Dave Arquati wrote in message ...

Perhaps 1 in 4 passenger from Ebbsfleet, Grays, Basildon, Chelmesford,
Stansted will want to go beyond Liverpool St to Farringdon, TCR, Bond
Street and beyond. Therefore CrossRail should provide 1 in 4 of the
lines into Liverpool Street on each of these routes. That is, 4 tph,
with 12 tph terminating at Liverpool St.

This is logical thinking but there's a big flaw. At least to start off
with, the same number of passengers will still be using Liverpool St
regardless of whether 1 in 4 or 4 in 4 trains are Crossrail. In fact
Liverpool St will overall have more capacity.

I'm not sure if I follow.
- More passengers will be using Liverpool Street because capacity and
usefulness of Liverpool Street will be increased.
- Many of these passengers will stay on CrossRail trains and go
straight through.

Both of these are benefits. The second is only a benefit to commuters
wanting to continue West from Liverpool Street, which is probably a
(large) minority of passengers. (Though the number will increase as
working and living patterns change)

We could assume that whether 1/4 or 4/4 of Shenfield trains are
Crossrail, the same number of people are using Liverpool St Underground
station - and that number will be a reduction on 0/4 Shenfield trains
being Crossrail.

Agreed and ditto if 0/4 Bishop Stortford, Grays etc trains are
CrossRail.

However, other Crossrail trains are now arriving at Liverpool St from
Basildon and Grays - some of these passengers would have used Fenchurch
St instead but perhaps Liverpool St is nearer to their workplace, or it
makes no difference whether they arrive at Liverpool St or Fenchurch St
so they just got the first train that came along.

This is placing *extra* demand on Liverpool St.

Matched by the extra capacity.

Looking at it another way, Crossrail will free up a lot of capacity in
Liverpool St mainline for other services - for example new fast services
from Brentwood.

Depends on where the bottleneck is. Is it the station, or is it the
incoming lines? (though the Isle of Dogs line is mostly new and will
provide extra line capacity).

These services will be attractive to Brentwood
passengers heading to the City, and they will use these in preference to
Crossrail - so those passengers carry on using the mainline station as
they were before, but with a faster and probably less crowded service.
If the numbers of people using Liverpool St Crossrail were a problem,
this would help to balance that problem out.

Agreed. But how does this suggest that spreading CrossRail out to
five* branches, each of 4 tph, is not the way to maximise CrossRail
benefit?

*This makes 20 tph, compared to tunnel theoretical capacity of 24 tph.
I would then have train waiting at Liverpool St and Paddington to fill
any spare slots caused by late arrivals. These would only go Liverpool
St to Paddington, and make up the numbers to 24 tph.