It was installed in 1994 after Mr. Rogers, misreading the signal by the fish tank, operated the trolley at too high of a speed around the castle, leading to a derailment that sent the trolley off the bridge. The investigation found a casual factor was the pianist was fatigued after filming three episodes in a row and had played the trolley music too slowly. Prince Tuesday was killed in the accident, but the show quietly replaced him with another actor.
Advantage is that PTC is going to be with modern ETCS like technology with GPS and radio communications, none of this 1990s stuff with miles of cable, fragile track antennas, and complex logic about release speeds, that the UK got stuck fiddling with.
@@SportyMabamba Finished. All Class I mainlines, and inter-city and commuter passenger lines had PTC operational as of the end of 2020. 98.5% was running at the end of 2019. In fact, the US has 5.8x the route-km under PTC than the UK has rail.
I worked on the railway here in Britain for nearly 45 years . And we used to get a lot of these sorts of films . We didn't mind . We got paid for doing nothing ! :-) Drivers may well have seen this as a introduction, but they would have gone into far more detail in the class room .
Greyclaw A lot of drivers for Thames and chiltern watched these ! One about low adhesion on here and the Slough incident the driver involved watched it and chuckled with embarrassment !!
Questions: 1. Who supplied which system at the time on either GWML and CML. 2. Who supplies them now and are they exactly the same system? 3. How does this fit in with the ERTMS standards?
TheSaintST1 GEC signalling on behalf of Alcatel SEL and all the 165s were delivered. The chiltern system differs from the Great Western version slightly. But both work the same. ETCS or the full ERTMS is completely different. Originally the LUL section was going to get the system too but it was expensive and it eventually became impossible to engage in engineering possessions on LUL metals for this task. That’s why chiltern units have tripcocks. 1909 technology on 1990s trains at the time ! The equipment was manufactured for the LUL a section but was moved elsewhere where it was more important. Sure would have helped. Thames pinched units 001-008 and gave them back eventually to 2004 and they didn’t get tripcocks when they got back so had to run in a 4 car formation. The ATP buttons were smashed up and had to go to Ilford for replacement. There’s a pic I remember of 005 and 003 being coupled oddly because of the arrangement
Greyclaw I believe Alcatel still supply the equipment however the supply for it is low because it is considered obsolete now. Chiltern Main line will keep it GWML will eventually rid of it and replace it with ERTMS but unlikely soon because the whole line was resignalled and taken over at TVSC at Didcot and replaced boxes such as Slough PSB or New IECC. I believe the building still exists.
The original plan was to use two independent manufacturers for the two systems - one for the Chilterns and the other for the Western main line and the new Heathrow Airport branch at the time. At that time, ACEC and Alcatel were separate companies, but not now. Historically, I had a fair bit to do with both signalling systems on both the Chilterns and the new Heathrow branch (along with full-on renewal and electrification between London Paddington and West Drayton). Might be worth mentioning that, at the time, not all rolling stock was fitted with it; in effect, just the new Heathrow Express ones, and the “Intercity” HSTs; not the rest of it, in particular the Network South East sets, nor any locomotives at the time. The integration of an add-on system to traditional BR signalling systems, along with conventional driving skills etc was hard work - including psychology as well; not just physical installation of extra equipment. All had much to learn along with that. As usual, money talks, and slowed down the original project, assisted by privatisation. It led to the development of the “Train Protections and Warning System (TPWS)” under Railtrack (remember them?). Later on, the concept of European Train Control System (ETCS) evolved, and in effect it has taken over the market.
@EdgyNumber1 Both GWML and Chiltern had given by different suppliers. The GWML is using the TBL signal.which develop by ACEC Belgium (Later on as GEC-Alsthom/Now Asltom.) This system also being use in our Hong Kong East Rail Line (1996-2021) when KCRC upgrading the whole signa from AWS as it didn't prevent SPAD crash.(But AWS still kept at secondary signal for Intercity train and cross country train. Now replace by Siemens TrainGuard-MT CBTC. Chiltern Mainline is using SELCab which provide by SEL Germany(Alcatel-SEL now part of the French Thales Group.) It is now as Seltrac system. SELCab is diverted from Seltrac system. Seltrac also being used in Hong Kong West Rail Line since 2003. It is the first use as Mainline signal in the world.)
is the warbler different on the chiltern system than on the gwml? i thought the cab/driver interfaces were identical on both systems. you can hear the chiltern one at 1.20 and the gwml/ hst one if you seach on here for 'emergency stop at 125mph'
While the installation of loop cables in Hong Kong is much rigorous than that..... Not a cable tie and a simple clip, but a tailor-made fixture, bolted onto the sleeper, for securely holding the cable.
Adenosine triphosphate Adenosine triphosphate is a complex organic chemical that provides energy to drive many processes in living cells, e.g. muscle contraction, nerve impulse propagation, and chemical synthesis.
Interesting video. Probably from the 80ties or earling 90ties by the look of the glasses... :) Why wasn't the system rolled out over the entire network eventually? Simply because of too high costs? The wire loop system is similar to the LZB cabsignalling system in Germany for the ICE high speed trains. It was develloped back in the 80ties. This system is still in use. It might be replace by ETCS level 2 in the near future.
If some unforeseen incident occurs can the driver over-ride the system? For example a motor car or lorry coming off an over bridge. As recently happened.(2 or 3 years ago)
The driver is in full control unless he/she is speeding or is not following instructions to brake because of restrictions the system knows about. This means that the driver can always stop the train themselves for other reasons. They cannot go faster than permitted by the system.
So what is the difference between AWS that the gwr had for many years to today's systems so if the driver cancels the audible warning and then commits a SPAD how does this system eliminate that
The cleaning is done by a massive mechanised unit, either using suction or mechanical means to remove, clean and replace the ballast as it slowly travels over it. The APT equipment would get damaged in the process.
Sean Not-telling Yes, ATP would have prevented the accident in WA. I operate Light Rail that utilizes ATP. I have no doubts that by not installing ATP on the renovated rail and saving $900,000, it just cost 3 or more lives, and numerous serious injuries.
It's going to be a bit of a wait for the NTSB and the speculations are flying right now. Everything from something on the tracks to speeding in that 30 MPH curve. All I can really say and hope for is that the numbers of fatalities don't increase over the next few days. I happened to be on that section of the interstate this last Friday. Spooky what can happen and where it can come from when you time is up.
Sean Not-telling its my understanding they weren't using track equipped with atp. However that's interesting that they didn't provide cautions along that route :(
I just noticed that I posed the almost exact same question 5 years ago. I had forgotten that I had already seen this video. But hey, youtube keeps coming up with these videos, although it should know that I have already seen it.... Thanks all for answering (again)!
ATP continually monitors your speed and can provide you with information (permitted speeds and signal aspects here for example) whereas TPWS doesn't really warn you before it intervenes and can only act on trains in fixed locations (e.g. signals). ATP will also do its best to stop you from passing a red signal (or end of movement authority) whereas TPWS overspeed sensors won't necessarily stop you before the signal, rather it aims to stop you before a point of conflict. Depending on your definition you could include (amongst others) TVM, ETCS and CBTC in "automatic train protection" as they also continually monitor your speed, I'll leave that for someone else though!
Bahn: That's fourth-rail track, which uses two rails for D.C.: One rail is DC-, and the other is DC+. Search for London Underground videos, and you'll see it there!
And in fact some of the Chiltern stock currently shares some of the London Underground routes in the area, and in the past used the same physical SPAD (Signal Passed At Danger) protection system, called the 'tripcock.'
Sorry, but that is not 4th rail. It is just normal rail sitting loose. I can't quite tell if it is new track awaiting installation or just old track waiting to be taken away but it is not LUL 4th rail.
EdgyNumber1 anything running over shared track with LU still requires tripcock protection. Chiltern into Marylebone and whichever TOC runs into Wimbledon also. Tripcocks are only removed as lines get upgraded to automatic signalling (DTG, TBTC & CBTC solutions have been or are being installed).
Thank you, children. Just a guy doing a favour for a friend. So glad it gave you something to try to sound 'big' about. I'm sure you could all do better. Er, funny how nobody asked you? It's so easy to make these unpleasant comments hiding behind a keyboard. I'm sure you'd foul yourselves if you were standing in front of me and had to make these comments. .
I have never heard it called ATP, BNSF, Amtrak, and the U.P. call it PTC for positive train control. All the press I saw coming out of Washington State this week called it PTC.
Bagaimanupun juga itu adalah konstruksi yang labil Orang bodoh yang banyak menghabiskan biaya/banyak untuk teknologi alat berat, bahan yang digunakan,ongkos upah pekerja,menghabiskan banyak waktu dalam proses pengerjaan dan hasilnya sangat tidak memuaskan SOEDIRAN, SETYAWAN TULUS RAHARJO MON'CHOYS STATION BLORA CENTRAL JAVA INDONESIA.
Unnecessary system to be honest. TPWS and TPWS+ do the same job for a lot less cost. ERTMS will be rolled out soon. Stuart how do you mean over-ride the system? go faster or slower?
Sorry David, disagree. TPWS can't prevent a train above a certain speed from going over the overlap. ATP won't let the train go that fast to begin with and will stop the train. ERTMS will render it (and TPWS) obsolete though
We have TPWS+ for the higher speeds. There's not been train crashes as a result of the current TPWS system failing to stop trains within the overlap. (Yes there have been trains with defective brakes such as at Crewe where speeding was involved and the driver had no proven route knowledge or low adhesion incidents which the system wouldn't stop anyway. ERTMS is the answer but in the meantime ATP is in its present form horribly inefficient. For example it can't tell the train if the aspect changes to a less restrictive one until the train gets to the balise near the signal. It is an intermittent form of train supervision. What this means is if a signal changes from red to green is that the driver can't accelerate under ATP until the signal is reached despite the fact he/she can see the signal hundreds of yards away.
+David S Extra layers of safety is NEVER "Unnecessary". What happens is one system failed and the train's computer fails to detect that failure due to some software or hardware bug? Computers and electronics can and do go wrong. The class 220/221 Voyager (plastic snot-box) is a perfect example.
+Morgan Winters as I said TPWS is adequate protection until ERTMS is rolled out and let's not forget ultimately the train driver 'drives' the train not the computer.
+David S Relying on one system alone is never a good idea regardless of how good anyone thinks is it. For example, think of the number of safety devices something like a TV in your home has (Main 80-100 amp fuse at the meter, an RCD, a MCB, plug fuse and often and internal fuse or thermal cut-out device). A train having multiple safety systems is never a bad idea. ERTMS however isn't fully rolled out yet is still under testing and development and it will be under testing a few years after it is fully rolled out to ensure the system works as designed in real world conditions. Even after real world testing, ERTMS won't be the ONLY safety device fitted to trains. If there is a human controlling the train, there will be other safety systems in place like the dead mans pedal. Technically drivers of modern stock don't "Drive" the train. They simply make requests to the on board computer which then decides based on different sensor information weather that request can be acted upon or not, just like a modern fighter jet like the Eurofighter. Modern trains like the Voyagers have no physical connection (push/pull rods, moving steel cable ect) between the power lever and the engine/traction motors. Only electrical cable which goes via a computer, that's what drive-my-wire is. Hence why on a 100mph line, a train can't go 125mph, The computer will say no (excuse the pun). The Eurofighter for example, is designed to be aerodynamically unstable and requires thousands of tiny adjustment every second to keep it in level flight, something that's impossible for a human to do since humans can only make low tens of adjustments per second. If one took the flight computers out and replace them with cable and pulleys. It would be very hard to fly and would be far too demanding on the pilot.
Brian Butterfield once again presenting railway safety films to us!
Jesus.....i'm at this part of the internet again.....
Hahaha.. Oh f**k yes.... I hear you brother...
Ian Hawkins I *love* this part of the internet. SO fascinating.
You can never leave!
🤣
I developed ATP some years ago. I appreciate this.
Lol
It was installed in 1994 after Mr. Rogers, misreading the signal by the fish tank, operated the trolley at too high of a speed around the castle, leading to a derailment that sent the trolley off the bridge. The investigation found a casual factor was the pianist was fatigued after filming three episodes in a row and had played the trolley music too slowly. Prince Tuesday was killed in the accident, but the show quietly replaced him with another actor.
After watching the video, I just can't Live Without ATP, i am dreaming day and night about it.
"Living with ATP" ..... I thought it was debilitating disease people had.
lmao too I'm thinking it's an autoimmune disorder...
Adenisine triphosphate
Association of Transport Professionals
Approved Training Personnel
These nearly write themselves.
that guys voice is so smooth
I'm about to work on the tracks so am going on a train video binge
This is handy information if I go into the train business some day.
Another great video 👍
Gotta love CZcams related videos :) Quite interesting tho!
I recognise the narrator. I bought a red Citroen cx off him in 1990 in Tonbridge wells. Spa films. He did a video of it. C560 MVW. Small world.
Living with ATP in the US is easy. We just talk about it, we don't actually do it.
ATP is a safety system used in British railways and is a result of the Southall and Ladbrokes grove crashes
Advantage is that PTC is going to be with modern ETCS like technology with GPS and radio communications, none of this 1990s stuff with miles of cable, fragile track antennas, and complex logic about release speeds, that the UK got stuck fiddling with.
straightpipediesel how’s that PTC roll-out going? 🤣
@@SportyMabamba well, at the moment, a lot of the North East has it with plans to expand it, so, ok
@@SportyMabamba Finished. All Class I mainlines, and inter-city and commuter passenger lines had PTC operational as of the end of 2020. 98.5% was running at the end of 2019. In fact, the US has 5.8x the route-km under PTC than the UK has rail.
Why does the Intercity swallow hst look so beautiful?
Makes ATP sound like an acronym for some kind of STD.
You can catch it by sleeping with an S&T technician.
ssbohio: Should have used protection, especially- never mind
I bet a lot of train drivers had to sit though this to watch why training
I worked on the railway here in Britain for nearly 45 years . And we used to get a lot of these sorts of films . We didn't mind . We got paid for doing nothing ! :-) Drivers may well have seen this as a introduction, but they would have gone into far more detail in the class room .
Is suspect this was for PWay staff instead of drivers
Greyclaw A lot of drivers for Thames and chiltern watched these ! One about low adhesion on here and the Slough incident the driver involved watched it and chuckled with embarrassment !!
@@danners4302 You're right, this one was for PWay workers, there was a separate driver version: czcams.com/video/Q4aWIjbVpcg/video.html
Paul looks different today.
Questions:
1. Who supplied which system at the time on either GWML and CML.
2. Who supplies them now and are they exactly the same system?
3. How does this fit in with the ERTMS standards?
TheSaintST1 GEC signalling on behalf of Alcatel SEL and all the 165s were delivered. The chiltern system differs from the Great Western version slightly. But both work the same. ETCS or the full ERTMS is completely different. Originally the LUL section was going to get the system too but it was expensive and it eventually became impossible to engage in engineering possessions on LUL metals for this task. That’s why chiltern units have tripcocks. 1909 technology on 1990s trains at the time ! The equipment was manufactured for the LUL a section but was moved elsewhere where it was more important. Sure would have helped. Thames pinched units 001-008 and gave them back eventually to 2004 and they didn’t get tripcocks when they got back so had to run in a 4 car formation. The ATP buttons were smashed up and had to go to Ilford for replacement. There’s a pic I remember of 005 and 003 being coupled oddly because of the arrangement
Greyclaw I believe Alcatel still supply the equipment however the supply for it is low because it is considered obsolete now. Chiltern Main line will keep it GWML will eventually rid of it and replace it with ERTMS but unlikely soon because the whole line was resignalled and taken over at TVSC at Didcot and replaced boxes such as Slough PSB or New IECC. I believe the building still exists.
The original plan was to use two independent manufacturers for the two systems - one for the Chilterns and the other for the Western main line and the new Heathrow Airport branch at the time. At that time, ACEC and Alcatel were separate companies, but not now.
Historically, I had a fair bit to do with both signalling systems on both the Chilterns and the new Heathrow branch (along with full-on renewal and electrification between London Paddington and West Drayton). Might be worth mentioning that, at the time, not all rolling stock was fitted with it; in effect, just the new Heathrow Express ones, and the “Intercity” HSTs; not the rest of it, in particular the Network South East sets, nor any locomotives at the time.
The integration of an add-on system to traditional BR signalling systems, along with conventional driving skills etc was hard work - including psychology as well; not just physical installation of extra equipment. All had much to learn along with that.
As usual, money talks, and slowed down the original project, assisted by privatisation. It led to the development of the “Train Protections and Warning System (TPWS)” under Railtrack (remember them?).
Later on, the concept of European Train Control System (ETCS) evolved, and in effect it has taken over the market.
@@johnkeepin7527 And now we get the inferior TPWS+ to replace ATP. Still no full speed protection for Intercities.
@EdgyNumber1 Both GWML and Chiltern had given by different suppliers.
The GWML is using the TBL signal.which develop by ACEC Belgium (Later on as GEC-Alsthom/Now Asltom.)
This system also being use in our Hong Kong East Rail Line (1996-2021) when KCRC upgrading the whole signa from AWS as it didn't prevent SPAD crash.(But AWS still kept at secondary signal for Intercity train and cross country train.
Now replace by Siemens TrainGuard-MT CBTC.
Chiltern Mainline is using SELCab which provide by SEL Germany(Alcatel-SEL now part of the French Thales Group.)
It is now as Seltrac system.
SELCab is diverted from Seltrac system.
Seltrac also being used in Hong Kong West Rail Line since 2003. It is the first use as Mainline signal in the world.)
Good now I know what to feed my ATP
is the warbler different on the chiltern system than on the gwml? i thought the cab/driver interfaces were identical on both systems. you can hear the chiltern one at 1.20 and the gwml/ hst one if you seach on here for 'emergency stop at 125mph'
While the installation of loop cables in Hong Kong is much rigorous than that..... Not a cable tie and a simple clip, but a tailor-made fixture, bolted onto the sleeper, for securely holding the cable.
A good idea - until you need to remove it!
@@JulianShagworthy Why do I need to remove 🤓
Adenosine triphosphate
Adenosine triphosphate is a complex organic chemical that provides energy to drive many processes in living cells, e.g. muscle contraction, nerve impulse propagation, and chemical synthesis.
Fascinating
It is innit!
@@darrencafferty most definitely is
Interesting video. Probably from the 80ties or earling 90ties by the look of the glasses... :) Why wasn't the system rolled out over the entire network eventually? Simply because of too high costs? The wire loop system is similar to the LZB cabsignalling system in Germany for the ICE high speed trains. It was develloped back in the 80ties. This system is still in use. It might be replace by ETCS level 2 in the near future.
Indeed, it was due to costs that ATP was not fitted network wide. However, TPWS was fitted network wide since due to significantly lower costs.
It is due to the privatization and the British Government's policy of not put funding the railway to do their work...
@@AAA839 Ok thanks for your answer.
im not even a train worker
Can I have one? Please see Volume 3 #2, ATP and YOU
If some unforeseen incident occurs can the driver over-ride the system? For example a motor car or lorry coming off an over bridge. As recently happened.(2 or 3 years ago)
The driver is in full control unless he/she is speeding or is not following instructions to brake because of restrictions the system knows about. This means that the driver can always stop the train themselves for other reasons. They cannot go faster than permitted by the system.
So what is the difference between AWS that the gwr had for many years to today's systems so if the driver cancels the audible warning and then commits a SPAD how does this system eliminate that
Just out of curiosity why does the ATP equipment (beacons, cable loops) need to be removed during ballast cleaning?
The cleaning is done by a massive mechanised unit, either using suction or mechanical means to remove, clean and replace the ballast as it slowly travels over it. The APT equipment would get damaged in the process.
llama0wn3d makes sens
Could this of saved lives today in Washington State?
Sean Not-telling Yes, ATP would have prevented the accident in WA. I operate Light Rail that utilizes ATP. I have no doubts that by not installing ATP on the renovated rail and saving $900,000, it just cost 3 or more lives, and numerous serious injuries.
It's going to be a bit of a wait for the NTSB and the speculations are flying right now.
Everything from something on the tracks to speeding in that 30 MPH curve. All I can
really say and hope for is that the numbers of fatalities don't increase over the next few days.
I happened to be on that section of the interstate this last Friday. Spooky what can happen
and where it can come from when you time is up.
Sean Not-telling its my understanding they weren't using track equipped with atp. However that's interesting that they didn't provide cautions along that route :(
Does anyone know why ATP did not make it eventually? Only AWS en TPWS are in operation in the UK (and TVM on the London - Folkstone highspeed line).
It was between 3 and 4 times too expensive, per life saved, than the anyone was willing to cover.
Don't forget ERTMS. ATP, TPWS, and eventually lineside signaling will all be replaced by ERTMS.
@@GdotWdot Ok thank you!
I just noticed that I posed the almost exact same question 5 years ago. I had forgotten that I had already seen this video. But hey, youtube keeps coming up with these videos, although it should know that I have already seen it.... Thanks all for answering (again)!
17:00 I didn't know the GEML had ATP? Why not just use it then?
GWML. not GEML.
My ATP enjoys cucumber sandwiches and warm beer, that tends to keep my ATP happy, what about yours?
I find Owl Quiche is nice
Where is Paul I want Paul!
So who fired Paul?
I'm confused how this works with or is different from TPWS
ATP continually monitors your speed and can provide you with information (permitted speeds and signal aspects here for example) whereas TPWS doesn't really warn you before it intervenes and can only act on trains in fixed locations (e.g. signals). ATP will also do its best to stop you from passing a red signal (or end of movement authority) whereas TPWS overspeed sensors won't necessarily stop you before the signal, rather it aims to stop you before a point of conflict.
Depending on your definition you could include (amongst others) TVM, ETCS and CBTC in "automatic train protection" as they also continually monitor your speed, I'll leave that for someone else though!
Track Ciruits are not something that terrorist should know about, they can be false fed.
Duel Gauge track to the right @1:45 and @1:37??
Bahn: That's fourth-rail track, which uses two rails for D.C.: One rail is DC-, and the other is DC+. Search for London Underground videos, and you'll see it there!
And in fact some of the Chiltern stock currently shares some of the London Underground routes in the area, and in the past used the same physical SPAD (Signal Passed At Danger) protection system, called the 'tripcock.'
Sorry, but that is not 4th rail. It is just normal rail sitting loose. I can't quite tell if it is new track awaiting installation or just old track waiting to be taken away but it is not LUL 4th rail.
EdgyNumber1 anything running over shared track with LU still requires tripcock protection. Chiltern into Marylebone and whichever TOC runs into Wimbledon also. Tripcocks are only removed as lines get upgraded to automatic signalling (DTG, TBTC & CBTC solutions have been or are being installed).
Did someone take this to Dragons Den? If so I bet they got knocked back because the system is too fragile and unreliable.
_Railtrack didnt buy_
This seems simple compared to the US boondoggle known as PTC.
CZcams kicks the comment if you say Merry Christmas.
Really do they kick the comment if you say "MERRY CHRISTMAS"? Well there's a thing.
Oh ok it's now 23.27 Christmas eve . Marry Christmas every body ! :-)
Thank you, children. Just a guy doing a favour for a friend. So glad it gave you something to try to sound 'big' about. I'm sure you could all do better. Er, funny how nobody asked you? It's so easy to make these unpleasant comments hiding behind a keyboard. I'm sure you'd foul yourselves if you were standing in front of me and had to make these comments. .
It's harder, even, making them hiding under a keyboard. You should try it, man.
I have never heard it called ATP, BNSF, Amtrak, and the U.P. call it PTC for positive train control. All the press I saw coming out of Washington State this week called it PTC.
Same thing only different :-)
Ya think?
PTC is the American term.
Also, this is UK railway content. There are other continents outside of North America ;)
Bagaimanupun juga itu adalah konstruksi yang labil
Orang bodoh yang banyak menghabiskan biaya/banyak untuk teknologi alat berat, bahan yang digunakan,ongkos upah pekerja,menghabiskan banyak waktu dalam proses pengerjaan dan hasilnya sangat tidak memuaskan
SOEDIRAN, SETYAWAN TULUS RAHARJO
MON'CHOYS STATION BLORA CENTRAL JAVA INDONESIA.
maksudnya gimana nih? ATP teknologi penting lho
Unnecessary system to be honest. TPWS and TPWS+
do the same job for a lot less cost. ERTMS will be rolled out soon.
Stuart how do you mean over-ride the system? go faster or slower?
Sorry David, disagree. TPWS can't prevent a train above a certain speed from going over the overlap. ATP won't let the train go that fast to begin with and will stop the train. ERTMS will render it (and TPWS) obsolete though
We have TPWS+ for the higher speeds. There's not been train crashes as a result of the current TPWS system failing to stop trains within the overlap. (Yes there have been trains with defective brakes such as at Crewe where speeding was involved and the driver had no proven route knowledge or low adhesion incidents which the system wouldn't stop anyway. ERTMS is the answer but in the meantime ATP is in its present form horribly inefficient. For example it can't tell the train if the aspect changes to a less restrictive one until the train gets to the balise near the signal. It is an intermittent form of train supervision. What this means is if a signal changes from red to green is that the driver can't accelerate under ATP until the signal is reached despite the fact he/she can see the signal hundreds of yards away.
+David S Extra layers of safety is NEVER "Unnecessary". What happens is one system failed and the train's computer fails to detect that failure due to some software or hardware bug? Computers and electronics can and do go wrong. The class 220/221 Voyager (plastic snot-box) is a perfect example.
+Morgan Winters as I said TPWS is adequate protection until ERTMS is rolled out and let's not forget ultimately the train driver 'drives' the train not the computer.
+David S Relying on one system alone is never a good idea regardless of how good anyone thinks is it. For example, think of the number of safety devices something like a TV in your home has (Main 80-100 amp fuse at the meter, an RCD, a MCB, plug fuse and often and internal fuse or thermal cut-out device). A train having multiple safety systems is never a bad idea. ERTMS however isn't fully rolled out yet is still under testing and development and it will be under testing a few years after it is fully rolled out to ensure the system works as designed in real world conditions. Even after real world testing, ERTMS won't be the ONLY safety device fitted to trains. If there is a human controlling the train, there will be other safety systems in place like the dead mans pedal.
Technically drivers of modern stock don't "Drive" the train. They simply make requests to the on board computer which then decides based on different sensor information weather that request can be acted upon or not, just like a modern fighter jet like the Eurofighter. Modern trains like the Voyagers have no physical connection (push/pull rods, moving steel cable ect) between the power lever and the engine/traction motors. Only electrical cable which goes via a computer, that's what drive-my-wire is. Hence why on a 100mph line, a train can't go 125mph, The computer will say no (excuse the pun).
The Eurofighter for example, is designed to be aerodynamically unstable and requires thousands of tiny adjustment every second to keep it in level flight, something that's impossible for a human to do since humans can only make low tens of adjustments per second. If one took the flight computers out and replace them with cable and pulleys. It would be very hard to fly and would be far too demanding on the pilot.