Signalling - Route Setting

[Y Ddraig Coch]

I have noticed whilst driving to work the last few days that when setting the signals, level crossing etc, the signaller works backwards.

They set the furthest set of lights then the next set back then the level crossing and the next set going back one by one until they are closest to the train.

It got me thinking, Is this how it is always done? I am not sure how I thought it was done, it does make sense now I have thought about it, I just assumed it would be the other way round without ever thinking too much about it.

This is on a small branch line, does this make a difference? Are main lines carried out differently? Or is this the standard procedure for all lines?

Thanks in advance.

 

[Johncleesefan]

I have noticed whilst driving to work the last few days that when setting the signals, level crossing etc, the signaller works backwards.

They set the furthest set of lights then the next set back then the level crossing and the next set going back one by one until they are closest to the train.

It got me thinking, Is this how it is always done? I am not sure how I thought it was done, it does make sense now I have thought about it, I just assumed it would be the other way round without ever thinking too much about it.

This is on a small branch line, does this make a difference? Are main lines carried out differently? Or is this the standard procedure for all lines?

Thanks in advance.

Always the case, ie the signal closest to the train can only go from yellow to green once the signal after it has gone from red to yellow etc

 

[Sunset route]

I have noticed whilst driving to work the last few days that when setting the signals, level crossing etc, the signaller works backwards.

They set the furthest set of lights then the next set back then the level crossing and the next set going back one by one until they are closest to the train.

It got me thinking, Is this how it is always done? I am not sure how I thought it was done, it does make sense now I have thought about it, I just assumed it would be the other way round without ever thinking too much about it.

This is on a small branch line, does this make a difference? Are main lines carried out differently? Or is this the standard procedure for all lines?

Thanks in advance.

Depends if it's signalled under Absolute Block Rules (AB) or Track Circuit Block Rules (TCB).

AB Is what must people will associate with the old traditional semephone signal (there can be modern colour light replacements).

TCB Is uaslly mass 2, 3 or 4 aspect colour colour light signalling.

In AB signalling all associated stop signals (the ones that can show a red) must be pulled (cleared) in sequence the home signal the first stop signal in the direction of travel associated with the signalbox) through any other stop signals that maybe provided up to and including the section signal (the last stop signal associated with a signalbox in the direction of travel, which lets the train into the next block section). When all stop signals have been cleared in that order then the distant signal can be cleared, the distant signal is the first signal a driver will see that is associated with the signalbox that they are approaching.

In TCB it's basically route setting from signal in rear to signal in advance (one signal section no Block sections involved here) and repeat as required. The aspects change up based on the signal ahead.

Based on local arrangements and working practices (individual or mandated) there are various methods around the country that adhere or vary in difference to above.

 

[Ianno87]

In TCB land, sometimes signallers get the 'further along' routes in place first, before setting the one closest to the train.

This means that if they make an error in setting the 'further along' routes, they can put them back to red without an approaching train seeing an adverse change of aspect immediately in front of it (if you see what I mean) by setting the route/signal closest to the train last.

 

[Y Ddraig Coch]

In TCB land, sometimes signallers get the 'further along' routes in place first, before setting the one closest to the train.

This means that if they make an error in setting the 'further along' routes, they can put them back to red without an approaching train seeing an adverse change of aspect immediately in front of it (if you see what I mean) by setting the route/signal closest to the train last.

This is exactly what I see daily.

Normally a set of lights on red furthest away clears to yellow, then they activate the crossing barriers, then the next set of lights closer to the train etc etc. Once that s all done they clear the first (furthest set away) to green.

So this all makes sense now.

Thanks for all your replies. Very informative.

 

[rebmcr]

In TCB land, sometimes signallers get the 'further along' routes in place first, before setting the one closest to the train.

This means that if they make an error in setting the 'further along' routes, they can put them back to red without an approaching train seeing an adverse change of aspect immediately in front of it (if you see what I mean) by setting the route/signal closest to the train last.

Which would also incur an associated cooldown timer before the route can be correctly re-set!

 

[LAX54]

At Colchester ASC we set 'the normal way' that is, in sequence, so signals clear as they would in an AB box
sometimes the siggy will set an advance signal first, and then work up to it, but its mainly down to personal pref

Think if we worked backwards, we'd 'check' too many trains !

 

[edwin_m]

If the OP could identify the location someone might come up with a specific reason. Could be as simple as the order the signaller gets to the buttons while walking along the panel after lowering the crossing?

 

[Y Ddraig Coch]

If the OP could identify the location someone might come up with a specific reason. Could be as simple as the order the signaller gets to the buttons while walking along the panel after lowering the crossing?

It's the Llandudno branch.

They start with the last set of lights before they cross the main line into Llandudno Junction (furthest from approaching train), then the Deganwy Quay Level crossing, then the Deganwy Station starter, then then the Deganwy Beach level crossing. (closest to approaching train)

 

[33056]

Can't comment on the Llandudno branch but I have known places where the route has to be set "backwards" to get an overlap to set in the desired direction or to ensure that a route is clear throughout and a train won't get stopped in an awkward place (can think of at least two places I have worked where it was only possible to set the route backwards otherwise it could not be set). Routes should also be set backwards for a propelling move but I presume that would not apply at the location in question!

 

[Tomnick]

I think there's two separate factors at play here.

The last signal, or the first to be cleared, is controlled by Llandudno Junction whereas the other two are controlled by Deganwy. LJ will, given the short section, probably put the route in as soon as the train is described to him if other traffic allows.

For Deganwy's two signals, it's possibly as simple as personal preference if both crossings can't be lowered simultaneously. In the other direction (into an absolute block section) sequential locking would almost certainly enforce signals being cleared in the 'correct' direction, so maybe it's just a routine that the signalmen have got into.

 

[Y Ddraig Coch]

I think there's two separate factors at play here.

The last signal, or the first to be cleared, is controlled by Llandudno Junction whereas the other two are controlled by Deganwy. LJ will, given the short section, probably put the route in as soon as the train is described to him if other traffic allows.

For Deganwy's two signals, it's possibly as simple as personal preference if both crossings can't be lowered simultaneously. In the other direction (into an absolute block section) sequential locking would almost certainly enforce signals being cleared in the 'correct' direction, so maybe it's just a routine that the signalmen have got into.

Thanks Tomnick, that probably explains it. Llandudno Junctions clears the furthest set to yellow, lets Deganwy know, then they do their crossings and signals, then he lets Junction know he is all set then junction clears the furthest set to green, which is normally how I see it.

But from a lot of the replies, it seems it's preference rather than set rules in a lot of locations, quite rare for the railway. Most things are very black and white.

 

[Tomnick]

Llandudno Junction doesn't need to tell Deganwy when the former's first signal is cleared. That can happen in any order - all that Deganwy would normally need is the track circuit between the two (plus overlap) clear and LJ's signal proved alight (doesn't matter what aspect it's showing). Deganwy's starter can then clear to yellow, and it'll then step up to green automatically if/when LJ clears his first signal (or straight to green if it's already cleared).

Similarly, LJ's first signal will automatically step up to green if/when the second signal is cleared.

 

[edwin_m]

Similarly, LJ's first signal will automatically step up to green if/when the second signal is cleared.

Just to clarify, this means that there is full braking distance between the two (stop) signals in question. A traditional semaphore box as discussed in a previous post would probably not have full braking distance between its stop signals, so all of them would have to be cleared before the distant could show a green.

 

[Tomnick]

Just to clarify, this means that there is full braking distance between the two (stop) signals in question. A traditional semaphore box as discussed in a previous post would probably not have full braking distance between its stop signals, so all of them would have to be cleared before the distant could show a green.

Yup, that too. Even where the starter at one box also acts as the distant for the box in advance, though, the box in rear doesn't have to do anything to get it to step up from yellow to green - it's done by the box in advance, whether that's automatically or with a yellow lever! In that case, though, it's much more likely that sequential locking would be provided which would prevent the sequence observed by the OP occurring in the first place.