Bedford South Junction signalling question

[racyrich]

I have some questions re how the ladder of crossovers at Bedford South Junction works.

When a train is signalled across a ladder of crossovers, such as the move from Up Slow to Up Fast, when do the crossovers clear ready for another train movement? Does the train have to get all the way past the next signal or does each crossover clear using track circuits and can be released before the train clears the next signal.

I'm surprised that that 360 could be signalled across that ladder into a red signal. At the very least it would be traversing the junction slowly at whatever the prescribed speed is for approaching a red. And depending on the length of the train and the gap from the last crossover to the next signal, it could end up just sat there fouling 2 lines. And if the crossovers don't clear until the next signal is passed, those 2 lines remain blocked.

 

[bengley]

Why would the 360 not be able to cross the ladder up to the next signal if the route across the junction to the next signal was clear? There is nothing wrong with that move and similar moves happen all over the network hundreds of times a day.

 

[74A]

Does the move from the Up Slow to Up Fast use flashing signal aspects ?

 

[bengley]

Does the move from the Up Slow to Up Fast use flashing signal aspects ?

No.

 

[357]

Does the train have to get all the way past the next signal or does each crossover clear using track circuits and can be released before the train clears the next signal.

In basic installations the train would need to clear all of the points. In certain locations there are more track circuits meaning routes can be cleared faster.

Nothing wrong with this setup at all.

 

[Signal Head]

I have some questions re how the ladder of crossovers at Bedford South Junction works.

When a train is signalled across a ladder of crossovers, such as the move from Up Slow to Up Fast, when do the crossovers clear ready for another train movement? Does the train have to get all the way past the next signal or does each crossover clear using track circuits and can be released before the train clears the next signal.

I'm surprised that that 360 could be signalled across that ladder into a red signal. At the very least it would be traversing the junction slowly at whatever the prescribed speed is for approaching a red. And depending on the length of the train and the gap from the last crossover to the next signal, it could end up just sat there fouling 2 lines. And if the crossovers don't clear until the next signal is passed, those 2 lines remain blocked.

The route locking, which is what holds the points in the required position, is released for each individual track circuit, or (as is the case here because of the type of interlocking and the layout) set of points, so each set (keep in mind that the crossovers will probably be double-ended so work as a pair) will go free once the train has passed clear of them.

However this only happens after the route is cancelled, by signaller 'pulling the button' or automatically by passage of train in some places.

Standage for the required train lengths is taken into account when signal positions are planned out, so normally there is no restriction on running a train through a junction up to a red.

 

[357]

Standage for the required train lengths is taken into account when signal positions are planned out, so normally there is no restriction on running a train through a junction up to a red.

For clarity to anyone else reading this - I think it's also worth adding that if a train was longer than the section leading up to the signal and was still over the points - the track circuits over the points will remain occupied meaning another train can't come through

 

[Signal Head]

For clarity to anyone else reading this - I think it's also worth adding that if a train was longer than the section leading up to the signal and was still over the points - the track circuits over the points will remain occupied meaning another train can't come through

But this is on an individual basis, so if a train came to a stand still occupying a track circuit over the DS/UF crossover only, that would be locked Reverse (assuming the movement had come over from the US as it did here), but the US/DS crossover would be free to go Normal, so a train could then be signalled along the US, but not along the DS or, for that matter, the UF.

 

[357]

But this is on an individual basis, so if a train came to a stand still occupying a track circuit over the DS/UF crossover only, that would be locked Reverse (assuming the movement had come over from the US as it did here), but the US/DS crossover would be free to go Normal, so a train could then be signalled along the US, but not along the DS or, for that matter, the UF.

Yes - my concern was more that the way a layman or reporter could read your post was that the train could be longer than the designed section and have another train routed over the junction - your reply explains it much better than I did though

 

[S-Car-Go]

It is possible to be signalled through a junction where the exit signal is at red. The preceding aspect would be single yellow of course. If the junction is on a straight, it's easy to observe the red. On a curve where the red is not visible, there is a risk of passing the pointwork and then accelerating up to line speed. This location would be highlighted to drivers as part of their route knowledge. The risk increases when summer foliage blocks visibility on curvature (bare trees in winter means you can see further ahead).

 

[Annetts key]

It is possible to be signalled through a junction where the exit signal is at red. The preceding aspect would be single yellow of course. If the junction is on a straight, it's easy to observe the red. On a curve where the red is not visible, there is a risk of passing the pointwork and then accelerating up to line speed. This location would be highlighted to drivers as part of their route knowledge. The risk increases when summer foliage blocks visibility on curvature (bare trees in winter means you can see further ahead).

Yes. It’s possible and permissible to route across a junction to a red signal.

A driver should always assume and plan for any yellow aspect to mean that the next signal is red.

In terms of signal sighting (the distance that a signal should be visible from), there is a Network Rail standard for this. If there is a fixed or permanent structure such as a bridge, tunnel or the sides of a cutting on a curved line or anything else that means that the minimum sighting distance cannot be achieved, then a banner signal will be provided.

If the sighting distance has been compromised by vegetation, then if the vegetation is on railway land, normally it will be cut back. If the vegetation (e.g. a tree or trees) are on private land, then the railway will attempt to get permission from the landowner(s) to cut back the tree or trees.

However, there is a reliance on drivers reporting vegetation that is obscuring a signal, as a fault to the signaller. Otherwise this will not be picked up until the S&T maintenance staff do their own sighting check during routine maintenance. Which is not frequent enough to pick up a problem during the growing season (spring and summer).

There is also a problem in that the part of Network Rail that deals with vegetation (called Off Track) in some areas can’t cope due to the squeeze on the maintenance budget.