Dept. of Transportation
Metro Transit Division

King Street Center
201 S Jackson St
Seattle, WA 98104
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Trolley Bus System Evaluation

Study report

May 27, 2011

Metro's 159 electric trolley buses are scheduled to be replaced in 2014. Before purchasing new buses, an in-depth, evaluation of vehicle options was conducted to determine relative costs, limitations, environmental impacts, and benefits. The findings from this evaluation will inform the technology decision for replacement of the trolley buses.

Final report:

Project Overview

Metro to study possible alternatives for aging electric trolley buses

trolley bus

Project Details

The trolley evaluation scope, work plan, and timeline were sent to the County Council on Aug. 26. Learn more...

King County Metro Transit has a fleet of 159 electric trolley buses that run along nearly 70 miles of overhead wire in Seattle. These buses are reaching the end of their useful lives, and Metro may need to order replacement buses before the end of 2012.

Before doing that, Metro has been directed by the Metropolitan King County Council to study potential alternative bus-propulsion technologies in order to evaluate and compare their costs, limitations, and benefits. The goal is to evaluate several factors to ensure the best overall value for the region.

This in-depth study will be limited to the current 14-route trolley system, with some variations as appropriate for each technology. The study findings will help the county make an informed decision about the best vehicle technology to use on these routes as the current trolley buses wear out.

» Project information sheet

Questions and Answers

  • What is the decision-making process for replacing the trolleys?

    During its 2011 biennial budget process, the County Council will decide which type of bus Metro will purchase to replace the current trolley buses. The Trolley Bus System Evaluation will help the Council make an informed decision about the best vehicle technology to use.

  • How many trolley buses does King County Metro Transit operate?

    Metro has 159 electric trolley buses.

  • How long have the trolley buses been in operation?

    Trolleys like the ones you see on Seattle’s streets today have been in operation for 70 years. Metro Transit was started in 1973, when the public Seattle Transit System was merged with the private Metropolitan Transit Corporation. Metro inherited Seattle Transit’s aging trolley network, and replaced it with a new expanded electric trolley bus system in 1978.

    The Metro Employees Historic Vehicle Association (MEHVA) has an online history of the trolleys in Seattle at

  • How big is Metro’s trolley system?

    There are 14 Metro routes that use electric trolley buses running on more than 70 miles of two-way overhead wire throughout downtown Seattle, Ballard, Queen Anne, the University District, Capitol Hill, First Hill, Beacon Hill and the Rainier Valley.

  • How many trolley bus routes does Metro operate?

    There are currently 14 trolley routes: 1, 2, 3, 4, 7, 10, 12, 13, 14, 36, 43, 44, 49, and 70.

  • How many miles do the trolleys travel a year?

    In 2009, Metro trolleys traveled 2,906,297 miles during 597,459 hours of service.

  • What is the ridership for the trolley routes, and what percentage do trolley riders represent of all Metro ridership?

    There were 19.7 million boardings on Metro’s trolley routes in 2009. That’s about one-fifth of Metro’s total average weekday boardings.

  • Are there other public trolley bus systems in the United States?

    Not many. Only Seattle, San Francisco, Boston, Philadelphia, and Dayton, Ohio have electric trolley buses currently in operation. In Canada, Vancouver, B.C. also has trolleys. Electric trolley buses are more common in Europe, Asia, and Latin America.

  • How are the trolley buses different from diesel or hybrid buses?

    A Metro trolley bus draws power from the overhead electrified wires, and that power is used to drive a large electric motor. The trolleys connect to the wire via a pole on the roof that is topped by an insulated shoe. The pressure from the spring-loaded pole keeps the shoe pushed up against the overhead wire, providing the connection that powers the bus and allowing the trolley to maneuver through turns and around corners.

    Metro’s current trolley buses cannot operate if they are not connected to the overhead power. Unlike a hybrid bus, they have no on-board energy storage system. So, when a trolley is braking or going downhill, the extra energy that is developed is dissipated through resistors. Some energy can be put back into the power lines, but only if there is another trolley on the line that needs the energy.

    With hybrid buses, the engine is coupled to a generator and the generated energy powers the motor. When more power is generated than is needed to operate the bus, the extra energy goes into a battery pack for later use. When the bus is coasting downhill or braking, that energy is turned into electricity and also stored into the battery pack on the roof of the bus. Stored energy in the batteries assists in the acceleration of the bus during starts, reducing the load on the diesel engine.

  • Where does Metro get the electricity used to power the trolley buses?

    Metro purchases electricity from Seattle City Light. The power is delivered to 40 Metro substations scattered across the city. Each substation houses electrical equipment that converts the incoming 26,000-volt AC (alternating current) power into the 700-volt DC (direct current) power used by the trolleys. The converted electricity is fed into the overhead wires via conduits that travel underneath Seattle streets and then the poles that support the overhead system.

» Questions and Answers handout

Community involvement

Community involvement timeline
Community Involvement Timeline

Metro kicked off the first phase of public outreach for the Trolley Bus System Evaluation on June 22, 2010 with a community open house, which was followed by a series of presentations to neighborhood groups. Thanks to all who participated in these meetings or sent in written comments. Community input played an important role in shaping the scope of the study.

In fall 2010, Metro and the consultant team began the technical evaluation. Once draft results are available in the first quarter of 2011, Metro will launch another phase of community outreach to gather input on the study.

The final evaluation will be sent to the County Council in spring 2011 to inform their biennial budget process. During this process, the Council will make the final decision about which type of bus to purchase to replace the current trolley buses.

Contact us

For more information, please visit the project details page or contact:

Ashley DeForest, Community Relations Planner

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Ashley DeForest
Community Relations Planner
King County Department of Transportation

More trolley information

News releases

Existing trolley bus routes

Performance Audits