Blog : Posts tagged with 'rail'

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Photo Post Of The Week

Another camera-equipped wander around the city


More weekend jaunts around Bristol.

Eroded wall, Southville Alleyway Bridge rail, Wapping Road, Bristol
Yachts, Floating Harbour, Bristol Holy Trinity Church, Hotwells Vauxhall Bridge, Bristol

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Facing Points

In which we delve into railway history following a recent accident


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.

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* 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

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