Pavement deterioration or distress can be classified into two basic categories for all pavement
types—structural and functional. The most serious category is structural.
Structural deterioration results in reduced ability to carry load and a decreased pavement
life. Functional deterioration can lead to and accelerate structural deterioration, but it
is only related to ride quality and frictional characteristics. A third type is environmental
deterioration, which is a form of material-related distress. Environmental deterioration
affects pavement materials and will generally exhibit itself as either functional or
structural deterioration.