Uxbridge branch signals

[orienteer]

I notice on the westbound track towards Uxbridge, as the train pulls into each station, the signal is red, but it goes green as the train stops. This happens even when there isn't another train just ahead (having waited at Rayners Lane!). How is this controlled, and what is the reason for it?

[q8]

It's the new standard being introduced system wide I believe. It is to prevent a train non stopping a station from passing through at a speed greater than the starting signal overlap allows. This is usually 5 mph. The same system is in operation on the ELL as well

It is controlled by a timing relay on the platform track circuit.

[orienteer]

Thanks q8, your clear answer rather belies your sig line!

[Deleted]

q8 said:

It's the new standard being introduced system wide I believe. It is to prevent a train non stopping a station from passing through at a speed greater than the starting signal overlap allows. This is usually 5 mph. The same system is in operation on the ELL as well

It is controlled by a timing relay on the platform track circuit.

How often do trains non-stop a station unless they're on special working? (Have i just answered my own question?? )

[setttt]

sturdjos said:

How often do trains non-stop a station unless they're on special working? (Have i just answered my own question?? )

More commonly due to station closure.

[Deleted]

setttt said:

More commonly due to station closure.

Or if the train is defective and or running empty as some do. I must admit I disagree with the idea, as it is putting unnecessary red signals in front of the driver.

[setttt]

metapprentice said:

I must admit I disagree with the idea, as it is putting unnecessary red signals in front of the driver.

Just what I was thinking... Seems daft really

[Deleted]

unless the sites were never designed with a full speed overlaps and i know that the hillingdon area of the met/picc is JTC (jointless track circuits) and is the same design as the bakerloo which if memory serves me right also as the same design that platform starters are appoached controlled.

[Harsig]

The irony is that the Uxbridge Branch can reasonably expect to see several trains a day that do not stop at stations. These are Engineers trains going to and from Ruislip Depot.

[orienteer]

Well, there were plenty of red lights eastbound last night: "signal failure at Ruislip". After taking 50 minutes to get from Uxbridge to Ruislip, I gave up and returned home!

I wonder whether the "stop and proceed" rule, at 10mph, is really necessary on open sections in clear visibility. The operator must be able to see as far as the next signal.

[setttt]

orienteer said:

I wonder whether the "stop and proceed" rule, at 10mph, is really necessary on open sections in clear visibility. The operator must be able to see as far as the next signal.

There's not much you can do about the slow speed business, at least not when it comes to stock which is fitted with SCAT (speed control after tripping), which prevents the train exceeding a 5(?)mph for 3(?) minutes after the initial tripping. I know the 73ts has this, but I'm not sure about the 'A' stock.

[CSLR]

orienteer said:

I wonder whether the "stop and proceed" rule, at 10mph, is really necessary on open sections in clear visibility. The operator must be able to see as far as the next signal.

Anybody - please correct me if I am wrong, but I think that the reasoning is that an object on the line, broken rail, etc, could affect the track circuit and put the signal to danger. Even when there is a general signal failure, the possibility of some other problem in the area of failure cannot be ruled out. For safety reasons, the requirement to proceed with caution, must therefore still be observed.

[Admin Team]

cslr said:

Anybody - please correct me if I am wrong, but I think that the reasoning is that an object on the line, broken rail, etc, could affect the track circuit and put the signal to danger. Even when there is a general signal failure, the possibility of some other problem in the area of failure cannot be ruled out. For safety reasons, the requirement to proceed with caution, must therefore still be observed.

Far from correcting you, I'm supporting this view 100%!

The problem is usually unknown - particularly if it's the first train through a 'failed' signal.

There are a myriad of possibilities. Forget 'speed limiters' and 'SCAT's' etc. The CORRECT answer is that a train can only proceed at a speed at which it is able to stop short of ANY obstruction.

This could be a bit of metal, a Tesco trolley - maybe even a TRAIN!!!

I (and others) can give chapter and verse on the procedures involved here. Follow the rules at all times - they're there for a reason! Many can also give examples of why the rules involve passing two consecutive signals etc....

Remember that railway operating procedures are designed around the failsafe principle.

[Deleted]

That's quite right - you'd never see a broken rail in time if you were doing over 10mph.

[Colin D]

The rule used to be that you could stop safely for any object that might cause a red 'un. Yes that would incude a broken rail, so you had to keep an eye on the track and look ahead. So slow and easy is the only safe way

[Deleted]

setttt said:

There's not much you can do about the slow speed business, at least not when it comes to stock which is fitted with SCAT (speed control after tripping), which prevents the train exceeding a 5(?)mph for 3(?) minutes after the initial tripping. I know the 73ts has this, but I'm not sure about the 'A' stock.

Below 10mph.

All stock now has SCAT.

[Deleted]

setttt said:

There's not much you can do about the slow speed business, at least not when it comes to stock which is fitted with SCAT (speed control after tripping), which prevents the train exceeding a 5(?)mph for 3(?) minutes after the initial tripping. I know the 73ts has this, but I'm not sure about the 'A' stock.

In terms of Slow Speed, there are ways round it, in terms of SCAT there isnt.

SCAT will only alow movement via the Slow Speed Circuit for three minutes. You still have to select Slow Speed on the CDU. This limits you speed to 8 mph

If the full speed circuit was not available the train would have to be moved in Slow Speed, this would mean that the train would have to be withdrawn from service at the first possible occasion. Once the train is out of service, the "Slow Speed Cut Out" can be operated which allows you to reach full speed via the Slow Speed Circuit.

The only way you will know that either one of the safety circuits has failed will be that you will get an emergency application of brakes when that circuit is selected via the CDU.

Hope that helps.

[Tom]

metapprentice said:

I must admit I disagree with the idea, as it is putting unnecessary red signals in front of the driver.

Maybe so, but it does enforce the speed check at the starter and hence prevent trains which should be passing at 5mph continuing though above the speed limit. If a train passes through unchecked and the driver doesn't comply with the line speed it is possible that the overlaps on signals ahead could become compromised.

[Tom]

aetearlscourt said:

unless the sites were never designed with a full speed overlaps and i know that the hillingdon area of the met/picc is JTC (jointless track circuits) and is the same design as the bakerloo which if memory serves me right also as the same design that platform starters are appoached controlled.

Mainly because the sites were all designed after the standard changed ;D

If at all possible a starter should be given a full speed overlap, if that is not possible it should be the highest possible speed but not any lover than 35kph.

But the issue as posted previously is not with the overlap of the starter but the signals beyond.

[Deleted]

tom said:

Maybe so, but it does enforce the speed check at the starter and hence prevent trains which should be passing at 5mph continuing though above the speed limit. If a train passes through unchecked and the driver doesn't comply with the line speed it is possible that the overlaps on signals ahead could become compromised.

Not if the starter is green and the next signal is green and can be seen. This is the case at a few of those stations along there.

[Deleted]

metapprentice said:

Not if the starter is green and the next signal is green and can be seen. This is the case at a few of those stations along there.

This is a bit of a gray area. The official rule, which does not discriminate of whether you can see if the next signal is green or not, is 5mph past station starter. This is non-negotiable except in areas as authorised by the relevant line supplement.
For example on the District, we're allowed to pass through stations between Ravenscourt Park and Acton Town (inclusive) at 25mph.

If a driver goes faster than 5mph past a station starter because he can see the next signal is clear, what he may not see is the DMT with the radar gun...
I know what you're saying, MA, but "officially" it must be 5mph.

[Deleted]

also temple on the e/b has a full speed overlap and last time i was through there on a sunday about a year now it was doing more then 5mph this is the only time i have known a train in service to pass a station at line speed

[Deleted]

alanl said:

on the District, we're allowed to pass through stations between Ravenscourt Park and Acton Town (inclusive) at 25mph.

Are we? That's news to me! Must devote more time to reading the line supplement...

I had one of the District TOMs in the cab with me on that stretch the other day and he couldn't understand the 25 signs followed a few yards later by a 35 either - now we know!

[Deleted]

alanl said:

I know what you're saying, MA, but "officially" it must be 5mph.

Oh yeah of course. I was talking more in terms of Tom's post, as if the starter is green as is thenext signal (which can be seen) there is not the chance of a compramised overlap.

[Deleted]

adw said:

I had one of the District TOMs in the cab with me on that stretch the other day and he couldn't understand the 25 signs followed a few yards later by a 35 either - now we know!

Apparently the Picc drivers know too

districtdavesforum.co.uk/index.cgi?board=picc&action=display&thread=1133718239

[Harsig]

metapprentice said:

alanl said:

I know what you're saying, MA, but "officially" it must be 5mph.

Oh yeah of course. I was talking more in terms of Tom's post, as if the starter is green as is thenext signal (which can be seen) there is not the chance of a compramised overlap.

Until you reach the next red signal wherever that may be. Given that all the overlaps are calculated on the basis of the maximum speed that can be obtained by a train starting from rest at the previous station then failure to ensure that the train does so (or at least the approximation of doing so in the form of 5mph at the station starter) means that when ever a train finally approaches a red signal it could be travelling at a speed which exceeds the design speed of the relevant signal overlap.

[Tom]

metapprentice said:

Oh yeah of course. I was talking more in terms of Tom's post, as if the starter is green as is thenext signal (which can be seen) there is not the chance of a compramised overlap.

And you last calculated an overlap when??
It is exactly for the reasons Harsig posted.

harsig said:

Until you reach the next red signal wherever that may be. Given that all the overlaps are calculated on the basis of the maximum speed that can be obtained by a train starting from rest at the previous station then failure to ensure that the train does so (or at least the approximation of doing so in the form of 5mph at the station starter) means that when ever a train finally approaches a red signal it could be travelling at a speed which exceeds the design speed of the relevant signal overlap.

Overlap calcs use data from the train peformance curve, which has assumed that when a train trips it has started from the previous station at rest if an 'all trains to stop station' and at line speed if it isn't.

In the case of the Uxbridge Branch, if all stations are defined as 'all trains to stop' the performance data assumes starting from 5mph and to ensure that this happens you have the speed check.

[Deleted]

q8 said:

It is to prevent a train non stopping a station from passing through at a speed greater than the starting signal overlap allows. This is usually 5 mph.

way back in my met days when i did a lot of nights, i used to take the 0118 staff ex baker st to ubridge,
as soon as the stick cleared at rayners, i wound up and kept the train at 50-55 till the approach to uxbridge,( if i didnt had any staff on board that is ) i think my record was around the 6 min mark from rayners to uxbridge ,

while i am on the subject of doing nights, the A60's were by far the most comfortable stock in which to sleep on, making a bed from 3 of the seats , i slept very soundly, upon doing the same on other stocks at a later date i have never seemed to have had such a restful night

aaaahhh how times have changed ----------- sighs !!!!!

[trainopd78]

For those DR staff reading the forum, the 25mph station starters are at Ravenscourt park, Stamford Brook, Turnham Green and Chiswick Park. Acton Town has 5mph station starters.