The Yellow Line is a Bay Area Rapid Transit (BART) line in the San Francisco Bay Area that runs between Antioch and San Francisco International Airport (SFO). Some morning trains and all trains after 9 pm are extended from SFO to serve Millbrae station when the Red Line is not running. It serves 28 stations in Antioch, Pittsburg, Bay Point, Concord, Pleasant Hill, Walnut Creek, Lafayette, Orinda, Oakland, San Francisco, Daly City, Colma, South San Francisco, San Bruno, and Millbrae. It is the most-used BART line, and the only line with additional trains (between SFO and Pittsburg/Bay Point) on weekdays. It runs for 62.2 miles (100.1 km), making it the system's longest line.
The line is split into two segments. The majority of the line uses the same electric multiple unit trains as the rest of BART, and shares tracks with the four other mainline services. The 8.6-mile (13.8 km) section from Antioch to near Pittsburg/Bay Point station, known as eBART, uses diesel multiple units. A cross-platform transfer between the two modes is made at a dedicated transfer platform east of Pittsburg/Bay Point station. However, the line is shown on maps as one route, and headsigns and station information display the ultimate terminus of the line.