En 
Inductive loops have been used for decades to count vehicles, control traffic-lights, speed-control enforcement and other traffic applications. Inductive loops can be very reliable detection method when it is installed with a certain precission under-ground, protected and secured, deep under the road surface and not influenced by common problems for detection in traffic. Characteristics that is even more important in tunnels, in a hostile environment with a special need for reliable, available and maintainable safety systems.
