wrote:
Are the signals that are normally found on the upper left side of the
tunnel entrances at Victoria line stations actually starter signals
or are they platform repeaters? I notice that the stations do not
appear to have track-level starters, execpt for areas where there are
points, such as at Victoria.

I realise that the various equipments differ, but I it seems that
signal aspects on the Victoria line are the same as those on the
Central line. These include a danger aspect, an aspect allowing
trains on code to proceed and a clear aspect for all trains.

In any event, I notice that many drivers on the Central and Victoria
lines prefer to wait until they get a full clear before closing up
and proceeding, although some will depart when the signal indicated
clear for coded trains. Why is that?

The platform headwall corner signals are "true" starters. A Vic line train
running in usual ATO mode will not normally pass a red signal (white aspect
shown when an ATO train can pass, but train in manual cannot). The same
thing is true where signals are ptrovided away from stations (usually
confliction point protection or where there are more than one route from the
signal). Headway posts are not intended to be stopped at by non ATO trains.

The corner signals realy become significant in degraded mode where manual
driving is necessary or if non ATO equipped works trains are running on the
line outside a possession (not sure if that is still allowed).

The existing Vic line signalling (due for replacement in the near future)
uses coded track circuits with a very restricted number of codes (3 running
codes for 2 train running speeds and 1 "code" only identified as part of the
signalling system).

Being pedantic the Vic Line mixes ATO with ATP (automatic train
protection) - the latter is, in very broad terms, the auto equivalent of
the fail safe signalling system.

Peter
--
Peter & Elizabeth Corser
Leighton Buzzard, UK

"Peter Corser" wrote in message
...

The platform headwall corner signals are "true" starters. A Vic line
train running in usual ATO mode will not normally pass a red signal (white
aspect shown when an ATO train can pass, but train in manual cannot).

I was referring to the white aspect in my earlier post, not the red one. I
was wondering why some drivers chose to hold at a station, even if they have
a white aspect.

The same thing is true where signals are ptrovided away from stations
(usually confliction point protection or where there are more than one
route from the signal). Headway posts are not intended to be stopped at
by non ATO trains.

What is a headway post?

On Thu, 23 Aug 2007 21:28:49 GMT, wrote:

The platform headwall corner signals are "true" starters. A Vic line
train running in usual ATO mode will not normally pass a red signal (white
aspect shown when an ATO train can pass, but train in manual cannot).

I was referring to the white aspect in my earlier post, not the red one. I
was wondering why some drivers chose to hold at a station, even if they have
a white aspect.

Because they're driving in manual?

"asdf" wrote in message
...
On Thu, 23 Aug 2007 21:28:49 GMT, wrote:

The platform headwall corner signals are "true" starters. A Vic line
train running in usual ATO mode will not normally pass a red signal
(white
aspect shown when an ATO train can pass, but train in manual cannot).

I was referring to the white aspect in my earlier post, not the red one. I
was wondering why some drivers chose to hold at a station, even if they
have
a white aspect.

Because they're driving in manual?

I've seen them driving in ATO and holding even when they have a white
aspect, at least on the Central line.

Even if they are driving in manual they would have to be on code, and even
then they would be able to proceed on a white aspect.

wrote:
"Peter Corser" wrote in message
...

The platform headwall corner signals are "true" starters. A Vic line
train running in usual ATO mode will not normally pass a red signal
(white aspect shown when an ATO train can pass, but train in manual
cannot).

I was referring to the white aspect in my earlier post, not the red
one. I was wondering why some drivers chose to hold at a station,
even if they have a white aspect.

The same thing is true where signals are ptrovided away from stations
(usually confliction point protection or where there are more than
one route from the signal). Headway posts are not intended to be
stopped at by non ATO trains.

What is a headway post?

The signal is part of the ATP function - it merely tells the driver that he
has the appropriate code and authority to pass that signal, not that he must
pass it. This is identical to a normal procede aspect in manual signalling.
ATO and ATP functions are not fully separated as is usually done with
current systems.

Driver holding at white could be in manual, but may just be running early
(or realise that he is running too close to the one in front - holding at
white for a short period may mean that he can have an unchecked or better
run to the next station/s). If he is running early he will only be held for
time at the next controlled signal site (signals clear on route and time,
among other factors).

Headway posts were installed in the Vic as a means of informing a driver
that he had been stopped in ATO/ATP due to the train in front. These were
the equivalent of intermediate and home signals, but a genuine signal was
only installed where there was a routing consideration. A non ATO/ATP train
could not be signalled to approach a headway post and be stopped at it.

AFAIR the white aspect came up on the corner signal as soon as a 270 code
(medium speed, but allowed remotoring) was available to the train in the
platform. The green was a genuine LUL green - only allowed once the
preceding train had cleared an "overlap" on the next signal (it wasn't
called an overlap, but fulfilled the same function). The codes were 420
pulses per minute = full speed allowed, 270 + medium speed with motoring,
180 = medium speed coasting only, 0 = only used by signalling system.

The station stop was achieved by an initial braking spot followed by a
sequence of spots with the speeds mimicking the braking curve to rest in the
platform. ISTR that the sequence was set in 5 mph steps with the spot
frequency indicating the allowed speed - there were three brake rates with
the braking curve assuming that the "normal" middle rate would be OK. The
only way to easy adjust the curve was reposition a spot (and there was much
fine tuning in the early days).

Peter
--
Peter & Elizabeth Corser
Leighton Buzzard, UK

In article , Peter Corser
writes
AFAIR the white aspect came up on the corner signal as soon as a 270 code
(medium speed, but allowed remotoring) was available to the train in the
platform. The green was a genuine LUL green - only allowed once the
preceding train had cleared an "overlap" on the next signal

No. From memory the signal shows white when the line is clear to the
next headway post plus overlap and green when it is clear to the next
signal plus overlap. A station starting point would only produce a 420
code, not a 270 - 270 allows restarting at a signal stop but not from a
station. White would only be displayed with a 420 code.

The codes were 420
pulses per minute = full speed allowed, 270 + medium speed with motoring,
180 = medium speed coasting only, 0 = only used by signalling system.

120, not 0.

--
Clive D.W. Feather | Home:
Tel: +44 20 8495 6138 (work) | Web: http://www.davros.org
Fax: +44 870 051 9937 | Work:
Please reply to the Reply-To address, which is: