ATO

[xtmw]

ATO 

The Central Line ATO, is it actually that good? (It was commissioned in the early 00's?) with a lot of overruns, and underruns (which still happen today) but I haven't encountered either of these in a long time. What are the flaws of the ATO system, and for a little project I'm working on, what does the DTS say sometimes? (If anyone is allowed to actually say, which I'm pretty sure they are allowed to say, but correct me if I am wrong) I have a few such as ATP Code Loss, Station Skip, ATO ready, ATP ready, Zero MSS? Any others I'm missing?


Anything else that the ATO system sometimes does? I've had a few instances where the train sometimes comes to a magical halt, with a lot of huffing and squealing noises? 

Thank you everyone

[Dstock7080]

Jun 13, 2022 19:06:52 GMT xtmw said:

and for a little project I'm working on, what does the DTS say sometimes? (If anyone is allowed to actually say, which I'm pretty sure they are allowed to say, but correct me if I am wrong) I have a few such as ATP Code Loss, Station Skip, ATO ready, ATP ready, Zero MSS? Any others I'm missing?

ATP NOT OK CAR 1
ATO NOT READY
ATO START FAULT
ATO BRAKE APPLIED
ATO DOOR WARNING
ATO EMERGENCY BRAKE
ATO OVERSPEED
ATP EM. BRAKE ON
ATP CODES AVAILABLE
ATO REBOOT OK
AUX SET REQ
EMERGENCY BRAKE
NEXT BRAKE EMERGENCY
LOCAL BRAKE FAULT
ROUND TRAIN FAULT
BRAKE DECODER FAULT CAR ‘X'
PEA BRAKE
PASS ALARM CAR ‘X'
PWM FAULT CAR ‘X'
M/B CONFLICT CAR ‘X'
DRAGGING BRAKE
MAIN LINE AIR FAULT
SUSPENSION FAULT
TRACTION FAULT
Equipment fault

[bpk]

Jun 13, 2022 19:06:52 GMT xtmw said:

ATO 

The Central Line ATO, is it actually that good? (It was commissioned in the early 00's?) with a lot of overruns, and underruns (which still happen today) but I haven't encountered either of these in a long time. What are the flaws of the ATO system, and for a little project I'm working on, what does the DTS say sometimes? (If anyone is allowed to actually say, which I'm pretty sure they are allowed to say, but correct me if I am wrong) I have a few such as ATP Code Loss, Station Skip, ATO ready, ATP ready, Zero MSS? Any others I'm missing?


Anything else that the ATO system sometimes does? I've had a few instances where the train sometimes comes to a magical halt, with a lot of huffing and squealing noises? 

Thank you everyone

To answer your initial question as a driver, I think its a very good system overall. While it is a fixed block system that works in a station to station nature, the proximity between trains is not far off what you’d get with TBTC for comparison.

To some extent it still works to the same principles as conventional signalling for example categories of signal, shunt signals etc. This means the Rules and Procedures training is not totally alien to someone coming in as a new driver from Ashfield House (you have to learn conventional signalling first regardless of what line your going to) or transferring from another line.

There is also more scope to operate under degraded conditions without impacting the service too much and Coded Manual mode is far more user friendly than what I’ve seen of Protected Manual mode in TBTC.

Without looking at a spreadsheet of reliability I’d say its reliable, the most common issues in my experience are temperamental train bourne issues that require a “trip and reset” of the ATP.

Huffing and puffing trains coming up in a heap is 99.9% of the time down to low rail adhesion, and the sound is the Wheel Slide Protection system kicking in.

www.davros.org/rail/signalling/articles/central.html
This site gives a good overview of the system with all the relevant dates.

[xtmw]

Thanks both - that website looks interesting.

[jamesb]

My experience of travelling on the central line as a passenger over the years is that the ATO doesn't perform very well in wet weather, with the trains stopping short or stopping between stations in the open sections (I recall somebody telling me once that it was related to the number of wheel turns not matching what the train would expect for a given distance travelled, causing the train to stop). It doesn't make a huge difference to the time it takes to complete my journey, but given rain is not uncommon, it seems a bit of design limitation (and coming to a sudden halt in wet, low adhesion conditions can't be good for the wheels!).

One particular highlight is that it seems to be 'sensible' in its design, allowing trains to get quite close to one another (for example, the closest I have ever seen two moving trains allowed to get is at Woodford, when a Hainault train is crossing over onto the eastbound platform from the siding [? the siding is called 21 road] and at the same time a westbound train is entering the westbound platform - at a cautious speed. I suspect on a more modern ATO system the westbound train would be held outside the platform until the Hainault train had crossed over onto the eastbound.

Another highlight from my perspective is that the LED next train indicator boards always seem accurate, and often give more accurate information then platform staff especially at times of disruption when there are last minutes changes. I also like the ability of the boards to display 'held' next to the destination although I'm not sure what triggers this.

[class411]

Jun 14, 2022 8:25:19 GMT jamesb said:

My experience of travelling on the central line as a passenger over the years is that the ATO doesn't perform very well in wet weather, with the trains stopping short or stopping between stations in the open sections (I recall somebody telling me once that it was related to the number of wheel turns not matching what the train would expect for a given distance travelled, causing the train to stop). It doesn't make a huge difference to the time it takes to complete my journey, but given rain is not uncommon, it seems a bit of design limitation (and coming to a sudden halt in wet, low adhesion conditions can't be good for the wheels!).

One particular highlight is that it seems to be 'sensible' in its design, allowing trains to get quite close to one another (for example, the closest I have ever seen two moving trains allowed to get is at Woodford, when a Hainault train is crossing over onto the eastbound platform from the siding [? the siding is called 21 road] and at the same time a westbound train is entering the westbound platform - at a cautious speed. I suspect on a more modern ATO system the westbound train would be held outside the platform until the Hainault train had crossed over onto the eastbound.

Another highlight from my perspective is that the LED next train indicator boards always seem accurate, and often give more accurate information then platform staff especially at times of disruption when there are last minutes changes. I also like the ability of the boards to display 'held' next to the destination although I'm not sure what triggers this.

'Held' is probably one of those things that someone at LU though was a good idea, and people who work for LU probably understand, but is b*gger all use to passengers.

I've been using LU for decades, and reading these forums for many years, but I've absolutely no idea what 'Held' means in the context of a train describer.

Obviously it means that the train is not moving, but what else?

The only thing that I can think of that makes any sense is that a train is stopped at some point where other trains can and are passing it. But is that of any help or interest to passengers?

[Chris M]

"Held" means that the train is currently not moving, often for longer than usual. It is expected that it will continue its journey, but the signalling system doesn't know how long the wait will be. The most common reasons are either because it's waiting at a red signal (or equivalent) or the driver has been instructed to wait in the platform so the train isn't stationary between stations for an extended period.
Or, alternatively

[jamesb]

I wondered if it triggers automatically if the minutes don't decrease as expected for whatever reason, e.g. the train is stationary when the signal says it can proceed?

Eventually the next train indicator board will display 'the service is delayed at present'.

I find it reassuring, ironically, because it at least means the signalling system is working consistently, and the delay is normally in the order of minutes!

Jun 14, 2022 8:48:29 GMT class411 said:

Jun 14, 2022 8:25:19 GMT jamesb said:

My experience of travelling on the central line as a passenger over the years is that the ATO doesn't perform very well in wet weather, with the trains stopping short or stopping between stations in the open sections (I recall somebody telling me once that it was related to the number of wheel turns not matching what the train would expect for a given distance travelled, causing the train to stop). It doesn't make a huge difference to the time it takes to complete my journey, but given rain is not uncommon, it seems a bit of design limitation (and coming to a sudden halt in wet, low adhesion conditions can't be good for the wheels!).

One particular highlight is that it seems to be 'sensible' in its design, allowing trains to get quite close to one another (for example, the closest I have ever seen two moving trains allowed to get is at Woodford, when a Hainault train is crossing over onto the eastbound platform from the siding [? the siding is called 21 road] and at the same time a westbound train is entering the westbound platform - at a cautious speed. I suspect on a more modern ATO system the westbound train would be held outside the platform until the Hainault train had crossed over onto the eastbound.

Another highlight from my perspective is that the LED next train indicator boards always seem accurate, and often give more accurate information then platform staff especially at times of disruption when there are last minutes changes. I also like the ability of the boards to display 'held' next to the destination although I'm not sure what triggers this.

'Held' is probably one of those things that someone at LU though was a good idea, and people who work for LU probably understand, but is b*gger all use to passengers.

I've been using LU for decades, and reading these forums for many years, but I've absolutely no idea what 'Held' means in the context of a train describer.

Obviously it means that the train is not moving, but what else?

The only thing that I can think of that makes any sense is that a train is stopped at some point where other trains can and are passing it. But is that of any help or interest to passengers?

[Tom]

The control centre can hold a train in the platform via the ATO system - this comes up as 'Held' on the Train Operator's desk. It may well (I've never read into it that much) also cause the Dot Matrix Indicators to show held.

I tend to agree with class411 that 'held' doesn't really make much sense to someone watching the Dot Matrix several stations down the line. Maybe 'delayed' would be a better term.

[xtmw]

I'm a frequent user of the Central Line eastern branch - and at Loughton the train indicator can't decide if the next train is in 7 or 8 minutes, so it flips between the two and then eventually switches to 'Held'

A lot of drivers switch to CM when it's raining, I notice when it is raining, the train stops as I said before with a lot of huffing and squealing noises (as i said before), the train is then clearly placed into CM because of the acceleration being slightly degraded and the braking not being as perfect as ATO! Although there are the odd few drivers who can actually stop like ATO

[bpk]

Driving CM in low rail adhesion requires lighter, earlier braking in order let the Wheel Slide Protection work effectively. ATO can get it right sometimes, and I know Wood Lane SCC can implement a lower braking rate on the open sections as they do in the leaf fall season.

Yes some drivers can stop "like the ATO", on dry rails you can even approach open stations slightly faster than the 50kph ATO hits the tailwall at. I believe the ATO brake rate allows for slightly faster approaches than is possible in CM in tunnels however. At Gants Hill IR for example you can stop comfortably in CM if you hit the tailwall at 58-possibly 60kph but you certainly wouldn't want to be doing anymore than that. ATO can do it at 65kph and its certainly not worth trying replicate that!


Another drawback with ATO is if the train underruns at a station where the Starting Signal is red, the Target Speed for the next signaling section is obviously zero and there is a limited time in which you have to switch to Coded Manual and pull up to the signal/fully berth train into the platform before being "code tripped". In this instance, it's safer/more practical to wait for the starter signal to clear or radio the signaller for authority to fully berth the train, preferably in CM but it may be necessary to do this in Restricted Manual if the signaller gives you authority to do so.

[d7666]

This is 'held' :

www.flickr.com/photos/58218988@N07/52145205797/in/dateposted-public/

[spsmiler]

Jun 14, 2022 9:01:29 GMT Chris M said:

"Held" means that the train is currently not moving, often for longer than usual. It is expected that it will continue its journey, but the signalling system doesn't know how long the wait will be. The most common reasons are either because it's waiting at a red signal (or equivalent) or the driver has been instructed to wait in the platform so the train isn't stationary between stations for an extended period.
Or, alternatively

Fantastic image!! That said, I wonder whether Joe Public will appreciate someone lovingly caressing the train they are actually on. 

[xtmw]

Is it possible to SPAD on CM? I'm aware the Target Speed becomes 0 when approaching a red signal or when a block section is occupied.

[Dstock7080]

Jun 15, 2022 8:20:55 GMT xtmw said:

Is it possible to SPAD on CM? I'm aware the Target Speed becomes 0 when approaching a red signal or when a block section is occupied.

It is certainly possible to in CM.

[Tom]

Jun 14, 2022 12:47:51 GMT bpk said:

Another drawback with ATO is if the train underruns at a station where the Starting Signal is red, the Target Speed for the next signaling section is obviously zero and there is a limited time in which you have to switch to Coded Manual and pull up to the signal/fully berth train into the platform before being "code tripped". In this instance, it's safer/more practical to wait for the starter signal to clear or radio the signaller for authority to fully berth the train, preferably in CM but it may be necessary to do this in Restricted Manual if the signaller gives you authority to do so.

It depends on the location, but you should be able to pull up to a red aspect without being code tripped. In auto areas it's not a problem, but in controlled areas the code can be removed from under a train when it's been proved at rest for a set period of time - either because the signalling system has called for an overlap when the train runs in, and now it's at rest it doesn't need to lock that overlap (allowing for a shunt move to a siding, for instance), or the turnaround berth code timer has run. This takes the code off the front of the train ready for it to be applied to the other end if the train reverses.

From memory the overlaps time out after fifteen seconds and turnaround timers after 30 or 60.

When it comes to rain, the worst type is not heavy rain but a light, misty rainfall - despite many years of trying various fixes the ATO still struggles with light rain, when it starts to brake, has a bit of wheelslip or slides, loses where it is and pulls up in a heap as others have described.

[100andthirty]

Jun 15, 2022 12:00:49 GMT Tom said:

Jun 14, 2022 12:47:51 GMT bpk said:

Another drawback with ATO is if the train underruns at a station where the Starting Signal is red, the Target Speed for the next signaling section is obviously zero and there is a limited time in which you have to switch to Coded Manual and pull up to the signal/fully berth train into the platform before being "code tripped". In this instance, it's safer/more practical to wait for the starter signal to clear or radio the signaller for authority to fully berth the train, preferably in CM but it may be necessary to do this in Restricted Manual if the signaller gives you authority to do so.

It depends on the location, but you should be able to pull up to a red aspect without being code tripped. In auto areas it's not a problem, but in controlled areas the code can be removed from under a train when it's been proved at rest for a set period of time - either because the signalling system has called for an overlap when the train runs in, and now it's at rest it doesn't need to lock that overlap (allowing for a shunt move to a siding, for instance), or the turnaround berth code timer has run. This takes the code off the front of the train ready for it to be applied to the other end if the train reverses.

From memory the overlaps time out after fifteen seconds and turnaround timers after 30 or 60.

When it comes to rain, the worst type is not heavy rain but a light, misty rainfall - despite many years of trying various fixes the ATO still struggles with light rain, when it starts to brake, has a bit of wheelslip or slides, loses where it is and pulls up in a heap as others have described.

Regarding rain, What Tom has described is an issue for all ATO systems. The SELTRAC systems can select lower braking rates (and, on SSR, motoring rates) to try and minimise wheel slip or spin. Research continues on having reliable/safety rated speed/position determination that doesn't rely on wheel rotation. Some use Doppler radar, others use accelerometers but this is in addition to the tachometers, not instead of.

There's probably a debate to be had at system level about how much wheelspin/disagreement between tachos is allowed before trains come up in a heap! The ATP system designers tend, reasonably, to be rather conservative.

[class411]

People keep talking about a train ‘in a heap’.

What does this mean?

I’ve never seen a train in anything other than a linear configuration.

[bigvern]

Up in a heap, the meaning in this that the train has lost code or has been tripped and the emergency brakes are applied, so the train does stop quite abruptly and due to the drawgear may be some buffing between cars, this term is used commonly on the underground.

[towerman]

Used to get bad wheelslide on 60TS with the old system,esp from full speed to controlled speed approaching Chigwelll OR.

[towerman]

I’ve been out of the loop on LUL for the past 12 years.Is the Vic Line system an upgraded version of the Central Line system?

[jimbo]

Jun 15, 2022 12:00:49 GMT Tom said:

When it comes to rain, the worst type is not heavy rain but a light, misty rainfall ...

Good job that is not common then!!! :-) 

[Colin]

Jun 15, 2022 21:26:24 GMT towerman said:

I’ve been out of the loop on LUL for the past 12 years.Is the Vic Line system an upgraded version of the Central Line system?

No, the Victoria line uses a distance to go radio based system these days.

There was a thread discussing it recently but having done a very brief search I haven't found it....

[Tom]

Jun 15, 2022 21:26:24 GMT towerman said:

I’ve been out of the loop on LUL for the past 12 years.Is the Vic Line system an upgraded version of the Central Line system?

I'm not entirely sure. The vital signalling is based on the Central line hardware and the application logic is similar, but the ATP and ATO side of things is a bit different. The 'map' of the railway is carried on the train on the Victoria line, whereas on the Central the map data was uploaded at each station. The ATP works on radio comms as Colin says, rather than via the track circuits which are purely for detection purposes.

How the ATO data is constructed, I'm not entirely sure.

[t697]

I thought the key point where Central and Vic ATP differ is that on the Vic "Distance to go" means it's continuously calculated whether the train is following a safe brake profile towards the 'signal' or speed restriction and trip it if not, even before it gets there. Hence the overlap can be shorter and trains can run safely on closer headways. And that's why Vic can achieve 36tph and the Central line system can't be made to do that.

[Tom]

Yes, you're right - there aren't the multitude of Overlap charts like on the Central line.

[xtmw]

Yes - One thing I've noticed with the Central Line ATO is that even if a train is 1 or 2 minutes behind, the train slows down in the tunnel and sometimes stops. Not so much in the open though