What were British Rail "headcode boxes" used for?

In the tradition of old-school web-surfing, I was reading the latest Destination: Freedom Newletter, which led to looking up various British locomotive classes, which then led to stumbling across the term 'Headcode Box'

OK, searching around, I found the following about Headcode Boxes:
They were mandated on British Locomotives in the late 1950s
They seemed to replace a '4 disk system'
They had space for 4 large digits/letters, apparently manually changed as they often did not line up quite right
They were no-longer required after 1976.
Many locomotives which had them have since had them removed and the space plated over (often with new headlights installed).

These boxes seem to have had something to do with train ID, although I'm not clear on exactly how. Anyone have a good idea of how they were used, and why they were tossed (well before Privitization, and well before Thatcher even...) - and for that matter, how the diskes were used.


Here's a pic:
http://www.lexcie.zetnet.co.uk/tops/52-small.jpg

Headcode boxes displayed the 4-character train reposrting code so that signalmen and other staff could visually idenity the train service. (These reporting codes are still used to this day, just are not displayed on the locomotive/train itself - modern signalling/communication equipment and practices render this obsolete).

The first digit described the 'type' of train and also ranks it's 'importance'.
1= express passenger
2= seconary passenger
3= parcels/mail
4= freightiner (containerized, express freight service)
5= other freight
etc. etc.

The next character (always a letter) denotes destination (to a degree).
Each of the former British Railways regions had a set of letters which related to train destination points (or areas) within their region. E.g. inside the London Midland Region (LMR), trains headed for Crewe were given the letter 'K', Liverpool 'F', Manchester Piccadilly 'H' etc. You can see that the letter allocations were often purely arbitrary!

Inter-regional services would have the following letters, merely indicating in which region the service terminated (not the actual location):
M= train's destination is on the LMR
S= Scottish Region (ScR)
E= Eastern Region (ER)
W= Western Region (WR)
O= Southern Region (SR)

Later on, when the Anglia Region was formed from part of the ER this was given the letter L.

The final 2 digits simply identify the train. Generally trains from point A to point B would begin in the morning with low numbers and finish in the evening with higher numbers and would run in some kind of sequence. This practice was loose at best, though.

47432 wrote:Headcode boxes displayed the 4-character train reposrting code so that signalmen and other staff could visually idenity the train service. (These reporting codes are still used to this day, just are not displayed on the locomotive/train itself - modern signalling/communication equipment and practices render this obsolete).

Thanks, that does makes sense. And clearly radio communication was reliable enough by the mid-1970s to replace the visual sightings, although for some reason I still tend to mentally associate british locos with those big black number boards mounted on front, even though they haven't needed them for nearly 30 years...

Sir Ray wrote: They seemed to replace a '4 disk system'
.....Anyone have a good idea of how they were used, and why they were tossed (well before Privitization, and well before Thatcher even...) - and for that matter, how the diskes were used.

The disc system was, as you say, an earlier system prior to the use of headcode boxes. The discs (by day) or lamps (by night) were fitted on up to 4 brackets on the locomotive. The number and pattern of discs/lamps indicated the class of train or in a few local areas showed the destination.
http://www.bulleid.force9.co.uk/lneeg/nat-1947.html

Early diesel locomotives built before headcode boxes came along were fitted with hinged discs and lamps. The discs folded in half and would be opened up to display the required pattern.

After headcode boxes came along some of the remaining steam locomotives ran in some areas with paper digits/letters stuck on one of the discs to make up the headcode.

Sir Ray wrote:... And clearly radio communication was reliable enough by the mid-1970s to replace the visual sightings...

Radio communication for dispatching and train regulation has (in general) never been widely used in the UK. There are two or three rural lines that use radio signalling, and some yards use radio, but otherwise it is not used for train control.

The end of headcode boxes came about because centralised signal centres had become widespread and very little visual reporting of trains was neccessary.

geoffs wrote:

Sir Ray wrote:... And clearly radio communication was reliable enough by the mid-1970s to replace the visual sightings...

Radio communication for dispatching and train regulation has (in general) never been widely used in the UK. There are two or three rural lines that use radio signalling, and some yards use radio, but otherwise it is not used for train control.
The end of headcode boxes came about because centralised signal centres had become widespread and very little visual reporting of trains was neccessary.

Really? It's common over here in North America (just read some of Santucci's 'Hot Times On The High Iron' articles linked on the front page of this site. I would think that all British Railways (meaning British Rail and then post-privatized British rail companies) would have had radio dispatching since the 1970s, and perhaps cell-phone dispatching since the 1990s.
Probably the UK has a lot better signaling system then usual North American practice (which has a lot of 'dark trackage' controlled by...track forms! (and radio/cellphones))

Sir Ray wrote:Really? It's common over here in North America...
I would think that all British Railways (meaning British Rail and then post-privatized British rail companies) would have had radio dispatching since the 1970s, and perhaps cell-phone dispatching since the 1990s.
Probably the UK has a lot better signaling system then usual North American practice (which has a lot of 'dark trackage' controlled by...track forms! (and radio/cellphones))

The signalling and control systems in the UK (and many other countries) developed in a very different way to those in the US. Most of the basic development was done well before radio became an option.

There are exceptions but the general way in which signalling developed in the UK was that all passenger lines were fully signalled with signal cabins at most stations and junctions. There were/are various arrangements for single line sections including the token block system. Some minor branch lines worked on the "one-engine-in-steam" principle. Yard areas were controlled by a yardmaster.

On passenger lines if any verbal communication was needed for out of timetable operations or during disruptions train crews could contact the nearest signal cabin by telephones located on the signal posts.

By the time that radio dispatching became feasible, most of the UK system had signalling processes already in place that made it un-neccessary and this would have involved a major change in the whole signalling and control systems. There were also deep concerns about a system working on verbal communication only.

Some use of radio has been made in the UK in the last thirty years or so. Trains now do have radios but they are used as a secondary communication form for discussions such as problem reporting and during delays and disruption.
All passenger routes are signalled by one means or another - a passenger train cannot operate over handworked points (switches) without rather involed safety proceedures.
Some yards have radio to control yard movements but not passenger moves.
The only real use of radio dispatching on passenger lines is the UK is on some lines in the north of Scotland and the East Suffolk line. These lines have a radio system which has both voice and data traffic. Initial contact is made verbally between the train and the signal centre to request permission to proceed. The signal centre then sends a data signal to the train and a display in the train cab illuminates to show the names of the section for which permission has been granted. The driver then verbally confirms reciept as a extra check. At the end of the section, the driver presses at button to release the section back, again all data traffic being verbally double-checked.
More development work is currently going on with trials in Wales of a European standard system based on data over GSM-R cell systems.

Some local transist systems such as the London Underground do use radio as an overlay system. When all is working to plan the radio is not used, but control centres will use the radio to control train movements such as instructions to terminate short of destination during service disruption.