Re-use / overlapping of headcodes

[Wilts Wanderer]

If you go back and look at old Working Timetables from the 1970s, 80s etc one thing that often jumps out is the profligate reuse of the same headcode multiple times per day on a given route.

For example, in the 1980 SX WTT, the majority of local trains between Carlisle and Whitehaven are coded 2P59 in BOTH directions!

Just curious - at what point did BR twig the compromise in safety this caused ("hello signaller, this is 2P59 at Wigton... no the down direction...") and mandate that the same headcode not normally be reused within a 12 hour period on a given box or panel area?

 

[RT4038]

If you go back and look at old Working Timetables from the 1970s, 80s etc one thing that often jumps out is the profligate reuse of the same headcode multiple times per day on a given route.

For example, in the 1980 SX WTT, the majority of local trains between Carlisle and Whitehaven are coded 2P59 in BOTH directions!

Just curious - at what point did BR twig the compromise in safety this caused ("hello signaller, this is 2P59 at Wigton... no the down direction...") and mandate that the same headcode not normally be reused within a 12 hour period on a given box or panel area?

Were there any accidents caused by this issue in that period?

This was long before ROCs covering large areas. In your example, I expect the signaller at Wigton would have had the train in plain view from the 'box. I think it was fairly common for all local trains on branch lines to have the same headcode. (Staines West branch was 2A82). I doubt that quoting headcodes to precisely identify an individual train trip were a thing then.

 

[Wilts Wanderer]

The principle certainly pre-dates ROCs - but clearly post-dates the introduction of TRUST. I also wondered whether there was some incident that triggered a policy change, so if anyone knows of it, I'll be interested to hear.

 

[30907]

Can't say when the change occurred, but
- class 2 services were commonly given a route code as you describe from the beginnings of 4-character headcodes.
- when individual 4-character codes were eventually introduced on SR WTTs, they inevitably repeated within the day (as well as within each division). Don't have an early 70s WTT handy to check....

 

[6Gman]

I think the practice, certainly in the 60s/70s, was that the two numbers following the letter were a route indicator rather than a unique reference number. So a 2F56 approaching Liverpool would be coming from Wigan and a 2F62 would be coming from Manchester Vic. (These are hypothetical examples, not saying those were the actual numbers used)

When TOPS was introduced 7 digit headcodes were used (but not displayed) with the first two digits of the originating TOPS location code as a prefix and a letter suffix.

So Crewe-Manchester stoppers might be 422H52a, 422H52b, 422H52c etc.

 

[Gloster]

In a lot of cases you don’t really need different headcodes. If one train follows another with no change of routing, then it doesn’t matter if it is 2P59 or 2P59. It is only if you have different routing, destinations (sometimes) or calling patterns (again sometimes) that there needs to be a clear differentiation between trains for the signalmen. With an awful lot of trains and less than 2000 numbers available, compromises have to be made.

 

[Taunton]

Trains at that time, probably right through the display of 4-character codes (it wasn't that long, about 1960 to 1975) were not particularly referred to by the code. In the example, even if under the control of Carlisle rather than a local box, it would be "I'm at the Wigton Up Home", and if there was any doubt about which train it would be "I'm the 11.08 off Carlisle". Having the same code as described allowed trains to run back and forth without messing about with reaching up to change the indicators at each end. Notably it was only after the physical display on train fronts stopped that things changed. And for the earlier half of the DMU fleet, they had only been capable of showing a 2-character code on the front anyway. So 2P59 Carlisle to Whitehaven just showed something like B2.

And it was a lot more useful that two oil lamps on the front of every steam-hauled local train, to all destinations ...

 

[etr221]

I found at www.barrowmoremrg.co.uk/BRBDocuments/BRB_4_Position_Train_indicators2.pdf an LMR publication explaining the Four Position Train Identification system on its introduction in 1961. Class B (or 2) and local ECS workings had route numbers for 3rd and 4th positions; freight trips had trip numbers; most other workings had individual identities; except certain types of working had 'specially allocated numbers'.
The impression I have is that - at least originally - the system was designed for signalmen, as a replacement for/improvement on the block bell codes they were used to, as much anything; and the concept of a system where each train would have an individual number to uniquely identify it across thesystem was not really considered.

 

[Taunton]

Ian Allan did one of their many interesting little booklets in the 1960s "BR Headcodes", which listed every one (doubtless taken from some official document cross-reference, like all such Ian Allan books), listed all the main line trains, showed all the 2-character and 4-character dmu headcodes, headlight codes, explained the various systems, etc.

I believe that besides spotters, such books were invariably found in control offices, shedmasters rooms, etc, being so much handier to use than the big old-fashioned BR duplicated documents with the same information.

 

[Springs Branch]

During the era mentioned by the OP, there were two almost-touching 2F50s at Wigan.

• 2F50 Manchester Victoria to Southport via Bolton.
• 2F50 Lime St / Wigan NW via St Helens Shaw St (both directions).

These trains would have run directly alongside each other at Wigan Station Junction, since the Lime Street stoppers all used the up side bay platforms at Wigan NW.

Signallers at Wigan No.1 box and subsequently Warrington PSB seemed to have managed without confusing them (admittedly very few trains crossed between the L&Y and LNWR lines at Wigan at that time, and none whilst in passenger service).

 

[Route115?]

There are still duplicate headcodes in use even on the same route which can be a nuisance if you want to unambigously refer to a train in delay attribution, etc. I think that there is also a Train Service Database Unqiue ID (TSDUID) but is over ten years ago that I dealt with timetables so my memory may be playing tricks. Someone who is current in the industry will know more.

 

[jfollows]

I think the practice, certainly in the 60s/70s, was that the two numbers following the letter were a route indicator rather than a unique reference number. So a 2F56 approaching Liverpool would be coming from Wigan and a 2F62 would be coming from Manchester Vic. (These are hypothetical examples, not saying those were the actual numbers used)

The attached from the 1977-78 CM working timetable shows the "route indication numbers for class 2 and empty coaching stock trains" on the south side of Manchester.
So Altrincham-Alderley Edge via Stockport was 2H54 and via Styal was 2H53 in both directions. Altrincham-Crewe via Styal was 2K61, and 2H61 in the opposite direction. 2K62 and 2H62 via Stockport. And so on.

== Doublepost prevention - post automatically merged: 8 Oct 2021 ==

Here also are the north Manchester equivalents - Wigan to Liverpool via St. Helens is 2F50 and Manchester Victoria-Liverpool via Patricroft is 2F52, for example. Opposite directions are 2F50 and 2J52 respectively. In this case from the same year's CP working timetable. As already noted, 2F50 was also Manchester-Southport via Bolton; 2F51 for Manchester-Southport via Atherton.

 

[Wilts Wanderer]

Thank you everyone for your very informative responses. That local headcodes were basically 'route codes' rather than unique IDs had never occurred to me. Quite a different world we operate in now.

 

[Rescars]

Trains at that time, probably right through the display of 4-character codes (it wasn't that long, about 1960 to 1975) were not particularly referred to by the code. In the example, even if under the control of Carlisle rather than a local box, it would be "I'm at the Wigton Up Home", and if there was any doubt about which train it would be "I'm the 11.08 off Carlisle". Having the same code as described allowed trains to run back and forth without messing about with reaching up to change the indicators at each end. Notably it was only after the physical display on train fronts stopped that things changed. And for the earlier half of the DMU fleet, they had only been capable of showing a 2-character code on the front anyway. So 2P59 Carlisle to Whitehaven just showed something like B2.

And it was a lot more useful that two oil lamps on the front of every steam-hauled local train, to all destinations ...

Taunton makes a good point about oil lamps. Of course the pre-1923 southern companies made an art form of headcode route indication with discs, coloured lamps et al. More here: https://sremg.org.uk/headcodes/headcodes.html

 

[gg1]

Taunton makes a good point about oil lamps. Of course the pre-1923 southern companies made an art form of headcode route indication with discs, coloured lamps et al. More here: https://sremg.org.uk/headcodes/headcodes.html

Very interesting link. I'd heard of simultaneously displaying both red and white lamps on the same end of a loco in certain circumstances but the use of green, blue and purple lamps are new to me.

 

[Rescars]

Very interesting link. I'd heard of simultaneously displaying both red and white lamps on the same end of a loco in certain circumstances but the use of green, blue and purple lamps are new to me.

Yes indeed - it must have made quite a sight.

 

[Whisky Papa]

There are still duplicate headcodes in use even on the same route which can be a nuisance if you want to unambigously refer to a train in delay attribution, etc. I think that there is also a Train Service Database Unqiue ID (TSDUID) but is over ten years ago that I dealt with timetables so my memory may be playing tricks. Someone who is current in the industry will know more.

I was involved in train planning at about the same time, and my recollection is that the four alpha-numeric characters were followed by a pair of letters in the train planning system which made apparently duplicated trains unique. At the time the Hadfield line was covered by only a small number of headcodes (probably nine in each direction) that appeared to repeat every few hours, but that no longer appears to be the case. I suspect there was a Network Rail mandated system for the allocation of the two extra letters for the Long Term Plan, but additional or amended STP trains often bore the initials of the train planner who had made the changes.