Jump to content

Recommended Posts

Hi All,

 

Quick question! I, modelling era 3-4 and have just made a tunnel entrance.  The question is, would there be signals controlling entry to the tunnel? My thoughts would be that this would be an obvious use for them, to ensure that one train has exited the tunnel before the next enters it. However on looking at pictures very few seem to have any sort of signals controlling entry. Thoughts?

 

Clive

Mainline tunnel portal.jpg

Link to post
Share on other sites

Tunnels do not of themselves necessitate signals in the way that say a set of level crossing gates usually required protecting signals.  

Block working would ensure that one train has arrived before another enters the section, whether or not there is a tunnel in the section.

So it was quite common with long tunnels to have a box near each end.  Rather that and sighting considerations tend to mean that you typically have them just before entry. 

 

Ideally you didn't have normal semaphore signals in tunnels because of limited space, smoke can obscure them and it's not an ideal place to be changing oil lamps.  Whilst not unknown, you don't usually have a stop signal immediately on exit either, because a tunnel is not the best place to stop a train, especially if an emergency arises and evacuation is needed.   Having said that, I believe the LNWR once has signals and a signalbox at the bottom of one of the big ventilation shafts in Kilsby Tunnel, the sulphurous atmosphere being so atrocious they had problems getting anybody to man the box.

  • Like 1
Link to post
Share on other sites
4 hours ago, Michael Hodgson said:

Tunnels do not of themselves necessitate signals in the way that say a set of level crossing gates usually required protecting signals.  

Block working would ensure that one train has arrived before another enters the section, whether or not there is a tunnel in the section.

So it was quite common with long tunnels to have a box near each end.  Rather that and sighting considerations tend to mean that you typically have them just before entry. 

 

Ideally you didn't have normal semaphore signals in tunnels because of limited space, smoke can obscure them and it's not an ideal place to be changing oil lamps.  Whilst not unknown, you don't usually have a stop signal immediately on exit either, because a tunnel is not the best place to stop a train, especially if an emergency arises and evacuation is needed.   Having said that, I believe the LNWR once has signals and a signalbox at the bottom of one of the big ventilation shafts in Kilsby Tunnel, the sulphurous atmosphere being so atrocious they had problems getting anybody to man the box.

 

The original Woodhead tunnel had a box in the middle but, surprisingly, it didn't last long!

The tunnels around Nottingham Victoria had signals just outside them due to the fact it was built in a massive hole in the ground.

 

  • Like 3
Link to post
Share on other sites
8 hours ago, Michael Hodgson said:

....... Ideally you didn't have normal semaphore signals in tunnels because of limited space, .......

.... not to mention the lack of daylight to illuminate the arm. There were some instance of special tunnel semaphores consisting of little more than the spectacle plate - but even they were electrically lit as soon as the technology allowed - and colour lights superseded them in due course.

The need to ensure one train had left a tunnel before the next entered disappeared with the introduction of what we think of as 'conventional' block working where only one train was allowed in a section ( whether or not a tunnel was involved ). In the early days of railways when time interval working was in force, entry to a tunnel was sometimes regulated thus - with disastrous results when things went wrong : e.g. Clayton Tunnel, 1861.

  • Agree 1
Link to post
Share on other sites

Quite a lot of tunnels have colourlights in them . They are ground mounted and a quite a bit smaller than than normal heads 

  • Agree 2
Link to post
Share on other sites
34 minutes ago, russ p said:

Quite a lot of tunnels have colourlights in them . They are ground mounted and a quite a bit smaller than than normal heads 

 

Indeed, London Transport has been using them since the earliest days of course 

  • Agree 2
Link to post
Share on other sites
10 hours ago, Michael Hodgson said:

...

  Whilst not unknown, you don't usually have a stop signal immediately on exit either, because a tunnel is not the best place to stop a train, especially if an emergency arises and evacuation is needed. 

...

The other problem with signals just past the exit is that it takes a few seconds for the driver's eyes to adjust to the increased light levels when exiting the tunnel.

Link to post
Share on other sites
40 minutes ago, Michael Hodgson said:

 

Indeed, London Transport has been using them since the earliest days of course 

Depends on your definition ........... there weren't a  lot of electric lights ( of any sort ) in the 1860's when the Metropolitan was started ........... London TransporT itself didn't come into existence 'til 1935 by which time all tube and sub-surface lines would have been electrically signalled - though a few semaphores survived on surface sections 'til the 50s.

Link to post
Share on other sites
  • RMweb Gold
5 hours ago, great central said:

 

The original Woodhead tunnel had a box in the middle but, surprisingly, it didn't last long!

The tunnels around Nottingham Victoria had signals just outside them due to the fact it was built in a massive hole in the ground.

 

 

The Mersey Railway had a signal box called River Bed - in the middle of the tunnel from Hamilton Square to James Street and directly under the river Mersey ! - I can't imagine that was a very pleasant place to work, and it only had 4 levers. It closed over 120 years ago.

 

 

Signals at entrances / exits (or even in)  to tunnels are not that rare, there were plenty of examples around but, as has been mentioned they were there because of traffic needs, not because of the tunnel itself.

  • Agree 1
Link to post
Share on other sites

Cannonbury tunnel has a normal three aspect post mounted signal in the middle of it wheree the second track used to be. Not so bad getting stopped at it with an electric but you don't want to be stood there very long with a diesel 

  • Like 2
Link to post
Share on other sites

Tunnels on my route card with signals inside them Kilsby, Hunsbury Hill, Watford (Fast and Slow tunnels). Regards to Watford, the id plates for the signals are mounted on the tunnel walls so you can't read them until you're right on top of them ;)

  • Like 2
  • Agree 1
Link to post
Share on other sites

There’s 4aspect signals halfway through Bradway tunnel (1mile 266yds) but they’re marked as distants on the plates even though it’s TCB round there. 
 

Also 4 aspects halfway through Belsize tunnel (1867yds) (round a dog-leg bend on the slows.)

 

They can display a red though, very common to be held there when you’re queuing with an ECS for Cricklewood behind a Thameslink. 

  • Like 1
  • Agree 1
Link to post
Share on other sites

The tunnels out of Glasgow Queen St. have (now bi-di) colour light signals in them, I think they are 'floor-mounted'.

The Glasgow Central & Queen St. low-level (tunnel) lines have always had signals and there were some signal boxes too until late-'60s (although Central Low-level line closed in '65, eventually returning as the Argyle Line in 1979)

  • Like 1
Link to post
Share on other sites

Like a lot of these sort of questions, the quick answer is 'it depends'.  Assuming that we are talking about absolute block working with semaphore signals, there is nothing about a tunnel that differentiates it from any other part of the block section that it is in for signalling purposes, but if the sighting of a signal is affected by it, then the distant or outermost home signal is moved back to the tunnel entrance, so that the driver knows what to expect when he comes out the other end.  For modelling purposes, if the tunnel is immediately ahead of signal box, that box's home signal will be at the tunnel entrance, not in the tunnel or at it's exit, although there were semaphore signals directly outside the exits from the Newport tunnels approaching High Street.

 

I am no expert on London Underground's signalling, but AFAIK the system was always colour lights operated automatically by the trains in much the same way as surface  railways' MAS signalling.

Link to post
Share on other sites

There's UndergrounD an' there's UndergrounD - yes the tube lines have always been fully electric but the Met and the District sub-surface lines started out steam worked - broad gauge in the former case - long before electrickery became commonplace ........ or reliable enough for signalling.

  • Agree 1
Link to post
Share on other sites
On 04/03/2021 at 10:11, Michael Hodgson said:

Indeed, London Transport has been using them since the earliest days of course 

 

Sort of depends upon what you mean. LT only came into being in 1933, so, yes, true.

 

The subsurface railways (Met, District etc) from 1863 used mostly conventional semaphore signals initially, although I think maybe some "armless" ones.

 

I believe that the first Tube, the C&SLR initially used "mechanical colour lights" - I can't recall the details off-hand, but I've got a drawing somewhere, and I think they operated with colour-slides behind the lens, red over green, so that they fell back to red if the wire broke. [EDIT: a further delve suggests that the very first version used rotating lenses, a bit like a Bardic Lamp, and that the vertical ones came slightly later]

 

By c1900 an electro-mechanical automatic  system devised by the great Mr Spagnoletti was in use on the Central London Railway and I think the GNP&B (Piccadilly Line). This had lights only in tunnels, and lights plus arms above ground. This used a brush-contact on the rear car of each train, in contact with ramps at the side of the track to complete the circuit that released the signals. I've got basic schematics for this.

 

I'm sure more details are in "Rails Through The Clay", but my copy is (appropriately) buried somewhere (in a cupboard, not below the soil).

 

EDIT: Blow me, if you follow a link in the previous post, you get a better description of Spagnoletti's system!

 

 

Edited by Nearholmer
  • Like 2
Link to post
Share on other sites
3 hours ago, Wickham Green too said:

Met and the District sub-surface lines started out steam worked - broad gauge in the former case - long before electrickery became commonplace ........ or reliable enough for signalling.

 

Again, sort of.

 

Electric block telegraph was used from the very start in 1863. Mr Spagnoletti, mentioned above, designed that too, and some of his instruments were in use until c1960.

 

Spagnoletti is a bit of a forgotten genius - read a bit about him here  https://en.wikipedia.org/wiki/Charles_Spagnoletti  I believe his voice was recorded for posterity, either on a wax cylinder, or a predecessor metal disc recording format, I think singing the national anthem - the recording is in the possession of the IET and I've heard a copy of it at a lecture.

  • Agree 1
  • Informative/Useful 2
Link to post
Share on other sites
3 hours ago, rodent279 said:

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

It still does as far as I know.

 

Plenty of other tunnels with stop signals within their length.  Clayton and Sevenoaks on the SR are among them.  Unusual to get stopped but not unusual to get slowed by yellows in the depths.  

 

The presence of a tunnel did not of itself require stop signals to prevent a train entering before the one ahead had cleared.  In a lot of cases line-of-sight would prove the absence of a train ahead.  Even the basic time-interval working system does not prove absence of a train in the tunnel; it may have stalled.  Flags rely upon time interval or human observation for safety.  Fixed signal sections are arranged - when possible - to avoid having signals within or immediately upon exit from tunnels but where they are present near the entry they are not there specifically to control entry to the tunnel.  They exist to control entry to the track section ahead.  In a few cases that section is almost or entirely within a tunnel but not commonly.  

 

 

  • Like 1
  • Agree 1
Link to post
Share on other sites
On 04/03/2021 at 10:48, WillCav said:

The other problem with signals just past the exit is that it takes a few seconds for the driver's eyes to adjust to the increased light levels when exiting the tunnel.

I would disagree with that statement

Unlike the people in the coach who are in the tunnel and only see the outside as you come out the driver can see the exit approaching and can see a signal that might be just outside the exit

 

In this picture a Colour Light can be see protecting the entrance on the Up and the back of the signal on the Down.

Woodhead Tunnel DMU 01/02/1981

 

As someone else said you don't find signals protecting tunnels but as the block section was 3+ miles long they kept it as short as possible

 

The same applied before Totley Tunnel at Grindleford on a route I used to drive over

 

Peter

Edited by Peter749
  • Like 3
Link to post
Share on other sites
  • RMweb Gold
On 04/03/2021 at 00:14, Michael Hodgson said:

Ideally you didn't have normal semaphore signals in tunnels because of limited space, smoke can obscure them and it's not an ideal place to be changing oil lamps

Whem my grandfather joined the LNWR Signal and Electrical department after WW1 he worked on semaphore signal in the tunnels at New Street.  They didn't have arms,  just coloured spectacles movinng in front of a lamp. These were actually gas lit at that time as were other signals on the station which were fed from the station lighting supply. On pictures from Victorian times the pipes can be seen going up signal posts and into the bottoms of the lamp cases. 

  • Like 3
  • Informative/Useful 1
Link to post
Share on other sites
22 hours ago, keefer said:

The tunnels out of Glasgow Queen St. have (now bi-di) colour light signals in them, I think they are 'floor-mounted'.

The Glasgow Central & Queen St. low-level (tunnel) lines have always had signals and there were some signal boxes too until late-'60s (although Central Low-level line closed in '65, eventually returning as the Argyle Line in 1979)

 

IIRC the signal on the Down (Helensburgh-bound) line in the tunnel beyond High Street station was/is particularly awkward to see, so much so that Scotrail issued an instruction that Drivers were not to pass the preceding signal at High Street unless it was displaying a green aspect. Not a major issue, until one day that signal could only be cleared to yellow. Cue huge delays, and much discussion over how to resolve the situation (and later, who would accept the delay minutes !).

 

  • Informative/Useful 1
Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.