Standard No. 208 has long required vehicles to meet specified injury criteria, including criteria for the head and chest, measured on 50th percentile adult male test dummies during a rigid barrier crash test at any speed up to 48 km/h (30 mph) and over the range of angles from -30 degrees to + 30 degrees. The standard has required air-bag-equipped vehicles to meet the criteria both with the dummies belted and unbelted.
If a vehicle crash test is to measure the overall ability of a vehicle and its occupant protection system to prevent fatalities and serious injuries, the crash test must have the severity of a potentially fatal crash. It is also important that the crash test make it necessary for vehicle manufacturers to design and equip their vehicles so that they provide protection in a range of potentially fatal crashes, recognizing that no single type of crash test can be directly representative of all the myriad potentially fatal crashes that occur in the real world.
The longstanding barrier test requirement specified in Standard No. 208 simulates a wide range of potentially fatal crashes, both with respect to severity and crash pulse. The test is conducted at any speed up to 48 km/h (30 mph), meaning that protection must be provided at all such speeds, e.g., 32 km/h (20 mph) and 40 km/h (25 mph), as well as 48 km/h (30 mph). The test is also conducted at any angle between 30 degrees to the left and 30 degrees to the right. While the perpendicular rigid barrier test results in crash pulses of short duration, e.g., the kind of pulse that a vehicle experiences when it strikes a bridge abutment or fully engages another similar-sized or larger vehicle directly head-on, the angled rigid barrier tests result in crash pulses of longer duration, i.e., a softer crash pulse.
The rigid barrier test requirements have been an integral part of the standard's automatic crash protection requirements and have resulted in enormous savings of lives. As noted above, NHTSA estimates that air bags have saved about 3,148 drivers and passengers. Of these, 2,725 were unbelted and 423 were belted. If these levels of effectiveness are maintained, i.e., 21 percent in frontal crashes for restrained occupants and 34 percent in frontal crashes for unrestrained occupants, air bags will save more than 3,000 lives each year in passenger cars and light trucks when all light vehicles on the road are equipped with dual air bags. Standard No. 208's current requirements thus represent one of NHTSA's most effective regulations in terms of the numbers of lives saved.
As also noted earlier in this notice, the agency amended Standard No. 208 in March 1997 to provide a temporary option for manufacturers to certify their vehicles to an unbelted sled test as an alternative to the unbelted barrier test requirement. NHTSA established the sled test option to ensure that the vehicle manufacturers could quickly depower all air bags so that they inflate less aggressively.(19) While vehicle manufacturers could have depowered many or most of their vehicles' air bags without changes to Standard No. 208, the final rule expedited this process.
Under the March 1997 final rule, the sled test option was scheduled to terminate on September 1, 2001. The agency explained that there was no need to permanently reduce Standard No. 208's performance requirements to enable manufacturers to fully address the adverse effects of air bags. This is because there were various alternatives already allowed by the standard to address the problem that did not necessitate reducing the standard's performance requirements. While the agency specified a several year duration for the alternative sled test, it indicated that it would revisit the end date, to the extent appropriate, in its future rulemaking on advanced air bags. See 62 FR 12968; March 19, 1997.
The September 1, 2001 termination date for the sled test option has been superseded by the NHTSA Reauthorization Act of 1998. In a paragraph titled "Coordination of Effective Dates," the Act provides that the unbelted sled test option "shall remain in effect unless and until changed by [the final rule for advanced air bags]." The Conference Report states that the current sled test certification option remains in effect "unless and until phased out according to the schedule in the final rule."
In light of the Act, the agency is proposing to phase out the sled test option as the requirements for advanced air bags are phased in. While NHTSA believes the sled test option has been an expedient and useful temporary measure to ensure that the vehicle manufacturers could quickly depower all of their air bags and to help ensure that some protection would continue to be provided, the agency does not consider sled testing to be an adequate long-term means of assessing the extent of occupant protection that a vehicle and its air bag will afford occupants in the real world. The sled test, first, excludes vehicle factors that can significantly affect the level of protection received in the real world and, second, is insufficiently representative of potentially fatal real world crashes.
Unlike a full scale vehicle crash test, a sled test does not, and cannot, measure the actual protection an occupant will receive in a crash. The current sled test measures limited performance attributes of the air bag, but cannot measure the performance provided by the vehicle structure in combination with the air bags or even the full air bag system by itself.
Among other shortcomings, the sled test does not evaluate the actual timing of air bag deployment. Deployment timing is a critical component of the safety afforded by an air bag. If the air bag deploys too late, the occupant may already have struck the interior of the vehicle before deployment begins.
Air bag timing is affected by parts of the air bag system which are not tested during a sled test, i.e., the crash sensors and computer crash algorithm. A barrier crash test evaluates the ability of sensors to detect a crash and the ability of an algorithm to predict, on the basis of initial sensing of the rate of increase in force levels, whether crash forces will reach levels high enough to warrant deployment. However, the sled test does not evaluate these critical factors. The ability of an algorithm to correctly, and quickly, predict serious crashes is critical. The signal for an air bag to deploy must come very early in a crash, when the crash forces are just beginning to be sensed by the air bag system. A delay in an air bag's deployment could mean that the air bag deploys too late to provide any protection. In a sled test, the air bag is artificially deployed at a predetermined time. The time of deployment in a sled test is artificial and may differ significantly from the time when the air bag would deploy during an actual crash involving the same vehicle.
Second, the current generic sled pulse does not replicate the actual crash pulse of a particular vehicle model, i.e., the specific manner in which the front of the vehicle deforms during a crash, thereby absorbing energy. The actual crash pulse of a vehicle is a critical factor in occupant protection. A crash pulse affects the timing of air bag deployment and the ability of an air bag to cushion and protect an occupant. However, the current sled test does not use the crash pulse of the vehicle being tested. In many cases, the crash pulse used in the sled test is not even one approximately representative of the test vehicle. The sled test uses the crash pulse of a large passenger car for all vehicles, regardless of their type or size. This crash pulse is appropriate for large passenger cars, but not for light trucks and smaller cars since they typically have much "stiffer" crash pulses than that of the sled test. In the real world, deceleration of light trucks and smaller cars, and their occupants, occurs more quickly than is simulated by the sled test. Thus, the sled test results may overstate the level of occupant protection that would be provided by a vehicle and its air bag system in the real world. An air bag that can open in a timely fashion and provide adequate cushioning in a soft pulse crash may not be able to do so in a stiffer pulse crash. This is because an occupant of a crashing vehicle moves forward, relative to the vehicle, more quickly in stiffer pulse crash than in a softer pulse crash.
Third, a sled test does not measure the potential for harm from vehicle components that are pushed back into the occupant compartment during a crash. Examples of components that may intrude into the occupant compartment include the steering wheel, an A-pillar and the toe-board. Since a sled test does not involve any kind of crash or deformation of the vehicle, it implicitly assumes that such intrusion does not occur in crashes. Thus, the sled test may indicate that a vehicle provides good protection when, as a result of steering wheel or other intrusion in a real world, the vehicle will actually provide poor protection in a real world crash.
Fourth, the sled test does not measure how a vehicle performs in angled crashes. It only tests vehicles in a perpendicular crash. In the real world, frontal crashes occur at varying angles, resulting in occupants moving toward the steering wheel and instrument panel in a variety of trajectories. The specification of angled tests in conjunction with the barrier test requirement ensures that a vehicle is tested under these real world conditions.
As noted below in the appendix to this preamble, NHTSA received several petitions for reconsideration concerning the sled test's sunset date (subsequently superseded by the NHTSA Reauthorization Act of 1998). The agency notes that its proposal to phase the option out as the requirements for advanced air bags are phased in will provide additional time for the vehicle manufacturers to redesign their air bags to avoid causing harm and to provide improved protection for all occupants, belted and unbelted. In the appendix, the agency provides additional reasons supporting its proposal for terminating the sled test option, including a discussion of the importance for safety of maintaining effective unbelted frontal crash test requirements.
NHTSA is requesting comments on whether it should develop potential alternative unbelted crash test requirements. The auto industry and other parties have raised a number of objections to the existing unbelted barrier test requirements. NHTSA is willing to consider alternatives and to that end is placing a technical paper on this subject in the docket. Among other things, the paper compares the existing rigid barrier test to tests using a stationary deformable barrier and a movable deformable barrier.
With respect to the current barrier test requirements, and as discussed later in this notice in a section titled "Injury Criteria," the agency is proposing to upgrade the standard's chest injury criteria and to add neck injury criteria. NHTSA notes that, as part of developing this proposal for advanced air bags, it considered the latest available information concerning injury criteria for both the existing 50th percentile adult male dummy and for each of the proposed new dummies. The agency is placing in the public docket a technical paper which explains the basis for each of the proposed injury criteria and the proposed performance limits.
NHTSA is also proposing to include, for all crash tests specified by Standard No. 208, certain vehicle integrity requirements. These requirements would specify that vehicle doors may not open during the crash test. For many years the agency has monitored whether doors open during 30 mph frontal barrier crash tests. In the agency's experience, doors remain closed in these crash tests. Since vehicles already can and do comply with this requirement, this proposal would establish this norm as a minimum level of safety. This requirement would support the agency goal of mitigating the fatalities and serious injuries attributable to complete and partial ejections.
This proposal would also specify that, after crash testing, vehicles having a roof of rigid construction (i.e., vehicles other than convertibles), must meet the following requirements. It must be possible, without the use of tools, to open at least one door, if there is one, per each row of seats. Further, where there is no such door, it must be possible to move the seats or tilt their backrests as necessary to allow the evacuation of all the occupants. This post crash door opening check has always been a demonstration part of the agency's compliance test procedure. The purpose is to demonstrate the potential for entrapment. After each test, the technicians approach the vehicle and try to open the vehicle doors. In the majority of these full frontal crash tests conducted by the agency, the technicians are able to open the vehicle doors without the use of tools. This process is recorded on the test films. The agency is proposing to add this door opening requirement to the regulation. NHTSA does not have any information indicating that there would anything other than a minimal cost impact associated with this proposed requirement, but requests comments on this issue.
