During the last round of federal rulemaking on advanced airbags, one issue sparked intense controversy — the National Highway Traffic Safety Administration's (NHTSA) decision to go with a speed of 25 mph instead of 30 mph in rigid-barrier compliance testing with unbelted adult male dummies. Since the advanced airbag standard was issued in 2000, the debate hasn't quieted. It has simply moved to a federal court.
Together with The Trauma Foundation, Public Citizen and the Center for Auto Safety have asked a federal court to review NHTSA's test speed decision, claiming that conducting unbelted tests at the lower speed of 25 mph "could result in hundreds of additional fatalities from automotive collisions" because of inadequate airbag protection. Tests at 30 mph are warranted, these parties told the court in a brief filed last October, because so many deaths occur in crashes at this speed or more.
The crux of the issue is whether conducting the tests at 30 mph will increase occupant protection by ensuring that more people are protected by airbags in higher speed crashes, as Public Citizen argues, or whether 25 mph testing will produce airbags that are just as effective in real-world crashes but pose much less risk of inflation injury to out-of-position occupants.
A 25 mph test speed allows automakers to continue designing airbags with power levels that keep the risks low from inflating airbags. Serious injuries from inflating bags have plummeted since automakers began depowering airbags in the mid- to late-1990s (see "Airbag risk is reduced in newest vehicles," April 6, 2002).
In response to Public Citizen, NHTSA told the court in a brief filed in January that "[s]peed is not the only component of occupant protection testing ... . Petitioners miss the point by suggesting that the only difference between the [old airbag standard] and the new standard is the maximum speed of the unbelted barrier test. That was only one of many changes, and ... the overall interests of safety favored the new unbelted test" at 25 mph.
From the start of the debate about testing at 25 versus 30 mph, the Institute and others have disagreed with Public Citizen. "We firmly believe NHTSA made the right decision," the Institute said in 2000 (see Status Report special issue: new federal airbag rule, June 17, 2000).
More recently the Institute weighed in again, telling the court it was misleading of Public Citizen to claim that more than half of all deaths occur in crashes at speeds faster than 30 mph. The implication is that 30 mph testing can assure occupant protection only in crashes up to about 30 mph and not in higher speed impacts.
This is incorrect, the Institute told the court. A 30 mph crash test into a rigid barrier is more severe than almost all 30 mph crashes that occur in the real world. The test produces occupant decelerations that are much higher. This is because deceleration (a better indicator of injury risk than crash speed) is determined by both the change in speed that occurs during a crash and the time over which the change occurs. A 30 mph rigid-barrier test occurs over a much shorter duration than most real-world crashes at the same speed, so the occupant decelerations are much higher in the test. Thus, a 25 mph rigid-barrier test is more severe, as measured by occupant decelerations, than most real-world crashes.
Another factor ignored by Public Citizen is that conducting tests at higher speeds doesn't automatically result in better occupant protection in real-world crashes. "The higher the test speed, the greater is the force level that is needed to quickly inflate airbags ... . [A]n airbag with the inflation forces needed to restrain an unbelted crash test dummy at a high speed is likely to injure a person who is very close to the bag when it first begins to inflate," the Institute told the court.
Concluding that "[t]he true consequences of a return to a 30 mph rigid-barrier test ... is a probable increase in airbag power, which would pose additional risks," the Institute asked the court to let NHTSA's decision stand.
Auto manufacturers' responses
The Alliance of Automobile Manufacturers and Automotive Occupant Restraints Council told the court that NHTSA isn't obligated to assume "a monocular focus on safety improvements for 50th percentile unbelted males," adding that the new airbag requirements "ensure an improvement in overall occupant safety," including protection for adult males.
Another industry trade group, the Association of International Automobile Manufacturers, addressed the same issue. Available information on crashes involving the depowered airbags allowed under the new testing rules shows "these airbags have been substantially less aggressive to occupants than previous airbags, yet provide the same or virtually the same level of protection to occupants of various sizes," this group said.