This chapter presents laboratory and in-situ experimental techniques used to describe the mechanical behaviour of pavement material at different saturation stages. The use of repeated triaxial load testing to obtain stiffness characteristics as well as the ability of the material to withstand accumulation of permanent deformation during cyclic loading is considered. For unsaturated soils, in addition to mechanical variables, it is shown that a moisture/suction control should be added. Several techniques are described to assist in this. A brief presentation of model parameters and tests needed for model calibration are introduced. Evaluation of pavement structural capacity based on deflection measurements with non-destructive testing equipment are presented. Finally, some examples of laboratory and in-situ measurement are shown.