Steam Era Route Availability Categories

I was trying to work out comparative route availability on different lines, and although I have the GW list, I couldn't find any others. I found a partial Network Rail list on Wikipedia (so be careful) but nothing steam age. Would any of you have RA lists for the rest of the big 4? If so may I have a copy?

FWIW this is what I have at the moment.

Route Availability Axle Load Tonnes Tons/Cwt
GW uncoloured 14T
GW Yellow 16T
NR RA3 ≤16.5 tonnes 16T 5cwt
GW Blue 17T 12cwt
NR RA5 ≤19.0 tonnes 18T 14cwt
GW Red 19T 12cwt **
NR RA6 ≤20.3 tonnes 20T
NR RA8 ≤22.8 tonnes 22T 9cwt
GWR double Red 22T 10cwt
NR RA9 ≤24.1 tonnes 23T 14cwt
RA10 ≤25.4 tonnes 25T

** Usually given as > 17.12 and not a King.
19:12 was the usual maximum on red route locomotives,
but some Hawksworth locos were 19:14 and the Bear,
which was not permitted on all red routes, was 20T,

 

Is this any help?
Pat

 

It all helps, thankyou.

 

I have a vague recollection that Holcroft wrote of seeing maps of SECR routes, coloured to indicate weight restrictions. The ex-SER Charing Cross to Dover via Tonbridge line had been re-ballasted and was shown in Red(?), able to take the new L-class with 19¼ ton axle-loading. Other routes including the LCDR main line were in another colour and able to take the E-class with 17½ ton axle-loading. And I think there was a third colour for lines with lower limits.

I am not aware of any other pre-1939 route classifications outside the GWR. But in 1940, the Civil Engineer's Department of the LNER Southern Area (ex-GN/GC/GE lines) devised a system of Route Availability (RA) classes. This was in a situation where WW2 was requiring engines to be assessed for use on lines outside their traditional areas. The LNER's large number of loco classes was no doubt making it very cumbersome and time-consuming to keep track of what could work where.

Part 1 of the RCTS "Locomotives of the LNER" gives details. Routes were classified into 8 groups based on maximum permissible axle-loading. Engine classes were assigned to these groups, but it was not a straightforward check on axle-loading alone. Bending moments were calculated for bridge spans of 10ft and above in increments of 5ft, effectively taking into account weight per foot run as well as axle-loading. The result was that where locos had heavily laden axles close together, as in 8-coupled freight types, they could go into a higher RA class than that indicated by the axle-loading alone.

The initiative was successful and was extended in 1947 to the whole of the LNER, with the RA number henceforth being shown on locos. Because there were a large number of classes in the RA5 (17.50-18.75 t) class, it was split in two and the higher RA classes "moved up" one. See attachment.

BR decided in due course to adopt the LNER system, although I'm not sure that it became network-wide before the 1970s. BR appear to have closed up the RA5/RA6 anomaly that the LNER had introduced in 1947, so for example a 90-ton (22½t axle-load) Class 67 is RA8 rather than RA9. I don't think there are any loco types in the present-day RA9/10, only freight wagons.

Doubtless the weight limits will now be formally defined in metric tonnes rather than imperial long tons, but that makes only a small difference. On-line references indicate that there is an RSSB document that provides chapter and verse for these standards. If any forum member has access to that document, perhaps they could check and amplify.

 

Excellent. Thank you. I'd wondered why my 1958 observers book listed RA classes for LNER and GWR but not the others.
Your post also explains why the LNER O4 is in a heavier RA category than the GWR class for the ROD 2-8-0: that being the only one on both lists in the book.

I've had a bit of a trawl through RSSB documents, but am yet to find the actual calculations. I did find that its now based on the maximum loads imposed by a 100m train on a 50m bridge, so whilst individual axle loading is obviously a significant part of it, its a much more sophisticated and realistic calculation.

To go off topic, something else I discovered in my trawl was a RSSB study of platform heights and offsets to trains. Of 5,671 platforms they evaluated in the national gauging database, just 384 were within the current standard for both height and clearance from the carriage. When you consider the expense that must be involved in changing platform height - and more are too high than too low - it seems that the lot of executives responsible for gauging is not an 'appy one!

Another little snippet from a study of RSSB documents is that "Engineering Requirements for Steam Locomotives and other Heritage Rail Vehicles" is RIS4472 and "Steam Locomotive Operation" is RIS3440. Who says the modern industry lacks a sense of history and humour?

 

"Bridge weight" is often forgotten, or people don't realise about it. A 9F and a Hall aren't that different in length, but the weights are. Yes, a 9F's axle loading is a few tonnes lower than that of a Hall, but there is a lot more overall weight in a similar wheelbase length.

 

Pity we don't use the UIC system. 5 axle load bands A to E; 5 tons per metre bands 1 to 5. No higher maths required.
Pat

 

As is my wont with a topic I haven't found very accessible information for I'm knocking up a web page with what I've discovered. If you're interested its here. https://www.devboats.co.uk/gwdrawings/weightrestrictions.php

 

Just in passing, the Wikipedia article on Great Western Railway Power and Weight Classification currently states that "In 1949, BR decided to adopt the London, Midland and Scottish Railway (LMS) system of power classification for all locomotives." Based on what had been posted here I assume Wikipedia is wrong (surely not!) but I won't change it myself as don't have a book I can use as a citation.

https://en.wikipedia.org/wiki/Great_Western_Railway_Power_and_Weight_Classification

 

I gain the impression that you are confusing Route Availability axle loadings with Power Classification, another thing altogether.

 

I could well be.

 

Mind you there's not much doubt that the LMS mafia at the Kremlin would have been happier to use an LMS route availability scheme, had it not been for the minor drawback that no such thing existed.

 

@Jimc - you might like this image:



Source: "The Sphere" Saturday 06 April 1929. Via https://www.facebook.com/DavidTurnerrailway/photos/10158657620600631

Tom

 

Page 115 and onwards of "Locomotive Adventure" - I'm sure @Jimc has a copy.

"Apart from the question of loading gauge was that of weight restriction. The SE&CR route map showed full strength sections coloured green, which could take engines equivalent in weight to an L class. Blue lines at that time predominated on the map and only engines equivalent in weight to D and E classes could be accepted for running. Branches which could take only special engines were marked in red.

[...]

The Western and Central Sections were not under the same stringency as the Eastern Section in regard to the routes open to their heavy locomotives."
​

The critical matter on the South Eastern section was the matter of boat trains - Victoria to Dover or Folkestone. There were six available routes but only route 1 was a green route. (Victoria via Herne Hill, Orpington and Tonbridge). Somewhat mimicking the more well known situation on the GWR, bridges had been being strengthened over the preceding years, such that by July 1924 the green routes (capable of handling an L class) was increased to routes 1, 2, 5 and 6. (That must have involved strengthening of the line via Catford in London; and via Maidstone East in Kent, leaving just the route via Faversham at "blue" status). The No. 1 boat train route was available for the "Ashfordised" N15 King Arthur by 1 July 1925.

Tom

 

Some of the balancing details of Urie/Maunsel locomotives were singled out by the bridge stress commity.
Hinting that either LSWR/SR design office had not known how to do it or had tried to fool the permanent way department.
The locomotives were balanced /maximized as steam hammers at speed for minimizing locomotive bearing maintenance cost.
I like conspiracy theories and cannot help to think that the Sevenoaks disaster was caused in part or whole by hammering permanent way by Urie/Maunsel 4-6-0s.

 

I think that's probably a conspiracy too far - those locos would have made in total a very small amount of the total used on the line in the lifetime of the p/way in that section.

In the members' section of the SECR Society website is a very interesting diagram showing the state of the p/way over the whole railway. Attached is the section around Sevenoaks. (The accident happened between Polshill Tunnel and Sevenoaks in the down direction, i.e. travelling left to right, the loco finally coming to rest round about milepost 21½).



The diagram shows, from bottom to top:

• The mileage, measured from Charing Cross
• The curvature
• The gradient profile
• The dates laid and rail weights for each individual line
• The names of notable features

It can be seen that in the vicinity of the accident, the track was laid in 1907 with 95lb/yd rail. (Interestingly, the up line in the vicinity was laid with 91¼ lb/yd rail in 1921 - the rail weight seems light for the era). That accords with the description in the accident report (at https://www.railwaysarchive.co.uk/documents/MoT_Sevenoaks1927.pdf) which notes that the measured weights of teh 95lb rail had diminished to:

• Inner rail: 86.2 - 87.9 lb/yd
• Check rail: 92.5 - 94.4 lb/yd
• Outer rail: 83.5 - 85.8 lb/yd

Clearly the p/way was fairly life expired and indeed, given the 1907 relaying date, it was due replacement in 1928 based on the normal 21½ year renewal cycle in use.

Tom

 

Re: Sevenoaks. I believe that the condition of the ballast and drainage was deficient. Not a RA issue per se, but a sign that pure numbers don't tell the whole story.
Pat

 

These days 'Elf 'n' Safety might have something to say about the timber platform that two of the observers are on!

 

Didn't they use beach pebbles rather than actual ballast stones which didn't provide a firm enough anchor for the track?

 

A lot of the beach came from Dungeness. There are pits that had sidings off the Dungeness branch. There used to the remains of the sleepers and a few chairs

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