Fast / Slow Line Layout

Sam Wilson wrote:

> The pedant in me has to point out that "optimise" does not necessarily
> mean "maximise"... :-)

Indeed, as any user of the NAg library will confirm: the optimisation
chapter is stuffed full of minimisation routines (E04FCF used to be
my best friend).

Cheers

mark-r

On Thu, 17 Jul 2008, Clive D. W. Feather wrote:

> The GER (Liverpool Street), the MR (St.Pancras), and the GWR (Paddington)
> went for paired by use. The GNR (King's Cross) and the LSWR (Waterloo) pair

The GER also swaps the pairs just south of Ilford with a flyover.
--
Chris Johns

"Chris Johns" <cmj@eh.org.invalid> wrote in message
news:Pine.LNX.4.64.0807171559250.2790@avalonia.loc al...
> On Thu, 17 Jul 2008, Clive D. W. Feather wrote:
>
>> The GER (Liverpool Street), the MR (St.Pancras), and the GWR (Paddington)
>> went for paired by use. The GNR (King's Cross) and the LSWR (Waterloo)
>> pair
>
> The GER also swaps the pairs just south of Ilford with a flyover.

Other than Slade Lane (already mentioned), the only place I can think of
where the pairing changes without the benefit of a flyover is Skelton Bridge
Junction, just north of York. Are there any others?

On 17 Jul, 13:48, "Clive D. W. Feather" <cl...@on-the-
train.demon.co.uk> wrote:

> Actually, the big issue was the triangle west of London Bridge, which
> was double track. The problem was that each leg was about the same size
> as the trains, so you couldn't hold trains on the triangle.
>
> [In fact, one signaller's mistake could result in a deadlock with three
> trains stopped because the rear of another one was fouling its route.]
>
Surely something which could be prevented with appropriately placed
signals and adequate locking.

On Jul 17, 12:01 pm, "Clive D. W. Feather" <cl...@on-the-
train.demon.co.uk> wrote:
<snip>
>
> Finally, the Metropolitan Line from Finchley Road to Harrow-on-the-Hill
> is arranged UF, US, DS, DF, UM, DM. The Marylebone pair are to one side
> for obvious reasons, but I'm not clear why they put the slows inside the
> fasts.

Possibly the slows came first and the fasts were added later, but
having the slows on the inside means just one island platform and one
set of access stairs is needed. I can't remember, though, if that's
what the arrangements are!

On Jul 17, 1:15 pm, "Peter Masson" <peter.mass...@privacy.net> wrote:
<snip>
> > Finally, the Metropolitan Line from Finchley Road to Harrow-on-the-Hill
> > is arranged UF, US, DS, DF, UM, DM. The Marylebone pair are to one side
> > for obvious reasons, but I'm not clear why they put the slows inside the
> > fasts.
>
> It has the advantage that Jubilee Line trains can be turned back at
> Willesden Green or Wembley Park by running them into a reversing siding
> between the Down and Up Slows (compare Welwyn Garden City, where a flyover
> had to be built to take terminating trains from the bay platforms on the
> Down Side to the Up Slow).

I'm sure the arrangement predates the Jubilee line by many years,
though if I remember correctly that's a renaming of part of the
Bakerloo line.

"John Salmon" <john.e.salmon@gensheet.com> wrote
>
> Other than Slade Lane (already mentioned), the only place I can think of
> where the pairing changes without the benefit of a flyover is Skelton
Bridge
> Junction, just north of York. Are there any others?
Harrow-on-the-Hill, at least for LUL trains (paired by direction from
Wembley Park and through the station, then paired by use on to Watford South
Junction. It's a bit more complicated, as the Chiltern Line from Marylebone
runs into the fast pair, while the Uxbridge branch leaves by a diveunder.

Effectively Colwich to Stafford, although there is only a double track
through Shugborough Tunnel.

I've lost track of the removal and reinstatement of the Relief Lines west of
Didcot, but effectively the GWML is paired by use east of Foxhall Junction,
but are or were paired by direction to the west.

AIUI something similar happens on the approach to Cardiff Central.

Peter

"Cats" <ramwater@uk2.net> wrote in message
news:215cd602-ec19-4c06-bcd4-f466a652d1eb@c58g2000hsc.************.com...
On Jul 17, 1:15 pm, "Peter Masson" <peter.mass...@privacy.net> wrote:
<snip>
>>
>> It has the advantage that Jubilee Line trains can be turned back at
>> Willesden Green or Wembley Park by running them into a reversing siding
>> between the Down and Up Slows (compare Welwyn Garden City, where a
flyover
>> had to be built to take terminating trains from the bay platforms on the
>> Down Side to the Up Slow).
>
>I'm sure the arrangement predates the Jubilee line by many years,
>though if I remember correctly that's a renaming of part of the
>Bakerloo line.

The Met lines were quadrupled between Finchley Road and Willesden Green
between 1913 and 1915, and on to Harrow in 1932. AIUI the arrangement with
the slow lines inside the fasts was intended to facilitate turning back of
short workings. The Stanmore branch was opened, as part of the Met, in 1932,
and the slow lines south of Wembley Park together with the Stanmore branch
were transferred to the Bakerloo in 1939, and then to the Jubilee in the
1970s.

Peter

I don’t think anyone’s mentioned yet that an important consideration
is the extent to which four tracks are being provided.

Paired by use doesn’t lend itself to sections of railway where, for
whatever reason, it is necessary to revert to just two tracks. One
immediately thinks of Hadley Wood Tunnel on the ECML paired by use, on
aproach to there, would be a nightmare

The LNWR is an interesting example of horses for courses.

Euston to Rugby is paired by use, as four tracks are available
throughout, yet the Trent Valley line north thereof is paired by
direction (believe will still be the case after upgrade), due to the
need to revert to just two tracks at various points.

Similarly, I believe the LNWR elected to pair by direction on the now
defunct four track sections of the North Wales main line for the same
reason.

allan tracy wrote:
> I don’t think anyone’s mentioned yet that an important consideration
> is the extent to which four tracks are being provided.
>
> Paired by use doesn’t lend itself to sections of railway where, for
> whatever reason, it is necessary to revert to just two tracks. One
> immediately thinks of Hadley Wood Tunnel on the ECML paired by use, on
> aproach to there, would be a nightmare
>
> The LNWR is an interesting example of horses for courses.
>
> Euston to Rugby is paired by use, as four tracks are available
> throughout, yet the Trent Valley line north thereof is paired by
> direction (believe will still be the case after upgrade), due to the
> need to revert to just two tracks at various points.

The new layout of the TV lines once through Rugby will be a little odd, in
that the lines will initially be DF, DS, UF, US, from south to north. The
down lines will switch over to DS, DF by virtue of the single track length
at Brinklow.

So if they ever get that big lottery win and four track that section,
they'll have to unknot the down lines, presumably a straightforward matter
once out of Rugby.

Paul