Here’s Why You See Those Black Tubes Across Some Illinois Roads
I'm guessing that everyone who drives has had the experience of being on a road that you drive regularly, only to discover one or two black tubes (that weren't there before) stretching across the street.
The tubes are obviously too small to act like a speed bump and slow you down, and there's nothing sharp on them that will rapidly deflate your tires like the StopSticks that law enforcement will sometimes use to end a car chase...so what are they there for?
If You Are Of A Certain Age, You Might Remember That "Back In The Day" Full-Service Gas Stations Had Them To Alert Employees That A Customer Had Pulled Up To The Pump
I'm guessing that if you're under the age of forty, you have little to no memory of the black rubber tube that stretched across where you pull up to the gas pump, and even less memory of full-service gas stations, or gas station attendants who wore a uniform:
This dude was ready to handle whatever your car needed, and sell you a map.
As these two show, we need more hats and uniforms in today's world.
The Black Rubber Tubes You See On The Street Are Called "Pneumatic Road Tubes," And They're For Governmental Use, Not For Drivers
According to Jalopnik, the technology they use is simple. Every time a vehicle’s tires roll over the tube, it sends a burst of air that triggers a switch that produces an electrical signal which is recorded by a counter.
A single pneumatic road tube is most commonly used to simply count the number of cars on the road, as well as time the gaps between individual vehicles.
If two pneumatic road tubes are set up spaced slightly apart, the counter can track the number of axles a vehicle has to better determine each individual vehicle’s class, the direction of traffic and the speed at which vehicles are moving.
Here's a good explainer for the process: