There are an undetermined but significant number of people driving while under the influence of prescription or over the counter drugs; there are also an undetermined but significant number of people now driving under the influence of marijuana, even though it is illegal. Despite this, the major danger signals for drivers continue to be alcohol in the bloodstream, a cell phone in the hand, and lead in the foot; a drunk trying to send a text message while driving at high speed is an accident that won't wait long to happen. Impairment by drugs simply does not register as a significant cause of traffic accidents. I wonder why?