Maybe you could get some ideas from Pee-Wee. (Sorry, couldn't resist)

> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Richard Prosser
> Sent: August 2, 1999 4:03 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: Traffic Lights (Was Car LED lighting etc ...)
> 
> 
> Also - If I had a strobe light on my bicycle (to stop people from running
> into me) that "just happened" to match the required pattern, then .....
> Richard
> > -----Original Message-----
> > From: Craig Lee [mailto:clee@ATTCANADA.NET]
> > Sent: Tuesday, August 03, 1999 9:47 AM
> > To: PICLIST@MITVMA.MIT.EDU
> > Subject: Re: Traffic Lights (Was Car LED lighting etc ...)
> >
> >
> > Hmm.... I wonder if the sensors will respond to invisible or nearly
> > invisible light....
> >
> > I was in a cab once where the cab driver looked both ways carefully,
> > then flicked his lights on and off at a certain rate.  To my surprise,
> > it worked!!
> >
> > Probably something you wouldn't want to get caught at, but what you
> > can't see...
> >
> > Craig
> >
> > > -----Original Message-----
> > > From: pic microcontroller discussion list
> > > [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Matthew Fries
> > > Sent: August 2, 1999 2:54 PM
> > > To: PICLIST@MITVMA.MIT.EDU
> > > Subject: Re: Traffic Lights (Was Car LED lighting etc ...)
> > >
> > >
> > > > A method that I have seen used here in the US is a system that
> > > extends the
> > > > green to emergency vehicles by keying off a white strobe
> > mounted on the
> > > > front of the vehicle.  The strobe frequency is specific
> > (and unknown to
> > > > me).  You can spot these intersections that are suchly
> > equipped- the
> > > > optical sensor is mounted in a horizontal tube pointed
> > along the traffic
> > > > flow, attached to the same support that the light is connected
> > > to.  I used
> > > > to see these all over the Washington, DC area, but since
> > I have moved to
> > > > Austin, TX, I have not noticed any.
> > >
> > > There are 2 strobe lights atop the ambulance, and they
> > flash 2 times each
> > > in the course of 1 second. The pulse looks something like this:
> > >
> > >     __    __       __    __
> > > ___|  |__|  |_____|  |__|  |___
> > >
> > >    Left Left     Right  Right
> > >
> > > I cannot be sure of the duty cycle, but I would bet that
> > the receiver is
> > > not that accurate.
> > >
> > > Maybe it just counts the pulses in 5 seconds.
> > >
> >
>