The role that wheelchairs and wheelchair mounted headrests play in rear impact occupant protection for children who remain seated in wheelchairs while traveling in motor vehicles was investigated using sled testing and computer simulation. Study goals were to establish pediatric wheelchair and headrest design guidelines and to determine the effect of headrests on relative injury risk outcome measures under rear impact conditions. Two series of sled tests (16 mph, 11g) were conducted using a Hybrid III 6-year old anthropomorphic test device (ATD) seated in identically configured manual pediatric wheelchairs, with and without headrests. Wheelchairs remained intact and the ATD remained upright. Rear impact front wheelchair securement points were subjected to loads similar to previously described (Ha, DongRan, 2004) rear securement points in frontal impact, although Ha used the more severe 30mph, 20g frontal impact WC19 -- Wheelchairs Used as Seats in Motor Vehicles (ANSI/RESNA, 2000) crash pulse. Sled test ATD data analysis indicated that wheelchair headrest use had a potentially protective effect based on pediatric head and neck injury risk outcomes. Sled test data established response corridors for MADYMO computer simulation model development, and defined statistical test target thresholds for model validation. Two simulation models were developed, with and without a headrest. The models validated well for tiedown loads, wheelchair acceleration, lap belt loads and chest acceleration. Outcomes related to head and neck response were not as strongly validated. Model ATD neck response characterization methods were developed. Finally, parametric sensitivity analyses were used to develop wheelchair and headrest design guidelines for pediatric manual wheelchairs in rear impact for front securement point loads, rear wheel loads and seatback loads. Pediatric injury outcome measure sensitivity to wheelchair, headrest and crash pulse parameters was evaluated. Neck injury criteria (Nij) was sensitive to headrest placement; resulting recommendations specify placing the headrest as close as possible to the back of the head, and top of the headrest pad should be at least 5 cm above the head center of gravity. Effects of stiffer 6-year old ATD neck response on injury risk outcome measures were evaluated and found to reduce likelihood of severe neck injury.