The post office railway goes from Paddington to Whitechapel with stops
at Oxford Circus, Rathbone Place, Mount Pleasant, and Liverpool
Street. It also passes along Oxford Street from the vicinity of Bond
Street.

The stop on Rathbone Place is very near the proposed Dean Street
"Western Ticket Hall" for the Tottenham Court Road station on
Crossrail.

Mount Pleasant is about 5 minutes walk from Farringdon, in the heart
of Clerkenwell, adjacent to the Thameslink and Circle/Met lines, in a
busy area which could do with a tube station.

The post office railway is disused.

Why didn't they just widen the tunnels and reuse them for Crossrail,
instead of digging hugely expensive new ones?

In message
,
lonelytraveller writes

The post office railway is disused.

Why didn't they just widen the tunnels and reuse them for Crossrail,
instead of digging hugely expensive new ones?

It's not deep enough - the Post Office Railway is on average 21m below
the surface, although the stations are virtually at basement level (and
so the tunnels also have steep 20% gradients either side of stations).
Crossrail in the central area is up to 36m below the surface. Also, 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.

It is a shame, though, that it hasn't been put to some good use since
its closure.
--
Paul Terry

"Paul Terry" wrote in message

In message
,
lonelytraveller writes

The post office railway is disused.

Why didn't they just widen the tunnels and reuse them for Crossrail,
instead of digging hugely expensive new ones?

It's not deep enough - the Post Office Railway is on average 21m below
the surface, although the stations are virtually at basement level
(and so the tunnels also have steep 20% gradients either side of
stations). Crossrail in the central area is up to 36m below the
surface. Also, 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.

Also, the big cost with Crossrail will be the huge stations more than
the tunnels. Re-using the PO railway would not help reduce this cost,
but would probably make it worse.

On Tue, May 25, 2010 at 04:51:32PM -0700, lonelytraveller wrote:

The post office railway is disused.

Why didn't they just widen the tunnels and reuse them for Crossrail,
instead of digging hugely expensive new ones?

The PO railway is such a small gauge (9' diameter tubes) that to widen
them would require almost as much work as boring new tunnels.

Also the stations are a lot shallower than the bulk of the tunnels, with
1:20 inclines either side which would be ... inconvenient.

--
David Cantrell | Godless Liberal Elitist

Hail Caesar! Those about to vi ^[ you!

On Wed, 26 May 2010 12:12:20 +0100
David Cantrell wrote:
On Tue, May 25, 2010 at 04:51:32PM -0700, lonelytraveller wrote:

The post office railway is disused.

Why didn't they just widen the tunnels and reuse them for Crossrail,
instead of digging hugely expensive new ones?

The PO railway is such a small gauge (9' diameter tubes) that to widen
them would require almost as much work as boring new tunnels.

Also the stations are a lot shallower than the bulk of the tunnels, with
1:20 inclines either side which would be ... inconvenient.

Sham about the PO railway. You'd think with the traffic problems in london
that any organisation would be falling over themselves to have their own
private tube system to transport their goods instead of relying on trucks
but I guess with the PO cost cutting comes before customer service.

B2003

On 26 May, 12:12, David Cantrell wrote:
On Tue, May 25, 2010 at 04:51:32PM -0700, lonelytraveller wrote:
The post office railway is disused.

Why didn't they just widen the tunnels and reuse them for Crossrail,
instead of digging hugely expensive new ones?

The PO railway is such a small gauge (9' diameter tubes) that to widen
them would require almost as much work as boring new tunnels.

Why? The main difficulty with tunnel boring is the lack of a line of
weakness to follow, and the lack of anywhere for spoil to spill into.
The PO railway is a line of weakness already made - a 9' diameter line
of weakness in fact - and a 9' diameter tube for the spoil to ease
itself into. There are even tracks to help remove the released spoil
by means of rail. Tunnel widening is a lot easier than tunnel boring.

Also the stations are a lot shallower than the bulk of the tunnels, with
1:20 inclines either side which would be ... inconvenient.

Only if you expand the bore from the same point all the way through.
If you expand it downwards at the stations, and upwards away from
them, the incline is significantly reduced.

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

the Post Office Railway is on average 21m below
The circle line is only on average around 9m below the surface, so the
PO railway is more than twice as deep.

the stations are virtually at basement level
That's hardly a bad thing. Less distance from the surface is greater
convenience for passengers trying to access it.

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? 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.
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.

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.

Only if you expand the bore from the same point all the way through.
If you expand it downwards at the stations, and upwards away from
them, the incline is significantly reduced.

And if you did that with steep enough gradients, you'd need EXTRA
powerful motors on lots of wheels for each and every train to escape
from the holes you've dug.
WHEREAS
If you make the line go up into the stations and down out of them, you
don't need to use the brakes and a quick push from the guard, sets the
train off and up to running speed as it accelerates away down the slope.

Jim

On Wed, 26 May 2010 04:56:23 -0700 (PDT)
lonelytraveller wrote:
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.

I would imagine that by the time you've stripped out all the tracks, cables
and tunnel lining so you can enlarge it you've probably spent more time and
money than you would if you just bored a new tunnel. Tunnels arn't dug with
picks and shovels any more - a TBM won't care if it has to dig the whole
tunnel itself or theres a small tunnel already there , it will take more or
less the same time. The only difference will be in the amount of spoil
needing to be carried away. Plus why inflict a windy route on a new
rail line when for high speed it needs to be as straight as possible.

B2003

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