theseaandalifesaver wrote:Has this ever been a safety issue at all? Who controls the movable section of platform?
It has never been a serious safety issue (except when a section doesn't extend or retract).
To add to what railfan said - only at the Times Square Shuttle station (tracks 1 & 3) are the movable platforms operated by the train operator by pushing a button. When leaving the station the platforms retract at the push of a button.
The ones at 14th St are totally automated (but can be controlled manually if they had to be). As the train enters the station there are sensors on the walls that register how many cars there are on the train (at one time trains were less than 10 cars during the overnight and weekend hours and if the train was shorter only a few of the platforms would actually extend). When the train is stopped at the "S" stopping mark at the front of the platform, a relay triggers the controls and the platforms extend. There is always a short delay for this action to happen and the conductor keeps the doors closed until the platforms extend and lock into place and a light goes on. After a short time the light goes off meaning that the platforms are now unlocked and will retract as the train leaves. The conductor closes the doors and the train leaves very slowly. As the a train car body moves it nudges the movable platform and it snaps back into the retracted position. There is a special signal at the end of the platform which will not clear until all the moving platforms retract.
At 14th St if the train operator upon entering the station goes past the prescribed stopping point (even by a few inches) then the platforms will not extend. This allows for situations where the train is not in passenger service and is just passing thru the station. If the train is in passenger service and the platforms don''t extend then all that can be done is to have the train continue to the next express station and passengers then have to take an uptown train back.
At the old South Ferry station it worked basically the same as 14th St although there were manual controls in the dispatachers office on the platform.