Approximately 4,000 fatalities result from crashes involving trucks and buses in the United States each year. Although estimates are wide-ranging, 10 to 20 percent of these crashes may have involved fatigued drivers. The stresses associated with work as a commercial motor vehicle (CMV) driver (e.g., irregular schedules, economic pressures) and the lifestyle many of these drivers lead put them at substantial risk for insufficient sleep and the development of shortand long-term health problems. Sleep disorders such as obstructive sleep apnea (OSA), for example, appear to be common among many CMV drivers. OSA is a major contributor to driver fatigue, which in turn raises a driver’s risk for involvement in crashes. Moreover, it has become increasingly clear that drivers who regularly obtain insufficient sleep, whether as a result of irregular work patterns, sleep disorders, or other reasons, are likely at increased risk for a number of serious long-term health problems. To address this problem, the Federal Motor Carrier Safety Administration (FMCSA) asked the National Academies of Sciences, Engineering, and Medicine to convene the Panel on Research Methodologies and Statistical Approaches to Understanding Driver Fatigue Factors in Motor Carrier Safety and Driver Health. The panel was charged with providing advice on additional data collection and analytic techniques with the potential to support a more comprehensive understanding of the links between operator fatigue and highway safety and between fatigue and long-term health such as cardiovascular diseases. Specifically, the charge to the panel was to “assess the state of knowledge about the relationship of such factors as hours of driving, hours on duty, and periods of rest to the fatigue experienced by truck and bus drivers while driving and the implications for the safe operation of their vehicles. The panel will also assess the relationship of these factors to drivers’ health over the longer term. It will identify improvements in data and research methods that can lead to better understanding in both areas.” FMCSA’s mission is to “reduce crashes, injuries, and fatalities involving large trucks and buses.” The agency works toward this goal in at least three ways. First, a major policy lever at FMCSA’s disposal is that it issues and administers hours-of-service (HOS) regulations for truck and bus drivers that specify the maximum number of hours they can work in a day and in a workweek. The hope is that if they drive limited hours, drivers will have enough time to obtain adequate sleep between work shifts, and therefore will be more alert and less fatigued while driving. As a result, it is believed, the risk of crashes will be more manageable. Second, FMCSA is responsible for the medical certification of CMV drivers through the National Registry of Certified Medical Examiners (NRCME). Members of the NRCME examine CMV operators at least every 2 years to determine whether they meet FMCSA’s medical standards. Third, Transport Canada, FMCSA, trucking industry trade associations, and other agencies developed the North American Fatigue Management Program (NAFMP), an Internetbased online educational program that informs drivers, their employers, and anyone involved in commercial carrier operations about the causes of driver fatigue, the increased risk of crashes due to fatigue, and the long-term health consequences of CMV driving (such as regular sleep insufficiency), and, most important, suggests countermeasures that can be used to manage driver fatigue. The specifics of these three FMCSA programs are based on the current scientific understanding of operator fatigue, its causes, and its consequences. A considerable amount of research has been conducted to clarify the relationship among hours of service, driver fatigue, and crash risk, as well as the relationship between fatigue and long-term health and wellness. As yet, knowledge of these relationships is not comprehensive, and the relationships themselves may be changing. However, the quality and quantity of the information available on these relationships is constantly increasing. In particular, new in-vehicle technologies and roadway improvements are regularly being applied to promote safety, and several of these innovations allow for the capture of important data that could be used to better inform policy and/or improve driving procedures. Additionally, recent advances in statistical methods could be applied to make better practical and research use of data that either are currently collected or could be collected if targeted for research purposes. HOS rules can only limit hours spent driving and working; they cannot mandate rest, so they inherently cannot ensure, by themselves, that drivers will be well rested and alert. Therefore, it is not straightforward to determine how additional modifications of the current HOS rules would result in more or less fatigue in CMV drivers that might, respectively, raise or lower crash risk. In addition, driver fatigue obviously is not the only cause of highway crashes. Crash risk factors can be grouped into at least four main types: driver characteristics; truck or bus characteristics; factors stemming from employment circumstances, especially with respect to scheduling and work assignments; and the physical environments encountered while driving. The variety of factors from which a crash can result, acting either solely or in combination, make it challenging to develop an understanding of the nature of an individual risk factor—in the present case fatigue—since there are so many confounders that are difficult to control or otherwise account for in analyses. Therefore, the study designs and analytic tools used in such research are critically important. A further complication is that fatigue is very difficult to define and therefore to measure objectively. If fatigue is loosely defined as the inability to sustain performance over time, under such a value definition it is not directly measurable. Therefore, it is somewhat difficult to assess fatigue, and thus to regulate how to avoid driving while fatigued. As a result, researchers and policy makers must instead assess how hours of service affects various components of fatigue, many of which are measurable. One of the most important, objectively measureable components of fatigue is “drowsiness” or lack of alertness. To add to this complexity, the commercial truck and bus industries are highly heterogeneous, with a great variety of types of employment, methods for compensation, and so on. As a result of their specific type of employment, many CMV drivers are affected in different ways, and sometimes not at all, by changes in HOS regulations. Therefore, stratifying, or otherwise accounting for, the type of employment in some way is important when carrying out research in this area. Adding still further to this complexity is the difficulty of assessing some of the primary inputs—sleep duration, hours of service, level of driver alertness—and the primary output—rates of crashes due to fatigue. Obtaining satisfactory measures of the amount or quality of sleep obtained by a truck or bus driver during the previous night or nights is difficult because selfreports often are not highly reliable and because attempts to directly capture measures of drivers’ sleep are invasive in nature. Also, it has been shown that paper logs recording hours of service for CMV drivers are often inaccurate. In crash reporting databases, moreover, the primary judge of the factors involved in a highway crash are police officers who must, make such assessments after the fact, with little information to go on. Partly as a result of these difficulties, the available crash reporting databases often provide a paucity of information on sleep deficiency in CMV drivers, their adherence to HOS rules, and their crash frequency as a result of fatigued driving. Therefore, research on the linkage among hours of service, fatigue, and accident frequency is hampered by imperfect knowledge of the three most central variables. (Author/publisher)
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