Tunnel Signals

[LNERGE]

Here's one.. The searchlight head was from Barking. The King's Cross fault team came and borrowed it from my garden where it was working quite happily. It's back in the garden now with a bit more history attached..

 

Edited March 5, 2021 by LNERGE

[SM42]

There are signals in the tunnel approaching New St from Wolverhampton. There used to be one until the NIA was built and now there are two.

The  signals on the other routes are outside the tunnels, some with low level co acting signals to add sighting.

 

Andy

[The Stationmaster]

The Severn Tunnel has long had.problems with signals.  IB signals were installed in the tunnel i during the war (1942 I think without checking) but were in trouble almost from teh start because track circuits would b not work reliable in the tunnel.  these signals were removed at the earliset oppportunity.  Signal were again installed in the tunnel during the 1970s Newport panel extension scheme and hit exactly teh same problem so they too were taken out after a fairly short life. due to the high incidence of track circuit failures.  Axle counters might be more reliable but I doubt there is much need nowadays for the additional capacity signals in the tunnel would offer.  

 

I know the Mersey rail tunnel suffers an excessively high rate of rail wear due to atmospheric conditions so I wonder if it too might have suffered track circuit reliability problems?

 

There is also a lineside signal in the CTRL tunnel approaching St Pancras - it's the commencement of lineside signals and the transition from TVM.  It caused a lot of headaches during SPAD risk assessment for the St Pancras signalling because it is approached on a rising gradient, it is at the end of the changeover from TVM, and originally 'somebody'. had planned in a neutral section about 100 yds in rear of where the signal would have to be sited.   The reaction of the latter 'planners' when they were called to the SPAD risk meeting was fascinating to say the least, especially when they started talking about APC magnets associated with the neutral section.   Needless to say the neutral section was moved a considerable distance.

[Ken.W]

On 05/03/2021 at 07:28, rodent279 said:

Has anyone mentioned Gasworks Tunnel? Didn't that have colour light signals in it?

 

Yes, it does, or at least it did until this month.

 

In the Down direction there's signals about a couple of engine lengths inside the tunnel - enough for a light engine to enter the tunnel clear of the GPL, then change direction back  into another platform.

Also ground mounted colour lights at the exit, and on the R/H side on 'A Line' (the R/H line).

In the Up direction the colour lights at the entrance apply right up to the stops.

 

However, the station's currently half closed for the final phase of the remodeling, which includes re-opening the east bore of Gasworks. I don't know where the new signals will be positioned.

[Mike_Walker]

On 06/03/2021 at 12:31, The Stationmaster said:

The Severn Tunnel has long had.problems with signals.  IB signals were installed in the tunnel i during the war (1942 I think without checking) but were in trouble almost from teh start because track circuits would b not work reliable in the tunnel.  these signals were removed at the earliset oppportunity.  Signal were again installed in the tunnel during the 1970s Newport panel extension scheme and hit exactly teh same problem so they too were taken out after a fairly short life. due to the high incidence of track circuit failures.  Axle counters might be more reliable but I doubt there is much need nowadays for the additional capacity signals in the tunnel would offer.  

 

I know the Mersey rail tunnel suffers an excessively high rate of rail wear due to atmospheric conditions so I wonder if it too might have suffered track circuit reliability problems?

 

There is also a lineside signal in the CTRL tunnel approaching St Pancras - it's the commencement of lineside signals and the transition from TVM.  It caused a lot of headaches during SPAD risk assessment for the St Pancras signalling because it is approached on a rising gradient, it is at the end of the changeover from TVM, and originally 'somebody'. had planned in a neutral section about 100 yds in rear of where the signal would have to be sited.   The reaction of the latter 'planners' when they were called to the SPAD risk meeting was fascinating to say the least, especially when they started talking about APC magnets associated with the neutral section.   Needless to say the neutral section was moved a considerable distance.

The current arrangements within the Severn Tunnel is that it has axle counters  throughout.  Both lines are signalled for bi-directional operation and there are "distant" signals on both lines at both ends referring to the signals found outside on leaving the tunnel, NT1014 and NT1616 at the London end and NT1029 and NT1625 at the Welsh end.  There are also emergency signals on both lines which are normally dark but can only display red when activated.  These are at 12m 15c in the down direction and 14m 10c in the up (the tunnel portals are at 11m 01c and 15m 29c).  There are also "change of gradient" lights which can be spotted from train windows if you are observant.  These are blue lights and comprise a single light roughly 1/4 mile from the point where the descending gradient flattens out and a double light at the actual point where the change occurs.  These are repeated on both lines in both directions.

[The Stationmaster]

1 hour ago, Mike_Walker said:

The current arrangements within the Severn Tunnel is that it has axle counters  throughout.  Both lines are signalled for bi-directional operation and there are "distant" signals on both lines at both ends referring to the signals found outside on leaving the tunnel, NT1014 and NT1616 at the London end and NT1029 and NT1625 at the Welsh end.  There are also emergency signals on both lines which are normally dark but can only display red when activated.  These are at 12m 15c in the down direction and 14m 10c in the up (the tunnel portals are at 11m 01c and 15m 29c).  There are also "change of gradient" lights which can be spotted from train windows if you are observant.  These are blue lights and comprise a single light roughly 1/4 mile from the point where the descending gradient flattens out and a double light at the actual point where the change occurs.  These are repeated on both lines in both directions.

Nothing really new then apart from changing the colour of the change of gradient lights from white to blue which dates back a lopng time.  Axle counters instead of track circuits have been there since 1987 although originally I think it only worked asa single section.  The emergency red signals are basically similar to replacing the intermediate signals to danger by the alarm wire replacement of signals to danger which was installed in the 1970s but those signals were removed  in the 1980s and and not retained as emergency signals.  It is, i think sensible to provide new emergency signals in view of the long section in darkness and might have mitigated or avoided the 1991 collision (which had to happen on the day I was the Regional Duty Officer but tthen had to be quickly pushed up the management tree) to GM level).

 

There were of course colour light distant signals in the tunnel long before MAS and that has never changed apart from their  position.