2007 National Roadside Survey of Alcohol and Drug Use by Drivers

2007 National Roadside Survey of Alcohol and Drug Use by Drivers: Drug ResultsResultsSince two different biological matrices (oral fluid and blood) were gathered to be analyzed forthe presence of drugs, we present prevalence estimates in three different ways in this report.1) We present both daytime and nighttime drug prevalence estimates based on theanalyses of the oral fluid samples alone, and then in combination with alcohol using breathalcohol test results. Tables reporting self-report drug use, observed safety measures, and reportswith contact with the criminal justice system and the health care system follow these results.2) We next present nighttime drug prevalence estimates based on analyses of blood, 14and then in combination with alcohol using breath alcohol test results.3) The third section presents nighttime prevalence results based on the combination ofthe results of the oral fluid / blood analyses, and subsequently in combination with alcohol usingbreath alcohol test results. We conclude this section by presenting prevalence estimates forspecific drugs from oral fluid and/or blood combined. In each of the sections, the results arepresented first in terms of drivers who were positive for any drug, then by class, followed bycategory as described in Tables 17 and 18.Throughout this report, we do not combine results for daytime and nighttime survey respondents,but display the two groups separately because the sampling frame is different for the two groups.The daytime drivers were sampled during a single Friday two-hour period in each PSU, while thenighttime drivers were sampled during four two-hour periods (two on Friday night and two onSaturday night in each PSU). Thus, combining the daytime and nighttime samples would notresult in a meaningful representation of driver drug use overall.Each of the various sampling stages (or frames) required a separate calculation of probability,which then became a component of the final probability computation, reflecting all levels orframes. The total weighted number of the sample was identical to the total number of eligibledrivers entering the survey bays, including refusers, but was adjusted to reflect the estimateddistribution of those drivers in the 48 contiguous States. Error terms for the analyses werecomputed by STATA (Stat Corp., 2006) to account for the differential weights, and the amountof variance attributable to the various sampling frames. Further information on the weighting ofthe data can be found in the Methodology Report (Lacey et al., 2009a).Oral Fluid Results (Daytime and Nighttime Samples)Driver Drug Use Prevalence Based on Oral Fluid ResultsThis section of the report presents the overall results of oral fluid analyses for all of the drugsindicated in the introductory section. Drivers who tested positive for one or more of the drugs wetested in oral fluid are categorized as drug-positive. It should be emphasized that this set of tablesaggregates over-the-counter, prescription, and illegal drugs and metabolites of drugs in eachcategory, indicating only that those who tested positive have recently consumed at least one ofthe tested drugs and not that they were necessarily impaired by the substance.14 Daytime data collection did not include requests for blood samples.37