"mookie89" wrote in message news:IPkvc.5247

Also, our emergency vehicles have what's known as an OptiCon System on
board. Basically it is a very specific white high intensity strobe lamp
aimed slightly upward. At many USA intersections a little periscope
appearing apparatus is mounted just above the traffic light. That's the

Don't you get boy-racers, and other miscreants, attempting to
synthesize the correct light-frequency and thus give themselves priority
at junctions ?

We'd get that sort of thing here. My last job involved telemetry
via UHF radio. Other European countries apparently used it to
give emerg vehicles priority but it was apparently rejected for the
UK, because nefarious persuns would be able to defeat it, even when
we proposed a 200-years-to-break challenge-acknowledge protocol (it
was two-way) !