Mind The Gap

Mind the Gap is a warning to train passengers to remind them of the sometimes significant gap between the train door and the station platform.

Introduction
It was first introduced in 1969 by the London Underground. The phrase is associated closely enough with the London Underground that the organization sells T-shirts with the phrase imposed on a London Transport symbol.

Information
Some station platforms on the London Underground are curved. Since the cars are straight, the distance from the platform to the car at certain points is greater than normal, and the phrase "mind the gap" is painted in capital letters along the edge of such platforms. A recorded announcement is also played whenever a train arrives at a station, consisting of "mind the gap" repeated several times, followed by "stand clear of the doors, please," and "this train is now ready to depart".

The recording is also used where platforms are of a non-standard height. Deep-level tube trains have a floor height around 20 cm less than cut-and-cover line trains. Where these trains share platforms, for example some Piccadilly line (deep level) and District line (cut-and-cover) stations, the platform is built as a compromise between the two. The "mind the gap" warning is used in this situation as well.