T Third Street
| Company type | Light rail service |
|---|---|
| Industry | Public transportation |
| Founded | January 13, 2007 |
| Headquarters | San Francisco , United States |
Area served | San Francisco, California |
| Owner | San Francisco Municipal Transportation Agency |
| Website | www |
The T Third Street line is a Muni Metro light rail service operating on San Francisco's eastern corridor, extending from to . It predominantly runs within exclusive median lanes along Third Street before transitioning into the Central Subway near the downtown area. The route includes 22 fully accessible stops, with most surface portions traveling in dedicated lanes, except for two segments shared with other traffic.
Initial limited operations commenced in January 2007, with full-scale service launching in April of the same year. On January 7, 2023, the route was altered north of to traverse through the Central Subway, reaching . This line marked the first expansion of the Muni Metro network since the introduction of the N Judah line in 1928.
Route
The T Third Street line begins at its northern endpoint, Chinatown station, located within the Central Subway. From there, trains head south beneath Stockton Street to reach Union Square/Market Street station, providing connections to Powell Street station as it bypasses the Market Street subway. The tunnel continues under 4th Street to serve Yerba Buena/Moscone station in the SoMA neighborhood before emerging near the Interstate 80 bypass at 4th and Brannan station. After crossing existing N line tracks at 4th and King Streets, the line proceeds southward along 3rd Street. Plans include additional short-turn trips between Chinatown and Mission Bay Loop.[1][2] The route passes through Mission Bay within a dedicated median lane, stopping at Mission Bay Loop between 18th and 19th Streets—a facility used for turning trains around or providing service during events at Chase Center.
Heading further south through Dogpatch and spanning Islais Creek, the line enters the neighborhoods of Bayview and Hunters Point. Here, it operates alongside regular traffic for a stretch between Kirkwood Avenue and Shafter Avenue before returning to exclusive lanes. A wye located at Armstrong Avenue allows for occasional short-turn maneuvers. Crossing over the U.S. Route 101 freeway where Third Street transitions into Bayshore Boulevard, the line continues along the median until reaching its southern terminus at Sunnydale station in Visitacion Valley.
Service
Operating daily, the T Third begins service at 5 a.m. on weekdays, starts at 6 a.m. on Saturdays, and from 8 a.m. on Sundays, running until 1 a.m. During hours when trains are not running, overnight coverage is provided by the bus route. On weekends before rail operations commence, the T Third Street Bus service operates from 5 a.m., closely mirroring the rail alignment but utilizing surface streets where dedicated rail corridors exist.
Background
Historically, streetcar service ran along Third Street and its southern extensions under Market Street Railway until 1941. After repaving projects enabled bus replacements, streetcar operations ceased. The bus route numbered 15 Third Street was discontinued following the introduction of light rail service.
Construction
Plans for this line emerged in the late 1980s as part of redevelopment efforts in Mission Bay. Known as the Third Street Light Rail Project during construction in the mid-2000s, testing began in summer 2006. Limited passenger service started on January 13, 2007, with full operations commencing April 7 that year. Initially operating between Castro and Sunnydale stations, after June 30, 2007, it was interlined with the K Ingleside line via downtown tunnels to form a continuous route from Balboa Park to Visitacion Valley.
The Mission Bay Loop project introduced a short-turn loop utilizing segments of 18th, Illinois, and 19th Streets to support operations alongside the Central Subway. Although initially designed in 1998, funding delays postponed construction until a $3.5 million contract was awarded in 2014. Work began in July 2016 and concluded in 2019. Additionally, there is a proposed loop at 25th and Illinois aimed at improving short-line frequencies between Downtown and Dogpatch.
Subsequent Modifications
The segment of the underground line located west of Castro station was closed between June 25 and August 24, 2018, as part of the Twin Peaks Tunnel closure. Following this, on August 25, 2018, Muni permanently implemented two-car trains on the K/T line, which had been utilized east of Castro during the shutdown period. The line experienced another closure from January 22 to April 1, 2019, to facilitate the construction of a new platform at UCSF/Mission Bay station. In April 2019, SFMTA eliminated unscheduled short turns that had been causing irregular service patterns in the Hunters Point-Bayview and Visitacion Valley areas.
On March 30, 2020, due to the COVID-19 pandemic, Muni Metro transitioned to bus operations. Rail service was reinstated on August 22 with adjusted routes aimed at improving subway reliability; specifically, the T Third Street and M Ocean View lines were combined between Sunnydale station and Balboa Park station. Nevertheless, just three days later on August 25, rail service was suspended once again because of overhead wire splice failures and quarantine measures affecting control center personnel. Service on the Embarcadero–Sunnydale portion of the T Third Street line resumed on January 23, 2021. Prior to this reopening, temporary traffic modifications at the 4th Street bridge over China Basin—including establishing a southbound transit-only lane and eliminating a northbound turn lane—resulted in a 60% reduction in delays. On May 15, service was extended back to West Portal and once more through-routed with the K Ingleside line.
In January 2021, Muni introduced the 15 Bayview-Hunters Point Express bus route, which provides local stops within Bayview–Hunters Point east of Third Street and limited stops running parallel to the T line along Third Street.
Central Subway
The project's second phase, known as the Central Subway, links SoMa with Chinatown through Union Square. Voter approval came in 2003 with route alignment finalized by 2008; construction commenced in 2012. After experiencing delays, it officially opened on November 19, 2022, initially operating weekend shuttle service between and . Complete service began on January 7, 2023, when the T Third Street line was redirected through the Central Subway. Service frequencies are every 10 minutes on weekdays and every 12 minutes during weekends. Additionally, special shuttle trains marked "S Mission Bay" run between and during events held at Chase Center.
The Central Subway was closed from February 26 to March 14, 2025, to address water leakage issues at Chinatown station. During this interval, T Third Street service was combined with K Ingleside operations.
| Template:T Third Street (Initial Alignment) | Template:T Third Street (2007–2021) | Template:T Third Street (2021–) |
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Station listing
Every station along this route features elevated platforms, which removes the necessity for the adjustable steps found on other Muni Metro lines.
| Station | Neighborhood | Additional Muni Metro lines |
Remarks and Connections |
|---|---|---|---|
| Disabled access Template:Munis | Chinatown | ||
| Disabled access Template:Munis | Financial District | Template:Rint Template:Rint Template:Rint Template:Rint Template:Rint Template:Rint (at Template:Munis) |
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| Disabled access Template:Munis | SoMa |
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| Disabled access Template:Munis | Template:Bus icon Muni: Routes 15, 30, and 45 | ||
| Disabled access Template:Munis | Mission Bay, San Francisco | Template:Rint |
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| Disabled access Template:Munis | |||
| Disabled access Template:Munis |
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| Disabled access Template:Munis | |||
| Disabled access Template:Munis | rowspan="2" | Dogpatch, San Francisco | Template:Bus icon Muni: Routes 15, 48, and 55 | |
| Disabled access Template:Munis | Caltrain’s nearby 22nd Street station offers both Express and Local service options | ||
| Disabled access Template:Munis | rowspan="10" | Bayview-Hunters Point | ||
| Disabled access Template:Munis | Served by Muni bus routes: 15, 19, and 44 | ||
| Disabled access Template:Munis | Muni bus lines: 44 and 54 operate here | ||
| Disabled access Template:Munis | Accessed by Muni bus route: 54 | ||
| Disabled access Template:Munis | Served by several Muni bus routes including 15, 23, 24, 44, and 54 | ||
| Disabled access Template:Munis | Muni bus route: 54 serves this station | ||
| Disabled access Template:Munis | Accessible via Muni bus route: 54 | ||
| Disabled access Template:Munis | |||
| Disabled access Template:Munis | Served by Muni bus route: 29 | ||
| Disabled access Template:Munis | |||
| Disabled access Template:Munis | rowspan="2" | Visitacion Valley |
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| Disabled access Template:Munis | Served by Muni routes: 9 and rapid variant 9R; also SamTrans routes: 292 and 397 |
