Linking functional and structural pavement deterioration processes

Asphalt pavement deterioration is a complex process involving the interplay of functional and structural deterioration. For example, the rate of functional deterioration in the surface layer is expected to vary depending on the structural deterioration state of the base, subbase, and subgrade. This relationship implies that if functional and structural deterioration are modelled independently, the deterioration behaviour of pavement may not be adequately captured. Therefore, elucidating their interdependency and appropriately incorporating it is crucial for the advancement of pavement asset management systems. This study (i) proposes a novel statistical methodology using inspection data to estimate the relationship between functional and structural deterioration processes in asphalt pavement, and (ii) provides the first explicit empirical evidence demonstrating their interdependency. Specifically, a continuous-time hidden Markov model is proposed that explicitly incorporates a mechanism in which the progression of structural deterioration affects the transition rates of functional deterioration. Leveraging the closed-form analytical solution for time-inhomogeneous transition probabilities in the proposed model, a computationally efficient model estimation method is then developed that accounts for the temporal inconsistency between the observation times of functional and structural deterioration states. Applying this methodology, the pavement deterioration process of actual highway roads in Ghana is estimated, where functional deterioration is represented by the International Roughness Index and structural deterioration by the effective structural number. The results demonstrate that functional deterioration is significantly accelerated by structural deterioration. In particular, structural deterioration is found to reduce the expected sojourn time in discretized functional deterioration states by 41.6% to 63.8%. • Statistically estimate the interdependent functional and structural deterioration processes of road pavements. • Utilize a continuous-time hidden Markov model. • Consider inconsistencies in observation timings of functional and structural states. • Provide the first empirical evidence that the progression of structural deterioration accelerates functional deterioration. • Reveal that structural deterioration reduces the expected sojourn time in functional states by 41.6% to 63.8%