DistrictDriver wrote:

Basically, any of the services via Edgware Road would have to be C
stock, as the D stocks are too long to fit in the platforms (and I
believe they scrape the platforms!). I think there's also a
restriction on C stocks going any further east than Barking, although
I'm not sure of the reasons.

UIVMM it's because C stock can't go as fast as D stock, so would cause
delays.

Aidan Stanger wrote:
DistrictDriver wrote:

Basically, any of the services via Edgware Road would have to be C
stock, as the D stocks are too long to fit in the platforms (and I
believe they scrape the platforms!). I think there's also a
restriction on C stocks going any further east than Barking,
although
I'm not sure of the reasons.

UIVMM it's because C stock can't go as fast as D stock, so would
cause
delays.

I always thought it was a gauging issue at Dagenham East - some part of
the C stock kept getting smacked by a platform edging stone or railing.
I've seen C stock DMs with Upminster on their dest. blinds, so they've
definitely been there in the past.

On 13 Feb 2005, TheOneKEA wrote:

Aidan Stanger wrote:
DistrictDriver wrote:

Basically, any of the services via Edgware Road would have to be C
stock, as the D stocks are too long to fit in the platforms (and I
believe they scrape the platforms!). I think there's also a
restriction on C stocks going any further east than Barking,
although I'm not sure of the reasons.

UIVMM it's because C stock can't go as fast as D stock, so would cause
delays.

I always thought it was a gauging issue at Dagenham East - some part of
the C stock kept getting smacked by a platform edging stone or railing.
I've seen C stock DMs with Upminster on their dest. blinds, so they've
definitely been there in the past.

We went over this a few weeks ago (search for "dull questions about
loading gauge"): once upon a time, there were speed restrictions on C
stock out there, due to some sort of gauge business. However, (a) trains
would have to slow down for the station starter anyway (no idea what that
means!) and (b) the business is now taken care of.

No idea about the speed thing, though. A stock to Upminster, is what i
say!

tom

--
Restate my assumptions

Tom Anderson wrote:

We went over this a few weeks ago (search for "dull questions about
loading gauge"): once upon a time, there were speed restrictions on C
stock out there, due to some sort of gauge business. However, (a)
trains would have to slow down for the station starter anyway (no
idea what that means!) and (b) the business is now taken care of.

(a) is probably in reference to an approach-released station starter;
in a controlled area like Dagenham East (FG), the interlocking is
probably designed to clear the relevant starter after the platform
track circuit has been occupied for a short period. In an auto area, a
timer circuit is used.

In article ,
Tom Anderson writes
However, (a) trains
would have to slow down for the station starter anyway (no idea what that
means!)

The station starter is the signal at the departure end of the platform;
while it is red, the train can't (legally) start away.

On LU the signalling is designed on the assumption that all trains will
be stopping at every station[*]. If a train runs through a station at
speed and passes a red signal, it is possible that the trip stops will
not stop it in time to prevent an accident [+]. Therefore drivers are
instructed to slow to 5mph (or in some places 10mph) when running
non-stop through a station.
[*] There are some specific exceptions, such as Turnham Green on the
Piccadilly, and the signalling in these places is altered accordingly.

[+] In general, a signal can only turn green if a train hitting the
train stop of the following red signal *at line speed* will be stopped
before the point of actual danger (e.g. another train). Designing for
the maximum possible speed of all trains would be unduly restrictive, so
designing to the speed limit of the line is a sensible compromise.

--
Clive D.W. Feather | Home:
Tel: +44 20 8495 6138 (work) | Web: http://www.davros.org
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Clive D. W. Feather wrote:

[*] There are some specific exceptions, such as Turnham Green
on the Piccadilly, and the signalling in these places is altered
accordingly.

In the case of Turnham Green, both lines do have home signals - the EB
line's homes are A631^A and A631^B, and the WB's are A630^A and A630^B.
Would the overlaps on these homes simply be longer than usual, to allow
a train to alternately stop or pass through at linespeed?


[+] In general, a signal can only turn green if a train hitting the
train stop of the following red signal *at line speed* will be
stopped before the point of actual danger (e.g. another train).
Designing for the maximum possible speed of all trains would be
unduly restrictive, so designing to the speed limit of the line is
a sensible compromise.


This doesn't make much sense. Are you saying that if a train passes a
red signal at linespeed or higher and gets tripped, the signal in rear
could change to green if the entire train manages to exit that signal's
overlap?

TheOneKEA wrote:
Clive D. W. Feather wrote:
snip
[+] In general, a signal can only turn green if a train hitting the
train stop of the following red signal *at line speed* will be
stopped before the point of actual danger (e.g. another train).
Designing for the maximum possible speed of all trains would be
unduly restrictive, so designing to the speed limit of the line is
a sensible compromise.


This doesn't make much sense. Are you saying that if a train passes a
red signal at linespeed or higher and gets tripped, the signal in rear
could change to green if the entire train manages to exit that
signal's overlap?

A signal is controlled by all the track circuits between it and the end of
the next signal's overlap. Therefore a signal will show red whilst there is
an occupied track circuit either between it and the next signal or in the
next signal's overlap.


--
Cheers for now,

John from Harrow, Middx

remove spamnocars to reply

In article . com,
TheOneKEA writes
[*] There are some specific exceptions, such as Turnham Green
on the Piccadilly, and the signalling in these places is altered
accordingly.
In the case of Turnham Green, both lines do have home signals - the EB
line's homes are A631^A and A631^B, and the WB's are A630^A and A630^B.
Would the overlaps on these homes simply be longer than usual, to allow
a train to alternately stop or pass through at linespeed?

Yes. Just as with a signal between stations. The overriding principle is
that a train stop hit at line speed should stop the train before the
point of danger.

[+] In general, a signal can only turn green if a train hitting the
train stop of the following red signal *at line speed* will be
stopped before the point of actual danger (e.g. another train).

This doesn't make much sense. Are you saying that if a train passes a
red signal at linespeed or higher and gets tripped, the signal in rear
could change to green if the entire train manages to exit that signal's
overlap?

Yes. But, in that case, the situation will still be protected. Um, let's
see:

|-O 1 |-O 2 |-O 3 |-O 4 |-O 5
-+---A---+---B---+---C---+---D---+---E---+---F---+---G---+---H---+---I-

Let's assume that braking distance from line speed is 1.4 times the
signal spacing. So:

1 is red if A, B, C, D, or E is occupied
2 is red if C, D, E, F, or G is occupied
3 is red if E, F, G, H, or I is occupied

etc. Suppose there's an obstruction at F. Signal 3 will be red because
it's within its block. Signal 2 will be red because a train tripped at
signal 3 won't stop until somewhere in G. Signal 1 can be green because
a train tripped at signal 2 from line speed will stop somewhere in E.

Now suppose a train runs past signal 1 at well over line speed and hits
the trip at signal 2. Signal 1 will be red at this point because the
train is occupying B and C. The train brakes but, because it was
speeding, it doesn't stop until somewhere in F. As the rear of the train
passes the E-F boundary signal 1 will revert to green *but* the
situation is still protected by signal 2 at red.

Clear? Or have I answered the wrong question?

--
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:

Clive D. W. Feather wrote:
In article . com,
TheOneKEA writes
In the case of Turnham Green, both lines do have home signals - the
EB line's homes are A631^A and A631^B, and the WB's are A630^A and
A630^B. Would the overlaps on these homes simply be longer than
usual, to allow a train to alternately stop or pass through at
linespeed?

Yes. Just as with a signal between stations. The overriding
principle is that a train stop hit at line speed should stop the
train before the point of danger.

Thanks, that was what I thought.

This doesn't make much sense. Are you saying that if a train passes
a red signal at linespeed or higher and gets tripped, the signal in
rear could change to green if the entire train manages to exit that
signal's overlap?

Yes. But, in that case, the situation will still be protected. Um,
let's see:

snip

Clear? Or have I answered the wrong question?

I understand now. But it doesn't seem sensible to place the signals
that close together, or only hold one signal in rear of the signal
protecting an obstruction at danger.

In message . com,
TheOneKEA writes

[*] There are some specific exceptions, such as Turnham Green
on the Piccadilly, and the signalling in these places is altered
accordingly.

In the case of Turnham Green, both lines do have home signals - the EB
line's homes are A631^A and A631^B, and the WB's are A630^A and A630^B.
Would the overlaps on these homes simply be longer than usual, to allow
a train to alternately stop or pass through at linespeed?

Yes. A Non-stopping Picc train doesn't have any speed restriction on
the fast lines through Turnham Green.

The normal 'rule' is 5 mph at a station starter. However, if we (the
Picc) are run down the local (District) line from Acton to Hammersmith,
we can pass the starters at 25 mph., so there must be some adjustments
of the overlaps there too.
--
Steve Fitzgerald has now left the building.
You will find him in London's Docklands, E16, UK
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