The costs of pavement materials combined with the huge volumes of materials required for construction and maintenance of road networks, forms the basic need of reliable methods and effective tools for optimizing design and performance of road pavements.

During the process, the timing of the rehabilitation activities is an important parameter to avoid waste of resources due to expensive rehabilitation because of late and essential reactive actions, or due to premature investments from poor planning and understanding of the nature of the failure.

Another important issue during the design is not only to consider the requirements to service life as defined by the critical limits, but also to evaluate how the pavement performs from the initial state to the critical state.
Again, this will influence the decisions for the timing and type of following rehabilitation activities.

Figure 1 illustrates the consequences of alternative performance graph with the same initial state and the same terminal state.

As seen from the black and the blue performance graphs the effects on predicted user costs over the lifetime is dramatically affected by the shape of the graphs.
The user costs can be vehicle operating costs, accidents costs, delay costs and loss in “aesthetic value”, related to the prediction of roughness, rutting, skid resistance and surface distresses.

Figure 1: The importance of developing accurate performance models.