Objective:​ This study analyzed matched rear sled tests with all belts to seat (ABTS) and conventional seats from the same vehicle model to determine differences in BioRID IIg dummy responses.

Methods:​ The BioRID IIg rear impact dummy was placed on ABTS or conventional seats and subjected to 10 mph rear sled tests using the Insurance Institute for Highway Safety (IIHS) whiplash assessment protocol. Measurements in the dummy included head and pelvis triaxial accelerations, T1 and L1 biaxial accelerations, and upper and lower neck triaxial forces and moments. High-speed video captured the dummy and seat kinematics during seat loading and rebound into the lap–shoulder belts. Four vehicles were available with conventional and ABTS seats in the same model. They were the 2007–2008 Chrysler Sebring, 2006 Ford F-150, 2005–2007 Saab 9-3, and 2006–2007 BMW 3 series. Confidence intervals were used to determine significant differences between the matched ABTS and conventional seat responses.

Results:​ Ten sled tests were available for the 4 vehicle models with ABTS and conventional seats. The upper neck rearward shear force was 75 percent higher (range 17%–156%, P < .05) in the matched ABTS compared to conventional seats. The upper neck tension was 44 percent higher (range 24%–94%, P < .05) and the lower neck extension moment was 102 percent higher (range 38%–187%, P < .05). The Saab 9-3 responses were lower than the 3 other vehicles for both the conventional and ABTS seats. There was less rearward shear and extension of the neck in the Saab seats.

Conclusions:​ The tests show that ABTS seats involved significantly higher neck tensions, rearward shear forces, and extension moments than matched conventional seats. Overall, ABTS seats applied more load on the head and spine, had less control of neck kinematics, and had higher risks for whiplash and more severe injury than conventional seats in the same vehicle model.