2009/1/29 James Laver <james.la...@gmail.com>: > 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. /joel
