Railway platform height is the built height – above top of rail (ATR) – of passenger platforms at stations. A connected term is train floor height, which refers to the ATR height of the floor of rail vehicles. Worldwide, there are many, frequently incompatible, standards for platform heights and train floor heights. Where raised platforms are in use, train widths must also be compatible, in order to avoid both large gaps between platforms and trains and mechanical interference liable to cause equipment damage.
The Yawkey MBTA Commuter Rail station in 2011, with two platform heights: low-level for most cars and a full height platform to accommodate passengers in wheelchairs. This station has since been extensively rebuilt and renamed to "Lansdowne".
A low floor tram platform in Cologne
Haining railway station's platform includes both low and high platforms
Older 200 mm platforms (background) and newer 1,100 mm platforms at Santa Mesa station
A platform gap is the space between a train car and the edge of the station platform, often created by geometric constraints, historic legacies, or use of partially compatible equipment.
A Central line platform at Bank tube station, London, showing the 1-foot (30 cm) gap between the train and the platform edge (delineated by a solid white line).
Significant vertical and horizontal platform gap at University station on the MTR system in Hong Kong
This German regional train (DB class 442) has door-mounted gap fillers
The severe concave platform curvature at 14th Street–Union Square requires gap fillers at regular intervals