Facing and trailing

Facing and Trailing are terms used to describe railway turnouts in respect to whether they are divergent or convergent.

Turnouts facing and trailing.

History

In the early history of railways in Britain, when signalling and interlockings were primitive, and staff were inexperienced, facing turnouts were a hazard, because they could switch a train travelling at high speed into a slow speed divergence or dead end. Facing turnouts were therefore banned, except when absolutely necessary. Facing turnouts cannot be avoided on single lines and their crossing loops.

Diamond crossings

Fixed diamond crossings (with no moving parts) count as trailing points in both directions, although in very exception circumstances such as propelling a train in reverse they can derail wagons as they bunch up.

So-called switched diamonds, which contain two stub turnouts in disguise, count as facing turnouts in both directions.

Recent times

With the widespread availibility of electrically interlocked signalling in modern times, the rule against facing turnouts has be relaxed.