A new simple design approach will be described that utilizes test results from the repeated load triaxial apparatus to establish the risk level of permanent deformations in the unbound granular layers (UGL) in pavement constructions under consideration of the properties of different unbound granular material (UGM). From this data a serviceability limit line (plastic shakedown limit) stress boundary for different UGM was defined. Below this line the material will have stable behaviour. It will be shown that the proposed design approach is a very satisfactory simple method to assess the risk against rutting in the UGL, even without the calculation of the exact permanent deformation of the pavement construction. Additionally, a plastic model and a nonlinear and a nonlinear elastic model (DRESDEN-Model), which is also described in the paper, were implemented into the 3-D FE-program FALTFEM. To check the validity of the plastic DRESDEN-Model, field tests in a test section (2.5m x 2.5m x 1.5m) on UGLs using cyclic loading (1,000,000 load repetitions) were carried out. The surface deformation induced by dynamic loading were predicted using the 3-D FE program FALTFEM. A comparison was carried out to assess the accuracy of the plastic model by comparing the results of calculated deformations from the plastic model against the measured values