I have often seen a black cable stretched across a road that I have been told measures the number of cars that cross it. How does this work?
they have sensors in the cables that hook to a box, in the box is a simple computer it counts cars and speeds by mathematics.
It is not a cable but a hose, it sends puffs of air to a device that counts the number of puffs then divides them by two arriving at an estimated number
