Railway platform height

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.

Differences in platform height (and platform gap) can pose a risk for passenger safety. Differences between platform height and train floor height may also make boarding much more difficult, or impossible, for wheelchair-using passengers and people with other mobility impairments, increasing station dwell time as platform or staff are required to deploy ramps to assist boarding. Platform ramps, steps, and platform gap fillers together with hazard warnings such as "mind the gap" are used to reduce risk and facilitate access. Platform height affects the loading gauge (the maximum size of train cars), and must conform to the structure gauge physical clearance specifications for the system. Tracks which are shared between freight and passenger service must have platforms which do not obstruct either type of railroad car.

To reduce construction costs, the platforms at stations on many railway systems are of low height, making it necessary for passenger cars to be equipped with external steps or internal stairs allowing passengers access to and from car floor levels. When railways were first introduced in the 19th century, low platforms were widely used from the 1880s, especially in rural areas, except in the United Kingdom. Over the years, raised platforms have become far more widespread, and are almost universal for high-speed express routes and universal in cities on commuter and rapid transit lines. Raised platforms on narrow gauge railways can prevent track gauge conversion to standard gauge or broad gauge.