British Rail Moving Forward with Sat-Nav/GPS

de1orean writes "The BBC is reporting that after a successful limited trial using GPS satellite navigation to improve train safety and efficiency, British Rail is committed to instituting sat-nav throughout the system. It may be in operation as early as 2008."

Comments

First impression

[Dancin_Santa]

It's a train. It's not like these things can wander all over the place.

Maybe if they were able to get them to run on time like they do in Japan and Fascist Italy, they could tell where the trains were by just looking at the clock.

Re:First impression

[ComputerSlicer23]

At least in the U.S., I know a couple of dispatch people (the train equivilent of "Air Traffic Controllers" for planes). One always told me that a train dispatcher made more life of death decisions per hour then then an ATC person did. He joked that guys used to retire from doing train work to being an ATC for the low pressure, low stress atmosphere. I'm not sure either of those statements is true, but I'll bet that it is true, that keeping trains running smoothing isn't as trivial as you make it out to be.

In the end, well, trains don't always travel the same speed, they don't always travel at the speed they are told to. Sometimes they break down. Sometimes the switches aren't thrown properly (so there really are two dimensions, possibly more), sometimes a train runs away. Some times a train is on a section of track its not supposed to be. Trains aren't a trivial problem (we actually had to write a simulation of this in college in a RTS class, you had to do the computations and throw the switches at the right time, or you had yourself a fairly serious collision).

With trains at least, by the time anyone can visually tell you this, all you can really do is jump off and save yourself. It's literally a million pound weapon of death, by the time anyone can see the problem it's over. Having a GPS system on the train would enable you to spot all sorts of upcoming problems with out having to communicate with anyone onboard.

Kirby

Re:Low tech incompetence

[ozmanjusri]

Why do fools insist on going to high tech solutions when they can't even get the low tech stuff right?

Because they can't even get the low tech stuff right. The key failure points on rail systems are the switches & signals that control which section of rail the train is on, and the locomotives themselves which can stop, speed up or slow down.

Knowing precisely where a loco is on the track is the single most important aspect of rail safety, so that train control can switch a train onto another section of track, or into a siding to avoid collision, or can warn the driver to speed up or slow down to achieve the same result. In non-gps systems is this is done with trackside transponders and dead reckoning. A modern positive train separation (PTS) system based on GPS is simpler and more reliable than the transponders it replaces, and allows for more sophisticated controls such as automatic speed limiting.

It's also far from uncommon. Similar systems have been available for years.

Lost trains not as uncommon as you might think

[timboc007]

GPS is not so much to let the train driver know where he/she is (although that is a valid use under some control systems) as it is to let the train controllers and the safety interlocking systems know where the train is. This is obviously an important consideration before trying to place another train into that location ;-)

Historically there are rail systems around the world that do without this basic functionality, particularly in areas of low density traffic. Instead, procedures were established by which a section was proven clear. The signaller at the entrance to the section (or 'block') would ring a bell to let the signaller at the exit from the block know that a train was entering the block. The signaller at the exit would then ring a bell back to the signaller at the entrance when the train cleared the block section.

This worked to some extent (and indeed continues to work in many places around the world), but was highly susceptible to human error. A couple of years ago, at Glenbrook in Sydney's west, a crash may have been averted had the signaller had some indication to remind him that the Indian Pacific had not yet cleared the section ahead of the suburban passenger train. As it was, he forgot to inform the second train of the first's existence, with the result that the second rammed into the back of the first.

The most common method for establishing a train's locations is the track circuit - a power source is placed on one end of a section of track, whilst a receiver measures the voltage at the other end of the section. When the train is on the section, the axles of the train short out the circuit, and the receiver measures a 0V potential. This is fed back to the local interlocking, and any signals which require this track to be clear in order to give a proceed aspect will go to stop, preventing any other trains from entering the section and hence avoiding a crash. This is what the article refers to as the "current block signalling system".

The problem with track circuits is twofold. As mentioned in the article, the accuracy is not great - track circuits can often extend over several kilometres, so the best that can be said is that the train is "somewhere within that circuit". Secondly, the track circuits are relatively difficult to maintain - maintenance crews must go to each track circuit in order to perform routine maintenance. Travel time being relatively unproductive, rail operators would much prefer that maintenance be achievable in one location.

GPS would overcome both of the problems listed above. The accuracy would be greatly increased, limited only by the accuracy of the GPS. Similarly, the equipment for the location would all be located on the rollingstock, rather than trackside, and could be brought to the maintainers. Further, with systems like the European Rail Traffic Management System (ERTMS), GPS can be used to run trains much closer together in what is called a 'moving block configuration'.

This translates into lower running/maintenance costs, combined with greater efficiency - is it any wonder BR are interested? Aren't you?