Measuring impaired driving behaviors of college students: development and reliability of the impaired driving assessment

American Journal of Health Studies, Winter, 2002 by Stuart L. Usdan, Joseph E. Schumacher, Cecelia McNamara, Jeffrey M. Bellis

Abstract: The Impaired Driving Assessment (IDA) was developed to collect detailed drinking and driving information over a one-month period. Based on the Timeline Followback assessment, the IDA provides a comprehensive account of impaired driving to identify those at risk for impaired driving, as well as measure the effect of impaired driving prevention programs. Participants consisted of college students who reported drinking and driving at least twice during the previous month on a screening questionnaire. Results demonstrated that impaired driving behaviors reported on the IDA have good test-retest (N=41) and interrater (N=40) reliability, with Pearson correlation coefficients ranging from r = .76 to .96 and r = .73 to .94 respectively.

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Drinking and driving is a major public health problem in the United States, causing more than 300,000 injuries each year, nearly 16,000 deaths, and one alcohol-related fatality every 33 minutes (National Highway Traffic and Safety Administration [NHTSA], 1999). According to the Centers for Disease Control (1998), motor vehicle crashes are the leading cause of death for people aged 15-20. However, the alcohol-related fatality rates for 18-, 19-, and 20-year-olds are almost twice that of the population over 21 years of age (NHTSA, 1999). Research has shown that the combination of inexperience with drinking alcohol and limited driving experience lead young adults to be at a high risk for automobile crashes (Hingson et al., 1994).

The widespread use of alcohol among college students is a major health problem with a broad array of associated negative consequences (Wechsler & Kuo, 2000). Impaired driving can be viewed as the most serious of alcohol-related problems because of its potential for extreme negative outcomes such as driving under the influence (DUI) arrests, injuries, and deaths. Recent data from both the Core Institute Study (Presley et al., 1996) and Youth Risk Behavior Surveillance System (YRBSS) studies (CDC, 1997) reveal that more than 25% of college students surveyed reported that they had driven after drinking. Additionally, the Harvard College Alcohol Studies (CAS) have shown that impaired driving among college students has increased in frequency from 1994 to 1997 (Wechsler et al., 1998).

In recent years, numerous assessment methods have been employed to document the prevalence of alcohol consumption among college students. Past research has relied on the modification of existing measures such as the Michigan Alcoholism Screening Test (MAST), Alcohol Use Disorders Identification Test (AUDIT), and CAGE instruments to study college students (Cohen and Vinson, 1995; Heck and Williams, 1995; Samet et al., 1996; Seizer, 1971). However, other studies have developed assessment tools specific to college students such as the Harvard College Alcohol Study, Core, and College Alcohol Problem Scale (CAPS) (O'Hare, 1997; Presley et al., 1996; Wechsler et al., 1994). Because college students are distinguished from other groups in their widespread use of alcohol and the role alcohol plays in the college environment, existing instruments that collect information on alcohol consumption and associated negative consequences lack measurement specific to drinking and driving in this population.

The Timeline Followback method (TLFB) relies on an individual's ability to retrospectively reconstruct his or her behavior (e.g., impaired driving episodes) over a specific time interval. A calendar representing the specified time period is used to aid the individual with reconstruction of events (Sobell et al., 1980). Incorporated into the TLFB method are certain recall-enhancing techniques such as anchoring (marking salient events on the calendar) and identifying patterns of drinking behavior (Sobell et al., 1988). Advantages to using a TLFB approach include easy identification of specific episodes of target behaviors (i.e., impaired driving) and a detailed assessment of the amount and types of alcohol consumed.

Although originally developed as an assessment tool for alcohol consumption, the TLFB has been adapted for a wide range of health-related behaviors. The TLFB assessment has been used to collect data on other substances of abuse such as marijuana, cocaine, heroin, and inhalants as well as alcohol (Ehrman and Robbins, 1994). In a study by Weinhardt et al. (1998), a modified version of the TLFB to assess HIV-related sexual behaviors was found to have high (rho range = .86 to .97) test-retest reliability on multiple variables. The TLFB was similarly modified in a study to determine condom use among gay-bisexual male substance abusers (Crosby et al., 1996). For the purposes of this study, the TLFB calendar method was adapted and expanded in order to collect more detailed information on alcohol use and subsequent impaired driving behaviors among college students.

The TLFB assessment method has been shown to be a psychometrically sound method for obtaining retrospective estimates of alcohol consumption (Sobell and Sobell, 1992), but has never been used to assess drinking and driving behavior. Past reliability studies of the TLFB assessment with problem drinkers (Cohen and Vinson, 1995; Maisto et al., 1979; Sobell et al., 1996), normal drinkers (Sobell et al., 1988), and college students (Cohen and Vinson, 1995; Connors et al., 1985; Sobell et al., 1986; Weinhardt et al., 1998) have yielded high estimates of reliability (See Table 1).