A single track railway
is one where traffic in both directions shares the same track. Single track is normally used on lesser used rail lines, often branch lines
, where the traffic density is not high enough to justify the cost of building double tracks
Single track operations
If a single track line is designed to be used by more than one train at a time, it will have passing loops
(short stretches of double track) at intervals along the line to allow trains running in different directions to pass each other. Although in some circumstances (such as the Abbey Line
in Great Britain) a single track line may work under the "one train working" principle without passing loops where only one train is allowed on the line at a time.
On single track lines with passing loops, measures must be taken to ensure that only one train in one direction can use a stretch of single track at a time, as head-on collisions
are a particular risk. Some form of signalling system
is required. In traditional British
practice (and countries using British practice), single track lines were operated using a token system
where the train driver had to be in possession of a token in order to enter a stretch of single track. Because there was only one unique token for each stretch of single track, it was impossible for more than one train to be on it at a time. This method is still used on some minor lines. In the early days of railways in North America
it was common to rely upon simple timetable......