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Dwi prevention
Addictive Behaviors 26 (2001) 155 ± 166
DWI prevention: Profiles of drinkers who use designated drivers Barry D. Caudilla,*, Wayne M. Hardingb,c, Brent A. Moorea a
Center for Studies on Alcohol, Westat, 1650 Research Blvd., Rockville, MD 20850, USA b Social Science Research and Evaluation, Burlington, MA USA c Harvard Medical School, Cambridge, MA USA
Abstract The effectiveness of designated driver (DD) use in preventing driving while intoxicated (DWI) depends on whether drinkers at risk for DWI use DDs. Bivariate and logistic regression analyses conducted on data from 1,391 Computer-Assisted Telephone Interviews (CATIs) and from 902 barroom patron surveys showed that DD users, compared to nonusers, tended to be at-risk, heavier drinkers. For example, logistic regression using the CATI sample indicated that DD users were more likely to drink more often outside the home, to achieve higher blood alcohol concentrations (BACs) when drinking outside the home, to ride with intoxicated drivers (RID), and to be heavy drinkers on D. Cahalan et al.'s (1969) Quantity-Frequency-Variability (QFV) index. Similarly, logistic regression using the barroom sample showed that DD users tended to be heavy drinkers on the QFV index, and were more likely to drive after drinking and to ride with intoxicated drivers. Additional analyses showed that DD users also were more likely than nonusers to engage in other behavior to avoid DWI, such as drinking less, waiting to drive until the effects of alcohol diminish, walking home, and staying overnight. These results are consistent with other findings from a related study by the current authors which showed that at-risk drinkers also used free safe (taxi) rides to avoid DWI, however were still more likely to report DWI and RID behavior (B. D. Caudill, W. M. Harding, & B. Moore, in press). Consequently, DWI prevention efforts may be improved by future research aimed at learning why such at-risk drinkers sometimes take steps to avoid DWI and sometimes do not. D 2001 Elsevier Science Ltd. All rights reserved. Keywords: Designated drivers; Safe rides; Driving while intoxicated; Riding with intoxicated drivers; Barroom surveys
* Corresponding author. E-mail address: [email protected] (B.D. Caudill). 0306-4603/01/$ ± see front matter D 2001 Elsevier Science Ltd. All rights reserved. PII: S 0 3 0 6 - 4 6 0 3 ( 0 0 ) 0 0 0 9 7 - 6
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In discussing the growing popularity of designated driver programs (DDPs), and the increase in the use of designated drivers (DDs) in the U.S. over the last decade, Hedlund (1997) suggested that the term ``one for the road'' has now been replaced by a question about who will serve as the DD. In spite of the widespread promotion of DD use in various local and national publicity campaigns in the U.S., the use of DDs by many drinkers, and a high degree of public enthusiasm about the efficacy of DD use in reducing driving while intoxicated (DWI), little is known about the characteristics of DD users. A central question pertinent to the efficacy of DD use in preventing DWI is whether individuals at high risk for DWI are using DDs. If not, programs designed to promote DD use will be less effective in preventing DWI. The current study was designed to profile individuals who use DDs. The study is part of a longitudinal assessment of the impact of promoting alternative transportation measures such as DDs and ``safe rides'' (SRs; a free ride home from a nondrinking driver such as a cab company or other organization) in preventing DWI. For this study, a designated driver (DD) was defined as one person in a couple or group who does not drink any alcohol in order to drive his/her companions home safely. DDPs have become a commonly used approach for communities trying to prevent DWI. There are hundreds of local DDPs in the U.S. (Apsler, Harding, & Goldfein, 1987; DeJong & Wallack, 1992; Harding, Apsler, & Farrah, 1994). In addition, national organizations such as the Harvard Alcohol Project (Winsten, 1994), Mothers Against Drunk Driving, and the National Group Rides and Designated Drivers program promote the use of DDs. Support for alternative transportation strategies as a means of preventing DWI is extensive, with national approval ratings as high as 91% (Gallup, 1987). In addition, results from a random digit-dial telephone survey of 1,391 drinkers in two Maryland cities, as part of the current project, showed that respondents believed that DDs were very effective in reducing DWI. Their mean response was 8.3 on a scale item about DD effectiveness that ranged from 0 (not at all effective) to 10 (very effective). The concept of using a DD has become a common part of everyday language as well as a frequently used means to avoid DWI (Barr & MacKinnon, 1998; DeJong & Winsten, 1999; National Highway Traffic Safety Administration, 1999). Several recent studies have reported high levels of designated driver use. In a study of college students, Barr and MacKinnon (1998) found that 86% of respondents reported that they had used a DD at some time in their lives. DeJong and Winsten (1999) found that 37% of college students surveyed reported using a DD in the last 30 days. In the National Survey of Drinking and Driving Attitudes and Behaviors (National Highway Traffic Safety Administration, 1999), 37% of respondents reported using a DD in the last year, as did 57% of individuals 21±29 years of age. In a recent national roadside survey, 25% of drivers reported serving as a DD on that evening (Fell, Voas, & Lange, 1997). Although the concept of using DDs is popular and many drinkers report using DDs, the potential utility of DD use has also been criticized (DeJong & Wallack, 1992). A major criticism has been the belief that individuals who use DDs are most likely those with low to moderate levels of DWI risk (DeJong & Wallack, 1992; Wagenaar, 1992). Since risk of a crash increases exponentially as a function of increasing blood alcohol concentration (BAC; Zador, 1991) and the frequency with which drinkers drink to the point of intoxication, it is more important for DWI interventions to impact heavy drinkers
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and individuals who achieve higher BACs, rather than light to moderate drinkers. There is, therefore, a clear need to learn whether drinkers who are at the greatest risk for DWI use DDs to prevent DWI. Prior research on DDs and DD users has primarily focused on who serves as a DD (Knight, Glascoff, & Rikard, 1993; Martin, 1996; Schwartz & Little, 1997). Knight et al. examined the attitudes and beliefs of college student DDs using focus group interviews, while Schwartz and Little surveyed the beliefs of students who attended high school parties. Martin's study used the National Survey of Drinking and Driving Attitudes and Behavior: 1993 to examine differences between respondents who reported serving as a DD in the last year and those who did not. She reported that DDs tended to be younger, female, single, and more educated. In addition, those serving as DDs were much more likely to have used a DD in the last year. Two previous studies have profiled characteristics of DD users. DeJong and Winsten (1999) recently described characteristics of DD users from a national sample of collegestudent drinkers. Respondents who reported using a DD in the last 30 days were more likely to be older than 21, White, single, and not living with children at home. DD users were also more likely to binge drink, defined as having five or more drinks on a single occasion. In another study of college-student drinkers, Barr and MacKinnon (1998) also found that DD use was predicted by heavy drinking and by a high frequency of respondents driving to drinking destinations. The latter authors also found that women were more likely to use DDs than men. These two studies, however, were limited to samples of college students and therefore miss a large proportion of the general population, many of whom are at high risk for DWI. The current study was designed to further profile users of DDs and allows us to directly address the important question of whether drinkers at risk for DWI actually use DDs to prevent DWI. By collecting community- and barroom-level data on random samples of drinkers, the current study also benefits from examining populations of drinkers that are much more representative of drinkers in general, and drinkers at risk for DWI in particular, than samples of drinkers previously examined in other studies. Drinkers profiled here include community-level drinkers, as assessed through random digit-dialed computer-assisted telephone interviews (CATIs), and more at-risk drinkers, as assessed through the conduct of anonymous barroom surveys. 1. Method 1.1. Context of data collection Data for this paper come from 1,391 computer-assisted telephone interviews (CATIs) and 983 barroom surveys that were conducted in two Maryland communities. Data examined here were collected as part of a baseline assessment for an ongoing 5-year longitudinal study funded by the National Institute on Alcohol Abuse and Alcoholism (NIAAA) on the effects of introducing an alternative transportation program for drinkers. The program provides incentives for designated drivers in public drinking establishments and free safe
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rides home (using taxis) for drinking drivers and their passengers. The CATI sample was chosen to represent individuals in the community who drink. The barroom sample was chosen to provide a sample of drinkers at greater risk for DWI. As a result, respondents in the barroom sample tended to be younger, single, heavier drinkers, and were more likely to drink and drive. 1.2. Selecting generalizable sampling communities An important consideration for the current study was to select study site sampling communities with characteristics that would make study results generalizable to many other communities nationally. It was also important for the current alternative transportation intervention project to select experimental and control site communities that were of sufficient size (at least 50,000 citizens) to have taxi companies available to provide safe rides, that were located nearby the researchers' offices, and whose leaders were willing to host the respective study interventions. With these factors in mind, we chose the study sites of Frederick and Hagerstown, Maryland. To test the potential generalizibility of study findings to other communities nationally, we compared demographic characteristics (i.e., sex, race, marital status, educational level, income, and age) for Frederick and Hagerstown to other communities of similar size across the country using 1990 Census data. In total, there are 396 urbanized areas in the U.S. that have populations of at least 50,000 citizens, but data only exists for 290 of these communities in the 1990 Census. For our statistical comparisons of Frederick and Hagerstown with other urbanized areas, the comparison sample was limited to urbanized areas with populations of less than 150,000 (N = 171), which included the cities of Frederick (58,427) and Hagerstown (70,158). Findings showed that no variables differed between Hagerstown and other national communities examined, and only one variable was found to differ between Frederick and urbanized area averages. The median income for Frederick was significantly higher ($38,283, p < .05) than was that of the national sample ($26,804). Thus, with this minor exception for Frederick, the current study communities are clearly representative of urbanized areas nationally with populations from 50,000 to 150,000 citizens. 1.3. CATI and barroom survey measures The CATIs and the barroom surveys requested information about the following major content areas: socio-demographics; alcohol use; items used to compute respondents' usual blood alcohol concentration levels (BACs) in different contexts, such as when they drink outside the home in general, or on occasions when they use a designated driver or safe ride; items indicative of alcohol use problems; drinking and driving behavior; riding with intoxicated drivers; and behaviors other than the use of DDs or SRs used to avoid DWI and riding with intoxicated drivers. Tables 1 and 2 present all variables examined for this paper. The timeframe for DWI behaviors examined, such as the number of times the respondent drove when feeling intoxicated, was the last 12 months. A generalized form of the Quantity-Frequency-Variability Index (QFV; Cahalan, Cisin, & Crossley, 1969) was used to measure the extent of alcohol use. For this measure, respondents
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Table 1 Demographic, alcohol use, and drinking and driving characteristics of CATI respondents who did and did not use a designated driver (DD) Characteristics Demographic characteristics Gender Males Females Mean age (SD)* Current marital status** Single Married/living with partner Separated/divorced/widowed Ethnic/racial group White African American Other (Hispanic, Asian, etc.) Mean yearly incomea Alcohol use, and drinking and driving characteristics Mean times drank outside the home (SD)* Mean estimated BAC outside the home (SD)* CAGE problem drinker** QFV categories** Infrequent/light drinkers Moderate drinkers Heavy drinkers Drove after drinking any alcohol** Drove when felt intoxicated** Rode with intoxicated driver** Arrested for DWI in last year
Used a DD (33%, n = 455)
Did not use a DD (67%, n = 936)
52% 48% 35.9 (10.2)
45% 55% 45.5 (14.4)
24% 54% 22%
13% 63% 25%
93% 4% 4% $35,001 ± $45,000
92% 5% 3% $35,001 ± $45,000
35.3 (44.8) 0.05 (0.03) 12%
17.2 (37.0) 0.02 (0.05) 4%
28% 34% 37% 65% 31% 27% < 1%
62% 18% 9% 47% 11% 10% < 1%
CATI = computer-assisted telephone interviews; BAC = blood alcohol concentration; CAGE = CAGE questionnaire; QFV = Quantity-Frequency-Variability index; DWI = driving while intoxicated. a Income was a categorical variable with 10 possible response categories such as $5,001 to $15,000. * p < .05 by t-test (2-tailed). ** p < .05 by chi square.
were asked questions about their usual patterns of drinking behavior regardless of beverage type. The QFV measure places drinkers into one of the four following drinking habits categories: infrequent, light, moderate, or heavy drinkers. The CAGE questionnaire (Mayfield, McLeod, & Hall, 1974), which is composed of four items, was used as a measure of alcohol use problems. Respondents were defined as problem drinkers if they endorsed two or more items. Estimated measures of BAC were computed using a variation of Widmark's (1932) formula that incorporated the amount of body water (based on weight) for males and females and the range of metabolic rates found in the population (National Highway Traffic Safety Administration, 1994). Respondents reported how many drinks they usually had when drinking outside the home in the last 12 months, and the period of time they usually took to consume the drinks. Answers to these items, along with information collected about
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Table 2 Demographic, alcohol use, and drinking and driving characteristics of barroom respondents who did and did not use a designated driver (DD) Characteristics Demographic characteristics Gender Males Females Mean age (SD)* Current marital status** Single Married/living with partner Separated/divorced/widowed Ethnic/racial group White African American Other (Hispanic, Asian, etc.) Mean yearly incomea Alcohol use, and drinking and driving characteristics Mean times drank outside the home (SD)* Mean estimated BAC outside the home (SD)* CAGE problem drinker QFV categories** Infrequent/light drinkers Moderate drinkers Heavy drinkers Drove after drinking any alcohol** Drove when felt intoxicated** Rode with intoxicated driver** Arrested for DWI in last year
Used a DD (55%, n = 497)
Did not use a DD (45%, n = 405)
50% 50% 31.9 (8.9)
56% 44% 36.0 (10.3)
47% 33% 20%
34% 42% 24%
94% 2% 4% $35,001 ± 45,000
92% 2% 5% $35,001 ± $45,000
44.5 (67.7) 0.09 (0.07) 21%
37.7 (67.7) 0.06 (0.07) 20%
9% 28% 63% 73% 54% 54% 6%
24% 29% 47% 64% 44% 36% 4%
BAC = blood alcohol concentration; CAGE = CAGE questionnaire; DWI = driving while intoxicated. Income was a categorical variable with 10 possible response categories such as $5,001 to $15,000. * p < .05 by t-test (2-tailed). ** p < .05 by chi square. a
respondents' gender and weight, were used to compute respondents' estimated BACs when drinking outside the home. 1.4. Procedure 1.4.1. Computer-assisted telephone interviews Telephone numbers were purchased for the zip codes that included the areas within each city. A computer mapping program then identified most of the telephone numbers purchased and whether those numbers fell inside or outside the city limits. For households determined to be outside of the city limits, interviewers asked respondents if their households were within 1 mile of the city limits. Eligible households were restricted to those within the city and extending to 1 mile beyond. The household member reached was then asked four screening
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questions to determine which, if any, members of the household met all of the following selection criteria: 21 years of age or older; lived in the county for at least 12 months; drove a motor vehicle in the last 12 months; and consumed an alcoholic beverage in the last 12 months for other than religious purposes. If one or more members of the household met the selection criteria, one was randomly selected and asked to participate in the interview. Of 4,165 households reached, 22% of individuals refused to complete the screening questions; 33% were determined to be ineligible; and the remaining 45% completed the screener questions and were deemed eligible. Of the 1,852 eligible respondents, 3% were determined to be ineligible once the randomly selected individual was reached; 11% refused to be interviewed or completed only partial interviews; 3% had language problems; 8% could not be reached (e.g., their telephones were disconnected, they did not answer our calls, or they moved prior to being interviewed); and the remaining 75% participated in the CATI. Interviews lasted approximately 30 minutes. 1.4.2. Barroom surveys Following completion of the CATIs, barroom surveys were administered on a single Saturday evening in 34 drinking establishments across the two communities. Sampling was restricted to barrooms and to barroom areas in restaurants so the respondents would consist largely of heavier drinkers who are more likely to drink and drive and who may need to use DDs and safe rides. Participating establishments included 11 restaurants with bars, 21 bars, and 2 large dance clubs (one in each city). Of the establishments approached to participate in the survey, 26% refused; for 21% of eligible businesses, owners could not be reached, the establishments were not open the night of the survey, or other logistical problems were encountered (for example, on the night of the survey several managers had not been informed by establishment owners about the survey); and 53% of the available bars and restaurants participated. Finally, as a means of testing for the representativeness of the participating establishments relative to the nonparticipating ones, all eligible establishments in both communities studied were categorized by project staff on the basis of size of the establishment and by on-site managers regarding the average age of their clientele. No differences were found on either variable between participating versus nonparticipating establishments. Customers were recruited for the study when they first entered each establishment to limit the amount of preassessment drinking by respondents. Teams of at least two trained survey administrators were assigned to each establishment and approached every customer as they entered. As survey administrators approached customers they said: We're conducting a study to see how customers in drinking establishments feel about free public services for drinkers. We can pay you $5.00 for completing a brief, anonymous survey about free rides for drinkers and the use of designated drivers to help reduce and/or prevent drinking and driving. The coupons can be used for any nonalcoholic item at this business. When you're done with the survey, seal it in this envelope and give it back to me. I just need to ask you a couple of questions to make sure you qualify for the survey.
Respondents were required to meet the same screening criteria described above for the CATI procedures, with two exceptions. The requirement that they live within 1 mile of the city limits was waived, and participants were excluded who had recently completed a CATI
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interview. Of approximately 2,000 customers approached, 65% agreed to complete the screener questions. Of those screened, 75% were eligible for the survey. Eighty-nine percent of eligible individuals completed the written questionnaire, which took 10 to 15 minutes to complete. It had fewer items than the CATI to maximize the chances that respondents in drinking settings would complete it. 2. Results The prevalence of DD use in the last year was found to be relatively high among CATI respondents, and was even higher among respondents in the barroom sample. Thirty-three percent of the CATI respondents reported using a DD in the last year, compared to 55% of barroom survey respondents. Tables 1 and 2 display demographic variables for DD users and nonusers for the CATI and barroom samples, respectively. Although 983 barroom surveys were collected as part of this study, 81 individuals did not answer our question regarding whether or not they had used a DD in the last year. Thus, 902 cases were available for the analyses regarding the barroom survey sample (as depicted in Table 2). Bivariate analyses indicated that across both samples DD users tended to be younger and were more often single. Neither sample showed statistically significant differences for gender, ethnicity, or income. Tables 1 and 2 also present alcohol use and drinking and driving variables for each sample, and for DD users versus nonusers. For the CATI sample, shown in Table 1, there were significant differences between DD users and nonusers on all drinking behavior measures examined except for DWI arrests in the last year. DD users were more likely to drink more often outside the home, to achieve higher usual BACs when drinking outside the home, to be heavier drinkers as indicated by the QFV index, to be problem drinkers as reflected by their CAGE scores, to drive after drinking any alcohol, to drive when feeling intoxicated, and to ride with intoxicated drivers. Three other variables from the CATI interviews were examined separately and were not included in the following logistic regression analyses since they were highly related behaviors to the outcome behavior of using a DD. These variables included whether respondents served as a DD in the last 12 months, whether they engaged in other behavior to avoid DWI, and whether they engaged in other behavior to avoid riding with an intoxicated driver (RID). Sixty-five percent of DD users served as a DD, compared to 35% of nonusers, c2 (df = 1, n = 1,391) = 239.42, p < .001. DD users (97%) were also much more likely to report having used other methods in the last 12 months to avoid DWI compared to nonusers (81%), c2 (df = 1, n = 780) = 54.85, p < .001. DD users (72%) were also more likely to report using other behaviors to avoid RID compared to nonusers (35%), c2 (df = 1, n = 1,324) = 153.50, p < .001. Behaviors respondents reported to avoid DWI and/or RID included staying home, paying for a cab, asking a sober person to drive, drinking less, choosing not to drink, waiting until the effects of the alcohol wore off, walking home, and staying overnight. Findings from the barroom sample, as detailed in Table 2, show a similar pattern. DD users, relative to nonusers, were more likely to drink more often outside the home, to achieve
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higher estimated BACs when drinking outside the home, to be heavier drinkers as indicated by the QFV index, to drive after drinking any alcohol, to drive when they felt intoxicated, and to ride with intoxicated drivers in the last 12 months. In addition, DD users in the barroom sample were much more likely than nonusers to have served as a DD in the last 12 months (72% versus 38%), c2 df 1; n 867 99:82; p < :001. Due to time limitations on the barroom survey, the CATI questions regarding other behaviors respondents used to avoid DWI and RID were omitted. 2.1. Logistic regression analyses Stepwise logistic regression analyses were performed for both the CATI and barroom samples. Demographic, drinking, and drinking and driving variables listed in the tables were used to predict whether respondents used or did not use a DD in the last 12 months. Stepwise logistic regression was chosen since there were no prior expectations concerning variables that would predict DD users from nonusers. An alpha level of .05 was used as the criterion for inclusion into the model. Since respondents for both the CATI and the barroom survey were told that they could skip items they did not wish to answer, missing responses to one or more of the variables were relatively common (38% skipped at least one item on the CATI, and 43% did on the barroom survey). Thus, we used imputed values for the logistic regression analyses. Both mean and regression-based imputation resulted in the same pattern of results. For the analyses reported here, mean imputation was used. For the CATI sample, the variables that significantly predicted group membership were age, income, the number of times the respondent drank outside the home, the usual estimated BAC achieved when drinking outside the home, and the QFV index. There was a good model fit for these variables, c2 (df = 6, n = 1,391) = 377.21. Predictive success was reasonable with 77% of cases being correctly classified. Those respondents more likely to have used a DD in the last 12 months were younger OR = 0.94, 95% CI = 0.93±0.95), had more income OR = 1.06, 95% CI = 1.00±1.13), drank more often outside the home (OR = 1.006, 95% CI = 1.003±1.010), achieved a higher BAC when drinking outside the home (OR = 36,218, 95% CI = 747±1,756,830; this value is so large since the ratio is determined by single increment increases in each variable, and since BAC ranges from 0 to considerably less than 1, the ratio reflects the scaling of the BAC measure), were more likely to have ridden with an intoxicated driver (OR = 1.64, 95% CI = 1.14±2.36), and were heavier drinkers (OR = 2.25, 95% CI = 1.86±2.73), as indicated by the QFV index. For the barroom sample, the equation was similar to that found for the CATI. The overall model fit, however, was not quite as good as it was with the CATI sample, c2 (df = 5, n = 983) = 90.58, and 62% of cases were correctly predicted. Respondents more likely to have used a DD were female (OR = 1.41, 95% CI = 1.05±1.88), younger (OR = 0.96, 95% CI = 0.95, 14±0.98), heavier drinkers as indicated by the QFV index (OR = 1.65, 95% CI = 1.35 ± 2.01), those who drove after drinking any alcohol (OR = 1.42, 95% CI = 1.04 ± 1.94), and those who rode with an intoxicated driver (OR = 1.53, 95% CI = 1.14±2.03).
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3. Discussion Results for drinking and driving variables from the logistic regression for the community sample (CATI interviews) suggest that users of designated drivers tend to be at greater risk for drinking and driving than nonusers. DD users were more likely to drink more often outside the home, to achieve higher BACs when drinking outside the home, to have ridden with an intoxicated driver, and to be heavier drinkers as measured on the QFV index. This hypothesis is also supported by results from the logistic regression for the barroom sample. While the significant drinking and driving variables differed from those in the CATI analysis, they are consistent with the view that DD users are at higher risk for drinking and driving. Barroom respondents tended to be heavier drinkers according to the QFV index, to drive after drinking any alcohol, and to have ridden with an intoxicated driver. These findings contradict suggestions that DDs may not be utilized by heavy and problem drinkers (DeJong & Wallack, 1992; Wagenaar, 1992), and are consistent with an earlier study of barroom drinkers' attitudes about alternative transportation as a means of preventing DWI by Caudill, Kaufman Kantor, and Ungerleider (1990). Caudill et al. reported that heavy drinkers surveyed in barroom settings had the most positive attitudes about the potential for alternative transportation to prevent their own DWI behavior. The current findings are also consistent with two prior studies on DD use in college-student drinkers (Barr & MacKinnon, 1998; DeJong & Winsten, 1999). These studies indicated that individuals who drank more, or were heavier drinkers, were more likely to have used a DD. In addition, Barr and MacKinnon found that the number of times a respondent reported driving to a drinking destination significantly predicted DD use. In the current study, the number of times respondents reported drinking outside the home predicted DD use in the CATI and barroom samples. Our findings show that DD users, relative to nonusers, take various steps to avoid or prevent DWI and RID, such as using DDs, drinking less, walking home, and staying overnight. At the same time, our findings also show that DD users are more likely than are nonusers to engage in driving after drinking and RID behavior. These findings are consistent with another study by the current authors, which compared safe-rides users with non-saferides users (Caudill, Harding, & Moore, in press). In addition to using safe rides to avoid DWI, safe-rides users, relative to non-safe-ride users, were also more likely to have used DDs. Although they reported using safe rides and DDs to avoid DWI, safe-rides users were also more likely than non-safe-rides users to still engage in DWI and RID behavior. Consequently, future research might benefit from examining the contextual and motivational variables that distinguish between the occasions on which at-risk drinkers choose to drive when feeling intoxicated or ride with an intoxicated driver, and the occasions on which they instead take specific steps to avoid DWI and/or RID. The results of this study also showed that younger drinkers were most likely to use DDs. This result was not indicated by prior research, most likely because of the use of college age samples which were restricted to younger ages. This suggestion is consistent, however, with findings from another study of ours which showed that safe-rides users also tended to be younger drinkers (Caudill et al., in press). This pattern of results may therefore suggest that
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efforts to promote the use of DDs and safe rides in younger drinkers have been effective, although perhaps more attention should be devoted to trying to promote the use of these DWI prevention strategies in older drinkers. Acknowledgments This research was supported by a grant from the National Institute on Alcohol Abuse and Alcoholism (Grant #1-R01-AA10729). This paper was presented, in part, at the annual meeting of the Research Society on Alcoholism, San Francisco, July 1997, and at the 14th International Conference on Alcohol, Drugs and Traffic Safety, Annecy, France, September 1997. The views expressed here are those of the authors and do not necessarily reflect the views of NIAAA. References Apsler, R., Harding, W. M., & Goldfein, J. (1987). The review and assessment of designated driver programs as an alcohol countermeasure approach, final report (DOT Publication No. HS 807 108). Washington, DC: U.S. Department of Transportation, National Highway Traffic Safety Administration. Barr, A., & MacKinnon, D. P. (1998). Designated driving among college students. Journal of Studies on Alcohol, 59, 549 ± 554. Cahalan, D., Cisin, I. H., & Crossley, H. M. (1969). American drinking practices: A national study of drinking behavior and attitutes. New Brunswick, NJ: Rutgers Center of Alcohol Studies. Caudill, B. D., Harding, W. M., & Moore, B. (in press). At-risk drinkers use safe rides to avoid drinking and driving. Journal of Substance Abuse. Caudill, B. D., Kaufman Kantor, G., & Ungerleider, S. (1990). Drinking and driving prevention: Deterrence or alternative transportation for the drunk driver? Journal of Substance Abuse, 35, 61 ± 74. DeJong, W., & Wallack, L. (1992). The role of designated drivers programs in the prevention of alcohol-impaired driving: A critical reassessment. Health Education Quarterly, 19, 429 ± 442. DeJong, W., & Winsten, J. A. (1999). The use of designated drivers by U.S. college students. Journal of the American College Health, 47, 151 ± 156. Fell, J., Voas, R. B., & Lange, J. E. (1997). Designated driver concept: Extent of use in the USA. Journal of Traffic Medicine, 25, 109 ± 114. Gallup, G. (1987). Designated driver program: Who holds the key to safety. Alcoholism & Addiction, 7, 16. Harding, W. M., Apsler, R., & Farrah, M. (1994). A guide to developing a community based designated driver program (DOT Publication No. HS 808 137). Washington, DC: U.S. Department of Transportation, National Highway Traffic Safety Administration. Hedlund, J. (1997). Partners in progress: United States impaired driving programs for the next decade. In C. Mercier-Guyon (Ed.), Proceedings of the 14th International Conference on Alcohol, Drugs, and Traffic Safety, vol. 1 (pp. 29 ± 35). Annecy, France: Centre d'Etudes et de Recherches en Medecine du Trafic. Knight, S. M., Glascoff, M. A., & Rikard, G. L. (1993). On being a designated driver: A qualitative investigation of underage college student perceptions. Journal of College Student Development, 34, 425 ± 431. Martin, S. E. (1996), Who are the designated drivers? Poster session presented at the annual meeting of the Research Society on Alcoholism, Washington, DC (June). Mayfield, D., McLeod, G., & Hall, P. (1974). The CAGE questionnaire: Validation of a new alcoholism instrument. American Journal of Psychiatry, 13, 1121 ± 1123. National Highway Traffic Safety Administration. (1994). Computing a BAC estimate. Washington, DC: U.S. Department of Transportation, National Highway Traffic Safety Administration.
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National Highway Traffic Safety Administration. (1999). National survey of drinking and driving attitudes and behavior: 1997 (DOT Publication No. HS 808844). Washington, DC: U.S. Department of Transportation, National Highway Traffic Safety Administration. Schwartz, R. H., & Little, D. L. (1997). Let's party tonight: Drinking patterns and breath alcohol values at high school parties. Family Medicine, 29, 326 ± 331. Wagenaar, A. C. (1992). Designated driver programs: A commentary on the DeJong and Wallack article. Health Education Quarterly, 19, 443 ± 445. Widmark, E. (1932). Die theoretischen grundiagen und die praktische verwendbarkeit der geriehtlich-medizinishen alkoholbestimmung. Berlin, Germany: Uragn and Schwarzenberg. Winsten, J. A. (1994). Promoting designated drivers: The Harvard Alcohol Project. American Journal of Preventive Medicine, 10, 11 ± 14. Zador, P. L. (1991). Alcohol-related relative risk of fatal driver injury in relation to driver age and sex. Journal of Studies on Alcohol, 52, 302 ± 310.
DWI prevention: Profiles of drinkers who use designated drivers Barry D. Caudilla,*, Wayne M. Hardingb,c, Brent A. Moorea a
Center for Studies on Alcohol, Westat, 1650 Research Blvd., Rockville, MD 20850, USA b Social Science Research and Evaluation, Burlington, MA USA c Harvard Medical School, Cambridge, MA USA
Abstract The effectiveness of designated driver (DD) use in preventing driving while intoxicated (DWI) depends on whether drinkers at risk for DWI use DDs. Bivariate and logistic regression analyses conducted on data from 1,391 Computer-Assisted Telephone Interviews (CATIs) and from 902 barroom patron surveys showed that DD users, compared to nonusers, tended to be at-risk, heavier drinkers. For example, logistic regression using the CATI sample indicated that DD users were more likely to drink more often outside the home, to achieve higher blood alcohol concentrations (BACs) when drinking outside the home, to ride with intoxicated drivers (RID), and to be heavy drinkers on D. Cahalan et al.'s (1969) Quantity-Frequency-Variability (QFV) index. Similarly, logistic regression using the barroom sample showed that DD users tended to be heavy drinkers on the QFV index, and were more likely to drive after drinking and to ride with intoxicated drivers. Additional analyses showed that DD users also were more likely than nonusers to engage in other behavior to avoid DWI, such as drinking less, waiting to drive until the effects of alcohol diminish, walking home, and staying overnight. These results are consistent with other findings from a related study by the current authors which showed that at-risk drinkers also used free safe (taxi) rides to avoid DWI, however were still more likely to report DWI and RID behavior (B. D. Caudill, W. M. Harding, & B. Moore, in press). Consequently, DWI prevention efforts may be improved by future research aimed at learning why such at-risk drinkers sometimes take steps to avoid DWI and sometimes do not. D 2001 Elsevier Science Ltd. All rights reserved. Keywords: Designated drivers; Safe rides; Driving while intoxicated; Riding with intoxicated drivers; Barroom surveys
* Corresponding author. E-mail address: [email protected] (B.D. Caudill). 0306-4603/01/$ ± see front matter D 2001 Elsevier Science Ltd. All rights reserved. PII: S 0 3 0 6 - 4 6 0 3 ( 0 0 ) 0 0 0 9 7 - 6
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In discussing the growing popularity of designated driver programs (DDPs), and the increase in the use of designated drivers (DDs) in the U.S. over the last decade, Hedlund (1997) suggested that the term ``one for the road'' has now been replaced by a question about who will serve as the DD. In spite of the widespread promotion of DD use in various local and national publicity campaigns in the U.S., the use of DDs by many drinkers, and a high degree of public enthusiasm about the efficacy of DD use in reducing driving while intoxicated (DWI), little is known about the characteristics of DD users. A central question pertinent to the efficacy of DD use in preventing DWI is whether individuals at high risk for DWI are using DDs. If not, programs designed to promote DD use will be less effective in preventing DWI. The current study was designed to profile individuals who use DDs. The study is part of a longitudinal assessment of the impact of promoting alternative transportation measures such as DDs and ``safe rides'' (SRs; a free ride home from a nondrinking driver such as a cab company or other organization) in preventing DWI. For this study, a designated driver (DD) was defined as one person in a couple or group who does not drink any alcohol in order to drive his/her companions home safely. DDPs have become a commonly used approach for communities trying to prevent DWI. There are hundreds of local DDPs in the U.S. (Apsler, Harding, & Goldfein, 1987; DeJong & Wallack, 1992; Harding, Apsler, & Farrah, 1994). In addition, national organizations such as the Harvard Alcohol Project (Winsten, 1994), Mothers Against Drunk Driving, and the National Group Rides and Designated Drivers program promote the use of DDs. Support for alternative transportation strategies as a means of preventing DWI is extensive, with national approval ratings as high as 91% (Gallup, 1987). In addition, results from a random digit-dial telephone survey of 1,391 drinkers in two Maryland cities, as part of the current project, showed that respondents believed that DDs were very effective in reducing DWI. Their mean response was 8.3 on a scale item about DD effectiveness that ranged from 0 (not at all effective) to 10 (very effective). The concept of using a DD has become a common part of everyday language as well as a frequently used means to avoid DWI (Barr & MacKinnon, 1998; DeJong & Winsten, 1999; National Highway Traffic Safety Administration, 1999). Several recent studies have reported high levels of designated driver use. In a study of college students, Barr and MacKinnon (1998) found that 86% of respondents reported that they had used a DD at some time in their lives. DeJong and Winsten (1999) found that 37% of college students surveyed reported using a DD in the last 30 days. In the National Survey of Drinking and Driving Attitudes and Behaviors (National Highway Traffic Safety Administration, 1999), 37% of respondents reported using a DD in the last year, as did 57% of individuals 21±29 years of age. In a recent national roadside survey, 25% of drivers reported serving as a DD on that evening (Fell, Voas, & Lange, 1997). Although the concept of using DDs is popular and many drinkers report using DDs, the potential utility of DD use has also been criticized (DeJong & Wallack, 1992). A major criticism has been the belief that individuals who use DDs are most likely those with low to moderate levels of DWI risk (DeJong & Wallack, 1992; Wagenaar, 1992). Since risk of a crash increases exponentially as a function of increasing blood alcohol concentration (BAC; Zador, 1991) and the frequency with which drinkers drink to the point of intoxication, it is more important for DWI interventions to impact heavy drinkers
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and individuals who achieve higher BACs, rather than light to moderate drinkers. There is, therefore, a clear need to learn whether drinkers who are at the greatest risk for DWI use DDs to prevent DWI. Prior research on DDs and DD users has primarily focused on who serves as a DD (Knight, Glascoff, & Rikard, 1993; Martin, 1996; Schwartz & Little, 1997). Knight et al. examined the attitudes and beliefs of college student DDs using focus group interviews, while Schwartz and Little surveyed the beliefs of students who attended high school parties. Martin's study used the National Survey of Drinking and Driving Attitudes and Behavior: 1993 to examine differences between respondents who reported serving as a DD in the last year and those who did not. She reported that DDs tended to be younger, female, single, and more educated. In addition, those serving as DDs were much more likely to have used a DD in the last year. Two previous studies have profiled characteristics of DD users. DeJong and Winsten (1999) recently described characteristics of DD users from a national sample of collegestudent drinkers. Respondents who reported using a DD in the last 30 days were more likely to be older than 21, White, single, and not living with children at home. DD users were also more likely to binge drink, defined as having five or more drinks on a single occasion. In another study of college-student drinkers, Barr and MacKinnon (1998) also found that DD use was predicted by heavy drinking and by a high frequency of respondents driving to drinking destinations. The latter authors also found that women were more likely to use DDs than men. These two studies, however, were limited to samples of college students and therefore miss a large proportion of the general population, many of whom are at high risk for DWI. The current study was designed to further profile users of DDs and allows us to directly address the important question of whether drinkers at risk for DWI actually use DDs to prevent DWI. By collecting community- and barroom-level data on random samples of drinkers, the current study also benefits from examining populations of drinkers that are much more representative of drinkers in general, and drinkers at risk for DWI in particular, than samples of drinkers previously examined in other studies. Drinkers profiled here include community-level drinkers, as assessed through random digit-dialed computer-assisted telephone interviews (CATIs), and more at-risk drinkers, as assessed through the conduct of anonymous barroom surveys. 1. Method 1.1. Context of data collection Data for this paper come from 1,391 computer-assisted telephone interviews (CATIs) and 983 barroom surveys that were conducted in two Maryland communities. Data examined here were collected as part of a baseline assessment for an ongoing 5-year longitudinal study funded by the National Institute on Alcohol Abuse and Alcoholism (NIAAA) on the effects of introducing an alternative transportation program for drinkers. The program provides incentives for designated drivers in public drinking establishments and free safe
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rides home (using taxis) for drinking drivers and their passengers. The CATI sample was chosen to represent individuals in the community who drink. The barroom sample was chosen to provide a sample of drinkers at greater risk for DWI. As a result, respondents in the barroom sample tended to be younger, single, heavier drinkers, and were more likely to drink and drive. 1.2. Selecting generalizable sampling communities An important consideration for the current study was to select study site sampling communities with characteristics that would make study results generalizable to many other communities nationally. It was also important for the current alternative transportation intervention project to select experimental and control site communities that were of sufficient size (at least 50,000 citizens) to have taxi companies available to provide safe rides, that were located nearby the researchers' offices, and whose leaders were willing to host the respective study interventions. With these factors in mind, we chose the study sites of Frederick and Hagerstown, Maryland. To test the potential generalizibility of study findings to other communities nationally, we compared demographic characteristics (i.e., sex, race, marital status, educational level, income, and age) for Frederick and Hagerstown to other communities of similar size across the country using 1990 Census data. In total, there are 396 urbanized areas in the U.S. that have populations of at least 50,000 citizens, but data only exists for 290 of these communities in the 1990 Census. For our statistical comparisons of Frederick and Hagerstown with other urbanized areas, the comparison sample was limited to urbanized areas with populations of less than 150,000 (N = 171), which included the cities of Frederick (58,427) and Hagerstown (70,158). Findings showed that no variables differed between Hagerstown and other national communities examined, and only one variable was found to differ between Frederick and urbanized area averages. The median income for Frederick was significantly higher ($38,283, p < .05) than was that of the national sample ($26,804). Thus, with this minor exception for Frederick, the current study communities are clearly representative of urbanized areas nationally with populations from 50,000 to 150,000 citizens. 1.3. CATI and barroom survey measures The CATIs and the barroom surveys requested information about the following major content areas: socio-demographics; alcohol use; items used to compute respondents' usual blood alcohol concentration levels (BACs) in different contexts, such as when they drink outside the home in general, or on occasions when they use a designated driver or safe ride; items indicative of alcohol use problems; drinking and driving behavior; riding with intoxicated drivers; and behaviors other than the use of DDs or SRs used to avoid DWI and riding with intoxicated drivers. Tables 1 and 2 present all variables examined for this paper. The timeframe for DWI behaviors examined, such as the number of times the respondent drove when feeling intoxicated, was the last 12 months. A generalized form of the Quantity-Frequency-Variability Index (QFV; Cahalan, Cisin, & Crossley, 1969) was used to measure the extent of alcohol use. For this measure, respondents
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Table 1 Demographic, alcohol use, and drinking and driving characteristics of CATI respondents who did and did not use a designated driver (DD) Characteristics Demographic characteristics Gender Males Females Mean age (SD)* Current marital status** Single Married/living with partner Separated/divorced/widowed Ethnic/racial group White African American Other (Hispanic, Asian, etc.) Mean yearly incomea Alcohol use, and drinking and driving characteristics Mean times drank outside the home (SD)* Mean estimated BAC outside the home (SD)* CAGE problem drinker** QFV categories** Infrequent/light drinkers Moderate drinkers Heavy drinkers Drove after drinking any alcohol** Drove when felt intoxicated** Rode with intoxicated driver** Arrested for DWI in last year
Used a DD (33%, n = 455)
Did not use a DD (67%, n = 936)
52% 48% 35.9 (10.2)
45% 55% 45.5 (14.4)
24% 54% 22%
13% 63% 25%
93% 4% 4% $35,001 ± $45,000
92% 5% 3% $35,001 ± $45,000
35.3 (44.8) 0.05 (0.03) 12%
17.2 (37.0) 0.02 (0.05) 4%
28% 34% 37% 65% 31% 27% < 1%
62% 18% 9% 47% 11% 10% < 1%
CATI = computer-assisted telephone interviews; BAC = blood alcohol concentration; CAGE = CAGE questionnaire; QFV = Quantity-Frequency-Variability index; DWI = driving while intoxicated. a Income was a categorical variable with 10 possible response categories such as $5,001 to $15,000. * p < .05 by t-test (2-tailed). ** p < .05 by chi square.
were asked questions about their usual patterns of drinking behavior regardless of beverage type. The QFV measure places drinkers into one of the four following drinking habits categories: infrequent, light, moderate, or heavy drinkers. The CAGE questionnaire (Mayfield, McLeod, & Hall, 1974), which is composed of four items, was used as a measure of alcohol use problems. Respondents were defined as problem drinkers if they endorsed two or more items. Estimated measures of BAC were computed using a variation of Widmark's (1932) formula that incorporated the amount of body water (based on weight) for males and females and the range of metabolic rates found in the population (National Highway Traffic Safety Administration, 1994). Respondents reported how many drinks they usually had when drinking outside the home in the last 12 months, and the period of time they usually took to consume the drinks. Answers to these items, along with information collected about
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Table 2 Demographic, alcohol use, and drinking and driving characteristics of barroom respondents who did and did not use a designated driver (DD) Characteristics Demographic characteristics Gender Males Females Mean age (SD)* Current marital status** Single Married/living with partner Separated/divorced/widowed Ethnic/racial group White African American Other (Hispanic, Asian, etc.) Mean yearly incomea Alcohol use, and drinking and driving characteristics Mean times drank outside the home (SD)* Mean estimated BAC outside the home (SD)* CAGE problem drinker QFV categories** Infrequent/light drinkers Moderate drinkers Heavy drinkers Drove after drinking any alcohol** Drove when felt intoxicated** Rode with intoxicated driver** Arrested for DWI in last year
Used a DD (55%, n = 497)
Did not use a DD (45%, n = 405)
50% 50% 31.9 (8.9)
56% 44% 36.0 (10.3)
47% 33% 20%
34% 42% 24%
94% 2% 4% $35,001 ± 45,000
92% 2% 5% $35,001 ± $45,000
44.5 (67.7) 0.09 (0.07) 21%
37.7 (67.7) 0.06 (0.07) 20%
9% 28% 63% 73% 54% 54% 6%
24% 29% 47% 64% 44% 36% 4%
BAC = blood alcohol concentration; CAGE = CAGE questionnaire; DWI = driving while intoxicated. Income was a categorical variable with 10 possible response categories such as $5,001 to $15,000. * p < .05 by t-test (2-tailed). ** p < .05 by chi square. a
respondents' gender and weight, were used to compute respondents' estimated BACs when drinking outside the home. 1.4. Procedure 1.4.1. Computer-assisted telephone interviews Telephone numbers were purchased for the zip codes that included the areas within each city. A computer mapping program then identified most of the telephone numbers purchased and whether those numbers fell inside or outside the city limits. For households determined to be outside of the city limits, interviewers asked respondents if their households were within 1 mile of the city limits. Eligible households were restricted to those within the city and extending to 1 mile beyond. The household member reached was then asked four screening
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questions to determine which, if any, members of the household met all of the following selection criteria: 21 years of age or older; lived in the county for at least 12 months; drove a motor vehicle in the last 12 months; and consumed an alcoholic beverage in the last 12 months for other than religious purposes. If one or more members of the household met the selection criteria, one was randomly selected and asked to participate in the interview. Of 4,165 households reached, 22% of individuals refused to complete the screening questions; 33% were determined to be ineligible; and the remaining 45% completed the screener questions and were deemed eligible. Of the 1,852 eligible respondents, 3% were determined to be ineligible once the randomly selected individual was reached; 11% refused to be interviewed or completed only partial interviews; 3% had language problems; 8% could not be reached (e.g., their telephones were disconnected, they did not answer our calls, or they moved prior to being interviewed); and the remaining 75% participated in the CATI. Interviews lasted approximately 30 minutes. 1.4.2. Barroom surveys Following completion of the CATIs, barroom surveys were administered on a single Saturday evening in 34 drinking establishments across the two communities. Sampling was restricted to barrooms and to barroom areas in restaurants so the respondents would consist largely of heavier drinkers who are more likely to drink and drive and who may need to use DDs and safe rides. Participating establishments included 11 restaurants with bars, 21 bars, and 2 large dance clubs (one in each city). Of the establishments approached to participate in the survey, 26% refused; for 21% of eligible businesses, owners could not be reached, the establishments were not open the night of the survey, or other logistical problems were encountered (for example, on the night of the survey several managers had not been informed by establishment owners about the survey); and 53% of the available bars and restaurants participated. Finally, as a means of testing for the representativeness of the participating establishments relative to the nonparticipating ones, all eligible establishments in both communities studied were categorized by project staff on the basis of size of the establishment and by on-site managers regarding the average age of their clientele. No differences were found on either variable between participating versus nonparticipating establishments. Customers were recruited for the study when they first entered each establishment to limit the amount of preassessment drinking by respondents. Teams of at least two trained survey administrators were assigned to each establishment and approached every customer as they entered. As survey administrators approached customers they said: We're conducting a study to see how customers in drinking establishments feel about free public services for drinkers. We can pay you $5.00 for completing a brief, anonymous survey about free rides for drinkers and the use of designated drivers to help reduce and/or prevent drinking and driving. The coupons can be used for any nonalcoholic item at this business. When you're done with the survey, seal it in this envelope and give it back to me. I just need to ask you a couple of questions to make sure you qualify for the survey.
Respondents were required to meet the same screening criteria described above for the CATI procedures, with two exceptions. The requirement that they live within 1 mile of the city limits was waived, and participants were excluded who had recently completed a CATI
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interview. Of approximately 2,000 customers approached, 65% agreed to complete the screener questions. Of those screened, 75% were eligible for the survey. Eighty-nine percent of eligible individuals completed the written questionnaire, which took 10 to 15 minutes to complete. It had fewer items than the CATI to maximize the chances that respondents in drinking settings would complete it. 2. Results The prevalence of DD use in the last year was found to be relatively high among CATI respondents, and was even higher among respondents in the barroom sample. Thirty-three percent of the CATI respondents reported using a DD in the last year, compared to 55% of barroom survey respondents. Tables 1 and 2 display demographic variables for DD users and nonusers for the CATI and barroom samples, respectively. Although 983 barroom surveys were collected as part of this study, 81 individuals did not answer our question regarding whether or not they had used a DD in the last year. Thus, 902 cases were available for the analyses regarding the barroom survey sample (as depicted in Table 2). Bivariate analyses indicated that across both samples DD users tended to be younger and were more often single. Neither sample showed statistically significant differences for gender, ethnicity, or income. Tables 1 and 2 also present alcohol use and drinking and driving variables for each sample, and for DD users versus nonusers. For the CATI sample, shown in Table 1, there were significant differences between DD users and nonusers on all drinking behavior measures examined except for DWI arrests in the last year. DD users were more likely to drink more often outside the home, to achieve higher usual BACs when drinking outside the home, to be heavier drinkers as indicated by the QFV index, to be problem drinkers as reflected by their CAGE scores, to drive after drinking any alcohol, to drive when feeling intoxicated, and to ride with intoxicated drivers. Three other variables from the CATI interviews were examined separately and were not included in the following logistic regression analyses since they were highly related behaviors to the outcome behavior of using a DD. These variables included whether respondents served as a DD in the last 12 months, whether they engaged in other behavior to avoid DWI, and whether they engaged in other behavior to avoid riding with an intoxicated driver (RID). Sixty-five percent of DD users served as a DD, compared to 35% of nonusers, c2 (df = 1, n = 1,391) = 239.42, p < .001. DD users (97%) were also much more likely to report having used other methods in the last 12 months to avoid DWI compared to nonusers (81%), c2 (df = 1, n = 780) = 54.85, p < .001. DD users (72%) were also more likely to report using other behaviors to avoid RID compared to nonusers (35%), c2 (df = 1, n = 1,324) = 153.50, p < .001. Behaviors respondents reported to avoid DWI and/or RID included staying home, paying for a cab, asking a sober person to drive, drinking less, choosing not to drink, waiting until the effects of the alcohol wore off, walking home, and staying overnight. Findings from the barroom sample, as detailed in Table 2, show a similar pattern. DD users, relative to nonusers, were more likely to drink more often outside the home, to achieve
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higher estimated BACs when drinking outside the home, to be heavier drinkers as indicated by the QFV index, to drive after drinking any alcohol, to drive when they felt intoxicated, and to ride with intoxicated drivers in the last 12 months. In addition, DD users in the barroom sample were much more likely than nonusers to have served as a DD in the last 12 months (72% versus 38%), c2 df 1; n 867 99:82; p < :001. Due to time limitations on the barroom survey, the CATI questions regarding other behaviors respondents used to avoid DWI and RID were omitted. 2.1. Logistic regression analyses Stepwise logistic regression analyses were performed for both the CATI and barroom samples. Demographic, drinking, and drinking and driving variables listed in the tables were used to predict whether respondents used or did not use a DD in the last 12 months. Stepwise logistic regression was chosen since there were no prior expectations concerning variables that would predict DD users from nonusers. An alpha level of .05 was used as the criterion for inclusion into the model. Since respondents for both the CATI and the barroom survey were told that they could skip items they did not wish to answer, missing responses to one or more of the variables were relatively common (38% skipped at least one item on the CATI, and 43% did on the barroom survey). Thus, we used imputed values for the logistic regression analyses. Both mean and regression-based imputation resulted in the same pattern of results. For the analyses reported here, mean imputation was used. For the CATI sample, the variables that significantly predicted group membership were age, income, the number of times the respondent drank outside the home, the usual estimated BAC achieved when drinking outside the home, and the QFV index. There was a good model fit for these variables, c2 (df = 6, n = 1,391) = 377.21. Predictive success was reasonable with 77% of cases being correctly classified. Those respondents more likely to have used a DD in the last 12 months were younger OR = 0.94, 95% CI = 0.93±0.95), had more income OR = 1.06, 95% CI = 1.00±1.13), drank more often outside the home (OR = 1.006, 95% CI = 1.003±1.010), achieved a higher BAC when drinking outside the home (OR = 36,218, 95% CI = 747±1,756,830; this value is so large since the ratio is determined by single increment increases in each variable, and since BAC ranges from 0 to considerably less than 1, the ratio reflects the scaling of the BAC measure), were more likely to have ridden with an intoxicated driver (OR = 1.64, 95% CI = 1.14±2.36), and were heavier drinkers (OR = 2.25, 95% CI = 1.86±2.73), as indicated by the QFV index. For the barroom sample, the equation was similar to that found for the CATI. The overall model fit, however, was not quite as good as it was with the CATI sample, c2 (df = 5, n = 983) = 90.58, and 62% of cases were correctly predicted. Respondents more likely to have used a DD were female (OR = 1.41, 95% CI = 1.05±1.88), younger (OR = 0.96, 95% CI = 0.95, 14±0.98), heavier drinkers as indicated by the QFV index (OR = 1.65, 95% CI = 1.35 ± 2.01), those who drove after drinking any alcohol (OR = 1.42, 95% CI = 1.04 ± 1.94), and those who rode with an intoxicated driver (OR = 1.53, 95% CI = 1.14±2.03).
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3. Discussion Results for drinking and driving variables from the logistic regression for the community sample (CATI interviews) suggest that users of designated drivers tend to be at greater risk for drinking and driving than nonusers. DD users were more likely to drink more often outside the home, to achieve higher BACs when drinking outside the home, to have ridden with an intoxicated driver, and to be heavier drinkers as measured on the QFV index. This hypothesis is also supported by results from the logistic regression for the barroom sample. While the significant drinking and driving variables differed from those in the CATI analysis, they are consistent with the view that DD users are at higher risk for drinking and driving. Barroom respondents tended to be heavier drinkers according to the QFV index, to drive after drinking any alcohol, and to have ridden with an intoxicated driver. These findings contradict suggestions that DDs may not be utilized by heavy and problem drinkers (DeJong & Wallack, 1992; Wagenaar, 1992), and are consistent with an earlier study of barroom drinkers' attitudes about alternative transportation as a means of preventing DWI by Caudill, Kaufman Kantor, and Ungerleider (1990). Caudill et al. reported that heavy drinkers surveyed in barroom settings had the most positive attitudes about the potential for alternative transportation to prevent their own DWI behavior. The current findings are also consistent with two prior studies on DD use in college-student drinkers (Barr & MacKinnon, 1998; DeJong & Winsten, 1999). These studies indicated that individuals who drank more, or were heavier drinkers, were more likely to have used a DD. In addition, Barr and MacKinnon found that the number of times a respondent reported driving to a drinking destination significantly predicted DD use. In the current study, the number of times respondents reported drinking outside the home predicted DD use in the CATI and barroom samples. Our findings show that DD users, relative to nonusers, take various steps to avoid or prevent DWI and RID, such as using DDs, drinking less, walking home, and staying overnight. At the same time, our findings also show that DD users are more likely than are nonusers to engage in driving after drinking and RID behavior. These findings are consistent with another study by the current authors, which compared safe-rides users with non-saferides users (Caudill, Harding, & Moore, in press). In addition to using safe rides to avoid DWI, safe-rides users, relative to non-safe-ride users, were also more likely to have used DDs. Although they reported using safe rides and DDs to avoid DWI, safe-rides users were also more likely than non-safe-rides users to still engage in DWI and RID behavior. Consequently, future research might benefit from examining the contextual and motivational variables that distinguish between the occasions on which at-risk drinkers choose to drive when feeling intoxicated or ride with an intoxicated driver, and the occasions on which they instead take specific steps to avoid DWI and/or RID. The results of this study also showed that younger drinkers were most likely to use DDs. This result was not indicated by prior research, most likely because of the use of college age samples which were restricted to younger ages. This suggestion is consistent, however, with findings from another study of ours which showed that safe-rides users also tended to be younger drinkers (Caudill et al., in press). This pattern of results may therefore suggest that
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efforts to promote the use of DDs and safe rides in younger drinkers have been effective, although perhaps more attention should be devoted to trying to promote the use of these DWI prevention strategies in older drinkers. Acknowledgments This research was supported by a grant from the National Institute on Alcohol Abuse and Alcoholism (Grant #1-R01-AA10729). This paper was presented, in part, at the annual meeting of the Research Society on Alcoholism, San Francisco, July 1997, and at the 14th International Conference on Alcohol, Drugs and Traffic Safety, Annecy, France, September 1997. The views expressed here are those of the authors and do not necessarily reflect the views of NIAAA. References Apsler, R., Harding, W. M., & Goldfein, J. (1987). The review and assessment of designated driver programs as an alcohol countermeasure approach, final report (DOT Publication No. HS 807 108). Washington, DC: U.S. Department of Transportation, National Highway Traffic Safety Administration. Barr, A., & MacKinnon, D. P. (1998). Designated driving among college students. Journal of Studies on Alcohol, 59, 549 ± 554. Cahalan, D., Cisin, I. H., & Crossley, H. M. (1969). American drinking practices: A national study of drinking behavior and attitutes. New Brunswick, NJ: Rutgers Center of Alcohol Studies. Caudill, B. D., Harding, W. M., & Moore, B. (in press). At-risk drinkers use safe rides to avoid drinking and driving. Journal of Substance Abuse. Caudill, B. D., Kaufman Kantor, G., & Ungerleider, S. (1990). Drinking and driving prevention: Deterrence or alternative transportation for the drunk driver? Journal of Substance Abuse, 35, 61 ± 74. DeJong, W., & Wallack, L. (1992). The role of designated drivers programs in the prevention of alcohol-impaired driving: A critical reassessment. Health Education Quarterly, 19, 429 ± 442. DeJong, W., & Winsten, J. A. (1999). The use of designated drivers by U.S. college students. Journal of the American College Health, 47, 151 ± 156. Fell, J., Voas, R. B., & Lange, J. E. (1997). Designated driver concept: Extent of use in the USA. Journal of Traffic Medicine, 25, 109 ± 114. Gallup, G. (1987). Designated driver program: Who holds the key to safety. Alcoholism & Addiction, 7, 16. Harding, W. M., Apsler, R., & Farrah, M. (1994). A guide to developing a community based designated driver program (DOT Publication No. HS 808 137). Washington, DC: U.S. Department of Transportation, National Highway Traffic Safety Administration. Hedlund, J. (1997). Partners in progress: United States impaired driving programs for the next decade. In C. Mercier-Guyon (Ed.), Proceedings of the 14th International Conference on Alcohol, Drugs, and Traffic Safety, vol. 1 (pp. 29 ± 35). Annecy, France: Centre d'Etudes et de Recherches en Medecine du Trafic. Knight, S. M., Glascoff, M. A., & Rikard, G. L. (1993). On being a designated driver: A qualitative investigation of underage college student perceptions. Journal of College Student Development, 34, 425 ± 431. Martin, S. E. (1996), Who are the designated drivers? Poster session presented at the annual meeting of the Research Society on Alcoholism, Washington, DC (June). Mayfield, D., McLeod, G., & Hall, P. (1974). The CAGE questionnaire: Validation of a new alcoholism instrument. American Journal of Psychiatry, 13, 1121 ± 1123. National Highway Traffic Safety Administration. (1994). Computing a BAC estimate. Washington, DC: U.S. Department of Transportation, National Highway Traffic Safety Administration.
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