Indian Broad Gauge measures 1,676 millimetres, equivalent to 5 feet 6 inches, between the inner faces of the two rails.
It is wider than the 1,435 mm standard gauge used in many countries.
Indian Railways has progressively converted many metre-gauge and narrow-gauge routes to broad gauge under its gauge-conversion programmes.
The wide gauge provides stability and allows the operation of large passenger coaches, heavy freight trains and powerful locomotives.