History of airbag safety benefits and risks.

Objective: The history of airbags was reviewed for benefits and risks as they became a supplement to lap-shoulder belts. Sled and crash tests were evaluated and field data was analyzed for airbag effectiveness. Field data on airbag deaths and studies on mechanisms of deployment injury were analyzed. The history was reviewed as airbags evolved from the early 1970s to today.

Methods: Airbag benefits were determined from NHTSA crash tests with unbelted and belted dummies in 40, 48, and 56 km/h (25, 30, and 35 mph) frontal impacts with and without airbags. The literature was reviewed for testing of passive restraints with and without airbags. Recent NCAP tests were compared with earlier tests to determine the change in occupant responses with seatbelts and supplemental airbags in modern vehicles. 1994-2015 NASS-CDS field data was analyzed for MAIS 4 + F injury. Risks were compared for belted and unbelted occupants in frontal impacts by delta V. Airbag risks were identified from field deployments and research. The 1973-76 GM fleet had two deaths due to the occupant being out-of-position (OOP). The mechanisms of injury were determined. From 1989-2003, NHTSA investigated 93 driver, 184 child passenger, and 13 adult passenger airbag deaths. The data was reviewed for injury mechanisms. Second generation airbags essentially eliminated OOP airbag deaths. More recently, three suppliers were linked to airbag rupture deaths. The circumstances for ruptures were reviewed.

Results: The risk for serious head injury was 5.495% in drivers and 4.435% passengers in 40-48 km/h (25-30 mph) frontal crash tests without belts or airbags. It was 80.5% lower at 1.073% in drivers and 82.0% at 0.797% in passengers with belts and airbags in 35 mph NCAP crash tests of 2012-20 MY vehicles. NASS-CDS field data showed a 15.45% risk for severe injury (MAIS 4 + F) to unbelted occupants and 4.68% with belted occupants in 30-35 mph frontal crash delta V with airbags, as deployed. The reduction in risk was 69.7% with belt use and airbags deploying in 96.1% of crashes. There were benefits over the range of delta V. Two airbag deaths were studied from the 1970s GM fleet of airbags. The unbelted driver death was caused by punchout force with the airbag cover blocked by the occupant and membrane forces as the airbag wrapped around the head, neck or chest with the occupant close to the inflating airbag. The unbelted child death was from airbag inflation forces from pre-impact braking causing the child to slide forward into the deploying airbag. Research showed that unrestrained children may have 13 different positions near the passenger airbag at deployment. NHTSA investigation of first generation airbag deaths found most driver deaths were females (75.3%) sitting forward on the seat track, close to the driver airbag. Seatbelt use was only 30%. Most child deaths (138, 75.4%) involved no or improper use of the lap-shoulder belts. Of these, 115 deaths involved pre-impact braking. Only 37 (20.2%) children were in child seats with 29 in rear-facing and 8 in forward-facing child seats. Eight child deaths (4.4%) occurred with lap-shoulder belt use. Airbag designs changed. More recently, Takata airbags were related to at least 24 deaths by airbag rupture prompting a recall; the successor company Joyson had an airbag recall. ARC airbags have experienced a chunk of the inflator propelled into the driver during deployment with several deaths leading to a recall.

Conclusions: Airbags are effective in preventing death and injury in crashes. They provide the greatest protection in combination with seatbelt use. NHTSA estimated airbags saved 28,244 lives through 1-1-09 while causing at least 320 deployment deaths, which has prompted improved designs, testing, and recalls.