My New Job (Was: Social Thurs 8 Jan 2009)

Joel Bernstein joel at
Thu Jan 29 14:28:15 GMT 2009

2009/1/29 James Laver <james.laver at>:
> Are signal failures still "driver ignored signal" or is the signal
> quality on the district line actually that appalling

>From LU's website

There are many reasons why signals fail. However, in many cases, the
signalling system itself is working normally, but the equipment has
detected a problem with the track. Because signals are designed to
'fail safe' whenever a fault occurs, signals turn to red and trains
stop running.

As the Tube's signalling system uses small electrical currents in the
track to detect the movement of passing trains, signal failures
sometimes happen when there is a short circuit between the running
rails. These short-circuits may occur after heavy rainfall, when
puddles of water build-up on the track - particularly on our open air
sections of line. Also, with our high frequency of service, the
accumulation of iron filings (from the daily wear and tear of trains)
across insulated joints between sections of track may also cause
problems. There have even been cases of rodents chewing through
cables, turning signals to red!

So there you go.


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