Bay Area Rapid Transit (BART) is a rapid transit system serving the San Francisco Bay Area in California. BART serves 50 stations along six routes and 131 miles of track, including a 9-mile (14 km) spur line running to Antioch, which uses diesel multiple unit vehicles, and a 3-mile (4.8 km) automated guideway transit line serving San Francisco Bay Oakland International Airport. With an average of 160,400 weekday passengers as of the fourth quarter of 2023 and 48,119,400 annual passengers in 2023, BART is the seventh-busiest rapid transit system in the United States.