A national laboratory of the U.S. Department of Energy 

Office of Energy Efficiency & Renewable Energy 

National Renewable Energy Laboratory 

Innovation for Our Energy Future 

Conference Paper Interim Evaluation Results 

NREL/CP-540-37752 from New Flyer/Allison May 2005 

Hybrid Buses at King County 

Metro 

Preprint 

K. Chandler, E. Eberts 

Battelle 

L. Eudy 

National Renewable Energy Laboratory 

To be presented at the American Public Transportation 

Association Bus and Paratransit Conference 

Columbus, Ohio 

May 15-18, 2005 

NREL is operated by Midwest Research Institute ● Battelle Contract No. DE-AC36-99-GO10337 
NOTICE 

The submitted manuscript has been offered by an employee of the Midwest Research Institute (MRI), a 

contractor of the US Government under Contract No. DE-AC36-99GO10337. Accordingly, the US 

Government and MRI retain a nonexclusive royalty-free license to publish or reproduce the published form of 

this contribution, or allow others to do so, for US Government purposes. 

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, makes any 

warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or 

usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not 

infringe privately owned rights. Reference herein to any specific commercial product, process, or service by 

trade name, trademark, manufacturer, or otherwise does not necessarily 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. 

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

Available for a processing fee to U.S. Department of Energy 

and its contractors, in paper, from: 

U.S. Department of Energy 

Office of Scientific and Technical Information 

P.O. Box 62

Oak Ridge, TN 37831-0062 

phone: 865.576.8401 

fax: 865.576.5728 

email: mailto:reports@adonis.osti.gov 

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

U.S. Department of Commerce 

National Technical Information Service 

5285 Port Royal Road 

Springfield, VA 22161 

phone: 800.553.6847 

fax: 703.605.6900 

email: orders@ntis.fedworld.gov 

online ordering: http://www.ntis.gov/ordering.htm 

Printed on paper containing at least 50% wastepaper, including 20% postconsumer waste 
Interim Evaluation Results from New Flyer/Allison Hybrid 

Buses at King County Metro 

Kevin Chandler 

Battelle 

Leslie Eudy 

National Renewable 

Erin Eberts 

Battelle 

Columbus, Ohio Energy Laboratory 

Golden, Colorado 

Columbus, Ohio 

ABSTRACT 

The National Renewable Energy Laboratory (NREL) 

is evaluating hybrid buses at King County Metro (KC 

Metro) in Seattle, Washington. The buses are diesel 

hybrid electric articulated buses from New Flyer, 

equipped with the Allison parallel hybrid propulsion 

system. The evaluation will compare the performance of 

20 hybrid buses and 10 diesel buses from the same order. 

This evaluation also will include a comparison of the 

hybrid and diesel buses to the Breda dual-mode buses that 

are being replaced by this new order of buses at KC 

Metro. 

INTRODUCTION 

The U.S. Department of Energy (DOE) has been 

evaluating heavy-duty advanced propulsion and 

alternative fuel vehicles for many years through the 

National Renewable Energy Laboratory (NREL). Current 

advanced heavy vehicle propulsion evaluations are being 

accomplished as part of DOE’s Advanced Vehicle 

Testing Activity (AVTA) in the FreedomCAR and 

Vehicle Technologies Program [1]. The primary goal of 

AVTA is to benchmark and validate the performance of 

light-, medium-, and heavy-duty vehicles that feature one 

or more advanced technologies, including the following: 

• Internal combustion engines burning advanced 

fuels such as 100% hydrogen and 

hydrogen/compressed natural gas-blended fuels 

• Hybrid electric, pure electric, and hydraulic drive 

systems 

• Advanced batteries and engines 

• Advanced climate control, power electronic, and 

other ancillary systems. 

By benchmarking the performance and capabilities of 

advanced technologies, AVTA supports the development 

of industry and DOE technology targets. The testing 

results are also leveraged as input to component, system, 

and vehicle models, as well as hardware-in-the-loop 

testing. 

AVTA produces information resources that support 

the decisions fleet managers and the public make when 

acquiring advanced technology vehicles. The testing 

results are presented in easy-to-understand formats that 

allow users to compare the performance of different types 

of vehicles. 

EVALUATION AT KING COUNTY METRO 

The Fleet Test & Evaluation team at NREL, which 

includes NREL and Battelle staff, is conducting the 

AVTA evaluation of diesel hybrid electric articulated 

buses at King County Metro (KC Metro) in Seattle, 

Washington. Objectives of this evaluation include the 

following: 

• Provide credible data and evaluation results that 

show progress and experience for hybrid electric 

bus and infrastructure operation in transit service 

• Add to the body of information about 

performance of advanced vehicles at different 

transit agencies and in different operating 

conditions. 

This information is important for estimating what the 

future technology and costs of operation may be based on 

the experiences of these operations and expected 

advances in systems integration and development. 

1
KING COUNTY METRO TRANSIT 

KC Metro [2] operates transit service in the 

Seattle/King County, Washington area (2,134 squaremiles), including approximately 1,300 standard and 

articulated buses, electric trolleys, dual-powered buses, 

and streetcars. Annual ridership is approximately 100 

million trips. KC Metro has committed to supplying 

environmentally sound and energy efficient transportation 

through several initiatives, including the following: 

• Retrofit of existing bus fleet with diesel 

particulate filters and use of ultra low sulfur 

diesel (ULSD) fuel. ULSD is a specially refined 

fuel with much lower sulfur content than regular 

highway diesel. The sulfur content ranges from 

15 to 30 parts per million. 

• Continuing use of zero-emission electric trolley 

buses to supply clean and quiet transportation on 

some of the busiest routes. 

• Using re-refined engine oil and special 

formulation transmission oil to increase 

recycling and decrease waste oil disposal. 

• Continuing use of the 1.3-mile electric bus 

tunnel underneath downtown Seattle (Figure 1). 

Only very low emission and electric buses are 

used in the tunnel. 

Figure 1. Seattle Downtown Metro Bus Tunnel 

The latest transit improvement at KC Metro is the use 

of new hybrid electric articulated buses, which replace 

dual-mode Breda buses (Figure 2). The Breda buses, 

which have been used in the Metro Bus Tunnel since its 

opening in 1990, allow for electric propulsion in the 

tunnel and diesel engine propulsion outside the tunnel or 

when off the electric catenary. These buses were 

developed especially for this tunnel application, but they 

have been expensive to operate and, at 14 years old, have 

exceeded their expected useful operating life. The 

technology in the new hybrid electric buses reduces 

emissions compared with the Breda buses by converting 

energy that is normally wasted in braking into electricity 

used to help the bus accelerate (i.e., regenerative braking). 

Figure 2. Breda Dual-Mode Bus in Yard 

NEW FLYER/ALLISON HYBRID BUSES 

At around the same time KC Metro began 

investigating replacements for the Breda buses, it was 

making plans to add light rail to the downtown tunnel 

operation. The light rail requires 1,500 VDC, and the 

dual-mode bus catenary is 700 VDC. For the light rail and 

dual-mode buses to operate in the tunnel at the same time, 

both catenary systems would need to coexist in the tunnel, 

which KC Metro did not find desirable. The agency 

wanted a replacement bus technology that met the 

following objectives: 

1. Be capable of operating in the tunnel with low 

tailpipe and noise emissions, preferably without 

the catenary system 

2. Be capable of significantly reduced operations 

and maintenance costs compared with the Breda 

dual-mode buses 

3. Be capable of operating on routes other than 

those in the tunnel. 

The search for a replacement bus technology 

occurred at the start of 2000, around the same time that 

Allison Transmission (a division of General Motors) 

2
began investigating potential test fleets for their new 

hybrid bus drive system. Based on a conference 

presentation by Allison, a discussion between Allison and 

KC Metro began. Allison demonstrated its technology at 

KC Metro using a 40-foot bus with a trailer. After this 

testing, KC Metro demonstrated the technology by 

purchasing one hybrid bus, which was manufactured by 

New Flyer. 

The demonstration bus was received in October 2002 

and was immediately put into test service, shadowing 

another in-service bus. The goal was to put a year’s worth 

of operation on the bus as quickly as possible. The bus 

was loaded to 130% seated load weight and operated in 

mock revenue service (shadow service) from November 

2002 through February 2003, 7 days a week, from noon to 

8:00 am the next morning. The bus was serviced between 

8:00 am and noon. The bus was operated for 37,000 miles 

during this testing. Allison documented this test in a video 

[3]. 

This first hybrid bus used a Cummins ISL engine 

(330 hp). In December 2002, Cummins notified KC 

Metro that it could not meet 2004 bus emissions standards 

with its 330 hp engine and withdrew from the project. 

Soon after, Caterpillar expressed interest in providing 

high horsepower engines for the bus industry. The project 

team switched to Caterpillar’s C9 diesel engine, which 

was certified for emissions at 330 hp. New Flyer 

reengineered the demonstration bus; the changes added 7 

inches to the rear of the bus to accommodate the 

Caterpillar engine. 

In April 2003, KC Metro released a request for 

proposals (RFP) for 265 buses, including 213 60-foot 

articulated hybrid buses for KC Metro, 22 60-foot 

articulated hybrid buses for nearby Sound Transit, and 30 

conventional diesel 60-foot articulated buses for KC 

Metro. The RFP included only standard performance 

criteria—KC Metro wanted to give the manufacturer 

design flexibility—and the Caterpillar engine was added 

to the RFP. The contract was signed in October 2003, 

with New Flyer including the Allison electric drive and 

Caterpillar C9 engine. The hybrid articulated buses cost 

$645,000 each. This new order had minor changes from 

the original demonstration bus, including the change to 

the C9 engine and the change of the drive axle from 

ArvinMeritor to MAN. 

CURRENT STATUS 

As of March 2005, all the new hybrid and diesel 

articulated buses (Figure 3 and 4) had been received and 

were in service. Table 1 shows the bus specifications. The 

buses are operating from five locations at KC Metro: 

1. South Base – 75 hybrid buses 

2. Ryerson Base – 30 diesel buses 

3. East Base – 38 hybrid buses 

4. North Base – 48 hybrid buses 

5. Atlantic Base – 52 hybrid buses 

Figure 3. New Flyer 60-Foot Articulated Diesel Bus at Ryerson Base 

Figure 4. New Flyer 60-Foot Articulated Hybrid Bus Awaiting Prep 

for Service 

3
Table 1. New Flyer/Allison Bus Descriptions • Hybrid buses: 10 buses from South Base and 10 

buses from Atlantic Base. 

Description KC Metro New 

Flyer/Allison Buses 

Buses 2004 New Flyer 

DE60LF 

Length/Width/Height 60.7 ft/102 in/132 in 

GVWR/Curb Weight 66,790/44,600 lb 

Seated Passenger 58 (or 50 and 2 

Capacity wheelchairs) 

Engine Caterpillar C9, 8.8L 

Engine Rating 330 hp @ 2,100 rpm 

1,150 ft-lb @ 1,300 rpm 

Emissions Certification 2.5 g/bhp-hr NOx + HC 

(with DPF) 0.5 g/bhp-hr PM 

Fuel Storage 125 gal (ULSD) 

Propulsion Allison Ep50 Parallel 

Hybrid System 

Motor/Generator 15 kW nominal, 150 kW 

peak 

Drive Unit Ev50 Drive: 246 kW 

input 

rating, 1,050 ft-lb torque 

Controls Allison (proprietary) 

Energy Storage Nickel metal hydride 

batteries, 600 VDC 

Regenerative Braking Yes 

EVALUATION PLANS 

The evaluation at KC Metro is intended to be a Full 

Evaluation as defined in the DOE/NREL General 

Evaluation Plan [4]. This type of evaluation is 

concentrated on commercial or nearly commercial 

technology vehicles and generally includes at least five of 

the advanced technology propulsion vehicles and three or 

more conventional propulsion vehicles matched as closely 

as possible in operation and vehicle type. The data 

collection period is intended to be at least 12 months. 

Plans for the KC Metro evaluation include selecting 

10 diesel and 20 hybrid buses for detailed study. The 

diesel buses are exactly the same bus and engine as in the 

hybrid buses but do not have the Allison hybrid 

propulsion system. The evaluation also includes a study 

of two specific routes for the diesel and hybrid buses that 

are closely matched in operation, to yield a detailed fuel 

economy comparison: 

• Diesel buses: 10 buses from Ryerson Base 

The evaluation also will compare the introduction 

and operation of the diesel hybrid buses with the Breda 

dual-mode buses, which should demonstrate the business 

case for purchasing the hybrid buses. The evaluation 

includes several levels of data collection: 

1. Experience implementing the hybrid electric 

articulated buses and infrastructure 

2. Detailed descriptions of the vehicles used in the 

evaluation 

3. Public awareness materials and public perception 

of the projects 

4. Vehicle performance testing as made available 

from the manufacturers and transit agencies 

5. Facilities built or used specifically for this 

demonstration, including fueling and 

modifications to existing structures to 

accommodate hybrid electric buses 

6. Capital costs for vehicles, facilities, and training 

7. Safety and training at each site 

8. Descriptions of baseline operations for standard 

buses at the site using the newest available and 

appropriate standard bus operations for diesel 

buses 

9. Operations data collection: vehicle and fueling 

infrastructure, duty cycle/assignment, fueling, 

maintenance, and configuration/design changes. 

REPORTING 

Three reports will be produced from this evaluation: 

• Start-up report: two-page description of KC 

Metro, the hybrid bus technology, and the 

evaluation plans [5] 

• Interim report: eight- to twelve-page description 

of interim results such as performance, fuel 

economy, maintenance issues, implementation 

experience, and status of the technology 

development; planned for availability in late 

summer 2005 

4
• Final report: 16- to 24-page description of full 

final results; planned for availability in early 

2006. 

WHAT WILL BE IN THE PRESENTATION 

The presentation at the APTA 2005 Bus and 

Paratransit Conference will give background information, 

including a thorough description of the buses and the 

hybrid propulsion system. It will also give KC Metro’s 

introduction experience, including early data and 

evaluation results such as fuel economy and operating 

costs. 

ACKNOWLEDGEMENTS 

We would like to thank DOE’s Office of Energy 

Efficiency and Renewable Energy, Office of 

FreedomCAR and Vehicle Technologies, and Lee Slezak, 

Manager of the Advanced Vehicle Testing Activity, for 

their support. We would also like to thank the project 

partners, including Jim Boon, George Stites, Todd Gibbs, 

and Ann Gonzalez at KC Metro and Peter Chiang at 

Allison Transmission. 

ENDNOTES 

1. U.S. Department of Energy FreedomCAR & Vehicle 

Technologies Web site: 

www.eere.energy.gov/vehiclesandfuels/. 

2. King County Metro Transit Web site: 

http://transit.metrokc.gov/. 

3. Allison Transmission: Allison Electric Drives King 

County Seattle Phases 1 & 2 Test. CD3713EN, 2003. 

Visit www.allisontransmission.com/publications/index.jsp 

to obtain. 

4. National Renewable Energy Laboratory: General 

Evaluation Plan, Fleet Test & Evaluation Projects. 

Golden, CO: National Renewable Energy Laboratory. 

Report no. NREL/BR-540-32392, 2002. Visit 

www.eere.energy.gov/afdc to obtain. 

5. National Renewable Energy Laboratory: King County 

Metro Transit. Advanced Technology Vehicles in Service: 

Diesel Hybrid Electric Buses. Golden, CO: National 

Renewable Energy Laboratory. Report no. DOE/GO102004-2026, 2004. Visit www.eere.energy.gov/afdc to 

obtain. 

5
REPORT DOCUMENTATION PAGE Form Approved 

OMB No. 0704-0188 

The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, 

gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this 

collection of information, including suggestions for reducing the burden, to Department of Defense, Executive Services and Communications Directorate (0704-0188). Respondents 

should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a 

currently valid OMB control number. 

PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ORGANIZATION. 

1. REPORT DATE (DD-MM-YYYY) 

May 2005 

2. REPORT TYPE 

Conference Paper 

3. DATES COVERED (From - To) 

4. TITLE AND SUBTITLE 

Interim Evaluation Results from New Flyer/Allison Hybrid Buses at 

King County Metro: Preprint 

5a. CONTRACT NUMBER 

DE-AC36-99-GO10337 

5b. GRANT NUMBER 

5c. PROGRAM ELEMENT NUMBER 

6. AUTHOR(S) 

K. Chandler, E. Eberts, and L. Eudy 

5d. PROJECT NUMBER 

NREL/CP-540-37752 

5e. TASK NUMBER 

FC05-3000 

5f. WORK UNIT NUMBER 

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 

National Renewable Energy Laboratory 

1617 Cole Blvd. 

Golden, CO 80401-3393 

8. PERFORMING ORGANIZATION 

REPORT NUMBER 

NREL/CP-540-37752 

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S) 

NREL 

11. SPONSORING/MONITORING 

AGENCY REPORT NUMBER 

12. DISTRIBUTION AVAILABILITY STATEMENT 

National Technical Information Service 

U.S. Department of Commerce 

5285 Port Royal Road 

Springfield, VA 22161 

13. SUPPLEMENTARY NOTES 

14. ABSTRACT (Maximum 200 Words) 

The National Renewable Energy Laboratory (NREL) is evaluating hybrid buses at King County Metro (KC Metro) in 

Seattle, Washington. The buses are diesel hybrid electric articulated buses from New Flyer, equipped with the Allison 

parallel hybrid propulsion system. The evaluation will compare the performance of 20 hybrid buses and 10 diesel 

buses from the same order. This evaluation also will include a comparison of the hybrid and diesel buses to the 

Breda dual-mode buses that are being replaced by this new order of buses at KC Metro. 

15. SUBJECT TERMS 

doe; nrel; hybrid electric; king county; articulated; public transit; buses 

16. SECURITY CLASSIFICATION OF: 17. LIMITATION 

OF ABSTRACT 

UL 

18. NUMBER 

OF PAGES 

19a. NAME OF RESPONSIBLE PERSON 

a. REPORT 

Unclassified 

b. ABSTRACT 

Unclassified 

c. THIS PAGE 

Unclassified 19b. TELEPHONE NUMBER (Include area code) 

Standard Form 298 (Rev. 8/98) 

Prescribed by ANSI Std. Z39.18 

F1147-E(12/2004)