Re: Fast / Slow Line Layout

On Thu, 17 Jul 2008 11:14:53 +0100 someone who may be
"news.btinternet.com" <Jabberwocky@xxxxxxxxxx> wrote this:-

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.

That it has happened over time is part of the reason, but not the
only part.

Part of the reason is that some railway companies preferred, all
other things being equal, to pair lines by direction, others liked
to pair them by function.

Lines paired by direction mean that moving from one to the other
does not involve crossing another line. This has an obvious
advantage if trains are being sent from one line to the other, but
at flat junctions a train may have to cross all other lines to make
the move. Lines paired by direction also means that small stations
are simpler, just two side platforms typically and they can be added
more easily by just putting the platforms on the outside.
Interchange between trains in the same direction can easily be
arranged by having an island platform between the lines.

Lines paired by function make moving between lines more complicated,
as it involves crossing another line. On the other hand flat
junctions are easier.

Neither arrangement is perfect, but in a particular set of
circumstances one may well be better. For example the Northampton
loop and junctions are Reading and Didcot are examples where lines
paired by function are better. Many lines with suburban services
show the advantages of lines paired by direction, for example the
ones from Finsbury Park northwards. Where circumstances change then
the sensible approach is a flying junction/flyover to sort things
out without conflict, for example Windmill Bridge and Wimbledon.



--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54
.

Relevant Pages

  • Re: Future of MFC?
    ... reason to not use .Net. ... for native code development, and with tools that were as good as those ... If those things matter to you you won't be interested in MFC, ... pretty-much a rarity on non-Windows platforms (and can't be guaranteed ...
    (microsoft.public.vc.mfc)
  • Re: Why are z/OS people reluctant to use z/OS UNIX?
    ... offend anyone's sensibilities (I'm an avid mainframe guy, ... The thing is, most new applications, features, platforms, et al, are fraught ... One reason that Linux exploded onto the scene is that it has a user ... I firmly believe that if IBM would ...
    (bit.listserv.ibm-main)
  • Re: OT: Impatient driver assists in suicide bid.
    ... cyclists tend to be helpful and decent, based on a statistical sample ... and it *is* selfish to hold up traffic (or trains) by attempting ...  I'm not excusing the actions of the attempted murderer (the ... traffic or trains for whatever reason are fuckwits. ...
    (uk.rec.cycling)
  • Re: Night Trains to Brighton
    ... late trains DON'T run either! ... Not the least problem about Brighton is the intensively used double track ... to the journey - I wouldn't be surprised if maintaining track like this ... there wasn't an advertised Haywards Heath call for this reason. ...
    (uk.railway)
  • Re: FGW class 67 diagram from 18 May
    ... TPWS reduced the risks associated with Mk1 lack of crashworthiness 'as low ... why the hell was BR still building mk1-based trains ... reason why they went so soon? ... the only slam-door commuter trains left, ...
    (uk.railway)