Route availability
![With its relatively high axle load, the Class 67 locomotive has somewhat limited Route availability of 8](/Images/godic/202502/08/67028_at_Kings_Cross_15907.jpg")
![A class 86/2, no. 86 252 at Birmingham New Street railway station. This class has a Route availability of 6.](/Images/godic/202502/08/86252_Birmingham_New_Street5907.jpg")
![A class 37 in British Rail large logo livery at Muir of Ord railway station, 1988 with a medium Route availability of 5.](/Images/godic/202502/08/Muir_of_Ord_railway_station_in_19885907.jpg")
![Class 14 no. D9526 (as preserved), at Williton on the West Somerset Railway a low axle load and less limited R.A. of 4.](/Images/godic/202502/08/Wiliton_D9526_double_headed5907.jpg")
Route Availability (RA) is the system by which the permanent way and supporting works (bridges, embankments, etc.) of the National Rail network of Great Britain are graded. All routes are allocated an RA number between 1 and 10.
Rolling stock is also allocated an RA (again between 1 and 10) and the RA of a train is the highest RA of any of its elements. 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. (When considering the operation of trains the loading gauge must also be considered.)