Symbolic Forest

More notes on the Lambrigg and/or Grayrigg train crash from a couple of weeks ago. Continued from here.

As I said in the first part, it was known for many years that junctions are a dangerous thing. Any place where a train has a choice of routes to take is a danger point, and the railways, for a hundred years or so, got around this by avoiding them as much as possible. A freight train, going into a siding, would have to run past it, stop, and back up slowly into the siding.

This is a very safe and careful thing to do, but it is very, very slow. Trains take a long time to slow down, and a long time to stop. Backing up has to be done very slowly, too, and the whole operation blocks the main line for rather a long time. If the train could run directly into the siding, things would be a lot faster.

Similarly, if one line of a pair has to be closed for engineering works, trains have to run in both directions over the remaining line. The old way of doing this was very slow indeed – the train would have to stop, reverse backwards onto the other track, then reverse again so it was going forwards. All very fiddly and slow,^* and it would have been easier if there was a faster way to do things.^**

So, in the 1960s and 1970s, an awful lot of the rail network got simplified and redesigned. In particular, “emergency crossovers,” like the ones involved in the Lambrigg crash, were installed every few miles on the main lines. Essentially, all they were there to do was let trains switch across to the other track if one line had to be closed for maintenance. This, though, meant greatly increasing the numbers of relatively dangerous, maintenance-heavy facing points on high-speed main lines. Cost was no longer so much of an issue – greater automation and mechanisation of the railways meant that all points were fitted with exactly the same locking equipment, so the legally-required and previously expensive locks on facing points were now provided for free. Maintenance still mattered, though.

Note that I said “relatively dangerous”. Facing points are maintenance-heavy, purely because they are intrinsically more dangerous than trailing points. This isn’t an issue, though, so long as the maintenance gets done. And, over the years, all points started to be given the same level of maintenance – there is in many ways no longer a distinction between facing and trailing points, maintenance-wise, because as I said above they nearly all have the same fittings.

So long as the maintenance gets done. That is the key. Railways just aren’t maintained in the same way that they used to be. There’s no longer a man walking every stretch of track, every day of the year, looking out for faults, like there used to be. If facing points aren’t maintained properly, they become dangerous, and they’re likely to cause accidents, such as Lambrigg and Potters Bar. The problem is, they’re vital to being able to run the railway smoothly and flexibly. If you want to run a flexible railway, it’s going to cost you more. You have to be willing to pay the price, however you want to pay it.

* there are lots of other rules involving people waving flags and people whose job is just to be unique, but I won’t bore you with them.

** This has nothing to do with the closing of alternative routes, incidentally, which people sometimes go on about as being a Bad Thing in connection with the rail network. Alternative routes are often a lot less useful than people think.

Keyword noise: accident, crash, derailment, facing point lock, facing points, FPL, flexibility, Grayrigg, history, junctions, Lambrigg, maintenance, points, Potters Bar, preventative maintenance, railway, railway history, signalling, shunting, trains.

Some notes on the Lambrigg rail accident (also known as the Grayrigg crash in the media).

Facing points are a bad thing. Facing points have always been known to be a bad thing. This has been known ever since the railways were first created.

A facing point is, essentially, a junction, where one line of rails splits in to two. The opposite is a trailing point: a junction where two lines come together to become one. You will quickly realise that a facing point becomes a trailing point if you stop your train and reverse it, and vice-versa.

Facing points are dangerous; trailing points are safe. You can drive through a faulty trailing point, or a trailing point set the wrong way, and you’re unlikely to have your train come off the track. You’ll probably wreck the point, unless it’s designed for you to do that to it,^* but your train will be unharmed. Do that with a faulty facing point and your train is going to end up all over the place.

Now, this was never a problem, because for years main-line railways only ever had tracks in pairs, one track for each direction. Going the Wrong Way was strictly against the rules. The main reason for this was to stop trains meeting head-on, but it had a secondary benefit: it meant that engineers could get rid of as many facing points as was possible. This was partly an expense issue. Anyone who’s ever had a train set will know that if you switch a facing point whilst a train is on it, Bad Things will happen as different parts of the train try to go in different directions. This isn’t what happened at Lambrigg/Grayrigg, but it has the same result; and when the government realised, they quickly insisted that all facing points be fitted with a complex arrangement of locks and train-detectors to make sure you can’t do that. Back then, that involved mechanical locks which needed a lot of careful and regular maintenance and adjustment. Now, most of it is done electrically, but there is still a mechanical lock somewhere in the point’s machine that holds the various moving parts of a point fast when a train is nearby. Of course, that’s only any use when the rest of the point is mechanically sound too.

So, anyway, as I said, if all lines are one-way only you don’t need facing points. Not until you get to big junctions, at any rate, where you have to live with them. Freight lines didn’t need the expensive facing point locks, so freight trains always backed into sidings. And the railways happily ran like that for a hundred years or so, and facing points rarely caused accidents. In modern times, though, it didn’t really work.

The second part of this article continues here

* Lots of points on rural lines, nowadays, are what’s called “sprung points”. They’re not controlled, they just sit there. Use them as a facing point, and they’ll always send you the same way.^** Use them as a trailing point, and you can approach them from either route without problems.

** Left, usually, on British main line railways at any rate.

Keyword noise: accident, crash, derailment, facing point lock, facing points, FPL, Grayrigg, history, Lambrigg, points, railway, railway history, signalling, trains.