Child posture and shoulder belt fit during extended night-time traveling: an in-transit observational study.

Understanding pediatric occupant postures can help researchers indentify injury risk factors, and provide information for prospective injury prediction. This study sought to observe lateral head positions and shoulder belt fit among older child automobile occupants during a scenario likely to result in sleeping - extended travel during the night. An observational, volunteer, in-transit study was performed with 30 pediatric rear-seat passengers, ages 7 to 14. Each was restrained by a three-point seatbelt and was driven for seventy-five minutes at night. Ten subjects used a high-back booster seat, ten used a low-back booster seat, and ten used none (based on the subject height and weight). The subjects were recorded with a low-light video camera, and one frame was analyzed per each minute of video. The high-back booster group exhibited a statistically significant (p<0.05) decrease in the mean frequency of poor shoulder belt fit compared to the no-booster and low-back booster groups. The high-back booster group also exhibited statistically significant decreases in the 90(th) percentile of the absolute value of the relative lateral motion of the head. The low-back booster group did not result in statistically significant decreases in poor shoulder belt fit or lateral head motion compared to the no-booster group. These results are consistent with the presence of large lateral supports of the high-back booster which provided support to the head while sleeping, reducing voluntary lateral occupant motion and improving shoulder belt fit. Future work includes examining lap belt fit in-transit, and examining the effects of these observations on predicted injury risk.