On Mon, 6 Aug 2007, Mr Thant wrote:

On Aug 6, 4:46 pm, "Clive D. W. Feather" cl...@on-the-
train.demon.co.uk wrote:

Obviously you want access off the flyover, and that will require use of
the headshunt. But why force the double reverse on anything coming out
of the south side of Paddy?

The layout at Shenfield is equally curious:
http://www.rail-reg.gov.uk/upload/pd...le_line_GE.pdf

Why is the Southend down diveunder connected solely to the Crossrail
up platform?

It's not - look at the colours again; Crossrail only uses the northernmost
island, via the existing track to the south of it (in orange), plus a new
stub on the north side (in red). The down Southend is accessed from the
blue and black track which runs past the north side of the middle island.

Furthermore, if you look at the mess of pointwork to the west, it looks
like there's a way to get trains from the slows to the Crossrail platform
without conflicting with moves from the fasts to the non-Crossrail
platforms: trains coming in on the down slow take the westernmost slip
linking that line to the new loop that leads into the new northern
terminating track; leaving, they take the slip onto the current down slow
(resignalled for up trains), and then the westernmost new slip linking the
current up and down slows. That would mean no Crossrail train ever runs on
the current up slow east of the westernmost new slip, and so trains coming
along the down fast and bound for Southend can use this, reached via the
new slip linking the down fast to the current up slow, to get to the
middle island and the down Southend. The odd thing is that you can't reach
the southern face of the northern island that way: there would have to be
a crossover in place of the slip that leads from the current down slow to
the new Crossrail terminating track. This only creates conflict between
Crossrail trains arriving into the southern platform and those departing
the northern platform, though; there's no conflict with trains on the
fasts. If enough things are bidirectionally signalled, then such a
conflict could be smoothed over by working the departing train into the
new loop, passing the arriving train on the wrong side, then reaching the
up slow via two slips (one new, one old) in rapid succession. If there was
another train arriving at that point, it would hit it, but there won't be.

Also, no crossovers are shown in the central section:
http://www.rail-reg.gov.uk/upload/pd...central_SE.pdf

That seems like a really bad idea. Any problem in the tunnel means
reversing everything at the portals.

tom

--
OK, mostly because of Tom, but not only because of his bloody irritating
character and songs.