On Tue, 1 Aug 2006, Dave Arquati wrote:

Tom Anderson wrote:
On Tue, 1 Aug 2006, Dave Arquati wrote:

Bob wrote:

to turn round of half the trains at Paddington which seems a wasted
opportunity - taking over the Hammersmith end of the H&C removes a busy
junction on the Circle Line with knock on effects for that lines
reliability would seem a low cost no brainer.

I agree, but I think ensuring the central tunnel gets built is most
important - adding on too many extra bits here and there could kill the
whole project. Hammersmith could come later...

Except Hammersmith involves noodling about quite near the Paddington portal
(if you want to have a station at Royal Oak, or if you want to use the
existing H&C fly-under, at any rate), so if you don't at least build in the
possibility at the start, you might not be able to do it later.

I'm not sure it would be worth keeping Royal Oak in this scenario
(gasp). Its catchment area overlaps a lot with Bayswater, Warwick Avenue
and Paddington H&C; a western entrance for Paddington Crossrail would
also be close by.

Sort of. You're right, of course, about other stations being close by, but
neither Bayswater nor Warwick Avenue are stations which offer good routes
to the eastern end of central London (ie the City). Paddington H&C would
of course cease to exist if the H&C was transferred to Crossrail - unless
you're envisaging a very exotic configuration of the subsurface lines!
People could go to Paddington to catch Crossrail, but that involves
pushing local commuters through a busy mainline station. This western
entrance could make that fairly painless, though; i'm afraid i don't know
the details of that.

Nonetheless, there's still the fly-under to think about: it gets to ground
level ~50 m west of Lord Hill's Bridge, which is pretty much level with
the planned Crossrail portal, so there wouldn't be room for a
straightforward junction here; you'd need some sort of weird junction on a
slope thing. Realistically, if you want to use it, you either have to move
the portal east, or you have to leave room for a junction inside the box,
so the branch can run for a hundred metres or so at a bit below ground
level to link up with the fly-under. Or something - IANACivilEngineer.

An alternative would be to ditch it, and add a new fly-under/over around
Westbourne Park, rebuilding the station a little to the east; this would
have the advantage that the station would be upwards of the junction, and
so would be served by more trains. It might also enable some creative use
of the H&C platforms and tracks from Paddington to Westbourne Park by
mainline trains; suggestions on a postcard, please.

Or i suppose you could run the box into the fly-under, run all Crossrail
trains along the existing H&C track on the south side of the formation,
and do something at Westbourne Park to allow them to carry on west - build
a new pair on the south side beyond the junction if possible, or else on
the north side, as is planned, then either provide a fly-under/over to get
there, or put in crossovers to shuffle all the pairs north one position.
Hang on, i'll try some ascii art:

Key:

--- track
+ joining of track
X crossing of track
direction of train
### Westbourne Park platform
.... line heading off to Hammersmith
nU line label; mainlines 1-3 and Crossrail X, plus Up/Down

Now:

1U ------------------------------ 1U
1D ------------------------------ 1D
2U ------------------------------ 2U
2D ------------------------------ 2D
3U ------------------------------ 3U
3D ------------------------------ 3D
/--------------------- XU
### //--------------------- XD
XU ...------//
XD ...------/
###

New pair to the south:

1U ------------------------------ 1U
1D ------------------------------ 1D
2U ------------------------------ 2U
2D ------------------------------ 2D
3U ------------------------------ 3U
3D ------------------------------ 3D
XU -----------+------------------ XU
XD ----------X+---\ ### /-------- XD
XU ...------// \---/
XD ...------/

New pair to the north, with fly-under (flying tracks not shown):

XU -----)
XD ----)
1U ------------------------------ 1U
1D ------------------------------ 1D
2U ------------------------------ 2U
2D ------------------------------ 2D
3U ------------------------------ 3U
3D ------------------------------ 3D
(-+------------- XU
(-X+---\ ### /--- XD
XU ...----------// \---/
XD ...----------/

New pair to the north, with shuffle:

1U -------------\
1D -------------\\
2U ----------+---X+-------------- 1U
2D ----------+X---+-------------- 1D
3U -------+---X+----------------- 2U
3D -------+X---+----------------- 2D
XU ----+---X+-------------------- 3U
XD ----+X---+-------------------- 3D
\\---------+------------- XU
\--------X+---\ ### /--- XD
XU ...----------// \---/
XD ...----------/

I expect that's made things crystal clear to all!

Adding a new pair to the south is clearly best, but probably not possible;
the shuffle would then probably be the easiest, but might leave the lines
in the wrong place for things further down. The fly-under/over would get
everything right, but involves either a big bridge or three small ones -
and does mean that the Crossrail line would cross the formation three
times between Paddington and Heathrow, which is frankly silly.

tom

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