Train Protection & Warning System (TPWS)

[DownSouth]

(Split from another topic)

The ICE radio? It still works as a mobile phone! I might as well add to my dislike of acronyms...

I don't know what ICE stands for, nor ERTMS, so I can hardly comment. I imagine that they are both part of the machine that stops a locomotive from being a machine that hauls a train and turns it into a software bunny to simplify safeworking by reducing staff and making it even more complicated than the current radio systems, hence the reason we use the mobile phone to talk to sinalboxes and train control!

Mick

(Software, bah humbug!)

The relatives of those killed in the Waterfall crash might have a more balanced view on this matter. When a software system like ERTMS or the older ATP could have prevented seven people dying, you go and install it regardless of whether it makes a handful of drivers feel less important.

 

[ralphchadkirk]

The relatives of those killed in the Waterfall crash might have a more balanced view on this matter. When a software system like ERTMS or the older ATP could have prevented seven people dying, you go and install it regardless of whether it makes a handful of drivers feel less important.

No you don't. There has to be a cost-benefit analysis. It's for the same reason that not all drugs are approved by NICE for use in this country, even though they have some clinical benefit.

 

[Hydro]

No you don't. There has to be a cost-benefit analysis. It's for the same reason that not all drugs are approved by NICE for use in this country, even though they have some clinical benefit.

...and cost was why ATP was not adopted nationally, and even limited the installation of TPWS.

 

[notadriver]

The relatives of those killed in the Waterfall crash might have a more balanced view on this matter. When a software system like ERTMS or the older ATP could have prevented seven people dying, you go and install it regardless of whether it makes a handful of drivers feel less important.

In Britain we have TPWS instead and a lot more than 7 people will die on the roads every day!

 

[RPM]

The relatives of those killed in the Waterfall crash might have a more balanced view on this matter.

With the very greatest of respect to those unfortunate folks, I would suggest that they would have anything but a balanced view on the matter.

 

[Grantham]

The relatives of those killed in the Waterfall crash might have a more balanced view on this matter. When a software system like ERTMS or the older ATP could have prevented seven people dying, you go and install it regardless of whether it makes a handful of drivers feel less important.

Yes, The waterfall crash was caused by a lack of software, wasn't it?

BWAHAHAHAHAHAHAHAHAHAHAHAHAHA!!! Mate, he died at the controls and tipped on a curve...the "bad place" at 41.700 or so. More a medical problem than a safeworking one, don't you think?

Mick

 

[BestWestern]

Yes, The waterfall crash was caused by a lack of software, wasn't it?

BWAHAHAHAHAHAHAHAHAHAHAHAHAHA!!! Mate, he died at the controls and tipped on a curve...the "bad place" at 41.700 or so. More a medical problem than a safeworking one, don't you think?

Mick

BWAHAHAHAHAHAHAHAHAHAHAHAHAHA!!! - Eh?!! Does that mean something down there is Oz?

I'm guessing the point would be that certain systems, such as TPWS, would have potentially prevented this by applying brakes had the train failed to slow sufficiently for a speed restriction?!

That's how I read the post anyway. I must admit I'd never heard of the accident though, was it in Australia?! Roughly what happened; I presume Driver taken ill, train didn't slow down, rounded a bend too fast and left the track?

 

[Grantham]

Yes, much like that. The train came off on a 50km/h curve doing 127km/h or some such speed. The speed on the curve has now been lifted to 55km/h...

Does the train protection equipment in England put the brakes on if you're going too fast for a curve? Sounds like wishful thinking to me.

M

 

[BestWestern]

Yes, much like that. The train came off on a 50km/h curve doing 127km/h or some such speed. The speed on the curve has now been lifted to 55km/h...

Does the train protection equipment in England put the brakes on if you're going too fast for a curve? Sounds like wishful thinking to me.

M

TPWS works on some kind of electrical wizardry whereby it will detect the speed of a passing train and activate the brakes if required, so it can be used on the approach to a lower speed limit and halt a train which has failed to slow accordingly. It's also used at many signals and will trigger the emergency anchors if the train fails to stop at a Danger aspect. Of course it isn't everywhere, but there is plenty of it about!

Is there no equivalent system over there then?

 

[Grantham]

No, it sounds flash. Does it work on everything? I would have to imagine that it isn't actually foolproof...there are ways of inventing better fools, and dumbing down the job is one of those ways!

There is a trip system fitted to Sydney suburban and interurban trains. It dumps the air and applies the brakes when you run through a red signal. I say "when", because some shunting signals don't lower the trip, and some shunting manouvers have to pass through red signals with the permission of the signalman, basically an unsignalled move. The train will creep up to it very slowly, lose the air and have to be manually re-set to continue the shunting move. The same applies to a failed signal, they fail safe (red) and even if there is no aspect showing (very rare) the signal trip will still be up.

Of course, if you've sailed through a red signal with gay abandon, the air will go and you'll come to a screaming halt. The signals are all (well most of them) alarmed, and setting one off will start a flurry of radio messages and phone calls, and bad things will happen to you...not what anyone wants!

We seem to be getting rather off topic, don't we?

Mick

 

[BestWestern]

Well, off-topic but interesting! Happy new year by the way, it must've reached you a while ago now, right?!

Anyway, what you've got there sounds a but like the system on the London Underground, they call it a 'tripcock'. Not entirely sure of the nuts and bolts but basically something trips a valve/lever on the side of the train if it runs a red, and puts the brake in. Some mainline stock is also fitted where they run over shared lines.

TPWS is fitted to everything on the main line, it has to be, along with AWS - Automatic Warning System - and OTMR, the 'black box' data recorders. Even steam locos have to be wired up if they want a main line certificate! AWS gives a bell or horn depending on the aspect of the next signal, the Driver has to hit a button to acknowledge and cancel the warning.

Then you also have a Driver's Safety Device foot-on-pedal arrangement, and a Vigilance. The Vig sounds if none of the controls have moved for between 60 - 90 seconds, requiring the Driver to release and re-press the DSD pedal. Finally there's a DRA - Driver's Reminder Appliance. That's a switch which is operated and glows red if the train is stopped in a platform with a red starting signal, providing another reminder to check the signal before deactivating the DRA and moving the train.

How Drivers manage to do all of that with just the two hands and feet I really don't know, but I imagine it keeps them awake! Like you say though, you can have all the systems in the world but people will always make mistakes. TPWS is the first national system which actually takes things out of the Driver's control, designed to catch errors rather than be fooled by them, unlike AWS which can be cancelled without the Driver truly acknowledging his signal, leaving him free to go tanking through a red or suchlike.

 

[notadriver]

I know guards that sit in the back cab detailing every time a driver exceeds the speed limit and reports them to management

As for TPWS taking things out of a drivers control - do you know what a reset and continue event is Bestwestern?

 

[BestWestern]

I know guards that sit in the back cab detailing every time a driver exceeds the speed limit and reports them to management

As for TPWS taking things out of a drivers control - do you know what a reset and continue event is Bestwestern?

I would take said Guards to one side and have words, what's that all about?! Jeez, who cares if it's a few miles over, and besides it's hardly unheard of to have a speedo discrepancy between different cabs!? :roll: Having said that, to use the Aussie example quoted above, if it was nearly a ton over the limit I may feel compelled to buzz my Driver up and ensure he isn't dead or suicidal!

Reset and continue is a very bad thing is it not?; I'd imagine bottoms being very firmly smacked if that was found out to be a regular occurrence!

 

[O L Leigh]

Train Protection and Warning System (TPWS) is actually a very simple system. The track equipment consists of two antenna (called loops) that, when live, transmit a radio signal to a receiver underneath the train. The first antenna is called the "arming loop" which starts a timer on the train. The second antenna is called the "trigger loop". If the train passes over the trigger loop before the timer has run down it will automatically trigger an emergency brake application.

There are two applications for TPWS, called "train stop loops" and "overspeed loops". Train stop loops are used at signals where the arming and trigger loops are placed immediately one after the other and will be energised whenever the signal is held at danger. This will stop any train that passes the signal without authority.

Overspeed loops are the ones that are most pertinent to the Waterfall crash. Sometimes these overspeed loops will be used in conjunction with train stop loops where there is a danger that a train that has passed a signal at danger without authority will not be stopped within the overlap of the signal. Therefore an emergency brake application can be triggered on a train BEFORE it reaches the signal itself if the driver fails to reduce the speed of the train on approach. However, overspeed loops are also found on approach to some speed restrictions where the reduction in speed is significant.

To drag this discussion back on-topic, TPWS may not have prevented the Waterfall crash but it WOULD have prevented the Chatsworth crash. A signal protecting a single line section is a prime location for fitment of TPWS. Even if the engineer had been busy texting his mates and not been paying attention to the road ahead, TPWS would have stopped the train before it fouled the single line. That the US Railroad authorities have no equivalent system is something that I think will need to be addressed.

Broadly speaking I agree that drivers are professionals and can be trusted to get on with the job without molly-coddling, but incidents still happen.

O L Leigh

 

[BestWestern]

Train Protection and Warning System (TPWS) is actually a very simple system. The track equipment consists of two antenna (called loops) that, when live, transmit a radio signal to a received underneath the train....

O L Leigh

Thanks for that, I know what it does but was out on a bit of a limb when it comes to a technical explanation of how it functions!

 

[Grantham]

Train Protection and Warning System (TPWS) is actually a very simple system. The track equipment consists of two antenna (called loops) that, when live, transmit a radio signal to a receiver underneath the train. The first antenna is called the "arming loop" which starts a timer on the train. The second antenna is called the "trigger loop". If the train passes over the trigger loop before the timer has run down it will automatically trigger an emergency brake application.

There are two applications for TPWS, called "train stop loops" and "overspeed loops". Train stop loops are used at signals where the arming and trigger loops are placed immediately one after the other and will be energised whenever the signal is held at danger. This will stop any train that passes the signal without authority.

Overspeed loops are the ones that are most pertinent to the Waterfall crash. Sometimes these overspeed loops will be used in conjunction with train stop loops where there is a danger that a train that has passed a signal at danger without authority will not be stopped within the overlap of the signal. Therefore an emergency brake application can be triggered on a train BEFORE it reaches the signal itself if the driver fails to reduce the speed of the train on approach. However, overspeed loops are also found on approach to some speed restrictions where the reduction in speed is significant.

To drag this discussion back on-topic, TPWS may not have prevented the Waterfall crash but it WOULD have prevented the Chatsworth crash. A signal protecting a single line section is a prime location for fitment of TPWS. Even if the engineer had been busy texting his mates and not been paying attention to the road ahead, TPWS would have stopped the train before it fouled the single line. That the US Railroad authorities have no equivalent system is something that I think will need to be addressed.

Broadly speaking I agree that drivers are professionals and can be trusted to get on with the job without molly-coddling, but incidents still happen.

O L Leigh

Sounds like any protection would have helped, trip cock to dump the air would do the job too.

M

 

[A-driver]

I believe TPWS always arms for 1 sec-ie when passing the arm loop it arms the trigger for 1 sec. If you pass the trigger within that time then it will trip you. That's why grids vary in distance-one set at 50-60mph for a PSR will be far further apart than those leading to buffers set at 10mph. Quite simple really-I believe tripcocks on the tube and finsbury park-moorgate line work exactly the same way.

 

[TDK]

I know guards that sit in the back cab detailing every time a driver exceeds the speed limit and reports them to management

As for TPWS taking things out of a drivers control - do you know what a reset and continue event is Bestwestern?

That cannot be used as evidence as the speedo in the back cab in reverse will not necessarily match the front speedo - if a guard reports a driver for speeding the only way to prove this is download the train via OTMR, then check the speedo and the wheel diameters then and only then can the driver be approached regarding a speeding incident.
--- old post above --- --- new post below ---

I would take said Guards to one side and have words, what's that all about?! Jeez, who cares if it's a few miles over, and besides it's hardly unheard of to have a speedo discrepancy between different cabs!? :roll: Having said that, to use the Aussie example quoted above, if it was nearly a ton over the limit I may feel compelled to buzz my Driver up and ensure he isn't dead or suicidal!

Reset and continue is a very bad thing is it not?; I'd imagine bottoms being very firmly smacked if that was found out to be a regular occurrence!

All PSR's ahve a tollerance so say a 50mph PSR can accept a train at 60mph with no adverse consequences apart from a rough ride, the tollerance for speeding for a driver is 3mph tolerance, over 3mph and you are speeding, this is due to speedometer accuracy etc. As for speedo discrepencies these are very common and there are not many trains - units anyway that are exactly the same from front to rear cab - reset and continue is a very serious flail of the rules and any driver that resets and continues can expect to be dosciplined severely, by resetting and continuing without the permission of the signaller is actually disregarding the safety systems provided.