Bill Bolton wrote on 11 September 2009
09:20:55 ...
GazK wrote:

Don't forget the loss of capacity due to increased dwell times loading
a DD train...

Dwell time issue only become significant if the train a significant
percentage of the passenger carrying capacity of the DD train
boards/alights at every stop on the route.

In most systems that doesn't happen, with large boarding/alighting
flows only occurring at a relatively small number of stops along the
route.

Bill Bolton
Sydney, Australia

This isn't "most systems". It's London, and all 6 of the central area
stations on Crossrail (the ones where 24tph are currently planned)
*will* have heavy boarding/alighting flows.

--
Richard J.
(to email me, swap 'uk' and 'yon' in address)