What Those Random Black Cables Found on Washington’s Roads Mean

I thought I knew what these were, but I was only partly right! Do you know?

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Ever Notice Black Cables Stetched Across the Road?

Have you ever noticed random cables stretched across some of Washington's roads? You may not have ever even noticed them before, or maybe you didn't think anything of them if you did. They are usually only at a specific location for around 24 hours and have an important job gathering information for WSDOT. Do you know what they are used for? If you guessed that they are gathering "speed" data about the cars driving over them, you would be wrong.

Traffic Counters in Washington State

No, they are not trying to find the places where traffic is "speeding" but they do count cars. There are multiple different ways that WSDOT gets traffic information to make important decisions that affect our roadways and one of those tools is a "short-term" portable 24-hour traffic counter. Yes, those are the black cables you see stretched sometimes over a section of roadway for around 24 hours at a time. Sometimes they only put down a single line of cable tubing instead of two, but the purpose is still the same, to count the "amount" of traffic. The cables are actually pneumatic rubber tubing that is laid and taped across the road and then hooked to a counter that can count the number of cars that cross over it. The tubes are filled with air, then taped to the road, and hooked up to a device sensitive to changes in air pressure. Every time a car passes over the tube, the pressure in the tube increases triggering the counter. The unit gathers and then stores the information to be picked up the next day by a WSDOT worker. Now you don't "have" to slow down every time you see one on the road.

Wanna know exactly how it works? Washington State Department of Transportation doesn't have a cool training video like the one I posted below, but the equipment they use is basically the same.