Driving under the influence of drugs (DUID) is a serious highway safety issue, and the number of persons who die annually in these crashes may be greatly underrepresented. Quantifying those affected by drugs—and, more specifically, by what classes of drugs—remains problematic, even in terms of crash fatalities. For instance, the ability to determine accurate on-scene blood alcohol concentrations (BACs) often trumps the delayed receipt of drug results collected by far more cumbersome, time-consuming, and expensive means.

According to the National Highway Traffic Safety Administration (NHTSA), only 63 percent (13,801) of the 21,798 drivers killed in U.S. traffic crashes in 2009 were tested for “drug involvement,” which neither implies impairment nor indicates crash cause.The 3,952 fatally injured drivers who actually tested positive for the presence of drugs other than alcohol represented 18 percent of all of those fatalities tested in 2009 (13,801), as well as 33 percent (3,952) of those 12,055 with known drug test results. The proportion of drivers testing positive for drugs increased between 2005 and 2009.