On Mon, 14 Jun 2004 20:35:22 -0400, Matthew Brush wrote:

> > IR strobe on the EV, to activate all red, or
> > straight through green on the
> > traffic light.
>
> This is a good thread, I always wondered how they did
> that, I just assumed it was RF.  Sounds easy enough to
> build, not that I really need one, I'm pretty patient.

Here in Britain they did experiment with an RF-emitter
mounted under the front bumper, detected by a loop in
the road, but they found it wasn't very useful because
at a lot of lights there wasn't time to safely cycle
through to green, especially in towns, and because of
traffic levels it usually ended up with the emergency
vehicle trapped behind a queue of cars trying to work
out what to do to get out of the way at the sudden
green.  A contributing problem is that people develop a
feel for the rhythm of the lights, and an unexpected
change can catch them out.

Nowadays emergency vehicles tend to cross over to the
wrong side at traffic lights, because it gets them past
the queue and means they are head-on to traffic so
everyone can see each other - but they don't go against
the red "flat out" because of possible crossing traffic.

Incidentally, in the USA if it's common for emergency
vehicles to change the lights to green their way,
howcome so many "World's worst police videos" show the
suspect vehicle running a red light, just in front of
the police car?

Cheers,

Howard Winter
St.Albans, England.

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