Single-line working

However, when a section of line which is not normally bi-directional has to be used in both directions, special procedures are needed to ensure safe operation.

[1] The worst safety risk is a head-on collision between two trains travelling in opposite directions, but there is also the risk of a rear-end collision if two trains travel simultaneously over the line in the unsignalled direction.

Because signals are provided for travel in this direction, the Pilot has only to explain to the driver what is taking place.

If there is an Automatic half-barrier (AHB) crossing under local control on the route, the driver may only pass over it if there is a handsignaller displaying a green flag or lamp to them.

Once they are in possession of the Single line working ticket and has received authority to move from the Pilot, the driver must obey the signals and may proceed at linespeed if conditions allow.

An example of single-line working: maintenance of way crews are working on two tracks (left) of a three-track line in the Czech Republic while a passenger train passes on the third track (right) in 2011.