October 2003 

DOE/GO-102002-1791 

Challenges and Experiences 

with Electric Propulsion Transit Buses 

in the United States

TECHNICAL REPORT

Leslie Eudy, National Renewable Energy Laboratory (NREL) 

Matthew Gifford, Battelle

November 2003 

DOE/GO-102003-1791 
A Strong Energy Portfolio for a Strong America

Energy efficiency and clean, renewable energy will mean a stronger economy, a cleaner 

environment, and greater energy independence for America. By investing in technology 

breakthroughs today, our nation can look forward to a more resilient economy and secure future. 

Far-reaching technology changes will be essential to America's energy future. Working with a wide array 

of state, community, industry, and university partners, the U.S. Department of Energy's Office of Energy 

Efficiency and Renewable Energy invests in a portfolio of energy technologies that will: 

• Conserve energy in the residential, commercial, industrial, government, and transportation sectors 

• Increase and diversify energy supply, with a focus on renewable domestic sources 

• Upgrade our national energy infrastructure 

• Facilitate the emergence of hydrogen technologies as vital new "energy carriers." 

The Opportunities 

Biomass Program

Using domestic, plant-derived resources to meet our fuel, power, and chemical needs 

Building Technologies Program

Homes, schools, and businesses that use less energy, cost less to operate, and ultimately, generate as 

much power as they use 

Distributed Energy & Electric Reliability Program

A more reliable energy infrastructure and reduced need for new power plants 

Federal Energy Management Program

Leading by example, saving energy and taxpayer dollars in federal facilities 

FreedomCAR & Vehicle Technologies Program

Less dependence on foreign oil, and eventual transition to an emissions-free, petroleum-free vehicle 

Geothermal Technologies Program

Tapping the Earth's energy to meet our heat and power needs 

Hydrogen, Fuel Cells & Infrastructure Technologies Program

Paving the way toward a hydrogen economy and net-zero carbon energy future 

Industrial Technologies Program

Boosting the productivity and competitiveness of U.S. industry through improvements in energy and 

environmental performance 

Solar Energy Technology Program

Utilizing the sun's natural energy to generate electricity and provide water and space heating 

Weatherization & Intergovernmental Program

Accelerating the use of today's best energy-efficient and renewable technologies in homes, communities, 

and businesses 

Wind & Hydropower Technologies Program

Harnessing America's abundant natural resources for clean power generation 

To learn more, visit www.eere.energy.gov. 
DOE/GO-102003-1791 

Challenges and Experiences 

with Electric Propulsion Transit Buses 

in the United States

TECHNICAL REPORT

Leslie Eudy, National Renewable Energy Laboratory (NREL) 

Matthew Gifford, Battelle

November 2003 
NOTICE

This report was prepared as an account of work sponsored by an agency of the United States 

government. Neither the United States government nor any agency thereof, nor any of their employees, 

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constitute or imply its endorsement, recommendation, or favoring by the United States government or any 

agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect 

those of the United States government or any agency thereof. 

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iii

Fleet Test & Evaluation Team 

The Fleet Test & Evaluation (FT&E) Team at the National Renewable Energy Laboratory (NREL) was 

formed to accomplish the objectives of current and emerging programs at the U.S. Department of Energy 

(DOE). The team consists of personnel from NREL and Battelle and supports DOE’s FreedomCAR and 

Vehicle Technologies (FCVT) and Hydrogen, Fuel Cells, and Infrastructure Technologies (HFC&IT) 

Programs. 

FT&E projects at NREL include six to nine evaluation sites/fleets over the next four years; two or three 

fleets will be evaluated in parallel. The team will collect as much as 12 months of data from each site. 

Data collected from study and control vehicles (if available) include cost, operations, and performance. 

Final reports of the results are planned for publication. Alternative fuel vehicles (including compressed or 

liquefied natural gas) will be evaluated, as will hybrid electric and fuel cell vehicles. 

The objective of DOE/NREL evaluation projects is to provide comprehensive, unbiased evaluations of 

currently available advanced technology and alternative fuel vehicles. This objective is customized for 

each evaluation site based on the vehicle technology development status and the site’s expectations. 

Operators considering the use of these vehicles constitute the primary audience for this information. 

Contacts 

NREL 

1617 Cole Boulevard 

Golden, Colorado 80401 

Leslie Eudy Ken Proc 

Senior Project Leader Project Engineer 

Telephone: (303) 275-4412 Telephone: (303) 275-4424 

Fax: (303) 275-4415 Fax: (303) 275-4415 

E-mail: leslie_eudy@nrel.gov E-mail: ken_proc@nrel.gov

Battelle 

505 King Avenue 

Columbus, Ohio 43201 

Kevin Chandler 

Principal Research Scientist 

Telephone: (614) 424-5127 

Fax: (614) 424-5069 

E-mail: chandlek@battelle.org
iv

Acknowledgments

This paper was developed with input from a focus group made up of government partners and transit 

agencies with experience using electric propulsion technologies in transit service. Contributing authors: 

U.S. Department of Energy Federal Transit Administration 

Lee Slezak Shang Hsiung 

New York City Transit Orange County Transit Authority 

Bill Parsley Jim Ortner 

Dana Lowell 

Santa Barbara Metropolitan Transit District SunLine Transit Agency 

Gary Gleason Bill Clapper 

Dallas Area Rapid Transit Santa Barbara Electric Transportation 

Rocky Rogers Institute 

Darryl Spencer Paul Griffith 

 Zail Coffman 

 

National Renewable Energy Laboratory (NREL) Battelle

Leslie Eudy Matthew Gifford 

Ken Proc Kevin Chandler 

The authors would like to thank the following people who reviewed the document and provided 

additional information. 

 Lee Grannis, Greater New Haven Clean Cities Coalition 

 BJ Kumar, Energetics 

 Jon Leonard, TIAX 
v

Table of Contents 

Introduction...................................................................................................................................................1 

Document Objective .....................................................................................................................................1 

Approach.......................................................................................................................................................1 

Steps to Success ............................................................................................................................................2 

Why Are Transit Agencies Considering Electric Propulsion Technology?..................................................3 

Electric Propulsion Technology Types.........................................................................................................4 

Status of Electric Propulsion Transit Bus Implementation...........................................................................6 

Development Path for Electric Propulsion Transit Buses.............................................................................7 

Advanced Propulsion Bus Operating Experience.........................................................................................7 

Research New Technologies ....................................................................................................................7 

Plan for Higher Costs and Added Resources............................................................................................8 

Apply a Teamwork Approach ..................................................................................................................9 

Train Maintenance and Other Staff ........................................................................................................10 

Technical Challenges ..................................................................................................................................10 

Energy Storage .......................................................................................................................................11 

Motors.....................................................................................................................................................13 

Hybrid-Specific Issues............................................................................................................................14 

Other Considerations ..............................................................................................................................14 

Conclusion ..................................................................................................................................................16 

References...................................................................................................................................................17 

Web Sites ....................................................................................................................................................19 

Appendix A: Focus Group Fleet Profiles....................................................................................................21 

New York City Transit ...........................................................................................................................21 

Orange County Transportation Authority...............................................................................................21 

Santa Barbara Metropolitan Transit District...........................................................................................22 

SunLine Transit Agency.........................................................................................................................23 

Dallas Area Rapid Transit ......................................................................................................................24 

Appendix B: Focus Group Responses to Questionnaires ...........................................................................25 

New York City Transit ...........................................................................................................................25 

Orange County Transportation Authority...............................................................................................26 

Santa Barbara Metropolitan Transit District...........................................................................................27 

SunLine Transit Agency.........................................................................................................................29 

Dallas Area Rapid Transit ......................................................................................................................30 

Federal Transit Administration (FTA)....................................................................................................31 

U.S. Department of Energy (DOE).........................................................................................................32 
1 

Introduction 

During the last decade, transit agencies have been under pressure to reduce overall fleet emissions. 

Although buses make up only 1% of the vehicles in the United States, they typically operate in the most 

populated areas where pollution is already a problem and exhaust smoke is easily noticed. Many agencies 

have switched to cleaner burning fuels, such as natural gas, but high capital costs for infrastructure have 

led some to look for other solutions. Powering buses with electric propulsion is one option. 

The U.S. Department of Energy’s (DOE) Advanced Vehicle Testing Activity (AVTA) supports the 

FreedomCAR and Vehicle Technologies Program’s efforts to facilitate the transition of advanced 

technologies from research and development to the marketplace. The National Renewable Energy 

Laboratory (NREL), which manages AVTA’s medium- and heavy-duty vehicle activities, provides 

potential buyers of advanced vehicles with the information they need to make informed decisions on 

purchasing and implementing vehicles into their fleets. These agencies need to be well informed about the 

vehicles’ operational characteristics, costs, and performance. Understanding the implementation process 

of electric propulsion technology and lessons learned by early adopters is vital to fleet success. 

Document Objective 

This document provides background for transit agencies and other fleets that are considering the use of 

electric propulsion technologies. It tells potential users what to expect and what to plan for when 

implementing vehicles with electric propulsion systems (such as dedicated electric vehicles, hybrids, and 

even fuel cells) into their fleets. This document also addresses the unique issues that electrical integration 

can pose for fleet personnel and points to the similarities between implementing electric propulsion and 

any other significant new technology. 

Technical objectives include: 

 Provide an accurate explanation of technical status of technology development 

 Provide information on what transit agencies are doing 

 Provide comments on lessons learned with current and future technologies 

 Provide perspective for what a transit agency might expect during its implementation of electric 

propulsion technology 

 

Approach 

This document was developed using the experiences of a focus group made up of professionals from 

transit agencies across the country that have experience working with electric propulsion vehicles. The 

following agencies participated in the focus group: 

 New York City Transit (NYCT) 

 Orange County Transportation Authority (OCTA) 

 Santa Barbara Metropolitan Transit District (MTD) 

 Santa Barbara Electric Transportation Institute 

 SunLine Transit Agency 

 Dallas Area Rapid Transit 
2

Also involved in the focus group are the Federal Transit Administration and DOE. 

As a part of the U.S. Department of Transportation, the Federal Transit Administration’s (FTA) mission 

is to provide leadership, technical assistance, and financial resources for safe, technologically advanced 

public transportation, which enhances citizens' mobility and accessibility, improves America’s 

communities and natural environment, and strengthens the national economy. FTA is currently 

developing a hydrogen and fuel cell bus initiative with a goal of accelerating the development of a zeroemission fuel-efficient bus. The strategic plan includes establishing partnerships with other government, 

industry, and environmental stakeholders to coordinate resources. The agency sees electric drive 

propulsion (including battery electric, hybrid 

electric, and fuel cell hybrid) as a path to 

reaching that goal. 

Like FTA, DOE is interested in fuel-efficient 

transit bus technologies. For the last 12 years, 

DOE has been evaluating alternative fuel 

vehicles to determine the potential to reduce 

the use of foreign petroleum. DOE invests 

significant time and resources to develop 

batteries, motors, controllers, and other 

electric and hybrid vehicle system components 

that will improve efficiency and reliability, 

while lowering overall vehicle costs. As a part 

of these evaluations, understanding the 

implementation process and lessons learned 

has been a key step in providing a complete 

explanation of each site’s experience with new 

propulsion and vehicle technologies. 

The evaluation team developed a 

questionnaire for focus group members to 

solicit feedback on their experience and advice 

regarding the implementation of electric 

propulsion in transit service. The group’s 

input has been compiled in this report. For 

profiles on participating transit agencies, see 

Appendix A. For questionnaire responses, see Appendix B.

Steps to Success 

According to transit agencies that participated in the focus group, research, planning, and 

teamwork are critical in the successful integration of electric propulsion technologies. Other 

steps to success include: 

 Building a Knowledge Base—Understanding the technology is the first and most important step 

in developing an advanced technology vehicle program. In addition to gathering information from 

government and other organizations familiar with transit related technologies, an agency should 

also seek advice from other transit properties with appropriate experience. 

Questionnaire 

We asked the focus group to answer a series of questions 

to tap into their experiences with electric propulsion 

transit buses. Questions included: 

 Description of the fleet, including electric 

propulsion buses 

 Reasons for implementing advanced technology 

buses 

 Overall impression of the specific technology 

used 

 Problems encountered with the technology and 

resolutions to them 

 Advice for other transit agencies investigating 

electric propulsion buses 

 Top three things that need significant work and 

investment to commercialize the technology 

Government participants were asked to provide their 

perspectives on the status of electric propulsion 

technology and the role of transit in developing this 

technology. They were also asked to offer advice to fleets 

considering these technologies.
3

 Matching the Vehicle to the Application—To ensure success, an agency must not only 

understand the different vehicle technologies but also have a firm grasp of their specific 

applications. What works well in one application might be a dismal failure in another. Don’t 

forget that climate conditions could also present challenges for electric propulsion systems. 

 Organizing a Team—Agencies with experience in electric propulsion vehicle technologies 

report excellent support from their development partners. Working closely with manufacturers, 

vehicle systems integrators, and funding partners will provide the best chance to make a project 

successful. Manufacturers should involve transit agencies early in the development process to 

ensure the bus will meet the fleet’s needs and reduce excessive modifications during the break-in 

stage. 

 Expecting Higher Costs and Planning Accordingly—Advanced technologies will require 

higher costs for purchase as well as for operations and maintenance. Plan ahead to meet these 

costs and involve upper management in the process. Look to outside organizations, such as 

federal, state, and local government partners, for potential funding sources. 

 Educating and Training Staff—Understanding the new technologies will take time and effort 

on the part of the maintenance personnel and the fleet managers. It pays to invest in training to 

overcome this high learning curve. It may be necessary to assign several staff members to 

concentrate on the new vehicles and build an expertise in the technology. Expect some difficulties 

in obtaining manuals and replacement parts.

 Determining Your Measure of Success—Define the criteria you will use to determine the 

success of your project. Goals should be realistic and reasonable for the level of technology. 

Although it’s difficult to quantify, don’t underestimate the benefits of public relations. 

Publicizing the use of advanced technologies spurs public interest that can result in increased 

ridership.

Why Are Transit Agencies Considering Electric Propulsion 

Technology? 

Transit buses are ideal applications for alternative fuel or advanced technologies because they: 

 Operate in congested areas where pollution is already a problem 

 Are centrally located and fueled 

 Are highly visible 

 Are government subsidized 

 Are professionally operated and maintained 

 Operate on a fixed route and fixed schedule 

 Have greater tolerance for added weight and volume requirements of advanced systems 

 Have less rigorous start-up and pull-out requirements 

 Offer greater public exposure to the positive benefits of advanced technologies which leads to a 

broader public knowledge and acceptance. 

The American Public Transportation Association (APTA) estimates that 11.5% of the buses in the United 

States in 2002 were using an alternate power source (see reference 1). Although most of those buses use 
4

alternative fuels, recent trends show an increase in orders of buses using electric propulsion, particularly 

hybrids. 

Why are agencies choosing these newer technologies? Air quality is a primary reason transit agencies 

are looking to advanced bus technologies. The focus group participants cited emission reductions as one 

reason they began using advanced propulsion technologies. Most of the agencies in the focus group are 

located in large cities where densely compacted businesses, traffic congestion, and often geography 

combine to cause problems with local air quality. Although SunLine Transit Agency operates in a less 

populated area, weather conditions often transfer smog from Los Angeles through the pass into the 

Coachella Valley near Palm Springs, California. This was cited as one reason SunLine chose to use clean 

bus technologies. 

Electric propulsion vehicles use electricity generation and energy storage methods to increase the overall 

operational efficiencies, while reducing emissions. Emission improvements from battery electric or fuel 

cell vehicles range from moderate reductions to a full elimination of all hazardous onboard emissions. 

Emissions reductions from hybrid vehicles can vary with the efficiency of the hybrid system. In general, 

the cleanliness of electric propulsion vehicles varies with the technology used, but all electric propulsion 

technologies have the potential to reduce emissions. 

However, the benefits of advanced technologies can expand beyond pollution reductions. Vehicle 

efficiency is another reason transit agencies are considering advanced technology buses. Both NYCT and 

OCTA cite the potential fuel efficiency gain as an important reason to consider electric propulsion. Many 

transit agencies acquire operating funds through local sales taxes. When the economy suffers, so do the 

agencies. A more efficient vehicle uses less fuel and may therefore reduce operating costs. 

Electric propulsion vehicles present some unique advantages over other advanced technologies. 

Technology trends indicate that electric propulsion may become dominant in the future. Incorporating 

electric propulsion technologies today will prepare fleets for evolving technologies tomorrow. In addition, 

the public relations benefits prompt transit agencies to explore advanced propulsion technologies. Santa 

Barbara MTD wanted to increase ridership in its area. The goal was to provide quiet, emission-free 

transportation that would attract new customers. Ridership increased dramatically after the electric buses 

were placed into service. 

Electric Propulsion Technology Types 

Electric propulsion technologies use electric power to drive a vehicle. These systems utilize components 

such as electric motors, electric energy storage devices, inverters, and electronic controllers. They differ 

significantly from conventional vehicle systems and require many specific considerations. The primary 

configurations for electric propulsion technologies are: 

Battery Electric—Battery electric vehicles are powered solely by electric power and use an electric 

motor to drive the vehicle. All their energy is stored in batteries onboard the vehicle and the batteries 

must be recharged by an external source or swapped with freshly charged batteries when depleted. Battery 

electric vehicles can take advantage of “regenerative braking,” which recharges the batteries, to recapture 

some of the energy lost during braking. Results in Santa Barbara demonstrate that more than 30% of the 

traction energy can be recovered via regenerative braking. 

Hybrid Electric—Hybrid electric vehicles typically combine an energy storage device, a power plant, 

and an electric propulsion system. Energy storage devices are most often batteries, but other possibilities 
5

include ultracapacitors and flywheels. Power plants can be internal combustion engines, diesel engines, 

gas turbines, or fuel cells. The efficiency of a hybrid system depends on a number of factors, such as the 

particular combination of subsystems, how the systems are integrated, and the control strategy employed. 

Like battery electric vehicles, hybrid vehicles can take advantage of regenerative braking. There are two 

basic strategies for hybrid propulsion: 

 Series Hybrid—In a series configuration, the power plant provides electrical power to the motor, 

which drives the wheels. There is no mechanical connection between the power plant and the 

wheels. An advantage of this configuration is being able to set the power plant to operate at its 

maximum efficiency. 

 Parallel Hybrid—This configuration has two power paths. It allows the wheels to be driven by 

the power plant, the electric motor, or both. A vehicle in this configuration has the advantage of 

higher power because the electric motor and power plant can provide power simultaneously. 

Fuel Cell—Fuel cells, which have been used to generate power in space for decades, combine hydrogen 

and oxygen in an electro-chemical process to produce electrical power with water as the only byproduct. 

Many fuel cell vehicles are in a hybrid configuration, with the fuel cell as the primary power source. Fuel 

cells for vehicle applications are in their early stages of development, yet as a clean and efficient power 

source, they have great potential. 

The Orion VII hybrid (left) uses a series hybrid system. The Allison Electric Drives bus 

 (right) uses a parallel hybrid system. 

These technologies all use electric power and drive systems for propulsion. Although conventional 

vehicles have long used electrical systems to power lights, air conditioning, and other accessory systems, 

using electricity as motive power to propel the vehicle provides challenges with which many vehicle 

maintenance personnel and fleet operators are not familiar. 

Fleet managers and maintenance personnel will need to make significant adjustments to their operations 

to incorporate electric propulsion technologies. The adjustments will have the same types of impacts that 

implementing alternative fuel vehicles have had for transit agencies across the country. Adjustments to 

fueling practices, preventive maintenance inspections, incorporation of specialized equipment, scheduled 

regular maintenance, and training will be necessary to move forward with the advancements in vehicle 

technologies. 
Status of Electric Propulsion Transit Bus Implementation 

Battery Electrics—The history of electric vehicles in public 

transit dates back to the turn of the 20th century with the first 

demonstrations of trolleybuses connected to overhead power 

lines in Massachusetts and Pennsylvania (see reference 2). 

Today, a few U.S. cities still operate trolleybuses, but most 

dedicated electric buses are battery powered. Battery electric

buses are limited in size and application because of restricted 

range, although improved technologies are now being fielded.

Batteries must be recharged (or replaced with recharged 

batteries) for extended operation. Most 22-foot battery electric 

buses in the United States are used in niche market applications. 

This battery electric bus, manufactured by

Ebus, operates in New Haven Connecticut.

Diesel Hybrids—Although battery electric buses have been 

limited to smaller vehicles, hybrid propulsion systems are being

developed in a wide range of vehicle sizes, including shuttle 

buses, 40-foot transit buses, 60-foot articulated buses, and overthe-road coaches. More than 30 organizations in the United 

States are currently demonstrating hybrid bus technologies. E

hybrid bus demonstration projects involved small numbers of 

vehicles, but interest has grown recently. The promising resu

from early projects have led several agencies to place large 

orders for hybrid buses. More than 600 hybrid buses could be 

placed into service around the country during the next few yea

arly

lts 

rs.

urbine Hybrids—Another type of hybrid electric, turbine 

variety

rid

uel Cell—The newest technology being developed for bus 

nd

tes

in 

technology. 

A diesel hybrid electric trolley bus by 

Trolley Enterprises. 

T

This turbine hybrid bus, operated in Coconut 

hybrids use a small turbine and generator set to produce 

electricity to power the bus. The turbine can operate on a

of fuels, including natural gas, propane, biodiesel, and diesel. In

a typical 30-kW configuration, the turbine supplies enough

power to operate a small (commonly a 22-foot) bus in a hyb

application. The largest order to date for turbine hybrids is 20 

buses, which are still in production (see reference 3). A larger,

60-kW turbine generator set is now commercially available for 

packaging in larger 40-foot hybrid bus 

applications. Creek, Florida, is fueled by propane. 

F

The prototype fuel cell hybrid bus from ISE 

propulsion uses fuel cells for power. Many of these vehicles 

have electric propulsion systems with a supplemental power a

energy storage device, such as a battery. Although many fuel cell

bus projects are being conducted throughout the world, these 

vehicles are still in the early prototype stage. In the United Sta

and Canada, 14 fuel cell buses have been demonstrated in 

various cities; 11 more are expected to begin revenue service 

2004. However, much work must still be done to lower costs and

improve reliability and durability enough to commercialize this

Research uses a fuel cell by UTC.

6
7

Development Path for Electric Propulsion Transit Buses 

Developing new transit bus technologies can be very costly for vehicle manufacturers. Advanced 

propulsion technologies require significant investments simply to develop prototypes. Because of the 

limited market for buses, the transit industry cannot expect the same level of manufacturer-led product 

development as occurs in the consumer auto industry. According to APTA, the most buses built by a 

single original equipment manufacturer in 2001 were 1,548 (see reference 4). By comparison, General 

Motors produced more than 5.5 million light-duty vehicles in that same year, including more than 

700,000 of the most popular vehicle model (see reference 5). 

The difference in sales volumes limits bus manufacturers from allocating the level of resources that auto 

manufacturers allocate for research and development of these new technologies. As a result, new bus 

technologies are typically developed using venture capital, often by small niche companies. In addition, 

buses are often built to each agency’s specification as opposed to building standard models that are 

available to all customers. These factors make extensive on-road testing unaffordable. Manufacturers 

must instead rely on transit fleets that are willing to operate vehicles as they progress from prototypes to 

full commercial models. 

Order size also causes difficulties in the development process. Smaller orders give transit agencies a 

chance to work out the bugs in new technologies before they comprise a critical portion of their fleet. 

However, manufacturers are likely to have difficulty supporting small fleets when technical problems 

occur. Larger orders allow for lower capital costs but could be a problem for smaller agencies if a major 

issue arises in the fleet. The operator may not have enough spare buses to cover potential service 

interruptions. Smaller bus manufacturers can also be hard pressed to deliver a large order of new 

technology buses. Even one failing product could drive a small company out of business, and leave the 

transit agency with little or no support. 

Advanced Propulsion Bus Operating Experience 

The experiences of our focus group are valuable resources for other agencies considering electric 

propulsion buses. Knowing the successes and challenges experienced by early adopters can help other 

organizations avoid potential pitfalls and help advance the technology to the next step. The group’s advice 

is broken into four categories: 

 

 Research New Technologies 

 Plan for Higher Costs and Added Resources 

 Apply a Teamwork Approach 

 Train Maintenance and Other Staff 

Research New Technologies 

Educating staff on the different technologies is one of the most important things a transit agency can do to 

ensure the success of an advanced propulsion technology bus program. This knowledge should be 

acquired before making a decision about which technology to use. There are a variety of new 

technologies being developed; a thorough understanding of the advantages and disadvantages of each is 

needed to make the best choice. An agency must also understand the specific application and the duty 

cycle on which the buses will operate. Matching the vehicle to the application is key to a successful 
8

implementation. For example, a battery electric bus has a limited range and must therefore be placed in 

appropriate duty cycles by the transit agencies. 

Resources on electric propulsion vehicles can be found in a number of places. The Internet provides 

information on electric propulsion vehicles. DOE’s Alternative Fuels Data Center (www.afdc.doe.gov) 

includes a wide variety of information on all types of alternative fuels and propulsion systems for lightand heavy-duty vehicle applications. The Transportation Research Board has published several reports on 

transit related issues, which can be ordered through the Web. Information is also available through 

organizations such as the Electric Drive Transportation Association (EDTA) and the APTA. These and 

other Web sites are convenient starting places for researching electric propulsion vehicles. (See 

References for Web site addresses.) 

Seeking the experiences of other transit agencies is also a helpful way to prepare for a vehicle 

demonstration. Many agencies are eager to share their knowledge with the industry. There are several 

organizations that bring interested parties together to trade their experiences. APTA’s Electric Bus 

Subcommittee meets twice yearly, typically in conjunction with events where transit professionals are 

already in attendance. The APTA Bus and Paratransit Conference held each year in early May is one of 

these events. The group includes members from transit agencies, bus manufacturers, fuel providers, and 

government agencies—all of which have interest in or experience with electric propulsion technologies. 

Another organization that brings transit professionals together to share information on advanced vehicles 

is the Electric Power Research Institute (EPRI). EPRI and EDTA have sponsored several electric bus 

workshops in the past few years where users and manufacturers where brought together to discuss 

available products as well as current issues with new technologies and the solutions to those problems. 

Plan for Higher Costs and Added Resources 

Transit agencies that plan to implement electric propulsion technologies should expect to incur 

significantly higher costs until these technologies achieve commercial maturity. Not only will the vehicles 

and other equipment cost more to purchase but standard maintenance tasks will take longer while 

personnel become familiar with the new technology. Transit agencies should take the time to fully 

investigate the potential costs involved before making a commitment to operate advanced technology 

vehicles. Planning up front can reduce the potential of surprises during a demonstration. 

Of course, the newer technologies are more expensive to purchase than conventional diesel buses. Table 1 

shows the typical costs associated with various transit bus technologies. The relative price difference is 

indicative of the comparative commercial maturity of these technologies. For many cash-strapped 

agencies, these costs may be prohibitive. An agency needs to plan for these costs early in the project 

development phase. Demonstrations of advanced technologies are often heavily subsidized by 

government agencies such as the Federal Transit Administration, which provides 80% of the capital cost 

of advanced technology buses. Other grants may be available from DOE, the U.S. Department of 

Transportation, as well as government agencies at the state and local level. However, even with 

government aid, fleets can encounter difficulty funding the incremental cost of vehicles, upgrades, 

equipment, training, and other costs for advanced technology vehicle projects. 

Transit agencies should also plan for potential added costs to upgrade maintenance facilities. For battery 

electric and hybrid buses, this could include lift equipment for trading out battery packs, battery 

charging/conditioning units, and safety equipment necessary for working with electric systems. Buses that 

operate on alternative fuels, such as compressed natural gas, will also require new fueling infrastructure to 

be added, as well as garage modifications to allow for safe maintenance practices. 
9

Table 1. Capital Costs For Transit Buses 

Technology Approximate Cost 

Standard 40-foot Diesel Bus $280-290K 

CNG Bus (40-foot) $300-320K 

Hybrid Bus (40-foot) $390-450K 

Hybrid Shuttle Bus (22-foot) $260-350K 

Battery Electric Shuttle Bus (22-foot) $180-230K 

Fuel Cell Bus $3 million 

In addition to the up-front costs of the buses, transit 

agencies must plan for additional resources to 

support the project. It is easy to underestimate the 

time required for project staff, from maintenance 

workers to project managers. Agencies can take 

several paths to meeting staffing resources. Some 

agencies treat the advanced technology no different 

from the conventional buses—training all 

maintenance workers to handle the vehicles. Other 

agencies find it helpful to assign specific staff to the 

new buses, developing several experts in the 

technology. 

Apply a Teamwork Approach 

Transit agencies considering electric propulsion buses should begin by building a team. While diesel bus 

technology is mature, electric propulsion buses are in an infancy stage. Organizations that have no 

significant experience with technologies other than diesel should be aware that there is often a gap 

between what they expect and the reality of the new technology bus. Forming a partnership between 

operator, manufacturer, and system integrator will help ensure success. Other potential team members 

include component suppliers, infrastructure developers (for vehicles operating on fuels other than diesel), 

and funding agencies. Experienced transit agencies suggest dealing with well-established organizations 

that will put up their own money to develop the product, are committed to commercializing the 

technology, and will support the product when problems arise. Transit agencies implementing electric 

propulsion vehicles should be wary of companies that are only interested in being paid for development 

work. 

The transit agency should be involved/partnered in the design, development, and construction stages of 

the bus. Vehicles built from the ground up, as opposed to retrofitted vehicles, generally perform better. A 

custom designed vehicle is often more robust than a converted vehicle. An agency can achieve a better 

match between vehicle and application when they are involved in this process. This can have a significant 

impact on the number of road calls and vehicle downtime. 

Once the first bus is delivered, the cooperation between bus manufacturer and transit agency becomes 

even more critical. Cooperation allows manufacturers to learn how their products need improvement and 

helps the fleet learn how the advanced systems work and how they affect operations. Transit agencies 

should understand that modifications might be necessary during the early stage of deployment. The 

operator’s support to the manufacturer during this time is important to help push the development of the 

technology. In a sense, the transit agency becomes its own researcher to support the manufacturer and 

integrator of the technology. The most successful agencies assign a person or team to become experts in 

The hybrid buses used on Denver’s 16th

Street Mall are fueled by CNG. 
10

the selected technology. This team can dedicate their time to study the system and work through problems 

to keep the buses operating. Resolution of problem may not be obvious and could take significant effort 

to resolve. Having personnel dedicated to the project is a key to success. 

Train Maintenance and Other Staff 

Because of the many issues and barriers associated with the transit bus development process, fleet 

managers should expect problems and setbacks when implementing new vehicle technologies. The first 

thing for fleet managers to understand when demonstrating new vehicle technologies is that their vehicles 

are not fully developed commercial products. Most electric propulsion vehicles that incorporate new 

technologies are in an early stage of development and are more likely to need greater attention from 

maintenance personnel than other vehicles. This is because electric propulsion systems incorporate new 

technologies that are unfamiliar to maintenance staff. Understand that there will be a longer “shakedown” 

period than with a conventional bus. It will take time for maintenance personnel to become familiar with 

troubleshooting and repairing new bus systems. However, the objective of this learning process is to help 

transit agencies to quickly reach the point where they can meet their maintenance needs without outside 

assistance. 

For transit agencies that maintain vehicles in-house, training is extremely important for their maintenance 

personnel. The new systems will be very different from the typical diesel systems. It will take time and 

money to provide the training necessary to get the maintenance staff up to speed. Even after the training 

has been performed, troubleshooting advanced systems will be more difficult until personnel become 

more familiar with the systems through experience. Each vehicle may develop its own unique set of 

integration problems. There is potential for a long learning curve with new technologies, but proper 

training and planning can help a technology demonstration succeed. 

Additional considerations should be made for transit agencies that have unionized maintenance depots. 

Depending on how the union is organized, there could be issues with maintaining systems that are not 

typical. For example, some maintenance shops have workers that specialize in specific systems, such as 

electrical or mechanical. An advanced technology bus has systems that may overlap specific job 

descriptions. Deciding who will maintain these systems could become an issue. Educating union 

representatives about the differences in the new technology buses could go a long way to avoid confusion 

when the first bus requires maintenance. 

Technical Challenges 

When implementing any new vehicle technology, there are likely to be challenges and setbacks. The 

impact of these events can be minimized by developing a thorough understanding of the technologies 

being operated. Many components in electric propulsion vehicles may present new challenges to 

maintenance staff. A basic understanding of the most common difficulties associated with electric 

propulsion vehicles will help prepare transit agencies that intend to demonstrate these technologies. 

Current electric propulsion systems typically lack the robustness that transit agencies expect from their 

vehicles. The components may be more sensitive to the environmental conditions of heavy vehicle 

operations, such as large swings in temperature and exposure to moisture. Some fleets have experienced 

intermittent electrical problems that can’t be traced to a defect in the design or components. 

Transit operators should not accept defective bus products. However, it is important to recognize that 

while the diesel-bus product is mature and well established, the electric-bus industry is still in its infancy. 
11

The operator should proceed with an electric propulsion bus procurement only with the clear 

understanding that there may well be a longer shakedown period than experienced with diesel-bus orders. 

Despite such uncertainties, experience has demonstrated that the benefits that accrue with the successful 

acquisition and implementation of an electric-drive bus program far outweigh the potential disadvantages. 

The following sections describe typical components in an electric propulsion system and some of the 

technical challenges the focus group encountered.

Energy Storage 

Batteries are the most common devices used for energy storage in advanced technology vehicles. The 

performance requirements needed for a battery depend on the specific application. The key performance 

variables for batteries are: 

 Specific Energy—The ratio of energy output of a battery to its weight, expressed in watt hours 

per kilogram (Wh/kg). 

 Specific Power—The ratio of power delivered by a battery to its weight, expressed in watts per 

kilogram (W/kg). 

 Cycle Life—The number of cycles under specific conditions that a battery can experience before 

failure. 

These factors indicate how long the battery can be expected to last and how much battery weight will be 

required to obtain a given amount of energy storage and power. These factors are important when 

selecting a battery for an advanced vehicle. For example, a battery electric vehicle needs high specific 

energy to provide sufficient vehicle range and high specific power for acceleration. In a hybrid electric 

configuration, the battery needs high specific power for acceleration and the capability to accept high 

power repetitive charges from regenerative braking. 

The cycle life of a battery is affected by the way they are utilized in a particular configuration. Battery 

electric vehicles typically use batteries in a deep discharge mode, which means the vehicle is operated 

until the batteries are discharged to a certain level then fully recharged. Batteries in a hybrid system, 

however, are operated in shallow charge/discharge cycles. Batteries have been described as the “Achilles 

heel” for electric propulsion because few developers have yet produced a system that meets vehicle needs 

cost effectively. The most understood battery types tend to be heavy and don’t have the cycle life of 

newer battery technologies. There are several types of batteries—all of which have implications for 

vehicle performance and reliability. 

The energy storage system used for electric propulsion applications will have a significant impact on the 

vehicle’s performance. Experienced transit agencies suggest considering the system’s reliability, costeffectiveness, and ability to maximize the energy recovered from regenerative braking when choosing an 

energy storage system. Another important factor to consider is the need for battery management, both 

thermally and electrically. A battery system can vary in temperature from module to module, which can 

cause an unbalance in the pack and reduce performance. Regulating temperature range and uniformity in 

the battery pack can affect the performance, charge acceptance (regenerative braking), and overall 

maintenance expenses (see reference 7). Current ambient temperature systems do not always include 

battery thermal management. Adding a management system could optimize performance, reduce 

maintenance costs, and increase the life of the battery pack, reducing the overall cost. Transit agencies 

looking into electric propulsion buses should investigate this option. 
12

Energy storage options include (see reference 8): 

Valve-Regulated Lead Acid (VRLA)—Unlike conventional batteries, VRLA batteries contain a limited 

amount of electrolyte that is either absorbed in a separator or in a gel. Lead acid batteries have been the 

most common rechargeable electrochemical storage system for longer than a century. This seems 

surprising because the amount of energy it can store is relatively modest because of the heavy weight of 

the reacting substances. Typical batteries have a specific energy of 35 Wh/kg, with a life of up to 800 

cycles. While they are low in energy, VRLA batteries have a high specific power of around 200 W/kg. 

They are, however, adversely affected by lower temperatures. VRLA batteries have been used in vehicles 

since 1978 and are the most common technology used in vehicle applications. Commercial availability of 

these batteries makes them a lower cost option. They are low in range but high in power. 

 

Nickel-Metal-Hydride (NiMH)—Utilizing the same technology pioneered in laptop computers and 

cellular phones during the past decade, NiMH batteries can be used effectively onboard electric 

propulsion vehicles. Although more costly than lead acid, NiMH batteries are used in most light-duty 

vehicle applications and are beginning to show up in heavy-duty hybrids. The specific energy of NiMH 

batteries varies depending on the application. For battery electric vehicles the specific energy ranges from 

65 to 75 Wh/kg, while in a hybrid configuration it ranges from 45 to 60 Wh/kg. 

Nickel Cadmium (NiCd)—The vented sintered-plate NiCd battery (sometimes called “flooded NiCd”) is 

mechanically rugged and long-lived. It has excellent low-temperature characteristics and can be 

hermetically sealed. The initial cost is higher than lead-acid batteries, but the total life-cycle cost is 

somewhat lower. NiCd batteries are fast charging and have a long life span. NiCd batteries can suffer 

from a “memory effect” when exposed to charging followed by repetitive shallow discharge cycles. This 

effect, which causes a gradual decrease in power and capacity, is completely reversible by reconditioning 

the batteries. Disadvantages of this battery chemistry are the lower energy density and the presence of 

cadmium, which is a toxic substance. A NiCd battery system utilizing a liquid-cooling system is presently 

being used on a hybrid bus. 

Sodium Nickel Chloride (NaNiCl)—This battery technology is reaching new levels of capacity, 

performance, safety, and cost-effectiveness. It has a high specific energy (around 115 Wh/kg) and a long 

cycle life (2,500 cycles). NaNiCl modules do not require topping-up, agitation, or direct battery cooling, 

reducing the need for costly ancillary equipment. It is a high temperature system, operating in the range of 

250°C–350°C. Because the batteries operate under controlled temperatures in a sealed steel box, they are 

Water cooled thermal management system on a 

battery electric bus. 

A battery management system could

help prevent failure of individual 

batteries in a pack. 
13

not affected by outside temperature. This battery has lately been the technology of choice in Europe for 

electric-drive buses. 

Lithium Ion (Li-ion) —In these batteries, lithium ions are exchanged between the positive and negative 

materials during the battery cycle. The positive electrode is comprised of a metal oxide, typically lithium 

cobalt oxide or lithium manganese oxide. The market for Li-ion batteries has grown over the last decade, 

mainly in portable electronics applications. These batteries offer a high specific energy (more than 150 

Wh/kg), high cycle life (more than 1,000 cycles), and operate in a wide temperature range. Because Liion batteries degrade when discharged below a certain level and lose capacity when overheated, they 

benefit from a management system to control temperature and charge level. 

Lithium-Metal Polymer—These batteries have been in development for several years and are currently 

approaching a specific energy of 150 Wh/kg and a specific power of 1,200 W/kg. Current prototype 

lithium polymer batteries have a cycle life approaching 10 years, which meets the FreedomCAR 2008 life 

cycle goal for a dual-assist hybrid. 

Table 2. Comparisons of Battery Characteristics (See Reference 8) 

Technology Configuration

Specific 

Energy 

(Wh/kg) 

Specific 

Power 

(W/kg) 

Cycle 

Life 

Lead Acid Cell 35 200 800 

Nickel Metal Hydride Cell 45-75 850 900 

Nickel Cadmium Cell 30 260 1,000 

Sodium Nickel Chloride Cell 

Battery 

115 

95 

260 

170 

2,500 

1,000 

Lithium Ion Battery 100-158 700-1,300 >1,000 

Motors 

Electric motors offer several advantages over engines for vehicle propulsion. Unlike engines, motors 

provide their highest torque at low speeds. This provides for exceptional acceleration from a stop and 

prevents the need to idle. Motors also offer the advantages of low noise and high efficiency. Motors 

generally require much less maintenance than engines. In addition, electric motors can facilitate 

regenerative braking by reversing field when the vehicle decelerates, thus becoming electricity generators 

that recharge battery packs. 

 

Lead acid battery pack in a hybrid bus. 
14

High Voltage and Current—Electric propulsion systems involve electronic circuits that deliver 

relatively high voltages and currents. To prevent harmful or potentially fatal electric shock, maintenance 

personnel will need to be trained to safely work with electric propulsion systems. Special protective 

equipment (including diagnostic tools) is required to work with such systems. The vehicle developers 

must train maintenance personnel to safely maintain their vehicles and suggest appropriate equipment. 

Electric propulsion vehicles require special wiring and harnesses capable of handling these high voltages 

and currents. Components should be designed for the vibration levels and environmental conditions 

associated with transit bus operations.

Hybrid-Specific Issues 

Engine Issues—Hybrid vehicles are unique because they involve a power generation system in addition 

to the electrical propulsion system. Diesel engines are often used in this application, although gas turbines 

and natural gas engines are also feasible alternatives. Current diesel engines and aftertreatment systems 

are not always sized well for hybrid applications. Improvements in efficiency and emissions could be 

achieved through diesel systems specifically designed for these applications. 

Certification of Hybrids—There is an issue with the current certification process for hybrid buses. The 

certification process for heavy-duty vehicles requires the engine to be certified on an engine 

dynamometer—separate from the vehicle. This process doesn’t take into account the emissions benefit of 

hybrid vehicles. Fleets want to get credit for the lower emissions to help meet regulations and justify the 

extra cost of hybrids. The FTA is leading a Working Group composed of industry, the U.S. 

Environmental Protection Agency, and the California Air Resources Board to find a way to credit fleets 

with lower emissions, while making sure the environmental benefits are realized throughout the life of the 

vehicle. 

Energy Storage Issues—Although battery systems on current hybrid vehicles do not need to be 

recharged from the electricity grid, sometimes a conditioning of the battery packs is necessary to balance 

the modules and increase battery life. Equipment for this conditioning adds cost to the project and must be 

maintained. Transit agencies will also need to establish procedures for this conditioning and work them 

into their standard practices.

Other Considerations 

Agency-Wide Support—It is critical for advanced technology vehicles to be supported at all levels of an 

organization. Transit agencies should have the support of senior management, who should understand that 

new technology, in addition to incremental cost, brings a risk of experiencing difficulties or even failure. 

In addition, drivers and maintenance personnel should understand the reasons for the implementation and 

the role they must fill for it to be successful. 

Developing In-House Expertise—Fleet operators could encounter complications because most electric 

propulsion vehicles cannot be considered fully commercial products. Agencies may not receive manuals 

for some of the newest technologies when the vehicles arrive. It is also likely that there will be limited 

parts availability for advanced technology components. Fleets may also have trouble obtaining the 

technical support they need as they implement advanced vehicles. To deal with these potential setbacks, 

agencies should draw on as many technical resources as possible and develop their own experts in the 

equipment they operate. Some transit agencies even suggested hiring an electrical engineer experienced 

with the implemented technology to work within the transit system. Transit agencies should also learn 
15

from outside resources, especially other transit agencies, before deciding to implement advanced 

technology vehicles and continue to learn and train after implementation. 

Warranty and Liability Issues—Transit agencies should pay careful attention to warranty and liability 

issues and should clearly understand which components are covered under the vehicle warranty and how 

warranty service will be performed. Additionally, transit agencies could have trouble insuring advanced 

technology demonstration vehicles they don’t own. 

This was true for one of the fuel cell buses demonstrated at SunLine. Because SunLine didn’t actually 

own the prototype bus, the insurance agency was hesitant to provide coverage. To reassure the insurance 

company, SunLine operated the prototype bus in simulated service, shadowing another bus on route for 

several weeks to create a record of safe and reliable operation. The demonstration bus passed the test and 

was put into service two weeks ahead of the insurance company’s original schedule. 

Maintenance Challenges—Fleets should also be aware of the significant operational impacts associated 

with maintaining advanced technology vehicles. Training will be necessary to prepare maintenance 

personnel to work with the advanced technologies. Additional maintenance equipment may also be 

needed to maintain the unique components onboard advanced technology vehicles. It may be difficult to 

identify failed components in an electric propulsion system, which hinders the troubleshooting process. It 

is important to train and prepare for maintenance difficulties, but transit agencies can still expect 

maintenance delays and challenges. 

Certain maintenance practices can help transit agencies implement advanced technology vehicles more 

smoothly. Agencies will benefit from careful documentation of the maintenance issues they encounter. 

This documentation can be used to diagnose future problems and facilitate solutions. Keeping hard-toprocure parts on hand will minimize downtime should a failure occur. The most significant impacts on 

operation are likely to occur in the first few months of operation while staff becomes familiar with the 

vehicles and their components. 

Transit agencies shouldn’t jeopardize their ability to provide service if a vehicle breaks down. They 

should plan enough spare vehicles to avoid service interruptions during this development phase. After the 

first few months of operations, difficulties may still occur, but the staff will be better equipped to handle 

breakdowns quickly. 

Characterize the Benefits of Electric Propulsion Technology—Assigning value to certain benefits of 

the technology can be very difficult. One benefit is emission reduction. Battery electric and hydrogen fuel 

cell buses emit zero tailpipe emissions, and tests of hybrid buses show major emission reductions 

compared to conventional diesel buses (see reference 15). This may be an easy selling point in crowded 

cities where pollution is a major concern, but how do you justify the benefit for rural areas? Recent 

studies investigated the health effects from diesel exhaust, which includes increased hospital admission 

rates for respiratory ailments such as asthma and bronchitis. Electric propulsion buses have the potential 

to reduce pollution by not only lowering tailpipe emissions, but by encouraging the use of public 

transportation. This, in turn, will reduce the total number of vehicles on the road. 

Another benefit that is hard to characterize is increased public relations. Many transit agencies report 

increased ridership for clean technology buses. Publicizing the new technology and tracking increased use 

could help an agency justify the added capital cost. 
16

Conclusion 

Early experiences indicate that electric propulsion technologies will provide low-emission transportation 

with high fuel economy. Yet these vehicles (for the most part) are not fully commercial products. Bus 

manufacturers rely on transit agencies to conduct on-road testing of new technologies. Agencies that 

participate in these early operations should work with their partners to further develop the technologies. 

All the agencies in our focus group are excited about the potential for increased efficiency, high 

performance, and lower emissions that electric propulsion offers. They acknowledge that there is a high 

risk associated with being an early adopter of new technologies, but they are willing to invest the time and 

effort to help push the technologies to the next stage. Sharing their collective experiences will help other 

transit agencies plan for their own implementation of advanced technology buses. 
17

References 

1. 2003Public Transportation Fact Book, American Public Transportation Association, Washington, 

DC, 2002. 

2. Wyatt, D.A., All Time List of North American Trolleybus Systems, 2000, 

http://home.cc.umanitoba.ca/~wyatt/etb-systems.html. 

3. Chandler, K. and Proc, K., Advanced Technology Vehicles in Service, LNG Turbine Hybrid 

Electric Buses, NREL/FS-540-31594, National Renewable Energy Laboratory, Golden, CO, 

2002. 

4. Table 81 New Bus and Trolleybus Market by Manufacturer 2001-2006, American Public 

Transportation Association, www.apta.com/research/stats/bus/busmktmanuf.cfm. 

5. 2003 Market Data Book, Automotive News, Crain Communications Inc., 2003. 

6. Pesaran, A., Keyser, M., Thermal Characteristics of Selected EV and HEV Batteries, 16th Annual 

Battery Conference: Advances and Applications, Long Beach, CA January 9-12, 2001. 

7. Linden, D., Reddy, T., Handbook of Batteries, Third Edition, McGraw-Hill, 2002. 

8. Chandler, K., Walkowicz, K., Eudy, L., NYCT Diesel Hybrid-Electric Buses, Final Results, 

NREL/BR-540-32427, National Renewable Energy Laboratory, Golden, CO, 2002. 

9. Chandler, K., NYCT’s Diesel Hybrid-Electric Buses, Final Data Report, Battelle, Columbus, OH. 

2000. 

10. Chandler, K., Walkowicz, K., Eudy, L., NYCT’s Diesel Hybrid-Electric Buses, Program Status 

Update, NREL/BR-540-31668, National Renewable Energy Laboratory, Golden, CO, 2002. 

11. Chandler, K., Eudy, L., Advanced Technology Vehicles in Service, Diesel Hybrid Electric Buses, 

NREL/FS-540-30736, National Renewable Energy Laboratory, Golden, CO, 2001. 

12. Emissions Evaluation of Orion VII Hybrid Bus with BAE Systems Controls HybriDriveTM

Propulsion System, 01-12, Environment Canada, Ottawa, Ontario, 2001. 

13. Lanni, T., Chatterjee, S., Conway, R., Windawi, H., Rosenblatt, D., Bush, C., Lowell, D., Evans, 

J., McLean, R., Performance and Durability Evaluation of Continuously Regenerating 

Particulate Filters on Diesel Powered Urban Buses at NY City Transit, 2001-01-0511, SAE 

International, Warrendale, PA, 2001. 

14. Clark, N., Wenwei, X., Gautam, M., Lyons, D., Norton, P., Balon, T., Hybrid Diesel-Electric 

Heavy Duty Bus Emissions: Benefits of Regeneration and Need for State of Charge Correction, 

2000-01-2955, SAE International, Warrandale, PA, 2000. 

15. Northeast Advanced Vehicle Consortium, Hybrid-Electric Drive Heavy-Duty Vehicle Testing 

Project, Final Emissions Report, Northeast Advanced Vehicle Consortium, Boston, MA, 2000.
18

16. Evaluation of Engine RPM on the Emissions from the Low Floor Diesel-Electric Hybrid Bus, 97-

26771-3, Environment Canada, Ottawa, Ontario, ERMD, 1998. 

17. Eudy, L., 2002, Natural Gas in Transit Fleets: A Review of the Transit Experience, NREL/TP540-31479, National Renewable Energy Laboratory, Golden, CO, 2002. 

18. Chandler, K., Norton, P., Clark, N., DART’s LNG Bus Fleet, Final Results, NREL/BR-540-

28739, National Renewable Energy Laboratory, Golden, CO, 2000. 

19. Chandler, K., Waste Management’s LNG Truck Fleet, Final Data Report, Battelle, Columbus, 

OH, 2000. 

20. Chandler, K., DART’s LNG Bus Fleet, Final Data Report, Battelle, Columbus, OH, 2000. 

21. Chandler, K., Norton, P., DART’s LNG Bus Fleet, Start-Up Experience, NREL/BR-540-28124, 

National Renewable Energy Laboratory, Golden, CO, 2000. 

22. Chandler, K., Technical Assessment of Advanced Transit Bus Propulsion Systems, DART, Dallas, 

TX, 2002. Posted with permission: www.nrel.gov/docs/gen/fy02/NN0127.pdf. 

23. Chandler, K., Norton, P., Clark, N., Update from the NREL Alternative Fuel Transit Bus 

Evaluation Program, American Public Transit Association, 1999 Bus Conference, Cleveland, 

OH, 1999. 

24. Clark, N., Lyons, D., Rapp, L., Gautam, M., Wang, W., Norton, P., White, C., Chandler, K., 

Emissions from Trucks and Buses Powered by Cummins L-10 Natural Gas Engines, 981393, SAE 

International, Warrendale, PA, 1998. 

25. Clark, N., Gautam, M., Lyons, D., Bata, R., Wang, W., Norton, P., Chandler, K., Natural Gas 

and Diesel Transit Bus Emissions: Review and Recent Data, 973203, SAE International, 

Warrendale, PA, 1997. 

26. Chandler, K., Alternative Fuel Transit Buses, The Pierce Transit Success Story, NREL/SP-425-

21606, National Renewable Energy Laboratory, Golden, CO, 1996. 

27. Chandler, K., Malcosky, N., Motta, R., Norton, P., Kelly, K., Schumacher, L., Lyons, D., 

Alternative Fuel Transit Bus Evaluation Program Results, 961082, SAE International, 

Warrendale, PA, 1996. 

28. Motta, R., Norton, P., Kelly, K., Chandler, K., Schumacher, L., Clark, N., Alternative Fuel 

Transit Buses, Final Results from the National Renewable Energy Laboratory Vehicle Evaluation 

Program, NREL/TP-425-20513, NREL, Golden, CO, 1996.

29. Chandler, K., Malcosky, N., Motta, R., Kelly, K., Norton, P., Schumacher, L., Final 

Alternative Fuel Transit Bus Evaluation Results, Battelle, Columbus, OH, 1996. 

30. Design Guidelines for Bus Transit Systems Using Electric and Hybrid Electric 

Propulsion as an Alternative Fuel, DOT-FTA-MA-26-7071-03-1, Federal Transit 

Administration, Washington DC, 2003. 
19

Web Sites 

Focus Group Participants 

New York City Transit http://www.mta.nyc.ny.us/nyct/

Orange County Transportation Authority http://www.octa.net/

Santa Barbara Metropolitan Transit District http://sbmtd.gov/

SunLine Transit Agency http://www.sunline.org/

Santa Barbara Electric Transportation Institute http://www.sbeti.com/

Dallas Area Rapid Transit http://www.dart.org/

Federal Transit Administration http://www.fta.dot.gov/

DOE's Advanced Vehicle Testing Activity http://www.ott.doe.gov/otu/field_ops.html

Other Information Resources 

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

APTA Committees http://www.apta.com/about/committees/index.cfm

Electric Drive Transportation Association http://www.evaa.org/

Georgetown University Fuel Cell Bus Program http://fuelcellbus.georgetown.edu/

Transportation Research Board http://www.trb.org/

Manufacturers or Systems Integrators of Electric Propulsion Technologies 

Allison Electric Drives http://www.allisontransmission.com/product/electricdrive/index.jsp

BAE Systems Controls http://www.hybridrive.com/PowerSystems.htm

Ebus http://www.ebus.com/ebus.htm

ISE Research http://www.isecorp.com/

Trolley Enterprises http://www.trolleyenterprises.com/
20
21

Appendix A: Focus Group Fleet Profiles 

New York City Transit 

New York City Metropolitan Transportation Authority 

(MTA), which includes New York City Transit’s (NYCT) 

Department of Buses, is the largest transportation system 

in the United States. Nearly 7.8 million passengers are 

transported daily by bus and rail. NYCT has 235 bus 

routes in the five boroughs, totaling 1,871 miles. Buses 

run up to 24 hours a day, seven days a week, and transport 

about 2.2 million people per day. 

The MTA is committed to its Clean Fuel Bus program, 

which includes the purchase of compressed natural gas 

(CNG) and hybrid electric buses as well as use of ultra-low 

sulfur diesel fuel and catalyzed particulate filters on the diesel buses. 

Table 1 outlines NYCT’s bus fleet. 

Table 1. NYCT Bus Fleet 

Type Current 

Number 

Diesel Buses 

(40-foot, articulated, and coach) 4,227 

Diesel Hybrid Electric Buses 10 

CNG Buses 229 

Total Bus Fleet 4,466 

NYCT was invited to participate in this project because of its experience with hybrid buses, which began 

with the demonstration of a prototype bus in 1998. The success of the demonstration led to the purchase 

of 10 Orion VI buses with BAE SYSTEMS’ HybriDriveTM propulsion system. Since delivery of the first 

buses in September 1998, NYCT’s hybrids have operated in regular revenue service. NYCT’s 

experiences with the Orion VI hybrids were detailed in a DOE/NREL evaluation project completed in 

July 2002 (see reference 8). Transit staff members have proactively pushed for technology development 

in the field of electric propulsion and demonstrated their commitment to hybrid technology by ordering 

325 additional hybrid buses. 

Orange County Transportation Authority 

Orange County Transportation Authority (OCTA) provides transportation programs and services for 

Orange County, California. Its urban bus fleet covers more than 500 square miles and serves around 2.8 

million residents. OCTA’s 569 buses travel on 76 local, rail connector, and express routes that carry more 

than 210,000 riders daily. Growing demand for service in the area led OCTA to plan a 75% service level 

increase by 2010. This must be accomplished using the cleanest technologies available. As a transit 

agency in the South Coast Air Quality Management District (SCAQMD), OCTA is subject to several 

rules and regulations governing bus emissions. 

An NYCT diesel hybrid electric bus in service.
22

OCTA has demonstrated a strong commitment to advanced vehicle technology with its current fleet of 

232 liquefied natural gas (LNG) buses. Table 2 summarizes OCTA’s bus fleet. In late 2000, OCTA began 

testing its first full-sized hybrid electric bus. The two New Flyer buses received by the agency utilized the 

Allison Transmission series hybrid-electric drive system. 

Table 2. OCTA Bus Fleet 

Type Current 

Number 

Diesel Buses 

(40-foot, articulated, and shuttle) 335 

Diesel Hybrid Electric Buses 2 

LNG Buses 232 

Total Bus Fleet 569 

The buses were operated in 

service on various routes to 

determine their performance 

under different conditions. 

During the demonstration 

period, Allison Electric 

Drives decided to concentrate 

on its parallel hybrid 

technology. OCTA’s two 

hybrids are currently being 

retrofitted with this parallel 

system and will be returned to 

OCTA to continue the 

demonstration. The agency is 

considering the addition of up to 10 hybrid electric buses to its fleet. Because of this experience with 

electric propulsion technology, OCTA was invited to participate in the focus group. 

Santa Barbara Metropolitan Transit District 

The Santa Barbara Metropolitan Transit District (MTD) covers approximately 52 square miles in southern 

Santa Barbara County, California. MTD’s 96 buses provide service to about 7 million passengers per year 

on 30 transit routes. Like other California transit agencies, MTD is subject to state regulations governing 

vehicle emissions. 

Although MTD is concerned about air quality, it was 

the desire to increase ridership and control traffic 

that led the organization to investigate battery 

electric technology in the early 1990s. 

As a popular tourist destination, Santa Barbara 

needed a clean, quiet vehicle to transport passengers 

between the Downtown and the Waterfront districts. 

MTD’s diverse electric fleet consists of 24 buses 

from various manufacturers and uses several battery 

technologies. Table 3 summarizes the MTD fleet. 

OCTA’s New Flyer-Allison Hybrid Bus 

One of Santa Barbara MTD’s newest electric buses.
23

Table 3. Santa Barbara MTD Bus Fleet

Type Current 

Number 

Diesel Buses (40-foot, and 30-foot) 72 

Battery-Electric Buses 24 

Total Bus Fleet 96 

Santa Barbara has been using dedicated electric bus technologies for more than 13 years and is committed 

to using electric propulsion to reduce emissions, while improving vehicle performance. During the early 

years of testing electric buses, MTD initiated the formation of the Santa Barbara Electric Transportation 

Institute (SBETI) to help the agency understand battery electric bus technology. The purpose of SBETI is 

to “facilitate the development and application of battery-electric vehicles”. The organization works 

closely with MTD, researching battery chemistries and other components to help develop electric bus 

technology. Because of this extensive experience, the MTD was asked to participate in the focus group. 

SunLine Transit Agency 

SunLine Transit Agency is a joint powers authority that provides public transit and community services to 

California’s Coachella Valley. SunLine’s fleet of buses operates on 13 fixed routes with 900 stops and 

serves the area’s 320,000 permanent residents, as well as 4 million tourists. 

Concern for air quality in the valley spurred SunLine to become the first public transit agency in the 

United States to switch to a fleet operated 100% by CNG buses. The SunLine fleet consists of 46 CNG 

and two Hythane (a mixture of 20% hydrogen, 80% CNG) buses, three LNG powered “SuperBuses,” 

and 25 CNG shuttle buses used for demand response service. Table 4 summarizes the fleet. 

Table 4. SunLine’s Bus Fleet 

Type Current 

Number 

CNG Buses (40-foot, 30-foot) 46 

CNG Shuttle Buses 25 

Hythane Buses 2 

LNG High Capacity Shuttles 3 

Total Bus Fleet 76 

SunLine Transit Agency has demonstrated three fuel cell buses: Ballard’s Zebus, ISE 

Research’s ThunderPower bus, and Georgetown University’s methanol fuel cell bus.
24

SunLine has shown continued commitment to advanced technologies and has positioned itself as a test 

bed for implementing advanced technology vehicles. The transit agency has taken a leading role in 

technology advancement by collaboration with multiple technology partners to work toward new 

developments. SunLine is further establishing itself as a pioneer in advanced technology by being one of 

the few transit agencies currently operating fuel cell transit buses. In addition to the 40-foot fuel cell bus 

developed by Ballard, SunLine has also helped test a 30-foot ThunderPower fuel cell bus developed by 

ISE Research using a fuel cell by UTC and is hosting a methanol fueled fuel cell bus developed by 

Georgetown University. All three of the fuel cell buses have electric propulsion systems powered by fuel 

cells. Because of this experience with electric drive technology, SunLine was asked to participate in the 

focus group.

Dallas Area Rapid Transit 

Dallas Area Rapid Transit (DART) operates more than 1,000 buses, railcars, and vans serve an area of 

approximately 700 square miles, including Dallas and 12 suburban cities. Its fleet of 877 buses covers 

130 local and express routes in the area. DART has extensive experience integrating alternative fuel 

vehicles into its fleet. Table 5 summarizes the DART bus fleet. It has operated LNG buses since 1998 and 

has significant potential to expand its fleet to include advanced technology vehicles. NREL conducted an 

evaluation of DART’s LNG bus experience, which was summarized in a report published in October 

2000 (see reference 18). 

Table 5. DART Bus Fleet 

Type Current 

Number 

Diesel Buses (40-foot, 30-foot) 597 

LNG Buses (40-foot) 184 

CNG Trolley Buses (30-foot) 20 

Total Bus Fleet 801 

Although DART hasn’t actually operated electric propulsion buses, it is currently researching the 

technologies for potential integration into the fleet. The knowledge gathered, along with the experience it 

has in implementing alternative fuel vehicles into its fleet, gives DART a unique perspective to this focus 

group. DART’s report, Technical Assessment of Advanced Transit Bus Propulsion Systems, is posted on 

the AVTA Web site (see reference 22).
25

Appendix B: Focus Group Responses to Questionnaires 

New York City Transit 

What are your reasons for implementing advanced technology buses? 

To reduce bus fleet exhaust emissions, improve fuel economy, improve customer satisfaction, and 

improve reliability. 

What problems did you encounter in integrating the technology? 

All major components of the hybrid buses have undergone redesign. Intermittent electrical problems (no 

defect found) are particularly difficult. Electrical harnesses need high-quality connections. Service 

manuals and training materials need to be developed. Logical and practical troubleshooting guides need to 

be developed and used. Service and parts manuals need to be accurate and useful. Parts need to be 

available. 

What advice would you give to other transit agencies that are thinking about implementing electric 

propulsion buses? 

Be prepared to spend time and money to support the development of a new technology. Get the support of 

senior management, which should understand that new technology, in addition to incremental cost, brings 

a risk of experiencing difficulties or even failure. Have a contingency plan if the technology doesn't work. 

Don't jeopardize your ability to provide service. Deal with well-established companies that will put up 

their own money to develop the product, are committed to commercializing the technology, and will 

support the product when things don't go well. Be wary of companies that are only interested in being 

paid for development work. 

What is your overall impression of the technology and your experience? 

NYCT is excited about hybrid-electric propulsion. We are certain that this technology represents a 

fundamental improvement in energy efficiency, offering improvements in emissions, fuel economy, and 

performance—all at the same time. However, we are very aware that the technology still needs to prove it 

can be reliable and cost-effective. We adopt an approach that tries to be objective and even scientific. We 

remain highly optimistic and, at the same time, purposefully skeptical in order to objectively test, 

evaluate, challenge, and ultimately improve the technology. 

What are the top three things that need significant work and investment in order for electric 

propulsion systems to become mainstream? 

1) Diesel engines and exhaust aftertreatment systems that are sized for hybrid buses and meet EPA 

urban bus certification standards need to be developed. 

2) Energy storage systems that are reliable, cost-effective, and maximize the energy recovered from 

regenerative braking need to be developed. 

3) Diagnostic and troubleshooting systems and tools need to be easier to use; positive identification 

of failed components needs to be more achievable. 

What went well that was a surprise? 

The initial acceleration and gradeability are exceptional. Hill holding is implemented in a unique and 

effective way. 

What one thing would you do differently in your project? 

I can’t think of anything I would do differently. 
26

Orange County Transportation Authority 

What are your reasons for implementing advanced technology buses? 

Lower emissions, greater fuel efficiency, greater brake efficiency, quieter vehicles, and improved 

acceleration. 

What problems did you encounter in integrating the technology? 

Battery life; technology must be closely monitored. 

As parts failed, they were upgraded in one bus and measured against the baseline bus. 

What advice would you give to other transit agencies that are thinking about implementing electric 

propulsion buses? 

Make sure you can afford to have the staff “baby” the new bus. You also need to have the maintenance 

staff and facilities to handle high voltage on the bus. 

What is your overall impression of the technology and your experience? 

High capital cost to achieve less-than-expected fuel efficiency gain. 

What are the top three things that need significant work and investment in order for electric 

propulsion systems to become mainstream? 

1) Batteries energy storage 

2) Optimizing internal combustion engine and electric drive combination 

3) Reduce weight 

What went well that was a surprise? 

The reliability in service reached 90% before buses were returned to install the parallel drive. Coach 

operators like accelerating from electric drive, especially when climbing hills. Fuel economy gains from 

diesel hybrid electric technology were less than expected. 

What one thing would you do differently in your project? 

More staff involved in learning about the technology. 
27

Santa Barbara Metropolitan Transit District 

What are your reasons for implementing advanced technology buses? 

The primary stimulus for the implementation of battery-electric bus service in Santa Barbara was a desire 

to increase ridership. When the project was originally conceived in 1989, it was believed that a creative 

“repackaging” of urban buses (generally viewed as a stagnant technology) might serve to increase interest 

in public transit and help overcome the psychological resistance that prevents many Americans from 

patronizing such services. Electric propulsion enabled quiet, exhaust-free, odorless operation, and proved 

to be an immediate success with riders.

What problems did you encounter in integrating the technology? 

Metropolitan Transit District encountered numerous problems relating to both the novel propulsion 

system and conventional bus systems unrelated to propulsion. Foremost among the propulsion system 

problems was variable day-to-day driving range resulting from fluctuations in battery condition. A 

pragmatic and long-term commitment to making the technology work by the managers, operators, and 

maintainers of the buses overcame the problems that came up. This commitment was maintained by the 

enthusiastic reception the buses receive from the community. 

What advice would you give to other transit agencies that are thinking about implementing electric 

propulsion buses?

It is critical that the operating agency have a thorough understanding of the benefits and limitations of 

electric buses prior to procurement and operation. This includes a strong familiarity with the maintenance 

requirements of the various battery options, and the influence that local climatic extremes will have on 

battery performance and longevity. It is essential that the application is thoroughly defined prior to 

selection and procurement of electric buses and that effective personnel training programs are 

implemented. 

It has also been the Metropolitan Transit District’s experience that simple systems are oftentimes more 

effective than sophisticated (complex) ones and that efforts to improve vehicle performance through the 

use of advanced technologies do not always yield the intended benefits. 

It is also helpful to have an adequate spare-bus ratio in order to ensure uninterrupted service during 

periods when the “newness” of electric-bus technology manifests itself in problems with vehicle 

reliability. Such periods can be minimized by strictly following all practices recommended by 

manufacturers of the bus, battery, and ancillary components. 

The longstanding Santa Barbara experience with electric buses has proven that the technology can be 

successfully deployed in carefully selected transit applications. The Metropolitan Transit District’s 

success with, and commitment to, electric buses is probably best reflected by current plans to integrate an 

additional 40 electric buses into its public transit fleet. 

What is your overall impression of the technology and your experience? 

The technology has steadily improved over the last 12 years. Metropolitan Transit District has a 

successful battery-electric fleet, and we’re proud of its accomplishments. 
28

What are the top three things that need significant work and investment in order for electric 

propulsion systems to become mainstream? 

1. Electric-propulsion systems on transit-quality buses from established bus makers would be 

number one on the list. Many electric buses were built by “boutique” builders, and their limited 

experience with the rigors of transit operations has been a serious shortcoming in electric buses. 

2. Electric propulsion systems need to utilize battery technologies that are truly maintenance free. 

This does not simply mean that watering is not required; the battery must also not require load 

testing, cell replacements, inspection of intercell connections, or cleaning. 

3. More of #1 and #2. 

What went well that was a surprise? 

Reception of electric buses by the community wasn’t really a surprise, but the intensity of the 

community’s support for the project surpassed expectations. 

What one thing would you do differently in your project? 

An intensive management and mitigation policy for technical risks should be part of any new technology 

project. Metropolitan Transit District has learned that the promises of new technology need to be 

demonstrated. 
29

SunLine Transit Agency 

What are your reasons for implementing advanced technology buses? 

Since 1992 our goals have been: 

1) Air Quality: We see Los Angeles smog coming into the valley through the pass. 

2) Overall Environment: Tourism and agriculture are the main industries in the area. 

3) Health Effects 

What problems did you encounter in integrating the technology? 

With the CNG buses, there were early pressure relief device problems because of the immature 

technology. These problems were solved. 

For the fuel cell bus demonstration there were no problems on SunLine's part. Maintenance was done by 

an original equipment manufacturer. We did have an issue with liability—if an agency participates in 

demo project and doesn’t own the bus, insurance agencies have a problem covering the bus. This 

happened with the ThunderPower fuel cell bus demonstration. We had to have the fuel cell bus shadow 

another bus for three months before the insurance company would allow passengers to ride in revenue 

service. Another issue early on with fuel cell buses operating on hydrogen was codes and standards. 

SunLine raised this issue early on, and now there is much progress being made by both government and 

industry. 

What advice would you give to other transit agencies that are thinking about implementing electric 

propulsion buses? 

Before making a decision, learn all you can about the technology. Visit other transit agencies that have 

experience with the technology. There is a very high risk associated with being an early adopter of 

technology. It was difficult with CNG, it will be worse with fuel cell buses. Transit agencies will have an 

advantage if they have experience with CNG. 

What is your overall impression of the technology and your experience? 

Experience was great. Our concerns for the future are affordability, durability, and reliability. 

What are the top three things that need significant work and investment in order for electric 

propulsion systems to become mainstream? 

1) Reliability/Durability of the Fuel Cell 

2) Cost 

3) Infrastructure (for Hydrogen) 

What went well that was a surprise? 

With the ThunderPower bus, that it worked so well. We expected some difficulties, but they never 

happened. 

What one thing would you do differently in your project? 

Better planning for funds to cover project. It is easy to underestimate time, manpower, and other the needs 

it takes to run a project with advanced buses. It also took much more effort and time to maintain 

infrastructure.
30

Dallas Area Rapid Transit 

What are your reasons for implementing advanced technology buses? 

Texas Clean Fleet program was fuel-based and was later revised to be an emissions-based program. 

What problems did you encounter in integrating the technology? 

 Multi-tank LNG systems did not fill, fuel economy was low, spark plug life was low, high fuel 

cost per mile, cylinder head valve and valve seat eroded (burn path) 

 Oxygen sensors and calibration misfired 

 Lack of tank information from supplier 

Based on your research, what advice would you give to other transit agencies that are thinking 

about implementing electric propulsion buses? 

Build your knowledge base on the technology and what's required for your specific service needs. Try not 

to introduce too many new technologies at once. There is a steep learning curve for maintenance staff 

with any new technology. You need to know what training is required to get workers up to the base level 

for the new technology. Plan for the transition by training staff about the new buses. This will be 

necessary for any large implementation of the technology. 

What is your overall impression of the technology based on what you’ve learned? 

We have determined fuel cell buses are not cost effective for DART at this stage, but we are very excited 

about hybrids. DART is investigating hybrid buses and plans to purchase a number of them by 2010. 

What are the top three things that need significant work and investment in order for electric 

propulsion systems to become mainstream? 

We would like to see reduction in capital cost of the buses, improvements to battery technology, and a 

demonstrated reliability of the buses in revenue service. 
31

Federal Transit Administration (FTA) 

What is FTA’s perspective on the status of electric propulsion technology in transit? 

Hybrid propulsion systems for transit are in the early stage of commercial market introduction—a 

Generation I stage. Battery electric buses for certain niche applications are at the commercial stage. 

Transit agencies, however, need to look at the capabilities of battery buses and the needs of their specific 

application. 

What advice would you give to transit agencies looking at advanced technology buses? 

The key to success is to match the capabilities of the technology with the requirements of each agency’s 

duty cycle. An agency must have a good understanding of what it takes to operate and maintain advanced 

technology buses. Also, the riding public has shown they like the new cleaner and quieter technologies. 

Although difficult, agencies should try to quantify the public relations benefit of using these technologies. 

What other activities does FTA have in the area of electric propulsion transit buses? 

The FTA is in the process of pulling together a comprehensive fuel cell bus program. The main goal is to 

achieve zero-emission, fuel-efficient buses. We see electric propulsion technology, including battery, 

hybrid, and fuel cell, as the path to this end. All work on electric drive systems help to push us closer to 

the goal. In the late 80s, FTA programs helped transit place natural gas vehicles into their fleets to help 

reduce pollution. That same kind of effort toward funding capital costs of electric propulsion vehicles 

would go a long way to pushing the technology to commercialization. 

What is the job/role that transit is playing in developing this technology? 

Transit has been at the forefront of advanced propulsion technology. Both FTA and transit agencies have 

critical roles to play in transition from R&D to commercialization. Transit systems also can help pave the 

way for light-duty applications. There are synergies for the work done in all transportation applications. 
32

U.S. Department of Energy (DOE) 

What is DOE’s perspective on the status of electric propulsion technology in transit? 

DOE views transit applications as an ideal use for advanced electric and hybrid technologies. The size, 

performance requirements, and operational characteristics of transit buses allow for easier integration of 

electric and hybrid systems than in any other vehicle class. Although many issues are still being 

addressed, great advances have been realized recently and the remaining barriers are deemed far from 

insurmountable. 

What advice would you give to transit agencies looking at advanced technology buses? 

Transit agencies that are looking at advanced technology transit buses should collect information on all 

available technology options before locking in on a specific technology. Information sources include 

government programs, such as DOE’s Advance Vehicle Technology Analysis and Evaluation Activities, 

transit and advanced vehicle associations, and transit agencies that have experience with advanced 

technology buses. Once this information has been obtained and reviewed, an educated decision on the 

appropriate technology for the agencies mission and vehicle requirements can be made. 

What other activities does DOE have in the area of electric propulsion transit buses? 

DOE is investing significant time and resources to develop batteries, motors, controllers, and other 

electric and hybrid vehicle system components that will improve efficiency and reliability while lowering 

overall vehicle costs. These technologies will be used in various models of advanced technology vehicles, 

ranging from passenger cars and light trucks to heavy-duty trucks and transit buses. 

What is the job/role that transit is playing in developing this technology? 

DOE is encouraged by the willingness of forward-thinking transit agencies to place advanced technology 

buses in revenue service and use their experiences to assist the manufacturers in improving and refining 

these technologies. This will ultimately allow advanced technology transit buses to reliably and costeffectively serve in revenue service with other transit agencies across the country and thus help reduce the 

use of petroleum in the United States. 
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Challenges and Experiences with Electric Propulsion Transit Buses in the United States 

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This document provides background to transit agencies and other fleets who are considering the use of electric propulsion 

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