Effects of Crash Pulse, Impact Angle, Occupant Size, Front Seat Location, and Restraint System on Rear Seat Occupant Protection

In this study, two sled series were conducted with a sled buck representing a compact vehicle. The first series of tests focused on the effects of crash pulse, impact angle, occupant size, and front seat location on rear seat occupant restraint with a generic rear-seat belt system without pre-tensioner or load limiter. The second series of tests focused on investigating the benefit of using advanced features for rear-seat occupant restraint in the most severe crash condition in the first sled series. The first series of tests include 16 test conditions with two impact angles (0° and 15°), two sled pulse (soft and severe), and four ATD sizes (HIII 6YO, HIII 5th female, HIII 95th male, and THOR-NT) with two ATDs in each test. The driver seat was located at the mid position, while the front passenger seat was positioned such that a constant distance between the ATD knee and the front seat is achieved. In all the tests, a generic rear-seat belt system without pre-tensioner, load limiter or dynamic locking tongue (DLT) was used. Test results from the first sled series showed that crash pulse and occupant size are the two dominating factors affecting the ATD kinematics and injury measurements, while impact angle and front-seat location are not statistically significant. Although no head-to-front-seat contact occurred in any of the tests, in general, the severe crash pulse would result in chest deflections over the injury criteria for adult ATDs with higher ATD excursions than for the soft crash pulse. These results are consistent to those from the field data in that chest injuries are the most common injuries in rear-seat adult occupants. The HIII 6YO ATD sustained submarining kinematics in all the tests due to the slouching pre-crash posture. In an attempt to help further reduce the chest loading while managing the head excursion, 3-point belts with pre-tensioner and load limiter, 4-point belts, DLT, inflatable belts, Bag in Roof (BiR) concept, and Self Conforming Rear-seat Air Bag (SCaRAB) concept were investigated in the second series of sled tests, in which only the most severe testing condition (0° and severe pulse) in the first sled series was used. Reductions in occupant loading were shown with these advanced restraint systems, especially the airbag features, to help reduce head, neck, and chest injury measures for rear-seat occupants. This study demonstrated the importance of considering the effects of occupant size and crash pulse on rear-seat occupant protection. Advanced restraint systems including features such as a pre-tensioner, a load limiter, and an airbag, may have the potential to help provide additional protection for rear-seat occupants with diverse occupant sizes.