Strange SPAD at Chalfont & Latimer?

[martin_wynne]

42 minutes ago, big jim said:

one thing that does apply to both sets of rules though, if you pass a signal at danger you dont make any futher moves until you gave spoken to the signaller and have permission to proceed!

 

 

Hi Jim,

 

What are the rules if you don't know you passed a signal at danger? If for example it looked yellow in sunlight?

 

Martin.

[big jim]

quite simply dont move until you have permission from the signaller

 

i (embarrassingly) once tripped an overspeed near chesterfield, supposedly going too fast for a fixed speed restriction and my tpws 4 dropped the brake and then continually chirps up ‘overspeed please contact signaller’ and shows a brake demand light (red) until i stop and acknowledge it with the AWS button (then reset using a couple of other buttons), had i had older tpws fitted it just have a brake application and demand light no audible warning, therefore i wouldnt know the reason i was being bought to a stop so id have to speak to the signaller in case i had had a spad, a ‘reset and go’ is one of the biggest no no’s now and career suicide if you do it and get caught! 

 

there is also a rule that when you see a spad indicator lit you must stop immediately and contact the signaller even if you know for definate you havent spadded otherwise you could be heading towards a collision with something that has!

 

of course, the above is applicable to NR  metals but the bit about not moving applies to LUL too

Edited July 12, 2020 by big jim

[PaulRhB]

4 minutes ago, martin_wynne said:

 

Hi Jim,

 

What are the rules if you don't know you passed a signal at danger? If for example it looked yellow in sunlight?

 

Martin.

That’s why you’re supposed to contact the Signalman if you have an unexplained brake application before moving. Whichever brake system you use it gives the extra chance to catch a SPAD. 

It’s still a SPAD and the investigation would include either cab video checks or signal sighting at the appropriate time to see if it could be recreated. It might exonerate the driver but it’s still a SPAD and it would then seek to advise what caused it so the relevant department can address it.

It’s not always the railway either. We had a driver report irregular aspects in the dark and it turned out to be a new supermarket till’s ‘call supervisor lights’ that happened to appear in their sight line just as they were expecting to see the signal causing multiple lights to appear. That was solved by getting the side of all the till lights pointing towards the railway blanked off with the help of the store. 

[caradoc]

7 hours ago, big jim said:

once tripped an overspeed near chesterfield, supposedly going too fast for a fixed speed restriction and my tpws 4 dropped the brake

 

Something that always baffled me, when TPWS was introduced on the approach to PSRs, was why the speed setting was not publicised; This being somewhere between the line speed and the actual PSR. It is perfectly possible for a train to be travelling faster than the speed setting (but not faster than line speed at that point and not therefore speeding), but still be perfectly capable of reducing speed to the correct level before reaching the start of the PSR. We in NR Control had no record of PSR speed settings either, whenever such an incident occurred we had to contact the local S&T staff to get that information.

 

7 hours ago, PaulRhB said:

It’s not always the railway either. We had a driver report irregular aspects in the dark and it turned out to be a new supermarket till’s ‘call supervisor lights’ that happened to appear in their sight line just as they were expecting to see the signal causing multiple lights to appear.

 

Similar incidents occurred with roadwork temporary traffic lights on or near overbridges. Sometimes a simple adjustment to the positioning of the lights sufficed, at other times complicated negotiations with the local council were required !

 

[PaulRhB]

33 minutes ago, caradoc said:

Something that always baffled me, when TPWS was introduced on the approach to PSRs, was why the speed setting was not publicised; This being somewhere between the line speed and the actual PSR. It is perfectly possible for a train to be travelling faster than the speed setting

We do have a list of the PSR set speeds in the box but I think like approach control on signals the TOC’s don’t tell the drivers because it may encourage later braking. 

The speed for the sensor is set for the braking in worst conditions with the lowest permitted braking curve. I think the only way adapt to different stock and braking variances is the preset on the stock? 
I don’t know how that works exactly but we do get FOC locos on railtours getting activations as theirs is set lower for freight braking and speed. 
 

[St. Simon]

1 hour ago, caradoc said:

 

Something that always baffled me, when TPWS was introduced on the approach to PSRs, was why the speed setting was not publicised

 

Hi,

 

TPWS Set Speeds for signals or PSRs are not published, at least for drivers, to prevent drivers 'driving to the TPWS' in the same way that some car drivers drive to avoid speed cameras (i.e, dipping their speed momentarily as they go past the camera to avoid being caught speeding).

 

I know that the vast majority of train drivers wouldn't even think about doing it, but there's always the possibility and not publishing the set speeds for drivers is the easiest way of closing that hole in the Swiss Cheese.

 

The Set Speeds for OSS' are effectively 'hard-wired' in the positioning of the Arming and Trigger Loops, as it is the separation between them in conjunction with the trains TPWS timer value, that defines the set speeds.

 

16 minutes ago, PaulRhB said:

The speed for the sensor is set for the braking in worst conditions with the lowest permitted braking curve. I think the only way adapt to different stock and braking variances is the preset on the stock? 
I don’t know how that works exactly but we do get FOC locos on railtours getting activations as theirs is set lower for freight braking and speed. 
 

 

Most the adapting is done by adjusting the timer values on the equipment fitted to the train, although I don't think you can adapt it to certain classes, only between passenger and freight settings (and I'm not sure how you do that to be honest).

 

There are more and more trips occurring with modern stock with enhanced brakes as they can legitimately brake closer to the signal (because of their better brakes) and go over an OSS loop at a speed higher than the set speed without danger. There is a proposal to have the timer values on these units changed to prevent that, therefore creating a third set speed.

 

If you want to make the TPWS work specifically to protect a certain train class and conflict, you can modify the design and location of the Loops on the track, like we did for the Class 345's between Padding and Stockley.

 

Simon

Edited July 13, 2020 by St. Simon

[Nick C]

8 hours ago, martin_wynne said:

 

Hi Jim,

 

What are the rules if you don't know you passed a signal at danger? If for example it looked yellow in sunlight?

 

Martin.

If a signal is showing an unclear aspect drivers are required to stop and phone it in - including glare on the lens making it difficult to see clearly.

[big jim]

Regards the overspeed at chesterfield it’s set to 62mph apparently, the grids in question are within a 70mph PSR area a good 1/2 mile before the 60 actually starts, in my opinion set far too low for the location, they could easily be set to 65 and still be able to safely brake down to 60 

[NorthEndCab]

1 hour ago, big jim said:

Regards the overspeed at chesterfield it’s set to 62mph apparently, the grids in question are within a 70mph PSR area a good 1/2 mile before the 60 actually starts, in my opinion set far too low for the location, they could easily be set to 65 and still be able to safely brake down to 60 

I seem to recall the grids for the 80 through Wellingborough on the Up are set at 80 and are a little way before the PSR, that caught quite a few people out. 

[caradoc]

3 hours ago, St. Simon said:

TPWS Set Speeds for signals or PSRs are not published, at least for drivers, to prevent drivers 'driving to the TPWS' in the same way that some car drivers drive to avoid speed cameras (i.e, dipping their speed momentarily as they go past the camera to avoid being caught speeding).

 

I know that the vast majority of train drivers wouldn't even think about doing it, but there's always the possibility and not publishing the set speeds for drivers is the easiest way of closing that hole in the Swiss Cheese.

 

That's a fair point; Is the danger perhaps that Drivers would slow to the TPWS setting but then accelerate again before the actual PSR ? And wasn't that an issue when TPWS for buffer stops was set at 5mph but positioned way before the actual platform end ?

 

[big jim]

22 minutes ago, caradoc said:

 

 wasn't that an issue when TPWS for buffer stops was set at 5mph but positioned way before the actual platform end ?

 

Yes, manchester Piccadilly was a pain for it, you had to slow to 5mph then power up to make it to the blocks! 
 

 

Edited July 13, 2020 by big jim

[Titanius Anglesmith]

14 hours ago, big jim said:

 

 

you can see the signal tripcock in action in the video linked to further back in the thread, ill see if i can get the time mark and edit this post accordingly

 

...

 

EDIT: tripcock arm in action at 38:55 on the linked video

 

Being pedantic, that's a trainstop not a tripcock.  The tripcock is the arm on the train that interacts with the trainstop. 

[St. Simon]

1 hour ago, caradoc said:

 

That's a fair point; Is the danger perhaps that Drivers would slow to the TPWS setting but then accelerate again before the actual PSR ? And wasn't that an issue when TPWS for buffer stops was set at 5mph but positioned way before the actual platform end ?

 

 

Yes, although speeding up after a set of loops is still possible accidently, the not publishing speeds is to prevent the 'malicious' act of deliberately ensuring you are not tripped.

 

Simon 

[phil-b259]

4 hours ago, big jim said:

Regards the overspeed at chesterfield it’s set to 62mph apparently, the grids in question are within a 70mph PSR area a good 1/2 mile before the 60 actually starts, in my opinion set far too low for the location, they could easily be set to 65 and still be able to safely brake down to 60 

 

As has been mentioned TPWS trip speeds are generally set for 'worst case' scenarios - e.g. wet rails, long / heavy trains and the braking abilities of the worst traction unit. If its a nice dry day, you have a light / short train or the loco is a very new one with excellent brakes then it can easily seem like the TPWS is over cautious.

 

The other factor to remember is that Freight and Passenger trains have different timers on board (to take into account the better stopping ability of the former). Over time its quite possible that improvements in Freight locos / wagons mean the difference between the two classes of trains is not so pronounced and the timer setting might need to be revised to take the improvements into account.

 

 

NOTE: The on train TPWS timer is set for a SPECIFIC DURATION under Vehicle approval regulations for the train type (Freight or Passenger) and its duration CANNOT be altered by ANYONE. Any changes would require a change in the standards to be made by the RSSB

 

 

[caradoc]

2 hours ago, St. Simon said:

Yes, although speeding up after a set of loops is still possible accidently, the not publishing speeds is to prevent the 'malicious' act of deliberately ensuring you are not tripped.

 

 

2 hours ago, phil-b259 said:

As has been mentioned TPWS trip speeds are generally set for 'worst case' scenarios - e.g. wet rails, long / heavy trains and the braking abilities of the worst traction unit. If its a nice dry day, you have a light / short train or the loco is a very new one with excellent brakes then it can easily seem like the TPWS is over cautious.

 

Good points, but what it meant in practice of course was that when TPWS was first installed for PSRs, TPWS interventions were inevitable until Drivers gained an understanding of roughly what the speed setting was. When such an incident occurred we always advised the relevant TOC/FOC the speed setting for the purpose of their investigation, no doubt this information was passed on !

 

 

[big jim]

27 minutes ago, caradoc said:

When such an incident occurred we always advised the relevant TOC/FOC the speed setting for the purpose of their investigation, no doubt this information was passed on !

 

 

 

hence why i know its set to 62mph!

[PaulRhB]

3 hours ago, St. Simon said:

not publishing speeds is to prevent the 'malicious' act of deliberately ensuring you are not tripped.

Malicious act? It’s to make sure they assume it’s the posted speed and they aren’t late braking, so they treat it with caution, the act of not tripping it is always the intention  

I don’t think ‘malicious’ comes into official thinking and we aren’t banned from telling anyone if they ask, it’s certainty not what has been assumed when I was involved in an investigation, and if it did I’d be very worried who had come up with the theory. 
Much like approach controls, drivers are aware they exist and we aren’t banned from telling them but you do have to assume they will remain red. 

Edited July 13, 2020 by PaulRhB

[Mark Saunders]

4 minutes ago, PaulRhB said:

Malicious act? It’s to make sure they assume it’s the posted speed and they aren’t late braking, so they treat it with caution, the act of not tripping it is always the intention  

I don’t think ‘malicious’ comes into official thinking, it’s certainty not what has been assumed when I was involved in an investigation, and if it did I’d be very worried who had come up with the theory. 

 

If only there was the same debate about the observation of traffic lights and speed limits on the roads.

 

The number of people who do not understand that there is a difference in National Speed limits depending on the vehicle type!

[PaulRhB]

1 minute ago, Mark Saunders said:

 

If only there was the same debate about the observation of traffic lights and speed limits on the roads.

 

The number of people who do not understand that there is a difference in National Speed limits depending on the vehicle type!

There is but it’s creeping in through black boxes for insurance. With roadside average speed networks it’s only a matter of time until it uses the reg to identify the vehicle speed max. The image technology is already there it’s just the political will with it being rather unpopular as it gets lumped in with much wider road safety. 
The railway standards are much higher already due to the wider public responsibilities and the organisation allows for monitoring to be installed. About the only thing not recorded is the Driver or Signalman’s physical movements, all communications and nearly every button press and control input is logged somewhere. 

[roythebus]

A few points raised (and destroyed) in this post; from my rather ancient signed route knowledge of the Met Line when I was a guard at Rickmansworth in 1973 and a few years before that at Parsons Green and a as BR driver post 1974.

 

The LT train stop/trip cock won't prevent any train from passing a signal at danger. What it will do is make an emergency brake application by opening  a valve on the train brake pipe (on older stock) or break the brake continuity wire on later stock. 

 

Once a driver has "hit a stick" (to use LT terminology) or a SPAD to use modern terminology, he has to follow the following procedure (apply the rule in old terminology): if it is an automatic signal (signal plate will show the prefix A) the driver can reset the trip cock and continue at caution after waiting 2 minutes until he has passed 2 signals displaying a clear aspect. If it is a controlled signal (with a box code on the signal plate) he must contact the signalman before proceeding. A signal plate displaying the letter X is the last automatic signal before a controlled area and must be treated as a controlled signal.

 

The Met has a mixture of traditional LT two aspect signals and BR style 3 or 4 aspect signals from Harrow on the Hill to Amersham. It doesn't have AWS or tWPS due to the presence of the centre 4th rail. Signalling on that line was set for the days of unfitted goods trains which shared the fast and slow lines when the line was quadrupled in the early 1960s. The local lines south of Moor Park had disc style distant signals, but these were all removed many years ago.

 

From information gleaned from a train drivers' Facebook group the Chiltern driver is an experienced driver with many years service. The same group reports that it is fairly common for Chiltern trains to be tripped on debris on the Met for some reason. It also reports the driver "hit the stick"/SPAD, reset the trip cock and continued. Whether or not he contacted the signalman is not mentioned. In continuing, the train ran through the trailing points for the Chesham branch as the road was set for the northbound Met train which was stationary in the northbound platform with the signal there displaying a proceed aspect for the Chesham branch. That signal returned to danger as soon as a the Chiltern train occupied the track section ahead of the signal. The layout at Chalfont is a facing crossover between northbound and southbound lines with a trailing point on the southbound line which leads to the Chesham branch. No switched diamonds involved, all plain points.

 

So, enough of the speculation, we'll have to find out from the RAIB what actually happened and why.

Edited July 13, 2020 by roythebus

[big jim]

It’s not just the met that gets spurious tripcock activations, I’ve been stopped by blocks of Snow and ice that have fallen off vehicles on Bentley heath crossing near dorridge And regularly as pointed out elsewhere after ballast drops where the shoulder is too high

 

 

[DY444]

Report is out. 

 

https://tinyurl.com/nfwf685n

 

What a shambles on the Chiltern side.  Could have turned out very badly indeed.  Thankfully the Chiltern driver was jolted out of his stupor in the nick of time, and the Met train was still on the approach side of its signal and its driver reacted promptly to it going back to danger.  Barely a cars length between them when the 165s stopped.