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9 DRUG AND ALCOHOL INFLUENCES However, some other "legal drugs," which also are con- IN CRASH STATISTICS trolled substances and must be obtained by medical prescrip- tion, are known to have adverse effects on actual or simulated The third issue concerns assessing whether drug-involved driving as well. Some of these include the hypnotics such automobile and truck and bus crash statistics can determine as diazepam, flurazepam, and loprazolam, or various anti- whether drugs or alcohol actually were factors in causing the depressants and antihistamines. Many drugs, especially some crashes, or whether drugs merely were concomitantly just prescribed medications, can influence vision, vigilance, and present at the time of the crashes. Numerous studies, reviews, even impulsiveness. Problems such as driver fatigue, lack and statistical treatises of highway accident reports document of attention, vigilance deficits, and suicidal and aggressive the large numbers of drivers, injured or dead in crashes, tendencies (singularly or in combination) can contribute to who had evidence of drugs or alcohol in their bodies. These causing crashes. OTC medications available without prescrip- determinations are often made through the analysis of blood tions, but which are also known to be psychoactive, include or tissue samples taken soon after the crashes (e.g., NTSB drugs such as the antihistamines containing diphenhydramine 1990, 1995; DeGier 2005; TRB Committee on Alcohol and (e.g., Benadryl). Most likely because they are usually pre- Other Drugs 2005). DeGier (2005), while focusing on medi- scribed by a medical practitioner, not subject to high abuse cinal drugs, cited numerous studies reporting traffic and drug potential, and not commonly used for "recreational purposes," statistics for 13 European countries, and indicated that the tests for these drugs, and many others, are rarely performed on quest for knowledge on the prevalence of drugs other than impaired ground vehicle drivers (whether commercial drivers alcohol in road traffic is hampered by methodological problems or not). If two or more drugs are found in a vehicle driver, encountered with epidemiological studies of drugs and driving, it is essential that the combined effect on performance be including problems with sample collection and data collection considered and evaluated (McBay 1997). procedures. DeGier estimated the presence of illicit drug use in the general driver population, at least in Europe, to be in In civil and commercial aviation transportation, procedures the range of 1% to 5%, whereas the prevalence of medicinal have been put in place by the NTSB and the FAA's Civil drugs affecting driving performance is higher (5% to 10%). Aeromedical Institute (CAMI) to do toxicological analyses In an overview of studies on drug-impaired driving in the of postmortem samples from pilot fatalities in aviation crashes United States, Jones et al. (2003) reported that benzodiazepines to determine whether performance impairment from a medical were found to be present in 4% of noncrash-involved drivers. condition(s) and/or drug and ethanol use was a contributing In a FMCSA research and analysis brief, Gruberg (2007) esti- factor in a particular crash (Chaturvedi et al. 2005; Canfield mated that in 2005 1.7% of drivers with commercial driver's et al. 2006; Botch and Johnson 2008). However, in both trans- licenses (CDLs) used controlled substances, and 0.2% used portation communities (aviation and ground motor vehicle alcohol [>0.04 BAC (breath alcohol concentrations)] while crash investigations) it is usually by inference that drug-crash performing their duties. causal conclusions are drawn and there is some uncertainty about the veracity of those conclusions. In 1994, the U.S.DOT first issued regulations requiring testing of safety-sensitive employees in transportation indus- The problem is exemplified by McBay (1997), who tries "for use, in violation of law or Federal Regulation, of addressed issues of whether enough is known about the alcohol and drugs listed in the Controlled Substances Act" effects of drugs on driving performance to permit expert (Federal Register 1994). The DOT stated that drivers shall witnesses to testify in court cases about the likely impairment not use controlled substances, except when the use is pursuant effects of drugs on a driver. Although McBay reported that to the instructions of a "physician who is familiar with the adequate methods are available for the identification and driver's medical history and assigned duties, and has advised determination of the amount of drugs through examination of the driver that the prescribed substance or drug will not blood, urine, hair, sweat, saliva, and other specimens taken adversely affect a driver's ability to safely operate a commer- from drivers shortly after crashes, the major problem is in cial motor vehicle" [391.41 (b)(12)]. The stated intent of the relating the drug concentrations in the specimens to actual federal workplace drug testing program is/was to identify driving impairment. Specimens other than blood may be useful individuals who use "illegal substances" (Federal Register in determining drug use, but none is helpful in determining 1994; see also Section 503, Public Law 100-71). For safety- whether there was an active drug in the body that was affecting sensitive employees, including commercial drivers, random driving performance at the time of a crash. Interpretation drug screening tests collect urine specimens that are tested for of the effects produced at various concentrations of drugs phencyclidine and cocaine (illegal drugs), and amphetamines, in blood specimens depends on many factors not generally marijuana and opiates, which may be prescribed by a medical available to an expert witness for use as a basis for formulating practitioner or taken without a prescription (Gruberg 2007). acceptable scientific opinions. Some of the factors are: the Regardless of jurisdiction, use of "medical marijuana" is pro- impossibility of reliably back-calculating a concentration(s) hibited by drivers of CMVs (FMCSA Frequently Asked Ques- to a prior time, individual differences in metabolism, single tions for Drug and Alcohol Compliance, FAQ: www.fmcsa. or chronic dosing, tolerance, withdrawal, inter- and intra- dot.gov/rules-regulations/topics/medical/faq.aspx.) laboratory methods and variances, multiple drug use, method