Seat belts play a central role in protecting motor vehicle occupants during accidents. And mandatory seat belt usage laws have fortunately greatly increased the number of Americans currently wearing seatbelts. Yet for every five people killed in motor vehicle accidents in the U.S., three would have survived had they been wearing their seat belts.
During an accident, seat belts restrain the occupants and prevent them from being ejected from the vehicle. They also provide a controlled “ride down” of the violent forces acting on a motor vehicle's occupants during a collision.
But if a seatbelt is not properly worn, or if it, or any of its components fail during an accident, serious injuries and death are likelier to result. And while seat belts should always be worn in a motor vehicle, in rare cases a defective seat belt can exacerbate or even be the cause of injuries during an accident.
In any event, we count on seatbelts to provide us with a certain measure of protection during an auto accident. A seat belt that fails to do so because of a design or manufacturing defect makes the resulting injuries or fatalities all the more tragic. The more common seatbelt defects and seatbelt-related causes that have led or contributed to motor vehicle accident injuries and fatalities include:
* Faulty tension relieving device and excessive belt slack—seatbelt systems that include a device allowing for slack on the shoulder belt can sometimes fail to retract the belt after the occupant has moved forward, resulting in permanent slack. Many of these devices retract the belt after the occupant tugs on the belt after having moved forward. But an accident can take place while the belt is in the temporarily slacked state. The resulting slack, whether temporary or permanent, can result in head, facial or abdominal injuries and spine fractures during an accident.
* Shoulder belt spool out—a incident also known as “skip lock” occurs when a belt fails to lock or locks up late in the accident sequence. When seatbelt systems in which the seatbelt is designed to lock when the vehicle exceeds a specified level of deceleration experience skip lock, unnecessary head and spinal injuries may result.
* Defective buckle and inertial unlatching—many types of seat belt buckles can release during impact and open. The inertial force of the forward movement of the occupant is transferred to the spring of the buckle, which releases the tension on the latch plate. This can happen even during relatively weak impacts, and when the buckle releases, the occupant is subjected to the same dangers as he or she would of had the seatbelt not been worn at all.
* Defective buckle and unintentional or inadvertent unlatching—some seatbelt buckles have been shown to false latch, partially unlatch, inadvertently unlatch, fail under a load, become inoperative, or not latch at all. One example includes the GEN 3 buckles that are contained in 1993-2002 Chryslers. The release buttons are raised above the covers, subjecting them to accidental release during a collision. Another example is that of Takata buckles, which were used in nine million cars, trucks and SUVs of various makes between 1986 and 1991. The buckles' release buttons have been known to crack or break with the application of relatively weak impacts or forces.
* Lap belt only seatbelt—many rear seats, center seats and even front seats in older vehicles are equipped with lap-only seatbelts. By failing to restrain the upper torso such as with three-point diagonal shoulder belt system, lap-only seat belts can result in fatal internal injuries, facial fractures, spinal damage, brain damage and death when worn in an accident. The National Transportation Safety Board has concluded that lap-only belts can actually induce injury, ranging in severity from minor to deadly due to jack knifing. While the auto industry has been aware of this for decades, rear seat shoulder belts were not used until the late 1980s, so many vehicle still contain lap-only seatbelts in the rear and center seating positions.
* Improperly used passive restraint system—automatic belts were introduced in part as a less expensive way to counter proposed airbag requirements by the U.S. Department of Transportation (DOT) in the late 1960s. The first automatic seatbelts had automatic shoulder belts, but no lap belts. In frontal collisions, occupants' torsos tended to slip under the belt while their heads and necks became caught by the belt, causing broken necks, spinal cord injuries and deaths. Manual lap belts was later included, but many occupants forgot to use them or were even aware they were there.
* Door mounted automatic belts with lap belts—some manufacturers introduced belt systems in which included lap belts. The systems were mounted to the structure of the door or door frame. But the system adversely limited the geometry of the design, and if the door opened during an accident, passengers were left unrestrained and often ejected from the vehicle.
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