Deterioration of bituminous surface layers of pavements is a complex function of stresses produced in the pavement structure due to traffic loading and the environment in which these pavements operate. These stresses are usually inter-related and depend upon each other. Their extent is often difficult to assess, measure and predict. Defects initiated in the pavement layers are regarded as symptoms of pavement deficiencies and as indicators of pavement deterioration level. The Pavement Performance/Deterioration Model—HDN (PP/DM-HDN) was developed earlier (by the authors) from tests carried out on thin asphaltic concrete (AC) pavements located in local urban streets. Its concept is based upon the time of initiation of each defect and the propagation function of that defect. Defects initiated in the pavement structure are correlated via time of their occurrence and their propagation rate. It is a universal model that can be successfully applied to many engineering applications.