As I understand it over here (NZ) the radio antennas on most city traffic
lights are to allow buses and emergency services priority - the red cycle
can be delayed slightly.
I've been trying to find out more details re the frequency & codes used etc.
- but purely for academic reasons of course :-)

(The antenna length suggests approx. 150MHz but that's all I've been able to
guess so far)

Richard
> -----Original Message-----
> From: Dennis Plunkett [mailto:dennis@RDD.NECA.NEC.COM.AU]
> Sent: Friday, July 30, 1999 1:44 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: Traffic Lights (Was Car LED lighting etc ...)
>
>
> At 11:11 30/07/99 +1000, you wrote:
> >Boy, this must be the longest thread I've seen.
> >
> >OK, some posters were talking about air traffic control,
> collision avoidance
> >etc. Here's a question re traffic control.
> >
> >In Australia, Melbourne suburbs, lots of traffic lights seem to be
> synchronised
> >so that heavy traffic flow on a main road gets all green
> lights. I always
> >assumed it was done with simple timers. However, I'm *told*
> that radar
> detectors
> >- you know those little black-box gizmos you put on your
> dash to defeat the
> >police? - are set off when approaching these synched lights.
> ('Course that's
> >only what I've been told. Heh! Well, I wouldn't  use illegal
> technology
> myself,
> >naturally ..............!)
> >
> >So, are synched traffic lights controlled with a microwave
> system somehow?
> >
> >Just wondering.
> >
> >PJH
> >
> >
>
>
> Are, uhm NO.
> Sync traffic lights are via telephone lines (Also provides
> communications
> to the signal control centre) (Notticed how the "In case of
> faults call
> 131360 and quote this number" sign is gone?)
> This is so for the city area as it allows VIC roads to alter sequences
> during heavy traffic times.
>
> Dennis
>