Assessment of a Pre-crash Seatbelt Technology in Frontal Impacts by Using a New Crash Test Sled System with Controllable Pre-impact Braking

The objective of this study is to develop a new method and tools required for the evaluation of the potential benefits of pre-impact safety restraint systems. A pre-crash sled system that can reproduce controlled pre-impact braking in combination with a variety of crash pulses was built. The sled can be customized from existing vehicles to examine a variety of restraint systems. In addition, a previously validated 50th percentile male Hybrid III dummy with a modified lumbar was employed to reconstruct realistic driver’s posture changes at the pre-impact braking phase. In order to evaluate the potential benefits of a pre-crash seatbelt (PSB), the modified dummy was placed on the sled with a standard seating posture and restrained by either a conventional seatbelt (SB) or a PSB controlled by a motor in the retractor. The sled system was then programmed to reach a steady speed of 64 km/h, followed by a 0.8 g deceleration and 0.8 seconds of duration, just before colliding against the barrier at the speed of 48 km/h. Increased forward travelling of the upper body at the pre-impact braking phase with the SB was measured in comparison to the PSB case. In the PSB case, full airbag deployment occurred before body-to-airbag contact, allowing the airbag in coordination with the belt to mitigate the neck loading optimally and to reduce a 15% of chest acceleration. In the SB case, body-to-airbag contact occurred before its complete deployment, causing increased neck forces and moments as well as chest acceleration. In contrast, equivalent chest deflections for both types of seatbelts were measured. In this research, a new pre-crash sled system with the potential to evaluate pre-crash safety restraint systems was developed. Crash tests with dummies were conducted in order to examine the effectiveness of a PSB. By controlling the posture change during an emergency braking, the reduction of neck and chest injury risk in front impacts was achieved. This confirms the potential of a PSB to enhance occupant protection.