On Mon, 29 Sep 2003 20:08:48 +0100, Paul Weaver
wrote:


On a similar note, what geological problems are there preventing massive
tube expansion?

It's usually impossible to get more than three deep tube lines running
through one place. Strictly speaking there are four deep tube lines
at Waterloo, but the Waterloo and City is in fact very shallow at that
point, and also terminates there which presumably is easier to
accommodate than a through line. That doesn't rule out tube expansion
completely but it does limit what could be achieved in Central London.

Tunnelling is a slow and labour-intensive process, so any investment
now in tube expansion would not yield benefits for quite a few years.

Why is no one investing in PRT (http://www.atsltd.co.uk/)?

Because it's incredibly speculative. Monorail, light rail, and other
such ideas have been around for decades. In practice very few have
been implemented successfully, and it's very hard to see how such a
system could ever be profitable.

I'm guessing the red tape involved in creating a private mass transit
system is prohibitive.

There would be prohibitive planning difficulties, but ultimately
that's because residents and businesses often don't like new elevated
structures being put along their roads.

Martin