Platform screen doors (PSD) and platform edge doors (PED) in railway stations or subway stations can separate platforms from trains. They are relatively new additions to many metro systems worldwide, some of which have been retrofitted into established systems. They are widely used in Asian and European subway systems.

The PSD is installed at the edge of the subway station platform to separate the running area from the platform waiting area, and is equipped with a sliding door continuous barrier corresponding to the train door that can be opened and closed by multipole control. The full height and closed door body is called screen door; Half height or full height of the door but not closed is called safety door.