USAGE AND EFFECTIVENESS OF REAR-SEAT BELT RESTRAINTS IN SEVERE FRONTAL CRASHES

Current estimates of effectiveness for lap belts and for lap-shoulder belts are based on studies of FARS (Fatal Accident Reporting System) data for years ending in 1985 or 1986, wherein usage of belts in the rear seat positions was almost non-existent. This paper reviews the fatal injury rates of front and rear outboard occupants in severe frontal crashes from all 21 years of FARS data currently available [FARS, 1995]. Belt usage by FARS frontal-crash occupants does not comport with the NHTSA nationwide usage estimates, which today range around 68 percent. Front-seat FARS usage has grown steadily to about 55 percent, rear-seat usage to about 34 percent by 1995, the latest year for which compiled FARS data are available. The 21 years of FARS data suggest that the frontal fatality-reduction effectiveness of lap-shoulder belts for drivers and right-front occupants is about 45 percent, which is consistent with earlier estimates by NHTSA (National Highway Traffic Safety Administration). FARS data on rear-seat belt use and fatal injury rates, for both lap-only and lap-shoulder belts, are analyzed. The data demonstrate that rear-occupant fatal injury rates are similar for lap-only and lap-shoulder belts. Indeed, lap-only belts post a better reported injury rate than do lap-shoulder belts for the protection of rear-seat occupants in frontal crashes within the totality of FARS data. While surprising in comparison with accepted early effectiveness estimates (which were based on very sparse national field data, mostly from front seats), this result is seen to be in accord with predictions from still earlier state field studies. It is concluded that in severe frontal crashes in the rear seat environment, the protection offered by lap belts is at least as good as that offered by lap-shoulder belts. For the covering abstract see ITRD E116488.