How reliant are UK railways on the Global Positioning System?

[Western 52]

If the GPS was suddenly not available, perhaps due to some form of sabotage or hacking, what effect would that have on the railway system? GPS is said to be vulnerable to attack, so should railway operators be worried, although GPS is probably low risk?

 

[_toommm_]

Do we use GPS for much on the railways? I believe it’s used in certain places to update times it passes over a certain point, but AFAIK there’s not much, if anything, in the way of safety-critical bits of infrastructure that rely on GPS.

More than happy to be corrected though.

 

[The Planner]

If the GPS was suddenly not available, perhaps due to some form of sabotage or hacking, what effect would that have on the railway system? GPS is said to be vulnerable to attack, so should railway operators be worried, although GPS is probably low risk?

Not a lot.

 

[zwk500]

Do we use GPS for much on the railways? I believe it’s used in certain places to update times it passes over a certain point, but AFAIK there’s not much, if anything, in the way of safety-critical bits of infrastructure that rely on GPS.

More than happy to be corrected though.

Listing the uses may not be the most responsible answer to the OP who was concerned about attacks!

GPS is not used by the signalling system for train detection, so although losing it would be disruptive it wouldn't shut the network down.

 

[Irascible]

On a slight tangent, we can still use nearly all Galileo services ( unless we've renegotiated access to the super-secure ones then it'd be all of them ).

 

[_toommm_]

Listing the uses may not be the most responsible answer to the OP who was concerned about attacks!

GPS is not used by the signalling system for train detection, so although losing it would be disruptive it wouldn't shut the network down.

I only mentioned it as I didn’t believe it was safety-critical, and that there were other methods used alongside GPS.

 

[zwk500]

I only mentioned it as I didn’t believe it was safety-critical, and that there were other methods used alongside GPS.

It was more people answering your question that I had in mind! I think that the knowledge that GPS is used to report live running times is A. Not particularly helpful for malicious purposes, and B. Fairly widely known.

 

[_toommm_]

It was more people answering your question that I had in mind! I think that the knowledge that GPS is used to report live running times is A. Not particularly helpful for malicious purposes, and B. Fairly widely known.

Ah, fair enough.

 

[Western 52]

Do on train information systems generally use GPS?

 

[Watershed]

Do on train information systems generally use GPS?

Yes. And some ASDO systems also use it.

 

[Western 52]

Yes. And some ASDO systems also use it.

What are ASDO systems?

 

[zwk500]

What are ASDO systems?

Automatic Selective Door Operation (I believe) - so that trains longer than the platform open only the appropriate doors.

 

[Western 52]

Automatic Selective Door Operation (I believe) - so that trains longer than the platform open only the appropriate doors.

Many thanks- not heard that term before.

 

[zwk500]

Many thanks- not heard that term before.

I think the exact acronym (and method of detection) can vary between trains/tocs. Some are beacons, some GPS and some the Guard.

 

[thenorthern]

As others have said not a lot.

It's important to remember that most devices in sold in the United Kingdom also use the Russian GLONASS locator system so if the US Government did switch off GPS then most satellite locator devices would still work.

 

[edwin_m]

The big risk for satellite navigation systems is if space junk builds up to such an extent that it becomes impossible to sustain enough satellites. That will affect all the navigation systems equally.

 

[Dryce]

As others have said not a lot.

It's important to remember that most devices in sold in the United Kingdom also use the Russian GLONASS locator system so if the US Government did switch off GPS then most satellite locator devices would still work.

Strategically - if the US felt the need to switch off their network ... then so would other nations?

Or worse - actively distort positions without warning.

 

[BayPaul]

The big risk for satellite navigation systems is if space junk builds up to such an extent that it becomes impossible to sustain enough satellites. That will affect all the navigation systems equally.

Not such an issue for Sat Nav systems, as they are medium earth orbiting satellites, where I understand there is plenty of room. The crowded part of space is for geostationary orbits, as that is a single line around the equator, so is most vulnerable to space junk.

Strategically - if the US felt the need to switch off their network ... then so would other nations?

Or worse - actively distort positions without warning.

The likelihood of this is pretty low. Active distortion of positions can be easily combatted using DGPS (differential Global Positioning System) technology - basically using GPS to plot the position of a fixed ground station, and then transmitting the position error to surrounding receivers so they can apply the same adjustment to their position. As this effectively renders selective availability pointless, the US has 'promised' that they will never again use it on GPS.
I don't think any nation would be likely to start to shut down systems that are absolutely safety critical to commercial aviation, and are virtually safety critical to merchant shipping as well, though ships do have more alternatives, especially in coastal waters, without giving at least enough notice to get aircraft out of the sky. It is difficult to envisage a Domesday scenario which requires all 3 systems to be shut down instantly - perhaps an indiscrimate firing of nuclear missiles by China, but I can't imagine they rely totally on foreign satellite navigation systems anyway.

 

[Dryce]

I don't think any nation would be likely to start to shut down systems that are absolutely safety critical to commercial aviation, and are virtually safety critical to merchant shipping as well, though ships do have more alternatives, especially in coastal waters, without giving at least enough notice to get aircraft out of the sky. It is difficult to envisage a Domesday scenario which requires all 3 systems to be shut down instantly - perhaps an indiscrimate firing of nuclear missiles by China, but I can't imagine they rely totally on foreign satellite navigation systems anyway.

Without scare mongering - the West in particular has become very complaceent about this since the end of the Cold War.

So we have products that have critical single source products. We have consumers and businesses operating using software that is enabled via the internet and holding data on servers accessed via the internet. We use GPS as a ubiquitously availble service.

NONE of these are guaranteed and all are critical points of failure in the event of major infrastructure damage (deliberate attack or inadvertent error).

And anybody involved incritical infrastructure such as the ralways needs to take this into consideration.

 

[dosxuk]

I don't think any nation would be likely to start to shut down systems that are absolutely safety critical to commercial aviation, and are virtually safety critical to merchant shipping as well, though ships do have more alternatives, especially in coastal waters, without giving at least enough notice to get aircraft out of the sky.

There's various parts of the planet with standing NOTAM's for unreliable GPS reception, particularly around the middle east and China, caused by nations either experimenting or wanting to reduce the reliability for their neighbours. Aircraft have multiple options for navigation and aren't solely reliant on GPS (although increasingly instrument approaches are becoming reliant on GPS, primarily because of not having to spend loads of money on ground equipment), however even then it doesn't preclude a visual approach and landing.

 

[jopsuk]

if we're at the stage of the US and Russia both switching off their systems I rather fear that issues with selective door operation are the least of our worries!

 

[Irascible]

if we're at the stage of the US and Russia both switching off their systems I rather fear that issues with selective door operation are the least of our worries!

Europe has it's own system, as do China & India. I think we can discount the UK govts plans for a national one thanks to dropping out of super-secure-Galileo as the usual impractical headline-generator.

As was said above there's still some radio nav aids left, although they're intended for aircraft & not terribly practical for receivers stuck on the ground. Decca nav for shipping was shut down 20 years ago... I hope crews are still trained on sextants

You can of course use GSM masts to get a fix, you don't have to use satellites.

 

[edwin_m]

Europe has it's own system, as do China & India. I think we can discount the UK govts plans for a national one thanks to dropping out of super-secure-Galileo as the usual impractical headline-generator.

As was said above there's still some radio nav aids left, although they're intended for aircraft & not terribly practical for receivers stuck on the ground. Decca nav for shipping was shut down 20 years ago... I hope crews are still trained on sextants

You can of course use GSM masts to get a fix, you don't have to use satellites.

Back in around 1989 as a graduate trainee at BR Research I did some trials on navigation for use on trains. A Decca system worked fine around Derby, though not very accurately, but was noticeably worse when near power lines. When we tried it on an 87 from Euston to Piccadilly we got no readings whatever. We later tried a GPS - the Americans had been thinking of using them but I think I was the first person in Europe to fit one to a train and we had to schedule the test runs when enough of the limited number of satellites were above the horizon. At the time that wouldn't work under OLE either.

 

[Irascible]

Back in around 1989 as a graduate trainee at BR Research I did some trials on navigation for use on trains. A Decca system worked fine around Derby, though not very accurately, but was noticeably worse when near power lines. When we tried it on an 87 from Euston to Piccadilly we got no readings whatever. We later tried a GPS - the Americans had been thinking of using them but I think I was the first person in Europe to fit one to a train and we had to schedule the test runs when enough of the limited number of satellites were above the horizon. At the time that wouldn't work under OLE either.

Hah! that's great. The EU still has LORAN stations, I wonder if they'd work at all... I'd imagine there'd be the same problem as DECCA though.

( Edit: nvm, no LORAN in Europe anymore either )

I found a rather short paper looking at methods of tracking rail vehicles without GNSS ( not anything particularily interesting ) but it's obviously a field of study. It shouldn't be a huge problem though, really - if a rail vehicle deviates from it's preset route ( ie, any of them ) you've got a bigger problem than tracking where you are, so perhaps a basic INS & a map would be enough.

 

[Annetts key]

Automatic Selective Door Operation (I believe) - so that trains longer than the platform open only the appropriate doors.

Some trains use Eurobalises (that are not part of a ETCS) to locate where they are. More details here.

The Great Western ASDO/APCO project is a small project upon which great things depend. The project has required an exceptional level of agility and collaboration from the project team of colleagues from Alstom and Network Rail. This project is deploying eurobalises across Wales and the West of England to enable new rolling stock and the biggest timetable change in a generation on the Great Western Railway in December 2019, all whilst platforms are being extended and overhead line electrification is being delivered. Network Rail's Signalling Design Group has provided the signalling designs, and Alstom have manufactured, programmed, installed and commissioned the eurobalises. The eurobalises are installed in the four foot and send a fixed telegram message to the train to enable Automatic Selective Door Opening (ASDO) and Automatic Power Change Over (APCO). ASDO is required where station platforms are shorter than the train, and APCO where the train pantograph is required to be up or down according to whether overhead lines are energised. This means that the project brings safety and capacity benefits on stream for GWR's customers, well in advance of completion of the full scope of electrification and platform extensions.

 

[Nym]

Small point to note, if they're Eurobalises, they're ETCS. They just might not be being used by the signalling aspects of ETCS, similarly to how TASS is "Not part of ETCS".

 

[zwk500]

Some trains use Eurobalises (that are not part of a ETCS) to locate where they are. More details here.

Hence why I put some are beacons, apologies if the terminology doesn't quite map

 

[Annetts key]

Small point to note, if they're Eurobalises, they're ETCS. They just might not be being used by the signalling aspects of ETCS, similarly to how TASS is "Not part of ETCS".

Well, there is no ETCS signalling system on Western at the moment, but there are Eurobalises, and they are used as detailed in my earlier post. They are only used for fixed position information for the on board equipment on the train.

As far as I am concerned, an ETCS is primarily a signalling system designed to provide the same or better protection than a conventional signalling system. Provision for some additional facilities has also been included.

Eurobalises and the on train equipment are part of a ETCS. But for these parts to become a ETSC signalling system you need more than just these parts. Hence, as far as I am concerned, in order to try to keep the terminology simple, I thought saying what I said was the simplest way of describing it.

Hence why I put some are beacons, apologies if the terminology doesn't quite map

That’s fair enough. Although I should point out that the word beacon is also used to describe the fixed GWML ATP equipment mounted in the track. Similarly the term ‘loop’ is used by both TPWS and ATP, but these are different things between the two different systems.

As with lots of technology, the same equipment can sometimes be used for more than one purpose. Or the same term is used for different equipment. And sometimes people mix and match between. It makes life more interesting, but can also be confusing!

 

[Orac]

The main problem with GPS is that signals are blocked by buildings, dense foliage, station roofs and other obstacles near the track, so you often can't get enough signals to compute a position solution (a minimum of 4 is needed). Multi-constellation GNSS (GPS+Galileo+GLONASS+Beidou) gives you about four times as many signals. However, you can still get large position errors (10s of metres) because many of the signals are reflected off buildings while the receiver software assumes that they travel direct from the satellite.
Various advanced solutions are being developed for urban areas that could also be adapted to the railways:

Supercorrelation Plus 3D Mapping-Aided GNSS

Inertially-aided extended coherent integration makes a GNSS receiver more sensitive to directly received signals than to reflected signals whenever the receiver

insidegnss.com

(Declaration: I am one of the authors)
However, there will still be areas where GNSS is not usable, tunnels being the most obvious example. Other technologies, such as wheel-speed sensors, inertial sensors, Doppler radar and balises will therefore still be needed.

 

[Ediswan]

Hah! that's great. The EU still has LORAN stations, I wonder if they'd work at all... I'd imagine there'd be the same problem as DECCA though.

( Edit: nvm, no LORAN in Europe anymore either )

Unsurprsingly, other people have noticed that over-reliance on GPS is a risk. LORAN may be on its way back as eLorain: https://www.xyht.com/gnsslocation-tech/the-return-of-loran/