The most important tool to date for testing seat-systems in rear impacts is a crash test dummy. However, investigators have noted limitations of the most commonly used dummy, the Hybrid III. Although the BioRID I is a step closer to a biofidelic crash test dummy it is not user-friendly and the straightening of the thoracic spine kyphosis is smaller than that of humans.The objective of this study is to compare the performance of the latest prototype of the BioRID, the P3, with those of volunteers. The BioRID P3 has new neck muscle substitutes, a softer thoracic spine and a softer rubber torso than does the BioRID I.The BioRID P3 was validated against volunteer test data in both a rigid and a standard seat without head restraints. The dummy kinematic performance, pressure distribution between subject and seatback, spine curvature, neck loads and accelerations were compared to those of seven volunteers and a Hybrid III fitted with a standard neck. The BioRID P3 provided repeatable test results and its response was very similar to that of the average volunteer in rear impacts at ΔV= 9 km/h.