Antioch–SFO/Millbrae line

When the SFO/Millbrae extension opened on June 22, 2003, BART extended the Pittsburg/Bay Point–SFO/Millbrae line to Millbrae but bypassed San Francisco International Airport station (SFIA). BART rerouted this line to SFIA in place of the Dublin/Pleasanton line on February 9, 2004, with service extended to Millbrae outside of weekday peak hours. San Mateo County is not a member of the San Francisco Bay Area Rapid Transit District, so SamTrans funded the county's BART service. When the extension's lower-than-expected ridership caused SamTrans to accrue deficits, BART agreed to SamTrans' request to operate only the Dublin/Pleasanton line south of Daly City effective September 12, 2005.

SamTrans and BART reached an agreement in February 2007 in which SamTrans would transfer control and financial responsibility of the SFO/Millbrae extension to BART, in return for BART receiving additional fixed funding from SamTrans and other sources.[10] In January 2008, BART re-extended the line to SFIA at all times, and in September 2009, trains were further extended to Millbrae on evenings and weekends. As of February 10, 2020, the Antioch line again terminates at SFIA at all times.[11] Antioch line and SFO-Millbrae line trains are interlined on Sundays, with no transfer required at SFIA.[12]

BART to Antioch, named during construction and commonly known as eBART (East Contra Costa BART Extension),[19][20][21] is a diesel multiple unit (DMU) light rail branch line of the Bay Area Rapid Transit (BART) system in eastern Contra Costa County, California, United States. Service starts at Pittsburg/Bay Point station and extends to Antioch station.

Trains and tracks for the portion of the Antioch – SFO/Millbrae line between Antioch and Pittsburg/Bay Point are incompatible with those of the main BART rapid transit system, making it impossible for trains to move between the two systems;[22] instead, passengers transfer via a cross platform interchange at an auxiliary BART stop at Pittsburg/Bay Point – the BART to Antioch platform is accessible only via an intra-station ride from the main station to this auxiliary stop. The first extension proceeds 10.1 miles (16.3 kilometres)[23] east along the State Route 4 corridor to the city of Antioch[24] at a Hillcrest Avenue station. Revenue service began on May 26, 2018.[25]

The BART map does not differentiate between this service and the remainder of the Antioch–SFO/Millbrae line.[26][27] There is a notation on the map published in stations showing a transfer is required, but not on the schedule or map brochures distributed to the public.[28]