Past rollover condition testing reported by the author utilized experimental seat belts, a rigid seat and a sitting pelvis Hybrid III mannequin or volunteer to observe dynamic vertical excursion. Other testing in a rollover condition utilized a rigid mannequin molded from a Hybrid III, sitting in a production vehicle restraint system. Application of rigid device in the test allows for simplification of the problem under study, yet limitations in the interpretation of the results. A third test program was conducted combining the rigid device of prior testing into one test, thereby allowing further scientific inference as to the affect of the seat belt restraint system in rollover conditions. Results show that an important factor in the extent of occupant vertical excursion is the kinematics and compliance of the occupant. Seat belts, in particular for this study, the lap belt, play a significant role in conjunction with other components of the motor vehicle in limiting the extent of occupant displacement in rollover conditions.