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Zero Emissions: Metro Transit Working to Mitigate Risks to County’s Ambitious 2035 Goal

Published June 11, 2024

King County Metro Transit is making substantial efforts toward achieving King County’s goal of a zero-emission fleet by 2035, improving collaboration and planning needed to complete the transition. It also faces significant risks that may impede reaching the goal, including a declining number of bus manufacturers and technology limitations. In response to these risks, Metro Transit is considering zero-emission options beyond battery-electric buses. We found that Metro Transit could improve communication about its efforts to diversify propulsion systems, establish emergency plans, and formalize existing efforts within its Capital Division to improve project processes and the use of collaborative delivery. This audit answers questions posed to us by the King County Council in Ordinance 19546 and makes recommendations for ways Metro Transit can improve the likelihood it will reach the 2035 goal.

Audit Highlights

Metro Transit has devoted substantial resources to organizing its department to transition to a zero-emission bus fleet by 2035, through improving the planning and collaboration efforts needed for this goal. It also faces significant risks that may impede reaching the goal, including the loss of bus manufacturers, technology limitations, sufficient electricity supply in the future, and lagging battery-electric bus performance. Metro Transit is exploring other propulsion systems, such as hydrogen fuel cell buses, to mitigate some of these risks, but it has not yet communicated this shift in strategy to the King County Council, missing opportunities to help ensure decision-makers are informed. It has also not yet adapted its emergency response role to a zero-emission fleet, increasing safety risks if Metro Transit is not able to fulfill anticipated roles in a disaster.

Metro Transit has planned extensive capital work through 2038 to build the infrastructure needed to support zero emissions operations, including work at all eight of its bases. The Metro Transit Capital Division is working to improve planning and use collaborative delivery methods that could save time on projects, but it has not developed a strategy to maximize efficiency and other benefits. We also found that capital project teams do not yet consistently engage central procurement or Metro Transit’s government relations and safety staff early in projects. As a result, teams might not address risks that cause delays or safety and security issues.

We recommend that Metro Transit improve communication about its efforts to diversify propulsion systems and establish emergency plans. We also recommend the agency implement a strategy to make best use of collaborative delivery methods and take steps to formalize procurement, safety collaboration, and government relations in capital projects.

Metro Transit’s bus operations create 43 percent of King County government’s greenhouse gas emissions, providing the single biggest opportunity to reduce King County’s carbon footprint. As directed by the County Council, Metro Transit is working to transition its revenue bus fleet to zero emissions by 2035. This goal is one of the most ambitious in the nation, requiring Metro Transit to compress timeframes for planning, stakeholder engagement, and capital project delivery. The accelerated pace compounds risks associated with the unknowns of emerging technology and supply chain challenges. Metro Transit will need to improve its ability to complete capital projects to stay on schedule and avoid costly changes to projects.

Audit Team

Audit Team

Elise Garvey, Luc Poon, and Ben Thompson worked on this audit. If you have any questions or would like more information, please call the King County Auditor's Office at 206-477-1033 or contact us by email at