Route Availability.

On former LNER lines locos were restricted as to where they could run by their axle weight. Pacifics, V2s and the W1 with around 22 tons axle loads were the highest rated and classified as RA9.

That said, and with the possible exception of the GCR, how could it be that such heavy locos run on preservation lines that obviously only permitted a lower axle load in former BR times?

 

I suspect the answer is that many preserved branch lines have been relaid to a far higher standard.

On a similar note, the GWR had a colour-coded route availability scheme. What did the LMS and Southern do? Did BR have a unified scheme?

 

A combination of restricted speed (Heritage lines should not allow running faster than 25 mph) and the higher standard that some lines adopt. When Steamport was active in Southport it was often said that the museum line was better than the siding connecting the museum to the national network.

 

What's now the Mid Hants was one of few single track secondary routes cleared for the heaviest axle loads, so they've got no explaining to do!

Forces, such as hammer blow, imparted to the track, are significantly less at 25mph than at the higher speeds often employed during a line's commercial existence, which covers some cases, plus many lines have upgraded track and infrastructure since preservation, though there are concerns expressed that the civil engineering here and there really isn't suitable for some of the heavier locos regularly traversing them.

During Southern days, the restriction on the Horsham to Guildford line (traditionally a haunt of locos such as D1s,D3s and later, M7s and 2MTs) was temporarily eased in order that 'Schools' class loco 'Cranleigh' could be named at it's 'home station'. I don't know from which end, or at what speed the loco was operated, but I'd guess 'from Guildford' and 'low', in that order.

As an aside, I seem to recall that 'Evening Star's' first preservation era jaunt on the West Somerset was only possible with restictions on coal carried in the tender to keep the axle load acceptable.

 

Same when the 8F first arrived at the SVR: no more than 4 1/2 tons of coal and2500 gallons of water.

 

On the NYMR, Track relaying with Sleepers per length increasing from 24 to 26 or 28.
Heavier rail, Deeper ballast and centralising the track across the formation, especially on bridges to reduce outward thrust on the structures.

 

Likewise on the mainline: the Black 5 used on the Cambrian Coast was limited on coal carried, stopping to refuel at Porthmadog on the outward journey.....