In message
,
lonelytraveller writes

On 26 May, 07:18, Paul Terry wrote:
It's not deep enough

Deep enough for what?

Deep enough to avoid all of the sub-surface structures (foundations,
tube tunnels, etc) that are in the way of Crossrail. The tiny Post
Office railway was able to skirt round these, but that's not possible
for Crossrail (see below) - and, of course, there are many more tall
buildings now than there were when the P.O. railway was built.

the Post Office Railway doesn't have a straight enough alignment - it runs
north of Oxford Street, curving up to Wimpole Street and then coming
back south before the big loop up to Mount Pleasant.

Straight enough for what?

Ten-carriage trains of mainline proportions travelling at up to 100kph
through the tunnels.

The curves are fairly gentle, even though
the tube itself copes with curves like those at Shepherd's Bush, and
the PO railway is close enough to oxford street at all the stations.

Yes, but Crossrail is nothing like a tube line - it is for mainline
services travelling at nearly three times the speed of tube trains in
the tunnels (and up to 160kph on the surface sections).

It doesn't need to hug oxford street when its not at a station, not
that the current Crossrail's Hanover Square and Dean Street Stations
are on Oxford Street either.

No, it doesn't need to hug Oxford Street (in fact, it runs slightly
south of the Central line), but it does have to be relatively straight
to achieve the anticipated speeds. Incidentally, there's no station at
Hanover Square - it is simply the eastern ticket hall for Bond Street
station, which gives some idea of the scale of the project. Similarly,
the works at Dean Street are for the western ticket hall of Tottenham
Court Road station (the eastern end being just in front of Centre
Point).

As for the loop at mount pleasant, its a comparatively small thing to
dig a new bypass around the loop than it is to dig an entirely new
route across the whole of london. Besides, mount pleasant /
clerkenwell / essex market could do with a tube station, the met and
thameslink lines run through it but don't stop.

Crossrail is not really comparable with a tube service, though.
--
Paul Terry