Virtual Speed Bump / Driving assistance

Virtual Speed Bump aims to mention drivers when they over speed. These tiny devices could be installed uniformly along the both sides of a freeway. It could calculates the speed of a car by the formula (V=S/T). The distance between two tiny devices is 5 meters. The time of a car passing by contiguous devices will be regarded as T in that formula. Then, the speed of a car could be worked out easily. Meanwhile, if a car over speed, each four devices would work together to cast a cautionary pattern.