Initial Studies of Dynamic Responses of Female and Male Volunteers in Rear Impact Tests

Licentiate thesis, 2010

Whiplash Associated Disorder (WAD) - commonly denoted whiplash injury - resulting from vehicle impacts, is a worldwide epidemic. These injuries occur at relatively low changes of velocity (typically between 10-25 km/h) and in impacts from all directions. Rear impacts are however the most common in the accident statistics. Since the middle of the 1960s, statistical data has shown that females have up to three times higher risk of sustaining whiplash injuries than males, even under similar crash conditions. Studies have indicated that there may be characteristic differences in the rear impact dynamic response between males and females. The 50th percentile male dummy might thus limit the assessment and development of whiplash prevention systems that adequately protect both male and female occupants. Data from volunteer tests is needed to establish the dynamic response for females and males. Such data is fundamental for developing future occupant mathematical and/or mechanical models for crash safety development and assessment. These models can be used, not only as a tool in the design of protective systems, but also in the process of further evaluation and development of injury criteria. The aim of this study was to quantify the differences in dynamic response between average sized females and males in low-speed rear impacts. Two rear impact volunteer studies were conducted. In the first study, data for the 50th percentile female were extracted from a previously performed rear impact car-to-car crash test series with female and male volunteers at 4 km/h and 8 km/h. In the second study, a sled test series was performed with 50th percentile female volunteers at 5 km/h and 7 km/h. In both studies, response corridors for the female volunteers were generated and compared with previously published corridors for the 50th percentile male. Additionally, the Neck Injury Criterion (NIC) values, head-to-head restraint distances and contact times were compared for the female and male volunteers in both studies. The overall result showed differences between the females and the males in the dynamic response and in the NIC values. For example, the head x-acceleration peaks were on average higher and earlier for the females; the head, T1, and head relative to T1 x-displacement peaks were on average lower and earlier; the initial head-to-head restraint distance was on average smaller for the females, resulting in earlier head-to-head restraint contact time for the females.