There are a number of reasons why road surfaces will deteriorate:
- road traffic wears the road surface away causing it to become polished and slippery
- the sun’s UV rays cause bitumen in the road surfacing material to oxidise, leading to the road surface becoming brittle. Once brittle, the road surface is prone to cracking or crazing.
- cracking can also be caused by extended dry, wet or cold periods where, particularly with clay and chalk soils underneath the road, shrinkage or swelling can occur. In clay soils this is very common near trees where roots go under the surface. Cracks allow water to penetrate the structure of the road which softens the foundations, giving rise to deformation (e.g. rutting) and potholes
- soil can be washed into cracks, allowing weeds to take root, causing more cracking