On Thu, 27 Mar 2008, Andy wrote:

On Mar 27, 11:59*pm, Tom Anderson wrote:
On Wed, 26 Mar 2008, Andy wrote:
On Mar 26, 6:53*pm, Tom Anderson wrote:
On Tue, 25 Mar 2008, Mr Thant wrote:
On 25 Mar, 23:49, Tom Anderson wrote:

True. All of which could be done without the tunnel, for a fraction of the
price.

And without increasing any capacity from the termini to where people
work/shop/go out/etc, which is the whole point of the current iteration
of the project.

Entirely agreed. But the point i was making in the text that's been
snipped is that the Crossrail project doesn't deliver significant
increases in capacity outside central London, and none that couldn't be
provided much more cheaply.

But it is the central London section that needs the capacity, as the
Underground can not distribute passengers arriving from the mainline.
How much cheaper would it be to provide the extra capacity across London
without the joining the lines to the west and east? Passengers taken
off, for example, the Central line at Liverpool Street / Stratford will
give more capacity for passengers from the West Anglia lines.

Absolutely. Sorry that i haven't really made myself clear about all this -
i think Crossrail's a good idea (although not as good an idea as some
other options which were dismissed - but that's another story), i just
think it's misleading to say it'll increase capacity on the lines it's
assimilating.

But can we agree that it will provide extra capacity at the terminii
where the current trains will be removed? On top of any possible
increase in the lines that it serves directly.

Yes.

But i'm still going to maintain that it's capacity that can't be used,
because the bottleneck is not the terminal capacity!

Unless you mean capacity for passengers rather than trains, in which case
you're quite right.

Again, could be done without the tunnel.

And where do you plan to build the extra platforms at Paddington and
Liverpool Street?

Liverpool Street isn't limited by platform capacity, it's limited by
capacity through the station throat. Rebuilding that is entirely
possible, although of course not trivial. I don't know about
Paddington, i have to confess. But since all we're talking about is
lengthening trains, why do we need more platforms?

Paddington has at least three platforms that are of limited length
(12-14, plus 11 which shares the country end track with the entrance to
platform 12). If you lengthen the trains to 8 or 10 coaches, I don't
think that any of these platforms can cope. Liverpool Street also
suffers from some of the same problems, with platforms 16-18 limited to
8 coaches. At both locations, the trains serving these platforms will be
the ones sent down the crossrail tunnels.

Right. Problems which could be solved without recourse to a tunnel.

But at what proportion of the cost?

At what proportion of umpty-billion pounds? A pretty small one.

To add a double track railway junction at each end of the Crossrail
tunnels is considerable easier than fitting extra platforms / new
layouts into the existing sites. The junctions can be placed where there
is room without the expense of buying the land etc. You only need to
look at the costs that seem to be involved in adding just one platform
at King's Cross. The point is that the extra capacity is needed in
central London and this can only be provided by building a tunnel.

The capacity increase is going to come from longer, not more, trains.
Extra platforms or whatever would not be needed; existing ones would need
to be extended. This is not free, but it's also not expensive, at least on
the Crossrail scheme of things.

I would certainly agree that if you are going to build a
cross-central-London tunnel, you should connect it to some routes outside
the centre, though. I'm not arguing for a Paddington-to-Liverpool Street
mini-Crossrail. I'm just saying that the capacity increase outside the
centre of London will be small, and nothing that couldn't be achieved much
more cheaply without Crossrail.

tom

--
Change happens with ball-flattening speed. -- Thomas Edison