When the Muni Metro subway opened with newfangled light rail vehicles, one and two-car trains were coupled together into three and four-car trains at the tunnel portals. The tunnel was not computer-controlled yet, limiting how fast and how closely trains can run, so run longer trains.
Well, that was the plan anyway. The timing didn't always work, nor did the couplers.
The second-generation trains and the first-generation tunnel control system increased capacity to 40 trains per hour, with no need to couple trains together. – Circa 1980 Public Utilities Commission Photographer | SFMTA Photo Archive
