This page lists every locomotive allocated a TOPS classification and all modern traction ( e.g. diesel , electric , gas turbine , petrol ) stock used on the mainline network since 1948 ( i.e British Railways and post-privatisation ) . This page lists every locomotive allocated a TOPS classification and all modern traction ( e.g. diesel , electric , gas turbine , petrol ) stock used on the mainline network since 1948 ( i.e. British Railways and post-privatisation ) .