Western Railroad Discussion > ATS (Automatic Train Stop) in a nutshell

In response to a query posted in a thread on the Passenger Board regarding Metrolink's new locomotives being equipped with ATS...

FRA guidlines dictate that without a Wayside Signal Actuation system, such as ATS (Automatic Train Stop) or ACS (Automatic Cab Signals) a train is not permitted to be operated above 79 MPH. With a wayside system spot-checking the engineer train speeds are permitted above 79 MPH though the overall permitted speed increase above 79 is limited by the effectiveness of the Wayside system. ATS is the simplest form of Wayside Signal Actuation that I know of, thus it only permits an increase of 11 MPH over 79, up to 90 MPH. ATS is most prevelant in the Southwestern US along several former ATSF lines where it was implemented in the 1930s-1950s. Since the Feds do not permit the removal of safety equipment ATS remains in effect on those lines today.

ATS (Automatic Train Stop), simply put, alerts an engineer when a decrease in speed is necessary... When in ATS territory (Between Milepost 176 and CP Pines on the Surfline for instance) you'll note small silver mounts right next to the signals on the engineer's side for the direction of travel. They're also placed next to most speedboards denoting a decrease in speed. These ATS inductors are magnetically set up so that when there is no power they are inert and thus when an ATS-equipped train passes its ATS shoe (mounted under the engineer's side, usually on the front truck) over the inert inductor it receives a magnetic signal which sets off an alarm in the cab. If the engineer fails to acknowledge the alarm by pressing a button or lever or whatever the cab's equipped with then after about 5-10 seconds the Pneumatic Control Switch opens; dropping the engine's load and applying a full set to the brakes, effectively forcing the train to stop.

The only time an ATS inductor will not send a signal is when the adjacent signal displays a clear indication, at which time the inductor is sent an electric charge inverting the magnetic field and making it invisible to the ATS shoe so it does not set of the AS alarm.

When an ATS-equipped train suffers a failure of the ATS system they are limited to 79 MPH (Or lower timetable speed) and must travel under an Absolute Block Authority, which means they treat EVERY signal as an absolute signal... this includes Intermediates. Furthermore the Absolute Block means they cannot enter a block without verbal permission from the dispatcher, who cannot give them permission unless the block is empty (even if it is governed by absolute signals, the ATS-deficient train cannot share a block with another train)

This is only meant to be a basic explanation... Feel free to add any information if you have it.

Also, I am not familiar with the operation of Automatic Cab Signals, if you are however you can post a thread of your own, I'd recommend posting it on the Eastern Board as it's more common over there.

Picture 1) The reason this whole discussion was started, for those wondering what we were talking about when we mentioned an ATS shoe in the Metrolink MP36 discussion here's a picture of an ATS Shoe attached to the forward truck of a Surfliner cab car, on the Engineer's side. I can't believe how many people have asked me in person if this has to do with third rail electric; Sorry folks, no 3rd rail on the Surfline!

Picture 2) Locals should be familiar with these small silver pods, which are placed next to signals and speedboards that DECREASE speed on the line. They activate the ATS system through the above shoe. And just to get it out of the way, yes that is a Nathan M5, no it's no longer mounted there, the K5LA was Bad Ordered and the M5 substituted for a few weeks (er, months). Don't bother booking your trip to the Surfline to see it, but you can see videos of the horn on YouTube. No questions about it.

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Nice explanation on ATS though!

IC had the same set up with cab signals, but had 2 loops nailed to the ties instead of silver Magnets on the side, and to bars with coils on them instead of shoes

Jaanfo has ATS nailed. It's 1930's technology, still in use today. We could do so much better if anybody wanted to spend some money. The railroads are all for safety when it involves painting a sign on a building, but when it would cost a little bit to make railroading safer that's a different story.

Barry Draper

barrydraper Wrote:
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> Jaanfo has ATS nailed. It's 1930's technology,
> still in use today. We could do so much better if
> anybody wanted to spend some money. The railroads
> are all for safety when it involves painting a
> sign on a building, but when it would cost a
> little bit to make railroading safer that's a
> different story.
>
> Barry Draper


It's not just some money it's a lot of money. Either most locomotives are fitted or you lose a lot of flexibility. All the Big 7 have to agree on a common standard or you have big problems, then there are the problems caused by the FRA. Under the current rules if the locomotive part of the system goes down you stop and get it repaired right there (fat chance), change lead locomotives (not always easy either), or establish absolute block clearance (can you imagine doing this on the Transcon or Overland Route). And then if it is a proprietary system of one manufacturer they have you over the barrel for pricing. Look at the recent experiences, Amtrak in Illinois, Rockwell-Collins could never get the system to work right and the government has poured millions down the drain. You'll note that even though the Santa Fe and IC systems work similarly, the design differences mean that the two are not compatible.

Positive Train Control utilizing GPS and other technoligies now in testing phases will make ATS obsolete within the next 10 years or so.

AAK Wrote:
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> Positive Train Control utilizing GPS and other
> technoligies now in testing phases will make ATS
> obsolete within the next 10 years or so.


You would think, but I wouldn't bet on it.

AAK Wrote:
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> Positive Train Control utilizing GPS and other
> technoligies now in testing phases will make ATS
> obsolete within the next 10 years or so.


I thought I read that the PTC experiment was deemed a failure and the companies involved are funding conversion of PTC-equipped lines to Cab Signals.

It might be 1930's technology, but it works. I think the big expense with rolling them out further is the cost of lengthening the signal blocks to handle the higher speeds.

Todd Clark
Canyon Country, CA
Trainorders.com

webmaster Wrote:
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> It might be 1930's technology, but it works. I
> think the big expense with rolling them out
> further is the cost of lengthening the signal
> blocks to handle the higher speeds.

In what way does it work? The signal is red, the train crew is asleep, train passes signal at 80 mph, ATS inductor causes the brakes to apply, train slows to 75 mph and hits stopped freight train 200 yards beyond the signal. The only way something simple like ATS helps is if you require empty blocks in advance of the signal or signal overlaps, which is effectively the same thing. Doing that will make a major reduction in track capacity. If the signal is red the inductor is off and will stop the train if the Engineer fails to acknowledge the ATS. If the signal is anything else the ATS is charged and nothing will happen, it has no ability to differentiate between a approach or a clear signal. Note also that if the Engineer acknowledges the ATS he is free to pass a stop signal the brakes will not be applied. The Europeans do better but at much greater costs, the new ETCS system (part of the larger ERTMS system) is costing in the range of 500k Euros per locomotive installation, a little less when installed in brand new locomotives when built, more as a retrofit, and this is with a system owned jointly by all potential manufacturers with required cross-compatability ( a Siemens equipped locomotive interfaces with an Alcatel equipped track system or any combination of manufacturers)

Soo; ATS gives a signal for ANY signal less than clear. In the case of the SCRRA and SDNR the engineer would have to Acknowledge an Advance Approach, an Approach, and then suddenly fall asleep without braking for the Approach in order to sleep through the Red. With signals placed no more then 2 miles apart, at 90 MPH you're talking at most a 1min 30sec from when the engineer acknowledges an Approach Signal until they pass a red. Personally, if I were in the engineer's seat running on a yellow signal I wouldn't be able to fall asleep in the next 90 seconds. Then when combined with other safety systems or regulations such as the alertor or a Fireman requirement (in the case of the SW Chief) there's too much going on in the cab for the engineer to miss six miles worth of signals of any type, much less approach signals.

That's how ATS is effective, it requires the engineer to be alert prior to them getting into trouble. Note that since the system has only limited efectiveness it only boosts available speed by 11 MPH, you'd need a slightly more effective system such as PTC or ACS to go above 90. (I believe PTC permitted 105 MPH operation, while ACS is currently allowing 150 MPH operation on the NEC)

mmmmmmm
Thay have some thing like this on the Victorian railways .
When you pass a block area an the lights are yellow it will trip the train brakes to on full an make the train just about slide to a stop.wwweeeeee bit hard on the poor passangers thou...loll
yours snoopy51

Jaanfo Wrote:
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> With a wayside system spot-checking the engineer
> train speeds are permitted above 79 MPH though the
> overall permitted speed increase above 79 is
> limited by the effectiveness of the Wayside
> system. ATS is the simplest form of Wayside
> Signal Actuation that I know of, thus it only
> permits an increase of 11 MPH over 79, up to 90
> MPH.

What rule does the FRA limit the speed to 90 mph with ATS? Beyond ATS, I thought it was a function of track or other restrictions or both, but not ATS.

barrydraper Wrote:
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> It's 1930's technology.

Actually it dates well before the 30's. The Class I railroads had at least one passenger division equipped with ATC (more sophisticated than ATS) in the 20's. There were some ATS type operations dating as early as the teens and oh-naughts, especially on some subways, Boston being one of them.

I'm not disagreeing that from a safety perspective, ATS, PTC, CS, installs are a plus, and that the cost alone should not be a prohibitive factor if defrayed amongst several "parties" in order to reach a common safety goal...however...

The discussion above is gearing implementation of these systems to translate directly into radical speed increases. Seems pretty clear that there is really only one operator that would benefit from such increases. When you consider the amount of unit train traffic that could likely never derive a benefit from speeds mentioned above(but clearly would derive the benefits from advancements like ECP), and possibly do even more to thwart such efforts(example:Coal train out in front of the Passenger train, and too much other traffic to cross the PT around him).

Upgrading of the signal system to any of the mentioned operating methods does not even begin to address the increased maintenance intervals and specifications required for 105 mph operation, versus where they are currently. Pricing and service models for freight movement are based on performance to schedule, so 90 - 105 mph isn't really a factor. What is even more likely is that the efficiency losses(higher MOW costs, higher fuel consumption, intensified eqpt. maintenance, etc.)associated with the upgrades required to operate freight at a significantly higher speed, would likely end up producing only marginally better transit times at a markedly higher cost, diminishing any real gains.

A real world example would be Conrail, who operated the nations busiest intermodal network at one time, and yet implemented systemwide speed reductions to it's TV and Mail fleet from 70 to 60 mph, when its research showed that overall schedules could still be met, fuel efficiency was enhanced, and additional savings were incurred through reduced track maintenance intensity.

Conrail also appeared to manage maintaining a fairly positive operating relationship with Amtrak as well.

Jaanfo Wrote:
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> Soo; ATS gives a signal for ANY signal less than
> clear. In the case of the SCRRA and SDNR the
> engineer would have to Acknowledge an Advance
> Approach, an Approach, and then suddenly fall
> asleep without braking for the Approach in order
> to sleep through the Red. With signals placed no
> more then 2 miles apart, at 90 MPH you're talking
> at most a 1min 30sec from when the engineer
> acknowledges an Approach Signal until they pass a
> red. Personally, if I were in the engineer's seat
> running on a yellow signal I wouldn't be able to
> fall asleep in the next 90 seconds. Then when
> combined with other safety systems or regulations
> such as the alertor or a Fireman requirement (in
> the case of the SW Chief) there's too much going
> on in the cab for the engineer to miss six miles
> worth of signals of any type, much less approach
> signals.
>
> That's how ATS is effective, it requires the
> engineer to be alert prior to them getting into
> trouble. Note that since the system has only
> limited efectiveness it only boosts available
> speed by 11 MPH, you'd need a slightly more
> effective system such as PTC or ACS to go above
> 90. (I believe PTC permitted 105 MPH operation,
> while ACS is currently allowing 150 MPH operation
> on the NEC)


Jaanfo, note the fairly recent British accidents at Southall and Ladbroke Grove to see the limitations of a very similar system (AWS). In the Southall accident the Engineer (Driver) was routinely canceling the AWS as he was passing many Double Yellow indications (similar to our Advance Approach) in succession, he became distracted and didn't notice passing a single yellow rather than another double yellow and then couldn't stop at the red and hit a freight crossing over with fatal results for some of his passengers. At Ladbroke Grove a relatively inexperienced driver misread a signal and ran a Red at an interlocking and slid into the path of a fast passenger train. The British decided to go with a more capable system TPWS and TPWSplus which have speed enforcement capability that cannot be overridden by the Engineer, and redesigned the interlocking at Ladbroke Grove. Note that the TPWS system is still less capable than a cabsignal/PTC system. The most capable systems available are the French TVM430 and the German LZB systems which provide continous cab signals with braking enforcement and the ability to program in speed restrictions. Both systems have the capability to operate at up to 200mph if the trains have the braking characteristics of the TGV or ICE. The European ETCS system will provide similar capability.

I did not say ATS is foolproof... Nothing is.. Just that you would have to be trying to screw up, or a complete fool to completely blow a red in ATS territory. More commonly out here I hear of engineers assuming they have a clear after a meet or not being familiar with a territory after an extended absence or signal change when there is an issue out here.

SOO6617 Wrote:
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> In what way does it work? The signal is red, the
> train crew is asleep, train passes signal at 80
> mph, ATS inductor causes the brakes to apply,
> train slows to 75 mph and hits stopped freight
> train 200 yards beyond the signal.

The IC had ? 2 or 3 short unsignaled ATS blocks on ether side of sidings. May have bin 1/4 mile blocks.
IC was widely known for FAST trains, If running behind on there schedule they pushed there gearing to get back on time.

Trainmaster's comments on the issue of high speed passenger mixing on a system with slower freight trains are on point. If you look at Japan or France, the ultra high speed trains (Shinkansen, TGV) run on a separate right of way. When the TGV ain't on its own trackage, for example the first half of the Geneva to Paris route, it operates at more pedestrian speeds.

The traffic pattern in Europe is also quite different and this helps support high speed rail. The distances are shorter. Freight movements occur predominately at night. Long distance night passenger runs are operated at a slower speed. Given the distances involved and the presence of sleeping cars you want to operate at a slower speed so that the passengers arive in the morning instead of a in the middle of the night.

QU25C Wrote:
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> SOO6617 Wrote:
> --------------------------------------------------
> -----
> >
> The IC had ? 2 or 3 short unsignaled ATS blocks on
> ether side of sidings. May have bin 1/4 mile
> blocks.
> IC was widely known for FAST trains, If running
> behind on there schedule they pushed there gearing
> to get back on time.

I had thought that this system was still in use a few years ago across Iowa. Is it in service now or has it been ripped out.

Sneebly

AAK Wrote:
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> Positive Train Control utilizing GPS and other
> technologies now in testing phases will make ATS
> obsolete within the next 10 years or so.

I agree. Current GPS units on locomotives give exact location and speed. Coupled with the right technology this will be the future of train monitoring. Its interesting (and scary) to pull up the records of your engine to see if you were speeding or how much you were moving each shift. To start another tangent, I believe this technology will end the conductors position on through trains (since someone else will have the ability to stop your train).