London Banter - View Single Post - DLR

Recliner[_3_] · April 25th 15, 10:58 PM posted to uk.transport.london

"Clive D. W. Feather" wrote:
In message , d wrote:
Except the person who was killed fell on the track by accident apparently
12 seconds before the train ran over her. Unless the driver was asleep he'd
have had no problem stopping the train in time.

Is that so? It's not obvious: a main line train takes 90 seconds to stop
from 100 mph at the braking rates the signalling is designed for.

A 3-unit DLR train is 84 metres long. The braking system is designed for
0.6 m/s^2, so that means the train will enter the platform at 10 m/s and
take 16.7 seconds to stop. 12 seconds before that the train is doing 17.2
m/s and is 162 metres from the start of the platform.

Suppose someone was at the entry end of the platform and fell at that
point, the driver takes 1 second to react, and the emergency braking rate
is 1.2 m/s^2, then after 1 second the train is 146 m from the platform
and at 16.6 m/s. It will then take 13.8 seconds to stop and proceed
another 115 m. So, yes, in that situation it will work.

I'll let you do the calculations for other places on the platform.

However, will the victim be visible at 162 metres from the platform?
Particularly if there's a curve on the track.

Unless you're claiming that no train with a driver has ever managed to make an
emergency stop before hitting something or someone on the track in the entire
history of railways, then I think you'll have to concede that having a pair
of eyes up front is probably a Good Thing.

Will it be worth the cost? How much will it cost to add a driver to every
DLR train? If I recall the previous posting, we're talking about one
accident every 5 years and one suicide a year.

I think the stats showed four probably accidental fatalities and six
successful suicides in 11 years. The latter would probably still happen
with or without alert drivers or obstruction detectors, if the would-be
suicides jumped just as the train entered the platform at speed. That means
that only about one accidental death every three years might be saved, and
that's assuming they fell early enough for the driver or detector to see
them and stop the train in time.