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INDIVIDUAL DIFFERENCES AND THE "HIGH-RISK" COMMERCIAL DRIVER SUMMARY This synthesis focuses on the "high-risk" commercial driver. Most truck and bus drivers are both conscientious and safe, but the findings of this research project support the notion, and widespread industry belief, that a relatively small percentage of commer- cial drivers are associated with a significant and inordinate percentage of the overall motor carrier crash risk. This research project has attempted to document this phenomenon, explore related factors, and identify ways that the high-risk driver can be targeted by various safety management practices and other safety interventions. Expert industry opinion has been accessed through survey questionnaires on the topic. The research literature on the topic has been reviewed, with emphasis on the personal factors associated with risk and carrier management approaches to reducing the problem. This synthesis focuses on commercial (i.e., large truck and bus) drivers, but also presents the results from a literature review on transportation operators in other modes such as air, rail, and maritime. Commercial motor vehicle (CMV) fleet safety managers are the principal audience for this synthesis, although this synthesis is a presentation of findings, not a "how to" guide to practice. In addition, the synthesis should be useful to government, industry, and academic personnel involved in formulating and conducting studies to gain knowl- edge (i.e., research) and to create tools (development) relating to this safety topic. As noted, one basis for the research project was survey data collected from fleet safety managers and "other experts" in motor carrier safety. Safety manager surveys were dis- tributed primarily through a random sample mailing to carriers listed in the American Trucking Associations fleet directory. In addition, survey forms were sent to people who responded to a CTBSSP Synthesis 1 survey (also on carrier safety management), and, in order to obtain motor coach segment respondents, some survey forms were distributed to members of the American Bus Association Safety Council. The safety manager sur- vey return rate was about 15%, so the sample cannot be described as representing the CMV industry in general. Instead, it represents 178 interested managers from a variety of CMV operations. A second survey sample consisted of 67 other experts. These are individuals pro- fessionally involved in CMV safety who are not fleet safety managers. This group

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2 includes former drivers and fleet managers, government regulatory and enforcement personnel, industry trade association representatives, and researchers. Of course, these are overlapping categories, and most other experts indicated several different motor carrier safety-related professional experience areas. The safety manager and other expert survey forms were parallel in their questions and content, but there was one key difference. Regarding management practices, safety managers were asked if they currently used the method and then, if "yes," they were asked to rate its effectiveness. This yielded data on the percentage of carriers actually using various methods and opinions of effectiveness of respondents actually using the methods. For the other experts, parallel items only elicited evaluation ratings because there were no questions regarding use. Perhaps the most fundamental question about high-risk commercial drivers is whether the problem is genuine and significant or the result of chance or other factors uncontrol- lable by commercial drivers and their fleets. Survey findings strongly support the notion that the problem is real and significant and that individual differences in safety among drivers are enduring. Empirical data cited from a number of studies corroborate this view, but do not sufficiently describe or explain the problem. In one cited study, for example, large individual differences were seen in the rate of driver involvement in traf- fic "near-miss" incidents, and 12% of the drivers in the study were associated with 38% of the incidents. However, the study did not track drivers for a long period of time to determine the degree of consistency of differential risk or the personal traits that could produce enduring individual differences in risk. Many factors affect commercial driver crash involvement. The focus of this syn- thesis is on enduring personal risk factors. Nevertheless, at any given time, com- mercial driver crash risk is affected by personal risk factors (e.g., hours of sleep the previous night), vehicle risk factors (e.g., brake adjustment), environmental factors (e.g., weather and roadway features), and, perhaps most important, risks created by other drivers and traffic. "Accident proneness" was originally conceptualized nearly 100 years ago. Early concepts of it considered it an innate, unitary trait, a view that is no longer widely held. However, it certainly appears that individual differences in per- sonality and performance predispose some people to increased crash risk. Driver errors can be violations of rules, mistakes of judgment, inattention errors, or inexperience errors. Common driver errors resulting in crashes include recognition errors (failure to perceive a crash threat) and decision errors (risky driving behavior such as tail- gating), or poor decision-making in dynamic traffic situations (such as trying to cross a stream of traffic). There are many personal dimensions that may be correlated with individual crash risk. In the research project survey, respondents were asked to rate the strength of asso- ciation of 16 such factors with crash risk. Personality traits such as aggressiveness, impulsivity, and inattentiveness were rated by both respondent groups as having the highest associations with risk. This synthesis reviews literature relating to the following factors related to com- mercial driver risk. A number of factors potentially correlate with risk and may be the basis for safety interventions to reduce risk. Factors discussed include the following: Driver age and gender Driving history Commercial driving experience Longevity with company Crashes, violations, and incidents Defensive driving

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3 Non-driving criminal history Medical conditions and health Sleep apnea Narcolepsy Diabetes Other medical conditions Alcohol and drug abuse Driver fatigue Personality Impulsivity and risk-taking Social maladjustment and aggressive/angry personalities Introversion-extroversion Locus of control Extreme ("dichotomous") thinking Sensory-motor performance Other risk factors Stress Recent involvement in other crashes Safety belt use Risks identified in other transportation modes Maritime operations Rail Aviation Fleet safety management approaches to preventing high-risk-driverrelated crashes revolve around the basic management functions of selection and hiring, per- formance evaluation, and driver safety management practices. The clearest advice to safety managers is, "Don't hire a problem." Methods for improving driver selection and job aids for safety managers are provided in Appendix F. Once drivers are hired, there are various ways to monitor their driving behaviors and modify their behavior in ways that reduce risk. Performance evaluation and feedback (perhaps enhanced by on-board safety monitoring of driver behavior), training and coun- seling, performance incentives, behavior-based safety, and driver self-management are among the methods described. Of course, termination may be the ultimate solution when drivers are unmanageable from the safety perspective. Recommended research and development (R&D) to address the problem of high-risk drivers includes the following: Verification of the reliability of research findings indicating differential driver risk. Determination of how enduring these differences are across time. To the extent that they are enduring, they constitute personal traits. To the extent that they change, they likely reflect short-term personal conditions (states) or purely situational factors. The conducting of case control or other driver studies that profile individual driver differences within a group of drivers and relate these differences to safety outcomes (e.g., crashes). Creation and field testing of various types of driver selection instruments. Investigation of individual fatigue susceptibility. Research should verify that dif- ferences in fatigue susceptibility are long-term personal traits and identify ways to assess the level of fatigue susceptibility. Highly susceptible individuals should not

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4 be hired as commercial drivers or should receive special attention, including med- ical screening for sleep disorders and counseling about sleep hygiene habits. Documentation of the best driver management practices for use by carrier safety managers and dissemination of this information throughout the industry. Industry pilot testing of behavioral safety management techniques, perhaps en- hanced by the use of on-board safety monitoring of driver safety performance and behaviors. This should include determination of the effectiveness of various management interventions including both positive rewards and negative discipline (punishment).