Rut prediction, whether stemming from deformation in asphalt or soil, has always been a particularly difficult area for the pavement engineer. This paper centres around a predictive technique for soils and granular materials and presents two examples where the technique has been used and appears to be a sufllciently accurate tool for achieving meaningful results. One example is of trafficking at a laboratory scale, the other relates to airfield pavement design. The derivation of the model itself is described and the means of obtaining model parameters discussed. Finally its role in pavement design is examined and recommendations made for its use.