Route availability


Route Availability is the system by which the permanent way and supporting works of the railway network of Great Britain are graded. All routes are allocated an RA number between 1 and 10.
Rolling stock is also allocated an RA and the RA of a train is the highest RA of any of its elements. The train must have a route availability lower than or equal to the RA of a line to be allowed to use it. The RA is primarily related to the axle load of the vehicle, although axle spacing is also taken into consideration. In practice it is the locomotive which governs where trains may operate, although many high capacity 4 axle wagons have high RAs when fully loaded.
The system was first devised by the London and North Eastern Railway, and perpetuated by British Rail to ascertain which locomotives can work on which lines throughout the rail network in Great Britain.
Exemptions may be obtained to allow locomotives to operate on lines from which they may otherwise be banned. An exemption might be granted by placing a speed restriction over a weak bridge, for example.

Line calculations

The route availability for a line is calculated by taking into account bridge strength, track condition, structural issues and so on. A route availability of one is the most restricted line, open to possibly one type of locomotive specially designed for it. A route availability of 10 is the most open, usable by any locomotive that fits within the GB loading gauge that has been 'passed' for it.

Vehicle calculations

Route availability for a vehicle is generally based upon its axle loading. That is, how much of the laden weight of the vehicle is distributed on each axle. The more weight on each axle, the higher the RA number, and the more restricted the vehicle is. The uneven weight distribution of the class 28 Co-Bo forced the use of a six-wheel bogie at one end in order to stay within RA 8. For wagons it is normal to have different RAs when running empty and full.
The RA of a locomotive must not exceed the RA of the track except under strictly controlled circumstances.
Thus a locomotive with RA 1 is able to work on any line, although it will have a very light axle loading. An RA 10 locomotive could only work upon an RA 10 line, placing severe restrictions on where it can be used.
If a vehicle has wheels that require significant balance weights, often found on steam locomotives, the dynamic loading resulting in what is termed the hammer blow action may affect the RA of the vehicle.
Network Rail currently gives the allowed axle loadings as follows:
Route AvailabilityAxle Load
RA3≤16.5 tonnes
RA5≤19.0 tonnes
RA6≤20.3 tonnes
RA8≤22.8 tonnes
RA9≤24.1 tonnes
RA10≤25.4 tonnes
EU average≈22.5 tonnes

The information regarding route availability in this article comes from the British Rail Route Availability Guide and the Freight Train Loads Book, both issued in 1969. Several routes will have had their RA numbers changed since that time.
Group NumberMainline ClassesShunters
1Y1401, 03, 04*, 11104, 15097
2158, 220, 222 02, 04*, 05
3
415, 16, 17, 22, 221, 222, 10800
520, 23, 25, 27, 29, 31*, 37*, 43, 55, 18506, 08*, 09, 10, 11, 12
68K, D16/2, 24, 26, 31*, 33, 35, 40, 42, 47*, 48, 50, 52*, 53, 57, 71, 73, 81, 82, 83, 84, 85, 86, 87, 8907, 08*
744, 45, 46, 47*, 52*, 57, 58, 59, 60, 66, 68, 70, 74, 88, 91
828, 67, 7613
9
10

* Depending on sub-class, see individual article for details.
$ Discrepancy with original data.

Historical notes

Before nationalisation the Big Four railway companies had their own classification systems.

Great Western Railway

Each locomotive had a coloured disc painted on the cab side to indicate its route availability:
Disc colourAxle load Axle load Axle load Notes
up to 14 long tons 0 cwt-
Yellow disc14 long tons 0 cwt up to 16 long tons 0 cwt-
Blue discover 16 long tons 0 cwt, up to 17 long tons 12 cwt-
Red discover 17 long tons 12 cwt-
Double red disc22 long tons 10 cwt"King" class only-