In this article:
Injuries Caused By Occupant Restraints
By design, occupant restraint systems, air bags, and seat belts are intended to protect occupants from harm and injury. What happens when these designs fail to do the job they were intended, or offer less protection to certain size occupants? The following is a brief look at some of the current issues and failures with restraint designs.
Seat Belts
Most seat belts were designed for adults, more specifically, 50th percentile adult males. Appropriate fit for small-stature occupants and children who have outgrown child and booster seats is particularly problematic. Poor seat belt fit can cause discomfort and may result in nonuse or misuse. Common misuse includes placing the shoulder portion of the belt under the arm or behind the back when the webbing abrades the neck or fits uncomfortably across women's breasts.Eliminating upper torso restraint creates the same dangers found with lap-only belts--lumbar spine and abdominal injuries.
Even if a small occupant wears the lap/shoulder belt, injuries can occur as a result of poor fit. The lap portion of the belt can ride up above the pelvis causing the occupant to "submarine" or slide under the webbing, resulting in abdominal injuries and neck injuries from the shoulder portion of the belt as it catches under the occupants' chin. Neck injuries typically include upper cervical spine fractures and dislocations, which can be fatal or cause total paralysis.
Remedies to poorly fitting seat belts include adjustable upper anchorages and seat-mounted belt systems. Despite years of proposed rulemaking and petitions, the National Highway Traffic Safety Administration (NHTSA) rules for seat belt fit did not require these designs until recently. After a Congressional mandate NHTSA, in 1992, finally proposed rules for belt comfort and convenience that eventually led to a requirement that lap/shoulder belts offer 5 centimeters of adjustment in the shoulder belt or that the belts be integrated into the seats. The rule became effective for vehicles built after September 1, 1997.
While no requirement was in place prior to 1997, adjustable anchorages were fitted in a number of manufacturers' vehicles as early as the mid-1980s. Some models sold in overseas markets were equipped with adjustable anchors although U.S. market counterparts were not.
Proper fit of traditional vehicle-mounted shoulder belts depends largely on the adjustment of the seat and location of the anchorage. Seat-mounted belts provide improved geometry and fit because all of the anchor points move with the seat as it is adjusted providing optimized protection. Despite having been built and tested seat integrated belts or "All Belts to Seats" in the 1960s and 1970s these designs did not make there way into production vehicles until 1990 and they were relegated to a few expensive luxury and sport models. Beginning in 1995, Ford fitted seat-integrated seat belts in all seating positions of its European 15-passenger van and for the 1996 model year Chrysler produced the first mass-market vehicle for the U.S. with this safety feature. GM and other manufactures have followed suit.
Air Bags
Injuries from air bags are most commonly caused by designs that inflate too aggressively, in low-speed, low-energy collisions, or when they inflate late in the crash scenario.
The industry claims that federal rules forced aggressive air bags into the market. However, government rules have always allowed less aggressive designs, and recent testing has demonstrated that under these rules less aggressive air bag designs provided the necessary protection to meet mandated minimum safety levels. Although there has always been flexibility in the standard, under industry pressure NHTSA recently amended requirements making them more lenient. The change in the rule led manufacturers to "depower" or reduce the inflation aggressively in some 1998 and later models even though these changes were always allowed. Depowered air bags are frequently called "second generation" or "Gen2" designs.
Aggressive air bags injure both belted and unbelted occupants. Short-stature drivers are at the greatest risk because of their proximity to the air bag module. Seat belts provide little or no protection to these vulnerable occupants because they are in the air bag inflation zone. Larger occupants are generally at less risk because they tend to position themselves further from the air bag. Preimpact braking and certain collision types will put the occupant into the inflation zone regardless of whether the belt is worn. The ability of the occupant to move forward is also related to the seat belt system and whether it adequately prevents too much forward movement.
The aggressivity of air bags can and has been addressed with various design features including: tethers to reduce the initial deployment force; fold patterns that control deployment direction and speed; dual-stage inflators that allow the bag to deploy less aggressively at low speeds and more aggressively in high-speed crashes; seat belt sensors that detect usage and adjust deployment accordingly; and devices that keep occupants away from the deploying bag such as adjustable foot pedals.
Many of the serious injuries and fatalities that result from air bags occur at speeds in which the change in velocity is less than 12 mph or from underbody impacts. In low-speed or underbody impacts, if the air bag does not deploy, occupants are unlikely to be injured. Deployments in low-speed and underbody impacts are the result of poor sensor design, location, or defects. Additionally, poor software design can also contribute to these types of deployments. A significant number of recalls have been issued to remedy inappropriate deployment problems.
Recent testing has alerted the safety community to yet another air bag problem--delayed deployment. Delayed deployment allows occupants to move into close proximity to the air bag module and into the inflation zone during the crash scenario creating the same types of injuries seen with short-stature occupants. Delayed deployment can cause injuries to occupants even in vehicles with the new depowered air bags. Delayed deployment can occur in collisions in which the energy is absorbed in part by the struck object. These crash types create a "softer" impact which sensor designs fail to discriminate early enough to initiate timely air bag deployment. The lack of forward sensors and inadequate sensor design are contributing factors to this problem.
Injuries from air bags include skull fracture and brain injury when an occupant's head is struck by the deploying air bag. Eye injuries and facial fractures also occur. There are two types of neck injuries commonly associated with air bag deployment. Toward the end of the air bag inflation cycle, the bag can gather under the occupant's chin pushing the head upward and rearward, which can cause skull dislocation relative to the first cervical vertebrae and is almost always fatal. Neck extension injuries can also occur when the occupant's head is pushed rearward. Chest injuries are caused when the torso is close to or up against the air bag module during deployment. Deployment forces can cause sternum and rib fractures, lung and heart contusions, and heart lacerations. Serious upper-extremity injuries also occur when an arm is in front of the air bag module. These injuries are often severe enough to result in the loss of use.
Despite the significant and obvious advantages offered by seat belts and air bags, poor designs can contribute to injuries. In many instances these designs could have been improved without costly remedies. A close examination of the vehicle(s), scene, collision facts, and injuries is necessary to determine whether an occupant's injury is the result of a restraint system.
Seat Belt Adjuster Warning
In an attempt to provide children with more comfortable belt fit, parents commonly purchase aftermarket seat belt adjusters. These adjusters lower the shoulder belt in an effort to move the webbing off of the occupant's neck; however, they can also cause the lap belt to rise above a child's hips, increasing the potential for abdominal injury. These products do not have to meet federal safety requirements and testing their efficacy is difficult because there are no abdominal sensors or corresponding injury criteria for child dummies used in government compliance testing. The federal government recently proposed that the manufacturers of seat belt adjusters be required to warn that the devices are not to be used by young or small children.
Takata TK52 Seat Belt Buckle Failures
Millions of vehicles built during the mid-1980s through the 1990s were equipped with Takata TK52 series seat belt buckles that may unlatch in a collision. In addition, many of these buckles may fail to latch leaving the occupant without a usable restraint. After one of the largest ever recall campaigns to remedy TK52 buckle defects, questions about their performance still remain.
Takata TK52 series buckles were investigated by the National Highway Traffic Safety Administration (NHTSA) beginning in 1994 because of failure to latch, unlatch, or to inadvertently unlatch. The investigation was initiated based on a Honda service bulletin that contained defect codes for buckles binding and failing to engage and disengage, as well as 12 consumer complaints of buckle failures. Shortly after opening a low-level inquiry into Honda buckles, the agency upgraded and expanded its investigations to include buckle supplier Takata and began separate inquiries into Suzuki, Isuzu, Daihatsu, Subaru, Mitsubishi, Nissan, Mazda, and GM models that used the TK52 buckle. Throughout the NHTSA investigations, some manufacturers placed the blame on consumers claiming that Americans commonly eat and drink in their vehicles and spilling food and drinks in the buckles created contamination, which was at least partially responsible for the buckle failure problems.
The investigations eventually led to "voluntary" recalls from the above manufacturers and Ford and Chrysler who sold vehicles with TK52 buckles. The recalls all cite the same defect--the ABS plastic release button can break and cause the buckle to fail. Manufacturers claimed that buckle unlatching in a collision could not occur despite owner claims to the contrary. Furthermore, manufacturers argued that the defect was not safety related despite agreeing to recall the subject vehicles. Depending on the vehicle manufacturer, repairs ranged from visual inspection and buckle replacement to modifying the existing buckle with new internal components.
In an unusual move, NHTSA continued to investigate Honda and supplier Takata after the recall announcements and found that the companies should have notified customers and the agency of safety-related defects in their buckles. NHTSA noted that both Takata and Honda were liable for civil penalties. Both companies agreed to pay fines to settle the matter, meanwhile denying they had in fact hidden the defect from the government and public.
In addition to the low number of vehicles repaired under the recall campaigns, another concern affecting the TK52 buckle has surfaced. Some TK52 buckles appear to have been manufactured outside of the necessary tolerances resulting in instances of false latching. False latching occurs when an occupant attempts to buckle the seat belt and the latchplate is held by the buckle; however, it is not fully latched in place and can release due to occupant movement or forces in a collision. Problems with component tolerances causing false latching was the subject of a 1996 recall affecting a small number of Isuzu models. Although the recall was limited, investigations by plaintiffs who claim that the seat belt was in use prior to a collision are yielding evidence that models outside of the recall may suffer from the same defect.
Inertial Unlatching May Be the Cause of "Unbelted" Occupants
Despite vigorous debate that seat belt buckles do not inertially unlatch in real-world collisions, evidence that manufacturers have been aware of and adopted design alternatives to prevent this hazard continue to mount. Seat belt buckle inertial unlatching refers to the inertial forces acting the on back-side of the seat belt buckle particularly in side-impact and rollover crashes that can cause the buckle to release the latchplate. Buckles using a side release button, which were used in millions of Ford, GM, Chrysler, and some imports beginning in the 1960s, are most susceptible to inertial unlatching.
Identification of the inertial unlatching problem was first noted in early seat belt patents dating back to the 1950s and 1960s. A number of patents described the potential for inertial unlatching and describe buckle designs that are resistant to the problem. These buckles are found in production vehicles beginning in the 1970s. In fact, many manufacturers who used the potentially problematic buckles were also using designs to prevent unlatching in other models. Additional evidence that inertial unlatching can occur in real-world collisions is also found in manufacturers' recalls and testing.
Lap-Only Seat Belts: Dangerous Designs Are Still Significant Safety Problem
Despite the well-known hazards of lap-only seat belts, which have been associated with the increased risk of abdominal and lumbar spine injuries for more than 30 years, these belts continue to be used in motor vehicles. Automakers installed lap-only belts in the rear outboard seats of U.S. market vehicles until 1989 and continue to use these hazardous designs in the center front and rear seating positions. Most of the victims of lap-only belt injuries are children.
Lap-only seat belts cause injuries when an occupant's torso flexes over the belt, which provides pelvic restraint only, or when the belt rides over the bony structure of the pelvis transferring loads to the abdomen. The most frequent injuries are to the lumbar spine causing paraplegia as well as abdominal injuries such as avulsions, hemorrhage, and rupture of the internal organs including the intestines, liver, pancreas, and spleen. Head injuries are also common when occupants flex over the belt and strike interior components.
Rear seat outboard position lap/shoulder belts, which offer significantly more protection than lap-only belts, were not required in the U.S. until 1989. However, similar model vehicles with these rear seat lap/shoulder belts have been sold overseas since the 1970s--and in many cases in countries that did not require them.
The National Highway Traffic Safety Administration (NHTSA), the agency under the U.S. DOT charged with mandating motor vehicle safety requirements, delayed rulemaking to require rear seat shoulder belts well beyond the time was known that they caused injury and provided far less protection to occupants in crash.
The turning point in this long saga came after the publication of the National Transportation Safety Board's 1986 study of lap belts. The NTSB, an independent federal agency charged with investigating transportation safety, but with no rulemaking power, noted that lap belts were causing serious injuries in real-world collisions and recommended that lap/shoulder belts be required and available for retrofit into older vehicle models. Congress roundly criticized NHTSA for delaying a requirement for rear seat lap/shoulder belts. Ultimately it took an act of Congress in 1987 to force NHTSA to issue new rules for safer lap/shoulder belts.
The NHTSA requirements for lap/shoulder belts in rear seat outboard seating positions left two significant unresolved problems: Pre-1989 vehicles were not required to have retrofitted lap/shoulder belts, and the center middle seating positions were excluded from the rule.
Based on NTSB's recommendations, manufacturers developed various retrofit programs; however, these programs were poorly advertised, lap/shoulder retrofits were not available for all models, consumers were forced to bear the cost, and dealers were not made aware of or did not stock the necessary parts. As a result, most consumers were unaware of lap/shoulder belt availability or their significant safety advantages. Those who did know of the problem were often thwarted by the dealer or the cost of the retrofits. At the manufacturers' request, NHTSA's rule also exempted outboard seating positions adjacent to a walkway in minivans, leaving another occupant vulnerable to lap belt hazards.
The front and rear center positions in many vehicles, including many popular sedans and pickup trucks, still use hazardous lap belt designs. While there is no requirement, some manufacturers have used center-position lap/shoulder belts since 1987, and there are clearly no technological obstacles to adding a safer seat belt design. Since 1987, manufacturers have begun to add rear middle position lap/shoulder belts even in low-price compact cars, clearly debunking arguments that these designs are too costly.
If you have questions or comments, please feel free to contact us.
©2009 Newsome Law Firm