Muni Metro is a light rail system serving San Francisco, California, United States. Operated by the San Francisco Municipal Railway (Muni), a part of the San Francisco Municipal Transportation Agency (SFMTA), Muni Metro served an average of 157,700 passengers per weekday in the fourth quarter of 2019, making it the second-busiest light rail system in the United States. Five services – J Church, K Ingleside, L Taraval, M Ocean View, and N Judah run on separate surface alignments and merge into a single east-west tunnel, the Market Street subway. The T Third Street uses a north-south tunnel downtown, the Central Subway. The supplementary S Shuttle service operates within the Market Street subway and Twin Peaks Tunnel. Muni Metro operates a fleet of 151 Breda high-floor light rail vehicles (LRVs), which are currently being replaced by a fleet of 249 Siemens S200 LRVs. The system has 117 stations, of which 63 (54%) are accessible. Muni Metro is one of the surviving first-generation streetcar systems in North America. The San Francisco Municipal Railway was created in 1909 and opened its first streetcar lines in 1912. Five of the current lines were added in the following decades: the J in 1917, the K (including the Twin Peaks Tunnel) in 1918, the L in 1919, the M in 1925, and the N in 1928. The other Municipal Railway streetcar lines, and those of the privately owned Market Street Railway, were converted to buses in the 1920s to 1950s, but these five lines were retained as streetcars because of their private rights of way. The system was converted to light rail, with larger US Standard Light Rail Vehicles, in the late 1970s and early 1980s. This included the opening of the Market Street subway as well as an extension of three lines to Balboa Park station. An extension along The Embarcadero to the Caltrain terminal at 4th and King Street opened in 1998. The T Third Street line opened in 2007, serving the southeastern portion of the city. The Central Subway, with three new subway stations and one new surface station opened on November 19, 2022. History Beginnings The first street railroad in San Francisco was the San Francisco Market Street Railroad Company, which was incorporated in 1857 and began operating in 1860, with track along Market Street from California to Mission Dolores. Muni Metro descended from the municipally-owned traditional streetcar system started on December