Anyone know why the DLR tunnels under the Thames to Greenwich and down
to Bank are lit up inside unlike the tube tunnels?

Seems a bit strange - people are used to travelling in the dark in
tunnels, so why bother lighting those particular ones up?

Something to do with the passengers seeing out the front and rear windows
maybe since they have no cab?


"Stevie" wrote in message
oups.com...
Anyone know why the DLR tunnels under the Thames to Greenwich and down
to Bank are lit up inside unlike the tube tunnels?

Seems a bit strange - people are used to travelling in the dark in
tunnels, so why bother lighting those particular ones up?

Could be for detraining reasons in an emergency but they
don't need to light the whole tunnel for that. Tho it seems
to be an unofficial policy on the railways to waste
as much electricity as possible. How many times have you
been on a train in bright sunlight and the interior lights are
on when theres no tunnel for miles if at all? And lets not
forget the new "efficient" 377s brought in on Southern
and elsewhere than use so much more power than the
old slam door stock that they had to build new substations!
Very enviromentally friendly. I remember when I was
younger that they used to switch the lights off fairly
frequently on the tube when the train was above ground
but they don't seem to bother now.

B2003

"Stevie" writes:
Anyone know why the DLR tunnels under the Thames to Greenwich and down
to Bank are lit up inside unlike the tube tunnels?

Yes, it's so the drivers on the DLR can... oh. :-)

Actually, I suspect the tunnels are lit in case of an emergency where
passengers have to evacuate themselves without staff assistance. The
tube tunnels were never designed for that -- after all, if something
happened to the driver, the guard could deal with things, right?

Note that the DLR tunnels are also provided with a walkway, unlike
most tube tunnels.
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Toronto | time you go by the Book, which is mostly a collection
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On 27 Aug 2005 08:50:32 -0700, "Boltar"
wrote:

Could be for detraining reasons in an emergency but they
don't need to light the whole tunnel for that. Tho it seems
to be an unofficial policy on the railways to waste
as much electricity as possible. How many times have you
been on a train in bright sunlight and the interior lights are
on when theres no tunnel for miles if at all? And lets not
forget the new "efficient" 377s brought in on Southern
and elsewhere than use so much more power than the
old slam door stock that they had to build new substations!
Very enviromentally friendly. I remember when I was
younger that they used to switch the lights off fairly
frequently on the tube when the train was above ground
but they don't seem to bother now.

I am not an electrician, but... someone told me that actually
switching on fluorescent lighting uses more power than leaving it
running for quite a number of hours.
--
Nick Cooper

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On 27 Aug 2005 08:50:32 -0700, "Boltar"
wrote:

Could be for detraining reasons in an emergency but they
don't need to light the whole tunnel for that. Tho it seems
to be an unofficial policy on the railways to waste
as much electricity as possible. How many times have you
been on a train in bright sunlight and the interior lights are
on when theres no tunnel for miles if at all?

Hamburg's DT4 U-Bahn units have a sensor on each end of the train to
turn the lights on just as you enter a tunnel. However, this may well
have backfired on the environmentally-friendly Germans - it takes as
much energy to start a fluorescent tube as it does to run one for
quite a period of time, as I recall.

Going back, I'm sure I remember that Merseyrail units used to have the
lights turned off until they reached Walton (for the Kirkdale tunnel),
though I can't remember when they started having them on throughout.

Neil

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On 27 Aug 2005 08:50:32 -0700, "Boltar"
wrote:

Could be for detraining reasons in an emergency but they
don't need to light the whole tunnel for that. Tho it seems
to be an unofficial policy on the railways to waste
as much electricity as possible. How many times have you
been on a train in bright sunlight and the interior lights are
on when theres no tunnel for miles if at all? And lets not
forget the new "efficient" 377s brought in on Southern
and elsewhere than use so much more power than the
old slam door stock that they had to build new substations!
Very enviromentally friendly. I remember when I was
younger that they used to switch the lights off fairly
frequently on the tube when the train was above ground
but they don't seem to bother now.

A bit OTT, but on the Paris RER the lighted are on and off all the
time. I wondered if they were automated.

Nick Cooper (and similarly Neil Williams) writes:
I am not an electrician, but... someone told me that actually
switching on fluorescent lighting uses more power than leaving it
running for quite a number of hours.

They were wrong. For "hours", you should read "seconds". This
should be obvious if you think about the wattage rating of the
lights, and the fact that turning them on doesn't overload the
circuits.

However, almost any type of electrical equipment tends to have a
shorter life if switched on and off frequently. (People who know
what they're talking about typically recommend that lights in a
home or office should be left on if they'll be needed again a few
minutes later.)

Also, sometimes when a fluorescent light is near failure, it will
stay lit once it gets started, but needs a minute or two of warmup
before it will start -- and because it draws more power during
startup, other lights on the same circuit may also fail to start.
quickly. Turning them off then makes this failure mode possible
when they're turned back on.
--
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Toronto can I judge whether I need to know it?
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My text in this article is in the public domain.

JRS: In article , dated Sat, 27 Aug
2005 22:27:12, seen in news:uk.transport.london, Nick Cooper
posted :

I am not an electrician, but... someone told me that actually
switching on fluorescent lighting uses more power than leaving it
running for quite a number of hours.

I can believe the first five words.

In fact I can believe what you write after that; but not what I suspect
someone, if correctly quoted, meant by it.

Power is rate-of-energy, corresponding to the speed of an electricity
meter. Energy is basically what one pays for.

I can easily believe that the start-up current, and hence the start-up
power, exceed the continuously-running value; though I do not assert it
to be so.

But starting takes seconds only; so if it used more energy than running
for hours, which is 3600 times longer, then it would draw about 3600
times the current. The best typical modern fluorescent draws about 10 W
running, say 40 mA; 3600 times that is 144 A. The full rating of a
small domestic installation is of the order of 100 A. The main fuse
might survive; the local one would not. Thus it cannot be so.


The other consideration for expense is tube-life; it's reasonable to
believe that turn on/off wears the tube out as much as a rather long
period of steady running. And tube-life matters not just for tube-cost
but costs of fitting a new tube to replace an old one.

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