Correct Radar

We call these roads here metal or shingle roads.
They sometimes do get called wash board roads too because of the bumpy corners.
Graders roughen up the surface once in a while.
I think the channels are caused by run off from rain water, following the camber of the road if any, otherwise potholes appear.

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I think washboards are also sometimes caused by slipping differentials
Interesting yaktx, I have never thought of that but I think you are quite right there, thanks, I learned something new today about the "SWER" roads.

The product of rotation, excitation and flux produces electricty.