On Tue, 20 Oct 2009 02:56:32 -0700, Matty F wrote:
Why do traffic engineers make you wait at the red light for 10 or more
seconds before the green light for the cross road changes to orange?

I think it varies by country and region, TBH - there doesn't seem to be
much consistency. Maybe you're just in an area where they happen to like
long delays; I've seen some setups where it really is 0.

One possibility is that it's just to give time for anyone already within
the junction (e.g. a slow cyclist) to clear it without seeing that the
lights are about to change and worrying that they'll get flattened.

Maybe it's also a delay to allow any emergency services vehicles chance
to muscle through for setups that don't give automatic priority to
transponder-fitted emergency vehicles (not sure if they have those in NZ?)

There's also the chance that approaching traffic will run the orange / red
light, so the planners want as much delay as possible before a change
to green just in case (I remember one set of lights on a fast road coming
into Wellington where the change from green to red was *extremely* quick -
there were probably quite a few incidents of vehicles sailing through on
a red/orange at that particular junction)

cheers

Jules