Occupant injury in automobile rear-end collisions is rapidly becoming one of the most aggravating traffic safety problems with high human suffering and societal costs. Recent studies in Europe, Canada and Japan have found that injury claims, in particular neck injuries due to rear impact have steadily increased and resulted in significant financial cost. Using the MADYMO facet technique, a series of numerical models have been built to get an understanding of how seats, vehicle and occupants interact during rear impacts. A family of Hybrid III (5%, 50% & 95%) dummies and prototype seats with accurate geometrical descriptions were used in the simulation. Usage of this technique not only yields more realistic seat and ocuupant impact interaction but also provides flexibility in modeling seat system in detail. All the dummies contained models of TRID (TNO Rear Impact Dummy) neck and facet surface head form. Models of the TRID neck and facet head form were available for 50% dummy. A validation study was done on prototype seats with instrumented Hybrid III 50% dummy with the TRID neck. In general, good correlation were obtained for all seats which were tested at different crash pulses. The measured signals include neck moments and forces as well as seat and dummy kinematics such as seat back and head rotation. However, it seems likely the current model is unable to capture neck shear force response.