K Ingleside

The K Ingleside is a light rail line of the Muni Metro system in San Francisco, California. It mostly serves the West Portal and Ingleside neighborhoods. Opened on February 3, 1918, it was the first line to use the Twin Peaks Tunnel.
Route description.
The K Ingleside line stops at concrete boarding islands in the middle of the street next to the tracks. Some stops have raised platforms for accessibility. Stations between West Portal and Embarcadero are only served by the outbound K. But, not the inbound K, as it switches to T at West Portal.
Operation.
The K Ingleside begins service at 5 a.m. on weekdays, 6 a.m. Saturdays and 8 a.m. Sundays, with the end of service around 12:30 a.m. each night. Trains on the weekdays are scheduled to come every 10 minutes. Trains on the weekends are scheduled to come every 12 minutes.
History.
Municipal Railway.
The San Francisco Municipal Railway (Muni) opened its K line along with the Twin Peaks Tunnel on February 3, 1918. The line ran from St. Francis Circle station along West Portal Avenue, through the tunnel, along Market Street to Van Ness Avenue (joining the J Church at Church Street). And along existing tracks on Van Ness Avenue to Pine Street. On June 1, 1918, the J and K lines were removed from Van Ness Avenue and went further along Market Street to a loop at the Ferry Building.
Changes in 1980s.
More changes to the service route followed until finally on December 17, 1980. It was when the K line was light rail operated, with service from Embarcadero Station to Balboa Park, on weekdays only. Weekend service continued to use PCC cars until September 1982. This was when the Muni Metro became fully operational.
Changes in 2000s.
From February 2001 to June 7, 2003, K Ingleside service was cut back to St. Francis Circle. It was also replaced by buses on Ocean Avenue for street repaving, and route reconstruction along Ocean Avenue. 
Following service changes on June 30, 2007, the K Ingleside and the T Third Street lines were combined inside the Market Street subway tunnel. Though keeping their line designations, resulting in an upside-down, horseshoe-shaped route from Balboa Park to Bayshore and Sunnydale. At West Portal Station, inbound K trains heading towards downtown change their signs to the T line; at Embarcadero Station, T trains heading into downtown change signs to the K line.