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's rapid transit system operates five routes on of line, with 44 stations in four counties. With an average of 422,490 weekday passengers, 211,288 Saturday passengers, and 158,855 Sunday passengers in September 2014, BART is the fifth-busiest heavy rail rapid transit system in the United States.