The purpose of this conceptual study is to address the increasing number of fatalities and severe injuries in vehicle rollovers. A restraint concept for reducing Head and Neck loading by hard contact with the roof of the car has been developed to reduce and/or mitigate these injuries.
The human neck is capable of sustaining higher loads when it is in flexion (e.g. the head is bent forward). Therefore, moving the occupant’s head to a bent forward position using a slowly deploying airbag is proposed.
The Roofbag concept includes a slide chamber and support chamber. Together, they form a multichamber airbag which is mounted at the top of the seat back. The inflator has an extremely slow onset, causing the airbag to deploy in about 250ms. When the slide chamber is inflated, it positions itself behind and above the occupant’s head. The support chamber pushes the slide chamber forward, causing the occupant’s head to bend forward.
Three advantages for this concept have been identified: the occupant’s neck can sustain higher bending loads when positioned in flexion; a cushion is positioned between the occupant’s head and the roof; the survival space between the head and the roof is increased.
A series of rollover tests (SAEJ2114, Curb Trip) using HIII dummies were performed to understand and demonstrate the benefits of this concept. The results show a significant reduction in head and neck injuries when the Roofbag concept is employed. Out-of-position tests show low-to-medium level loadings.
Further potential benefit could possibly result from expanding the Roofbag concept to other applications, such as head protection for convertibles or neck protection during rear impact.