Application of System Dynamics to Integrate Pavement Preservation in Flexible Pavement Design Process

The performance of a pavement depends on factors like the characteristics of the materials in different pavement layers, traffic, climates, environments, construction quality, etc. Though a pavement is designed for 15 years, conventionally, the pavement reaches the threshold level of performance before the design life, warranting minor and major rehabilitation treatments because of factors beyond the control of the designer. However, the maintenance and rehabilitation treatments during the design life of a pavement are not considered in the design process. The performance of a pavement is defined in terms of the various distresses, i.e., cracking, rutting, roughness, potholes, etc. The performance of the pavement also depends on the strength properties of different pavement layers and their thicknesses, quality of construction, traffic, climate, etc. The level of influence of these parameters on each of the distresses is different. In this study, the Mechanistic Empirical Pavement Design Guideline design tool AASHTOWare is used to simulate the data for cracking (percentage of bottom up fatigue cracking), rutting (total rutting), and roughness in terms of the International Roughness Index. A sensitivity analysis is carried out to study the influence of the design parameters on the distresses. From the results of AASHTOWare simulations, a relationship is established between design input parameters and distress growth using multiple linear regression. While this model gives the estimate of distress over time with respect to the design parameters, the year at which the first preservation activity has to be carried out is to be determined. Considering the pavement as a system, the system dynamics concept could be well suited to study the influence of various factors on the performance of the pavement. A system dynamic model is formulated and implemented using system dynamic software POWERSIM. This study identifies the optimal intervention year for the pavement preservation strategies that depend on traffic level, design layer thicknesses, and modulus (strength) of the pavement layers.