National Renewable Energy Laboratory 

Innovation for Our Energy Future 

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

Office of Energy Efficiency & Renewable Energy

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

King County Metro Transit 

Hybrid Articulated Buses: 

Interim Evaluation Results 

K. Chandler 

Battelle 

K. Walkowicz 

National Renewable Energy Laboratory

Technical Report 

NREL/TP-540-39742 

April 2006 
King County Metro Transit 

Hybrid Articulated Buses: 

Interim Evaluation Results 

K. Chandler 

Battelle 

K. Walkowicz 

National Renewable Energy Laboratory

Prepared under Task No. FC06.3000 

Technical Report 

NREL/TP-540-39742 

April 2006 

National Renewable Energy Laboratory 

1617 Cole Boulevard, Golden, Colorado 80401-3393 

303-275-3000 • www.nrel.gov 

Operated for the U.S. Department of Energy 

Office of Energy Efficiency and Renewable Energy 

by Midwest Research Institute • Battelle 

Contract No. DE-AC36-99-GO10337
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Acknowledgements 

This evaluation is funded through the Advanced Vehicle Testing Activity, which is managed by 

Lee Slezak within the FreedomCAR & Vehicle Technologies Program in the U.S. Department of 

Energy (DOE). All publications on the King County Metro Transit hybrid bus evaluation will be 

posted on the DOE Office of Energy Efficiency and Renewable Energy Web site. Please see 

http://www1.eere.energy.gov/vehiclesandfuels/avta. 

This evaluation conducted at King County Metro Transit (KC Metro) would not have been 

possible without the support and cooperation of many people. Therefore, the authors wish to 

thank each of the following: 

U.S. Department of Energy 

Lee Slezak 

NREL 

Leslie Eudy 

KC Metro 

Jim Boon 

Colleen Duke 

Bernie Durant 

Todd Gibbs 

Ann Gonzales 

Wayne Hom 

Lynn Matteoni 

Jo Merrick 

George Stites 

GM Allison 

Peter Chiang 

New Flyer Industries 

Rick Brandenburg 

Paul Zanetel 

Caterpillar 

Dave Bradshaw 

NC Power 

Bill Hofer 

iii
iv
Table of Contents 

Executive Summary....................................................................................................................... vi 

Project Design and Data Collection........................................................................................... vi 

Hybrid and Diesel Buses........................................................................................................... vii 

Implementation Experience ...................................................................................................... vii 

Evaluation Results ...................................................................................................................viii 

Emissions Testing ....................................................................................................................... x 

Future Work................................................................................................................................ x 

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

Advanced Vehicle Testing Activity............................................................................................ 1 

Host Site Profile—KC Metro Transit ......................................................................................... 2 

Description of the KC Metro Hybrid Transit Bus Project.......................................................... 2 

Project Design and Data Collection............................................................................................ 8 

Vehicle System Descriptions...................................................................................................... 9 

Facility Descriptions..................................................................................................................... 14 

Implementation Experience .......................................................................................................... 16 

Evaluation Results (6 of 12 Months) ............................................................................................ 18 

Route Descriptions.................................................................................................................... 18 

Bus Usage ................................................................................................................................. 19 

Fuel Economy and Cost............................................................................................................ 20 

Maintenance Cost Analysis....................................................................................................... 23 

Road Call Analysis ................................................................................................................... 32 

Laboratory Emissions Testing .................................................................................................. 34 

Future Work.................................................................................................................................. 36 

Contacts......................................................................................................................................... 37 

Acronyms and Abbreviations ....................................................................................................... 38 

Bibliography ................................................................................................................................. 40 

Appendix: Fleet Summary Statistics............................................................................................. 42 

v
Executive Summary 

This document is an interim technical report on a comparison and evaluation of new diesel and 

diesel hybrid-electric articulated buses operated as part of the King County Metro Transit (KC 

Metro) fleet in Seattle, Washington. This interim report covers the first six months of a planned 

12-month evaluation at KC Metro. The evaluation is being completed through the U.S. 

Department of Energy’s (DOE) Advanced Vehicle Testing Activity (AVTA) by the National 

Renewable Energy Laboratory (NREL). Publication of the final report covering all 12 months of 

the evaluation is planned for fall 2006. 

KC Metro operates bus-only transit service in the 2,134-square-mile Seattle/King County, 

Washington, area. Its fleet consists of 1,400 standard and articulated buses, trolley buses, and 

streetcars. KC Metro recently began using 235 new hybrid-electric articulated buses that replace 

an older fleet of 236 dual-mode Breda articulated buses. The Breda buses were specially 

developed for use in the 1.3-mile Seattle downtown transit tunnel since its opening in 1990. This 

tunnel was built with light rail in mind but had been used only by the Breda dual-mode buses 

until the hybrid buses were introduced. The Breda dual-mode buses allowed zero-emission, fully 

electric propulsion operation inside the tunnel and diesel engine propulsion outside the tunnel or 

when the buses were not connected to the electric catenary system.1

 

Both the diesel and diesel hybrid-electric articulated buses at KC Metro were manufactured by 

New Flyer Industries. The hybrid buses include the General Motors (GM) Allison EP50 System

parallel hybrid propulsion system. This fleet is the largest application of the GM Allison hybrid 

propulsion system to date. 

Project Design and Data Collection 

This evaluation focuses on diesel and hybrid diesel buses selected from three of KC Metro’s 

seven operating depots, or bases (see Table ES-1). All 30 of the new diesel articulated buses 

currently operate from the Ryerson Base depot; they are identical to the hybrid buses except for 

the hybrid-electric propulsion systems. Ten diesel buses were selected from Ryerson Base for 

detailed evaluation, and 10 hybrid buses were selected from Atlantic Base for comparison. The 

Ryerson diesel buses and the Atlantic hybrid buses have similar service and duty cycles—

downtown service at an average speed of 13.3 mph for Ryerson and 11.2 mph for Atlantic. 

Table ES-1. Summary of Evaluation Sites and Buses

Topic Ryerson Base Atlantic Base South Base 

Number of Buses in 

Evaluation 10 10 10 

Bus Type Diesel Only Diesel Hybrid Diesel Hybrid 

 

1

 A catenary system features electricity-carrying wires strung above a roadway. Buses and trolley vehicles can obtain 

access to electric power via poles that touch the catenary wires and provide electricity directly to the electric 

propulsion system in the bus. Many light rail systems also use a catenary system to provide the light rail vehicle with 

access to electricity and power for propulsion. 

vi
South Base hybrid buses (10 buses) were also selected for study, because that depot was the first 

to receive the new hybrid vehicles. South Base provided an opportunity to study an early 

implementation experience with the new technology at KC Metro, as well as to look at longer 

term potential maintenance and reliability issues that might arise in these oldest of the fleet buses. 

South Base has a higher operating average speed (19.2 mph for articulated buses) than the other 

two depots and should not be used in direct comparisons . Data from this depot are therefore 

provided in this report for reference only. In many cases, the South Base evaluation results appear 

in gray type in this report as a reminder that the information is not intended to be directly 

compared with results from the other two depots. 

Hybrid and Diesel Buses 

The New Flyer diesel and diesel-hybrid articulated buses are identical except for the hybrid 

propulsion system. Both propulsion systems are equipped with Caterpillar engines (C9–330 brake 

horsepower [bhp] maximum, 1150 ft-lb torque and diesel particulate filters [DPF]). The hybrid 

buses weigh approximately 1,100 lb more than the diesels, but this does not make a difference in 

the number of passengers that can be carried because there is not enough standing space on either 

one to take the bus to the gross vehicle weight rating (GVWR). 

The GM Allison EP

50 parallel electric propulsion system has a drive unit that contains two 

motors and fits where a standard-size transmission would normally be placed in the bus. Each 

motor, which can act as a generator, is capable of 75 kW continuous power and up to 150 kW 

peak power. In the hybrid buses, the C9 engine is used primarily for highway driving, and the 

electric motor provides power during hill climbing, acceleration, and other periods of high power 

demand. The energy storage system for the hybrid-electric system consists of nickel metal 

hydride batteries, and the system operates with regenerative braking, i.e., braking energy is 

captured back through the motor/generator set and used later for propulsion along with the energy 

saved in the battery pack. The engine is also capable of charging the energy storage system along 

with the regenerative braking energy. 

Implementation Experience 

New diesel and diesel-hybrid articulated buses were delivered to KC Metro at nearly the same 

time in May 2004. The 30 diesel buses were on site and in service at Ryerson Base depot by July 

2004. All 235 hybrid buses were delivered and put into service at Atlantic Base and South Base 

as well as two other depots by early December 2004. 

KC Metro reported that there were no significant issues in placing any of these buses into service, 

which took only a few weeks once each bus was delivered to Seattle. As the new articulated buses 

were placed in service, the older Breda buses were retired out of service. Caterpillar (CAT) and 

GM Allison have used a local dealer for warranty support and in troubleshooting problems with 

these buses. New Flyer made one mechanic/technician available on site for KC Metro’s needs. 

The buses are reportedly doing well; through September 2005, the 235 hybrid buses had operated 

for 8.8 million miles and the diesel buses for 1.1 million miles. 

vii
The hybrid and diesel buses have been operating with only a few significant issues. There have 

been a few fleet defects and campaigns of warranty repairs as the manufacturers gained more 

experience with the KC Metro operation and environment as well as specific design issues 

concerning the integration of the bus systems. A fleet defect is defined in the contract between the 

transit agency and the manufacturer as failures of the same type occurring on multiple buses in an 

order. A campaign is a repair (typically covered under warranty) that is applied to an entire (or 

significant portion) of an order of buses. The following list summarizes some of the significant 

(major) campaigns for the propulsion system of these buses: 

1. Axle planetary snap rings (8/2004) 

2. Allison software upgrade for issues with the inverter and CAT engine software changes 

(9/2004) 

3. Proheat auxiliary coolant heater software change (1/2005) 

4. Relocation of the DPF and change of the thermal blanket (2/2005) 

5. Allison software upgrade for additional CAT engine software changes and hush mode 

hybrid thermal protection (5/2005) 

6. Allison software upgrade for removing hush mode and a few software enhancements 

(10/2005) 

One significant problem that has not yet registered as a fleet defect or warranty campaign is the 

problem with the CAT engine turbocharger. This problem, caused by heavier than expected 

usage, has resulted in a few turbocharger failures and, ultimately, DPF failures because of engine 

oil leaking into the exhaust through the damaged turbocharger. CAT plans to replace the 

turbocharger compressor wheels with ones made with titanium to alleviate this issue. 

April 1, 2005, was chosen as a “clean point” for the evaluation because by then the major 

campaigns listed above were completed. The evaluation period selected for this interim report is 

April through September 2005. The entire 12-month evaluation period is April 2005 through 

March 2006. 

Evaluation Results 

The evaluation results presented in this report focus on the diesel buses operating from Ryerson 

Base (RB) and hybrid buses operating from Atlantic Base (AB). These two depots were chosen 

for the evaluation because of their similar duty cycles (average speeds of 13.3 mph at RB and 

11.2 mph at AB), as noted earlier. South Base (SB) hybrid buses are included in the evaluation 

only to note some experiences in implementing the first hybrids at KC Metro. The duty cycle of 

the SB hybrid buses was significantly different from those at the other two depots (an average 

speed of 19.2 mph), is not directly comparable, and is included in this report for reference only. 

Table ES-2 summarizes the evaluation results presented in greater detail later in this report. Note 

that SB hybrid data are presented but not included in the comparison discussion. Regarding 

maintenance costs, mechanic labor was kept constant at $50 per hour, which does not reflect an 

actual labor rate at KC Metro. The warranty parts cost per mile is shown in the table but is not 

included in any of the other cost calculations. Data in the table column titled “Hybrid Difference” 

was calculated in this manner: (Result Hybrid AB / Result Diesel RB – 1)* 100% 

viii
A positive result (+) indicates that the hybrid AB result was higher than the diesel RB result. A 

negative result (-) indicates that the hybrid AB result was lower than the diesel RB result. 

Table ES-2. Summary Evaluation Results (6-month evaluation period)

Category Diesel RB Hybrid AB 

Hybrid 

Difference Hybrid SB 

Monthly Average Mileage per Bus 2,908 2,985 +3% 4,139 

Fuel Economy 2.55 3.21 +26% 3.75 

Fuel Cost per Mile ($) 0.78 

(0.76 adj)* 

0.61 -22% 

(-20% adj)* 

0.52 

Total Maintenance Cost per Mile ($) 0.46 0.47 +2% 0.46 

Propulsion-Only Maintenance Cost 

per Mile ($) 

0.14 0.14 0 0.16 

Warranty Parts Cost per Mile ($) 0.06 0.08 +33% 0.17 

Total Operating Cost per Mile ($) 1.25 

(1.23 adj)* 

1.07 -14% 

(-13% adj)* 

0.98 

Miles Between All Road calls 7,585 5,777 -24% 4,656 

Miles Between Propulsion Road 

calls 

14,539 12,792 -12% 8,596 

*Diesel buses utilized a biodiesel blend that cost an additional $0.05 per gallon. Adjusted price is that for conventional ULSD

fuel. 

• Bus Usage—The diesel buses at RB and hybrid buses at AB had essentially the same 

monthly average mileage per bus; average mileage for the AB hybrid buses was only 3% 

higher. 

• Fuel Economy—The hybrid buses at AB had on average 26% higher fuel economy than 

the diesel buses at RB. This difference ranged from 21% up to 30% during the evaluation 

period. 

• Fuel Cost per Mile—The diesel buses at RB used a biodiesel blend of 5% biodiesel (B5) 

and 95% ultra-low-sulfur diesel (ULSD) costing an average of $2.00 per gallon during the 

evaluation period. The hybrid buses at AB used only ULSD costing an average of $1.95 

per gallon during the evaluation period. The fuel cost and fuel economy combined 

resulted in a fuel cost per mile that was 22% lower (20% when adjusted for fuel price 

difference) for the hybrid buses at AB than that of the diesel buses at RB. Note: The 

energy content difference between B5 and ULSD is less than 1%. 

• Total Maintenance Cost per Mile—The hybrid buses at AB and the diesel buses at RB had 

essentially the same total maintenance cost per mile; this cost for hybrid buses was only 

2% higher. 

• Propulsion Only Maintenance Cost per Mile—The propulsion-related systems are 

transmission, nonlighting electrical (charging, cranking, and ignition), air intake, cooling, 

exhaust, fuel, engine, electric propulsion, and hydraulics. The hybrid buses at AB and the 

diesel buses at RB had exactly the same cost per mile for this category. 

• Warranty Parts Cost per Mile—These costs are not included in any other row in this table; 

they are costs incurred by manufacturers, not the fleet. Collecting all warranty costs 

(including labor) is a high priority for the final report. For the warranty parts tracked thus 

far, costs for the hybrid buses at AB were 33% higher in this category than those of the 

diesel buses at RB. 

ix
• Total Operating Cost per Mile—This category is the sum of the fuel cost per mile and the 

total maintenance cost per mile. Costs for the hybrid buses at AB were 14% lower than 

those of the diesel buses at RB (13 % when adjusted for fuel price difference). 

• Miles Between All Road Calls—The definition of road call is taken from the Federal 

Transit Administration (FTA) National Transit Database (NTD). A road call, or revenue 

vehicle system failure, is defined as a failure of an in-service bus that causes the bus to be 

replaced on its route or that causes a significant schedule delay. The hybrid buses at AB 

had a 24% lower rate of miles between all road calls than that of the diesel buses at RB. 

• Miles Between Propulsion Road Calls—The rate for hybrid buses at AB in this category 

was 12% lower than that of the diesel buses at RB. 

Emissions Testing 

Two buses were tested at NREL’s ReFUEL laboratory in Golden, Colorado, in May and June 

2005. One bus (vehicle 2899) was from the conventional diesel fleet (from Ryerson Base Depot), 

and another bus (vehicle 2709) was from the hybrid fleet (one of the 235 hybrids ordered). Both 

vehicles were tested for fuel economy and emissions performance on identical cycles. Four cycles 

were tested to determine the variability of fuel economy and emissions: Central Business District 

14 (CBD), Manhattan, the Orange County Transit Authority (OCTA), and a custom cycle made 

up of various King County runs (KCM). Each vehicle was tested multiple times on each run to 

ensure some level of statistical accuracy. Fuel economy, carbon dioxide (CO2), carbon monoxide 

(CO), nitrogen oxides (NOx), and particulate matter (PM) were measured. Differences in 

measurements between the hybrid and the conventional bus are shown in Table ES-3. 

Table ES-3. Hybrid Bus vs. Conventional Bus Test Results

Manhattan OCTA CBD KCM 

Fuel Economy (mpg, % increase) 74.6% 50.6% 48.3% 30.3% 

Fuel Consumption (gpm, % reduction) 42.9% 33.7% 32.8% 23.4% 

NOx (gpm, % reduction) 38.7% 28.6% 26.6% 17.8% 

PM (gpm, % reduction) 92.6% 50.8% 97.1% Ns 

CO (gpm, % reduction) ns 32.0% 48.0% 59.5% 

THC (gpm, % reduction) ns ns 75.2% 56.3% 

Note: gpm = gallons per mile; mpg = miles per gallon; ns = not statistically significant at 95% 

confidence level or not enough data to determine; THC = total hydrocarbon. 

Detailed information on this testing is available later in this report. It will also be available online 

in the report KCM Transit Emissions (www.nrel.gov/vehiclesandfuels/ahhps/publications.html).

Future Work 

The first six months of the evaluation, which are documented in this report, included operation of 

the hybrid buses in the downtown transit tunnel. The tunnel is now closed for conversion to light 

rail. The second six months of the evaluation will be outside the tunnel and on the street surfaces. 

The hybrid buses operated for the first six months in the tunnel in “hush mode,” which provided 

more electric propulsion operation in the tunnel (and less use of the engine) to reduce noise and 

engine emissions. Because the hybrid buses are no longer in the tunnel, the hush mode has been 

deactivated (campaign #6). This may change fuel economy data for the hybrid buses.

x
 Overview 

This interim report includes the results of an evaluation of new diesel hybrid-electric buses 

featuring a GM Allison EP

50 System parallel hybrid propulsion system and standard diesel 

articulated buses from New Flyer Industries. The buses operate in the King County Metro 

Transit (KC Metro) fleet in Seattle, Washington. The evaluation is being completed through the 

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

National Renewable Energy Laboratory (NREL), which has been tracking and evaluating new 

propulsion systems in transit buses and trucks for more than 10 years using a well-established 

and documented evaluation protocol.2

 

This report covers the first six months of the standard 12-month evaluation period. The final 

report on all results will be completed later in the year. 

Advanced Vehicle Testing Activity 

The role of AVTA is to bridge the gap between research and development (R&D) and the 

commercial availability of advanced vehicle technologies that reduce U.S. petroleum 

consumption. AVTA supports DOE’s FreedomCAR & Vehicle Technologies Program by 

evaluating the performance and durability of alternative fuel and advanced technology vehicles, 

and assessing the performance of these vehicles in fleet applications. 

The main objective of AVTA projects is to provide comprehensive, unbiased evaluations of 

advanced technologies. Data collected and analyzed include the operation, maintenance, 

performance, safety, cost, and emissions characteristics of advanced technology fleets and 

comparable conventional technology fleets operating at the same site. By comparing available 

advanced and conventional technology vehicles, AVTA evaluations help fleet owners and 

operators make informed purchasing decisions. 

The NREL AVTA team, supported by Battelle personnel, conducts medium- and heavy-duty 

vehicle evaluations. Hybrid-electric transit buses are one of the advanced vehicle choices 

available today. The evaluation team has conducted or is in the process of conducting several 

evaluations of advanced propulsion vehicles (see Table 1). For information on other evaluations, 

visit www.nrel.gov/vehiclesandfuels/fleettest. 

 

2 General Evaluation Plan, Fleet Test and Evaluation Projects, NREL/BR-540-32392, National Renewable Energy 

Laboratory, July 2002; www.nrel.gov/vehiclesandfuels/fleettest/pdfs/32392.pdf. 

1
Table 1. AVTA Heavy Vehicle Evaluations 

Fleet Location Vehicle Technology Evaluation Status 

King County 

Metro Seattle, WA 

New Flyer 60-ft 

articulated transit 

bus 

Parallel hybrid, GM-Allison 

EP

50 System (diesel) 

In progress; interim 

results reported here 

New York City 

Transit 

Manhattan, 

Brooklyn, Bronx, 

Queens, NY 

Orion VII 40-ft 

transit bus 

Series hybrid, BAE Systems 

HybriDrive propulsion system 

(diesel), two generations; 

DDC S50G CNG engines 

In progress; interim 

results reported 

IndyGo Indianapolis, IN Ebus 22-ft bus 

Series hybrid, Capstone 

MicroTurbine (diesel) Completed in 2005 

Knoxville 

Area Transit Knoxville, TN Ebus 22-ft bus 

Series hybrid, Capstone 

MicroTurbine (propane) Completed in 2005 

Norcal San Francisco, CA 

Peterbilt/378, Class 

8 truck 

Cummins Westport ISXG 

high-pressure direct injection 

LNG and diesel Completed in 2004 

Note: CNG = compressed natural gas; LNG = liquefied natural gas 

Host Site Profile—KC Metro Transit 

King County Metro Transit (KC Metro, http://transit.metrokc.gov/) operates bus-only transit 

service in the 2,134-square-mile Seattle/King County, Washington area. KC Metro operates a 

fleet of about 1,400 vehicles, standard and articulated buses, trolley buses, and streetcars that 

make a total of about 100 million trips annually. KC Metro also operates the largest publicly 

owned vanpool program in the country—more than 600 vans in the program make more than 2.9 

million trips per year. 

Like most large transit agencies, KC Metro has long been committed to supplying 

environmentally responsible transportation through several initiatives, including the following: 

• Retrofits of existing diesel bus fleet with diesel particulate filters (DPF) and the use of 

ULSD fuel. ULSD is a specially refined fuel with significantly lower sulfur content (less 

than 15 parts per million) than regular highway diesel. 

• Continued use of zero-emission electric trolley buses to supply clean and quiet 

transportation on some of the busiest routes. 

• Use of biodiesel blends at B5 levels (or 5% biodiesel by volume in diesel fuel) at two 

operating depots (Bellevue and Ryerson bases). 

• Use of new hybrid-electric articulated buses from New Flyer and GM Allison. 

KC Metro also provides bus service in King County under contract to Sound Transit. Sound 

Transit is a regional transit operator serving multiple counties. KC Metro and Sound Transit are 

cooperating to install light rail in the Seattle downtown transit tunnel, as discussed later in this 

report. 

Description of the KC Metro Hybrid Transit Bus Project 

One of the latest transit improvements introduced at KC Metro is the use of new hybrid-electric 

articulated buses to replace a fleet of dual-mode Breda articulated buses. The Breda buses were 

specially developed for use in the Seattle downtown transit tunnel (see the map in Figure 1) since 

it opened in 1990. The Breda dual-mode buses allowed zero-emission electric propulsion 

2
operation in the tunnel and diesel engine propulsion outside the tunnel or when the buses are not 

connected to the electric catenary system. 

In a catenary system, electricity-carrying wires strung above a roadway provide buses and trolley 

vehicles with electric power. Poles touch the catenary wires and provide electricity directly to the 

bus’s electric propulsion system. Many light rail systems also use a catenary system to provide 

the light rail vehicle with access to electricity and power for propulsion. 

Experiences with the Breda Dual-Mode Buses. KC Metro has been operating a fleet of 236 

Breda dual-mode buses (one is shown in Figure 2) that are at the end of their useful life—more 

than 14 years, in contrast to their 12-year expected lifetime. The 1.3-mile Seattle downtown 

tunnel was built with light rail in mind but had been used exclusively by the Breda dual-mode 

buses until the hybrid buses were placed in service. The bus tunnel was built under 3rd Avenue 

through the downtown area. This has helped to reduce congestion in downtown Seattle and helps 

KC Metro to keep buses on schedule with this exclusive right-of-way. One of the tunnel stations 

is shown in Figure 3. 

Figure 1. Seattle Downtown Transit Tunnel 

3
Figure 2. Breda Dual-Mode Bus in Yard 

Figure 3. Hybrid Bus in Seattle Downtown Tunnel at International Station 

The Breda dual-mode buses (Figure 2) were originally a unique application. This 60-foot (ft) 

articulated bus has two operating modes, a diesel engine mechanical power train, and an electric 

propulsion system powered by a catenary system. While it is in the tunnel, the bus is propelled 

by the electric drive system via the catenary poles for electricity and power. When the bus is 

outside the tunnel, the catenary poles are retracted, and the diesel engine drives a separate 

mechanical drive train to operate the bus. Other North American cities that have used a similar 

type of dual-mode bus include Vancouver, Dayton, and Boston. 

KC Metro has had a somewhat difficult and expensive experience with the Breda dual-mode 

buses. In 1988, the Breda buses were purchased for $450,000 each, and the Italian manufacturer 

4
did not provide much on-site support. Troubleshooting and maintaining the Breda buses required 

a significant amount of time and dedication on the part of the KC Metro staff. Some operating 

problems with the Breda dual-mode buses required KC Metro staff to come up with unique 

solutions so the bus’s operation would be acceptably reliable. One of the major issues was the 

unavailability of replacement parts. Some of these parts were available only through the 

manufacturer, who used small suppliers in Italy. In some cases, these parts had to be purchased a 

year in advance and in large quantities. Some parts were therefore analyzed and redesigned so 

that local U.S. shops could be used for procurements. 

In KC Metro’s experience through 2004, the last full year of the Breda fleet’s operation, about 

25% of the fleet needed to have an engine rebuilt each year and 33% needed to have a 

transmission rebuilt each year, on average. These were causing significant increases in 

maintenance costs. The engine in the Breda buses was an older DDC 6V92 diesel engine that 

needed an emissions waiver to be operated because it was not certified at the required 310-hp 

level needed for an articulated bus. 

The use of the Breda buses was discontinued in early 2005 to reduce operating and maintenance 

costs. The last date of operation for those buses was January 24, 2005; however, 59 of the buses 

were refurbished as trolley buses (electric only) and were put back in service on the catenary 

system (one is shown in Figure 4). Many of the remaining Breda dual-mode buses will be used 

for parts to help keep the 59 Breda trolley buses operating. 

Figure 4. Refurbished Breda Dual-Mode Bus to Electric-Only Trolley-Bus Operation 

Investigation of the GM Allison Hybrid. At around the same time that the transit company 

began investigating replacements for the Breda dual-mode buses, KC Metro and Sound Transit 

were putting plans together to add light rail to the downtown tunnel operation. The light rail 

operation requires a 1500 VDC catenary, and the dual-mode bus catenary is 700 VDC. If both 

the light rail and dual-mode bus fleet were to operate in the tunnel at the same time, both 

catenary systems would need to coexist in the tunnel. The company decided that there would be 

a significant benefit to removing the 700 VDC catenary system and discontinue the use of the 

dual-mode buses. 

KC Metro looked into replacing the Breda dual-mode buses not just because of their age but also 

because those buses had always been expensive to operate and maintain. New dual-mode buses 

5
were expected to be an expensive purchase; for example, Boston recently purchased new dualmode buses at an average cost of $1.6 million each. However, new dual-mode buses were no 

longer desirable because of the light rail situation in the tunnel. A replacement bus technology 

for KC Metro needed to be found that could meet the following objectives: 

1. Operate in the tunnel with low tailpipe and noise emissions, preferably without the 

catenary system 

2. Have significantly reduced operation and maintenance costs, compared with those of the 

Breda dual-mode buses 

3. Ideally, operate on routes other than the tunnel route. 

The search for a bus technology that would replace the dual-mode buses started in early 2000, 

around the same time that a division of General Motors known as Allison Electric Drives 

(www.allisontransmission.com/product/electricdrive/index.jsp) began investigating potential test 

fleets for its new hybrid bus propulsion system. After viewing a conference presentation by 

Allison, KC Metro and the company began discussions. Allison demonstrated its technology at 

KC Metro using a 40-ft bus with a trailer to simulate the operation of an articulated bus. 

The result of this testing was enough to move KC Metro to the next stage, which was to 

demonstrate the technology by purchasing one bus (number 2599). New Flyer Industries 

(www.newflyer.com) was the only builder to respond to KC Metro’s request for proposals (RFP) 

for the one hybrid articulated demonstrator bus. Bus number 2599 was received in October 2002 

and immediately put into service shadowing another in-service bus. The goal was to put a year’s 

worth of operation on the bus as soon as possible. It was loaded to 130% seated load weight and 

operated in mock revenue service (known as “shadow service”) from November 2002 through 

February 2003 for 7 days a week from noon to 8 a.m. the next morning. The bus was serviced 

between 8 a.m. and noon each day. It operated a total of 37,000 miles during the four-month 

testing period. This test was documented in a GM Allison video, “Allison Electric Drives King 

County Seattle Phases 1 & 2 Test.” 

This first hybrid articulated bus used a Cummins engine (ISL–330 hp, 8.9 liter). In December 

2002, Cummins notified KC Metro that it could not meet the emissions requirement for a model 

year 2004 bus with a 330 hp engine and pulled out of the project. Soon afterward, Caterpillar 

(CAT) expressed an interest in providing high-horsepower engines for the transit bus industry. 

CAT had a C9 (8.8 liter) diesel engine that was already certified for emissions at 330 hp for a bus 

model year 2004 engine. This was the exact size needed for the hybrid articulated bus. Therefore, 

the project team—which included New Flyer, GM Allison, and KC Metro—switched to CAT as 

the engine supplier at that time. 

Purchase of 235 New Flyer/GM Allison Hybrid Buses. In April 2003, KC Metro released an 

RFP for 265 buses—including 213 hybrid 60-ft articulated buses for KC Metro, 22 hybrid 60-ft 

articulated buses for Sound Transit, plus 30 conventional diesel 60-ft articulated buses for KC 

Metro. The RFP included only standard performance criteria, because KC Metro wanted to allow 

the manufacturer some flexibility, and the CAT engine was specified in the RFP as a powerplant 

acceptable to KC Metro just before release. A contract was signed in October 2003 with New 

Flyer that included the GM Allison electric drive and CAT C9 engine. The intent of this order 

was to replace the Breda fleet of buses entirely; the 235 new hybrid buses plus the demonstrator 

6
replaced the 236 Breda dual-mode buses. The new hybrid articulated buses cost $645,000 each. 

The diesel articulated buses, which were essentially identical to the hybrid buses without the 

electric propulsion system, cost $445,000 each. 

The new hybrid and diesel articulated buses (shown in Figures 5 and 6) were delivered to five 

operating bases at KC Metro in the following order: 

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 

KC Metro took final delivery of all the new hybrid articulated buses in early December 2004. 

Expectations of the Hybrid Bus Project. KC Metro and the hybrid bus project team expected 

significant cost savings for the hybrid buses when compared with the Breda dual-mode buses for 

operation and maintenance. The reasons that KC Metro implemented this hybrid project were as 

follows: 

• The buses are capable of tunnel operation. 

• Maintenance costs will be lower (when compared with costs for the Breda buses). 

• Fuel economy will increase (when compared with that of the Breda buses; hybrid-electric 

technology reduces emissions further when 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). 

• Intervals between brake relinings should be longer (~70,000 miles). 

• There is potential to extend the engine oil drain interval (based on oil sampling, the 

Cummins engine in the demonstration bus extended the oil drain interval from 6,000 

miles to 24,000 miles with no problems; the CAT engine was expected also to extend this 

interval, and a sampling program was planned to determine the appropriate interval; the 

company is also looking at using a synthetic engine oil). 

• The engines of the hybrid buses are expected to last the entire 12-year life of the bus. 

• The drive train is not expected to require fluid changes during its lifetime. 

Figure 5. New Flyer 60-Ft Articulated Diesel Bus at Ryerson Base 

7
Figure 6. New Flyer 60-Ft Articulated Hybrid Bus 

Project Design and Data Collection 

AVTA evaluation projects focus on using a standardized process for data collection and analysis, 

communicating results clearly, and providing an accurate and complete evaluation. The 

information in this report utilized data based on 10 selected new baseline diesel buses operating 

at Ryerson Base and 10 new hybrid buses operating at Atlantic Base as well as 10 new hybrid 

buses at South Base. The Ryerson and South Base buses went into service about the same time 

(June–July 2004) and the Atlantic Base buses went into service in around November 2004. This 

evaluation omits warranty costs from the maintenance cost analyses; the warranty costs are 

analyzed separately. 

South Base was the first depot to receive hybrid buses, and this provided an opportunity to 

evaluate the early operation of the hybrid buses at KC Metro as well as to look at the longer term 

operation of this hybrid technology for potential maintenance and reliability issues. Ryerson 

Base was the only depot with the diesel version of the new articulated buses, and the hybrid 

buses at Atlantic Base were selected for evaluation because of the similar operating cycles of 

Ryerson and Atlantic. Therefore, all cost and fuel economy comparisons in this report focus on 

the buses at the Ryerson and Atlantic bases, because they allow an apples-to-apples comparison. 

South Base was used for reference only. The evaluation strategy is discussed again in the section 

on evaluation results. 

All the articulated buses at the three depots were dispatched randomly on all routes designated 

for articulated bus operation. There were no restrictions on the diesel or hybrid articulated buses. 

The data collection activity was designed to disrupt KC Metro operations as little as possible. 

Data were sent electronically from KC Metro to Battelle for analysis. Data collected for the study 

included the following (vehicle, dates, and odometer readings were recorded for each): 

• Fluids – fuel, oil, coolant, transmission, and any others 

• Maintenance – repair history, including all work orders 

• Warranty – all warranty costs from KC Metro, New Flyer, GM Allison, and CAT 

• Road calls – from the Work Order Cost Report 

• Route assignment. 

Fleet-level summary data for the 30 new diesel and 235 new hybrid articulated buses were also 

collected, including mileage accumulations and road calls. The study was designed to include 

8
tracking of safety incidents that affected the vehicles or occurred at KC Metro facilities; 

however, no safety incidents were reported during the data collection period. 

Vehicle System Descriptions 

Table 2 summarizes the vehicle system descriptions for the diesel and hybrid articulated groups 

of buses studied. The diesel and hybrid articulated buses are essentially identical except for the 

hybrid propulsion system. The hybrid buses weigh approximately 1,100 lb more than the diesels; 

this does not make a difference in the number of passengers because there is not enough standing 

space to take the bus to the gross vehicle weight rating (GVWR). Table 3 provides some details 

about the GM Allison EP50 parallel electric propulsion system. 

Table 2. Vehicle System Descriptions

Vehicle System Diesel Hybrid Hybrid 

Operating Location Ryerson Atlantic South 

Number of Buses 10 10 10 

Bus Manufacturer and 

Model New Flyer D60LF New Flyer DE60LF New Flyer DE60LF 

Model Year 2004 2004 2004 

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

GVWR/Curb Weight 66,790 lb/43,500 lb 66,790 lb/44,600 lb 66,790 lb/44,600 lb 

Passenger Capacity 

58 Seated 

Standees Space Limited

58 Seated 

Standees Space Limited

58 Seated 

Standees Space Limited

Engine Manufacturer 

and Model Caterpillar C9 (8.8L) Caterpillar C9 (8.8L) Caterpillar C9 (8.8L) 

 Rated Horsepower 330 hp @ 2100 rpm 330 hp @ 2100 rpm 330 hp @ 2100 rpm 

 Rated Torque 1150 ft-lb @ 1400 rpm 1150 ft-lb @ 1400 rpm 1150 ft-lb @ 1400 rpm 

Emissions Equipment Engelhard DPX Engelhard DPX Engelhard DPX 

Retarder/Regenerative 

Braking Retarder Regenerative Braking Regenerative Braking 

Fuel Capacity 125 gallons 125 gallons 125 gallons 

Bus Purchase Cost $445,000 $645,000 $645,000 

Table 3. Hybrid Propulsion Systems 

Hybrid-Related System Hybrid Buses 

Manufacturer/Model GM Allison Electric Drives EP50 

Hybrid Type Parallel 

Motor/Generator 75 kW continuous, 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, 6 modules, 600 VDC 

(nominal) 

Inverter Dual Power Inverter Module (DPIM), 430-900 VDC, 

160 kW continuous 3-phase AC 

Regenerative Braking Yes 

Caterpillar C9 Engine. The diesel engine used in each of the new diesel and hybrid articulated 

buses is the Caterpillar (CAT) C9 engine (see https://ohe.cat.com/cda/layout?m=37285&x=7). 

The U.S. Environmental Protection Agency (EPA) engine emissions certification data results for 

the CAT C9 engine are shown in Table 4. 

9
Table 4. EPA Emissions Certification Levels for Model Year 2004 (g/bhp-hr)

Model Year Fuel HC + NOx CO PM Engine Family 

Certification 

Levels Diesel 2.4 15.5 0.05 All 

2004 CAT C9 Diesel 2.4 0.6 0.00 4CPXH0537H3K 

GM Allison Electric Drives EP

50. This parallel hybrid propulsion system uses the CAT engine 

primarily for highway driving, and the electric motor provides power during hill climbing, 

acceleration, and other periods of high power demand. The engine charges the energy storage 

system that supplies electricity to the motor, and energy released during deceleration is captured 

via regenerative braking and stored. Figure 7 provides some details about the operation of this 

hybrid propulsion system. Figure 8 shows a static display of the electric propulsion drive unit, 

which is designed to replace a standard transmission and to go where a standard transmission is 

usually placed. Figure 9 shows the dual-power inverter module (DPIM) with the cover open. 

This electric propulsion system has several advantages over conventional propulsion systems. It 

allows the engine to operate more efficiently and allows for regenerative braking, both of which 

increase fuel economy. For example, electric power dominates when the bus accelerates from a 

stop, eliminating the exhaust cloud typically produced by the higher transient load on the engines 

in conventional buses. The added electric power also allows the bus to accelerate faster, which is 

beneficial in city driving. 

The hybrid buses have a feature unique to KC Metro’s operation: “hush mode.” Hush mode fills 

the need for an operating mode to minimize noise and engine emissions while a bus is in 

Seattle’s downtown transit tunnel. The hybrid buses operate in an electric-only mode in the 

station areas of the tunnel and in a reduced engine power mode in between stations. 

10
The Allison EP

50 System 

Courtesy of Allison Transmission, a Division of General Motors

The energy storage system supplies electricity to the EV50 Drive’s electric motors. It stores electricity 

during normal operation and regenerative braking. 

The dual power inverter module converts electricity into alternating or direct current. This enables transfer, 

storage, and use of energy between the EV50 Drive, which uses and produces alternating current, and the 

energy storage system, which can only store direct current. 

The hybrid control modules process information from system components and driver inputs. They control 

vehicle propulsion and energy production and include diagnostic and reprogramming features. 

The engine produces power, which is used to propel the bus and to produce electricity that is stored in the 

energy storage system. 

The EV50 Drive converts electricity from the energy storage system into power to propel the bus, and it 

converts power from the engine and regenerative braking into electricity that is stored in the energy storage 

system.

Figure 7. GM Allison EP50 System Description 

KC Metro’s operation in the 1.3 mile long downtown tunnel posed a unique challenge for GM 

Allison engineers. KC Metro wanted the hybrid buses to be able to operate in the tunnel only on 

electric power, without any engine operation, to reduce tailpipe and noise emissions in the 

tunnel. The Allison engineers determined that the hybrid buses could operate in the tunnel on 

battery power only, but this would severely reduce battery life, so a compromise was needed. 

11
Figure 8. GM Allison Electric Drive Unit 

Figure 9. Dual-Power Inverter Module 

This need for low tailpipe and noise emissions and adequate battery life resulted in the 

development of “hush mode” for the hybrid buses. Hush mode operation allows the use of both 

all-electric operation and a combination of diesel and electric operation. This operation has the 

following characteristics: 

• Before entering the tunnel, the batteries are precharged to 90% state of charge or more; 

the driver pushes a button on the dashboard to start this process. 

• The driver initiates hush mode by pushing the precharge button one more time before the 

bus enters the tunnel. 

• The tunnel has two types of areas—the big, open station areas and the tunnel tubes 

between stations. 

• The hybrid buses operate in an all-electric mode while in the station areas, but while in 

the tunnel tube areas, the diesel engine is allowed to operate in reduced-power mode to 

allow for charging of the batteries (about 110 hp). 

• The timing of the switch between all-electric operation and reduced-power diesel mode is 

based on the distance traveled into the tunnel; reduced-power diesel operation starts when 

the bus’s speed reaches 15 mph or more. 

12
• While in the station area, the bus operates on battery power; however, the engine still 

rotates to operate auxiliary loads such as the air compressor; when the doors open at a 

station boarding area, the engine stops until the doors are closed again. 

The batteries were originally precharged by parking the hybrid buses in staging areas at each end 

of the tunnel until the precharge was complete, which took about 5 minutes. When light rail 

operation in the tunnel starts, precharging at the staging areas will not be possible. Allison and 

KC Metro have identified a place at each end of the tunnel where the precharge should be 

initiated to ensure that the batteries are precharged in time before entering the tunnel. In this way, 

the buses do not need to stop for the precharge, which is now accomplished en route. 

The Seattle downtown transit tunnel closed on September 24, 2005, for the addition of light rail. 

The bus catenary in the tunnel is being removed. According to the plan, the tunnel will be closed 

for two years, so bus traffic has been moved up onto 3rd Avenue. Routes were changed to 

accommodate the use of the city street instead of the tunnel. Hush mode was then deactivated in 

the hybrid buses in early October 2005 (see campaign item #6 in the next section). 

13
Facility Descriptions 

KC Metro operates seven depots for 1,420 standard, articulated, and trolley buses. This 

evaluation covers diesel and hybrid articulated buses from three of the seven depots. The new 

diesel articulated study buses operate only from Ryerson Base, and the hybrid articulated study 

buses operate from South and Atlantic bases. No special facilities or equipment are used for the 

new diesel and hybrid articulated buses. 

South Base is located in Tukwila, 10 miles south of Seattle, and serves mainly intercity routes in 

the south end and service from southern outlying suburbs into Seattle. The majority of South 

Base routes are interurban and involve service at relatively high average speeds. Approximately 

270 buses operate from South Base. Figure 10 shows the South Base maintenance and office 

building. Figure 11 shows a hybrid bus leaving South Base for peak evening service. 

Figure 10. South Base Maintenance and Office Building 

Figure 11. Hybrid Articulated Bus Leaving South Base 

The Ryerson and Atlantic bases are both within one mile of the downtown Seattle area and serve 

mainly downtown-area riders. Some of the routes move outside the Seattle city limits, but most 

are in and around downtown. The average-speed service for routes from these two bases is 

similar and lower than the average-speed service for South Base buses. Average speeds and 

routes will be discussed further in the section on evaluation results in this report. Figures 12 and 

13 show Ryerson Base. 

14
Figure 12. Ryerson Base Maintenance and Office Building 

Figure 13. Bus Parking at Ryerson Base, with Part of Seattle Skyline in Background 

Figure 14. Bus Parking at Atlantic Base with Central Base Depot in Background 

15
16

Implementation Experience 

This section discusses overall fleet-level results for mileage accumulations and significant 

campaign issues associated with the fleet of 213 KC Metro and 22 Sound Transit hybrid buses 

and 30 KC Metro diesel buses. KC Metro has treated them as standard articulated buses for 

service. No special treatment was given to the operating bases for pullout requirements. 

The hybrid and diesel articulated buses were delivered to KC Metro between May 2004 and 

early December 2004 and placed in service within a few weeks of delivery. Preparation of a bus 

only required adding KC Metro equipment, checking the bus’s operation for safety, and placing 

the bus into service. KC Metro’s experience overall has been better than expected. The bus 

operators like the new buses and do not want the old Breda dual-mode buses back. KC Metro 

reports that vendor support has also been better than expected. Caterpillar and New Flyer each 

have one technical person available in the Seattle area to help KC Metro place the new buses in 

service and keep them in service. 

As these new diesel and hybrid articulated buses were received and placed in service, the Breda 

dual-mode buses were removed from the fleet on a one-for-one basis. Figure 15 shows 

cumulative mileage for all the new hybrid and diesel buses, from June 2004 through September 

2005. As of September 2005, the hybrid buses had accumulated approximately 8.8 million miles. 

The diesel buses had accumulated 1.1 million miles through September 2005. 

0

1,000,000

2,000,000

3,000,000

4,000,000

5,000,000

6,000,000

7,000,000

8,000,000

9,000,000

Jun-04 Aug-04 Oct-04 Dec-04 Feb-05 Apr-05 Jun-05 Aug-05

Total Miles

Diesel (30 Buses) Hybrid All (235 Buses)

Figure 15. Cumulative Mileage for the Hybrid and Diesel Bus Fleet 

Figure 16 displays average monthly mileage per bus for the hybrid and diesel buses. This figure 

shows that, in general, the buses have been used at a similar rate and have averaged between 

2,500 and 3,000 monthly miles per bus. In the last three months of the data period shown, the 

diesel buses experiences lower usage as a result of engine problems, which are discussed later. 
17

0

500

1,000

1,500

2,000

2,500

3,000

3,500

Jun-04 Aug-04 Oct-04 Dec-04 Feb-05 Apr-05 Jun-05 Aug-05

Average Monthly Miles/Bus

Diesel (30 Buses) Hybrid All (235 Buses)

Figure 16. Average Monthly Mileage per Bus for entire Hybrid and Diesel Bus Fleet 

The hybrid and diesel buses have gone into service with only a few significant issues. There have 

been a few fleet defects and campaigns of warranty repairs as the manufacturers gained 

experience with the KC Metro operation and environment and addressed specific design issues 

involving the integration of the bus systems. A fleet defect, as defined in the contract between 

the transit agency and manufacturer, refers to failures of the same type on multiple buses in an 

order. A campaign is a repair, typically covered under warranty, applied to an entire order of 

buses or significant portion of one. The following list summarizes information about some of the 

significant campaigns for these buses: 

1. Axle planetary snap rings (8/2004) 

2. Allison software upgrade for issues with the inverter and CAT engine software changes 

(9/2004) 

3. Proheat auxiliary coolant heater software change (1/2005) 

4. Relocation of the DPF and change of the thermal blanket (2/2005) 

5. Allison software upgrade for additional CAT engine software changes and hush mode 

hybrid thermal protection (5/2005) 

6. Allison software upgrade for removing hush mode and a few software enhancements 

(10/2005) 

There were also minor campaigns for other bus systems, but those listed were the major changes 

to the propulsion system. April 1, 2005, was chosen as the “clean point” for the evaluation 

because the major campaigns were completed and the reliability of the buses was stabilized after 

January–February 2005. As discussed in the next section, the evaluation period for this interim 

report is April through September 2005. 
Evaluation Results (6 of 12 Months) 

The starting point for this evaluation was April 1, 2005; this report focuses on results for the first 

six months of fleet operation, through September 2005. The study buses for this evaluation are 

10 diesel articulated buses operating from Ryerson Base (Diesel RB) and 10 hybrid articulated 

buses operating from Atlantic Base (Hybrid AB). The 10 hybrid articulated buses operating from 

South Base (Hybrid SB) are included to describe early implementation experiences and for 

reference only. One of the hybrid buses at South Base had a turbocharger failure and was 

incorrectly repaired in March 2005. This caused the engine to be damaged beyond repair, so it 

was replaced in April 2005. This bus, number 2646, was removed from the evaluation. 

As discussed earlier, this evaluation focuses on comparing results for diesel buses from Ryerson 

with those for the hybrid buses from Atlantic. This was done because of the similar duty cycles 

at Ryerson and Atlantic, but not at South Base. South Base hybrid buses are included in this 

evaluation report to increase our understanding of the technology, since this was the first 

operating base to receive hybrid buses at KC Metro. The South Base hybrid buses also allow us 

to look into near-term hybrid bus maintenance and reliability issues, since they are the oldest of 

the hybrid bus fleet studied. Results for the South Base hybrid buses are shown here in gray type 

to distinguish them from other results. 

Route Descriptions 

Table 5 shows an average week’s work for articulated buses at the three bases where the study 

buses are operated—Ryerson, Atlantic, and South Base. These data are based on route 

assignments as of September 2004. As discussed earlier, average speeds are similar at Ryerson 

and Atlantic: 13.3 mph for Ryerson and 11.2 mph for Atlantic. South Base is significantly 

different, with an average speed of 19.2 mph. 

Table 5. Average Speed for Articulated Buses at Bases with Study Buses 

Base Day of Week Miles/Day Hours Avg. Speed (mph) 

Weekday 7,778 587.17 13.2 

Saturday 1,006 75.05 13.4 

Sunday 1,006 75.10 13.4 

Ryerson 

Weekly Total 40,902 3,086.00 13.3 

Weekday 4,856 415.84 11.7 

Saturday 4,644 466.25 10.0 

Sunday 1,124 130.15 8.6 

Atlantic 

Weekly Total 30,058 2,675.60 11.2 

Weekday 18,038 917.63 19.7 

Saturday 7,795 482.66 16.2 

Sunday 6,235 371.16 16.8 

South 

Weekly Total 104,220 5,441.95 19.2 

18
Bus Usage 

Among other things, bus usage is an indicator of the reliability and availability of bus service. 

The lack of usage may be an indication of downtime for maintenance or a purposeful reduction 

of planned work for the buses. 

Figure 17 shows cumulative average monthly mileage per bus for the three study groups of buses 

since they began operating; the evaluation period is shown on the chart. The general mileage 

trend for each of the three study groups of buses is slightly higher over time. The hybrid buses at 

Atlantic Base and the diesel buses at Ryerson Base have essentially the same cumulative average 

monthly mileage, around 2,800 miles per bus. The hybrid buses at South Base have a usage of 

slightly more than 4,000 miles per bus, which reflects the higher speed and route mileage duty 

cycle compared with Ryerson Base and Atlantic Base operation, which highlights why the data 

are not comparable. 

Table 6 shows average monthly mileage per bus for the study buses during the evaluation period. 

Usage for the hybrid buses at Atlantic Base and the diesel buses at Ryerson Base is 

approximately the same; that for the hybrid buses is just 3% higher. These usage rates support 

the decision to focus the evaluation on the study buses at the Ryerson and Atlantic bases. The 

hybrid buses at South Base are used in a significantly different manner, averaging 4,139 monthly 

miles per bus, which is 42% higher than the mileage for the diesel buses. 

0

500

1000

1500

2000

2500

3000

3500

4000

4500

Jul-04 Sep-04 Nov-04 Jan-05 Mar-05 May-05 Jul-05 Sep-05

Average Monthly Miles/Bus

Diesel RB Hybrid AB Hybrid SB

Evaluation Period

April - September 2005

Figure 17. Cumulative Average Monthly Miles per Bus 

19
Table 6. Monthly Mileage per Study Bus (6-month evaluation period) 

Bus Starting 

Mileage 

Ending 

Mileage 

Total 

Mileage Months Monthly Average 

Diesel RB 

2880 22,078 37,077 14,999 6 2,500 

2881 22,178 36,549 14,371 6 2,395 

2882 24,569 40,784 16,215 6 2,703 

2883 21,108 39,440 18,332 6 3,055 

2884 24,068 39,204 15,136 6 2,523 

2885 21,764 41,164 19,400 6 3,233 

2886 22,508 40,074 17,566 6 2,928 

2887 22,775 43,274 20,499 6 3,417 

2888 18,259 38,291 20,032 6 3,339 

2889 21,932 39,847 17,915 6 2,986 

174,466 60 2,908

Hybrid AB 

2780 6,791 25,323 18,532 6 3,087 

2781 7,439 26,901 19,462 6 3,244 

2782 6,243 20,381 14,138 6 2,356 

2783 7,450 25,990 18,540 6 3,090 

2784 7,626 27,005 19,379 6 3,230 

2785 4,134 22,350 18,216 6 3,036 

2786 6,615 25,852 19,237 6 3,206 

2787 6,224 20,088 13,864 6 2,311 

2788 7,111 24,682 17,571 6 2,929 

2789 5,938 26,091 20,153 6 3,359 

179,092 60 2,985

Hybrid SB 

2640 37,180 60,058 22,878 6 3,813 

2641 41,580 67,262 25,682 6 4,280 

2642 34,009 56,749 22,740 6 3,790 

2643 35,419 59,366 23,947 6 3,991 

2644 31,062 55,692 24,630 6 4,105 

2645 36,879 61,813 24,934 6 4,156 

2647 35,343 63,950 28,607 6 4,768 

2648 36,025 61,255 25,230 6 4,205 

2649 36,548 61,407 24,859 6 4,143 

223,507 54 4,139

Fuel Economy and Cost 

KC Metro buses use ULSD fuel, which has a sulfur content less than 15 ppm. In addition to 

ULSD, Ryerson Base diesel buses use a 5% biodiesel blended with ULSD (B5), which has 

virtually the same energy content (<1% difference). Table 7 summarizes fuel economy results for 

the 30 study buses. The hybrid buses from Atlantic Base had a 26% higher fuel economy on 

average compared with that of diesel buses at Ryerson Base. This comparison is the most 

applicable because of their similar usage and duty cycles, as discussed earlier. The South Base 

hybrid buses have operated in a higher average speed duty cycle and have a fuel economy that is 

47% higher on average than that of the diesel buses at Ryerson Base and 17% higher than that of 

the other hybrid buses at Atlantic Base. 

20
Figure 18 shows average fuel economies for the Ryerson and Atlantic study groups since the 

beginning of their operation at KC Metro (the evaluation period is indicated). The diesel buses at 

Ryerson Base had an average fuel economy that started at around 2.2 mpg and went up to around 

2.5 mpg from August to October 2004. This increase was accomplished through a software 

change in the CAT engine. The diesel buses have operated at around 2.5 mpg since the first three 

months of operation. All of the CAT engines (diesel and hybrid) received this software update; 

however, only the diesel buses showed a significant increase in fuel economy. 

Table 7. Fuel Use and Economy (6-month evaluation period) 

Bus Mileage 

(Fuel Base) 

Gallons 

Consumed

Miles per 

Gallon 

Diesel RB 

2880 14,901 5,688 2.62 

2881 13,354 5,583 2.39 

2882 15,166 5,771 2.63 

2883 18,255 7,158 2.55 

2884 14,716 6,029 2.44 

2885 19,082 7,380 2.59 

2886 16,748 6,626 2.53 

2887 20,008 7,973 2.51 

2888 19,177 7,152 2.68 

2889 16,861 6,527 2.58 

168,268 65,886 2.55 

Hybrid AB 

2780 17,228 5,431 3.17 

2781 18,825 5,871 3.21 

2782 13,494 4,285 3.15 

2783 18,094 5,849 3.09 

2784 19,070 5,741 3.32 

2785 17,406 5,354 3.25 

2786 17,662 5,394 3.21 

2787 12,865 3,974 3.24 

2788 16,608 5,152 3.22 

2789 19,560 6,096 3.21 

170,812 53,248 3.21 

Hybrid SB 

2640 22,498 6,131 3.67 

2641 20,932 5,490 3.81 

2642 21,285 5,939 3.58 

2643 21,738 5,681 3.83 

2644 23,786 6,443 3.69 

2645 21,570 6,023 3.58 

2647 27,625 7,223 3.82 

2648 22,148 5,575 3.97 

2649 22,183 5,813 3.82 

203,765 54,318 3.75 

21
0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

Jul-04 Sep-04 Nov-04 Jan-05 Mar-05 May-05 Jul-05 Sep-05

Miles per Gallon (MPG)

Diesel RB Hybrid AB

Evaluation Period

April - September 2005

RB Avg. 2.55 mpg

AB Avg. 3.21 mpg

AB/RB +26%

Figure 18. Average Fuel Economy (mpg) 

For a controlled, detailed, direct fuel economy comparison, KC Metro recommended Route 120 

(12.9 average mph) operated from Ryerson Base and Route 106 (12.6 average mph) operated 

from Atlantic Base. For the study buses at these two operating bases, route and fuel consumption 

data were used to compare fuel economies calculated from operation on the two bus routes. The 

results show a 19% higher fuel economy for the hybrid buses, on average. Table 8 shows the 

results of this comparison for the evaluation period. 

Table 8. Fuel Economy Comparison for Route 120 and Route 106 (6-month evaluation period) 

Month 

RB Diesels 

Route 120 

Fuel Economy 

AB Hybrids 

Route 106 

Fuel Economy 

Percent Difference 

(Hybrid/Diesel) 

April-2005 2.54 3.08 21% 

May-2005 2.65 3.02 14% 

June-2005 2.62 3.19 22% 

July-2005 2.59 3.07 19% 

August-2005 2.48 2.91 17% 

September-2005 2.55 3.19 25% 

Average 2.57 3.07 19% 

Actual fuel costs during the evaluation period were $2.00 per gallon on average for the 5% 

biodiesel blend fuel at Ryerson Base and $1.95 per gallon for Atlantic and South Bases. The use 

of the B5 blend at Ryerson Base was not a technical requirement for the diesel buses but it was 

used 100% of the time at that depot; therefore, results are given for actual costs incurred and 

adjusted costs, as if the diesel vehicles at RB used the same $1.95 per gallon fuel. Costs per mile 

for each of the three study bus groups are as follows: 

• Diesel RB = $0.78 per mile actual (adjusted = $0.76 per mile if same fuel as hybrid) 

• Hybrid AB = $0.61 per mile 

• Hybrid SB = $0.52 per mile. 

22
This translates to an actual cost per mile 22% lower for the Atlantic Base hybrid buses when 

compared with the Ryerson Base diesel buses, or 20% lower when adjusted for the fuel 

discrepancy. 

Maintenance Cost Analysis 

The maintenance cost analysis in this section focuses on the evaluation period (April 2005 

through September 2005); however, some of the analyses compare results from the time that the 

buses started operations. The data period is clearly indicated for each figure in this section. 

Warranty costs are not included in this section but are analyzed separately later. All work orders 

since the beginning of the operation of the study buses were collected and analyzed for this 

evaluation. The labor rate for maintenance was kept at a constant $50 per hour, and this does not 

reflect an average rate at KC Metro. This section first discusses total maintenance costs and then 

maintenance costs broken down by bus system. 

Total Maintenance Costs. Total maintenance costs include the actual cost of parts and hourly 

labor costs at $50 per hour and do not include warranty costs. Cost per mile is calculated as 

follows: Cost per mile = [(labor hours * 50) + parts cost] / mileage 

Table 9 shows total maintenance costs during the evaluation period for the diesel and hybrid 

study buses at the two depots. The two study groups of buses essentially had the same total 

maintenance cost for the evaluation period. South Base depot results are shown in Table 9 for 

reference only. 

Of the two higher cost-per-mile buses in the Ryerson diesel study group, bus 2880 was out of 

service for much of June 2005 for repairs of the starter and engine. This bus also needed 

significant repair of the air-conditioning equipment in September 2005 and was involved in an 

accident near the end of the month. The drive axle and differential of bus 2884, the other higher 

cost-per-mile bus, also had significant repairs, as did the air-conditioning, like bus 2880. 

At Atlantic Base, the two highest cost-per-mile hybrid buses were numbers 2782 and 2787. Bus 

2782 was out of service for most of June 2005 to repair damage from vandalism inside the bus 

and for a preventive maintenance inspection. Significant engine repairs and troubleshooting were 

completed during July through September 2005, for a total of 62.5 hours of work. Bus 2787 had 

maintenance work done on the drive axle and suspension as a result of an accident in late March 

2005 and repairs done in early April 2005. The other significant repair for this bus was for a 

problem with charging the standard lead-acid (12 V/24 V) batteries and alternator. 

23
Table 9. Total Maintenance Costs (6-month evaluation period)

Bus Mileage Parts 

Cost ($) 

Labor 

Hours 

Cost per 

Mile ($) 

Diesel RB 

2880 14,999 2,040.88 134.7 0.59 

2881 14,372 952.22 115.5 0.47 

2882 16,215 1,452.25 124.5 0.47 

2883 18,332 1,122.30 94.5 0.32 

2884 15,136 2,301.57 148.0 0.64 

2885 19,399 2,753.47 117.0 0.44 

2886 17,566 1,809.28 99.5 0.39 

2887 20,500 1,463.39 121.0 0.37 

2888 20,032 3,749.89 128.5 0.51 

2889 17,915 1,168.50 161.0 0.52 

Avg. 17,447 1,881.38 124.4 0.46

Hybrid AB 

2780 18,532 906.28 92.5 0.30 

2781 19,462 1,687.85 143.5 0.46 

2782 14,138 1,265.94 181.5 0.73 

2783 18,540 1,367.55 128.0 0.42 

2784 19,379 1,444.12 131.5 0.41 

2785 18,216 3,147.04 141.8 0.56 

2786 19,237 2,122.34 124.0 0.43 

2787 13,864 1,913.13 133.5 0.62 

2788 17,571 1,721.84 137.3 0.49 

2789 20,153 1,329.52 117.0 0.36 

Avg. 17,909 1,690.56 133.1 0.47

Hybrid SB 

2640 22,878 1,158.97 245.3 0.59 

2641 25,682 2,743.72 201.0 0.50 

2642 22,740 1,079.41 201.0 0.49 

2643 23,947 1,636.19 152.5 0.39 

2644 24,630 2,139.81 205.0 0.50 

2645 24,934 1,238.51 186.5 0.42 

2647 28,606 1,820.83 191.0 0.40 

2648 25,231 2,095.81 182.0 0.44 

2649 24,859 1,282.96 165.0 0.38 

Avg. 24,831 1,688.47 192.1 0.46

Figure 19 shows cumulative total maintenance costs for the Ryerson and Atlantic study bus 

groups from the start of operation through September 2005. In general, the Ryerson Base diesel 

buses and Atlantic Base hybrid buses have had the same total maintenance costs for most of the 

period shown, though these costs for the hybrid buses were slightly higher. 

24
0.000

0.100

0.200

0.300

0.400

0.500

0.600

Jul-04 Sep-04 Nov-04 Jan-05 Mar-05 May-05 Jul-05 Sep-05

Maintenance Cost ($) per Mile

Diesel RB Hybrid AB

Evaluation Period

April - September 2005

Figure 19. Cumulative Maintenance Cost per Mile (all data)

Maintenance Cost Breakdown by System. Table 10 shows maintenance costs by vehicle 

system and bus study group. The vehicle systems shown in the table include the following: 

• Air system, general 

• Axles, wheels, and drive shaft 

• Brakes—Excludes regenerative braking for the hybrids, which is included in propulsionrelated systems 

• Cab, body, and accessories—Includes body repairs following accidents, glass, and paint; 

cab and sheet metal repairs on seats and doors; and accessory repairs such as 

hubodometers and radios 

• Frame, steering, and suspension—Includes steering and suspension repairs 

• Heating, ventilation, and air-conditioning (HVAC) 

• Lighting 

• Preventive maintenance inspections (PMI)—Labor for inspections during preventive 

maintenance 

• Propulsion-related systems—Repairs for exhaust, fuel, and engine; electric motors, 

traction batteries, and propulsion control; nonlighting electrical (charging, cranking, and 

ignition); air intake, cooling, hydraulics, and transmission 

• Tires 

The four highest-cost repair categories for all three bus study groups were cab, body, and 

accessories; propulsion-related; HVAC; and PMI. There were no major brake repairs in the three 

study groups. 

25
Table 10. Breakdown of Vehicle System Maintenance Cost per Mile (6-month evaluation period)

Diesel Ryerson Hybrid Atlantic Hybrid South 

System 

(in order of cost) Cost per 

Mile ($) 

Percent of 

Total (%) 

Cost per 

Mile ($) 

Percent of 

Total (%) 

Cost per 

Mile ($) 

Percent 

of Total 

(%) 

Cab, Body, and 

Accessories 0.16 35 0.19 40 0.14 31 

Propulsion-Related 0.14 31 0.14 30 0.16 35 

HVAC 0.07 15 0.04 9 0.05 11 

PMI 0.05 11 0.06 13 0.05 11 

Frame, Steering, and 

Suspension 0.01 2 0.02 4 0.01 2 

Lighting 0.01 2 0.01 2 0.00 0 

Air, General 0.01 2 0.00 0 0.01 2 

Axles, Wheels, and 

Drive Shaft 0.01 2 0.00 0 0.02 4 

Brakes 0.00 0 0.01 2 0.01 2 

Tires 0.00 0 0.00 0 0.00 0 

Articulation Joint 0.00 0 0.00 0 0.01 2 

Total 0.46 100 0.47 100 0.46 100 

Cab, Body, and Accessories Maintenance Costs. The maintenance costs associated with these 

systems are shown by bus study group. The following describes each subsystem in this category. 

• Body exterior—Includes all body panels and compartment doors, as well as reflectors 

• Destination signs 

• Cleaning—All cleaning activities inside and outside the bus 

• Door and interlock—Includes anything that has to do with the doors and interlock system 

except the brakes 

• Farebox 

• Fire extinguisher 

• General interior and seats 

• Horn 

• Mirrors—All inside and outside mirrors 

• Radio 

• Supplies and expendable items—Includes painting supplies, tools, wipes, eyeglasses, and 

coveralls assigned to a bus 

• Wheelchair ramp—Includes all repairs for the wheelchair ramp system except hydraulics 

• Windshield wipers—Includes the wipers, motors, and washer systems 

The maintenance costs for the hybrid buses at Atlantic Base in this category were slightly higher 

than those for the diesel buses, and the costs for the hybrid buses at South Base were slightly 

lower than those of the diesel buses. The highest-cost subsystems in this category were cleaning, 

farebox, body-exterior, and general interior and seats. 

26
Propulsion-Related Maintenance Costs. The propulsion-related vehicle systems include the 

exhaust, fuel, engine, electric propulsion, air intake, cooling, nonlighting electrical (charging, 

cranking, and ignition), transmission, and hydraulic systems. The cooling system also includes 

an auxiliary coolant heater to ensure that the engine coolant warms up quickly. 

Table 11 shows the total propulsion-related maintenance costs and lists each of the system 

maintenance costs that make up propulsion-related maintenance for the three study groups of 

buses. All comparison calculations are for the hybrid compared with the diesel buses from 

Ryerson Base. 

The propulsion-related maintenance cost per mile for the Atlantic Base hybrid buses is the same 

as that for the Ryerson Base diesel buses. The cost per mile for the South Base hybrid buses is 

14% higher than that of the diesel buses. The following is a breakdown of propulsion-related 

maintenance costs during the evaluation period: 

• Air intake system maintenance—These costs were very low and similar for the two study 

groups. 

• Cooling system maintenance—These costs were lower for the hybrid bus study group 

than for the diesel buses. Two diesel buses had significant auxiliary coolant heater 

repairs. 

• Electric propulsion maintenance (reference only)—When comparing the two depots with 

hybrids (which have different duty cycles), costs were lower in this category for the 

Atlantic Base hybrid buses, and those of the South Base hybrid buses were higher at 

$0.05 per mile. The higher cost for the South Base hybrid buses was caused by a high 

number of labor hours spent to troubleshoot problems with the propulsion system 

(perhaps because SB was the first to receive hybrids). For two of the hybrid buses in the 

South Base study group, labor hours were significant and included investigating a 

problem with the cooling lines for the DPIM. Four DPIMs were replaced in the South 

Base hybrid buses, and one was replaced in the Atlantic Base hybrid buses. No battery 

replacements were reported since the beginning of operation for any of the hybrid buses. 

• Engine system maintenance—For both the AB and RB groups of buses, costs for the 

engine system were similar. 

• Exhaust system maintenance—The repair costs for the diesel buses were the highest in 

this category; however, the costs themselves were low ($0.01 per mile). 

• Fuel system maintenance—The maintenance costs for this system were essentially the 

same for study buses in both the RB and AB depots. 

• Hydraulic system maintenance—Costs for this system were low and the same for both 

study groups. Only costs for hydraulic fluid replacements for scheduled maintenance 

were reported for both study groups. 

• Nonlighting electrical systems maintenance—The costs for this category for the two 

study groups were essentially the same; those for the hybrid buses at Atlantic Base were 

only slightly higher than those in the other study group. 

• Transmission maintenance—These costs were very low and similar for both groups. 

27
Table 11. Propulsion-Related Maintenance Cost by System (6-month evaluation period) 

Maintenance System 

Costs 

Diesel 

Ryerson 

Hybrid 

Atlantic 

Hybrid South 

Mileage Base 174,466 179,092 233,507 

Total Propulsion-Related Systems (Roll-Up) 

Parts Cost ($) 9,292.47 5,656.96 4,922.93 

Labor Hours 310.5 374.3 606.7 

Total Cost per Mile ($) 0.14 0.14 0.16 

Exhaust System Repairs 

Parts Cost ($) 121.10 0.00 62.89 

Labor Hours 14.0 0.0 10.5 

Total Cost per Mile ($) 0.01 0.00 0.00 

Fuel System Repairs 

Parts Cost ($) 473.24 507.25 450.28 

Labor Hours 7.0 13.8 16.0 

Total Cost per Mile ($) 0.01 0.01 0.01 

Engine System Repairs 

Parts Cost ($) 1,829.09 1,770.62 1,987.02 

Labor Hours 175.0 167.0 182.5 

Total Cost per Mile ($) 0.06 0.06 0.05 

Electric Motor, Generator, and Battery Repairs 

Parts Cost ($) 534.45 10.95 

Labor Hours 36.0 246.7 

Total Cost per Mile ($) 0.01 0.05 

Nonlighting Electrical System Repairs (General Electrical, Charging, 

Cranking, Ignition) 

Parts Cost ($) 959.96 817.15 517.86 

Labor Hours 42.5 92.5 73.5 

Total Cost per Mile ($) 0.02 0.03 0.02 

Air Intake System Repairs 

Parts Cost ($) 341.85 95.18 146.25 

Labor Hours 3.0 2.0 3.0 

Total Cost per Mile ($) 0.00 0.00 0.00 

Cooling System Repairs 

Parts Cost ($) 3,823.58 165.11 154.10 

Labor Hours 61.0 52.0 70.0 

Total Cost per Mile ($) 0.04 0.02 0.02 

Transmission Repairs 

Parts Cost ($) 0.76 62.10 58.99 

Labor Hours 8.0 11.0 4.5 

Total Cost per Mile ($) 0.00 0.00 0.00 

Hydraulic Repairs 

Parts Cost ($) 1,742.89 1,705.10 1,534.59 

Labor Hours 0.0 0.0 0.0 

Total Cost per Mile ($) 0.01 0.01 0.01 

Figure 20 shows propulsion-related maintenance costs for the Ryerson and Atlantic study bus 

groups for the evaluation period. Costs per mile for the diesel buses at Ryerson Base start out 

higher and then settle down to end at around $0.15 per mile. Early problems had to do with the 

auxiliary coolant heater. Later problems for the diesel buses had to do with the engine, 

turbocharger, and DPF. The costs for the hybrid buses at Atlantic Base started low and then 

jumped in August 2005. This was caused by problems with the engine, standard batteries, and 

28
voltage regulator for the alternator. Costs for the Atlantic Base hybrid buses ended at the same 

level as those of the diesel buses. 

0.00

0.05

0.10

0.15

0.20

0.25

0.30

Apr-05 May-05 Jun-05 Jul-05 Aug-05 Sep-05

Cost ($) / Mile

Diesel RB Hybrid AB

Figure 20. Propulsion-Related Maintenance Cost per Mile (6-month evaluation period)

HVAC Maintenance Costs. This category includes all maintenance actions for heating and 

ventilation and the air-conditioning system. The majority of the costs in this category are related 

to the air-conditioning system. Maintenance costs for the study groups of buses are shown in 

Table 12. 

These costs were lowest for the hybrid buses at Atlantic Base. The parts costs for all the study 

groups were for major repairs for the air-conditioning system. For all three study groups of 

buses, troubleshooting work orders for the heating system were most likely the result of an issue 

with the auxiliary coolant heater; however, the work order descriptions were not specific enough 

to indicate the root cause of the “no heat” problem. 

 Table 12. HVAC System Maintenance Costs (6-month evaluation period)

Study 

Group Mileage Parts Cost ($) 

Labor 

Hours 

Cost per 

Mile ($) 

Diesel RB 174,466 4,941.81 158.5 0.07 

Hybrid AB 179,092 2,775.62 84.3 0.04 

Hybrid SB 223,507 3,489.31 158.0 0.05 

PMI Maintenance Costs. This category only includes labor hours for inspections of multiple 

bus systems during preventive maintenance. As shown in Table 13, the maintenance cost per 

mile for this category was essentially the same for the study groups of buses. This indicates that, 

in general, the three study groups featured similar preventive maintenance practices even though 

they operate from three separate locations. 

29
Table 13. PMI Maintenance Costs (6-month evaluation period)

Study 

Group Mileage Parts Cost ($) 

Labor 

Hours 

Cost per 

Mile ($) 

Diesel RB 174,466 0.00 173.5 0.05 

Hybrid AB 179,092 0.00 218.0 0.06 

Hybrid SB 223,507 0.00 228.0 0.05 

Warranty Costs. Warranty costs are maintenance costs covered by the manufacturer(s) of the 

vehicle, such as providing parts at no cost, and for costs that were incurred by the fleet and 

reimbursed. There is a one- to two-year warranty period for many systems on the buses; the 

warranty period for some systems is determined by mileage or calendar time. Most transit bus 

operators have a fleet defect clause that covers maintenance beyond the standard warranty 

period. 

The maintenance analysis in the previous section does not include any of the costs presented 

here. The KC Metro maintenance system tracks most part replacements, including those 

provided by the manufacturers. The cost summary in Table 14 shows warranty parts costs 

determined on the basis of parts replaced in the KC Metro maintenance tracking system. Parts 

costs that were listed as $0.01 (covered by warranty) were replaced with the actual or estimated 

cost of the parts listed. These parts costs were summed to better indicate where costs might be 

when warranty period ended. This analysis is not yet complete and will be a high priority for the 

final report. Additional work in determining the warranty activities that are one-time charges and 

those that are recurring will also be in the final report of this evaluation. 

For the evaluation period, Table 14 shows that the lowest warranty parts costs were for the diesel 

buses, followed by those for the hybrid buses at Atlantic Base. For the diesel buses, the highest 

warranty costs were for exhaust (one DPF replacement at $5,700), fuel (one fuel pump at 

$1,200), and engine (one turbocharger at $1,900). The highest warranty costs in the nonlighting 

electrical category were for the hybrid buses at Atlantic Base. These costs were incurred for 

campaign activities for the multiplexing modules and the alternator. One dual power inverter 

module was also replaced (at an estimated cost of $2,500). There were several high-cost 

warranty activities for the South Base hybrid buses. They included significant repairs to the airconditioning systems of two buses. The nonlighting electrical warranty costs were mostly 

campaigns for the multiplexing modules, voltage regulator, and alternator. Costs for these buses 

included one DPF replacement ($5,700) and one fuel pump ($1,200). The engine warranty parts 

costs included the replacement of three turbochargers (at $1,900 each) and four exhaust brakes 

(at $646 each). Four DPIM replacements (estimated at $2,500 each) were also required for the 

hybrid buses. 

Figure 21 shows average monthly warranty parts cost per bus from the beginning of operation 

through September 2005. This chart shows that the high warranty parts costs for the diesel buses 

early on was caused mostly by DPF replacements (for a manufacturing defect) and early 

campaigns. The period from November 2004 through June 2005 showed relatively low warranty 

parts costs per bus. Costs for the Atlantic Base hybrid buses jumped in July 2005 because of the 

campaigns for the multiplexing modules and alternators. The costs for the diesel buses were very 

low until September 2005, when one bus experienced a turbocharger and DPF failure and 

subsequent replacements. 

30
Table 14. Warranty Parts Costs by Bus System (6-month evaluation period)

System Diesel RB Hybrid AB Hybrid SB 

HVAC 238.56 344.80 1,422.13 

Cab, Body, Accessories 852.25 0.00 1.81 

Air, General 0.00 70.86 70.86 

Suspension 0.00 50.43 0.00 

Axles 224.00 0.00 873.00 

Steering 0.00 0.00 32.43 

Transmission 0.00 0.00 6.21 

Nonlighting Electrical 8.00 11,789.32 7,952.87 

Cooling 50.00 150.00 129.56 

Exhaust 5,793.93 0.00 6,010.15 

Fuel 1,214.03 0.00 1,219.09 

Engine 1,914.03 143.54 9,689.69 

Electric Propulsion 0.00 2,500.00 10,000.00 

Articulation Joint 20.00 10.00 15.00 

Total 10,319.86 15,058.95 37,422.80 

Potential Cost per Mile ($)* 0.06 0.08 0.17 

*Cost per mile if these costs were included in the total maintenance costs discussed 

above. 

0.00

500.00

1000.00

1500.00

2000.00

2500.00

Jul-04 Sep-04 Nov-04 Jan-05 Mar-05 May-05 Jul-05 Sep-05

Warranty Part Cost ($) per Bus

Diesel RB Hybrid AB

Evaluation Period

April - September 2005

Figure 21. Monthly Warranty Parts Cost per Study Bus ($) 

31
Road Call Analysis 

A road call (RC) or revenue vehicle system failure (so named for the National Transit Database3) 

is defined as a failure of an in-service bus that causes the bus to be replaced en route or results in 

a significant schedule delay. If the problem can be repaired during a layover and the schedule is 

not affected, this is not considered a RC. This analysis includes only RCs that were caused by 

“chargeable” failures. Chargeable RCs involve systems that can physically disable the bus from 

operating en route, such as interlocks (doors), engine, etc. The analysis does not include RCs for 

things such as radios or destination signs. 

Figure 22 shows cumulative miles between road calls (MBRC) and Table 15 breaks down the 

RCs by vehicle system for all three study groups for the evaluation period. There are two lines 

for each study group; one is for the MBRC for all RCs and the other is for the MBRC only for 

propulsion-related RCs. The MBRC for all RCs for the Ryerson and Atlantic study groups of 

buses were nearly the same by the end of the evaluation period—between 5,000 and 7,000 

MBRC—and the highest were for the diesel buses. The propulsion-related MBRC for the 

Atlantic Base hybrid buses was 12,792, and for the diesel buses it was 14,539, or 12% higher. 

0

5000

10000

15000

20000

25000

30000

35000

Apr-05 May-05 Jun-05 Jul-05 Aug-05 Sep-05

Miles Between Roadcalls (MBRC)

Diesel RB Cumulative MBRC Diesel RB Cumulative Propulsion MBRC

Hybrid AB Cumulative MBRC Hybrid AB Cumulative Propulsion MBRC

Figure 22. Total and Propulsion-Only Cumulative MBRC (6-month evaluation period)

In Table 15, the top three categories of most RCs for diesel buses were for engine, doors and 

interlock, and cooling problems (in that order). The top three categories of most RCs for hybrid 

buses at AB were doors and interlock, engine, and a tie for third (lighting, cooling, fuel, and 

wheelchair ramp). The top three categories of most RCs for the hybrid buses at SB were the 

 

3

 Revenue vehicle system failures are defined for the FTA’s National Transit Database in the Reporting Manual 

Resource Module, which can be found at 

www.ntdprogram.com/NTD/ReportingManual/2005/Annual/PDFFiles/2005%20Resource%20Module.pdf. 

32
electric propulsion, engine, and doors and interlock. The RCs for electric propulsion were related 

to early problems with the cooling of the DPIM. 

 Table 15. Summary of Road Calls by System (6-month evaluation period)

Diesel RB Hybrid AB Hybrid SB 

System 

Road 

Calls 

Percent 

(%) 

Road 

Calls 

Percent 

(%) 

Road 

Calls 

Percent 

(%) 

HVAC 0 0 1 3 5 10 

Doors and Interlock 4 17 6 20 6 13 

Wipers 0 0 1 3 0 0 

Air, General 0 0 0 0 1 2 

Brakes 1 4 2 6 2 4 

Steering 1 4 1 3 0 0 

Suspension 0 0 0 0 1 2 

Axles 0 0 0 0 1 2 

Transmission* 1 4 0 0 0 0 

Nonlighting Electrical* 0 0 2 6 4 8 

Lighting 2 10 3 10 1 2 

Cooling* 3 13 3 10 2 4 

Exhaust* 1 4 0 0 0 0 

Fuel* 0 0 3 10 1 2 

Engine* 7 30 5 16 7 15 

Electric Propulsion* 0 0 1 3 12 25 

Wheelchair Ramp 2 10 3 10 3 7 

Articulation Joint 1 4 0 0 2 4 

Total 23 100 31 100 48 100 

All MBRC 7,585 5,777 4,656 

Propulsion MBRC 14,539 12,792 8,596 

*=Propulsion System Related Groups

Table 16 summarizes fuel and maintenance costs per mile for the study groups. The table shows 

the costs for each bus and the group average. The total cost for the hybrid buses at Atlantic Base 

were 14% lower than that for the diesel buses (13% when adjusted for fuel discrepancy). 

33
Table 16. Summary of Costs per Mile

Bus 

Fuel Cost per 

Mile ($) 

Maintenance 

Cost per 

Mile ($) 

Total Cost per 

Mile ($) 

Potential 

Warranty Part 

Cost per Mile 

($) 

Diesel RB

2880 0.76 0.59 1.35 

2881 0.84 0.47 1.31 

2882 0.76 0.47 1.23 

2883 0.78 0.32 1.10 

2884 0.82 0.64 1.46 

2885 0.77 0.44 1.21 

2886 0.79 0.39 1.18 

2887 0.80 0.37 1.17 

2888 0.75 0.51 1.26 

2889 0.78 0.52 1.30 

Avg. 

0.78 

(0.76 adjusted) 0.46 

1.25 

(1.23 adjusted) 0.06 

Hybrid AB

2780 0.62 0.30 0.92 

2781 0.61 0.46 1.07 

2782 0.62 0.73 1.35 

2783 0.63 0.42 1.05 

2784 0.59 0.41 1.00 

2785 0.60 0.56 1.16 

2786 0.61 0.43 1.04 

2787 0.60 0.62 1.22 

2788 0.61 0.49 1.10 

2789 0.61 0.36 0.97 

Avg. 0.61 0.47 1.07 0.08 

Hybrid SB

2640 0.53 0.59 1.12 

2641 0.51 0.50 1.01 

2642 0.54 0.49 1.03 

2643 0.51 0.39 0.90 

2644 0.53 0.50 1.03 

2645 0.54 0.42 0.96 

2647 0.51 0.40 0.91 

2648 0.49 0.44 0.93 

2649 0.51 0.38 0.89 

Avg. 0.52 0.46 0.98 0.17 

Laboratory Emissions Testing 

Tests were performed on one hybrid bus (of the 235) and one conventional bus (of the 30) during 

May and June 2005 to determine the emissions and fuel economy benefits of the hybrid-electric 

powertrain being evaluated on site in King County. The tests were conducted over four driving 

cycles: Central Business District (CBD), Orange County (OCTA), Manhattan, and a custom test 

cycle developed from in-use data on the King County Metro (KCM) fleet’s operation. In order to 

evaluate the effects of additional engine and vehicle loading due to grade, select cycles were 

34
repeated with and without this added load. Vehicle exhaust emissions, fuel consumption, and 

state of charge of the energy storage system were measured for repeated test conditions. 

The vehicles were tested at the ReFUEL laboratory, which is operated by NREL and located in 

Denver, Colorado. The laboratory includes a heavy-duty vehicle (chassis) test cell and an engine 

dynamometer test cell with emissions measurement capability. Regulated emissions 

measurements are performed using procedures consistent with the Code of Federal Regulations 

(CFR) title 40, section 86, subpart N. Instrumentation and sensors at the laboratory are 

maintained with National Institute of Standards and 

Technology (NIST)-traceable calibration. Test procedures, 

calibrations, and measurement accuracies are maintained to 

meet requirements outlined in the current CFR title 40, 

section 86, subpart N. 

The test vehicles were installed on the chassis dynamometer, 

shown in Figure 23. All sensors shown were monitored and 

recorded continuously by the ReFUEL data acquisition 

system throughout each test cycle run, unless otherwise 

noted. Detailed results of this testing are included in the 

report, KCM Transit Emissions, which will be available at 

www.nrel.gov/vehiclesandfuels/ahhps/publications.html.

Figure 23. Chassis Cell with Test 

Fuel economy results for the buses are shown in Table 17. Emissions results (for NOx, PM, CO, 

and CO2) are shown in Table 18. 

Table 17. Fuel Economy of Buses on Various Cycles

 Manhattan OCTA CBD KCM 

KCM, 

no grade

Conventional Bus Fuel Economy (mpg) 1.46 2.15 2.19 2.90 3.03 

Hybrid Bus Fuel Economy (mpg) 2.56 3.24 3.25 3.78 3.98 

Fuel Economy Increase with Hybrid Bus (mpg) 1.09 1.09 1.06 0.88 0.95 

Table 18. Average Values for Emission Results of Buses on Specified Cycles*

Manhattan OCTA CBD KCM 

 Diesel Hybrid Diesel Hybrid Diesel Hybrid Diesel Hybrid 

NOx 

(gram/mile) 29.58 18.12 18.91 13.51 19.67 14.44 14.74 12.11 

PM 

(gram/mile) 0.380 .003 0.050 0.024 0.101 0.003 .108 0.187 

CO 

(gram/mile) 3.13 2.81 2.29 1.55 1.77 1.55 0.66 0.27 

THC 

(gram/mile) 0.04 0.05 0.03 0.03 0.12 0.03 0.04 0.02 

CO2 

(gram/mile) 6714 3771 4579 3001 4587 2991 3446 2614 

*Average of at least three runs; see detailed report for measured variation between runs. 

35
Future Work

All the new diesel and hybrid articulated buses from New Flyer have been delivered and have 

been in service since at least December 2004. This interim evaluation report provides results 

from the first six of a 12-month evaluation period. The first six months covered in this report 

included operation of the hybrid buses in the downtown transit tunnel. The tunnel is now closed, 

and the next six months of operation will be outside the transit tunnel. The “hush mode” feature 

of the hybrid buses has been deactivated via software. The final report will cover all 12 months 

of the evaluation, and its completion and release are planned for fall 2006. 

36
Contacts 

U.S. Department of Energy 

Lee Slezak 

Manager, Advanced Vehicle Testing Activity 

Phone: 202-586-2335 

E-mail: lee.slezak@ee.doe.gov 

National Renewable Energy Laboratory 

Kevin Walkowicz 

Senior Project Engineer 

Phone: 303-275-4492 

E-mail: kevin_walkowicz@nrel.gov 

King County Metro Transit 

Todd Gibbs 

Senior Program Administrator 

Phone: 206-684-2878 

E-mail: todd.gibbs@metrokc.gov 

GM Allison Electric Drives 

Peter Chiang 

Vehicle/Field Engineering 

Phone: 317-915-2748 

E-mail: peter.chiang@gm.com 

New Flyer Industries 

G. Paul Zanetel 

Chief Technical Advisor 

Phone: 204-982-8180 

E-mail: paul_zanetel@newflyer.com 

Caterpillar Inc. 

Dave Bradshaw 

Truck Engine District Manager, Northwest Region 

Phone: 425-562-9659 

E-mail: bradshaw_david_G@cat.com 

Battelle 

Kevin Chandler 

Program Manager 

Phone: 614-424-5127 

E-mail: chandlek@battelle.org 

37
Acronyms and Abbreviations 

AB Atlantic Base 

AVTA Advanced Vehicle Testing Activity 

B5 biodiesel blend at 5% 

bhp brake horsepower 

CAT Caterpillar 

CNG compressed natural gas 

CO carbon monoxide 

DDC Detroit Diesel Corporation 

DOC diesel oxidation catalyst 

DOE U.S. Department of Energy 

DPF diesel particulate filter 

DPIM dual-power inverter module 

EPA U.S. Environmental Protection Agency 

EGR exhaust gas recirculation 

ft feet 

ft-lb foot-pounds 

FTA Federal Transit Administration 

g/bhp-hr grams per brake horsepower-hour 

GM General Motors 

GVWR gross vehicle weight rating 

HC hydrocarbons 

HEV hybrid-electric vehicle 

hp horsepower 

HVAC heating, ventilation, and air-conditioning 

in. inches 

KC Metro King County Metro Transit 

kW kilowatts 

L liter 

lb pounds 

LNG liquefied natural gas 

MBRC miles between road calls 

mpg miles per gallon 

mph miles per hour 

NREL National Renewable Energy Laboratory 

NMHC nonmethane hydrocarbons 

NOx oxides of nitrogen 

NTD National Transit Database 

PM particulate matter 

ppm parts per million 

PMI preventive maintenance inspection 

RB Ryerson Base 

RC road call 

R&D research and development 

38
RFP request for proposals 

rpm revolutions per minute 

SB South Base 

THC total hydrocarbon 

ULSD ultra-low-sulfur diesel 

V volts 

VDC volts direct current 

39
Bibliography 

Chandler, K., Eudy, L., Eberts, E., 2006, New York City Transit Hybrid and CNG Transit Buses: Interim 

Evaluation Results, National Renewable Energy Laboratory, Golden, CO, NREL/TP-540-38843 

Chandler, K., 2006, Ten Years of Compressed Natural Gas (CNG) Operations at SunLine Transit Agency, 

National Renewable Energy Laboratory, Golden, CO, NREL/SR-540-39180 

NREL, 2005, Advanced Technology Vehicles in Service: New York City Transit Drives Hybrid-electric 

Buses into the Future, National Renewable Energy Laboratory, Golden, CO, DOE/GO-102005-2009 

NREL, 2005, Advanced Technology Vehicles in Service, Knoxville Area Transit, National Renewable 

Energy Laboratory, Golden, CO, DOE/GO-102005-2085 

NREL, 2004, Advanced Technology Vehicles in Service, King County Metro Transit, National Renewable 

Energy Laboratory, Golden, CO, DOE/GO-102004-2026 

NREL, 2004, Advanced Technology Vehicles in Service, Indianapolis Public Transportation, National 

Renewable Energy Laboratory, Golden, CO, DOE/GO-102004-1986 

Chandler, K., Proc, K., 2004, Norcal Prototype LNG Truck Fleet, Final Results, National Renewable 

Energy Laboratory, Golden, CO, DOE/GO-102004-1920 

NREL, 2003, Advanced Technology Vehicles in Service: MTA New York City Transit, Diesel Hybridelectric Buses, National Renewable Energy Laboratory, Golden, CO, NREL/FS-540-33397 

Chandler, K., Eudy, L., 2003, ThunderPower, Bus Evaluation at SunLine Transit Agency, National 

Renewable Laboratory, Golden, CO, DOE/GO-102003-1786 

Chandler, K., Vertin, K., Alleman, T., Clark, N., 2003, Ralphs Grocery Company EC-Diesel Truck Fleet: 

Final Results, National Renewable Energy Laboratory, Golden, CO, NREL/BR-540-31363 

Eudy, L., Gifford, M., 2003, Challenges and Experiences with Electric Propulsion Transit Buses in the 

United States, National Renewable Energy Laboratory, Golden, CO, DOE/GO-102003-1791 

NREL, 2002, Advanced Technology Vehicles in Service, Norcal Waste Systems, Inc., National Renewable 

Energy Laboratory, Golden, CO, NREL/FS-540-32808 

Chandler, K., Walkowicz, K., Eudy, L., 2002, New York City Transit Diesel Hybrid-Electric Buses: Final 

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

Battelle/NREL, 2002, NYCT’s Diesel Hybrid-Electric Buses, Program Status Update, National 

Renewable Energy Laboratory, Golden, CO, NREL/BR-540-31668 

NREL, 2002, General Evaluation Plan, Fleet Test & Evaluation Projects, National Renewable Energy 

Laboratory, Golden, CO, NREL/BR-540-32392 

Eudy, L., 2002, Natural Gas in Transit Fleets: A Review of the Transit Experience, National Renewable 

Energy Laboratory, Golden, CO, NREL/TP-540-31479 

40
Battelle/NREL, 2001, Advanced Technology Vehicles in Service, Diesel Hybrid-electric Buses, National 

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

Chandler, K., Norton, P., Clark, N., 2001, Waste Management’s LNG Truck Fleet, Final Results, National 

Renewable Energy Laboratory, Golden, CO, NREL/BR-540-29073 

Chandler, K., Norton, P., Clark, N., 2000, DART’s LNG Bus Fleet, Final Results, National Renewable 

Energy Laboratory, Golden, CO, NREL/BR-540-28739 

Chandler, K., Norton, P., Clark, N., 2000, Raley’s LNG Truck Fleet, Final Results, National Renewable 

Energy Laboratory, Golden, CO, NREL/BR-540-27678 

Battelle, 1999, Waste Management’s LNG Truck Fleet, Start-Up Experience, National Renewable Energy 

Laboratory, Golden, CO, NREL/BR-540-26617 

Battelle, 1997, Raley’s LNG Truck Fleet, Start-Up Experience, National Renewable Energy Laboratory, 

Golden, CO, NREL/BR-540-23402 

Battelle, 2000, DART’s LNG Bus Fleet, Start-Up Experience, National Renewable Energy Laboratory, 

Golden, CO, NREL/BR-540-28124 

Motta, R., Norton, P., Kelly, K., Chandler, K., Schumacher, L., Nigel, N., 1996, Alternative Fuel Transit 

Buses, Final Results from the National Renewable Energy Laboratory (NREL) Vehicle Evaluation 

Program, National Renewable Energy Laboratory, Golden, CO, NREL/TP-425-20513 

41
Appendix: Fleet Summary Statistics 

King County Metro (Seattle, WA) Fleet Summary Statistics 

Evaluation Period Only 

Fleet Operations and Economics 

Diesel Hybrid Hybrid 

Ryerson Atlantic South 

Number of Vehicles 10 10 9

Period Used for Fuel Analysis 4/05 - 9/05 4/05 - 9/05 4/05 - 9/05

Total Number of Months in Period 6 6 6

Fuel Analysis Base Fleet Mileage 168,268 170,812 203,765

Period Used for Maintenance Op 

Analysis 

4/05 - 9/05 4/05 - 9/05 4/05 - 9/05

Total Number of Months in Period 6 6 6

Maintenance Analysis Base Fleet 

Mileage 

174,466 179,092 223,507

Average Monthly Mileage per Vehicle 2,908 2,985 4,139

Fleet Fuel Usage in Gal. 65,886 53,248 54,318

Representative Fleet MPG 2.55 3.21 3.75

Hybrid compared to Diesel 26% 47%

Average Fuel Cost as Reported 

(adjusted from 2.00—see report) 

1.95 1.95 1.95

per Gal D2 per Gal D2 per Gal D2

Average Fuel Cost per Energy 

Equivalent 

1.95 1.95 1.95

Fuel Cost per Mile 0.764 0.608 0.520

Number of Total Road Calls 23 31 48

MBRC All Road Calls 7,585 5,777 4,656

Number of Propulsion System Road 

Calls 

12 14 26

MBRC Propulsion System Road Calls 14,539 12,792 8,596

Total Scheduled Repair Cost per Mile 0.165 0.172 0.119

Total Unscheduled Repair cost per Mile 0.299 0.294 0.336

Total Maintenance Cost per Mile 0.464 0.466 0.455

Total Operating Cost per Mile 1.228 1.074 0.975

Maintenance Costs 

Diesel Hybrid Hybrid 

Ryerson Atlantic South 

Fleet Mileage 174,466 179,092 223,507

Total Parts Cost 18,813.75 16,905.61 15,196.75

42
Total Labor Hours 1244.2 1330.5 1729.2

Average Labor Cost 62,210.00 66,525.00 86,460.00

(@ $50.00 per hour) 

Total Maintenance Cost 81,023.75 83,430.61 101,656.75

Total Maintenance Cost per Mile 0.464 0.466 0.455

Breakdown of Maintenance Costs by Vehicle System 

Diesel Hybrid Hybrid 

Ryerson Atlantic South 

Fleet Mileage 174,466 179,092 223,507

Total Propulsion-Related Systems 

(ATA VMRS 27, 30, 31, 32, 33, 41, 42, 43, 44, 45, 46, 65)

Parts Cost 9,292.47 5,656.96 4,922.93

Labor Hours 310.5 374.3 606.7

Average Labor Cost 15,525.00 18,712.50 30,335.00

Total Cost (for system) 24,817.47 24,369.46 35,257.93

Total Cost (for system) per Mile 0.1422 0.1361 0.1577

Exhaust System Repairs (ATA VMRS 43)

Parts Cost 121.10 0.00 62.89

Labor Hours 14.0 0.0 10.5

Average Labor Cost 700.00 0.00 525.00

Total Cost (for system) 821.10 0.00 587.89

Total Cost (for system) per Mile 0.0047 0.0000 0.0026

Fuel System Repairs (ATA VMRS 44)

Parts Cost 473.24 507.25 450.28

Labor Hours 7.0 13.8 16.0

Average Labor Cost 350.00 687.50 800.00

Total Cost (for system) 823.24 1,194.75 1,250.28

Total Cost (for system) per Mile 0.0047 0.0067 0.0056

Power Plant (Engine) Repairs (ATA VMRS 45)

Parts Cost 1,829.09 1,770.62 1,987.02

Labor Hours 175.0 167.0 182.5

Average Labor Cost 8,750.00 8,350.00 9,125.00

Total Cost (for system) 10,579.09 10,120.62 11,112.02

Total Cost (for system) per Mile 0.0606 0.0565 0.0497

Electric Motor, Generator, and Battery Repairs (ATA VMRS 46) 

Parts Cost 0.00 534.45 10.95

Labor Hours 0.0 36.0 246.7

Average Labor Cost 0.00 1,800.00 12,335.00

Total Cost (for system) 0.00 2,334.45 12,345.95

Total Cost (for system) per Mile 0.0000 0.0130 0.0552

Electrical System Repairs (ATA VMRS 30-Electrical General, 

31-Charging, 32-Cranking, 33-Ignition)

Parts Cost 959.96 817.15 517.86

43
Labor Hours 42.5 92.5 73.5

Average Labor Cost 2,125.00 4,625.00 3,675.00

Total Cost (for system) 3,084.96 5,442.15 4,192.86

Total Cost (for system) per Mile 0.0177 0.0304 0.0188

Breakdown of Maintenance Costs by Vehicle System (continued)

Diesel Hybrid Hybrid 

Ryerson Atlantic South 

Air Intake System Repairs (ATA VMRS 41)

Parts Cost 341.85 95.18 146.25

Labor Hours 3.0 2.0 3.0

Average Labor Cost 150.00 100.00 150.00

Total Cost (for system) 491.85 195.18 296.25

Total Cost (for system) per Mile 0.0028 0.0011 0.0013

Cooling System Repairs (ATA VMRS 42)

Parts Cost 3,823.58 165.11 154.10

Labor Hours 61.0 52.0 70.0

Average Labor Cost 3,050.00 2,600.00 3,500.00

Total Cost (for system) 6,873.58 2,765.11 3,654.10

Total Cost (for system) per Mile 0.0394 0.0154 0.0163

Hydraulic Repairs (ATA VMRS 65)

Parts Cost 1,742.89 1,705.10 1,534.59

Labor Hours 0.0 0.0 0.0

Average Labor Cost 0.00 0.00 0.00

Total Cost (for system) 1,742.89 1,705.10 1,534.59

Total Cost (for system) per Mile 0.0100 0.0095 0.0069

Transmission Repairs (ATA VMRS 27)

Parts Cost 0.76 62.10 58.99

Labor Hours 8.0 11.0 4.5

Average Labor Cost 200.00 550.00 225.00

Total Cost (for system) 200.76 612.10 283.99

Total Cost (for system) per Mile 0.0012 0.0034 0.0013

Cab, Body, and Accessories Systems Repairs 

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

Parts Cost 3,307.30 6,193.62 4,180.29

Labor Hours 484.0 568.8 547.8

Average Labor Cost 24,200.00 28,437.50 27,387.50

Total Cost (for system) 27,507.30 34,631.12 31,567.79

Total Cost (for system) per Mile 0.1577 0.1934 0.1412

Inspections Only - no parts replacements (101)

Parts Cost 0.00 0.00 0.00

Labor Hours 173.5 218.0 228.0

Average Labor Cost 8,675.00 10,900.00 11,400.00

Total Cost (for system) 8,675.00 10,900.00 11,400.00

Total Cost (for system) per Mile 0.0497 0.0609 0.0510

44
Breakdown of Maintenance Costs by Vehicle System (continued)

Diesel Hybrid Hybrid 

Ryerson Atlantic South 

HVAC System Repairs (ATA VMRS 01)

Parts Cost 4,941.81 2,775.62 3,489.31

Labor Hours 158.5 84.3 158.0

Average Labor Cost 7,925.00 4,212.50 7,900.00

Total Cost (for system) 12,866.81 6,988.12 11,389.31

Total Cost (for system) per Mile 0.0737 0.0390 0.0510

Brake System Repairs (ATA VMRS 13)

Parts Cost 8.84 0.00 0.00

Labor Hours 6.5 17.5 17.5

Average Labor Cost 325.00 875.00 875.00

Total Cost (for system) 333.84 875.00 875.00

Total Cost (for system) per Mile 0.0019 0.0049 0.0039

Air System Repairs (ATA VMRS 10)

Parts Cost 414.84 151.42 231.12

Labor Hours 13.0 8.0 24.8

Average Labor Cost 650.00 400.00 1,237.50

Total Cost (for system) 1,064.84 551.42 1,468.62

Total Cost (for system) per Mile 0.0061 0.0031 0.0066

Lighting System Repairs (ATA VMRS 34)

Parts Cost 96.25 97.43 169.09

Labor Hours 15.5 19.5 10.0

Average Labor Cost 775.00 975.00 500.00

Total Cost (for system) 871.25 1,072.43 669.09

Total Cost (for system) per Mile 0.0050 0.0060 0.0030

Parts Cost 241.96 2,013.82 824.03

Labor Hours 27.5 31.8 37.5

Average Labor Cost 1,375.00 1,587.50 1,875.00

Total Cost (for system) 1,616.96 3,601.32 2,699.03

Total Cost (for system) per Mile 0.0093 0.0201 0.0121

Parts Cost 500.42 8.82 616.58

Labor Hours 35.5 1.0 60.0

Average Labor Cost 1,775.00 50.00 3,000.00

Total Cost (for system) 2,275.42 58.82 3,616.58

Total Cost (for system) per Mile 0.0130 0.0003 0.0162

Tire Repairs (ATA VMRS 17)

Parts Cost 0.00 0.00 0.00

Labor Hours 3.0 0.0 15.5

Average Labor Cost 150.00 0.00 775.00

Total Cost (for system) 150.00 0.00 775.00

Total Cost (for system) per Mile 0.0009 0.0000 0.0035

45
Breakdown of Maintenance Costs by Vehicle System (continued)

Diesel Hybrid Hybrid 

Ryerson Atlantic South 

Articulation Repairs (ATA VMRS 59) 

Parts Cost 9.87 0.02 762.89

Labor Hours 17.0 7.5 23.5

Average Labor Cost 850.00 375.00 1,175.00

Total Cost (for system) 859.87 375.02 1,937.89

Total Cost (for system) per Mile 0.0049 0.0021 0.0087

Notes 

1. The engine and fuel-related systems were chosen to include only those systems of the vehicles that could be 

directly a part of the propulsion system. 

2. ATA VMRS coding is based on parts that were replaced. If there was no part replaced in a given repair, then the 

code was chosen by the system being worked on. 

3. In general, inspections (with no part replacements) were only included in the overall totals (not by system). 

101 was created to track labor costs for PM inspections. 

4. ATA VMRS 02-Cab and Sheet Metal represents seats, doors, etc.; ATA VMRS 50-Accessories represents 

things like fire extinguishers, test kits, etc.; ATA VMRS 71-Body represent mostly windows and windshields. 

5. Average labor cost is assumed to be $50 per hour. 

6. Warranty costs are not included.

46
F1147-E(12/2004) 

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PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ORGANIZATION.

1. REPORT DATE (DD-MM-YYYY)

April 2006 

2. REPORT TYPE

Technical Report 

3. DATES COVERED (From - To)

April 2005 - September 2005 

5a. CONTRACT NUMBER

DE-AC36-99-GO10337 

5b. GRANT NUMBER

4. TITLE AND SUBTITLE

King County Metro Transit Hybrid Articulated Buses: Interim 

Evaluation Results 

5c. PROGRAM ELEMENT NUMBER

5d. PROJECT NUMBER

NREL/TP-540-39742 

5e. TASK NUMBER

FC06.3000 

6. AUTHOR(S)

K. Chandler and K. Walkowicz 

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/TP-540-39742 

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NREL 

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13. SUPPLEMENTARY NOTES

14. ABSTRACT (Maximum 200 Words)

This document is an interim technical report on a comparison and evaluation of new diesel and diesel hybrid-electric 

articulated buses operated as part of the King County Metro Transit (KC Metro) fleet in Seattle, Washington. This 

interim report covers the first six months of a planned 12-month evaluation at KC Metro. The evaluation is being 

completed through the U.S. Department of Energy’s (DOE) Advanced Vehicle Testing Activity (AVTA) by the National 

Renewable Energy Laboratory (NREL). 

15. SUBJECT TERMS

Diesel hybrid-electric articulated buses; King County Metro Transit; KC Metro; fleet evaluation; U.S. Department of 

Energy; DOE; Advanced Vehicle Testing Activity; AVTA; National Renewable Energy Laboratory; NREL; Battelle 

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