Since MADD started being more interested in being neo-prohibitionists than in actually reducing the number of traffic accidents and fatalities caused by alcohol. They broaden their definitions of "intoxicated" and "alcohol-related" so as to increase the number of "intoxicated" motorists and "alcohol-related" crashes, and then point to such increases as a basis for imposing even broader definitions of "intoxication".
IMHO if the amount of alcohol someone has consumed affects their driving ability they should be arrested. If drugs, prescribed, over the counter or illegal hamper someones driving ability, they should be arrested. On any given weekend night 1 out of 10 cars has a drunk driver behind the wheel. Impaired drivers need to be stopped. No one has the right to endanger other people because they can't control their own behavior.