youll find these all over the place if you pay attention.
Did you ever wonder why there were black rubber tubes layed across the road in random places??
The rubber tube when driven over send a puff of air to a sensor that counts the axles that drive over it… so they can monitor traffic… Im sure they monitor time between pulses and amount.
Ive seen em everywhere. usually they are accompanied by a small black box on one side of the road.