High-level platform
On a railway, the platform height refers to the height of a railway platform Above Top of Rail (ATR). A related term is "train floor height" which is the height of the floor of the rail vehicle. Worldwide, there are a large number of incompatible standards for platform heights and train floor heights. When raised platforms are in use, the train width must also be compatible, to avoid both large gaps or mechanical interference which causes equipment damage.
Differences in platform height (and platform gap) can pose a risk for passenger safety. Platform ramps, steps, and platform gap fillers together with hazard warnings such as "mind the gap" are used to reduce risk and enable 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 station construction costs, many train systems use a low platform, and require passenger cars with internal stairs up to the train floor.
Buses, trams, trolleys and railway passenger cars are divided into several typical categories.
Typical Algerian platforms are 550 mm (21.7 in) above rail.
The majority of railway systems in Australia use high level platforms with a platform height a small distance below the train floor level. Exception to this include Queensland who have narrow gauge trains and lower platforms, and South Australia who have trains fitted with low level steps to enable the use of low level platforms.
In New South Wales, by 2000, the platform step (the difference between the platform height and the train floor height) had been allowed to grow to a maximum of about 300 mm (11.8 in), which was uncomfortably large. For Sydney's 2000 Olympics, new and altered platforms were designed to match the Tangara trains, which are 3,000 mm (9 ft 10 1⁄8 in) wide, leaving a platform gap of about 80 mm (3 1⁄8 in) and a step height close to zero. This has become the standard for all subsequent platforms and trains in NSW.
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