Fast / Slow Line Layout

May be a silly question, but why are fast and low lines laid out as they
are.

What I mean is this, on some routes the layout seems to be Up Slow, Up fast,
Down Fast, Down Slow,
but on other routes it more like Up Slow, Down Slow, Up Fast, Down Fast.

Is there a reason for the difference, or is it just one of those things that
has happened over time.

Just curious,

J

I would be inclined to say it depends on the relative length of the
line.

If for example, the length of quadruple track is relatively short, and
it ends in a terminus, trains coming in on the slow lines will most
likely go out on the slow lines, and ditto for fast lines, so grouping
by speed helps reduce on conflicting movement and so boosts the
overall throughput of the layout.

Sorting by direction makes more sense for longer lines, however, as
the switching of trains between fast and slow lines can be acheived
without having to cross other lines. Again, this has repercussions on
line capacity and service punctuality.

Of course these problems can also be solved by flyovers but these
require considerable capital investment, which is probably only
warranted when none of the alternatives are acceptable.

"Graeme Wall" wrote
> Historically the companies had different ideas on how it should be done,
> the
> GWR went for paired by use, the LSWR went for paired by direction for
> example. Both methods have advantages and disadvantages. The GW version
> allowed for cheap stations with a single island platform serving the slow
> lines only at intermediate stations, the LSWR system allowed for cross
> platform interchange between fast and slow services at key points such as
> Woking and Basingstoke.

Except that they put the platforms in the wrong places at those two
locations, so cross-platform interchange between fast and slow can't happen.

<amogles@yahoo.com> wrote in message
news:56ee2957-8218-4784-a0c5-d71390b1211e@z66g2000hsc.************.com...
>
> I would be inclined to say it depends on the relative length of the
> line.
>
> If for example, the length of quadruple track is relatively short, and
> it ends in a terminus, trains coming in on the slow lines will most
> likely go out on the slow lines, and ditto for fast lines, so grouping
> by speed helps reduce on conflicting movement and so boosts the
> overall throughput of the layout.
>
> Sorting by direction makes more sense for longer lines, however, as
> the switching of trains between fast and slow lines can be acheived
> without having to cross other lines. Again, this has repercussions on
> line capacity and service punctuality.

On the SWML the practical advantages of pairing by direction allows semi
fast trains to cross easily to the slow (platform) lines for station calls,
limited stop trains can run partially on the fast lines, and slow trains can
be repathed fast line to make up time and overtake if running late.

Of course the LSWR provided a flyover at nearly every junction as well, the
most obvious problem being the lack of a flyover at Woking, the flat
junction there apparently constrains the whole mainline timetable.

Not so good for line closures for maintenance though.

Paul

John Salmon wrote:
> "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 by use at the terminus but then use a
>> single-track flyover (at Belle Isle and Wimbledon respectively) to
>> switch the lines around and run paired by direction along the main
>> line. The lines out of Manchester Piccadilly do the same, switching at
>> Slade Green.
>
> Slade *Lane*.
>

.... and what a shame there is no flyover there!

Charlie

"John F Kappler" <john@pceffect.co.uk> wrote in message
news:9mcu741kv8641vrpl5ts6nq7r7f3h8ae18@********...
> Of course on the GW they're not Fast and Slow, they are Main and
> Relief.......
>
> Sorry to be pedantic...........

that's why I put 'fast' in inverted commas when I was referring to the
Windsor branch. It's usually me that's pedantic about use of Main and Relief
on the GWML (and sometimes I even insist on Through and Local on the
Southern).

Peter

"Clive D. W. Feather" <clive@on-the-train.demon.co.uk> 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 by use at the terminus but then use a single-track
> flyover (at Belle Isle and Wimbledon respectively) to switch the lines
> around and run paired by direction along the main line.

The Belle Isle flyover was, until the 1970s, only used to access the goods
yard, and all passenger trains had to cross everything else in the station
throat (though suburban trains could go down to Moorgate via the Widened
Lines to avoid conflicts with expresses). The Wimbledon flyover was only
built in the 1930s, and before that fast and slow trains for the SWML had to
be sorted out in the Waterloo throat.
>
> 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).

Peter

On 17 Jul., 13:54, John F Kappler <j...@pceffect.co.uk> wrote:
> Of course on the GW they're not Fast and Slow, they are Main and
> Relief.......
>
> Sorry to be pedantic...........

The OS maps even have them labelled as such.

Did the OS people borrow the vocabulary of the railway concerned, or
were/are all maps labelled in a uniform way?

Andrew

In article <431247c04f%Rail@greywall.demon.co.uk>,
Graeme Wall <Rail@greywall.demon.co.uk> wrote:

> In message <tmr88jrp7n00.yzx4cobed7a4.dlg@40tude.net>
> Chris Tolley <cjt.7@supanet.com> wrote:
>
>
> >
> > IRL, of course, things are rarely as black and white as that, so the
> > layout will be designed to optimise the number of conflicting movements,
> > which is one reason why rail layouts are sometimes redesigned when
> > service patterns change.
> >
>
> While I'm sure we all suspect there are layouts specifically designed to
> optimise conflicting movements the intention is usually to minimise them :-)

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

Sam

On 17 Jul, 14:28, Sam Wilson <Sam.Wil...@ed.ac.uk> wrote:
> In article <431247c04f%R...@greywall.demon.co.uk>,
>  Graeme Wall <R...@greywall.demon.co.uk> wrote:
>
> > In message <tmr88jrp7n00.yzx4cobed7a4....@40tude.net>
> >           Chris  Tolley <cj...@supanet.com> wrote:
>
> > > IRL, of course, things are rarely as black and white as that, so the
> > > layout will be designed to optimise the number of conflicting movements,
> > > which is one reason why rail layouts are sometimes redesigned when
> > > service patterns change.
>
> > While I'm sure we all suspect there are layouts specifically designed to
> > optimise conflicting movements the intention is usually to minimise them :-)
>
> The pedant in me has to point out that "optimise" does not necessarily
> mean "maximise"...  :-)
>
> Sam

What nobody has pointed out yet is that when a main line is built as a
2-track railway and then widened to a 4-track (as happened on the
Great Western, for example), pairing by use is much easier than
pairing by direction.

Rob.