Abstract
The influence of the Fairfax County alcohol safety action project on the B.A.C.'s of drivers at night is discussed. Data were taken before and 9 months after the start of the project. Significantly higher percentages of drinking drivers were found in the after survey, with a slight reduction in B.A.C. above 0.10%. An index of accident probability that revealed dramatic reductions in accident probability for late night hours on weekends was calculated.