The 31BX Balboa B Express runs during weekday peak periods only.
Balboa and 12th Avenue via Balboa, Turk, Masonic, Geary, Presidio, Bush, Sansome, California, Davis to Pine.
Express Area: No stops after Presidio and Geary until Montgomery.
Davis and Pine via Davis, Pine, Presidio, Geary, Masonic, Turk, Balboa to 12th Avenue.
Express Area: No stops after Montgomery until Presidio and Geary.