Fatigue laws obtained by means of laboratory tests do not usually take into account the fact that asphalt mixtures in highways have rest periods (without loads). These rest periods tend to increase the fatigue life of mixtures due to the phenomenon known as healing. A new fatigue test which includes rest periods has been developed. In order to study healing, tests with and without rest have been carried out on asphalt concrete, and the corresponding fatigue curves have been obtained. The test results show an increase of five to ten times fatigue strength. This paper summarizes the main experiences. The testing method used in the research is described. The results are analyzed by means of a statistical technique called discriminate analysis.

A critical factor in highway design is maintaining a good consistency with a road geometry that fits the drivers’ expectations. Presently, highway geometric design consistency is usually evaluated on the basis of operating-speed profile analysis, which requires the use of operating-speed models. This paper presents research carried out in Colombia consisting of a study of vehicle speeds on tangents and curves of two-lane rural highways. Car speeds were measured on the approach tangent and at the beginning, middle, and end points of curves by using two radar meters. The operating-speed prediction models that were developed are described. The speed change experienced by drivers from tangent to curve was also studied, and a model is presented that predicts this change. Finally, the model developed for operating-speed prediction at the midpoint of curves was compared with equivalent models calibrated in other countries and applied to a Colombian highway. This comparative study highlights the importance of usi...