On Thu, 16 Jul 2009 00:23:13 +0100, Basil Jet
wrote:
How are the phases of traffic lights controlled anyway? Is there a
program inside them written in some standard programming language,

Pretty much, yes. It's on a PROM but I can't remember what language is
used.

and someone has put the IF statement in the wrong place? I would have
guessed that the
danger of conflicting greens would have prevented the control sequence
from being written in a standard language and that something much less
flexible would have been used, which would have prevented the error Isee
at this junction.

Allegedly, a new PROM is created for each junction, while temporary lights
run on a standard sequence. Often the PROM is re-blown after the previous
one has been shown (by long queues) to be wrong.

I say allegedly because at one junction I know, the westbound stops before
the eastbound if no vehicles are detected there. At this junction this is
completely pointless, as both westbound and eastbound traffic is only
allowed to go straight on.

Colin McKenzie

--
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