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Chapter 4

Drowsy driving can be considered another form of distracted driving in that drivers experiencing drowsiness do not apply their full attention to the driving task. Yet, drowsy driving is a problem of its own.

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."

This section provides information on the driving age public's experiences and perceptions regarding drowsy driving. Specifically it covers the following topics:

· Experience with driving while drowsy
· Characteristics of most recent drowsy driving trip
· Measures to prevent falling asleep while driving
· Outcomes of drowsy driving
· Perceived threat of drowsy driving

Experiences With Drowsy Driving

Nodding Off While Driving

Overall, 37% of the driving population says they have nodded off for at least a moment or fallen asleep while driving at some time in their life. Males (49%) are almost twice as likely to report having nodded off while driving than are female drivers (26%).
Not surprisingly, newer drivers (i.e. those under age 21) who have had less time driving overall, are only half as likely to have experienced nodding off while driving (18%) as older drivers. And, just as drivers over age 64 are less likely to undertake behaviors that are potentially distracting, these drivers are also less likely to have nodded off while driving (30%). [Figure 13-A]

Recency of Drowsy Driving

While 37% of drivers have nodded off while driving at some point in their lives, approximately three out of ten (29%) of these drivers report that they last experienced this problem within the past year, with just one in ten (10%) saying this happened to them within the past month. This amounts to about 4% of the driving population or an estimated 7.5 million drivers who have nodded off while driving within the past month. An additional 4% of drivers (11% of those who have ever nodded off at the wheel) report having done so within the past two to six months. [Figure 13-B]

By Gender and Age

About 22% of male drivers who have nodded off at the wheel report having done so within the past month as compared to 19% of their female counterparts.

While drivers under age 21 are only half as likely to have had an experience of falling asleep while driving, slightly more than four of ten (44%) of those report having this experience within the past six months. [Figure 13-D]

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Characteristics of Most Recent Drowsy Driving Trip

In order to better understand the conditions under which drivers experience drowsy driving, drivers who reported having nodded off while driving within the past six months were asked a series of defining characteristics of their most recent experience.

Time of Day

While some hold the perception that drowsy driving occurs mostly late at night or in the early morning hours, just 28% of drivers reporting a recent drowsy driving experience report this experience occurring between the hours of midnight and 6:00 a.m. More than one-third (35%) of drivers who nodded off while driving within the past six months say their last experience occurred between 6:00 a.m. and 5:00 p.m. An additional 17% report they nodded off between 5:00 p.m. and 9:00 p.m. [Figure 14-A]

Average Length of Time Driving

While slightly more than one in five (22%) drivers who recently experienced a drowsy driving episode report having been on the road driving for five or more hours, nearly half (47%) were driving for an hour or less. [Figure 14-B]

On average, these drivers were driving for almost three hours before they nodded off. Males had driven for about an hour longer than females on average (3.2 as compared to 2.2 hours). Drivers age 30 and over became drowsy in a shorter amount of time than younger drivers. [Figure 14-C]

Type of Road Driving

Nearly six in ten (58%) drivers with a recent drowsy driving episode report this occurrence on multi-lane interstate highways, 23% report nodding off while driving on a two-lane road with posted speed limits of 45 MPH or higher, and fewer than one in ten drivers nodded off while driving on non-interstate multi-lane roads (8%) or local city or neighborhood roads (8%). [Figure 14-D] This report of nodding off experience by road type does not match the overall pattern of driving by road type. Just 55% of drivers report frequently driving on multi-lane interstate highways as compared with 83% who frequently drive local city or neighborhood roads. [Figure 2-A]

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Number of Hours Slept the Night Before

While about one in four (24%) drivers experiencing a recent drowsy driving episode reported having just four or fewer hours of sleep the night before, a full one-third (33%) of the drivers had at least seven hours of sleep. An additional 26% report receiving about six hours of sleep the prior night. [Figure 15-A]

While drowsy drivers on average had received six hours of sleep the night before they nodded off while driving, older drivers report having a drowsy driving episode even after longer sleep times. Drowsy drivers under age 30 reported an average of 5.5 hours of sleep the night before they nodded off at the wheel. The average sleep time of drowsy drivers increases with age, with those age 65 or older reporting a drowsy driving episode after an average of 7.7 hours of sleep the prior night. [Figure 15-B]

Use of Alcohol or Medications Prior to Driving

Relatively few drivers who nod off at the wheel report having had consumed alcohol (2%) or allergy or other medications (12%) prior to their trip. Alcohol is reported more of a factor among those in their 20s, of whom 5% report having consumed alcohol prior to their trip. Drivers age 30-45 are least likely to report either alcohol (0%) or medication (6%) as a factor in their drowsy driving. [Figure 15-C]

 

Number of Hours Slept the Night Before
While about one in four (24%) drivers experiencing a recent drowsy driving episode reported having just four or fewer hours of sleep the night before, a full one-third (33%) of the drivers had at least seven hours of sleep. An additional 26% report receiving about six hours of sleep the prior night. [Figure 15-A]
While drowsy drivers on average had received six hours of sleep the night before they nodded off while driving, older drivers report having a drowsy driving episode even after longer sleep times. Dwsy

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Actions Taken When Feel Sleepy While Driving

While only about 11% of all drivers say they have nodded off or fallen asleep while driving in the past year, we asked all drivers what actions they take if they feel sleepy while driving. About one-half of all drivers mention multiple actions, most of which serve as a change of status quo that alters the current driving experience. The majority of actions are physical in nature rather than cognitive changes. It is important to note that drivers who have nodded off while driving take different actions than those who have never nodded off.

The largest proportion of drivers (43%) say they pull over and take a nap, while an additional 15% say they just pull over or get off the road. Six percent (6%) change drivers. About one in ten (9%) get out of the car to stretch or exercise. About one in four (26%) open a window to get air, while about one in five get a coffee or soda to drink (17%) or get something to eat (3%). One in seven (14%) say they turn on the radio or increase its volume, while an additional 3% say they sing or talk to himself or herself or another person (via cell phone) or a fellow passenger. [Figure 16-A]

By Gender and Age

Male drivers are much more likely to say they pull over and take a nap if they feel sleepy while driving (46% as compared to 39% of females), while female drivers are more likely to open a window (28% as compared to 24%). [Figure 16-B]

The prevalence of drivers taking physical actions such as pulling over to nap, getting out of the car to stretch or exercise, and pulling over to get off the road all increase somewhat with age. Just 33% of drivers under age 21 reports that they pull over and nap as compared to 48% of those over age 45. Similarly, just 3% of the young drivers get out to exercise or stretch as compared to 12% of the older drivers. Young drivers are most likely to rely upon turning the radio loud to keep them awake if they feel sleepy. More than one-third (35%) of drivers under 21 rely on this action as compared to just 6% of drivers over age 64. [Figure 16-C]

By Drowsy Driving Experience

Drivers who have ever nodded off while driving are more likely than those who have never nodded off at the wheel to open a window (34% as compared to 21% of those who have never nodded off), to get a soda or coffee (20% as compared to 15%), get out of the car and stretch or exercise (12% compared to 7%), and to turn the radio on loud (19% compared to 11%). Those who have never nodded off while driving are more likely to say they pull over and take a nap (46% versus 38%) or pull over to get off of the road (16% compared to 12%). [Figure 16-D]

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Outcome of Nodding Off on Most Recent Occasion

The overwhelming majority (92%) of drivers who have nodded off while driving within the past six months report that they startled awake. However, sizable proportions of these drivers' experiences had more dangerous outcomes. One of three (33%) wandered into another lane or onto the shoulder, while 19% say they crossed the centerline. In one in ten (10%) cases, the driver ran off the road. While it happened in only about 2% of the most recent drowsy driving episodes, it is estimated that approximately 292,000 drivers were involved in some type of crash within the past six months as a result of nodding off at the wheel. [Figure 17-A]

Involved in Crash as Result of Nodding Off Past Five Years

Less than one percent (.7%) of all drivers (1.4% of those who have ever nodded off while driving, and 6.4% of those who have done so in the past six months) report they have been involved in a crash within the past five years that they attribute to them nodding off or having to greatly struggle to keep their eyes open. This equates to 2.5% of drivers who have been in any crash in the past five years attributing a crash to drowsy driving.

Males are twice as likely as females to have been in such a crash (1.0% compared to .4%). While the total numbers of drivers involved is still small, drivers under age 30 are about six times more likely (1.8% have) to report involvement in a crash as a result of drowsy driving as are older drivers (.3%). [Figure 17-B]

While the proportion of drivers involved in a crash as a result of nodding off at the wheel is very small, the actual numbers of drivers involved in such crashes over the past five years is sizable. Figure 17-C shows the estimated numbers of drivers by age and gender involved in a drowsy driving-related crash, along with high and low ranges around the estimates.

An estimated 1.35 million drivers have been involved in a drowsy driving related crash in the past five years. About seven in ten of these drivers, or 972,000 were males, while 379,000 were females. Young drivers make a disproportionally high number of drowsy driving-related crashes, with about 274,000 drivers under age 21 involved in a drowsy driving-related crash within the past five years. These young drivers make up about 20% of all drivers involved in such a crash, yet these drivers under age 21 make up about 8.5% of the driving population. Similarly, about 44% of all drivers involved in a drowsy driving-related crash are in their 20s (594,000 drivers) yet they make up just 15% of the driving population. Relatively few drivers over age 64 (18,000) have had a drowsy driving-related crash in the past five years.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Perceived Threat of Driving While Drowsy

Perceived Threat of Other Drivers Driving While Sleepy or Drowsy
Virtually all drivers believe that other drivers who drive while sleepy or drowsy are a threat to their own personal safety and that of their family. Ninety-five percent (95%) believe this behavior by others to be a major threat, while 5% see it as a minor threat. [Figure 18-A]

By Gender

There is little substantive difference in the perception of the threat of other drivers who drive while drowsy or sleepy between male and female drivers. Male drivers are slightly more likely to view this behavior as a minor (6%), rather than a major (93%) threat to their and their family's safety as compared to female drivers (3% and 96% respectively). However, all drivers see the behavior as a personal threat to their safety. [Figure 18-B]

By Age

There is also little difference in the perceived threat of others' driving while drowsy or sleepy by age, with the exception that drivers in their 20s are more likely to see this behavior as a minor (8%) rather than a major threat (91%) to their and their family's safety. [Figure 18-C]

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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