‘Each Underground line has one or more train maintenance depots, which are very quiet during the day but hives of activity at night. Getting all the trains in and out of the depots is a carefully timetabled exercise and a huge logistical challenge- especially when you consider that the Northern line, for example, has 106 trains.
‘Some trains will undergo light maintenance- which takes around ten minutes per train- while others get what we call a “heavy overhaul”, where they’re put up on jacks over a long pit so that the technician can get underneath and make sure everything’s in good working order. They’ll also all go through the train equivalent of a car wash on the way in and out of the depots.
‘At all of our terminus stations, we have staff who check trains before they go to the depot, so 99.999 percent of the time, passengers don’t end up in depots. We do have the odd occasion where someone gets, as we say, “over carried”- but it’s very rare.’
Nigel Holness, London Underground’s operations director for the Jubilee, Northern and Picadilly lines.
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