Throughout the motorized world seat belts are now accepted and worn by the majority of front seat occupants and by an increasing proportion of rear seat passengers, and data is presented to illustrate current rates. Current seat belts and airbags have fixed characteristics, usually optimized around the 30 mph flat barrier test for airbags with an otherwise unrestrained 50th percentile male dummy, and in the case of the restrained dummy the restraints are optimized to the 35 mph NCAP crash test. Some real world population characteristics are described, particularly the ranges in sitting positions, weights, sitting heights and biomechanical tolerance variation. Some of the population characteristics of frontal crash severities are also summarized. The desirable parameters of future restraint systems which would have variable characteristics are outlined in an effort to address these population issues.