Why does the signal at the country end of the down Central Line at Stratford
have Red, WHITE and Green aspects? It wasn't just a faded yellow!

MaxB

On Tue, 14 Nov 2006 11:54:39 -0000, MaxB wrote:

Why does the signal at the country end of the down Central Line at
Stratford
have Red, WHITE and Green aspects? It wasn't just a faded yellow!

Possibly a tripcock tester?
http://www.trainweb.org/tubeprune/Si...photos.htm#Fig 3

The tester is usualy next to the track 3/4 of the way along the platform,
with the white light next to the starting signal.

--
Fig

MaxB wrote:
Why does the signal at the country end of the down Central Line at Stratford
have Red, WHITE and Green aspects? It wasn't just a faded yellow!

It's part of the Automatic Train Protection/Control system. There
isn't a signal at the entrance to every block, trains being controlled
by codes transmitted in the blocks. Where signals are retained, a
green aspect indicated that all blocks up to the next signal are
transmitting a proceed code. A white light indicates that a proceed
code is being transmitted, but not by all blocks to the next signal.
Red means stop (proceed code not being transmitted).

It wasn't appropriate to use yellow, as on traditional signalling
systems that would indicate to the driver that he was clear to the next
signal.

On Tue, 14 Nov 2006 11:54:39 -0000, MaxB wrote:

Why does the signal at the country end of the down Central Line at
Stratford
have Red, WHITE and Green aspects? It wasn't just a faded yellow!

Possibly a tripcock tester?
http://www.trainweb.org/tubeprune/Si...os.htm#Fig%203

The tester is usualy next to the track 3/4 of the way along the platform,
with the white light next to the starting signal.

--
Fig

Fig wrote:
Possibly a tripcock tester?
http://www.trainweb.org/tubeprune/Si...photos.htm#Fig 3

The tester is usualy next to the track 3/4 of the way along the platform,
with the white light next to the starting signal.

That was my first though when I read the question. Tripcock tester
lights are often purple, but they are also white at times. The only
other option I can think of off the top of my head is its a platform
reverser signal, which indicates to the driver he is to turn on the
platform.

wrote in message
oups.com...

MaxB wrote:
Why does the signal at the country end of the down Central Line at
Stratford
have Red, WHITE and Green aspects? It wasn't just a faded yellow!

It's part of the Automatic Train Protection/Control system. There
isn't a signal at the entrance to every block, trains being controlled
by codes transmitted in the blocks. Where signals are retained, a
green aspect indicated that all blocks up to the next signal are
transmitting a proceed code. A white light indicates that a proceed
code is being transmitted, but not by all blocks to the next signal.
Red means stop (proceed code not being transmitted).

It wasn't appropriate to use yellow, as on traditional signalling
systems that would indicate to the driver that he was clear to the next
signal.


Definitely the running signals, so I am sure this is the correct
explanation. Thanks.

MaxB

"Fig" wrote in message newsp.tiz9qurwm4iaeb@dell...
On Tue, 14 Nov 2006 11:54:39 -0000, MaxB wrote:

Why does the signal at the country end of the down Central Line at
Stratford
have Red, WHITE and Green aspects? It wasn't just a faded yellow!

Possibly a tripcock tester?
http://www.trainweb.org/tubeprune/Si...os.htm#Fig%203

The tester is usualy next to the track 3/4 of the way along the platform,
with the white light next to the starting signal.

--
Fig
It may be worth pointing out that there are no tripcocks on the central line
(or the vic line).
Andy

wrote:
It wasn't appropriate to use yellow, as on traditional signalling
systems that would indicate to the driver that he was clear to the next
signal.

They should have chosen something other than white though. If theres
any colour that could be confused at a distance with lots of other
normal
lights nearby its a white. What was wrong with blue or purple for
example?

B2003

Boltar wrote:

wrote:
It wasn't appropriate to use yellow, as on traditional signalling
systems that would indicate to the driver that he was clear to the next
signal.

They should have chosen something other than white though. If theres
any colour that could be confused at a distance with lots of other
normal
lights nearby its a white. What was wrong with blue or purple for
example?

Nothing. In fac rumour has it that the white aspects are going to be
replaced with blue aspects, to match the blue aspects to be used on the
VLU signalling.

TheOneKEA wrote:
Boltar wrote:

wrote:
It wasn't appropriate to use yellow, as on traditional signalling
systems that would indicate to the driver that he was clear to the
next signal.

They should have chosen something other than white though. If theres
any colour that could be confused at a distance with lots of other
normal lights nearby its a white.

One would have thought so, but I think you'll find that white signals are
already used on tram systems, e.g. Croydon and Bordeaux to my knowledge.
Presumably the potential confusion has been investigated and found to be not
a problem in practice.

What was wrong with blue or purple
for example?

Nothing. In fac rumour has it that the white aspects are going to be
replaced with blue aspects, to match the blue aspects to be used on
the VLU signalling.

VLU?

--
Richard J.
(to email me, swap 'uk' and 'yon' in address)