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Bus Base Expansion

Growing for the future

King County Metro is making major investments to support more and better bus service.

Bases are the heart of our bus system. They provide essential support for safe and reliable service. This support includes housing and maintaining off-duty buses as well as training, dispatching, and managing bus operators. Base workforces include bus operators, supervisors, administrative staff, and mechanics, painters, and others in skilled trades.

Metro created a bus base expansion program to meet the current and future transit demand of our growing region. It will allow us to house and maintain our buses more efficiently and convert to an all-electric bus fleet by 2040. Learn more about our bus base expansion program below and how some plans have changed as a result of the COVID-19 pandemic.

Project details

We are making major investments so we can offer more and better service:

The bus base expansion program will initially focus on our South Campus in Tukwila where we will open two new bases: Interim Base and South Annex Base. Metro will continue to monitor demand for new service and the potential need for a new base in south King County.

King County is taking action to confront climate change and Metro is doing our part to reduce transportation-related greenhouse gas emissions. Building on our current fleet of electric trolley buses, we will transition to a fully electric bus fleet by 2040. The new South Annex Base in Tukwila will be an all-electric bus base when complete in 2027. Then we’ll retrofit all of our existing bases for electric bus charging.

Base expansion centers community. New bases support current and future service that will improve access to transit and connections to jobs and essential services. As projects move through design, construction, and operations, we’ll work with communities to help create facilities that support their goals and add value. We are also committed to creating new jobs, providing job training, and continued community workforce agreements.

South Campus

Metro has operated facilities in Tukwila for more than 40 years. As part of our bus base expansion program, the new facilities at South Campus will provide meaningful contributions to the physical, environmental, and economic health of the community.

The South Campus expansion includes the following projects:

The first new base in decades

Interim Base at South Campus is Metro’s first new base in decades. Construction kicked off in 2019, with substantial completion in early summer 2021. We called it "interim" because we initially planned for a temporary facility. However, we now have a longer-term use for this base and are planning to rename it.


Interim base

Paving the way for King County’s clean energy fleet

Metro is leading the nation in creating a fully electric bus fleet. South Annex Base will house and maintain up to 250 battery electric, zero-emission buses and operation facilities that are third-party certified green buildings. We’re currently in the design phase, with construction scheduled to begin in 2025, and operations scheduled to start in 2027.


South annex base


South Annex Base RAISE Grant Funding

South Annex Base is critical to Metro’s vision for the future – a region served by seamless, multi-modal transit that provides equity, efficiency, and sustainability. Metro is applying for the Rebuilding American Infrastructure with Sustainability and Equity (RAISE) Grant Program to help fund the new base, including electrification.

Application materials

Questions about Metro’s RAISE grant application?

Contact Peter Heffernan, King County Metro Intergovernmental Relations.

Department of transportation logo

South King County Base

Metro has paused plans for a new fully electric bus base in south King County until we reassess future service demands. Should service demand return to projected pre-COVID level growth, we will consider reactivating our plans to build South King County Base.

Changes to this project are included in King County's proposed budget. Find more information on the 2021-2022 budget in our blog post.

Blog posts

Stay up to date on bus base expansion.