Why do they put grooves in concrete roads like where I live on Highway 66 to Lyons and Highway 287?

Concrete, for all practical purposes, is a non-porous substance when it comes to rainstorms, so the groves help disperse some of the rainwater that is on the road and helps it dry out faster.

Asphalt, or blacktop, is more porous than concrete and has a higher capacity to absorb water, so there's no need for grooves.

“However, while you do want positive drainage and that general direction of flow, you don't really want that kind of water flow, a smooth sheet of water flowing across the road in front of you," she says.

deRiel says even though these longitudinal grooves present a minor obstacle to water flowing easily from the center of the road to the side of the road, what they also do is make the water turbulent, which helps with tire traction in a rainstorm.

There's a point at which the water will flow like a sheet anyway if you have high enough water volume, so there is a point at which the groves don't really help much, but they're way better than nothing.”.

deRiel tells me the grooves should be cut nearly longitudinal to the driving surface.

"They’re pretty small, and anyone operating a motor vehicle should be actively driving which means paying attention to road conditions, surrounding traffic, weather, etc., and actively steering.

Another reason for the long lines in the concrete, according to deRiel, is to help with pavement joint impact reduction.

Cars don't like the bumps, drivers don't like the bumps, passengers don't like the bumps, and maintenance workers don't like the bumps either because bumps in pavement generate impact loading.

For example, freshly paved asphalt roadway generally has some small voids that serve the same function as the grooves in concrete, they help with drainage and preventing sheet flow.