You know, if we would just do roadside tests for impairment, period, then it really wouldnt matter what the person was impaired by. If you're impaired, you're impaired. It really is simple. Come up with a more cohesive coordination type of test, that can test for impairment from anything, be it alcohol, pot, LSD, pills, or hell, just plain tiredness. If you fail the impairment test, you are taken off the road, period. If you fail the impairment test, and then later test for "x-amount" of level of alcohol or drugs, you get charged with DUI. If you were just tired, you get a warning, and then a fine. But if you do not fail the impairment test at all, then you should be free to go. It really is that simple. There are plenty of folks out there who can drive with a certain level of intoxicants, and plenty of people who can't. Impairment levels are different for everyone, for all substances, not just psycho-actives.