SEPTA's M-4 transit car door experience
D.J. Gibbone, Jenee Malloy, Norman Vutz · 2002
Shortly after SEPTA's new M-4 cars were introduced into service, two modifications to the door system were found to be necessary. The background for the modifications, interim actions, and final implementation are described. One modification involved addition of sensors on the cars and targets at station platforms to enable door operation only with a platform adjacent. The design of this change was purely a SEPTA effort. The second modification involved a total change-out of the door actuation hardware and its associated controls to obtain acceptable reliability.