RATIONAL APPROACH IN APPLYING RELIABILITY THEORY TO PAVEMENT STRUCTURAL DESIGN

A rigorous yet practical methodology for evaluating pavement design reliability is described. Pavement design reliability is expressed in terms of the probability that a pavement will withstand the actual number of load applications--that is, the traffic--on it during a selected design life while maintaining its structural integrity. Traffic is selected as the design element to which the reliability analysis should be applied because it is the only factor common to all pavement types. The methodology therefore provides a uniform basis for evaluating the reliability of alternative pavement designs with different pavement types. Alternative expressions of reliability (such as the probability of not exceeding a specified level of pavement distress) do not provide a proper comparison of alternative pavement types. A mathematical model that can be used to evaluate the reliability of alternative pavement designs and to calculate the design traffic for the selected design is presented. A systematic process for updating and improving initial estimates of the statistical parameters needed for the evaluation of reliability is also described.