Thirty-day self-reported risky driving behaviors of ADHD and non-ADHD drivers

Abstract

The present study aims to compare differences in reported risky driving behaviors of drivers – males and females – having and not having Attention Deficit Hyperactivity Disorder (ADHD), by using a checklist of driving behaviors based on the Driving Behavior Questionnaire (DBQ). Unlike the studies which employ the DBQ by asking the subjects to fill the questionnaire once, in this present study, the participants were asked to report their behaviors on a daily basis for 30 consequent days. The checklist included two factors of risky driving behavior: Violation and Faults. Thirty-eight drivers – 10 males and 9 females with ADHD, and 9 males and 10 females without ADHD (N-ADHD) as control groups – participated in the study. The results showed that the mean of the unsafe behaviors of ADHD was higher, i.e., less safe driving, compared to that of N-ADHD. However, a statistically significant effect was found only between male ADHD and male N-ADHD for the Faults. In order to check the effect of the length of the study, the 30 days duration of the research was divided into three consecutive periods. The reported driving habits of the female ADHD showed safer behaviors than those of the males. Unlike the findings of N-ADHD of both genders, which showed a tendency towards safer driving reports in the three periods, both genders of the ADHD showed higher rates of Faults, i.e., a decrease in safety driving reports, in the three periods. The findings suggest that ADHD drivers differ from the N-ADHD drivers in making driving mistakes, i.e., Faults, due to their lack of sustained attention, but not in making Violations. However, some of the results in the present study were not very strong. Possible explanations for this as well as methodological considerations are discussed, and further research is suggested.

Introduction

There is extensive literature on high-risk driving populations, which states that human factors, in addition to vehicular and environmental factors, are the main contributors to Motor Vehicle Collisions (MVCs) (United States General Accounting Office, 2003).

Empirical studies indicate that inattention is among the most common contributors to traffic crashes. Any disorder that markedly impairs attention would elevate one's risk for crashes and additional adverse driving outcomes (Lam, 2002, Russell et al., 2007). Data of traffic crashes collected by the United States General Accounting Office (2003) shows a similar tendency.

Poor risk perception, as well as impaired capacity to deploy appropriate judgment and reasoning while driving, have also been found to play a role in risky behaviors and negative driving outcomes, as shown by McKnight and McKnight (2000) and Ryb et al. (2006). Deficits in these higher order cognitive factors features of executive functioning are thought to underlie risky driving behaviors. Risky driving behaviors such as speeding, tailgating, driving under the influence of alcohol and not using seatbelts while driving, etc., are found to predict MVCs and driving citations (Blows et al., 2005, McKnight and McKnight, 2000). The current study aims to examine self-reports on driving of male and female ADHD and non-ADHD (N-ADHD) drivers.

The Task-Capability Interface (TCI) model and associated hypothesis of task difficulty homeostasis (Fuller, 2000) suggests that under certain conditions, drivers’ behavior is determined by the maintenance of safety margins, such as the distance of the driver from a hazard. According to TCI (Fuller, 2000) loss of control by the driver (and a possible collision occurrence) may arise when the demands of the driving task exceed the available capability of the driver.

One of the ways to study driving quality is by employing the Manchester Driving Behavior Questionnaire (DBQ), which was developed for measuring aberrant driver behavior by using a self-report method (Reason et al., 1990). Reason et al. (1990) identified three factors within the DBQ: violations, errors and lapses. Violations are defined as deliberate departures from behaviors believed to represent safe driving practices (e.g., disregarding the speed limit), while Errors are defined as failures of observation that may be hazardous to others (e.g., failing to check one's rear-view mirror before pulling out or changing lanes). Errors also include planned actions that fail to accomplish their intended outcomes (e.g., braking too quickly on a slippery road, or turning the steering wheel in the wrong direction in a skidding vehicle). Further, Lapses are defined as absent-minded behaviors which usually do not pose any threat to road users (e.g., attempting to drive away from traffic lights in third gear).

The three above-mentioned basic components of the DBQ (violations, errors and lapses) were also found by other studies as reflecting aberrant driving (e.g., Parker et al., 1995). Lawton et al. (1997) differentiated between aggressive violations (e.g., sounding your horn to indicate your annoyance) directed at individual road users and ordinary (highway-code) violations. Notably, violations have usually been associated with crash involvement, and among elderly drivers, high error and lapse scores have been reported to predict accident involvement (Parker et al., 2000).

Reason et al. (1990) suggested that errors and violations are mediated by different psychological mechanisms. Violations require explanation in terms of social and motivational factors (i.e., disregarding traffic rules or disregarding the speed limit, etc.) whereas errors (slips, lapses, and mistakes, i.e., hitting something while reversing or switching on the headlights when meaning to switch on the wipers, etc.) may be accounted for by reference to the information-processing characteristics of the individual. Jerome et al. (2006) found that slow processing and distractibility, and problems with visual memory are also associated with negative driving outcomes.

Attention Deficit Hyperactivity Disorder (ADHD) is a common psychiatric disorder with its onset in childhood, and is characterized by symptoms of inattention, impulsiveness and hyperactivity (American Psychiatric Association, 1994). It affects 8–10% of children (American Academy of Pediatrics AAP, 2000) and 4–5% of adults (Briggs-Gowan et al., 2000). ADHD is relatively persistent, with clinically important symptoms continuing into adolescence (Barkley et al., 1990) and early adulthood (Barkley et al., 2002a, Barkley et al., 2002b) in up to 80% and 66% of diagnosed cases, respectively. ADHD is associated with impairments and adverse outcomes over one's life span, having a substantial impact on a variety of domains of adaptive functioning, including family life, social relationships, community functioning, and educational success (Barkley, 2005). This disorder also encompasses other factors, e.g., demographic, cognitive, and personality which are also related to driving risks and unintentional injury on the road (Jerome et al., 2006).

A meta-analysis of the literature about ADHD and driving risk generally indicates that groups with ADHD are at higher risk for negative driving outcomes and therefore at risk of being involved in MVC (Jerome et al., 2006). The main methods of studying the driving behavior of these subjects were observations, using simulators and self-reports. Observational studies indicated that the ADHD group received more driving citations than control groups, for various violations including speeding and other traffic violations, license suspensions and driving without a license (e.g., Barkley et al., 2002a, Barkley et al., 2002b, Fried et al., 2006). Studies which employed a simulator to assess driving performance also showed that the ADHD group experienced significantly more scrapes, collisions, steering variability and poorer steering control (e.g., Barkley et al., 1996). These findings and others’ (e.g., Fischer et al., 2007) showed a moderate correlation between simulator performance and other parameters.

Some other studies of ADHD and driving risk employed the DBQ (Fried et al., 2006, Reimer et al., 2005, Woodward et al., 2000). The ADHD group showed significantly more lapses, errors and violations than the control group, and more risky driving behaviors were consistently found in ADHD groups compared to N-ADHD groups. Previous studies using the DBQ show a high correlation between self-reported driving behavior and actual driving (e.g., Walton, 1999). Therefore, the use of a DBQ-based method might be relevant to measure ADHD and N-ADHD drivers’ self-report driving habits.

The DBQ was employed in the above studies by asking the participants to fill in the questionnaire once in order to describe their general driving behaviors. A single round of answering on a questionnaire should represent the subject's evaluation of his usual manner of driving, but naturally, it might contain a bias due to his experience, mainly his driving experience, on that very same day. Therefore, this method of using the one-time answering of the questionnaire might raise doubts about the reliability and stability of the driving behavior represented by that single answering. Fischer et al. (2007) report that participants dramatically under-reported the severity of their ADHD symptoms at adult outcome relative to parental reports. Furthermore, they found that the degree of agreement between self-rated safe driving behavior and ratings provided by others was also modest (0.28) and below that found between these same ratings in clinic-referred adults.

In order to overcome the above difficulty, in our present study, the collection of self-reported driving behaviors from the participants was carried out more than once. The participants were asked to fill out a checklist of driving behaviors referring either to violations or to faults. This method was inspired by the DBQ after necessary adjustments were made to fit the changes due to the length of the study, and participants filled out these checklists on a daily basis for 30 consecutive days. The present study aims to measure drivers’ differences in unsafe driving behaviors of male and female, having and not having ADHD, by 30 days of self-reporting.

Leigh (2000) asserts that daily reporting generally yield higher levels of actual behavior, especially of commonplace behaviors that might easily be forgotten as well as more accurate information on mundane behaviors. When participants record events on the day that they occur, daily reporting can reduce forgetfulness.

In line with Schwarz (1990), we used, in the current study, a method leaning on the daily reporting of specific events. We found this more suitable than asking the participants to estimate their “usual” or “average” behavior, which may not correspond to actual behavior for any particular interval (Whitty and Jones, 1992).

In line with the above-mentioned characteristics of inattentive drivers, we assumed that ADHD drivers would report less safe behaviors than N-ADHD. We also assumed, in accordance with the well-based evidence about gender differences in safe driving (Ozkan and Lajunen, 2006, Yagil, 1998) that males would generally report more errors and violations than females.