPG

SoyDiesel*

Heavy-Duty Vehicles

Table 3. U.S. Environmental Protection Agency Heavy-Duty Engine

Standards (in grams per brake horsepower hour) for Heavy-Duty Trucks

HC CO NOx PM

1991–93 1.3 15.5 5.0 0.25

1994–97 1.3 15.5 5.0 0.10

1998 1.3 15.5 4.0 0.10

M65-B0344031
in over-the-road line-haul applications, whereas transit buses typically

have automatic transmissions and 

are operated in stop-and-go urban

driving conditions. These differences

are important to consider when 

performing chassis dynamometer

emissions tests and interpreting 

the results.

Another factor to consider when

emissions testing heavy-duty vehicles

is the driving cycle. Although the

Central Business District chassis

dynamometer driving cycle is an

accepted test cycle for buses, many

large trucks with manual transmissions are unable to accomplish the

rapid accelerations and braking

requirements of that test. Development of a more appropriate test cycle

for heavy-duty trucks is the topic of

several ongoing research projects. In

the interim, West Virginia University

has designed a “5-peak” driving

cycle (see Figure 32) that can be 

driven by most large heavy-duty

trucks. Except where noted, the

results reported here for the vehicles

in the Federal heavy-duty demonstration program are based on this 

5-peak driving cycle.

Emissions Test Results from

Ethanol Trucks

During 1994 and 1995, West Virginia

University personnel made two trips

each to Peoria and Minneapolis to

test the emissions of heavy-duty

trucks powered by Detroit Diesel

Corporation 6V92 engines operating

on 95 percent ethanol. In Peoria,

four ethanol trucks and one diesel

(control) line-haul truck owned and

55

Figure 32. West Virginia University’s 

5-peak driving cycle compared to the

Central Business District driving cycle

Heavy-Duty Vehicles

M65-B0344032
operated by Archer Daniels Midland

were tested. In Minneapolis, two

ethanol snowplows and one diesel

(control) snowplow belonging to

Hennepin County were tested.

For various emissions constituents,

Figure 33 shows the average, minimum, and maximum values observed

in the trucks tested in Peoria and

Minneapolis. Although the two

engine applications are quite different

(snowplow versus line-haul tractor),

the average observed emissions are

similar. At both locations, the average

particulate matter detected in the

ethanol trucks was less than 50 percent of the corresponding diesel

value for their diesel counterparts, the

average oxides of nitrogen observed

in the ethanol trucks were marginally

lower than in their diesel counterparts, and the average hydrocarbon

and average carbon monoxide values

were observed to be higher in ethanol

trucks than in diesel trucks. Also,

emissions results from ethanol trucks

at both locations are more variable

than the corresponding values from

diesel trucks, especially in the case of

carbon monoxide and hydrocarbons.

In general, the emissions from the

heavy-duty trucks are similar to

those for transit buses operating on

ethanol Detroit Diesel Corporation

6V92 engines. For the large trucks

and buses, average particulate matter

and oxides of nitrogen are lower 

for the ethanol vehicles. However,

hydrocarbon and carbon monoxide

emission levels are higher than those

of their diesel counterparts.

As with the transit buses, ethanol

heavy-duty trucks show potential for

contributing to cleaner air by reducing levels of particulate matter and

oxides of nitrogen. However, the

higher variability in individual emissions results from these ethanol vehicles may point to the need for further

technological improvements. To this

end, results from the Federal heavyduty demonstration program are

being communicated to the engine

manufacturers to help them identify

and correct the problems associated

with the high emitters.

Emissions Results from Compressed

Natural Gas Garbage Packers

Also during 1994 and 1995, West

Virginia University personnel tested

six compressed natural gas and three

diesel New York City Department of

Sanitation garbage packers for emissions output. These vehicles were

tested using the Central Business

District driving cycle because they

56

Heavy-Duty Vehicles

Figure 33. Comparative emissions

results for ethanol and diesel trucks 

in Peoria and Minneapolis

✝✝ Particulate matter values were magnified 

10 times to show results on the same scale

M65-B0344033
typically operate in urban service,

and because they are equipped 

with automatic transmissions. The

engines in the compressed natural

gas garbage packers represent 

early demonstration versions of the

Cummins L10GG, which have been

available since 1992. Cummins engineers have indicated that the vehicles

powered by these engines were

placed in fleets as “proof of concept”

vehicles, and were not optimized for

emissions reductions. As expected,

the emissions results from these

vehicles have been mixed, but are

reported here for completeness. They

also establish a benchmark against

which new compressed natural gas

technologies can be compared.

Figure 34 shows the average, minimum, and maximum emissions from

the New York City garbage packers.

The average particulate matter from

the compressed natural gas vehicles

is very low. In six of eleven tests 

performed to date, particulate matter

levels are essentially zero (that is,

too low to measure), and the diesel

vehicles average approximately 

0.7 grams per mile. Again, as in the

case of transit buses, this is an attractive feature of compressed natural

gas, because these vehicles operate

in populated urban areas where particulate matter from vehicle exhaust

is a serious human health concern.

On the other hand, the average hydrocarbons emissions from the compressed natural gas garbage packers

are higher than the corresponding values for the diesel garbage packers. As

in the case of transit buses, hydrocarbon emissions from the compressed

natural gas vehicles typically comprised 90 percent to 95 percent

methane. The Environmental

Protection Agency and California 

Air Resources Board regulations 

are written in terms of non-methane

hydrocarbons because methane is

considered to be non-reactive in the

atmosphere. However, methane is a

potent greenhouse gas—far more

active than carbon dioxide. The nonmethane hydrocarbon levels from the

compressed natural gas garbage packers were not measured directly, but

the values are projected to be similar

to or lower than those observed in the

diesel garbage packers.

The carbon monoxide and oxides of

nitrogen levels observed in the compressed natural gas garbage packers

are not as encouraging. Individual

values of carbon monoxide and

57

Figure 34. Emissions results for New

York City garbage packers

* Total hydrocarbons.

✝✝ Particulate matter values were magnified 

10 times to show results on the same scale.

Heavy-Duty Vehicles

M65-B0344034
oxides of nitrogen vary greatly, but

most test results were notably higher

than the corresponding results for

garbage packers operating on diesel.

It should be noted that the compressed natural gas engines on 

which the tests were conducted 

are “uncertified” with regard to

emissions. As in the case of these

engines deployed in transit buses,

later versions have been optimized

for emissions reduction, and early

tests on the enhanced models show

substantial reductions in the levels 

of carbon monoxide and oxides of

nitrogen (see the section on transit

bus emissions for further discussion).

There are plans to pursue emissions

testing of the newer model, certified

engines as they are put into service

in heavy-duty fleets.

Emissions Results from 

AG Processing Corporation’s 

Biodiesel Blend Line-Haul Trucks

During 1995, West Virginia

University personnel performed the

first round of emissions tests on

trucks operating on biodiesel 

blend (biodiesel blends other than

B100 are not considered by the U.S.

Department of Energy to be alternative fuels under the provisions of the

Act). There are six large heavy-duty

trucks in Iowa operating on biodiesel blend, which are part of AG

Processing Corporation’s line-haul

fleet. All six were previously operated as standard diesel trucks. The

biodiesel blend is composed of 

35 percent methyl ester of soya oil

and 65 percent diesel.

The emissions test procedures for

these trucks differ from those discussed so far, in that each vehicle

was first tested on biodiesel blend

and then retested on standard diesel

fuel. This approach allows for a

direct comparison of the emissions

from the two fuels on each truck.

Of the six biodiesel trucks, two are

powered by Cummins N14 engines,

two by Detroit Diesel Corporation

Series 60 engines, and two by the

Mack E6 engine. Each vehicle was

emissions tested on biodiesel blend,

operated for approximately one week

on conventional diesel, and then

retested on diesel. The results from

the emissions tests are summarized

in Figure 35. The vehicles with the

Cummins N14 and Detroit Diesel

Series 60 engines all exhibited a

decrease in average carbon monoxide, particulate matter, and hydrocarbon emissions when tested on

biodiesel blend, relative to the average values for these same vehicles

tested on diesel. The particulate matter and hydrocarbon averages ranged

between 15 percent and 23 percent

below the corresponding values 

58

Figure 35. Emissions results for

biodiesel blend line-haul trucks

(biodiesel blends other than 

B100 are not presently considered 

to be alternative fuels by the U.S.

Department of Energy)

Heavy-Duty Vehicles

M65-B0344035
59

for diesel. In addition, all engine

makes registered a small (less than

10 percent) increase, on average,

in oxides of nitrogen when tested 

on biodiesel blend relative to the 

corresponding averages obtained 

on diesel. The trucks with Mack E6

engines are all high-mileage vehicles. Although the average values 

for all emissions for these vehicles

were higher when tested on biodiesel blend than those obtained

when tested on diesel, the results 

for individual trucks were mixed.

These results are preliminary in that

they are the first heavy-duty truck

chassis dynamometer tests run on

two fuels back to back. Results from

the most consistent of the engines

agree well with results from dynamometer tests conducted on both

fuels individually in the laboratory.

Additional on-site emissions tests

will be conducted on the biodiesel

blend trucks on site in Iowa during

1996. The additional data collected

should allow more rigorous conclusions to be drawn.

Federal Express CleanFleet

In addition to the emissions test

results available from the heavy-duty

vehicles included in the heavy-duty

demonstration program, additional

emissions information has been

obtained from the medium-duty vans

included in the Federal Express

CleanFleet project. This project was

partially funded by the U.S.

Department of Energy.

In the CleanFleet project, 36 delivery

vans were emissions tested at each of

three different mileage levels. The

first round of tests was performed 

at about 4,000 miles, the second at

about 14,000 miles, and the third 

at the end of the project (25,000 to

35,000 miles). Three vans from each

combination of vehicle manufacturer

and fuel type were tested.

The California Air Resources Board

conducted the emissions tests using 

a chassis dynamometer running the

Federal Test Procedure. Industryaverage standard unleaded test gasoline (RF-A) was used in the control

vehicles for purposes of comparison.

The CleanFleet compressed natural

gas vehicles emitted an average of 

65 percent to 80 percent less carbon

monoxide than otherwise identical

vehicles running on unleaded 

gasoline. These vehicles also had 

70 percent to 95 percent lower nonmethane hydrocarbon emissions.

Emissions of oxides of nitrogen 

were mixed; the vehicles using 

catalytic converters designed for natural gas exhaust had lower average

oxides of nitrogen emissions, and the

Ford vans using catalytic converters

designed for gasoline exhaust had

higher average oxides of nitrogen

emissions. However, there is considerable variability among the results

for individual vehicles. Except for

the oxides of nitrogen emissions

from the Ford vans, the difference in

emissions between the compressed

natural gas and gasoline vehicles did

not change dramatically from one

mileage level to the next.

In contrast, the difference in emissions from delivery vans operating

on propane and their counterparts

operating on gasoline did become

more pronounced with increasing

mileage. Generally, the average

Heavy-Duty Vehicles
60

emissions levels from the propane

vans remained relatively constant,

but the gasoline control vans 

exhibited increasing values with

increasing mileage.

In particular, the propane vehicles

emitted less carbon monoxide on

average, but slightly more hydrocarbons, on average, than their 

gasoline-powered counterparts. 

A substantial portion of the emitted

hydrocarbons was unburned propane,

which is relatively non-reactive, photochemically, in the atmosphere. The

results for oxides of nitrogen were

mixed, with individual tests and individual vans being highly variable. 

The overall results from the Ford vans

running on 85 percent methanol were

also highly variable. One conclusion

is that these vehicles tended to exhibit

lower average carbon monoxide emissions than their gasoline counterparts

at various mileage levels.

Performance and Reliability

Vehicle performance for heavy-duty

trucks and commercial delivery vans

encompasses such factors as acceleration, hill climbing, driveability, and

driver acceptance. Information about

the performance of these kinds of

vehicles is collected in two ways:

direct measurements are taken on

parameters such as acceleration and

hill climbing, and driver feedback is

solicited and recorded.

To directly assess the performance of

heavy-duty trucks operating on alternative fuels, acceleration and hill

climbing capability of a compressed

natural gas line-haul truck operated

by Vons Grocery Company and a

diesel counterpart were measured 

in controlled tests. Acceleration was

tested using six consecutive runs in

opposite directions on a single onemile length of road. The hill-climb

tests were conducted on Kellogg

Hill, one of the larger hills in the

greater Los Angeles freeway system.

Both trucks were hauling a trailer

containing a typical load.

Figure 36. Acceleration performance

of the Vons compressed natural gas

and diesel trucks

Figure 37. Hill-climb performance of

the Vons compressed natural gas and

diesel trucks

Top speed (mph), hill climbing

Heavy-Duty Vehicles

M65-B0344036 M65-B0344037
The results of these tests are shown

in Figures 36 and 37. Acceleration

for the two trucks was nearly identical. In the hill-climbing test, the compressed natural gas truck’s top speed

was about two miles per hour slower

than that of its diesel counterpart.

The sidebar on page 62 highlights

specific performance and reliability

issues that have surfaced with the

vehicles in the Federal heavy-duty

demonstration program. These issues

vary from one location to the next.

As a direct result of this field experience, the manufacturers of the

engines included in this program

have already made significant design

improvements. Additional evidence

and experience can only lead to further performance improvements in

heavy-duty alternative fuel engines.

Fuel Economy

Delivery Vans

All fuel economy data for the

CleanFleet delivery vans have been

collected and analyzed. Figure 38

presents a summary of the final inuse and chassis dynamometer fuel

economy information on a mile per

gasoline-equivalent-gallon basis. In

general, all the chassis dynamometer

results are higher than the corresponding in-use values. This result is

probably due to a difference in the

driving cycle of urban delivery vans

in comparison to the driving cycle

used in the dynamometer test. For

example, a typical van usage pattern

includes more stopping and idling

than outlined in the Federal Test

Procedure driving cycle.

In accordance with these considerations, the Chevrolet propane and compressed natural gas vans and Dodge

compressed natural gas vans achieved

10 percent to 15 percent lower in-use

fuel economy than their gasoline

counterparts. The corresponding

dynamometer results for these same

vehicles mirror this result. The fuel

economy achieved by all the Ford

vehicles (compressed natural gas,

propane, and 85 percent methanol)

was within a few percentage points of

the fuel economy achieved by their

gasoline counterparts. This was true

for both the in-use and dynamometer

types of measurements.

Large Trucks

Each time a truck is refueled, the 

driver records the quantity of fuel

put into the truck and its odometer

61

Heavy-Duty Vehicles

Figure 38. CleanFleet fuel economy

results for delivery vans

M65-B0344038
62

Heavy-Duty Vehicles

Heavy-Duty Vehicle Performance and Reliability Issues

Project Fuel Performance Reliability

Federal Express 85 percent methanol, Driveability and range Original equipment

CleanFleet compressed natural complaints manufacturer engines

gas, liquefied generally better than

petroleum gas, conversions

gasoline,

electricity

Vons Grocery Compressed Hill-climb test Numerous reliability

Company Truck natural gas slower than diesel; problems indicate lack

acceleration of development

comparable to diesel

New York City Compressed Comparable One low-mileage

Garbage Packer natural gas performance; piston failure

much quieter

Illinois Dept. of 95 percent ethanol Comparable Bearing failure caused

Commerce and performance by operator error*

Community Affairs/

Arthur Daniels 

Midland truck

Hennepin County 95 percent ethanol Performance com- Fuel pump failures

and Nebraska plaints related to fuel

Highway Department pumps; cold-starting

Snowplow problems; stalling

problems

Los Angeles Times Compressed natural Comparable performance High oil consumption

Truck gas in general, some hard (upgrades are being 

starting installed to solve the 

problem), fuel line rupture (fuel line routing 

was redesigned)

AG Processing 35 percent biodiesel Drivers may have No reliability problems

line-haul truck blend** reported hesitation to date

and lack of power

* A new operator thought that the Detroit Diesel Company-required fuel additive was an oil additive and added it to the crankcase. This diluted the

oil and caused premature wear of the crankshaft bearings. Although this was a simple mistake, it does point to the necessity of thorough training

for operators of alternative fuel vehicles.

** Biodiesel blends other than B100 are not considered by the Department of Energy to be alternative fuels under the Act.
reading. From these records, the inuse fuel economy of the vehicle can

be calculated. When the vehicle is

tested for emissions on the transportable chassis dynamometer, the

fuel economy is also measured.

As in other instances, in-use fuel

economy for large trucks varies 

from refueling to refueling because

of factors such as variations in driving styles and day-to-day duties.

Measurements obtained on a chassis

dynamometer, on the other hand, are

taken under tightly controlled conditions, and therefore exhibit less variation. As was the case in previous

discussions, the disadvantage of the

dynamometer tests is that the incorporated driving cycle may not be

representative of the vehicle’s 

normal operation.

With the exception of the New York

City garbage packers, all large trucks

in the Federal demonstration program have manual transmissions 

and cannot accommodate the Central

Business District dynamometer driving cycle. Consequently, they were

all tested using West Virginia

University’s 5-peak cycle. The

garbage packers, on the other hand,

were tested using the Central

Business District driving cycle.

Figure 39 summarizes the fuel economy data available to date for the

vehicles in the Federal heavy-duty

vehicle demonstration program. All

information is presented on a mile

per diesel-equivalent-gallon basis. 

So far, most of the alternative fuel

vehicles have exhibited both in-use

and dynamometer fuel economy

somewhat less than their diesel 

counterparts.

A number of trucks operating on 

35 percent biodiesel blend (not

presently considered by the U.S.

Department of Energy to be an alternative fuel) in Sheldon, Iowa, were

recently added to the program.

Although West Virginia University

personnel have visited the site and

taken fuel economy measurements

using the portable chassis dynamometer, there are insufficient 

in-use refueling data to report at this

time. Also, a number of large trucks

operating on liquefied natural gas in

Texas have recently been added to

the heavy-duty demonstration program, but West Virginia University

personnel have not yet conducted

tests on these trucks.

63

Figure 39. Fuel economy data available to date in the Federal heavyduty vehicle demonstration program

* B35 is not considered an alternative fuel

by the U.S. Department of Energy at this

time. ** Based on a small sample of preliminary

data (diesel data not yet available).

E-95

Diesel

Illinois,

line haul

B35*

Diesel

Iowa, line haul,

Mack E6 engine

Texas, line haul-LNG**

E-95

Diesel

Minnesota and Nebraska

road Maintenance

CNG

Diesel

New York,

garbage packer

B35*

Diesel

Iowa, line haul,

DDC Series 60 engine

B35*

Diesel

Iowa, line haul,

Cummins N14 engine

Heavy-Duty Vehicles

M65-B0344039
Cost

Keeping operating costs low is critical

to successful heavy-duty vehicle operations, as it is for service functions

performed by such vehicles as delivery vans. For example, the American

Trucking Association reports that in

line-haul trucking, the profit margin is

very narrow—on the order of 2 percent. This means that any increase in

operating cost either makes the operation unprofitable or increases the

price the consumer must pay.

Incremental Acquisition Costs

Acquiring a new alternative fuel

heavy-duty truck has generally

required several steps:

• Identifying and acquiring an

appropriate alternative fuel engine

• Acquiring the fuel system

• Acquiring the chassis

• Hiring an engineering firm to

design and execute the build-up of

the vehicle.

As expected, equipping a heavy-duty

truck to use alternative fuels is more

expensive than equipping a similar

truck to operate on diesel. In the case

of compressed natural gas, heavyduty engines carry an incremental

cost of $15,000 to $20,000. The

incremental cost of the fuel system

exceeds the incremental cost of the

engine, and it differs depending on

type of chassis and the fuel of interest. The liquefied natural gas fuel system for trucks recently added to the

Federal demonstration program cost

about $12,000. Other incremental

costs are associated with designing

and executing vehicle build-up. The

design phase costs about $30,000 per

vehicle, and actual build-up costs are

about $15,000 per vehicle.

These expenses are a major disincentive to fleet operators interested

in using alternative fuel trucks.

However, as the heavy-duty 

alternative fuel market develops,

such costs are expected to decrease.

Beginning in 1996, several chassis

manufacturers will begin offering

alternative fuel trucks as a package,

eliminating the need to go through

the steps outlined above. In principle, an alternative fuel engine should

not be inherently a great deal more

expensive to manufacture than a

diesel engine. Therefore, as the market expands, and research and development costs are recouped, the

engine cost should approach the cost

of diesel engines. The same can be

said for chassis costs.

The fuel system for compressed and

liquefied natural gas, in contrast, is

inherently more complex than a

diesel fuel system and will probably

continue to be more expensive.

However, the fuel system cost is a

relatively small part of the total cost

of the vehicle. A small incremental

cost for the fuel system could easily

be recovered in lower fuel costs.

Comparative Fuel Costs

Truck fleets tend to consume large

amounts of fuel, making fuel cost a

large part of the total operating cost

of a trucking company—second only

to personnel costs. For this reason, a

change of a few cents per gallon can

make a substantial impact on the

64

Heavy-Duty Vehicles
ability of alternative fuels to compete

in the trucking business.

As noted previously, the cost of

alternative fuels varies from one fuel

to another, both regionally and over

time. Federal and state taxes also 

figure heavily in fuel cost. 

The Department of Energy’s publication entitled Guide to Alternative

Fuel Vehicle Incentives and Laws

itemizes many of the varying state

incentives and taxes applicable to

purchasers of alternative fuels.

Figure 40 shows representative fuel

cost per diesel equivalent gallon for

the fuels being used in the Federal

heavy-duty vehicle demonstration

program. Federal and state taxes are

included in the figures.

The costs presented for ethanol,

compressed natural gas, and diesel

are based on published national average station prices. However, comparative prices are not available for liquefied natural gas because of the

lack of infrastructure for this fuel.

The same is true for biodiesel

blends, which, other than neat

biodiesel (B100), are not considered

by the Department of Energy to be

alternative fuels under the provisions

of the Act. Instead, a cost is presented for B35 (a low-level biodiesel

blend) based on the price paid at the

Federal biodiesel demonstration site

in Sheldon, Iowa. The cost shown 

for liquefied natural gas is based on

the cost at a liquefaction plant for

liquefied natural gas with 95 percent

to 97 percent methane content.

Currently, there are 15 liquefaction

plants throughout the country. For 

a trucking company that is not 

located near a liquefaction plant,

transportation cost adds about $0.07

per diesel equivalent gallon for every

100 miles from the plant.

It is clear from Figure 40 that compressed and liquefied natural gas can

potentially save a trucking company

money, but that saving is not automatic. The total saving per vehicle

depends on the number of miles the

vehicle travels per day and the cost

differential between the alternative

fuel and diesel. This cost saving must

be balanced against the incremental

cost of the alternative fuel vehicle

and any infrastructure changes

required. Trucking companies expect

a payback period of two to three

years to justify investing in alternative fuels. There are indications that

natural gas may be economically justified in some high-mileage applications right now. As the incremental

cost of natural gas vehicles decreases, a greater variety of trucks will be

able to reap economic benefits from

using natural gas. Economic advantage is the only force great enough to

drive the widespread use of alternative fuels in trucking.

65

Figure 40. Average retail fuel 

costs per diesel equivalent gallon

(with tax)

* Taxed as CNG.

** Taxed as “special motor fuel.”

✝ Price in Sheldon, IA, only. B35,

a low-level biodiesel blend, is not 

considered an alternative fuel by the 

U.S. Department of Energy at this time.

Heavy-Duty Vehicles

M65-B0344040
As mentioned previously, a difference of a few cents per gallon can

change the economics from a benefit

to a detriment for a specific trucking

application. This means that the fuel

tax structure will play a major role in

determining whether alternative fuels

are widely used. The Federal fuel tax

on the alternative fuels used in the

Federal heavy-duty vehicle demonstration program is shown in 

Figure 41. The tax is shown on an

equal energy basis for direct comparison. Two bars are included for liquefied natural gas because there have

been two interpretations regarding

the taxes applied to this fuel. Until

recently, liquefied natural gas could

be taxed either as compressed natural

gas or as a “special motor fuel”

(the category that liquefied petroleum gas falls into). However, on

August 7, 1995, the U.S. Internal

Revenue Service published a ruling

in the Federal Register requiring liquefied natural gas to be taxed at the

higher special motor fuel rate. This

deals a serious blow to the use of 

liquefied natural gas in trucking.

Several parties, including the

National Gas Vehicle Coalition and

the American Trucking Association,

are challenging the ruling.

Comparative Maintenance

Costs

Virtually all the heavy-duty alternative fuel vehicles in the Federal

demonstration program cost more to

maintain than their diesel counterparts. Most vehicles in the program

represent prototype, field-test technology, and part of the reason for

deploying and tracking them is to

work out the bugs in the technology

so it can be moved closer to commercialization. Higher maintenance

costs are to be expected for such

vehicles. As alternative fuel engine

manufacturers accumulate 

experience through such programs,

the reliability of the engines will

increase and maintenance costs

should approach those of their diesel

counterparts. Beginning in 1996, a

vehicle evaluation program modeled

after the transit bus program will be

initiated to evaluate the maintenance

costs of the newly available production heavy-duty alternative fuel vehicles side by side with comparable

diesel vehicles.

Summary

The heavy-duty alternative fuel

industry is still in its early stages of

development. The Federal heavyduty alternative fuel demonstration

program has been a catalyst in that

development process. The feasibility

of new technologies has been

demonstrated with the Archer

Daniels Methanol trucks running on

ethanol. Technology has been refined

66

Heavy-Duty Vehicles

Figure 41. Federal fuel tax per diesel

equivalent gallon

* Taxed as CNG.

** Taxed as “special motor fuel.”

*** A low-level biodiesel blend not 

currently considered by the Department 

of Energy to be an alternative fuel under 

the provisions of the Act.

M65-B0344041
through on-road field testing using

the Vons compressed natural gas

truck. Acceptance of alternative fuel

vehicles has been increased through

use of the United Parcel Service

compressed natural gas delivery

vans. Finally, technology has been

moved closer to commercialization

through the use of the Los Angeles

Times compressed natural gas truck.

In 1996, heavy-duty trucks equipped

to run on alternative fuels will be

available directly from the truck

manufacturers for the first time. The

industry has made its choice among

the many alternative fuels: the new

vehicles will be available for natural

gas only (both compressed and liquefied). Propane vehicles may

become available in 1997.

In 1996, the Federal demonstration

program will begin side-by-side 

evaluations of the new production

alternative fuel trucks with comparable diesel-powered trucks. This evaluation effort will be patterned after 

the Federal transit bus evaluation

project.

67

Liquefied Natural Gas Refueling

Becomes “Self Serve”

Liquefied natural gas is cryogenically stored at 260 degrees

Fahrenheit below zero. Because

it is a denser fuel than compressed natural gas and is stored

at a lower pressure, liquefied natural gas fuel tanks are smaller

and lighter than compressed natural gas cylinders. This gives 

liquefied natural gas an advantage for trucks that require a 

long operating range between

refuelings.

In the past, however, refueling with liquefied natural gas looked like a

scene out of a NASA documentary. Trained technicians required special suits and face masks to protect themselves from the cryogenic liquid. The picture is now changing with the introduction of new “selfserve” liquefied natural gas refueling technology.

To date, three retail liquefied natural gas stations have been installed—

one each in Los Angeles, Denver, and Bloomfield, New Mexico. All

three of these stations are card operated and sell directly to the consumer. In Los Angeles, where one of the new test vehicles in the

Federal heavy-duty demonstration program will refuel, a discount is

offered to any customer who completes a short training course on the

use of the station. A station attendant refuels the vehicle when its driver

has not received the training.

Jeffery Beale, president of CH•IV Cryogenics, describes the new 

technology in this way: “Imagine fueling your personal gasoline 

vehicle . . . that’s how simple and safe our new installation has made

fueling an LNG vehicle.” The CH•IV design uses a single hose (analogous to a gasoline hose), and purges the fuel from the nozzle before

connecting or disconnecting, so the driver is not exposed to the fuel.

Heavy-Duty Vehicles

LNG fueling dispenser

Photo courtesy of CH•IV Cryogenics/PIX 03316
68
Overview

The Energy Policy Act of 1992 

(42 U.S.C. 13212 (a) and (b)) specifies minimum purchase requirements 

for alternative fuel vehicles in the

Federal fleet. The schedule for

acquiring light-duty alternative fuel

vehicles follows:

• FY 1993 5,000 vehicles

• FY 1994 7,500 vehicles

• FY 1995 10,000 vehicles

• FY 1996 25 percent of Federal

fleet acquisitions

• FY 1997 33 percent of Federal

fleet acquisitions

• FY 1998 50 percent of Federal

fleet acquisitions

• FY 1999 75 percent of Federal

and after fleet acquisitions

The Federal government normally

acquires about 50,000 vehicles each

year.

Although alternative fuel vehicles

have been under development for

more than a decade, their availability

from the automobile manufacturers

was not sufficient in calendar year

1992 to allow the various Federal

agencies to meet the requirements 

of the Act. The decision was made 

to use aftermarket conversions to fill

the gap until a sufficient number of

original equipment models could be

made available at a reasonable cost.

Aftermarket conversions involve

equipment additions after the vehicle

is sold, to allow vehicles originally

designed for one fuel to operate 

on another. There are many U.S.

companies that convert light-duty

gasoline vehicles to allow them to

operate on compressed natural gas 

or liquefied petroleum gas.

In February 1992, the National

Renewable Energy Laboratory initiated a competitive procurement for

aftermarket conversion of vehicles in

the Federal fleet. Such conversions

enable the vehicles to operate on an

alternative fuel. The procurement

was initiated to develop subcontracts

with several alternative fuel vehicle

conversion companies across the

nation, with the goal of converting

about 1,000 Federal government

vehicles. The U.S. Department 

of Energy provided the funding 

for these conversions. As of 

August 1995, about half of the 

targeted conversions were completed, with the remainder either 

on order or in the planning stages.

The conversion effort has succeeded

in helping the Federal government

meet the requirements of the Act

during a period of limited model

availability. Activities will be phased

down during 1996, however, because

original equipment availability has

significantly improved.

69

Aftermarket Vehicle

Conversions
70

Aftermarket Vehicle Conversions

Table 4 compares the availability 

of alternative fuel vehicles from the

original equipment manufacturers at

the start of the Federal light-duty

program in 1992, with their corresponding availability in 1996, and

illustrates the expanded product

availability during this time frame.

Program Description

At this time, light-duty vehicles are

commonly converted to operate on

one of two alternative fuels: compressed natural gas or liquefied

petroleum gas (propane).

Aftermarket conversions inherently

represent a compromise of vehicle

technology, so a key program objective is to obtain the highest-quality

conversions available. Consequently,

when selecting subcontractors to perform the work, experience, capabilities, and demonstrated ability to

meet the high performance criteria

were weighted more heavily than

price. With regard to actual equipment, only higher-quality, “closedloop, feedback” conversion kits were

used, because these are known to

provide the best emissions performance. Best industry practices were

required during installation of the

kits. For instance, all compressed

natural gas conversions were

installed according to the National

Fire Protection Association’s

Specification 52. This specification

includes detailed instructions for

installing the fuel system and tank.

Similarly, liquefied petroleum gas

conversions were installed according

to the National Fire Protection

Association’s Specification 58.

Vehicles converted to operate on

compressed natural gas have a 

minimum specified driving range 

of 70 miles. In most cases, however,

the range is substantially more. In

contrast, vehicles converted to operate on liquefied petroleum gas have 

a minimum specified driving range 

of 170 miles.

Table 4. Expansion of Alternative Fuel Vehicle Availability between

1992 and 1996

1992 Model Year Vehicles

Manufacturer Model Body Style Fuel

Chrysler-Dodge Ram van/wagon Full-size van CNG

GM-Chevrolet C1500/C2500 Full-size pickup CNG

GM-Chevrolet Lumina Mid-size sedan Ethanol

Ford F700 Medium-duty truck LPG

1996 Model Year Vehicles

Manufacturer Model Body Style Fuel

Chrysler-Dodge Ram van/wagon Full-size van CNG

Chrysler-Dodge Ram pickup Full-size pickup CNG

Chrysler-Dodge/

Plymouth Caravan/Voyager Minivan CNG

Ford Contour Compact sedan CNG/Bi-fuel

Ford Taurus Mid-size sedan Methanol

Ford Taurus Mid-size sedan Ethanol

Ford Crown Victoria Full-size sedan CNG

Ford F150/F250 Full-size pickup CNG

Ford Econoline Full-size van CNG

Ford F150/F250 Full-size pickup LPG/Bi-fuel

Ford F700 Medium-duty truck LPG
Each aftermarket vehicle conversion

is protected by a warranty that covers all installed conversion system

parts and associated labor for three

years or 36,000 miles, whichever

comes first. Conversion subcontractors are also responsible to repair 

or replace any engine, fuel system,

electrical, or electronic system components damaged by the installed

conversion equipment during this

period. As required by the provisions

of the Act, subcontractors are

required to sign individual warranty

agreements with Chrysler, Ford, and

General Motors.

The first light-duty vehicle conversions were completed during the

summer of 1994. Conversion activities are continuing through the date

of this writing.

Table 5 shows the total number of

conversions currently completed,

planned, or on order, by Federal

agencies as of August, 1995.

Figure 42 shows the distribution 

of conversions, by state, that are

completed, planned, or on order.

Figure 43 shows the distribution of

conversions, by vehicle type, that are

completed, planned, or on order.

Figure 43 illustrates that more than

90 percent of all conversions are taking place on pickups and vans. This

is a good sign because the original

equipment manufacturers are concentrating on producing these same

types of vehicles.

Most light-duty vehicle conversions

(more than 92 percent) are bi-fuel

conversions, which means that the

vehicle may operate on either gasoline or the designated alternative

fuel. The remainder are “dedicated”

conversions, which means that the

vehicles may operate only on the

designated alternative fuel.

The cost of a light-duty vehicle conversion depends on the alternative

fuel of interest, the level of conversion technology used, and the size 

71

Aftermarket Vehicle Conversions

Table 5. Conversions by Federal Agency

Agency CNG LPG Total Vehicles

Air Force 414 0 414

Marines 220 0 220

General Services Administration 160 40 200

Navy 97 0 97

National Institutes of Health 67 0 67

Forest Service 32 24 56

Other Federal Agencies 8 3 11

Totals 998 67 1065

Figure 42. States in which aftermarket conversions included in 

the program are located

397 67

50

60

67

182 132

110

CNG Conversions

LPG Conversions

M65-B0344042
or quantity of the fuel tanks. The

average total cost for each compressed natural gas conversion in 

the program is about $4,500. The

average total cost for each liquefied

petroleum gas conversion, on the

other hand, is about

$2,700. The overall cost 

of each conversion, especially in the case of compressed natural gas,

depends heavily on the

number and size of the

fuel tanks. The fuel tanks

specified for each conversion, in turn, depend on

the vehicle type and

desired range. For some

vehicles, more than one

tank is installed.

Where possible, every effort 

was made to target vehicles located

in cities designated by the U.S.

Department of Energy as “Clean

Cities.” Converted vehicles will be

operating in six of the 45 communities designated as Clean Cities (as 

of April 1, 1996): Atlanta; Denver;

Las Vegas; Washington, D.C.;

Albuquerque; and Colorado Springs.

Emissions Results

During the 1995 fiscal year, the program began testing emissions on a

limited number of these aftermarket

conversion vehicles. A very large test

matrix of vehicles and conversion 

kits would need to be tested to fully

answer the question of how various

conversion kits perform on a large

cross-section of vehicle types, given

the expected variability in individual

vehicle performance and emission test

results. As an initial step, emissions

testing was begun in 1995 on a 

limited number of vehicles included

in the Federal aftermarket conversion

program. Sixteen vehicles, including

eight new vehicle models, and two

different conversion kits (one each for

compressed natural gas and liquefied

petroleum gas) were included in this

effort. A list of the number and type

of vehicles is shown in Table 6.

As stated earlier, the conversion program was designed to use only highquality conversion systems. GFI

Control Systems kits were installed

in the vehicles converted to operate

on compressed natural gas. Impco

ADP Systems were installed in the

vehicles converted to operate on liquefied petroleum gas. These modern

conversion kits use electronic controls to continually adjust the air/fuel

ratio based on a signal from the

exhaust gas oxygen sensor. These

closed-loop, feedback control conversion kits represent the state of the

art of equipment available in 1995,

and they constitute a minimum 

technological requirement for the

conversion program because they are

generally expected to be cleaner and

more reliable than the older nonfeedback kits.

In addition to having closed-loop

feedback control, the GFI kits can 

be electronically calibrated to a 

specific engine model for improved

emissions performance. Consequently,

an attempt has been made to test

emissions on only those compressed

natural gas vehicles in the conversions

program for which an engine calibration exists. Furthermore, all vehicles

included in the Federal conversion

program were required to conform 

72

Aftermarket Vehicle Conversions

Figure 43. Vehicle conversions 

by vehicle type (1,065 total)

M65-B0344043
to the U.S. Environmental Protection

Agency’s emissions requirements for

conversions (see sidebar on page 75).

Other criteria used to select vehicles

for emissions testing include low

mileage before conversion, and similarity to original equipment alternative

fuel vehicle models available from the

manufacturers.

To establish an emissions baseline,

each vehicle was tested on California

Phase 2 reformulated gasoline before

conversion. The conversion kit 

was installed shortly after (within

1,000 miles of) the baseline test,

and subsequent emissions tests were

performed first on reformulated

gasoline and then on the alternative

fuel (compressed natural gas or 

liquefied petroleum gas). The compressed natural gas used for emissions testing was specially blended

from tightly controlled constituent

gases, and the liquefied petroleum

gas was produced to conform with

the industry-accepted specification

(known as HD5) for transportation

propane fuel. All emissions tests

conformed to the Environmental

Protection Agency’s Federal Test

Procedures (see sidebar on test procedures on page 21) using the Urban

Dynamometer Driving Schedule. In

addition, standard one-hour diurnal

heat-build and hot-soak evaporative

test procedures were included. Plans

are to test the vehicles once each

year to establish emissions durability

over time and accumulated mileage.

Although the first-round emissions

results from the vehicles in the

Federal aftermarket conversion program are somewhat mixed, the following general observations can be

made. The results are summarized 

in Table 7.

In general, installing compressed

natural gas conversion kits did not

adversely affect the reformulated

gasoline emissions profile. In other

words, for most vehicles and most

constituents, the difference was 

negligible between the emissions 

recorded for reformulated gasoline

before and after conversion (less than 

10 percent). For the liquefied petroleum gasoline conversions tested,

two of three showed relatively large

increases in emissions when tested

73

Aftermarket Vehicle Conversions

Table 6. Converted Vehicles Emissions Tested in 1995

Compressed Natural Gas (kit make and model: GFI)

Manufacturer Model Quantity

Plymouth Acclaim 2

Ford Taurus 2

Chevrolet Astro (minivan) 1

Dodge (minivan) 2

General Motors Safari (minivan) 2

Dodge B250 full-size passenger van 2

General Motors C1500 pickup 2

Total CNG 13

Liquefied Petroleum Gas (kit make and model: Impco ADP)

Manufacturer Model Quantity

Ford F150 pickup 2

Ford Taurus 1

Total LPG 3
74

Aftermarket Vehicle Conversions

Table 4. Emission Test Results from Aftermarket Conversions

Washington DC Conversion Vehicles

Vehicle Model Before Conversion (RFG) After Conversion (RFG) After Conversion (CNG)

Model Year NOx CO NMHC NOx CO NMHC NOx CO NMHC

Acclaim 1992 0.23 4.13 0.15 NC

Acclaim 1992 0.46 3.52 0.11 NC NC

Astro 1992 1.01 2.42 0.48 NC NC

Caravan 1992 0.75 1.30 0.23

Caravan 1992 0.53 1.96 0.24 NC

Safari 1993 1.14 4.92 0.46 NC NC NC

Safari 1993 1.20 6.19 0.54 NC

Taurus 1994 0.22 1.08 0.09 NC NC

Taurus 1994 0.17 0.98 0.08 NC NC

Denver CNG Conversion Vehicles

Vehicle Model Before Conversion (RFG) After Conversion (RFG) After Conversion (CNG)

Model Year NOx CO NMHC NOx CO NMHC NOx CO NMHC

B250 1994 2.31 8.66 0.84 NC NC NC

B250 1994 0.65 2.75 0.16 NC NC

C1500 1994 0.49 2.88 0.17 NC NC

C1500 1994 0.61 3.98 0.18 NC NC NC

Denver LPG Conversion Vehicles

Vehicle Model Before Conversion (RFG) After Conversion (RFG) After Conversion (LPG)

Model Year NOx CO NMHC NOx CO NMHC NOx CO NMHC

F150 Pkup 1994 1.20 0.66 0.09 NC

F150 Pkup 1994 0.88 0.80 0.08 NC NC

Taurus 1994 0.25 0.80 0.09 NC NC

Moderate emissions decrease (10%–50%)

NC = No change (i.e., less than 10%)

Large emissions increase (>50%)

Large emissions decrease (>50%) Moderate emissions increase (10%–50%)
on reformulated gasoline after conversion. This indicates that either 

the kit or the installation had a negative impact on gasoline emissions

performance. This is an area of concern for conversion systems, but at

this point the test sample size is too

small to make general conclusions.

Additional testing, designed to further investigate this problem, is

planned in 1996.

It should be noted that the liquefied

petroleum gas conversion kit is of a

substantially different design than

the compressed natural gas kit. It is

therefore impossible in this program

to make any comparisons between

compressed natural gas and liquefied

petroleum gas fuel, even if both tests

were done on the same make and

model of vehicle.

The emissions comparison between

reformulated gasoline and the alternative fuel in these conversions is

not promising. Six of the nine 

vehicles converted in Maryland

recorded substantial increases in

oxides of nitrogen when tested on

compressed natural gas, and five of

nine recorded substantial increases 

in carbon monoxide when tested on

compressed natural gas, relative to

the corresponding levels obtained in

the tests on reformulated gasoline.

Seven of the nine Maryland vehicles

achieved a decrease in non-methane

hydrocarbon emissions when tested

on compressed natural gas, relative

to the values obtained in tests on

reformulated gasoline.

In the case of the vehicles converted

and tested in Denver, all those converted to compressed natural gas

exhibited a small decrease in oxides

of nitrogen, a substantial decrease in

non-methane hydrocarbon emissions,

and a substantial increase in carbon

monoxide emissions when tested on

compressed natural gas relative to

the corresponding values obtained in

tests on reformulated gasoline.

Two of the three liquefied petroleum

gas conversions in Denver showed

no change in oxides of nitrogen,

and all three showed a substantial

decrease in carbon monoxide, and a

substantial increase in non-methane

hydrocarbon emissions when tested

on liquefied petroleum gas relative 

75

Aftermarket Vehicle Conversions

Emissions Standards for Aftermarket Conversions

In 1974, the U.S. Environmental Protection Agency issued Mobile

Source Enforcement Memorandum No. 1A, which states the agency’s

interim policy with regard to enforcing the “tampering” prohibition of

the Clean Air Act. The primary objective of this memorandum was to

ensure unimpaired emission control of motor vehicles throughout their

useful lives. This memorandum, in effect, states that aftermarket conversion of vehicles to an alternative fuel will not be considered “tampering” if the installer has a “reasonable basis” for knowing that such

modifications will not adversely affect emissions performance. As a

result of increased aftermarket conversion activity, an additional fact

sheet was issued by the Environmental Protection Agency on March 4,

1993, stating that a “reasonable basis” may include certificaton of the

conversion kit by the California Air Resources Board, the Colorado

Department of Health (for high-altitude areas), or by performing other

Federally-recognized test procedures. All vehicles included in the

Federal conversion program were required to conform to these criteria.

In 1994, the Environmental Protection Agency established new certification standards for aftermarket conversions. In order for a conversion

to count as a “clean fuel vehicle” and be eligible for the Environmental

Protection Agency’s fleet program, or for a state to claim emissions

benefits, the converter must certify the converted vehicle to these new

standards. Vehicles can still be converted under Memorandum 1A, but

they cannot then be used for claiming emissions benefits. The Energy

Policy Act does not require that a conversion meet these new certification standards to be counted as an alternative fuel vehicle.
to the corresponding values obtained

in tests on reformulated gasoline.

The results from this study cannot be

considered comprehensive or conclusive because of the limited number

and types of vehicles tested, especially for liquefied petroleum gas.

However, a trend has been established for vehicles converted to 

compressed natural gas. Typically,

they exhibit an emissions benefit in

terms of non-methane hydrocarbons,

but they tend to realize substantial

increases in either oxides of nitrogen

or carbon monoxide. Substantial

decreases in non-methane hydrocarbons are to be expected for compressed natural gas vehicles, because

the total hydrocarbons in the exhaust

are composed of at least 90 percent

to 95 percent methane. Too few liquefied petroleum gas conversions

have been tested to establish a trend,

but the initial testing has highlighted

two areas of concern. The first is the

emissions performance on gasoline

after conversion, and the second is

the increase in non-methane hydrocarbons when tested on liquefied

petroleum gas after conversion.

These early emissions results for

aftermarket conversions, when contrasted with the considerable emissions improvements obtained with

dedicated compressed natural gas

vehicles from the original equipment

manufacturers (see the discussions

on light-duty vehicle emissions,

pages 20–28), highlight the need 

to consider both the fuel and the

vehicle technology when evaluating

options for reducing air pollution.

Although using dedicated compressed natural gas vehicles from the

original equipment manufacturers,

for example, yields substantial emissions benefits, it cannot be assumed

that all fuel system technologies will

achieve this end. The aftermarket

conversion vehicles that have been

emissions tested so far will continue

to be monitored, and the need for

additional testing or the inclusion of

additional vehicles will be evaluated.

Summary

Aftermarket conversions can play 

an important role in the transition to

more widespread use of alternative

fuel vehicles. However, the disappointing emissions performance of

these relatively advanced closed-loop

feedback kits to date raises the question of their overall contribution to

reducing emissions. In addition,

many less advanced and less expensive kits exist, and the technical 

literature confirms that they 

generally exhibit worse emissions

performance.

Nonetheless, conversions currently

dominate the alternative fuel market.

Even with increasing model availability from original equipment 

manufacturers, many conversion

strategies involve significant price

advantages, which may eventually

delay expansion of the original

equipment manufacturer market.

76

Aftermarket Vehicle Conversions
77

Safety Incidents 

In general, the overall Federal

demonstration fleet continues to

experience a very good safety record.

Safety issues related to alternative

fuels or the alternative fuel systems

have very rarely been raised. In

1994, there were two serious incidents involving Chevrolet C2500

dedicated compressed natural gas

pickup trucks. High-pressure fuel

tanks failed on both vehicles, resulting in equipment loss, but no one

was seriously injured. Neither vehicle was part of the General Services

Administration fleet or included in

the Federal demonstration program.

The Chevrolet C2500 vehicles have

all been removed from the General

Services Administration fleet, and

Chevrolet no longer sells this vehicle. Details of this incident were

reported last year.

Two new safety incidents occurred 

in 1995. Both were related to compressed natural gas fuel tanks. The

first was much less serious than the

1994 incident. Damage was discovered on the under-vehicle fuel tank

on two compressed natural gas

Dodge Ram vans during the incoming vehicle inspection, which is routinely conducted before scheduled

vehicle emissions testing. The damaged tanks were emptied and tank

valves were closed to isolate the tank

before any tests were conducted. The

fleet manager at the military base

where the vehicles were operating

was notified of the problem, and

inspectors recommended that the

tanks be thoroughly inspected and

replaced if necessary. No one was

injured and the vehicle was not 

damaged.

In the other safety incident reported

during 1995, compressed natural 

gas pressure relief devices made by

Mirada Controls failed. This device

has been used on a variety of compressed natural gas vehicles, including transit buses. The device failure

can result in sudden release of the

compressed natural gas stored in the

fuel tank. The potential for damage,

including fire, depends on the presence of an ignition source and other

circumstances.

Approximately 100 of these valves

have failed on buses operated in 

the United States during the past 

two years. However, none of these

vehicles is included in the Federal

demonstration program.

To date, the incidents noted above

have resulted in minimal property

damage and no personal injury. The

National Highway Traffic Safety

Administration has issued a safety

recall for the Mirada pressure relief

device manufactured between June

1991 and February 1993. In addition,

the Natural Gas Vehicle Coalition

Safety
78

Technical Committee is conducting

research in areas of pressure relief

device design and high-pressure

compressed natural gas discharge

behavior, and recommendations for

improvements are expected to be

forthcoming.

Safety
79

To meet the demands that the

increasing numbers of alternative

fuel vehicles are placing on the U.S.

marketplace, an associated infrastructure has developed. This infrastructure, consisting of refueling

sites and maintenance and storage

facilities, is the fabric that holds the

components of the alternative fuel

industry together. Growth of this

infrastructure has been stimulated 

by various legislative incentives,

such as the Alternative Motor Fuels

Act of 1988, the Clean Air Act

Amendments of 1990, the Energy

Policy Act of 1992, and Executive

Order 12844 (Federal Use of

Alternative Fueled Vehicles, April

1993). Also, the U.S. Department of

Energy has promoted infrastructure

development within the context of 

its Clean Cities Program

Refueling Sites

Expanded development of refueling

sites faces a number of hurdles,

depending on the alternative fuel of

interest. For methanol and ethanol

refueling stations, it is relatively easy

to install a new in-ground or aboveground fuel storage tank. Special

attention must be given to the choice

of materials used to make the tank,

pump, and hoses, however, because

alcohol fuels are highly corrosive.

For compressed natural gas, there 

is a variety of refueling technology

from which to choose. However, all

such options are more expensive

than those for alcohol fuels. A slowfill system uses a small compressor

and has the lowest cost. With this

kind of arrangement, vehicles are

usually attached to a refueling hose

overnight, with the typical refueling

time being about eight hours. A 

fast-fill system, on the other hand,

requires a large and expensive compressor station. Using this kind of a

system, a vehicle can typically be

refilled with compressed natural gas

in about the same amount of time it

takes to refill with diesel or gasoline.

Most public access compressed natural gas stations are fast-fill, but they

can cost $200,000 to $300,000 to

build.

The absence of consistent zoning

and safety ordinances continues to

hamper the installation of alternative

fuel refueling stations. Because each

municipality has its own unique

requirements, equipment and installation procedures cannot be standardized, which, in turn, leads to

higher costs.

Light-Duty Vehicles

Despite the above considerations, the

total number of alternative fuel refueling stations continues to increase.

The percentage distribution of compressed natural gas, methanol, and

ethanol refueling sites in the United

States is illustrated in Figure 44. As

of August 1, 1995, there were more

than 1,100 compressed natural gas

stations, as well as 88 methanol 

Infrastructure

Support
stations, and 36 ethanol stations.

Figure 45 shows the geographic distribution of all these stations

throughout the country. About twothirds of the methanol stations are in

California.

The total number of refueling sites for alternative

fuels has more than

quadrupled in the past 

five years. Although the

number of ethanol and

methanol refueling sites

did not expand in the past

year, the number of compressed natural gas sites,

according to the American

Gas Association, grew at a

rate of three to four stations per week. The total

number of operational compressed

natural gas stations reported by the

American Gas Association is 1,107,

representing a growth of almost 20

percent in one year. Of these sites,

about three-fifths are open to the

public, either with full access or

access by arrangement.

A 1992 survey by the National

Propane Gas Association reported

3,300 liquefied petroleum gas 

sites in the United states that offer

propane as a motor fuel. However,

the Liquefied Petroleum Gas Clean

Fuels Coalition recently estimated

that there are now as many as 11,000

sites where propane can be obtained

for this purpose.

Transit Buses and Heavy-Duty

Vehicles

Transit bus agencies and heavy-duty

fleet operators generally install their

own fueling stations and do not use

public facilities. Regardless of the

fuel in question, installing an alternative fuel refueling facility poses

unique challenges in terms of setup

costs and safety.

Maintenance Facilities

The General Services Administration

reports that, as a rule, alternative fuel

vehicle maintenance was sometimes

difficult in the early years of the program (1991–1992), but is no longer

the problem it once was. Although

this trend does not alleviate the need

for adequate maintenance facilities

and qualified service personnel, it

relieves the pressure to provide large

numbers of garages and technicians

dedicated solely to the repair of

alternative fuel vehicles.

Light-Duty Vehicles

In light of the above comments,

original equipment manufacturer

dealerships have been retained to

perform all maintenance on lightduty alternative fuel vehicles in the

Federal demonstration program,

using facilities and staff already in

place. Personnel from each dealership has been factory-trained to service the specific alternative fuel

vehicles sold by that dealership.

These individuals are particularly

knowledgeable about the vehicle’s

fuel system and electronics, allowing the dealerships to provide reasonable service for a fair price.

Conversions

Maintaining light-duty aftermarket

conversion vehicles is a bit more

problematic. The conversion vehicles

in the Federal demonstration program are returned to their respective

80

Infrastructure Support

Figure 44. Compressed natural gas,

methanol, and ethanol refueling sites

(as of August 1, 1995)

M65-B0344044
shops for service. In general, though,

there are not currently enough qualified technicians to staff the demand. 

To expand this pool, the U.S.

Department of Energy’s Office of

Transportation Technologies, in 

compliance with section 411 of 

the Energy Policy Act of 1992, has

funded a national program to certify

training programs for technicians

who convert vehicles to alternative

fuels, and who maintain and repair

the vehicles and refueling stations.

This program is called CHAMP

(Certification of Higher-learning in

the Alternative Motor Fuels

Program). The CHAMP team is

composed of 16 charter organizations that represent automobile manufacturing, education, certification,

alternative fuels production, vehicle

conversions, automotive service, and

the public. It is expected to provide

the guidance and resources necessary

to stimulate the certification program’s development, implementation, and evaluation.

Transit Buses and Heavy-Duty

Vehicles

Expanding the availability of maintenance facilities for alternative fuel

transit buses and heavy-duty vehicles

encompasses two somewhat divergent scenarios. With regard to buses,

a transit agency generally performs

its own maintenance on the alternative fuel vehicles it operates, or it

relies on an engine dealership to do

so. This is true for all the transit

agencies with vehicles in the Federal

81

Infrastructure Support

Figure 45. Geographic distribution 

of alcohol and compressed natural 

gas refining sites across the country

M65-B0344045
82

demonstration program. Because a

transit agency usually has only one

or two central sites for maintaining

its entire fleet, those sites must be

outfitted for the alternative fuels,

and for diesel, used by the agency.

The agencies’ technicians are dualtrained to quickly repair diesel and

alternative fuel systems, or they 

gain on-the-job experience with the

alternative fuel technology through

repeated exposure to many vehicles.

The fact that there are many vehicles

involved is the key factor that makes

the provision of maintenance facilities economically valid.

In contrast, there are often only a

few alternative fuel heavy-duty vehicles at any given site, where the lack

of maintenance technicians having

experience in alternative fuel technologies is a problem. In addition,

many of the maintenance shops 

frequented by heavy-duty vehicles

do not have adequate ventilation, or 

sufficient detection devices to safely

accommodate gaseous fuels indoors.

Although both situations are improving, progress is slow. Few maintenance facilities can justify upgrading

their equipment and training their

personnel to service alternative fuel

vehicles when the total pool of such

vehicles in a given location is so

small (perhaps fewer than ten).

Vehicle Storage

Although storing alcohol vehicles

presents no particular problem,

special precautions must be taken

before housing gaseous fuel vehicles

indoors. Indoor storage requires gas

detectors and adequate ventilation

systems. For this reason, many

underground parking facilities do 

not permit compressed natural gas 

or liquefied petroleum gas vehicles

to be left on their premises. This presents a problem for pickup and delivery vehicles operating in urban areas.

In the long term, this issue will need

to be resolved if compressed natural

gas and propane are to gain widespread use in this type of service.

Where We Are

The infrastructure for light-duty

alternative fuel vehicles is growing at

a pace that parallels the number 

of alternative fuel vehicles being

deployed. No significant impediment

to further expansion is evident. The

infrastructure for alternative fuel

transit buses is also expanding in

concert with the number of those

vehicles being deployed. 

On the other hand, there have been

significant infrastructure problems

associated with the use of alternative

fuels in large trucks. As an example,

the operators of almost every large

truck in the Federal demonstration

program have encountered problems

with some aspect of refueling, maintenance, or storage. The reported

problems range from inconsistencies

in biodiesel blending to incompatible

connectors for liquefied natural gas

refueling. Nonetheless, the knowledge gained in addressing such problems helps advance the use of alternative fuels in heavy-duty applications, and progress is being made on

several fronts.

Infrastructure Support
83

Figure 46. Number of compressed 

natural gas vehicles in U.S. fleets

Alternative Fuel Vehicles

in Use

The number of light-duty alternative

fuel vehicles operating in U.S.

Federal and non-Federal fleets has

increased steadily over the past several years. Figures 46, 47, and 48

depict the growth in deployment of

these vehicles since 1992. These

same figures include projections of

the totals that will be in service by

the end of 1996. The projections

have been developed by the U.S.

Department of Energy’s Energy

Information Administration using

automotive industry sources and 

fleet vehicle acquisition estimates.

Although not reflected in 

Figure 48, the Energy Information

Administration projects an increase

in ethanol flexible-fuel vehicles to

nearly 32,000 units in the near future

because of an announcement that

Chevrolet will manufacture an

ethanol-compatible pickup truck.

Light-duty vehicles fueled by liquefied petroleum gas (propane) are

estimated to be the largest group of

vehicles in the United States operating on a fuel other than gasoline.

Nearly all the propane vehicles are

conversions, making it difficult to

determine their numbers. However,

the best information currently available puts the total at approximately

217,000 units.

In January 1995, a survey of transit

bus agencies was conducted by the

American Public Transit Association.

The results indicated an increase in

the number of alternative fuel transit

buses in service in 1995 compared 

to the number in service in 1994. 

Of more than 52,000 transit buses

Vehicle Availability

Figure 47. Number of methanol (M85)

vehicles in U.S. fleets

M65-B0344046 M65-B0344047
84

currently in operation around the

country, about 5 percent of them now

operate on alternative fuels. The

market penetration of alternative

fuels in the transit bus sector is substantially ahead of the corresponding

level for any other transportation sector—a situation that may reflect the

nearly ideal characteristics of transit

buses as applications for alternative

fuels.

Model Availability

In 1995, the manufacturers offered

six compressed natural gas models

(including dedicated minivans, pickups, a dedicated van, a bi-fuel van,

and a bi-fuel pickup), two 85 percent

methanol flexible-fuel sedans, one 

85 percent ethanol flexible-fuel

sedan, and one liquefied petroleum

gas medium-duty truck. The models

available in 1996 will include one 

85 percent methanol sedan, one 

85 percent ethanol sedan, six compressed natural gas vehicles (including dedicated minivans, pickups,

vans, and sedans), a bi-fuel van, a 

bi-fuel pickup, and one liquefied

petroleum gas medium-duty truck.

The Energy Policy Act of 1992 

(42 U.S.C. 13212 (a) and (b)) mandates that 25 percent of all new vehicle purchases made in 1996 by the

Federal government be alternative

fuel vehicles. Based on projected

vehicle acquisitions, the General

Services Administration will be

required to purchase approximately

8,600 units. The Energy Policy Act

also requires new acquisitions by

state fleets and fuel provider fleets to

include a certain percentage of alternative fuel vehicles. The demand for

alternative fuel vehicles is expected

to be high in the coming years as 

targeted fleets work to meet the 

mandated requirements.

Vehicle Availability

Figure 48. Number of ethanol (E85)

vehicles in U.S. fleets

M65-B0344048
85

The National Alternative Fuels Hotline,

the U.S. Department of Energy’s 

primary source of information 

about alternative fuels

Information dissemination is 

an important component of the 

U.S. Department of Energy’s program to expand the use of alternative

fuels in the United States. Accurate,

timely, and readily available information can only help to hasten 

public acceptance and adoption of

alternative fuels and alternative fuel

vehicles. Programs to provide information about alternative fuels are

mandated by the same Federal legislation that requires alternative fuel

vehicle demonstrations and data collection activities. The legislation that

requires these activities includes the

Alternative Motor Fuels Act of 1988,

the Clean Air Act Amendments of

1990, the Energy Policy Act of 1992,

and Executive Order 12844.

The Alternative Fuels 

Data Center

To make the best possible use of 

all the information being collected

through the various vehicle demonstration programs, the Office of

Alternative Fuels in the U.S.

Department of Energy’s Office of

Transportation Technologies established the Alternative Fuels Data

Center at the National Renewable

Energy Laboratory. This center

serves as the focal point for the

information collected in all the vehicle demonstration programs. The

Alternative Fuels Data Center maintains information on line in computerized databases. Hard copies are

available as well, and are distributed

through the National Alternative

Fuels Hotline (1-800-423-1DOE).

Engineers in the Alternative Fuels

Data Center validate the quality of

the information they receive from

various sources using many computerized, statistical, and manual procedures. If the data meet these quality

checks, they are loaded into a production database. If the data do not

satisfy the quality standards, they 

are further investigated to determine

whether errors exist that can be corrected, and whether procedures can

be implemented to prevent similar

errors in the future. Once loaded into

the production database, the information is analyzed and reports are

developed. All information in the

Information

Dissemination

Photo courtesy of Information Resources, Inc./PIX 03315
86

database is made available to other

researchers, private industry, and

anyone else interested in the information, free of charge.

Several methods are available 

for accessing information in the

Alternative Fuels Data Center. The

primary method is via the World

Wide Web on the Internet, using

browser software such as Mosaic.

Because this graphical user interface

is very intuitive and user friendly, it

is gaining wide popularity throughout industry and government. The

World Wide Web facilitates access 

to raw data, as well as complete

reports, graphics, photographs,

sound, and even movies. As examples, the Alternative Fuels Data

Center currently maintains maps of

alternative fuel refueling sites, databases of biofuels and alternative

fuels literature, and the complete

texts of quarterly newsletters and

many alternative fuel reports, all 

of which can be directly accessed 

via the World Wide Web at

http://www.afdc.doe.gov.

Users of the Alternative Fuels Data

Center may also access information

by programming their own queries or

using commercial data query tools.

These methods are recommended for

the serious researcher rather than the

casual user.

In addition to direct measurements

taken on vehicles (for example,

emissions and fuel economy), data

center personnel have established a

comprehensive textual database of

research and demonstration information pertaining to alternative fuels.

Materials that are not copyrighted

can be distributed as complete documents. Copyrighted information is

maintained only in the form of literature citations. Individuals interested

in obtaining these materials may call

the National Alternative Fuels

Hotline. (1-800-423-1DOE).

The hotline staff also maintains a

large inventory of general information of interest to the public, as 

well as to government workers,

researchers on alternative fuels, and

to representatives of the supporting

industries. These materials are distributed free of charge by the Hotline

on request.

The Alternative Fuels Data Center is

constantly producing and updating a

series of publications. For example, a

quarterly newsletter is published that

currently has a hard copy circulation

of nearly 15,000. The newsletter is

also available on line.

The National Alternative Fuels

Hotline is the U.S. Department of

Energy’s primary source of information concerning alternative fuels and

related issues. Hotline operators have

immediate access to all databases

maintained by the Alternative Fuels

Data Center, as well as to information that has not yet been placed in

production. The hotline’s staff can

immediately answer any and all

questions about alternative fuels,

process requests for information,

and refer callers to other data 

sources and organizations.

In summary, information dissemination is one of the most important

facets of the U.S. Department of

Energy’s strategy for increasing the

use and acceptance of alternative

Information Dissemination
fuels. The Alternative Fuels Data

Center, and its associated personnel,

constantly strive to improve the 

quality and flow of data, and to do 

so with the most efficient and up-todate means possible.

87

Information Dissemination
A-1

Appendix

Table A-1: Emissions Tests Completed on Light-Duty Vehicles as of August 1, 1995

Vehicle Model Year Model Number Number

Type of Vehicles of Tests

Chevrolet C-2500 Pickup 1992 Dedicated CNG 5 5 

1993 Standard 2 2 

Chevrolet Lumina 1991 M85 flexible-fuel 7 116 

Standard 8 25

1992 E85 flexible-fuel 13 59

1993 E85 flexible-fuel 12 42

Standard 16 23

Dodge B-250 Van 1991 Dedicated CNG 2 2

1992 Dedicated CNG 36 50

Standard 22 25 

1994 Dedicated CNG 14 14

Standard 25 35

Dodge Caravan (mini-van) 1994 Dedicated CNG 10 10

Dodge Intrepid 1995 M85 flexible-fuel 3 7

Standard 8 8

Dodge Spirit 1993 M85 flexible-fuel 76 319 

Standard 72 126 

Ford Econoline Van 1992 M85 flexible-fuel 13 53 

1993 M85 flexible-fuel 3 9

Standard 18 23

Ford Taurus 1991 M85 flexible-fuel 7 89

Standard 2 18

1994 E85 flexible-fuel 2 4

1995 E85 flexible-fuel 12 24

Standard 2 2

Total 390 1090 
A-2

Appendix

Table A-2: Summary of the Alternative Fuel Transit Buses in the Data Collection Program

Site Fuel Number of Alternative Months Total Mileage on

Fuel Buses of Data Alternative Fuel Buses

Houston LNG/diesel dual-fuel 10 17 376,000

Miami CNG 5 17 87,000

Tacoma CNG 5 14 294,000

Peoria E95/E93* 5 23 389,000

Minneapolis E95 5 9 57,000

Miami M100 5 17 193,000

New York M100 5 0 0

St. Louis B20** 5 10 184,000

Portland LNG 8 0 0

* Peoria switched from E95 to E93 in March 1994 for financial reasons. Approximately 70 percent of the above mileage 

had been accumulated when this switch was made.

** B20 is a low-level biodiesel blend that the Department of Energy does not consider to be an alternative fuel under 

the provisions of the Act.
A-3

Appendix

Table A-3: Summary of the Heavy-Duty Vehicles in the Data Collection Program

Project Fuel Engines Vocation Number of Sponsors Launched

Vehicles/Controls

Federal Express M85 Local 82/27 NREL, SCAQMD, CEC, 10/92

CleanFleet CNG delivery Federal Express, OEMs,

Propane Fuel suppliers

RFG

Trucking Research CNG Tecogen 4.3 L Local 20/5 NREL, UPS 09/94

Institute/United delivery

Parcel Service

New York City CNG Cummins L10G Garbage 6/3 NREL, NYC Department 11/92

Department of packer of Sanitation

Sanitation

Illinois Dept. of E95 DDC 6V92 Line haul 4/1 NREL, Illinois 10/92

Commerce and

Community Affairs\

Archer Daniels

Midland

Trucking Research E95 DDC 6V92 Dump truck/ 2/1 NREL, Hennepin County 10/93

Institute/Hennepin snowplow

County, Minnesota

Trucking Research E95 DDC 6V92 Dump truck/ 2/0 NREL, Nebraska 09/94

Institute/Nebraska snowplow

Trucking Research CNG DDC Series 60 City delivery 1/1 NREL, SCAQMD, SoCal, 09/94

Institute/Acurex/ Gas, CEC

LA Times

Trucking Research Biodiesel* DDC, Cummins, Line haul 6/3 NREL, Ag Products 10/94

Institute/Ag Products Mack

Trucking Research LNG DDC Series 60 Line haul 3/1 NREL, Liquid Carbonics 2/95

Institute/Liquid

Carbonics

Trucking Research LNG Cummins C83 City Tractor 2/1 NREL, Pacific Enterprises 8/95

Institute/Con-way LNG

Western Express

* Other than neat biodiesel (B100), biodiesel blends are not currently considered by the Department of Energy to be an 

alternative fuel under the provisions of the Act.
A-4

Appendix

Table A-4: Vehicles in the Heavy-Duty Program: 

Phase 0 and 1 School Bus Grants

Phase Operating State Number Fuel Vehicle

Jurisdiction Type

0 Tulsa County Oklahoma 55 CNG School buses

0 Tulsa County Oklahoma 45 CNG School buses1

0 Town of Weston Massachusetts 3 CNG School buses

0 Town of Weston Massachusetts 2 CNG School buses1

0 Wood County West Virginia 2 CNG School buses

0 Wood County West Virginia 2 CNG School buses

0 Wood County West Virginia 4 CNG School buses1

1 Maricopa County Arizona 4 CNG School buses

1 Braxton County West Virginia 3 CNG School buses

1 Montgomery County Pennsylvania 1 Methanol School bus

1 D.C. Public Schools District of Columbia 4 CNG School buses

1 Springfield School District Missouri 4 CNG School buses

1 Jordan School District Utah 4 CNG School buses

1 University of Vermont Vermont 2 CNG School buses

1 Shenendehowa School District New York 2 CNG School buses

1 Marcus Whitman School District New York 2 CNG School buses

1 Albuquerque New Mexico 4 CNG School buses

1 Franklin County Kentucky 4 CNG School buses

1 Montgomery County Maryland 32 CNG School buses

1 Baltimore County Maryland 32 CNG School buses

Total 153

1 Conversion vehicles (all others are OEM vehicles)

2 Two of the vehicles were purchased with DOE funding; one was purchased with Maryland state funds.
A-5

Appendix

Table A-5: Vehicles in the Heavy-Duty Program: 

Phase 2 School Bus and Heavy-Duty Vehicle Grants

Phase Operating State Number Fuel Vehicle Type

Jurisdiction

2 Peoria Illinois 2 E95 Snowplow/construction trucks

2 Peoria Illinois 1 E95 School bus

2 Louisville/ Kentucky 3 CNG Municipal wreckers

Jefferson County

2 Mecklenburg County North Carolina 4 CNG School buses

2 State of Nevada Nevada 2 CNG 15,000-GVW Crew Cab

dump trucks

2 State of Nevada Nevada 2 CNG Tymco street sweepers

2 New York City New York 2 CNG Athey street sweepers

2 Bethlehem School 2 CNG Transit-style buses used

District, Albany County New York in school bus operation

2 East Providence Rhode Island 4 CNG School buses

2 Richland and South Carolina 4 CNG Heavy-duty trucks

Lexington Counties

2 Richmond, Virginia 3 LPG Class 7 (28,000-33,000 GVW)

Northern Virginia, dump trucks

and Suffolk

2 Virginia Beach Virginia 1 CNG School bus

2 Pleasants County West Virginia 2 CNG Transit-style buses used 

in school bus operation

2 Washington, D.C. District of 3 CNG Jet Vac machines

Columbia

2 Washington, D.C. District of 1 CNG 38,000-GVW dump truck

Columbia

2 Waco and Washington Iowa 4 Soydiesel* School buses

Community

School Districts

Total 40

* 70 percent soydiesel/30 percent diesel blend (not currently considered by the Department of Energy to be an alternative 

fuel under the provisions of the Act).
A-6

Appendix

Table A-6: Vehicles in the Heavy-Duty Program: 

Phase 3 School Bus and Heavy-Duty Vehicle Grants

Phase Operating State Number Fuel Vehicle Type

Jurisdiction

3 Washington, D.C. District of 4 CNG Ford E350s

Columbia

3 Boston Massachusetts 4 CNG Airport shuttles

3 Long Beach California 4 CNG Refuse haulers

3 State of Maryland Maryland 7 CNG Heavy-duty vehicles

3 Kenosha Wisconsin 3 CNG Refuse haulers

3 Kenosha Wisconsin 1 CNG Street sweeper

3 Chicago Illinois 7 Diesel, LPG, Refuse haulers

Ethanol, CNG

3 Las Vegas Nevada 2 CNG Street sweepers

3 Phoenix Arizona 2 CNG Tractor trailers

3 Phoenix Arizona 2 CNG Dump trucks

3 Phoenix Arizona 2 CNG Refuse haulers

3 State of Pennsylvania Pennsylvania 1 M100 School bus

3 State of Pennsylvania Pennsylvania 1 CNG School bus

3 Austin Texas 2 LPG Refuse haulers

Total 42
A-7

Appendix

Table A-7: Vehicles in the Heavy-Duty Program: 

Phase 4 School Bus and Heavy-Duty Vehicle Grants

Phase Operating State Number Fuel Vehicle Type

Jurisdiction

4 Chicago Illinois 3 LPG Refuse haulers

4 Syracuse New York 1 Natural gas School bus

hybrid

4 Tonowanda New York 1 CNG Sewer jet vactor

4 White Plains New York 2 Ethanol Heavy-duty trucks

4 Berkeley California 4 CNG Heavy-duty trucks

4 Jordon/Alpine Schools Utah 4 CNG School buses

4 Milwaukee County Wisconsin 1 CNG 5.71 V-8 engine

4 Dane County Wisconsin 1 Propane 7.51 V-8 engine

4 Plano Texas 3 Propane 8.31 engines

4 El Paso Texas 5 Propane Heavy-duty trucks

4 Maricopa County Arizona 4 CNG School buses

4 York County S. Carolina 3 CNG School buses
U.S. Department of Energy

Office of Transportation Technologies

Office of Energy Efficiency and Renewable Energy

T OF ENERGY

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