"John Rowland" wrote in message
...
The traffic lights here have three (traffic) phases:
1) turn right from the main road
2) forward or left from the main road
3) forward, left or right from the minor road
...in that order. Every other junction which I know has these three phases
has them in the opposite order.

Does anyone know why this junction is different?


Looking at the junction on Google Maps the A10 is two lanes per direction
dual carriageway which expands at the junction to five lanes arranged left
to right as follows:

1 Left Turn
2-4 Ahead
5 Right Turn

It looks to me like physical constraints dictate that lane 5 is rather short
and traffic waiting there would tail back preventing other traffic from
reaching lanes 1-4. Clearing as much right-turning traffic from the junction
*first* in the sequence avoids this, but at the cost of making the junction
more dangerous. The danger is that someone sitting at a red light in lane 4
will see the light for lane 5 change and think it applies to them, taking
off across the junction into the path of right-turning traffic from the
opposite direction. The light(s) for lanes 2-4 are out of the direct line of
vision for someone in lane 5 so the reverse situation doesn't arise when the
phases are in the more usual arrangement.

There is a junction on the A270 in Hove (near where I live) which is even
more constrained in that right turning traffic has to slew across in front
of the waiting 'ahead' traffic before making the right turn.

http://maps.google.co.uk/maps?f=q&hl=en&geocode=&time=&date=&ttype=&q=HOVE+ A270&sll=51.658963,-0.059084&sspn=0.00121,0.002325&ie=UTF8&ll=50.83890 1,-0.178018&spn=0.001231,0.002325&t=k&z=19&iwloc=addr &om=1

The traffic lights all have signs on the poles which read "RIGHT TURNS GO
FIRST", and *still* people try to drive ahead when the right filter changes.

A lot of the above would be avoided if we fell into line with most of the
rest of the world, where the lights for filter lanes have arrows on the red
and amber heads as well as the green (ASCII art diagram below).

D A Stocks


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