A pothole solution – Build roads well above ground level

• Dave Onderstall writes:

I am interested in potholes and have ‘studied’ them over many years.

My conclusion is that potholes very rarely occur where the road surface is above ground level. They are worst where the road surface is well below the ground surface.

It seems to me that the obvious solution is to build roads well above the ground surface. This would eliminate the need for storm water drains, saving a lot of money and eliminating the problems caused by the runoff.

Can anyone explain to me why we dig a deep hole, fill it with layers of rock and gravel and the tarmac surface is lower than the ground level before construction started?