road grooves: why do they run the long way instead of across or diagonally to drain water?
In: Engineering
There are several practical reasons.
First the truck that they used to cut the grooves can drive back and forth across the highway perpendicularly.
Second, and probably the most important, if the grooves went side to side it would probably create a series of hydraulic wedges perpendicular to the direction of travel.
The average tire tread is already side to side more than it is front to back, so another side to side pattern would create high and low spots as the two patterns mesh.
With the grooves running along in the direction of travel the water can move in all four directions and that creates a tiny checkerboardhish pattern where the water can flow perpendicular to travel through the treads and parallel to travel through the grooves.
The goal of putting the little grooves in is to create a drainage pattern with the greatest possibility of getting the water out from between the tire and the concrete. The horizontal pattern, or more correctly the generally diagonal pattern, of the tire is designed to create a kind of pump to help the water get away. And when you match that with the parallel lines moving in the direction of travel you get these little squares instead of bars that go all the way across the width of the tire.
So the pressure patterns can be continuous as you roll forward, but they would be a sawtooth pressure pattern if the grooves and the pavement went the other way.
So between being able to make long continuous cuts by pulling the multi-blade saw behind the truck that cuts the grooves, and the desire not to create little hydraulic impact zones perpendicular to the directional waters being pushed by the moving car, it just makes the most physical sense.
(It’s hard to tell if I describe this correctly… There’s a lot of hydraulics and physics I just sort of glossed over. 🤘😎)
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