San Francisco Municipal Railway

The San Francisco Municipal Railway, commonly known as Muni, is the public transit system for the city and county of San Francisco, California. In 2006, it served 46.7 square miles (121 km²) with an operating budget of about $700 million. In terms of ridership, Muni is the seventh largest transit system in the United States, with 210,848,310 rides in 2006. Muni is an integral part of public transit in the City of San Francisco, operating 365 days a year and connecting with regional transportation services, such as Bay Area Rapid Transit (BART), SamTrans, and AC Transit. Its network consists of 54 bus lines, 17 trolley bus lines, 7 light rail lines (known as the Muni Metro), 3 cable car lines, and a heritage streetcar line known as the F Market & Wharves. Many weekday riders are commuters, as the daytime weekday population in San Francisco exceeds its normal residential population. Muni shares four metro stations with BART, which can lead to confusion amongst visitors. Travelers can connect to San Francisco International Airport and Oakland International Airport via BART.

(from wikipedia)