Two-third rule
Encyclopedia
For safety reasons, railway lines are assessed and a speed limit
imposed on trains running on that line. Many factors can affect the speed limit of a particular line including the state of the track, the curvature of the track, the number of stations, the individual features of stations or junctions and the stopping distances of trains running on that track are examples of such factors.
On some passenger lines in southern England, speed limits are higher than they might be elsewhere because the trains which operate on these tracks are usually electric multiple units (EMUs) which are capable of slowing down much quicker than many other trains, particularly freight trains.
On such tracks, the two-third rule applies to freight trains. The two-third rule means that the speed limit for a freight train is automatically two-thirds of the speed for an EMU.
For example, the Dartford Loop Line
has a speed limit of 60 mph for EMUs between Lee
and Crayford
. A freight train on this track is therefore limited to two-thirds of 60 mph, ie 40 mph.
Speed limit
Road speed limits are used in most countries to regulate the speed of road vehicles. Speed limits may define maximum , minimum or no speed limit and are normally indicated using a traffic sign...
imposed on trains running on that line. Many factors can affect the speed limit of a particular line including the state of the track, the curvature of the track, the number of stations, the individual features of stations or junctions and the stopping distances of trains running on that track are examples of such factors.
On some passenger lines in southern England, speed limits are higher than they might be elsewhere because the trains which operate on these tracks are usually electric multiple units (EMUs) which are capable of slowing down much quicker than many other trains, particularly freight trains.
On such tracks, the two-third rule applies to freight trains. The two-third rule means that the speed limit for a freight train is automatically two-thirds of the speed for an EMU.
For example, the Dartford Loop Line
Dartford Loop Line
The Dartford Loop Line is one of three lines linking London with Dartford in Kent, England. It lies to the south of the other two: the North Kent Line and the Bexleyheath Line.-Construction:...
has a speed limit of 60 mph for EMUs between Lee
Lee railway station
Lee station is a suburban railway station on Burnt Ash Hill in Lee in south-east London, England, between Hither Green and Mottingham on the Dartford loop . It was opened by the South Eastern Railway in 1866...
and Crayford
Crayford railway station
Crayford railway station is in the London Borough of Bexley in south-east London, in Travelcard Zone 6. The station and all trains serving it are operated by Southeastern....
. A freight train on this track is therefore limited to two-thirds of 60 mph, ie 40 mph.