High Quality Content by WIKIPEDIA articles! Bay Area Rapid Transit (BART) is a rapid transit system serving the San Francisco Bay Area. The heavy-rail public transit and subway system connects San Francisco with cities in the East Bay and suburbs in northern San Mateo County. BART operates five lines on 104 miles (167 km) of track with 44 stations in four counties. With an average weekday ridership of 357,800 passengers, BART is the fifth-busiest heavy rail rapid transit system in the United States.