Crash test dummies able to mimic the motion of a human are needed to assess the protective performance of seats and head restraints in crash tests. This study evaluates both a newly developed dummy for rear impacts (BioRID P3) and the Hybrid III dummy by means of a recently available set of human subject data. The study also meets the need for validation of the BioRID P3 at a higher impact severity than that previously achieved. The BioRID P3 and the Hybrid III were evaluated by means of pendulum impacts to the back and compared with data from previously run cadaver tests. Seated dummies were struck with a pendulum with a mass of 23 kg and an impact velocity of 4.6 m/s at the level of the 6th thoracic vertebra. The results showed that peak values and temporal responses of the BioRID P3 was closer to that of the corridor of the cadavers than the Hybrid III in terms of horizontal, vertical, and angular displacement of the head and of the head relative to T1.