4. Distracted and Fatigued Driving
Distracted and fatigued driving are common, though both are difficult to define, observe, and measure. Both distracted and fatigued driving result in large part from lifestyle patterns and choices: they are societal issues rather than just driving and transportation system issues. For these reasons, few behavioral highway safety countermeasures have been shown to reduce distracted or fatigued driving. Rumble strips and other environmental measures have proven quite successful in reducing crashes by distracted or fatigued drivers. A variety of vehicular measures may either increase or reduce distractions and fatigue.
Recent distracted driving attention and research has concentrated on cell phones, but other distractions are more common and appear to contribute more to crashes. Attention and research on fatigue has concentrated on commercial truck drivers, but the problem is far more widespread.
Problem size and characteristics: distracted driving. Distractions take a driver's attention away from driving. A distraction can be produced by something a driver sees or hears, some physical task not directly involved in driving (such as eating or operating the car radio), or mental activities (such as conversations with passengers or on a cell phone) (NHCRP, 2005, Section III).
NHTSA surveyed 4,010 drivers in spring 2002 and asked about a variety of potentially distracting behaviors (Royal, 2003, p. 1). The vast majority reported these behaviors on some trips, often on many or most trips. The most common were:
About one-quarter of the drivers reported that they had been involved in a crash in the previous five years in which some vehicle was damaged. About 14 percent attributed their crash to distracted driving (Royal, 2003, p. 28). Similarly, about 10 percent of the drivers in a sample of crashes involving at least one towed vehicle in 1995-1999 were classified by NHTSA investigators as having been distracted (Stutts et al., 2001, p. 3). The true role of distraction in crashes probably is higher because pre-crash distractions often leave no evidence for law enforcement officers or crash investigators to observe. A recent study that monitored 100 drivers for a year, using specialized instrumentation, reported that nearly 80 percent of the 72 recorded crashes and 65 percent of the 761 near-crashes involved driver inattention just prior to the incident (VTTI, 2005).
In crashes where distractions were reported, the most common distractions were similar in NHTSA's driver survey and crash investigations.
None of the leading distractions is easily addressed. Cell phone use falls well down this list.
Problem size and characteristics: fatigued or drowsy driving. Three recent national telephone surveys, two in the United States and one in Canada , provide consistent estimates of the prevalence and key characteristics of drowsy driving. Of the 1,456 adult drivers surveyed by the National Sleep Foundation (NSF) in fall 2004, 60 percent reported that they had driven while feeling drowsy at least once within the past year. Further, 37 percent said they had "nodded off or fallen asleep" while driving a vehicle at least once in their life (NSF, 2005b, p. 42). Canadian responses from 1,209 drivers were similar: 57 percent had driven while tired and 20 percent had dozed off (Beirness et al, 2005). In NHTSA's survey, 11 percent reported that they had nodded off while driving during the past year (Royal, 2003, p. 42). Of those who nodded off, 66 percent said they had six or fewer hours of sleep the previous night (Royal, 2004, p. 46). The NHTSA and Canadian surveys found that drivers under age 30 and male drivers were more likely than older drivers and female drivers to have dozed off at the wheel, as did a previous NSF survey (Beirness et al., 2005, p. iii; NSF, 2002a, p. 25; Royal, 2003, p. 42) (the 2005 NSF survey did not examine driver age and gender).
The NHTSA and Canadian surveys provide additional useful information about drowsy driving. Drivers nodded off throughout the day and night. In each survey, over one-quarter of the most recent incidents occurred in the afternoon (noon to 6 p.m.) and over one-quarter between midnight and 6 a.m. In both surveys, nearly half of the drivers who nodded off had been driving for an hour or less (Royal, 2003, p. 44; Beirness et al, 2005, p. 12). About 0.7 percent of all drivers reported that they had been in a crash in the past five years that they attributed to their drowsy driving. That's about one-fifth as many as reported a crash that they attributed to distracted driving (Royal, 2003, p. 50).
The obvious way to reduce distracted or drowsy driving crashes is to convince or require drivers to get enough sleep and to pay attention to their driving. These are very difficult goals. Drowsy driving may result from lifestyles that include insufficient or irregular sleep (shift workers, for instance) or from medical problems - issues beyond a driver's immediate control. Many drivers consider some distractions, such as eating or drinking, listening to the radio, or talking on a cell phone, to be important and common activities and are unlikely to give them up.
Behavioral strategies to reduce distracted or drowsy driving attempt to remove some of the underlying causes and to promote awareness of the risks. The standard behavioral countermeasures of laws, enforcement, and sanctions, which are used successfully for alcohol impairment, safety belt use, aggressive driving, and speeding, are unlikely to be effective for distracted or drowsy drivers. One exception is for young drivers: some graduated driver licensing provisions help reduce distractions by limiting the number of passengers or restricting cell phone use.
Distracted or fatigued driving that is related to a driver's job may be reduced through employer policies and programs. Drowsy driving caused by medical conditions such as sleep apnea or by drugs or medications may be addressed through policies, communications, and outreach. Similarly, communications and outreach may be useful in raising awareness of specific distraction or fatigue issues among certain high-risk populations. However, none of these strategies has been evaluated.
This chapter discusses these behavioral strategies. It does not include the environmental, vehicular, and regulatory countermeasures mentioned below because SHSOs do not have authority or responsibility in these areas.
Environmental strategies can address both distracted and drowsy driving. Rumble strips, both on the shoulder and the centerline, have demonstrated their effectiveness in preventing crashes caused by inattention or fatigue. Other roadway improvements, such as wide and visible edge lines, more easily visible road signs, and better lighting at night, can help drivers who are not fully alert. See NCHRP (under review) for a thorough discussion and for references to other NCHRP guides. In the future, ITS (Intelligent Transportation System) technology also may help drivers remain alert or warn them of risky situations (ITS, 2003).
Vehicular strategies also affect driver distraction and fatigue. In-car television, vehicle location and route-finding systems, and other new technologies in vehicles may create more potential distractions. On the other hand, in-vehicle technology in the future may be able to detect driver distraction or fatigue, by monitoring driver performance, and then alert drivers. In-vehicle technology also may be able to warn drivers of risky situations. Automobile manufacturers and NHTSA are vigorously investigating many possibilities (NHTSA, 2000; ITS, 2003).
Driver fatigue is a critical issue for commercial drivers. The Federal Motor Carrier Safety Administrtion attempts to control commercial driver fatigue through Hours of Service regulations, driver logs and inspections (see for example FMCSA, 2005a). FMCSA has an extensive driver fatigue research program focused on commercial drivers (FMCSA, 2005b). As with the environmental and vehiclular countermeasures mentioned above, commercial driver countermeasures are not discussed in this guide because they do not fall under SHSO jurisdiction.
Countermeasures to reduce distracted and fatigued driving are listed below and discussed individually in this chapter. The table is intended to give a rough estimate of each countermeasure's effectiveness, use, cost, and time required for implementation. The terms used are described below. Effectiveness, cost, and time to implement can vary substantially from State to State and community to community. Costs for many countermeasures are difficult to measure, so the summary terms are very approximate. See each countermeasure discussion for more information.
1. Laws and enforcement
*Included under reckless driving; use of explicit fatigue and distraction laws is low
2. Communications and outreach
3. Other countermeasures
Effectiveness is measured by reductions in crashes or injuries unless noted otherwise.
See individual countermeasure descriptions for information on effectiveness size and how effectiveness is measured.
Cost to implement:
Time to implement:
These estimates do not include the time required to enact legislation or establish policies.