Dept. of Transportation
Metro Transit Division

King Street Center
201 S Jackson St
Seattle, WA 98104
Metro Online Home
Metro Online Home

« Back to Project Overview

Trolley Bus System Evaluation

Project details

video A quick look into King County Metro Transit's trolley system.

Work plan, scope, and schedule

Metro completed the work plan, scope, and schedule for the Trolley Bus System Evaluation in August 2010. This plan reviews the status of the existing trolley bus fleet, identifies the alternative bus propulsion technologies that the study will evaluate, outlines the scope of the evaluation, and describes policy issues and choices associated with each alternative. The work plan also has a schedule that includes public involvement and a process for input and monitoring by the Metropolitan King County Council.

Status of the existing trolley fleet

Metro will analyze the possibility of extending the life of its current 159-bus trolley fleet beyond the scheduled replacement date in 2014. So far, Metro has found that such extension would require maintenance and parts replacement that are beyond those associated with normal wear and tear.

For example, the 59 60-foot Breda articulated trolley buses would require repairs to their propulsion systems, bodies and frames, and drive axle planetary gears, while the 100 40-foot Gillig trolley buses would require additional work on their propulsion systems and direct-current converters. Technical support and parts from the original manufacturers are no longer available for these vehicles and components, so much of this work would require Metro to engineer and build replacement parts.

Alternative bus propulsion technologies

Metro identified and did preliminary evaluations of a range of propulsion technologies for replacing the trolley bus fleet. These technologies included all-electric trolleys, diesel and diesel-electric hybrids, compressed natural gas, electric batteries, and hydrogen fuel cells. These technologies were identified because they are either in use by, or are being tested by, other transit agencies.

Metro reviewed these technologies to determine their feasibility for a large fleet purchase in 2012. Based on this review, Metro will conduct more detailed analysis of the diesel-electric hybrid and electric trolley propulsion technologies only. Table 1 summarizes the results and reasons why other technologies were not chosen for more detailed evaluation.

Table 1: Vehicle propulsion review summary
Technologies Feasibility for study
Diesel No further evaluation—similar to hybrids, with greater environmental impact
Diesel-electric hybrid Evaluate—reworked to accommodate grades
Electric trolley Evaluate—with propulsion backup
Electric battery No further evaluation—not commercially available; reduced travel range
Compressed natural gas   No further evaluation—high costs; greater environmental impacts than hybrids
Hydrogen fuel cell No further evaluation—not commercially available; high costs; reduced travel range; reduced reliability


The Trolley Bus System evaluation will assess diesel-electric hybrid and electric trolley technologies in five areas:

  1. Vehicle and system assessment and costs
  2. Service network
  3. Environmental effects
  4. Funding
  5. Legal review

Table 2 outlines the scope of the evaluation in more detail:

Table 2: Scope of Evaluation
Elements Description
Vehicle and system assessment and costs—Analysis of performance and lifecycle cost
Vehicle Capital Costs Cost of purchasing technology, including modifications needed for Seattle network
Operating and Maintenance Costs Cost to operate and maintain the vehicle, including energy, parts, repair, mechanical labor, fueling, etc.
Energy Costs Sensitivity analysis of energy costs for lifetime of vehicle, including high, low and medium investment and impacts to City Light rate payers
Power/Maintenance Infrastructure Costs Cost of maintaining the infrastructure for various technologies, including the costs of removal of trolley facilities, analysis of the impacts of decommissioning and benefits of keeping the wire
Vehicle Flexibility Analysis of flexibility of service, including ability to reroute due to construction, expand service as system grows, and operate in adverse weather
Impact of Grade on System Ability to operate on hills—maintenance implications of equipment and impacts to the system
Impact of Weight on Road Impact of the weight of the vehicle on the roadway
Service network—Analysis of effects on Metro’s service network
Service Design Analysis of any changes in route network
Scheduling Efficiencies Analysis of scheduling efficiencies from changes in service delivery, including refueling needs and the ability to connect routes
Environmental assessment
Traffic Impacts Impact on traffic, including changes in general purpose, transit, pedestrian, bicycle and parking impacts
Noise Analysis of the noise type and volume, quantitative estimates for expected decibel output
Greenhouse Gas Emissions Analysis of the CO2 emissions, including development, production, and delivery of service, plus a discussion on carbon trading impacts
Air Quality Analysis of the air quality emission, including development, production, and delivery service
Environmental Justice Effects on low-income and minority groups, plus quality of life implications
Historic Evaluation Effects that might require review under Section 106 of the National Historical Preservation Act
Community Impacts Assessment of community impacts, including visual and aesthetics, and “sense of place”
Other Requirements Discussion of other possible impacts, including hazardous materials, water quality, storm water management, etc.
Funding—Analysis of effects on funding, including local, state, and federal grants
Funding Implications Funding impacts of the various technologies, including estimates for local, state and federal grants
Legal review—Analysis of legal issues
Legal Review Analysis of existing agreements in place and their impacts with each technology

Metro plans to hire a consultant to help in the evaluation. This consultant will work with Metro staff members to analyze life cycle costs and environmental effects of each technology. Metro will do system analyses and assess vehicle performance and grant impacts with support from the consultant team.


The following timeline outlines the proposed Trolley Bus System Evaluation schedule, including when the buses need to be purchased and replaced.

Trolley timeline
Timeline—Evaluation and Procurement

For more information, please contact Ashley DeForest, Community Relations Planner, at 206-684-1154 or—or visit the study website at