Muni Subway Expansion Project

Project Introduction


Note that the Muni Subway Expansion Project is no longer an active project. Please refer to the ConnectSF Transit Strategy for San Francisco’s transit expansion priorities. In addition, the Muni Metro Modernization Program is one of the transit priorities identified by ConnectSF that focuses on addressing some of the problems that the Muni Subway Expansion Project set out to address via a different package of improvements.

The Muni Subway Expansion project is based on a simple idea: make the best use of the resources we have. That means our subway tunnel and our train cars. We should make one of Muni's rail lines a full subway line, providing a backbone of fast, reliable, high-capacity transit that runs across the whole city – from the very southwest corner of San Francisco to the Embarcadero on the northeast. Introducing a full subway would unlock the ability to utilize the existing subway tunnel to its fullest capacity. The line selected as the spine, the M Ocean View, connects the major job centers and dense planned housing in eastern San Francisco with the densest and fastest-growing node in Southwest San Francisco. This is about making the Metro system work better for everyone.

This big idea is still in very early stages of planning. As a part of the planning phase, we have been focused on defining the project’s conceptual design. The next step is for it to be considered for prioritization as a part of a citywide effort called ConnectSF that will identify the full universe of major transit investments that we need to provide a world class transit system.

Current Phase or Stage
New bike lanes
Wider sidewalks and improved pedestrian areas
Muni Metro train
New subway for M Ocean View
Streetscape Icon
More room for street amenities
Project Details, History or Features

Look at Muni Metro during the commute and you see the packed train cars.  What if we told you there is already extra capacity in the system to move thousands more people, we just need to unlock it?

That’s what the Muni Subway Expansion does.

We have to understand a little history first. Muni’s Metro rail system is a mash-up of a rail system designed in two different eras. In the 1800s and early 1900s, San Francisco built a robust streetcar network across the city. Several decades later, the BART system was built in the 1970s, including the Muni subway under Market Street that all our rail lines feed into. Once Muni rail started using the new subway, Muni began operating as a hybrid subway-streetcar system. The Market Street subway—a modern subway tunnel under the densest employment center west of the Mississippi! – is an incredibly valuable asset. But we aren’t able to make use of its full value because of the Metro’s hybrid subway-surface design.

  • The subway stations are long enough to serve trains more than twice as long as the current two-car trains. The problem is running trains longer than two cars on surface streets creates collision risks and blocks intersections. That’s the inherent flaw of the hybrid system.
  • Running trains at the surface also results in a slower and more variable travel time. This limits the number of passengers per hour that can travel under Market Street to much less than what the subway was designed to accommodate


Major milestones before project approval and finalizing a schedule include:

•    A multi-year environmental review effort
•    Ongoing community outreach and involvement
•    Identification of a full funding strategy

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Metropolitan Transportation Commission logo
Muni logo
San Francisco County Transportation Authority logo
SF Planning Department logo
Contact Information
Liz Brisson