Can you expand on that thought a little? At first glance, if traffic was moving in one direction, how would you use a motion sensor to let the other direction move? Consider that motion followed by no motion might indicate a second car was located and waiting at the intersection, but it might also indicate the second car ran the light.
Why would you want to sense motion? Passing birds, mischievous kids etc could cause havoc.Traffic lights are usually controlled by vehicle presence detectors.
Can you expand on that thought a little? At first glance, if traffic was moving in one direction, how would you use a motion sensor to let the other direction move? Consider that motion followed by no motion might indicate a second car was located and waiting at the intersection, but it might also indicate the second car ran the light.
A single IR Tx/Rx setup will detect vehicle presence (which I think is what you want). Presence/absence signals in succession would indicate motion rather crudely, but a second Tx/Rx pair spaced a known distance from the first could perhaps be added to give an indication of vehicle speed (if you really are interested in motion).
Generally the vehicle detector is "an inductive loop vehicle detector".
A condutor of about 1.5 mm square, is insulated with polyethylene about 4 mm diameter and laid in a slot cut in the road surface. there is usually several turns of the insulated wire. The loop is connected to the detector by a special single pair cable. The change in loop inductance due to a vehicle presence is often done by a frequency shift measurement technique.
Hope this helps.
The metal detectors work well. Buried wire loop. They do not see bicycles or people.
In this area they now use cameras. They look at the pavement. When a stopped car covers up part of the pavement for a while the light switches.
In my neighborhood they use cameras to catch people running red lights and mail them a ticket. I wondered why some cameras were facing oncoming traffic when Florida doesn't have license plates on the front. That explains it.