Brimstone wrote:
Richard J. wrote:
Brimstone wrote:
Mrs Redboots wrote:
Richard J. wrote to uk.transport.london on Fri, 25 Mar 2005:


But IIRC the tidal rise and fall in Sydney is quite small. In
London it can be more than 7 metres.

Given that for centuries the river provided almost the *only*
public transport available in London, I rather suspect that this
is a problem which has been overcome in the past, and can be
again.

Is it even a problem since boats are loading and unloading now?

Yes, but carrying relatively few passengers. This discussion is
about using the river for mass transit - many thousands of
passengers per
hour. In comparison with trains, boats have very long dwell times,
partly because berthing at a pier takes longer than arriving at a
platform, and partly because it takes longer to embark/disembark.

Surely that depends on the design of the vessel and of the pier?

A Tube train has up to 32 door openings to access 2.5 metres of train
width. If you built a boat that narrow it would be unstable, so you
have to build it wider, but you can't then fit enough doors to empty
that width of boat as quickly as a train.

So to get the capacity you'd have to provide many more pier berths
than at present, equivalent to having, say, 8 platforms at every
tube stop. Having 7-metre tides and strong currents means that
berthing will be even slower and it's more difficult to design
such a pier for large numbers of people.

I accept that a different design would be needed for commuter
(compared to the current leisure) levels of traffic but why would
they be more difficult to design?

To accommodate tides of 7 metres or more, you would need ramps totalling
90 - 100 metres long (to limit maximum gradient to the DfT guideline
maximum of 1 in 12), and sufficient of them to cope with large passenger
flows. It's not impossible, but it's a significant constraint on the
design, and may limit potential capacity just because the piers would
take up so much room.
--
Richard J.
(to e-mail me, swap uk and yon in address)