The Oakland Wye is an underground flyingwye junction in downtown Oakland, California which serves the Bay Area Rapid Transit (BART) system. Trains can switch between (a) the northbound Richmond or Antioch lines (first station: 12th Street Oakland City Center, underground), (b) the westbound San Francisco lines (first station: West Oakland, elevated), and (c) the southbound Berryessa or Dublin/Pleasanton lines (first station: Lake Merritt, underground).[1][2][3][4]: 45–46 The Oakland Wye is the center of the BART system (all mileposts measure distance from the wye),[5] and is a bottleneck for the whole system because every regularly scheduled BART train (except for the Oakland Airport Connector and eBART) passes through it.[1][6]