EXECUTIVE SUMMARY Drowsy driving is a serious problem that leads to thousands of automobile crashes each year. This report, sponsored by the National Center on Sleep Disorders Research (NCSDR) of the Na-tional Heart, Lung, and Blood Institute of the National Institutes of Health, and the National Highway Traffic Safety Administration (NHTSA), is designed to provide direction to an NCSDR/NHTSA educational campaign to combat drowsy driving. The report presents the results of a literature review and opinions of the Expert Panel on Driver Fatigue and Sleepiness regarding key issues involved in the problem. BIOLOGY OF HUMAN SLEEP AND SLEEPINESS Sleep is a neurobiologic need with predictable patterns of sleepiness and wakefulness. Sleepiness results from the sleep component of the circadian cycle of sleep and wakefulness, restriction of sleep, and/or interruption or fragmentation of sleep. The loss of one night's sleep can lead to extreme short-term sleepiness, while habitually restricting sleep by 1 or 2 hours a night can lead to chronic sleepiness. Sleeping is the most effective way to reduce sleepiness. Sleepiness causes auto crashes because it impairs performance and can ultimately lead to the inability to resist falling asleep at the wheel. Critical aspects of driving impairment associated with sleepiness are reaction time, vigilance, attention, and information processing. CRASH CHARACTERISTICS Subjective and objective tools are available to approximate or detect sleepiness. However, unlike the situation with alcohol-related crashes, no blood, breath, or other measurable test is currently available to quantify levels of sleepiness at the crash site. Although current understanding largely comes from inferential evidence, a typical crash related to sleepiness has the following characteristics: The problem occurs during late night/ early morning or midafternoon. The crash is likely to be serious. A single vehicle leaves the roadway. The crash occurs on a high-speed road. The driver does not attempt to avoid a crash. The driver is alone in the vehicle. RISKS FOR DROWSY-DRIVING CRASHES Although evidence is limited or inferential, chronic predisposing factors and acute situational factors recognized as increasing the risk of drowsy driving and related crashes include: Sleep loss. Driving patterns, including driving between midnight and 6 a.m.; driving a substantial number of miles each year and/or a substantial number of hours each day; driving in the midafternoon hours (especially for older persons); and driving for longer times without taking a break. Use of sedating medications, especially prescribed anxiolytic hypnotics, tricyclic antidepressants, and some antihistamines Untreated or unrecognized sleep disorders, especially sleep apnea syndrome (SAS) and narcolepsy. Consumption of alcohol, which interacts with and adds to drowsiness. These factors have cumulative effects; a combination of them substantially increases crash risk. POPULATION GROUPS AT HIGHEST RISK Although no driver is immune, the following three population groups are at highest risk, based on evidence from crash reports and self-reports of sleep behavior and driving performance. Young people (ages 16 to 29), especially males. Shift workers whose sleep is disrupted by working at night or working long or irregular hours. People with untreated sleep apnea syndrome (SAS) and narcolepsy. COUNTERMEASURES To prevent drowsy driving and its consequences, Americans need information on approaches that may reduce their risks. The public needs to be informed of the benefits of specific behaviors that help avoid becoming drowsy while driving. Helpful behaviors include (1) planning to get sufficient sleep, (2) not drinking even small amounts of alcohol when sleepy, and (3) limiting driving between midnight and 6 a.m. As soon as a driver becomes sleepy, the key behavioral step is to stop driving-for example, letting a passenger drive or stopping to sleep before continuing a trip. Two remedial actions can make a short-term difference in driving alertness: taking a short nap (about 15 to 20 minutes) and consuming caffeine equivalent to two cups of coffee. The effectiveness of any other steps to improve alertness when sleepy, such as opening a window or listening to the radio, has not been demonstrated. A more informed medical community could help reduce drowsy driving by talking to patients about the need for adequate sleep, an important behavior for good health as well as drowsy-driving prevention. The detection and management of illnesses that can cause sleepiness, such as SAS and narcolepsy, are other health care-related countermeasures. Information could be provided to the public and policymakers about the purpose and meaning of shoulder rumble strips, which alarm or awaken sleepy drivers whose vehicles are going off the road. These rumble strips placed on high-speed, controlled-access, rural roads reduce drive-off-the-road crashes by 30 to 50%. However, rumble strips are not a solution for sleepy drivers, who must view any wake-up alert as an indication of impairment-a signal to stop driving and get adequate sleep before driving again. Employers, unions, and shift work employees need to be informed about effective measures they can take to reduce sleepiness resulting from shift work schedules. Countermeasures include following effective strategies for scheduling shift changes and, when shift work precludes normal nighttime sleep, planning a time and an environment to obtain sufficient restorative sleep. FOCUSING AN EDUCATIONAL CAMPAIGN: PANEL RECOMMENDATIONS To assist the educational campaign in developing its educational initiatives, the panel recommended the following three priority areas: Educate young males (ages 16 to 24) about drowsy driving and how to reduce lifestyle- related risks. Promote shoulder rumble strips as an effective countermeasure for drowsy driving; in this context, raise public and policymaker awareness about drowsy-driving risks and how to reduce them. Educate shift workers about the risks of drowsy driving and how to reduce them. The panel also identified complementary messages for the campaigns and called for the active involvement of other organizations in an effort to promote sufficient sleep-as a public health benefit as well as a means to reduce the risk of fall-asleep crashes. I. INTRODUCTION In the 1996 appropriations bill for the U.S. Department of Transportation, the Senate Appropriations Committee report noted that "NHTSA data indicate that in recent years there have been about 56,000 crashes annually in which driver drowsiness/fatigue was cited by police. Annual averages of roughly 40,000 nonfatal injuries and 1,550 fatalities result from these crashes. It is widely recognized that these statistics underreport the extent of these types of crashes. These statistics also do not deal with crashes caused by driver inattention, which is believed to be a larger problem." In response, Congress allocated funds for a public education campaign on drowsy driving among noncommercial drivers, to be sponsored by the National Highway Traffic Safety Administration (NHTSA) and the National Center on Sleep Disorders Research (NCSDR) of the National Heart, Lung, and Blood Institute, the National Institutes of Health. This focus complements Federal Highway Administration efforts to address the problem among commercial vehicle drivers (Federal Register, 1996). To provide evidence-based direction to this campaign, the Expert Panel on Driver Fatigue and Sleepiness reviewed the research conducted to date on drowsy-driving crashes. The resulting report outlines the following: The biology of human sleep and sleepiness, which physiologically underlies crash risk. Common characteristics of crashes related to drowsy driving and sleepiness. Risks for crashes attributed to drowsy driving. Population groups at highest risk. Effective countermeasures used to prevent drowsy driving and related crashes. In addition to summarizing what is known-and what remains unknown-from sleep and highway safety research, the report also presents the panel's recommendations for the highest priority target audiences and educational message points for the NCSDR/NHTSA campaign. METHODS AND KNOWLEDGE BASE OF THIS REPORT The panel conducted a wide-ranging search for information on sleep, circadian rhythms, sleepiness, drowsiness, sleep physiology, and sleep disorders, as well as on the association of these topics with driving risk and crash prevention. The panel conducted literature searches of online databases in traffic safety, medicine, and physiology using the keywords listed above and following suggestions for linkage to related topics (e.g., technology, alerting devices, industrial accidents, and shift work). In addition, the panel requested or was forwarded formal and informal reviews and monographs by Federal, State, and nongovernmental agencies. Although there was no formal ranking of the scientific rigor of all this material, original papers, reviews, monographs, and reports selected for citation reflect the higher levels of evidence available on the topic and literature upon which the major concepts or opinions of the panel report are based. The references provided do not, however, reflect all resources available or reviewed by the panel; when possible, more recent material or reviews are preferentially cited. The principal types of primary data the panel used fall into the following categories: Studies of crash data that identify the characteristics of crashes in which the driver was reported by police to have fallen asleep and the characteristics of the sleepy driver. Self-reports from drivers involved in crashes (with data collected either at the crash scene or retrospectively) that gather information on driver behavior preceding the crash or relevant work, sleep, and other lifestyle habits. Population surveys that relate driver factors to fall-asleep or drowsy-driving crashes or to risky behavior associated with crashes. Laboratory studies using a driver simulator or other fundamental tests that relate the effects on performance of sleepiness, sleep loss, and the combined effects of sleep loss and alcohol consumption. Laboratory studies using a driver simulator or performance tests that examine the performance of persons with sleep disorders compared with a control group. Retrospective studies that compare crash histories of drivers with sleep disorders with other drivers. Laboratory and epidemiological studies of drowsy-driving countermeasures. The literature reviewed had variations in design, method, rigor, populations included, methodological detail, outcome measures, and other variables, all of which precluded a strict comparison. In addition, the number of studies is relatively small, and some of the studies do not represent large numbers of crashes or feature crash numbers or frequency as an outcome measure. RESEARCH NEEDS The panel identified three major categories in which more evidence is needed: Quantification of the problem. To allow accurate estimates of the true prevalence of drowsy-driving crashes, it will be important to develop a standard manner by which law enforce- ment officers can assess and report crashes resulting from drowsy driving. Currently, States use different definitions and have varying reporting requirements, which hinder quantification. However, this is not just a reporting problem; a method for objectively assessing sleepiness at the crash site also would enable better quantification. Risks. More information is needed on chronic and acute risks for drowsy-driving crashes. For example, capturing information on drivers' precrash behaviors (e.g., duration of prior wakefulness, recent sleep-wake patterns, the quality and quantity of sleep, work hours, and work patterns [day shift, night shift, rotating shift]) could enhance understanding of the problems. It is important to learn more about at-risk drivers who do not crash and about the impact of drowsiness on driving at all points on the continuum, from low-level drowsiness to falling asleep at the wheel. Countermeasures. Additional information and research are needed on measures that increase or restore driver alertness or reduce crash risk or incidence. In addition, studies should determine whether early recognition, treatment, and management of sleepiness and sleep disorders reduce crash risk or incidence. Educational approaches that are effective for reaching high-risk audiences will need to be developed and tested; ultimately, the impact of such approaches on drowsy-driving knowledge, attitudes, and behaviors will need to be examined.