Semaphore signals and colour light signals.

[30907]

The classic semaphore case of a 'wrong side failure' being Abbots Ripton, in '76, where the signal failed (due to ice and snow) to an aspect indicating the block was clear. Sam

For younger readers it was 1876 not 1976. The slotted-post signal(s) froze in the clear position with disastrous results. As well as the rule-book change, this led to the GNR adopting the distinctive "somersault" signal.

 

[Old Hill Bank]

AndyPJG - I'm sure there are plenty of auto signals (with ERSs) that are plated as such?[/QUOTE]

Agreed, Stourbridge-Hartlebury re-sig commissioned last August has plenty of them.

 

[MarkyT]

Automatic signals with emergency replacement won't be plated as autos, so that a driver can't pass on his/her own authority as the signaller may be holding the signal at danger for a good reason.

The term 'automatic signal' has two distinct but related meanings, which can be a little confusing!

In signal engineering 'automatics' are signals used to divide up sections of unidirectional running line between junctions into distinct shorter blocks, so as to provide headway for traffic closely following in the same direction. Because there are no junctions in each block, no signalled conflicting movements possible in the other direction, and signaller workload concerns favour automatic re-clearance after the passage of each train, the logic in the control system to show yellow is remarkably simple, incorporating only track circuit clear to next signal overlap and proof the next signal is alight. To get better than yellow the aspect of the next signal also needs to be known, and an emergency replacement facility by the signaller can also be included, but this was by no means fitted to every example traditionally, often typically only one in five. Because of this simplicity, in old relay installations the entire control logic could be incorporated in the lineside cabinets and cables, with no centralised interlocking necessary and only very limited distributed remote control and indication facilities. Almost all such plain line signals were plated as 'automatic' traditionally, but a small number were not so classified because of particular location specific risks.

In operational terms an automatic plate has nothing to do with the control architecture, but is a clear indication to the driver that passing that signal at danger is allowed under certain circumstances without specific instructions from the signaller. The idea of the 'auto' plate was to allow traffic to keep moving if a signal is at danger and the driver couldn't get in touch with the signaller to obtain authority to pass it. On unidirectional lines there's little risk involved as the train passing the red must proceed able to stop at any obstruction, and traffic can't approach from the other direction except under special procedures where the signaller must ensure only one train is in the entire single line section at any time anyway.

Today, drivers usually talk to signallers over cab radio and if that fails the lineside signal telephones can provide back-up communications. There's little chance of no conversation taking place now, so the marginal risk of driver self-authorised movements, and their often slower speed can be avoided, hence auto plates are often not provided in new projects. Modern signal control technology allows every headway signal to be provided with an emergency replacement facility.

The train detection systems that control headway signals are also evolving, with the traditional track circuit giving way to axle counters in many areas. With direct connections to the exposed running rails and critical 'knife edge' adjustment of operating voltage and current, track circuits can be fairly prone to 'right side' failures related to weather or cargo spillage, and remain a significant reason why signals show red unintentionally.

Axle counters are much less prone to failures of this sort and should further reduce the need for trains to pass danger signals.

 

[pendolino]

In operational terms an automatic plate has nothing to do with the control architecture, but is a clear indication to the driver that passing that signal at danger is allowed under certain circumstances without specific instructions from the signaller.

The Rule Book was amended recently (see page 38 of Issue 16 of the Amendments Module) such that drivers can no longer pass automatic or semi-automatic signals under their own authority. The change was introduced because it rarely happened, largely because (as you say) CSR/GSM-R/mobile phone technology means that it is pretty much impossible to have no means of contacting the signaller.

 

[RPM]

The Rule Book was amended recently (see page 38 of Issue 16 of the Amendments Module) such that drivers can no longer pass automatic or semi-automatic signals under their own authority. The change was introduced because it rarely happened, largely because (as you say) CSR/GSM-R/mobile phone technology means that it is pretty much impossible to have no means of contacting the signaller.

I only know one driver who ever passed an automatic under his own authority, and they tried to pin it on him as a Cat A SPAD. The claim was that he had not exhausted every possible means of attempting to contact the signaller, despite the fact that the rule book failed to define exactly what lengths a driver should go to make contact. It was overturned eventually, but I suspect it was one of the incidents that led to the (very sensible) Rule Book amendment.

 

[MarkyT]

The Rule Book was amended recently (see page 38 of Issue 16 of the Amendments Module) such that drivers can no longer pass automatic or semi-automatic signals under their own authority. The change was introduced because it rarely happened, largely because (as you say) CSR/GSM-R/mobile phone technology means that it is pretty much impossible to have no means of contacting the signaller.

Thanks for that. Effectively the auto plate symbol is now redundant, as it conveys no relevant information to the driver. It might even be considered a risk if a driver forgets the rule has changed (I'm not saying that's particularly likely you understand). So perhaps the symbol should now be removed from all existing signals as well as new projects to avoid confusion, black gaffer tape might offer a cost effective short term solution!

 

[455driver]

Automatic signals with emergency replacement won't be plated as autos, so that a driver can't pass on his/her own authority as the signaller may be holding the signal at danger for a good reason.

You need to update your rules knowledge on passing signals at danger without authority!

edit-
I see others have beat me to it.

 

[pendolino]

black gaffer tape might offer a cost effective short term solution!

It's been used for just that purpose - at Cheam when the automatic signals were converted to controlled a month or so back. I shall keep an eye out when going that way to see if the plates get changed before the tape falls off.

 

[Trog]

There are signal post replacement switches at automatic signals that the S&T can use to put the signal to red with the use of a special key.

The P-Way also usually had a copy of this key for Hand Signalling duties.

I was once on a job where we managed to switch a signal to danger by smashing the cast iron key switch housing by backing a 12 ton 360' excavator into it.

The thing is that at the time no one including the machine driver noticed what had happened. The bash had however also pushed the signal slightly out of alignment and it was shining on the ground about 100 yards out. Needless to say the first driver past after the possession was given up, noticed this signal with a pool of red light on the ground in front of it straight away.

It cost the earth to get the S&T to get out of their nice warm vans to sort it out and they insisted that the whole signal was replaced to their latest standard.

 

[455driver]

The P-Way also usually had a copy of this key for Hand Signalling duties.

I was once on a job where we managed to switch a signal to danger by smashing the cast iron key switch housing by backing a 12 ton 360' excavator into it.
It cost the earth to get the S&T to get out of their nice warm vans to sort it out and they insisted that the whole signal was replaced to their latest standard.

Couldnt you just give it a wack from the other side?

 

[Trog]

Couldnt you just give it a wack from the other side?

If we had found it while we still had the plant on site we would probably have got a spirit level out and squared it up again. Before we got the S&T out to check it over.