Can permissive working permit two moving trains in a block?

[jawr256]

I was recently on a train that was, through permissive working, allowed to enter platform 1 (a through platform) at Preston behind another train already in the platform. The other train was due to have already left, but its signal was not cleared until I had alighted from my train.

The late departure of the other train could of course be for all sorts of reasons, but it got me wondering - during permissive working at stations, do the rules allow for the signal to be cleared for the train in front and for it to be dispatched while the second train is still in motion?

And, considering fixed block signalling only, are there any other circumstances in which two trains are permitted to move within the same block?

 

[ComUtoR]

In a nutshell, yes.

 

[driver9000]

Yes it does and the rules tell a Driver to keep a safe distance from the train ahead in case it stops.

 

[LowLevel]

The one thing that you must not do, IIRC, is set a route from a call on signal where a permissive section signal is off. This is due to a crash at Stafford in the 80s where the driver of an empty EMU from Stoke to Soho crashed into the back of an overnight express station while it was delayed due to disorder. The driver, it is assumed (no data recorder then and he was killed) saw the green signal at the platform and assumed it was his. I believe it may also have seen off oil fired tail lamps.

 

[Tomnick]

I’m fairly sure that the rules don’t actually prohibit it, but the interlocking will do in many, but not all, installations. It’s called Huddersfield Control (possibly because that was where it was first provided?) but to the best of my knowledge came about as a result of the accident at Stafford that LowLevel refers to.

 

[185]

(iirc) Two white dots (aka cats eyes) accompanying the signal on approach to the platform proceed beyond the white dots at caution preparing to stop for any obstacles, trains, buffers or the next signal.

 

[Ken H]

The one thing that you must not do, IIRC, is set a route from a call on signal where a permissive section signal is off. This is due to a crash at Stafford in the 80s where the driver of an empty EMU from Stoke to Soho crashed into the back of an overnight express station while it was delayed due to disorder. The driver, it is assumed (no data recorder then and he was killed) saw the green signal at the platform and assumed it was his. I believe it may also have seen off oil fired tail lamps.

not seeing the next signal but the one after has always been a problem. Thats why we need a national plan for in cab signalling. As a bolt on goody for existing signal kit. How hard is it do transmit a short data message from trackside to train and display in the cab. 32 bits would do it. maybe 64 if you want to do speed restrictions too. from trackside to train and display in the cab. make the device something the driver takes from train to train and you dont need a device for every cab. Just one for each signed on driver.

 

[Highlandspring]

Brilliant. Patent this now. After all, “how hard is it”.

 

[edwin_m]

I imagine ERTMS has a function to manage permissive signalling and enforce a low speed on a following train if there is one in the block already. And of course ERTMS ultimately leads to removal of the lineside signals and therefore no possibility of reading through to aspects ahead. Considering that there have been no accidents from this cause for a couple of decades, I can't see any reason to spend a lot of money introducing a new system to track and train that would start to become obsolete almost immediately.

If there's an issue in a particular place, then an extra TPWS OSS could be provided. It would be activated when the berth track circuit was occupied, to give an emergency stop for any train approaching at anything faster than walking pace.

 

[Llanigraham]

I imagine ERTMS has a function to manage permissive signalling and enforce a low speed on a following train if there is one in the block already. And of course ERTMS ultimately leads to removal of the lineside signals and therefore no possibility of reading through to aspects ahead. Considering that there have been no accidents from this cause for a couple of decades, I can't see any reason to spend a lot of money introducing a new system to track and train that would start to become obsolete almost immediately.

If there's an issue in a particular place, then an extra TPWS OSS could be provided. It would be activated when the berth track circuit was occupied, to give an emergency stop for any train approaching at anything faster than walking pace.

It happens at Machynlleth every day, with no problems.

 

[Tomnick]

Brilliant. Patent this now. After all, “how hard is it”.

You can probably download an app for it already, it’s so easy.

not seeing the next signal but the one after has always been a problem. Thats why we need a national plan for in cab signalling. As a bolt on goody for existing signal kit. How hard is it do transmit a short data message from trackside to train and display in the cab. 32 bits would do it. maybe 64 if you want to do speed restrictions too. from trackside to train and display in the cab. make the device something the driver takes from train to train and you dont need a device for every cab. Just one for each signed on driver.

The risk here isn’t reading through beyond a signal, it’s reading through to the next signal with a train intervening. Either way, read through risks are already pretty well managed, identified where they do exist and highlighted during route risk briefs. Still a risk, but no great drama...

 

[Pigeon]

Brilliant. Patent this now. After all, "how hard is it".

As a true bolt-on extra, as proposed? It's a doddle. A TV remote control, with rechargeable batteries and a solar panel to charge them, gaffer taped to the signal post (oops, sorry, bolted to the signal post). LDRs wired across four of the buttons, and mounted on the underside of the hoods over the lenses with blu-tack (oops, sorry, with little bolted-on clamps), with collimator tubes pointing at the lights. Then the driver carries a portable TV in the cab (with the speaker removed, so it's not a distraction, and with gaffer tape over the screen apart from a little hole in one corner where the OSD channel number shows up). As the train goes past the signal, it changes the channel on the TV according to the signal aspect, and the driver can see the OSD channel number to be reminded what that aspect was.

For a real one, you'd want a more robust coding scheme than TV remote controls use, to avoid mis-reception; you'd arrange for the AWS pickup to clear the display, and mount the transmitter in the track shortly after the AWS magnet, to avoid it continuing to show the previous aspect if it misses receiving a code altogether; and you'd hard-wire it into the signal circuit rather than using LDRs. But these are mere details. It's still basically the guts of a TV remote control at the heart of it.

If AWS didn't exist, it would be even easier; you'd just invent it, in a modified form that transmits two bits instead of one.

 

[MarkyT]

There have been 'Huddersfield controls' as described by Tomnick above incorporated in new interlockings for two or three decades now, which prevent permissive routes being set into the rear end of a platform where the starting signal has already cleared and the converse where the route from the platform starter cannot be set until a permissive move to rear has been proved to have fully entered the platform and come to a stand. Permissive control logic can be very complicated indeed in some applications. I remember back in the 1980s, when I worked in Reading signalling drawing office, overlooking the railway, I often observed a frequent permissive move of empty stock from the DMU depot into platform 5 (the old up main platform) following a moving HST departure for Paddington. One day the DMU was following particularly closely when the HST made a sudden stop, possibly due to some kind of door incident. The DMU couldn't stop in time and there was an almighty crunch as the buffers cut two neat holes in the rear nose fairing. No injury or serious damage was sustained in that case thank goodness, but a series of similar but more serious incidents around this time led to a general prohibition of such simultaneous permissive movements and the development of Huddersfield controls for new installations. In some locations, such permissive working was important for throughput, at Cardiff Central for instance where frequent short trains follow closely through a very long platform.

 

[Bletchleyite]

It happens at Machynlleth every day, with no problems.

I was quite impressed when my connection (last train of the day onto the Pwllheli branch) involved walking about 10 yards - I had expected to need to cross the bridge (at some speed, because it's a now-official 4 minute connection!)

 

[Bletchleyite]

If AWS didn't exist, it would be even easier; you'd just invent it, in a modified form that transmits two bits instead of one.

If you invented AWS now, you'd invent Indusi or TPWS.

 

[pt_mad]

(iirc) Two white dots (aka cats eyes) accompanying the signal on approach to the platform proceed beyond the white dots at caution preparing to stop for any obstacles, trains, buffers or the next signal.

Are you describing position light/shunt signals?

And are these always available on approach at stations which allow platform permissive working?

 

[big all]

ok "permissive block"
"the line is only clear as far as the line is clear "
zero ambiguity there at least 25 years ago when i finished
go as far as required or requested within the scope off the engineers block or posetion
if in doubt question the picop the signal man or others in turn before taking an action that is counter inituative to your training or indeed self preservation you cannot be chastised for making reasonable extra checks withing an unusual situation within your employment
they can suggest you take extra tuition or training to cover the points
but providing you have the right level off skills are not overly careful or paranoid you will be fine

years ago on an engineers train at purley the blockman said to proceed on the the down slow towards the protection i said "are you sure " as the protection is the boundary
he said yes its fine
got to the protection just clear off the crossover at stotsnest to redhill he removed the dedts and said proceed now i again said are you sure because there was still in doubt as beyond the protection could be open track and someonelses space
got to the signal on the divergance to redhill and asked the secondman {remember them } to get permission to proceede
he said the signal man wanted to speak to me
we had just entered a open track but avoided danger
now whilst i was innocent as such and never found lacking i accept i should have fully understood and fully aqauinted my self off the then i think section "d"
any way the point i am making being sensible acting on a "gut feeling if not a bit overcausiouse will not get you penalized

 

[LAX54]

I was recently on a train that was, through permissive working, allowed to enter platform 1 (a through platform) at Preston behind another train already in the platform. The other train was due to have already left, but its signal was not cleared until I had alighted from my train.

The late departure of the other train could of course be for all sorts of reasons, but it got me wondering - during permissive working at stations, do the rules allow for the signal to be cleared for the train in front and for it to be dispatched while the second train is still in motion?

And, considering fixed block signalling only, are there any other circumstances in which two trains are permitted to move within the same block?

NO! you cannot clear the signal for a train to depart one end with another arriving at the other end.

 

[LAX54]

Yes it does and the rules tell a Driver to keep a safe distance from the train ahead in case it stops.

WHAT ?

 

[driver9000]

WHAT ?

Have a look at TW1 20.4 which gives a clear instruction on moving towards a moving train under permissive working.

 

[driver9000]

NO! you cannot clear the signal for a train to depart one end with another arriving at the other end.

They certainly can at Preston where the OP mentions.

 

[Pigeon]

If you invented AWS now, you'd invent Indusi or TPWS.

Yes. I think you've got my point

 

[MarkyT]

If you invented AWS now, you'd invent Indusi or TPWS.

Yes. I think you've got my point

I think you'd use standard ETCS components to create a digital limited supervision system that could potentially do all sorts of things. Siemens offered such a thing to Railtrack around 2000 when they were looking at options for TPWS+ systems, but since trains had already just been fitted with TPWS it would have required additional equipment on board and didn't stand a chance against just putting down additional loops based on the original tech. A HST power car was tested on the GWML with balises somewhere around Slough I recall.

 

[lineclear]

I am concerned about some of the replies on this thread, at least concerning permissive working on platform lines.

TS2 regulation 3.3.4 prohibits some scenarios described above.

 

[nom de guerre]

Hmm...

 

[big all]

sorry about my earlier post in case it caused confusion
i was off course ranting on about an engineers [absolute block ]or have i got that wrong as well ??

we just called it permissive working and being based both at coulsdon north and redhill over the years was a nearing an every day often several times a day occurrence so no no big deal

 

[nom de guerre]

I was recently on a train that was, through permissive working, allowed to enter platform 1 (a through platform) at Preston behind another train already in the platform. The other train was due to have already left, but its signal was not cleared until I had alighted from my train.

The late departure of the other train could of course be for all sorts of reasons, but it got me wondering - during permissive working at stations, do the rules allow for the signal to be cleared for the train in front and for it to be dispatched while the second train is still in motion?

And, considering fixed block signalling only, are there any other circumstances in which two trains are permitted to move within the same block?

In a nutshell, yes.

Yes it does

I'd be interested to hear a little more detail from ComUtoR (which part of the OP's question were you replying 'Yes' to?) and driver9000.

Have a look at TW1 20.4 which gives a clear instruction on moving towards a moving train under permissive working.

"When it is permitted" - which, according to TS2/3.3.4, does not include on platform lines.

They certainly can at Preston where the OP mentions.

Are you stating that this is permitted at Preston, or are you stating that the OP said this? (They didn't.)

I’m fairly sure that the rules don’t actually prohibit it

I certainly don't know it all rulebook-wise and am always happy to be educated, but TS2/3.3.4 seems clear with regards to platform lines.

 

[Nippy]

Yes we certainly don't clear the the signal for the first train to depart until the second is at a stand at Oxford.

 

[contrad!ction]

Yes we certainly don't clear the the signal for the first train to depart until the second is at a stand at Oxford.

Exactly the same at my place.

(Although the interlocking will let you and if you’re not careful ARS will kindly do it for you as well)

 

[MarkyT]

Yes we certainly don't clear the the signal for the first train to depart until the second is at a stand at Oxford.

I hope the new interlocking would prevent that if you ever (accidentally!) tried.