Originally Posted by
omgwtfbbq!
The strips in the road detect the electro magnetic field generated by your engine, but I think he's referring to something emergency vehicles use, I was pretty sure you need a transponder to do that though.
actually the iron in your car affects the electric circuit in the ground, via EMF effects. that's why motorcycles can sit at traffic lights and the sensors won't detect them. they don't have enough iron for the circuit to detect a change in current. that's also why they sell "pieces of iron" at the bike shops and market them as light changers. there are transponders that only a few traffic lights recognize that are able to change the light. other than that, the flash your high beam is a myth.
just pure coincidence.