This project provides upgrades to BART’s 34.5kV subtransmission system including replacement of the left circuit cable section between ACO and ASL traction power substations (TPSS), ASL and AWA traction power switching station, and AWA to ABF TPSS. Both the left and right circuits will be replaced between the LAA and AHA, AHA to ASH, ASH to AAY, and AAY to AUC TPSS. Concurrent with the subtransmission circuit replacement, installation of isolation disconnect switches at ABF, AHA, ASH, the future AEY site, AAY, and AUC substation locations. Additionally, 288 and 144 strand fiber optic (FO) cable is to be installed connecting the train control rooms (TCR) at all passenger stations from ACO to AUC including the Hayward Yard TCR.