An in-depth review of previous reported research results concerning lap belt restraint dynamics, biomechanics, and field data effectiveness was performed in this study and the summarized results were analyzed using basic kinematic and dynamic principles in an attempt to place in perspective the continuing controversy concerning the effectiveness of lap belt only restraints in automobiles. The results of this study show that the currently reported lap belt effectiveness of 15% to 20% overall and - 10% to +10% in frontal impacts fits a pattern that has been reported for many years. That is, lap belts are partial restraint systems only and their limitations show up most markedly in the most frequent type of accident, the frontal impact.