An overview of frontal air bag performance with changes in frontal crash-test requirements: findings of the Blue Ribbon Panel for the evaluation of advanced technology air bags

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.

Injury Patterns Sustained in Fatal Motor Vehicle Collisions with Driver's Third-Generation Airbag Deployment

The Office of the Chief Coroner for Ontario database for 2011-2012 was used to compare fatal injury patterns in drivers whose third-generation airbags deployed compared to first- and second-generation airbag deployments and airbag nondeployments with and without seatbelt use. There were 110 frontal and offset frontal crashes analyzed. The small sample size meant that the odds of craniocerebral, cervical spinal, thoracic, and abdominal injuries were not statistically different for airbag generation, deployment status, and seatbelt use; however, the risk of fatal thoracic injuries in third- and second-generation cases was increased. Seatbelt usage in third- and second-generation deployment cases reduced the risk of all injuries except abdominal trauma. High severity impacts and occupant compartment intrusion were frequently observed. The analyses in this retrospective study were challenged by data that were not collated in a standardized way and were limited in details about scene, vehicle, and driver variables.

Airbag deployment-related eye injuries

OBJECTIVE

We studied the correlation between airbag deployment and eye injuries using 2 different data sets.

METHODS

The registry of the Finnish Road Accident (FRA) Investigation Teams was analyzed to study severe head- and eyewear-related injuries. All fatal passenger car or van accidents that occurred during the years 2009-2012 (4 years) were included (n = 734). Cases in which the driver's front airbag was deployed were subjected to analysis (n = 409). To determine the proportion of minor, potentially airbag-related eye injuries, the results were compared to the data for all new eye injury patients (n = 1,151) recorded at the Emergency Clinic of the Helsinki University Eye Hospital (HUEH) during one year, from May 1, 2011, to April 30, 2012.

RESULTS

In the FRA data set, the unbelted drivers showed a significantly higher risk of death (odds ratio [OR] = 5.89, 95% confidence interval [CI], 3.33-10.9, P = 2.6E-12) or of sustaining head injuries (OR = 2.50, 95% CI, 1.59-3.97, P = 3.8E-5). Only 4 of the 1,151 HUEH patients were involved in a passenger car accident. In one of the crashes, the airbag operated, and the belted driver received 2 sutured eye lid wounds and showed conjunctival sugillation. No permanent eye injuries were recorded during the follow-up. The calculated annual airbag-related eye injury incidence was less than 1/1,000,000 people, 4/100,000 accidents, and 4/10,000 injured occupants.

CONCLUSIONS

Airbag-related eye injuries occurred very rarely in car accidents in cases where the occupant survived and the restraint system was appropriately used. Spectacle use did not appear to increase the risk of eye injury in restrained occupants.

Vehicle occupant restraint systems impact on eye injuries: a review

Vehicle occupant trauma to the eyes and associated facial structures has evolved rapidly in conjunction with safety-oriented vehicle design, including restraint systems. Trends vary worldwide with culture, personal factors, vehicle safety equipment, and the traffic environment-including physical, legislative, and enforcement. Wearing safety belts is essential to occupant protection. Airbags were designed as a supplement to protect the head from hard surfaces in frontal crashes, not as a primary countermeasure. Even where vehicle fleets are new with high airbag prevalence, but safety culture and knowledge of restraints is less than robust, injury attributable to not wearing seatbelts is frequent, especially in countries where high-powered vehicles are prevalent. Upper bodies of rapidly forward-moving unrestrained occupants collide with rearward-accelerating airbags. Airbag deployment produces injuries such as corneal abrasions, alkali burns, and the effects of globe compression.

Are airbags a dangerous safety measure? A meta-analysis of the effects of frontal airbags on driver fatalities

A meta-analysis has been conducted of the effectiveness of frontal airbags in reducing driver fatalities, and some potential moderator variables for airbag effectiveness have been investigated. The results confirm the assumption that airbags reduce accident fatalities among belted drivers, but the results are too heterogeneous for drawing conclusions about the size of the overall effect. No support has been found for the hypothesis that airbags increase overall fatality risk, as has been found in the study by Meyer and Finney (Meyer, M., Finney, T., 2005. Who wants Airbags? Chance, 18 (19) 3-16). The results do not seem to be affected by publication bias, and no indications of confounding effects of vehicle characteristics or impact velocity have been found. In frontal collisions belted driver fatalities were found to be reduced by about 22% when all types of airbags are regarded together. The revision of the test criteria for airbags in the USA in 1997 has improved airbag effectiveness. For unbelted drivers airbags are neither effective nor counterproductive, but may increase fatality risk in single vehicle accidents. The results show that there is a lack of knowledge about the effects of airbags in accidents that are not frontal collisions.

Injury risks in frontal crashes by delta V and body region with focus on head injuries in low-speed collisions

PURPOSE

This study investigated injury risks in frontal crashes by belt use and crash severity (delta V) with a focus on studying whether there is a pattern to the crashes causing serious head injuries in low-speed frontal collisions.

METHODS

1996-2007 National Automotive Sample System-Crashworthiness Data System (NASS-CDS) was analyzed for frontal crashes involving front-outboard occupants. Light vehicles were included with model year 1997+. Injuries of maximum severity MAIS 0-6 and fatalities were determined by crash severity and belt. Body region injury (AIS 0-6) was also determined. NASS-CDS electronic cases involving <15 mph crashes were evaluated to determine the crash circumstances causing serious head injury (AIS 3+) in occupants with overall severe injuries (MAIS 4+F).

RESULTS

More than half (51.3%) of belted occupants in 10-15 mph delta V crashes were uninjured compared with 30.2 percent for unbelted occupants. The ratio of the fraction (relative risk) of belted occupants who were uninjured to the fraction of unbelted, uninjured occupants was highest at 3.74 in the 30-35 mph delta V. For 10-15 mph crashes, 0.40 +/- 0.15 percent of unbelted occupants were severely injured (MAIS 4+F) compared to 0.033 +/- 0.009 percent for belted occupants. For 30-35 mph crashes, 8.51 +/- 2.20 percent of unbelted and 5.83 +/- 1.93 percent of belted occupants were severely injured. Overall, seat belt use was 87.4 percent effective in preventing severe injury (MAIS 4+F). The effectiveness decreased with increasing crash severity. The highest relative risk for severe injury of unbelted compared to belted occupants was 12.3 in crashes of 10-15 mph delta V. The relative risk was 8.8 in <10 mph crashes. Overall, the relative risk was 8.0 for severe injury (MAIS 4+F) in frontal crashes. 16.5 +/- 0.98 percent of unbelted occupants experienced serious (AIS 3-6) injury. This risk was 6.49 times greater than the 2.53 +/- 0.10 percent risk with belted occupants. The largest relative risk for serious injury (AIS 3-6) was to the neck (367 times), face (15.5 times) and head (10.2 times).

CONCLUSIONS

The highest relative risk for severe injury of unbelted occupants was in frontal crashes <15 mph. Most of the crashes involved multiple impacts and air bag deployment in the accident sequence. The use of long fill-time side curtains, additional curtain deployment logic, limited deflation front air bags and broader curtain coverage of the front interior may address these injuries.

Front air bag nondeployments in frontal crashes fatal to drivers or right-front passengers

OBJECTIVE

Public concern has arisen about the reliability of front air bags because Fatality Analysis Reporting System (FARS) data indicate many nondeployed air bags in fatal frontal crashes. However, the accuracy of air bag deployment, the variable in question, is uncertain. This study aimed to provide more certain estimates of nondeployment incidence in fatal frontal crashes.

METHODS

Fatally injured passenger vehicle drivers and right-front passengers in frontal crashes were identified in two U.S. databases for calendar years 1998-2006 and model years 1994-2006: FARS, a census of police-reported fatal crashes on public roads, and National Automotive Sampling System/Crashworthiness Data System (NASS/CDS), a probability sample of tow-away crashes. NASS/CDS contains subsets of fatal crashes in FARS and collects detailed data using crash investigators. Front air bag deployment coding for front-seat occupant fatalities was compared in FARS and NASS/CDS, and case reviews were conducted.

RESULTS

Among FARS frontal deaths with available deployment status (N = 43,169), front air bags were coded as not deployed for 18 percent of front occupants. In comparison, NASS/CDS (N = 628) reported 9 percent (weighted estimate) nondeployment among front occupants killed. Among crashes common to both databases, NASS/CDS reported deployments for 45 percent of front occupant deaths for which FARS had coded nondeployments. Detailed case reviews of NASS/CDS crashes indicated highly accurate coding for deployment status. Based on this case review, 8 percent (weighted estimate) of front occupant deaths in frontal crashes appeared to involve air bag nondeployments; 1-2 percent of front occupant deaths represented potential system failures where deployments would have been expected. Air bag deployments appeared unwarranted in most nondeployments based on crash characteristics.

DISCUSSION

FARS data overstate the magnitude of the problem of air bag deployment failures; steps should be taken to improve coding. There are inherent uncertainties in judgments about whether or not air bags would be expected to deploy in some crashes. Continued monitoring of air bag performance is warranted.

Improving traffic safety: conceptual considerations for successful action

INTRODUCTION

In the early stages of motorization, it did not take rigorous scientific research to achieve major improvements in traffic safety. Instead, early traffic-safety countermeasures were often based exclusively on common sense. Since then, scientific research has gradually increased in importance as the basis for developing successful interventions. This shift was not made by choice but mostly by necessity: many of the "easy" problems have already been addressed, and the remaining problems are generally too complex for an approach based solely on common sense. Fortunately, our understanding of the complexities involved in traffic safety has recently made major gains, and common sense can now be supplemented, to some degree, by valid technical analysis.

APPROACH

This article discusses major conceptual issues that should be considered in guiding the future development of effective, science-based traffic-safety countermeasures.

IMPACT ON INDUSTRY

After briefly discussing the conceptual issues, the article offers a list of implications for action.