Automatic Shoulder Belt Manual Lap Belt Restraint Systems: Human Factors Analyses of Case Studies Data

Abstract

Automatic shoulder belts combined with manual lap belts satisfy federal requirements for passive vehicle restraint systems. Previous studies show that usage rates of the lap belts in these systems is considerably lower that usage rates for manual three-point belts. Recent years have witnessed a substantial amount of litigation involving the automatic shoulder belt manual lap belt systems. Forty-one legal cases have been reviewed in which an occupant was injured or killed in an accident while wearing the shoulder belt but not the lap belt. Particular attention was given to issues of risk perception and warnings. Analyses of these cases indicate reasons for not wearing the lap belt include: (1) feeling belted or secure when the shoulder belt was in place; (2) forgetting to fasten the belt; and (3) not familiar with the type of seat belt system. The vehicle warning systems designed to encourage lap belt use generally fail to communicate the hazards and consequences of not wearing the lap belt.