[2] The designation of S Shuttle is also given to trains at other hours and locations, most commonly to those which run service before and after San Francisco Giants and Golden State Warriors games to provide additional capacity to Oracle Park and Chase Center respectively.

[4] (The S Castro Shuttle designation continued to be used for extra service to AT&T Park on San Francisco Giants game days.)

[9] However, the three-car set proved unreliable, and perennial rolling stock shortages caused the shuttles to be frequently cancelled in favor of branch line service.

The revamped service, which was modeled after similar Hillway shuttles on the N Judah line, ran during weekday morning rush hours.

S Shuttle service frequency was increased, as three other lines no longer entered the subway; two- and three-car trains operated between West Portal and Embarcadero on 6–9 minute headways.

[2] Rail service was re-replaced with buses on August 25 due to issues with malfunctioning overhead wire splices and the need to quarantine control center staff after a COVID-19 case.