According to the 1980 law, a person is presumed guilty of driving while intoxicated if the alcohol weight in the blood is at or above .10 percent. If found guilty, the DWI offender is sentenced to 1 day in jail, plus fines, and is required to attend alcohol information school. This study obtained data from 41 cities and 15 counties for the period January 1977 to December 1979 and January 1980 to December 1982. Dramatic increases in arrests, convictions, and incarcerations demonstrate the efficient implementation of the 1980 law by law enforcement organizations, prosecutors, courts, and jails. Alcohol-related accidents continued to climb in the 1977-81 period, but in 1982 showed a significant decrease. Specifically, there has been a 20-percent decrease in the number of alcohol-related accidents per month for the 41 cities and a 28-percent decrease per month for the 15 counties. The 1-year lag in realized effects may be attributed to the time it has taken for DWI offenders to understand the full impact of the tougher laws and start to change their behavior. Other research indicates that increasing the severity of punishment without ensuring the certainty of apprehension is futile. Tables, graphs, and eight references are included. The appendixes contain Washington State traffic statistics, a chronology of the process of changing Washington's DWI legislation, a discussion of the time series pattern description method, and a list of the sample sites.