ing procedures, Evans (1990) estimated that eliminating alcohol would reduce overall traffic fatalities by about 47 percent. Yet these estimates do not reflect the enormous human and economic costs that result from the nonfatal traffic injuries in which alcohol figures prominently (Stoduto et al. 1991; Vingilis et al. 1988). Alcohol and Motor Vehicle Crashes Perrine (1990) noted that society's perception of drunken drivers has changed over the past 50 years. For example, the BAC legal threshold for impairment has decreased as research data, field experience, and social and political pressure have increased. Several States have reduced their BAC limits from .10 percent to .08 percent, and an increasing number of States are considering similar legislation. Emphasis has shifted from drivers who are drunk to drivers who are intoxicated to drivers who are impaired. Researchers therefore have shifted from the dichotomy of intoxicated/not intoxicated to the concept of impairment, which can be measured as diminished performance or reductions in other behavioral activities that result from specified amounts of alcohol consumption (Perrine 1990). In 1989, 22,413 people were killed in alcoholrelated motor vehicle crashes, representing approximately 49 percent of all traffic fatalities (figure 5). Fatalities are defined as alcohol related when one or more drivers or nonoccupants (pedestrians, cyclists) have a BAC of .01 percent or higher. Approximately 39 percent of all traffic fatalities (17,849) resulted from crashes in which at least one driver or nonoccupant had a BAC of .10 percent or higher. Although the number of people killed and injured in alcohol-related traffic crashes continues to be high (NHTSA 1991), study estimates suggest that some progress has been made in this area during the past decade. Between 1982 and 1989, the percentage of traffic fatalities involving at least one intoxicated (BAC .10 percent or higher) driver or nonoccupant declined from 46.3 percent to 39.2 percent (figure 6).1 A similar pattern can be discerned with alcohol involvement for all drivers involved in fatal crashes (figure 6). 1 Although 1990 data on alcohol-related fatal crashes are now available, an analysis of the data had not been performed when this chapter was written. For drivers in all age categories, there has been a slight downward trend in fatal crashes involving high BACS (.10 percent or higher) (NHTSA 1991). But the rate of decline has not been constant across age categories. Drivers under 18 experienced the sharpest declines. For these drivers, the percentage of traffic fatalities involving at least one intoxicated driver or nonoccupant decreased from 19 percent to 10 percent between 1982 and 1989, a 47-percent reduction. For drivers aged 18 to 20 and those 65 or older, the decline was approximately 33 percent. Declining rates of alcohol involvement among younger drivers may be partially attributed to changes in minimum-drinking-age laws (NHTSA 1991) (see Chapter 12, Prevention of Alcohol-Related Problems). The smallest rate of decline (about 9 percent) was among drivers aged 25 to 34. Comparatively small reductions in the proportion of high-BAC fatal traffic crashes were also observed for drivers aged 35 to 54 and those between 21 and 24. Alcohol and Increasing Risk of Injury Epidemiological research on non-motor vehicle traumatic injury safety offers important baseline information on rates of alcohol involvement and strongly suggests that alcohol increases the risk of injury. Although it is commonly believed that alcohol may protect against injury once an accident occurs, research findings provide evidence to the contrary. Controlled animal studies indicate that alcohol exacerbates the injurious effects of trauma. Moreover, an analysis of data from more than 1 million drivers involved in motor vehicle crashes indicated that when such effects of injury-related variables as safety belt use, vehicle deformation, vehicle speed, driver age, and vehicle weight were accounted for, drinking drivers were more likely than nondrinking drivers to suffer serious injury or death (Waller et al. 1986). As Perrine et al. (1989) pointed out, the fact that nearly 50 percent of all motor vehicle fatalities are alcohol related does not necessarily prove that alcohol contributed to the crash because it is not known how many crashes would have occurred in the absence of alcohol. Estimating increased relative crash risk requires knowledge of BACS among comparable drivers who are not involved in motor vehicle crashes. Case-control studies (Borkenstein et al. 1964; McCarroll and Haddon 1962; Perrine et al. 1971) can serve as a powerful tool for estimating the increased risk of traumatic injury. For purposes of comparison, these studies randomly select and test drivers who pass crash sites at times that are comparable to the time an accident occurred. This procedure enables researchers to estimate the distribution of BACS for comparable drivers who were not involved in fatal crashes. Reviews of such studies (Hurst 1973; NHTSA 1985; Perrine et al. 1989) indicate that the risk of a fatal crash increases exponentially with increasing BAC. According to Perrine et al. (1989), all studies show increased risk by .08 percent BAC and dramatically increased risk at BACS of .10 percent and higher. These investigators assert that case-control studies underestimate the increased risk of fatal motor vehicle injuries, especially at low BACS. Zador (1991) used data from the second national roadside breath testing survey (Lund and Wolfe 1991) and the NHTSA Fatal Accident Reporting System (FARS) to estimate the relative fatal crash risk for drivers at different BACs. Compared with the risk for nondrinking drivers, the relative fatality risk for drivers in single-vehicle crashes was slightly elevated for drivers with BACS between .02 percent and .04 percent (figure 7). Risk increased sharply at higher BACs. Compared with the risk for nondrinking drivers, the risk of fatal injury was an estimated 11.1 times greater for drivers with BACS between .05 percent and .09 percent, 48 times greater for drivers with BACS between .10 percent and .15 percent, and 385 times greater for drivers with BACS higher than .15 percent (Zador 1991). Zador (1991) noted that nearly 40 percent of drivers aged 16 to 19 who were involved in alcohol-related fatal traffic crashes had BACs under .10 percent. Alcohol may pose an especially serious risk for younger drivers because they have comparatively little experience with alcohol or driving. In addition, the effect of increasing BAC on relative fatality risk may vary by gender. Borkenstein et al. (1964) found that at BACS higher than .04 percent, the risk of fatal injury increased faster for females than for males. Zador (1991) used log-linear models to estimate the extent to which different BACS increased the relative risk of fatal crash by age and sex (table 1).2 Male drivers aged 25 years or older, with BACS equal to the criterion group, were arbitrarily used as the reference category for calculating increased relative risk. Regardless of gender, alcohol increased relative crash risk most substantially among drivers aged 16 through 20 years. This effect is most apparent at moderate BACS (e.g., .05 percent to .09 percent). Alcohol also appears to increase crash risk more for females than for males. Indeed, the sharpest increase was for young females aged 16 through 20 years who had moderate BACS; their increased risk of fatal crash was 21.3 times higher than that for males aged 25 years or older with comparable BACS. Zador's (1991) analysis suggests that (1) alcohol increases fatal crash risk more for females than for males, (2) alcohol increases fatal crash risk more for younger drivers than for older ones, and (3) moderate BACS profoundly enhance crash risk among drivers aged 16 years through 20 years, and especially among females of the age group. This analysis also suggests that more attention should be given to the effects of low and moderate BACS and to gender and age differences when considering the effects of alcohol on behavior and safety. Young Females: At Increasing Risk? Female drivers are less likely to be involved in alcohol-related motor vehicle crashes than males. In 1989, about 27 percent of male drivers involved in fatal crashes had BACS of .10 percent or higher. The comparable rate for women was 14.4 percent (NHTSA 1991). But the proportion Table 1. Estimated increased relative fatal injury risk by sex, age, and blood alcohol concentration (BAC) in single-vehicle crashes. 2 To calculate increased relative risk, one must specify an appropriate reference category for purposes of comparison. Zador of fatally injured female drivers increased 37 percent between 1982 and 1989 (NHTSA 1991). According to the Nationwide Personal Transportation Study, the average number of miles driven by women aged 16 to 19 increased 21 percent between 1969 and 1983 (Federal Highway Administration 1985). The same study indicated that the proportion of young women who drove also increased during that period. Other studies report increased heavy drinking among younger women (Fillmore 1984; Wilsnack and Beckman 1984). These combined changes in the drinking and driving behavior of young females point to a population potentially at increasing risk of involvement in alcohol-related motor vehicle crashes (Fell 1987; Popkin 1991; Popkin et al. 1988). Using FARS data, Fell (1987) noted that for females aged 21 to 24, rates of alcohol involvement in fatal crashes did not decrease between 1982 and 1985. This finding contrasted with the decreasing rates of alcohol involvement for males in all age categories and for females in general. Popkin (1991) analyzed changes in arrest rates, alcohol-related crashes, and single-vehicle nighttime crash rates by age and sex in North Carolina (table 2). For most subgroups, drivingwhile-intoxicated (DWI) arrest rates decreased between 1976 and 1985. DWI arrest rates decreased sharply for males in the age categories investigated. However, decreases in DWI rates were less significant for females than for males. In fact, females aged 21 through 24 years were the only group to experience an increased DWI arrest rate (26 percent) during the study. Striking gender differences were reported in the changing rate of alcohol-related crashes. Regardless of age, the rate of alcohol-related crashes among males declined between 1976 and 1985 (Popkin 1991). Among females, the crash rate increased 74 percent for those aged 18 through 20 years, 93 percent for those 21 through 24 years, and 45 percent for those 25 through 34 years. For females under age 18, the rate of alcohol-related crashes decreased. Popkin (1991) found significant gender differences in single-vehicle nighttime crash rates, a variable that often is used as a surrogate indicator of alcohol involvement. For male drivers under 18, the single-vehicle nighttime crash rate decreased by 20 percent between 1976 and 1985; in comparison, there was a 29-percent increase for females in the same age category during this period. Females in other age categories also exhibited increased involvement in singlevehicle night time crashes (table 2). Alcohol and Traffic Safety: It is clear that alcohol consumption impairs many perceptual, cognitive, and motor skills needed to safely operate motor vehicles (Hindmarch et al. 1991; Moskowitz and Burns 1990; Moskowitz and Robinson 1988). Nevertheless, the relationship between alcohol consumption and motor vehicle safety is confounded by a myriad of poorly understood factors. Previously cited literature demonstrates that the effects of alcohol on traffic safety vary by age and gender. combined changes in the drinking and driving behavior of young females point to a population potentially at increasing risk of involvement in alcohol-related motor vehicle crashes. A growing body of literature (Argeriou et al. 1985; Arstein-Kerslake and Peck 1985; Donovan and Marlatt 1982; Donovan et al. 1986; McMillen et al. 1989; Perrine 1990; Wells-Parker et al. in press; Wieczorek and Miller in press; Wilson 1991) indicates that the impaired-driving population varies in terms of the following: ♦ Severity of alcohol problem • Demographic characteristics ♦ Involvement in deviant and criminal behavior • Expectations about the effects of alcohol Personality characteristics. The literature suggests that these factors may mediate the relationship between alcohol and traffic safety. For example, in an experimental study using a balanced-placebo design, drivers who initially scored high on measures of sensation-seeking, hostility, aggressiveness, and psychopathic deviance and who believed that they had consumed alcohol subsequently displayed increased high-risk driving behaviors (McMillen et al. 1989). Drivers who initially scored low on these characteristics and believed that they had consumed alcohol subsequently displayed fewer high-risk driving behaviors. Table 2. Percent change in North Carolina driving-while-intoxicated (DWI) arrest rates, alcohol-related (A-R) crash rates, and single-vehicle nighttime (S-V-N) crash rates, by age and sex, 1979 to 1984. SOURCE: Reprinted with permission from Accident Analysis and Prevention, volume 23, Popkin, Drinking and driving by young females, copyright 1991, Pergamon Press Ltd. McMillen et al. (1991) compared eight driver groups on personality measures (e.g., hostility, sensation-seeking, psychopathic deviance, and mania) and behavior measures (e.g., number of drinks consumed per week, number of times per month of driving impaired, number of nontraffic arrests, number of crashes, and number of crashes after drinking). The researchers found that impaired drivers arrested after an accident or moving violation were significantly higher in hostility, psychopathic deviance, nontraffic arrests, frequency of impaired driving, crashes after drinking, and drinks consumed per week than impaired drivers caught in roadblocks. Neither impaired drivers stopped in roadblocks nor impaired drivers never arrested differed from nonimpaired drinking drivers or nondrinking drivers on most measures examined. The findings of this study suggest that impaired driving is part of a larger pattern of problematic characteristics and behaviors for some individuals. Compared with men in the general driving population, male offenders convicted of driving under the influence of alcohol (DUI) are heavy drinkers. According to Perrine (in press), about 10 percent of males in the general driving population, 40 percent of first-time DUI offenders, and 60 percent of multiple DUI offenders reported consuming five or more drinks as their usual amount. Fifty percent of the general driving population, 92 percent of first-time DUI offenders, and 93 percent of multiple DUI offenders reported having five or more drinks when they consume more than their usual amount. In a study examining the extent and nature of criminal behavior among DUI offenders, Argeriou et al. (1985) reviewed the criminal records of 1,406 randomly selected DUI offenders in Massachusetts. The records revealed a history of prior court arraignments in 76.5 percent of cases. Half of the individuals had been arraigned for criminal offenses other than or in addition to traffic and DUI offenses, and one-fourth had been arraigned previously for DUI. Among those with prior DUI arrests, 68 percent also had criminal arrests. A 3-year followup indicated that 63 percent of those rearrested for DUI had prior criminal arrests. These findings indicate that DUI offenders are a heterogeneous group; rehabilitation programs should be responsive to the differences in this population. Alcohol and Air Traffic The recent conviction of two commercial airline Compared with motor vehicle crashes, aviation crashes are quite rare and relatively little research has been conducted to estimate the extent of alcohol involvement. Copeland (1986) analyzed the medical examiner's files for noncommercial aircraft fatalities in Dade County, Florida, between 1977 and 1983. BACS were |