Facing and trailing


Facing or trailing are railway turnouts in respect to whether they are divergent or convergent. When a train traverses a turnout in a facing direction, it may diverge onto either of the two routes. When travelled in a trailing direction, the two routes converge onto each other.

History

In the early history of railways in Britain, when signalling and interlocking were primitive, and staff were inexperienced, facing turnouts were a hazard, because a train travelling at high speed could be accidentally switched into a slow speed divergence or dead end. Facing turnouts were therefore banned, except when absolutely necessary. However, facing turnouts cannot be avoided where there are crossing loops on single lines.
With the widespread availability of electrically-interlocked signalling in modern times, the rule against facing turnouts has been relaxed.

Diamond crossings

Fixed diamond crossings count as trailing points in both directions, although in very exceptional circumstances such as propelling a train in reverse over fine angle diamond crossings they can derail wagons as they bunch up.
Switched diamonds, which contain two stub turnouts in disguise, count as facing turnouts in both directions and are also known as moveable angles.

Moveable crossings

Fixed V-crossings are trailable in both directions. Moveable crossings are effectively facing in both directions and must be correctly aligned.

Stub switches

Stub switches are effectively facing in both directions and must be correctly aligned.

Double junctions

s are now configurable in a number of different ways, whereby the number of facing and trailing turnouts vary.

Goods siding

The goods siding on a double line uses two trailing points and a diamond. It can be shunted by trains in either direction.
This was widely done in New South Wales, though later on the diamond crossing was replaced with a pair of ladder crossovers; such as: