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Rear seat occupants In frontal collisions, people wearing only lap belts have a tendency to jackknife over the lap belt. Jackknifing may result in fatal or severe abdominal injuries or spinal cord injuries, or may cause the victim's head to strike the front seat back or center console causing neurological injuries. Injuries caused by lap belts in airplane crashes have been reported since the early 1950s. Medical literature has cited injuries caused by lap belts in automobile crashes since 1956. For years, auto manufacturers have known the potential hazards of lap only belts. A Swedish safety researcher wrote in 1961, almost four decades ago, that the lap belt "does not comply with minimum performance requirements because it does not maintain the occupant in an upright position, does not protect the head and thorax, and does not hold the vital parts of the body together within the car during an accident - so it has not been considered a safety belt in Sweden." In 1967, the manager of Ford's Biomechanical Department wrote, "When properly worn, the 3-point diagonal shoulder belt has been demonstrated to offer much more greater (sic) protection to the vehicle occupant than does a single lap belt since it prevents injury from jacknifing." In fact, U.S. auto manufacturers have been putting shoulder harnesses in the rear seats of cars sold in Australia and Europe since the early 1970s.
In 1970, The National Highway Traffic Safety Administration (NHTSA) proposed rulemaking which would require full lap/shoulder belts for all seating positions. Opposition from auto manufacturers caused NHTSA to water down its original proposal, making rear seat lap/shoulder belt installation optional for auto manufacturers. (Meanwhile, as early as 1972 in Australia and in parts of Europe, Japanese, European and American automakers began installing lap-shoulder belts for rear seat occupants.)
In July 1986, the National Transportation Safety Board (NTSB) published its study, "Performance of Lap Belts in 26 Frontal Crashes," followed by law suits and national media attention, allerting the general public that rear seat lap belts present a hazard in very common crashes, especially to children. In December 1986, Congress held hearings regarding this issue, but NHTSA did not require lap/shoulder belts for all outboard seating positions until 1991.
The acute symmetrical blow of the head against the dashboard is shown with considerable hyperextension of the neck. Note the restraining action of the seat belt with the associated flexion of the lumbar spine. This type of pattern is especially true for small occupants.
The 1968 illustration above shows an occupant wearing a lap belt in the front seat hitting their head on the dashboard. A similar impact occurs in the rear seat. An occupant wearing a lap beltin the rear seat hits their head on the front seat back. In a center rear seat lap belt case, manufacturers contend that placing a shoulder harness in a hatch back vehicle is not technologically feasible. The1991 Ford Escort pictured here (below) illustrates the ease of modifying this vehicle.
The hazards of the lap only seatbelt and the clear superiority of lap/shoulder seatbelts have been known to the government and industry for decades. At a time when the government and industry seek to maximize seatbelt usage, it is irresponsible not toprovide the public with the safest available seatbelt. And at a time when our children have been relegated to the center rear seat out of a well-founded concern for their safety, it is ironic that most vehicles have an inferior lap only belt in that position. It is high time for the government and the industry to stop dragging their feet, and to start preventing needless injuries and deaths by installing lap/shoulder belts for all seating positions.
(06/30/99)
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