What is this thing?

Where I'm at, there are "speed vans", these survey boxes are also used to determine where the speed vans should be placed, though the other uses such as vehicle weight/axle count others mentioned are the main function afaik.

These speed vans are equipped with cameras that can capture several lanes and directions, from a great distance. You just drive past these things and they have a sign on top saying "your speed has been checked".

I always slow way down on these just to slightly skew the numbers. Though that could go good or bad for me, without a way to know.

If these had been around when I was a kid, I'd probably run over it a bunch of times with my bike. Especially going "backwards."

They measure speed (how long between compression of each hose), direction (which hose was hit first), weight (how much was each hose squeezed), and axel count (how many pairs of wheels went over).

When you are calculating road wear, number of axels (and weight) is more important than number of vehicles.

You can often derive the number and type of vehicles by the pattern of “hits”. A passenger car will have a different pattern than an 18-wheeler; a van will have a longer wheelbase than a motorcycle, etc.

Yes, with two hoses they are measuring count, speed, and vehicle weight. Not enforceable, as many others have said - nobody will be getting a speeding ticket from this. It's just data collection.

Note: force measured on the hoses is a function of vehicle weight and speed. If you only have one hose, you can't tell the difference between a light vehicle moving fast and a heavy vehicle moving slow. With 2 hoses you can now measure speed, which you can then use along with the pneumatic force to figure out weight.