After almost a decade of use of three-anchor point safety-belts, further improvements in the systems can only be achieved in small steps. The paper investigates the effect of safety-belt-, vehicle- and passenger-parameters on the effectiveness of the belt system. Individual topics include passenger position, tenseness of belts, effect of other passengers, location of belt anchors, and collision processes. Safety evaluation criteria are also discussed.The discussions indicate areas of improvement for current passenger-restraint systems and related vehicle components. Moreover, the beneficial aspects of greater use of seat-belts are undisputed; before other, more costly passenger-safety measures (e.g., speed limitation devices) are implemented, their effectiveness should be investigated and compared with the potential of greater belt use. Alternative belt systems, such as passive safety-belts, offer hope for more universal use.