In article , Martin Rich
wrote:
On Mon, 29 Sep 2003 20:08:48 +0100, Paul Weaver
wrote:


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

What problems does it solve to put a single-occupant vehicle
onto rails?

None whatsoever.

If the standard vehicle is going to be a 4-seater like a car
to allow for family outings, then it will take up the same space as a
car. If it is a single-seater, then if the crossection of the route is
reduced to make use of the small size, then 4-seaters will be too big.
Not likely to be acceptable.

Braking distances will be about the same as for rubber-tyred
vehicles, the examples in the Highway Code assumes a deceleration of
about 0.5g. In very good conditions a road vehicle can achieve 1.2g,
this is exceptional, but in rain etc 0.2g is all that can be achieved.
Rail vehicles can achieve 0.2 in normal conditions, with magnetic
track brakes they can achieve 0.5g. So safety distances will be about
the same. You can have automatic close-following, as on the French VAL
system, and there are plenty of systems for doing likewise with road
vehicles. This approach means you have to have short platoons of
close-following vehicles behaving as if they were a single vehicle,
with a normal safety-distance between platoons. You have to assemble
the platoons, run them through to near their destination, then
disperse them to their final destination.

It's all difficulty. And a lot of infrastructure. And what
will the return be? The sums have been done, many times, and the
prospects found not appealing.

It's not nice to stamp on enthusiasm and bright ideas, but
sometimes it has to be done.

--
Michael Bell