RA stands for Route Availbility which is a measure of a rail vehicles axle load upon the track. The higher the axle load, the higher the vehicles RA on a scale from 1 to 10 (1 being very light to 10 being very heavy). Every Network Rail route has its own RA number in addition to railway vehicles and generally speaking (there are exceptions) no vehicle with a higher RA number than the route RA may travel on the route without special authorisation.Starkey7 wrote:What is RA5?!
The Oban branch has a route RA of 5, thus only vehicles whose vehicle RA is 5 or under may travel along it, i.e. all passenger vehicles and locos such as the class 37, 55 or IC125. Heavier locos like the class 66 (which are vehicle RA7) are barred from this route as thier vehicle RA is higher than the route RA.
Hope I have explained things in a simple manner.