TPWS for Permanent Speed Restrictions

[Quickthorn]

Hi,

Can anyone tell me what speeds trigger TPWS set up before PSRs?

There was a helpful post here that showed how TPWS OSS is set up for signals (it was an extract of Network Rail Standard NR/SP/SIG/10138), and I was hoping that there might be similar information for TPWS PSR.

If not, I have some examples, and wanted to know what speed would trigger a TPWS stop:

60mph to 20 mph, grid 280 m from PSR on 1:120 falling gradient;

60mph to 20 mph, grid 330 m from PSR on 1:237 falling gradient;

60mph to 40 mph, grid 190 m from PSR on level gradient;

75mph to 50 mph, grid 785 m from PSR on 1:79 falling gradient.

Thanks for any help

 

[driver9000]

That is something Network Rail seem to keep very close to their chest. As a Driver I have always been told that information regarding trigger speeds for TPWS isn't given out, the only way we tend to find out is when a train gets tripped. I probably only know what maybe 3 OSS grids are set at.

 

[455driver]

I know several trip speeds!

We actually have one set of grids where the line-speed drops from 60 to 40 and the grids are set at 72, funnily enough they have never been tripped!

 

[A-driver]

The exact trigger speed will depend on the risk of speeding, how far away the grids are from the PSR, and the types of train cleared for the route amongst other things.

 

[Quickthorn]

Thanks for the replies.

Perhaps I ought to mention this is for building a route on Train Simulator, and I don't work in the rail industry myself. If exact speeds are hard to come by, then an educated guess for those examples would still be useful.

The traffic is mainly Sprinter type units and coal traffic, typically Cl66 + 20 or so HTA or similar. For the last example, I think freight is rare, and the 75 and 50 speeds only apply to units; all other traffic is 20 mph.

 

[A-driver]

Well think about the normal braking curve up to the speed limit and go for something around that. But its based on the worst performing train cleared for the route.

They are designed to prevent a train running over the lower speed at a speed high enough to become dangerous so not all PSRs will be gridded.

 

[Southern313]

I go for 10mph above the PSR that is associated with the grids...hopefully that'll keep me out the "off track club"

 

[A-driver]

I go for 10mph above the PSR that is associated with the grids...hopefully that'll keep me out the "off track club"

I think the worst grids I've encountered were those on the down Portsmouth approaching Sutton where it drops 60-40. The grids are miles away (well not quite miles but you get my point) on an uphill stretch and loads of people got tripped in 377s. The grids were set for freight at around 50 I think but most downloads of people tripped were a mile or 2/hour over the trip speed and the downloads showed that if they had kept the braking curve they had at time of setting the TPWS off they would be doing under 20 by the 40 boards!

 

[pendolino]

I go for 10mph above the PSR that is associated with the grids...hopefully that'll keep me out the "off track club"

Even approaching the stops? Sounds scary.

 

[A-driver]

Even approaching the stops? Sounds scary.

Southern always seemed o early strict with their 6mph policy approaching stops.

At places like kings x, moorgate and Cambridge 8-10mph is encouraged over the grids. Took a bit of getting used to for me after the years of edging up at 5-6.

 

[Southern313]

Lol, no, stick to the 6mph for the buffers...especially the ones at Warblington, Cosham and Bedhampton if you come in on a red! The looks you get from punters creeping in at that speed

 

[455driver]

Dont you love TPWS-

I asked how many incidents had occurred of trains over-running stations and going over level crossings but never got an answer, funny that. :roll:

I think that stuff like TPWS- is thought up by an organisation looking for problems to solve, many years ago they did a good job of sorting out the most regular incidents but as they improved things they had less to fix, now there is so little to fix they end up trying to solve "problems" which dont really exist.
The thing is if they dont do that then they are out of a job!

 

[pendolino]

You can't see the point of TPWS, is that what you're saying? Southall and Ladbroke Grove were problems that 'don't really exist'?

 

[455driver]

No that is not what I said, read my post again! :roll:

If you are stuggling (you obviously are) note the "-" after the TPWS!

 

[pendolino]

TPWS minus? No wonder I'm struggling.

 

[Zoe]

You can't see the point of TPWS, is that what you're saying? Southall and Ladbroke Grove were problems that 'don't really exist'?

TPWS would most likely have prevented the Ladbroke Grove collision but not Southall.

 

[pendolino]

TPWS would have prevented Ladbroke Grove but not Southall.

You could say TPWS prevented neither because it was introduced as a consequence of Southall & Ladbroke Grove (that's what I was getting at). But yes, even with it in place, TPWS is rarely effective at preventing a SPAD outright, but (hopefully) it mitigates the effects.

 

[Zoe]

You could say TPWS prevented neither because it was introduced as a consequence of Southall & Ladbroke Grove (that's what I was getting at). But yes, even with it in place, TPWS is rarely effective at preventing a SPAD outright, but (hopefully) it mitigates the effects.

I can understand the introduction of TPWS as a result of Ladbroke Grove (which even if it didn't prevent the SPAD, I believe it most likely would have prevented the collision) but why would Southall have been a motivation for its introduction when TPWS would not have prevented the collision? I seem to remember calls for full ATP at the time rather than TPWS.

 

[pendolino]

I can understand the introduction of TPWS as a result of Ladbroke Grove (which even if it didn't prevent the SPAD, I believe it most likely would have prevented the collision) but why would Southall have been a motivation for its introduction when TPWS would not have prevented the collision? I seem to remember calls for full ATP at the time rather than TPWS.

You'd best ask the ORR that question as that's what it says on their website.

 

[TDK]

Dont you love TPWS-

If you drive your train correctly you do not need to worry about TPWS
--- old post above --- --- new post below ---

Dont you love TPWS-


I think that stuff like TPWS- is thought up by an organisation looking for problems to solve, many years ago they did a good job of sorting out the most regular incidents but as they improved things they had less to fix, now there is so little to fix they end up trying to solve "problems" which dont really exist.

I just love these comments from new drivers, TPWS was instigated due to serious collisions that killled people, TPWS is a cheap effort yes but since it's installation has saved occurences serious incidents. Collisions, derailments etc. I drove trains before TPWS and when it was first introduced it was a pain especially driving slam door stock up to buffers but it has now been sorted out and to be honest is a safety measure that is needed. Sorry to be blunt with you 455driver but I have seen this before with newish drivers giving it the "I have been driving for years and years" with these comments and to be fair you have got to admit that TPWS is a way forward regarding safety of the railway!
--- old post above --- --- new post below ---

I can understand the introduction of TPWS as a result of Ladbroke Grove (which even if it didn't prevent the SPAD, I believe it most likely would have prevented the collision) but why would Southall have been a motivation for its introduction when TPWS would not have prevented the collision? I seem to remember calls for full ATP at the time rather than TPWS.

ATP was too expensive and believe it or not there is a price on human life when it comes to cost analysis with risk assessments

 

[A-driver]

If you drive your train correctly you do not need to worry about TPWS
--- old post above --- --- new post below ---

Well read what I put earlier about the grids approaching Sutton. Those trains which tripped the grids were all being driven correctly, 377s have fantastic breaks but have to be driven like a freight train there. All downloads were showing the trains were being driven correctly but they are still tripped.

 

[High Dyke]

I was involved in an incident last year where the driver activated the OSS approaching a diverging junction - the signalling equipment was working correctly. There was an issue with the voice comms from the driver, but we established that the equipment did what it should and stopped the train.

The controlling signal box at that location knew (from the panel) that TPWS was fitted, but didn't have any record of the speeds of the OSS loops or distances from the respective signal(s) the loops are placed.

 

[Kneedown]

We actually have one set of grids where the line-speed drops from 60 to 40 and the grids are set at 72, funnily enough they have never been tripped!

We've got a set similar to that on the Robin Hood Line. 75mph down to 50mph. Grids set at 76mph. Once again they've never been tripped........ which is good!

 

[TDK]

Well read what I put earlier about the grids approaching Sutton. Those trains which tripped the grids were all being driven correctly, 377s have fantastic breaks but have to be driven like a freight train there. All downloads were showing the trains were being driven correctly but they are still tripped.

If the grids are set incorrectly you still do not have anything to worry about as a driver and to be fair this is probably a rare instance, it was the same at balham on the up towards Victoria when TPWS was forst installed and NR adjusted the trigger speed.

 

[cjmillsnun]

You could say TPWS prevented neither because it was introduced as a consequence of Southall & Ladbroke Grove (that's what I was getting at). But yes, even with it in place, TPWS is rarely effective at preventing a SPAD outright, but (hopefully) it mitigates the effects.

TPWS was coming anyway. Both Southall and Ladbroke Grove would've been prevented by ATP (it was actually fitted to the HST involved in Southall but was isolated as there had been issues with it - solved by then - and the fact they weren't that keen on using it at the time.), and should've been fitted to all stock on those lines IMO.

 

[Bald Rick]

TPWS is rarely effective at preventing a SPAD outright

You'd be surprised. Compare SPAD rates per million train km now to 15 years ago, and you will see they have dropped to less than a third of what they were. Even if half of this is down to changes to driver training, behaviour, and other SPAD mitigation measures (an optimistic assumption), that still means that TPWS has cut out at least a third of SPADs.

 

[notadriver]

I think it's pointless to have TPWS for permanent speed restrictions (which is what this thread is about - not Spads) A permanent AWS magnet is sufficient.

 

[A-driver]

I think it's pointless to have TPWS for permanent speed restrictions (which is what this thread is about - not Spads) A permanent AWS magnet is sufficient.

So when you have a 30mph curve on a 125mph running line you think no TPWS is needed?! So if the driver cancels the AWS but fails to bring the trains speed down in time and runs the train into a field killing dozens that is acceptable?!

 

[notadriver]

Where is there a speed change from 125 mph straight down to 30 not controlled by signals ? Don't forget that temporary and emergency speeds don't have TPWS overspeed loops either. They rely on the professionalism of the driver and that's enough for me.

 

[GB]

Humans make mistakes and everyone has an off day now and then.