Geograph - photograph every grid square

A train, heading east towards South Shields, stands at Platform 1 just behind the photographer as can be seen in the mirror. Tyne & Wear Metro trains are operated under 'driver only' conditions, which means that the driver is responsible for train dispatch from stations. The square convex mirror enables the train driver to see the entire platform behind and is for safety purposes to determine that everyone has boarded before closing the doors.

When the train is ready to depart, the driver checks that it is safe to close the doors and starts the door closing sequence by pressing a 'door tone' button in the cab. This activates a 3-4 second 'hustle alarm' and a spoken message (“doors closing”) to warn passengers. The driver is then required to check the platform again before pressing the 'door close' button in the cab. When all the doors are automatically detected as fully closed and locked, a safety circuit (called the traction interlock circuit) is made (i.e. completed) by means of a microswitch associated with each door leaf, and the driver receives a bell sound and a green light in the cab. With the traction interlock made, the driver is then able to release the brakes and apply traction power to depart from the station.
From: Rail Accident Report following 'trap & drag' incident at Jarrow Station, 12 April 2012 Link