A simple phenomenological damage model based on the number of load applications, the critical response, and the material modulus was used with three sets of experimental data: (a) the decrease in the modulus of an asphalt concrete (AC) under laboratory, direct tension fatigue testing; (b) the decrease in the modulus of a pozzolan–lime-stabilized sand under accelerated loading in a full-scale pavement testing facility; and (c) the increase in the permanent strain at three levels of two subgrade materials, also under full-scale accelerated loading. The model is shown to be capable of describing the damage reasonably well for all three cases, though with some limitations. For the direct tension tests with AC, the rate of damage was underpredicted for two of six samples under controlled stress testing, whereas the prediction for all 10 controlled strain tests was good. For freeze–thaw conditions, the model for permanent strain in the subgrade also tended to underpredict the damage rate. The simple damage model may be useful for incremental–recursive pavement design or for pavement management systems.