On Mon, 1 Jan 2007 19:21:34 +0000, Tom Anderson
wrote:

While we're sort of on the subject, why do tube lines normally close at
night? Maintenance of some sort, AIUI, but what, exactly? What is it that
requires a six-hour closure of every line every night?

Firstly a correction - there is less than 5 hours a night between power
off and power on the following morning on weekdays. There is a little
more time Sat Night to Sunday morning.

A fair amount of small scale engineering work gets done every night to
the track. Track wears out or bolts come lose - they all need to be
replaced / tightened etc.

Track areas are cleaned to prevent a build up of litter that can cause
fires or get caught in equipment thus causing track fires or signal
failures or damage to trains.

There is also a lot of inspection work to make sure that rails are safe
(checking for broken rails), signals are working and that work sites on
or near the track are clean and tidy.

In addition works are done in stations to upgrade them, install new
equipment, convert rooms to other uses, cleaning of escalators to remove
dirt, dust, fluff and oil / grease build ups and cleaning of the
stations themselves. Some assets cannot be repaired during the day if
they are too close to the track or too high - lights, cameras, speakers,
signs etc.

The trains also need to be washed and cleaned and have minor repairs
done to them. Bigger repair jobs will be done on the trains during
daytime when they will be out of service and their slot taken by a spare
train.

People always quote New York as having 24 hour tubes but the builders of
that system had the foresight to build 3 or 4 tracks and crossovers /
junctions on almost all routes which provides a lot of flexibility for
maintenance purposes. The all night service pattern changes regularly in
NYC and that is to match the engineering works against the tracks that
can be used.

When LU's system gets to a modern state with better quality assets and
much better predictive maintenance techniques it may be possible to
reduce engineering hours but for now there is still a hell of lot of
stuff that has to be done to keep the railway safe and working. I dread
to think what would happen to reliability if these checks and
maintenance works were not done.
--
Paul C


Admits to working for London Underground!