"Aidan Stanger" wrote in message
...
John Rowland wrote:

Hi all,

I have often seen footage of foreign crossroads with 2 diagonal
pedestrian
crossings in addition to the 4 orthogonal crossings we usually have here
in
Britain. Today I found a crossroads with all six crossings just east of
Burnt Oak tube station in Northwest London. According to the nearest
person
I could accost, it's been like that for about 2 or 3 years. Is this the
only
one in Britain? It seems to have been there too long to be a trial.

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

"Paul Oter" 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.

More likely it costs a fiver more in paint

--
r

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.

The Japanese have a good example in central Tokyo which combines IIRC
both types of crossing, and they know a thing or two about moving
people around.

OTOH, since it seems our local authorities are anti-car to a
ridiculous extent, this is probably an academic discussion. :-)

Rgds,

"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.

That would be the case if the traffic planners calculated the length of the
pedestrian phase on the basis of the time taken to cross two arms of the
junction. In practice, they are likely to only consider the time taken to
cross a single arm of the junction.

PaulO

"Paul Oter" typed


That would be the case if the traffic planners calculated the length of the
pedestrian phase on the basis of the time taken to cross two arms of the
junction. In practice, they are likely to only consider the time taken to
cross a single arm of the junction.

Too true :-(
Then they totally redesign some junctions so that the pedestian has 3 or
4 arms to wait for & cross rather than one or two.

Golders Green used to have an 'all red' phase when a fast pedestrian
could safely do a diagonal flit. It is now a nightmare.

--
Helen D. Vecht:
Edgware.

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.