Comprehensive laboratory triaxial dynamic testing of subgrade soils in Kuwait was conducted to determine the engineering parameters for pavement design and construction. A literature survey and a review of ongoing road construction projects indicated that the subgrade soils were predominantly granular (A-1-b and A-2-4) according to the AASHTO classification system. A chemical and mineralogical analysis indicated that quartz is the principal component. Gypsum, calcium, magnesium, and sodium sulphate are also present in varying proportions. The results of California bearing ratio (CBR) and direct shear tests indicated that these soils exhibited the characteristics of a high-performance subgrade. The angle of internal friction ranged from 20 to 40 deg, with an average value of about 30. The soaked CBR ranged from 10 to 47. Varying the moisture content around the optimum by+/-2% resulted in significant changes in soil strength and deformation in certain cases and had an insignificant effect in some other conditions. This depends on the soil compaction curve. Soils with nearly flat curves around the optimum were less sensitive to mositure variation. A model for rut depth prediction was developed, and its material constants were evaluated. The model was implemented in a rut depth prediction system. The developed model and its guidelines were demonstrated to be of practical significance for the range of the investigated soils.