It is correct that it measures the amount of traffic. I believe its done with air pressure.

I do have to say that i truly hope that all people who drive like idiots and do not respect any other traffic and pedestrians should hit a concrete wall head on.

Just the other day we were overtaken in an alley, the car drove like 60 KM per hour and a lady walking down the street had to jump away in order to prevent gotten hit by that car.

Take care,

Dutch