On Fri, 20 Aug 2010 19:46:24 +0100, Tom Anderson
wrote:

The weakness, of course, is the reservoir. If it isn't filled (eg a train
has been parked for ages), or it runs out (eg a train has parked
recently), or it leaks or is vented by mistake, you've lost your ability
to apply the brake. I don't know how this is dealt with - i would guess by
making the reservoir quite large and very reliable (and it is, after all,
just a big tank with a pipe coming out of it)

Part of it is additionally that trains tend to run with more than one
vehicle (not always, I know), and each has its own reservoir. Thus,
if in a 6-car train 2 cars lose their braking system completely, it
will still stop.

Exactly. The sort of thing that in nuclear power engineering is called a
scram - a last-ditch, absolutely foolproof, not necessarily recoverable,
way of stopping a runaway.

On the railway that's often handled off the vehicle by a set of catch
points, which are basically points that deliberately derail the train
and send it off into a sand drag or something. Not that useful on
LUL, though.

For engineering work, derailer ramps are often fitted at each end to
catch any runaway and stop it by sending it off the track in the same
sort of way. Maybe that's something LUL should look at doing - though
if it had happened here the two engineering staff on the runaway might
well not have survived the experience.

Neil
--
Neil Williams in Milton Keynes, UK
To reply put my first name before the at.