I also thought about Laser Light … but only problem was that, we need separate transmitter and receiver aligned accurately across the road.

Prototype will work fine, but do u think the range of IR will be enough to reach vehicles or objects moving around 20 feet. One more thing, if you place the sensor at lower range will it be able to detect vehicles moving at 60kmph above? Look into these issues.

If IR is very short range working sensor then we go with IOT (internet of things) the growing and developing technology now.we can use this to over come all the problems.Because the complete city is going with smart technology.

no actually u need some sensors which are industry grade for better performance because we have to think about all the day to day senario