On Thu, 4 Dec 2008, Andrew Heenan wrote:

"Tom Anderson" wrote...
So how were you able to determine that Shenfield was such a bad terminus?
That's the bit i can't work out.

Well, I've explained about 15 times, including in the post you replied to,
but I'm happy to try again.

No, you haven't explained it once. You still don't here. Read the question
again: how can you judge Shenfield to be the wrong terminus, when you
can't judge any other option?

I happen to believe that planning multi-billion pound investments of
taxpayers money (plus about 0.005% added by 'business') should be based on
positive reasons, rather than convenience.

But there's gaping hole in the list of reasons for Crossrail *to* go there.
Other than convenience.

If we use the word 'feasibility' rather than 'convenience', does that make
things any clearer?

And even the convenience arguments are flawed. Crossrail does not *have*
to be an all-stopper; that was a preference of Ken's, who wanted
Crossrail to be a 'supa tube' for London; Thank God he did, because his
support was key in getting the thing accepted, and that's why he got his
way. But he's not the only political opportunist, and I can see poweful
arguments for some trains that stop at all central stations, but go fast
(or faster, at least) at the ends; Heathrow is one obvious example,
Cambridge would be another. Oxford another.

You're right, Crossrail doesn't have to be an all-stopper.

But what it does have to be is completely, or almost completely,
segregated from non-Crossrail lines. Without that, it becomes a recipe for
monstrous performance pollution between railways on different sides of
London - for instance, if it shared tracks with services on the Great
Eastern and West Coast routes, then problems at Milton Keynes could end up
disrupting services in Chelmsford. This would be a really bad idea.

In practice, this means that Crossrail gets to take over one pair of
tracks on one or two routes on each side of the core tunnel. Those could
be fast or slow pairs, making it an express or stopping service. It could
be one of each, even on the same route. But any more than that, and the
core tunnel won't be able to supply enough trains to provide an adequate
service on its own.

That means that if we want a service along the GEML and the tunnel to
Abbey Wood, then on the GEML, Crossrail can take over either the fast or
the slow lines, but not both, and it can't share both with Liverpool
Street trains. That just would not work in practice.

So, if you want to run stopping services on the GEML, you *can't* also run
fast services. You could run fast services instead, but not as well.

Now, you could indeed do that - and there was a competing proposal called
Superlink which never quite got off the ground, but would have run to
Cambridge, Ipswich and Southend in the east, with stops only at Liverpool
Street and Canary Wharf inside London. There's certainly a case to be made
for this - although there might be more tunnelling (there was in that
plan), there's less construction in built-up areas, and because fares are
higher, more revenue to pay for it.

But it seems that you want a service that does everything - fast trains,
slow trains, a panoply of branches, all presumably sharing with other
services. That just is not feasible.

tom

--
I'm angry, but not Milk and Cheese angry. -- Mike Froggatt