Tpws speed settings

[Layaboutlarry]

Hi,

I know it may be a random question but I was just wondering if there is anywhere we can find out what certain twps grids are set at?

Thanks in advance

 

[swt_passenger]

Hi,

I know it may be a random question but I was just wondering if there is anywhere we can find out what certain twps grids are set at?

Thanks in advance

Every time this has come up before the answer from drivers has been that they are intentionally not published.

 

[bengley]

I've got the speeds for my routes but most routes don't give the information to drivers.

 

[Jamesb1974]

Deleted

 

[scott118]

Hi,

I know it may be a random question but I was just wondering if there is anywhere we can find out what certain twps grids are set at?

Thanks in advance

without being rude, however, to what benefit, would this be to yourself?

'Over speed' grids are determined by the line speed, track curvature, gradients etc. These parameter's, also apply, to TPWS+.

 

[Rich McLean]

You won't know the speeds until someone trips them. Those drivers who do, then pass this round the mess room. Over the years this info if then collated for various routes to a point where most time served drivers know the "unofficial" speed of the majority of the grids on the routes that they sign. However that doesn't stop NR changing the trip speeds.

The trip speeds are never officially released, as if you do trip them in normal conditions then you are driving to fast at that point (not slow enough on approach to restrictive aspects, too fast for a lower speed turnout etc) anyway.

If Instructors are giving out speeds, then I suspect that it's "unofficial".

Certainly no need for passengers or "Cranks" to know what these are.

 

[class 9]

The trip speeds are never officially released, as if you do trip them in normal conditions then you are driving to fast at that point (not slow enough on approach to restrictive aspects, too fast for a lower speed turnout etc) anyway.

Not necessarily, I was on I light loco and tripped a OSS approaching a 20 PSR a few years ago, the brake was already in and we came to stand a loco length short of of the commencement board.

 

[Layaboutlarry]

I only ask out of curiosity just to wonder how much "Lee-way" we get as drivers

 

[AlterEgo]

I only ask out of curiosity just to wonder how much "Lee-way" we get as drivers

That's why they don't get publicised.

 

[louis97]

In Anglia between Ely and Norwich, think between Brandon and Thetford, just after a PSR Warning Indicator there is a similar sign which says 'TPWS 69' or something like that on it. Can only presume this is the speed the grids are set at - it is on the approach to a 60mph PSR I think.

 

[kevconnor]

Please excuse my ignorance but would a Tpws speed settings be a warning system so say if the PSR were 60 then it may flag up a warning of say you are 5mph over? Also what is the result of tripping one? Is it an in cab alert or automatic break application or does it send a warning somewhere that a train has triggered the warning.

 

[ComUtoR]

I only ask out of curiosity just to wonder how much "Lee-way" we get as drivers

Your supposed to driver like its not there. TPWS is an "invisible" system you should be driving about all day without thinking about TPWS
--- old post above --- --- new post below ---

Please excuse my ignorance but would a Tpws speed settings be a warning system so say if the PSR were 60 then it may flag up a warning of say you are 5mph over?

They can trip at 0.1mph over the set speed.

Also what is the result of tripping one? Is it an in cab alert or automatic break application or does it send a warning somewhere that a train has triggered the warning.

In cab alert, full brake application with no override.

We have an onboard system that sends an alert if you have a full brake application.

 

[Tomnick]

There was an overspeed sensor on the approach to a 55mph PSR at one of my boxes - trains that got caught by it usually came to a stand right outside the box, barely 100 yards beyond the start of the PSR. Based on that alone, I'd say that it's quite easy to get caught without going "too fast"!

Please excuse my ignorance but would a Tpws speed settings be a warning system so say if the PSR were 60 then it may flag up a warning of say you are 5mph over? Also what is the result of tripping one? Is it an in cab alert or automatic break application or does it send a warning somewhere that a train has triggered the warning.

No, it either activates (if the train is exceeding the set speed) or it doesn't. Full brake application (except WCRC) and flashing red "brake demand" light in the cab.

 

[ComUtoR]

There was an overspeed sensor on the approach to a 55mph PSR at one of my boxes - trains that got caught by it usually came to a stand right outside the box, barely 100 yards beyond the start of the PSR. Based on that alone, I'd say that it's quite easy to get caught without going "too fast"!

If a full brake application stopped the train 100yrds beyond the PSR then I have doubts that a normal application would have brought the train within the speed limit.

We have a predictor that can determine if you were able to bring the speed down in time IF you applied the brakes, and what brake step. The problem is that the system doesn't ask IF. It simply stops you. Without it you may still be going at speed. TPWS is a good system.

TPWS is also set with the highest speed/heaviest traction along that stretch (or so I'm taught) so passenger services tend to get caught all lot because we can brake relatively. The system is Arm/Trigger if the speed is exceeded.

 

[AndyPJG]

No, it either activates (if the train is exceeding the set speed) or it doesn't. Full brake application (except WCRC) and flashing red "brake demand" light in the cab.

Like!

Edit:-
And once at a stand, contact signaller immediately for instructions?

 

[Tomnick]

If a full brake application stopped the train 100yrds beyond the PSR then I have doubts that a normal application would have brought the train within the speed limit.

We have a predictor that can determine if you were able to bring the speed down in time IF you applied the brakes, and what brake step. The problem is that the system doesn't ask IF. It simply stops you. Without it you may still be going at speed. TPWS is a good system.

TPWS is also set with the highest speed/heaviest traction along that stretch (or so I'm taught) so passenger services tend to get caught all lot because we can brake relatively. The system is Arm/Trigger if the speed is exceeded.

The ones that I saw for myself all appeared to be doing well under 55mph (braking heavily, obviously) by the time that they reached the start of the PSR. I know that they'll at it afterwards to determine whether you'd have managed to get down in time or not, but on the other hand it does seem as though some adjustment to braking technique is required in some locations to account for the TPWS (for trains with better brakes in particular), effectively braking first for the TPWS and then again for the PSR itself - but how can you do that if you don't know what the set speed is?

It is a good system, I agree, and its limitations are perfectly understandable.

 

[ComUtoR]

effectively braking first for the TPWS and then again for the PSR itself - but how can you do that if you don't know what the set speed is?

.

Its very bad driving. We used to have published TPWS speeds but what happened is that Drivers would aim for that speed to clear the TPWS then end up tripping it by fractions or still running through speeds because they clear the TPWS and then coast, keep going, effectively circumventing the reasons TPWS exists.

From investigation they find that people are driving to the TPWS and not aiming for the PSR the TPWS trips because of a lack of concentration or good driving techniques.

It was the same with SPADS and the 15 at the magnet. Drivers would hit the magnet perfectly but still SPAD the signal (going 14 mph !)

Same with buffer stop hits. Drivers literally drive over the grids at 9.9 mph then hit the buffers :/

I'm in the camp where I don't believe speeds should be published. Especially as another problem was that the published speed wasn't always accurate.

 

[HarleyDavidson]

The OSS trip speeds should be shown in route learning packs. I know that ours are.

 

[W230]

None of ours are published. The only way you find out is by tripping them. However, some seem set a bit strangely slow IMHO but I tend to think of them as a bit of a crude one size fits all sort of safety device. As said, if it's set at 75mph then going at 74.9mph won't set it off...

I believe a couple of years ago ASLEF were trying to get the speeds published though never heard anything more so guessing they changed their mind or it just never happened.

I'm not sure I agree that tripping one necessarily equals bad driving but then I would say that under the circumstances...

They are set at different trigger speeds for freight and passenger.

 

[ComUtoR]

I'm not sure I agree that tripping one necessarily equals bad driving but then I would say that under the circumstances...

Please don't get me wrong. It's not tripping them its the driving to TPWS speeds that really isn't wise. We have loads that trip whilst on ECS. Its an industry wide thing too.

They are set at different trigger speeds for freight and passenger.

Not that I'm aware of. They get set at a set speed for ALL units over the line. They decide the speed based on the highest speed/heaviest traction that needs to stop before the point of conflict/danger point etc.

*Unless freight TPWS equipment is different ? Its a simple system. Its armed and the trigger loop is only active for a specific time and they set the speed by the distance the loops are from the PSR and how far they are apart ?

At least this is what I've been taught. I'd love the more techy and knowledgable folks to confirm, correct, and enlighten us

 

[MarkyT]

They are set at different trigger speeds for freight and passenger.

Effectively yes. There's a simple timer onboard the traction which is started at the arm loop then if you get to the trigger loop before it has expired you get tripped, simple as that! The timer for freight is slightly longer so you have to be going slower in order not to be tripped. The set speed is configured by the distance between the loops, and based on the standard braking curves assumed for the different types of traffic. I understand most locos have a switch to select freight or passenger mode that adjusts the timer as appropriate for what is being hauled.

 

[W230]

The only reason I know they're different is through reading about them in the WON. Whenever they move the grids they publish it in there obviously but also publish a freight and passenger speed (not that I ever remember them).

MarkyT's explanation as to how the differentiate between the two makes sense as I know it's pretty simple equipment and so had wonders how it could tell if you were freight or passenger.

 

[FordFocus]

My company doesn't post the trip speeds. The only reason I've been given is that if drivers know the trip speed they will put the brake in later and drive differently. Potentially causing more TPWS activations because the brakes weren't as good as normal.

However!!! There was an issue with a resignalling scheme with a few drivers getting tripped at an OSS that according to NR, meets the current standards. The company eventually published the trip speed and no more TPWS activations have happened to my knowledge has happened since.

 

[ComUtoR]

The company eventually published the trip speed and no more TPWS activations have happened to my knowledge has happened since.

We had a recent one. 60 onto a 40 with a TPWS set at 55. The number of trips was staggering till they published the speed. I think seeing it a 55 and the location of the PSR made people think twice. (they were pretty much all ECS trips)

 

[notadriver]

My toc publishes the relevant speeds and in the WON whenever they install new TPWS grids they tell you the set speeds.
--- old post above --- --- new post below ---

Please excuse my ignorance but would a Tpws speed settings be a warning system so say if the PSR were 60 then it may flag up a warning of say you are 5mph over? Also what is the result of tripping one? Is it an in cab alert or automatic break application or does it send a warning somewhere that a train has triggered the warning.

So the TPWS is there to ensure trains are slowing down for a PSR. They are not used to make sure the train is observing the speed limit.

If let's say the current speed limit is 70 mph and there is PSR 15 mph ahead (a sharp bend) the driver has to slow the train in such a way that doesn't trip TPWS and doesn't lose too much time by braking too hard and crawling at 15 mph for 5 minutes needlessly and losing time.

 

[Rich McLean]

Personally if you are taught the route correctly, you will be taught to drive in a way that never presents a risk to tripping a grid (braking locations, correct braking curve etc..), unless there is a change, and the grid is moved. If the Grid is moved then you should be suitably advised and adjust your driving technique to suit.

If you do trip one that has been moved, as long as you carry out all actions correctly, then following a download and after a quick chat with your manager, you will know the trip speed and adjust your driving accordingly.