Side curtain and torso airbags deployed in the Acura TL and Volvo S60, although the S60’s torso airbag fired too late in the crash to protect the dummy’s chest from potential contact with side structures. One or both of the curtain and torso airbags didn’t deploy in seven of the cars evaluated. Of the six curtains that deployed, four didn’t provide sufficient forward coverage. The Institute lowered restraint and kinematics scores if side airbags didn’t deploy or coverage was lacking. “Side curtain airbags and torso airbags are designed to deploy in side impacts, but they can be beneficial in small overlap frontal crashes as well,” Lund says. “If they do deploy, curtain airbags also need to extend far enough forward to protect the head from contact with side structures and outside objects.”
For example, in the Lincoln MKZ test, the dummy’s head and chest completely missed the front airbag as the steering column moved to the right. The side curtain airbag deployed but didn’t extend far enough forward to protect the dummy’s head. In comparison, the Acura TL’s front and side curtain airbags worked well together to keep the head from coming close to any stiff structures or objects that could cause injury.
Engineers at some manufacturers have indicated that they are adjusting airbag algorithms to deploy side airbags in small overlap frontal crashes. Mercedes, for example, plans changes for the current C-Class. Another restraint and kinematics issue Institute engineers flagged was excessive forward movement of the driver dummy caused by too much shoulder belt webbing spooling out of the retractor. This was the case with the BMW, Mercedes and Volkswagen. Like most new vehicles, these cars have safety belts equipped with load limiters that allow occupants’ upper bodies to move forward in frontal crashes when belt loads exceed a specific threshold. Load limiters allow some belt spoolout after the initial impact to reduce belt- force-related thoracic injuries such as rib fractures by allowing people to ride down deflating front airbags. However, too much spoolout can compromise belt effectiveness by allowing belted occupants to move enough to strike hard surfaces inside the vehicle. This concern is greater in small overlaps where occupants may load only a small part of the front airbag or miss it completely.