Air Bag Injuries
Over the past several years, there has been a public outcry about the deaths of almost one hundred motorists in low speed motor vehicle collisions as a result of air bags. Children and small adults continue to die because of the violent exposure to inflating air bags. We can and should understand the cause of such tragedies.
Air bag systems were installed in the United States in thousands of automobiles during the model years 1974 through 1976. These air bags were designed and installed in large size vehicles by both General Motors Corporation and Ford Motor Company. At the time, the intent was to provide frontal crash protection for the general population of motorists who, on the whole, were not wearing seat belts. Consequently, the air bags installed in the 1970s were quite large in circumference — occupying fully the entire front of the vehicle from door to door. The very few accident studies of early vintage air bag crashes concluded that these systems were working to minimize injury potential. Those studies were consistent with laboratory testing which demonstrated that these passive restraint systems provided protection in barrier impacts through 30 to 40 mph crash speed range. Publications in recent years have analyzed the field performance of these older systems. Looking just at driver’s side air bag system performance, these authors determined that the system was found to be 21% effective in preventing AIS 3+ injuries, but was -34% ineffective for AIS 2+ passenger injury. Many of the airbag inflation injuries found in the research of the systems performance — as well as the much more recent data obtained since 1989 — occurred in moderate severity crashes without distortion of the occupant compartment. Thus, the deployment of an airbag under some circumstances has the potential to seriously injure or kill, and it does not always depend upon the severity of the crash. As David Viano of the GM Biomedical Science Department stated a few years ago,
“The high energy release of an airbag may injure an occupant against the system at the instant of deployment. Blocking the path of deployment increases pressures in the cushion during gas generation and develops high forces on the occupant. Since the force occurs with high velocity, there is a risk of injury by a Viscous mechanism.”
Public and secret lobbying efforts of the auto industry caused the federal government’s delay of the starting date of mandatory passive restraint criteria, [FMVSS 208] for more than a decade. During this period of time, automobile manufacturers chose not to pursue the mass production of motor vehicles with air bags. In the calendar years 1980 and 1981, Daimler Benz introduced in Europe a test fleet with full frontal protection by air bag restraint. Then in the 1982 model year, Daimler Benz introduced a driver’s side air bag system (along with a manual lap and shoulder belt) in Europe, along with a three point passenger side manual seat belt with a pretensioner retractor. Daimler Benz then introduced air bag systems to the U.S. market in 1984, offering it first as an optional piece of equipment and then it became standard equipment. Chrysler Corporation became the first American manufacturer in the 1980’s to introduce air bags into its vehicles. And, with time, the remaining manufacturers have installed air bags for both driver and passenger positions — as a direct result of the mandatory passive restraint performance criteria adopted by the NHTSA. It is estimated that by the year 2000 there will be over 50 million vehicles on the roads with air bags, and each year there will be literally hundreds of thousands of air bag deployments.
Most of the reported adult injuries and deaths due to air bag deployment involved drivers rather than front seat passengers. In these data there were 16 driver fatalities and 4 passenger fatalities. Of course, the reported fatalities to children provide a different picture. In a four to five year time period, the NHTSA has studied 96 air bag induced deaths to adults and children under the age of nine.
In the fatalities produced, it was observed that a majority of the adult motorists were female and under 50 years of age and unbelted. However, there was no different injury pattern between the belted and unbelted fatalities. Between the two groups, there was a proportionately equal number of deaths due to brain injury and spinal cord trauma. The average crash speed in these deaths and in many of the seriously injured accidents investigated were approximately 12 mph. A majority of the deaths to children over age one occurred in reported instances where the child was unrestrained. Most but not all of the infants who died were seated in the vehicle’s front passenger seat in a rear facing child seat. The risk of injury from an inflating air bag has been a consideration for all occupants for many years.
In recent years, it has been widely agreed that air bag protection is less necessary in low speed collisions. In fact, manufacturers such as Mercedes Benz has designed air bags which deploy at 12 mph delta V if the driver is unbelted and at an 18 mph threshold if the driver is belted. This dual threshold design has been gradually introduced into the American market by other European car companies as well. This staged deployment is perfectly consistent with the published data suggesting that the risk of severe injury does not arise until a delta V of 18 mph.
Old laboratory studies confirmed what we are now seeing in field accidents: “high” loads can be developed on occupants who are within the path of an inflating bag. As in other dynamic circumstances, the risk of injury depends on the system, the environment and the alignment and position of the occupant at the time of bag inflation. Clearly the human body parts at greatest risk are the head, neck and torso because of their (foreseeable) close proximity to the system. In order to minimize the danger of air bag head injury in low speed accidents, car companies like General Motors developed dual deployment air bag systems, which provide for proportioned deployment with the dual deployment of air bags. This system allows for a less violent deployment with a delta V below 18 mph.
Real world “near position” injuries are associated with a wide range of crash severities, but most troubling are those circumstances when the Delta V is below 25 mph, because these are accident circumstances which should, ordinarily, cause little or no serious injury. This exposure to injury occurs under a variety of scenarios, including the driver or passenger who has slumped forward from illness or drowsiness; or moved forward because he or she is not belted, or because a child seat extends almost to the instrument panel, or because of pre-impact braking which moves even the belted occupant forward toward the air bag unit.
Air bag induced injuries are, by the very terms used, injuries caused when an occupant is impacted by an inflating air bag. NHTSA has informed Congress that air bags can have adverse effects for small stature people, older people and out of position children.
A high number of head and neck injuries have been reported in air bag deployments even when the motorist is restrained. The mechanics of this type injury suggest that the seat belted occupant is moving forward in a relatively upright position and coming into contact with the inflating air bag so that the neck is either placed in compression or extension. To minimize seat belt excursion to the “out of position” stage the seat belt must be designed to lock-up when deceleration of the vehicle first begins — through braking — or as a result of occupant movement within the seat belt — by using web sensitive retractors which are tuned to lock up at .35g. Additionally, the environment of the driver’s position needs to be studied to deal with people of small stature. Some possible incremental solutions would include adjustable pedals, a pretensioning retractor and changing the characteristics of deployment — including a reduction of the deployment rate, tethering the bag, and widening its coverage which would also reduce “bag slap.”
If you or someone you love has been hurt by an airbag, contact us for a free review of your case.