Rail track gauge

Smallest distance between a pair of rails measured between the inside surfaces of the rail heads. More precisely, a gauge consists of a set of rules including a reference contour and its associated calculation rules, allowing the definition of the outer dimensions of the vehicle and the space to be cleared by the infrastructure. Statistics on rail track gauge distinguish between broad/large (more than 1 435 mm), standard (1 435 mm) and narrow (less than 1 435 mm) gauge railway track. More precisely, a standard gauge is not less than 1 435 mm on straight sections, and not more than 1 470 mm on curves, including gauge widening.