High Quality Content by WIKIPEDIA articles! A dual-gauge or mixed-gauge railway has railway track that allows trains of different gauges to use the same track. Generally, a dual-gauge railway consists of three rails, rather than the standard two rails. The two outer rails give the wider gauge, while one of the outer rails and the inner rail give a narrower gauge - one of the three rails is common to all traffic. This configuration is not to be confused with the electric third rail.