Usually, TBMs bore the deep-level tunnels between stations, while the station vaults are dug out manually and contain both the tracks and the platform. The track tunnels adjoining the ten stations' island platforms were built with tunnel boring machines (TBMs), and the island platforms were actually located in a separate vault between the two track tunnels. The platform 'doors' are actually openings in the station wall, which supports the ceiling of the platform. The first stations in the world with platform screen doors were the ten stations of the Saint Petersburg Metro's Line 2 that opened between 19. Unlike Shute's invention, the entire platform gate was movable, and was to retract upward. Pneumatic cylinders with pistons would be used to raise the gates above the platform when a train was in the station. The invention provided for spaced guides secured to a tunnel's side wall, with 'a gate having its ends guided in the guides, the ends and intermediate portions of the gate having rollers engaging the side wall'. In 1917, Carl Albert West was granted a patent for 'Gate for subrailways and the like'. The invention consisted of 'a fence for railway platform edges', composed of a series of pickets bolted to the platform edge, and vertically movable pickets that could retract into a platform edge when there was a train in the station. Shute of Boston was granted a patent for 'Safety fence and gate for railway-platforms'. The idea for platform edge doors dates as early as 1908, when Charles S. 'Horizontal lift' style doors at Lomonosovskaya station on the Saint Petersburg Metro, the first type of screen doors in the world.

Westinghouse monitor driver