Progress toward a more efficient U.S. automobile fleet with reduced average vehicle size and mass has precipitated studies of injury risk to small car occupants and projections of future traffic fatalities. Unfortunately, the importance of vehicle size and mass is often left either obscure or over emphasized relative to other factors influencing highway safety. This review indicates the influence of reduced vehicle size and mass is small relative to potential effects of increased vehicle miles traveled or restraint usage. For increased risk conditions of high vehicle miles traveled and low restraint usage, traffic fatalties in the year 1995 could number around 70,000. For reduced risk conditions of low vehicle miles traveled and a theoretical upper bound on restraint usage, traffic fatalities in 1995 could number around 35,000. In either case, reduced vehicle size has a relatively small and relatively predictable influence on this wide range of future highway safety estimates. Restraint system usage, while unpredictable, has a much higher potential to affect future traffic fatalities.