A BioRID (biofidelic rear impact dummy) representing a 50th percentile adult male was seated in the front passenger seat of six new vehicle models in a series of low-speed crash tests. The neck injury criterion (NIC) and other dummy responses that may indicate whiplash injury risk were recorded. Both front-into- rear and rear-into-barrier tests with an average velocity change of 11 km/h were conducted. Head restraints were tested in both adjusted (up) and unadjusted (down) positions. Damage to all models was minor, and longitudinal vehicle accelerations were low (less than 7 g). Neck extension angles and bending moments were much less than injury assessment reference values (IARV) (80 degrees and 57 Nm, respectively), indicating low risk of hyperextension injuries. Neck tension and transverse forces also were less than IARVs used to indicate the risk of more serious neck injuries. NICs recorded on the BioRID during these tests were in the range recorded from volunteers who did not experience long-term injury, and most were below the proposed IARV of 15 m2/s2. NIC and neck tension were lowest in tests of the Saab 9-3, which was equipped with an active head restraint designed to move upward and forward in a rear-end crash. In general, adjusted head restraints positioned to have a small horizontal gap between the restraint and dummy's head tended to produce lower injury measures. However, none of the recorded injury measures exhibited any influence of head restraint height. Both NIC and neck tension seemed to be influenced by crash severity indicated by both vehicle and pelvis acceleration.