title: Occupant restraint in the rear seat: ATD responses to standard and pre-tensioning, force-limiting belt restraints.
abstract: Recent studies have shown that restrained occupants over the age of 50 in frontal crashes have a higher risk of injury in the rear seat than in the front, and have hypothesized that the incorporation of technology such as belt pre-tensioning and force limiting preferentially in the front seat is at least partially responsible for this trend. This study investigates the potential benefits and trade-offs of seat belt pretensioners and force-limiters in the rear seat using a series of frontal impact sled tests at two speeds (48 km/h and 29 km/h DeltaV) with a buck representing the interior of the reat seat occupant compartment of a contemporary mid-sized sedan. Four different dummies were tested: the Hybrid III six year old (in a booster seat, H3 6YO), the Hybrid III 5(th) percentile female (H3 AF05), the Hybrid III 50(th) percentile male (H3 AM50), and the THOR-NT. The restraints consisted of either a standard three point belt, or a 3-point belt with a retractor pretensioner and a progressive force-limiter (FL+PT). Each test condition was repeated in triplicate. The FL+PT restraints (compared to the standard restraints) resulted in a significant (p < or = 0.05) decrease in peak internal chest deflection for each of the Hybrid III dummies at both test speeds (48 km/h: 29% decrease for H3 6YO, 38% decrease for H3 AF05, 30% decrease for H3 AM50), and for the THOR-NT at a DeltaV of 29 km/h. At 48 km/h, the FL+PT restraint qualitatively decreased the average peak internal chest deflection of the THOR-NT, however this decrease was not statistically significant (p=0.06). Furthermore, the FL+PT system allowed little or no increase in forward head excursion, and improved whole-body kinematics for all dummies by restricting pelvic excursion and slightly increasing torso pitch. The results suggest that the FL+PT system studied here may provide injury-reducing benefit to rear seat occupants in moderate to high severity frontal crashes, although more study is needed to evaluate these restraints in other crash scenarios.
authors.affiliation: University of Virginia, Center for Applied Biomechanics, Charlottesville, VA, USA.
authors.forename: Jason
authors.initials: J
authors.lastname: Forman
authors.forename: Jarett
authors.initials: J
authors.lastname: Michaelson
authors.forename: Richard
authors.initials: R
authors.lastname: Kent
authors.forename: Shashi
authors.initials: S
authors.lastname: Kuppa
authors.forename: Ola
authors.initials: O
authors.lastname: Bostrom
mesh_terms: D000063:Accidents, Traffic; D000328:Adult; D001336:Automobiles; D002648:Child; D004867:Equipment Design; D005260:Female; D006801:Humans; D008297:Male; D008348:Manikins; D008954:Models, Biological; D012622:Seat Belts; D013314:Stress, Mechanical; D014947:Wounds and Injuries / Q000209:etiology / Q000517:prevention & control*