Richard Buttrey wrote in message . ..
On Sat, 3 Jan 2004 09:47:35 -0000, "Paul Oter"
wrote:


"Aidan Stanger" wrote in message

The big mystery is why so few crossings in London are marked like that.
Space is such a constraint that most of London's signalled crossings use
the Barnes Dance sequence UIVMM.

I suspect the main constraint is that a diagonal crossing, being a greater
distance, requires vehicle traffic to be stopped for longer than with an
ordinary orthogonal crossing. So it's pedestrian convenience vs motorist
convenience.

PaulO

An optimal phasing for a number of pedestrians would surely depend on
where pedestrians are trying to get to, and the relative numbers
wanting to make a simple orthogonal move and those wanting a diagonal
move?

If all pedestrians wanted to end up on a diagonally opposite corner,
then one diagonal move as opposed to two orthogonal moves would result
in a shorter overall crossing time and obviously a shorter stopping
time for motorists. It becomes more complex when a group of
pedestrians want to undertake both types of crossing. Clearly there's
a break even point somewhere which minimises the sum total of all
pedestrian crossing movement times.

You would rarely, if ever, find a crossroads where all pedestrian
desire-lines were diagonal. Even if the majority are there is nothing
to be gained by preventing orthoganal crossing at the same time as
diagonal, which seems to be what you are suggesting.