Mission Bay Loop

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Project Introduction

The Mission Bay Loop (the Loop) provides turn-around capabilities for the T Third Street light rail via a connection of trackway from Third Street to 18th, Illinois, and 19th streets and supports the reliability of the overall system by allowing trains to turn around for special events and during peak periods to accommodate additional service between Mission Bay and Market Street Muni Metro. The Loop is integral to the Central Subway Project due to emerging population growth in the southeast section of the city and the need to provide transit service to destinations such as Caltrain, BART the Financial District and the Chinatown area.

Project Timeline
July 2016
Construction Begins
Fall 2019
Construction Completion
Project Status
  1. Completed
Muni Metro train
Improve T Third service by increasing frequency, reducing service delays and accommodating high ridership demand
Install street lighting, traffic signals, and crosswalks
Bus Routes and Rail Lines

Project Background 

The Loop was designed in 1998 as part of the Third Street Light Rail Project, completed in 2003. An Environmental Impact Statement/Environmental Impact Report (EIS/EIR) for the Third Street Light Rail Project was completed and approved in 1999 by the Federal Transit Administration (FTA) and the City and County of San Francisco. Yet, due to budget constraints, construction of the Loop was deferred.

The project secured funding under a partnership with the FTA for allocation of $10 million TIGER funds through the Department of Transportation and the Lifeline Transportation Program from the Metropolitan Transportation Commission (MTC). Additionally, the FTA prepared an Environmental Assessment (EA) report to identify and evaluate any conditions that may have changed after 1999 that could potentially result in adverse environmental effects from construction and operation of the Loop.


T Third line inbound

The existing trackway on 18th and 19th streets between Third and Illinois streets will be extended to Illinois Street to complete the Loop. Pedestrian crosswalks and traffic signals will be installed at the intersections of 18th and Illinois streets and 19th and Illinois streets. 

Muni logo
San Francisco Public Works logo
Contact Information
Peter Gabancho, Project Manager
Erin McMillan, Public Information Officer