Drowsy driving is a significant threat to traffic safety and public health. Although underreported in government statistics, previous research by the AAA Foundation for Traffic Safety has estimated that 6% to 11% of all police-reported motor-vehicle crashes and 16% to 21% of fatal crashes likely involve drowsy driving. Thus, there is a need to identify effective strategies for reducing the prevalence of drowsy driving and the crashes, injuries, and deaths that result from it.
The purpose of this research was to describe the current state of knowledge regarding the effectiveness of countermeasures intended to combat drowsy driving or mitigate its consequences. This was accomplished through a review of recent literature as well as discussions with experts.
The results of this study highlight the complexity of reducing drowsy driving and suggest the following conclusions:
- There is evidence that obtaining sufficient sleep, napping, and consuming caffeine reduce the risk of drowsy driving. Numerous other behavioral countermeasures were identified, but there is insufficient or mixed evidence regarding their effectiveness.
- Advanced driver assistance systems are effective in reducing rates of crashes in general, though more research is needed on their effectiveness in reducing drowsy driving crashes specifically. Other technology-based countermeasures intended to reduce drowsy driving require additional research.
- Infrastructure-based countermeasures such as rumble strips are effective in preventing crashes in general, though more research is needed on their effectiveness in reducing drowsy driving crashes specifically.
- Education is important for at-risk populations, but it is insufficient to reduce drowsy driving by itself and must be combined with other countermeasures.
- Sleep disorders contribute to drowsy driving. Treatments are available for sleep disorders, though more research is needed to determine their effects on drowsy driving.
- Policy countermeasures including drowsy driving laws as well as workplace policies require further research to examine their effectiveness in preventing drowsy driving.
The literature review and discussions with experts also identified three key cross-cutting themes for future research and action:
- Many drowsy driving countermeasures have been examined in laboratory settings and appear promising. However, research in naturalistic settings or with real-world data is needed to evaluate their effectiveness and to understand how they may interact with various contextual factors.
- Reliable and informative data are critical to understanding the prevalence of drowsy driving, educating the public, and evaluating countermeasures. However, driver drowsiness is difficult to measure, especially after a crash. There is a need for improved data on drowsy driving.
- Disclosing drowsiness or medical conditions that cause drowsiness is often stigmatized in the workplace. This stigma is a barrier to addressing drowsy driving. Efforts are needed to combat drowsiness-related stigma in the workplace.
The research team conducted a literature review to identify peer-reviewed research on drowsy driving countermeasures published in English between 2010 and 2020, as well as an environmental scan to identify grey literature (e.g., reports by government agencies, industry groups, and others) focused on drowsy driving countermeasures. A panel of experts was convened in April 2021 for the following purposes:
- To review the countermeasures identified through the literature review and environmental scan
- To gather new information on countermeasures not yet evaluated or published
- To discuss the feasibility of implementing the countermeasures
- To discuss needs for additional research
Several additional experts were interviewed individually as well. A total of 152 articles or reports were identified, and they included information about 207 countermeasure evaluations.