Shortest headways

[newWCMLwatcher]

I've seen a couple of videos of situations where trains are running very close to one another, what might even be block-on-block running.

An example of such scenario is here:

- Britannia and Galatea running within spitting distance of each other on the WCML. Shortly followed by a 66 convoy.

Now I know this must happen quite often and we never actually see it out in the sticks, but I wondered if there's any footage or if anyone has witnessed any particularly short headways?

Another example here:

The Pendolino passes at 00:56 and the points change at 1:08, a mere 12 seconds after it has passed.

 

[The Planner]

The kettles were nowhere near block on block, they were over 5 minutes apart. That Pendolino would have been a long way in front by the time the second train left the loop. You can plan the second train to do that and leave at less than the headway value for that very reason.

 

[Tomnick]

The points could be swung as soon as the Pendolino's passed clear of them, even sooner than they actually were, either on individual switches or by oversetting the route. That's not necessarily when the signal cleared. Even so, though, it only needs to get one signal section clear before the one out of the loop gets a single yellow - you couldn't keep two trains moving at speed on that headway though!

 

[newWCMLwatcher]

The points could be swung as soon as the Pendolino's passed clear of them, even sooner than they actually were, either on individual switches or by oversetting the route. That's not necessarily when the signal cleared. Even so, though, it only needs to get one signal section clear before the one out of the loop gets a single yellow - you couldn't keep two trains moving at speed on that headway though!

Thanks for replying, I've learnt a lot from your posts. So, as soon as the Pendolino cleared the points are you saying that this would be shown to the signaller? The thing with this, is that I've always thought that a train must pass a signal to give the signaller an indication of its position. I know track circuits are used, I guess these may be in place with more accurate positioning reports rather than relying on signal sections? I find it so interesting that a route can be set so quickly from the passing of a train, with the signaller knowing the rear bogies have cleared the junction. Making those changes a matter of seconds afterwards is just so surprising to me.

 

[newWCMLwatcher]

The kettles were nowhere near block on block, they were over 5 minutes apart. That Pendolino would have been a long way in front by the time the second train left the loop. You can plan the second train to do that and leave at less than the headway value for that very reason.

Maybe not but the 66s were stopped at the signal whilst Brtannia was still in the section in front. Very surprised this was practice on a section so far in the middle of nowhere.

 

[Tomnick]

Thanks for replying, I've learnt a lot from your posts. So, as soon as the Pendolino cleared the points are you saying that this would be shown to the signaller? The thing with this, is that I've always thought that a train must pass a signal to give the signaller an indication of its position. I know track circuits are used, I guess these may be in place with more accurate positioning reports rather than relying on signal sections? I find it so interesting that a route can be set so quickly from the passing of a train, with the signaller knowing the rear bogies have cleared the junction. Making those changes a matter of seconds afterwards is just so surprising to me.

There'll often be more than one track circuit in each signal section, especially where there's pointwork involved as there is here. It's useful for the signalman to know when the train's cleared the pointwork, not least for movements which might then almost immediately stop behind a shunt signal to go back over the pointwork in the other direction. There's a photo of the relevant part of Motherwell panel here where you can just about pick out the different track circuit sections (adjacent track circuits being shown in different colours).

I think it'd be well worth you having a look over at www.simsig.co.uk - there isn't a better power-signalling simulation anywhere, in my view.

 

[newWCMLwatcher]

There'll often be more than one track circuit in each signal section, especially where there's pointwork involved as there is here. It's useful for the signalman to know when the train's cleared the pointwork, not least for movements which might then almost immediately stop behind a shunt signal to go back over the pointwork in the other direction. There's a photo of the relevant part of Motherwell panel here where you can just about pick out the different track circuit sections (adjacent track circuits being shown in different colours).

I think it'd be well worth you having a look over at www.simsig.co.uk - there isn't a better power-signalling simulation anywhere, in my view.

Thanks, I'll make sure I check it out. Pointwork and circuits has interested me for a long time, I'm sure someone will take it on.