When impact tests are performed on cars to assess the level of protection afforded in side impacts it is tempting to use the test dummies which were originally designed with frontal impact in mind. However, examination of the two situations shows that side impacts, where intrusion plays a more significant part in injury causation, are sufficiently different from frontal impacts for a special test device to be needed. This paper illustrates, from crash-injury studies, the types of injury seen in side impacts. These show that forces rather than accelerations should be measured, because serious injuries can be caused by localised forces to the torso and by crushing of the pelvis. The development of a special dummy designed to measure these forces in side impacts has already been described. This dummy has been calibrated against accident data and tentative human tolerance limits have been proposed. Vehicle impact testing has been performed with this dummy over the past six years and this has shown the value of being able to measure forces. Some of the results of this testing are given. Modifications have now been made to the dummy in the light of recent cadaver testing.