Drowsy Driving and Traffic Safety
An Interview with Dr. Allan Pack
From Winter 1997Volume III, Number 3
Dr. Allan Pack is director of the Center for Sleep and Respiratory Neurobiology at the University of Pennsylvania. Dr. Pack served as medical director for the National Sleep Foundation for two and a half years and has done extensive research on sleep-related issues.
BB: How common is drowsy driving, and how many crashes result from it?
AP: There is disagreement on the numbers and how big a problem it is. If you take it from police accident report data, then you get estimates of somewhere between 1 to 1.4 percent of all crashes and about 4 percent of fatal crashes. However, many of us are concerned as to how accurate that information is, given that there's little police training [in detecting fatigue-related crashes]. Even if there were training, there is often no evidence at the scene that the driver may have fallen asleep.
Another way of looking at it is through survey data. In one survey in New York State, 25 percent [of the respondents] reported having fallen asleep while driving, and 4.6 percent reported having had a crash due to falling asleep or being drowsy. Crash rates were much higher in males. Almost 1 in 10 males and almost 1 in 20 people in New York State have had a fatigue-related crash at some point in their lives. Those numbers are very similar to those generated in the National Sleep Foundation's Gallup survey, in which 31 percent reported having fallen asleep at the wheel and 4 percent reported having a crash due to falling asleep.
BB: Who is most at risk for drowsy-driving-related crashes?
AP: There are a number of significant at-risk groups. Based on a review of North Carolina's police accident report database, 55 percent of these crashes occurred in people 25 or younger. The peak age of occurrence was age 20. This included only those crashes that were attributed by the police to the driver falling asleep and where no alcohol was involved. In particular, the largest group is young males.
BB: Why are youth--and young males in particular--at high risk?
AP: First, most fall-asleep crashes occur at night, as you might imagine. This is a group who are driving around at 2:00 or 3:00 in the morning while the rest of us are in our beds. Second, we know that youth as a group are chronically partially sleep-deprived. They stay up late, they cut their total sleep time down, and they are more sleepy during the day than other age groups. Finally, with all drivers and especially with youth, there is a significant interaction between sleep and alcohol. In a chronically sleep-deprived group, a single beer can have profound effects.
BB: Who else is at risk?
AP: Shift workers. These are people who really are chronically sleep-deprived because of what society asks them to do. We ask them to work at night and try to sleep in the daytime, and it's difficult for them to sleep in the daytime because their biological clock is telling them to be awake.
Another important at-risk group is people with undiagnosed sleep disorders, particularly sleep apnea. We know that sleep apnea occurs in 4 percent of middle-aged males and 2 percent of middle-aged females and is associated with three to seven times the risk of car crashes.
Business travelers are also at risk. They drive a lot of miles, and they don't sleep particularly well in hotels. The National Sleep Foundation did a survey with the Hilton Hotels, and over 50 percent of people reported difficulty sleeping in hotels on the first night.
BB: When many people think of drowsy driving, they think of commercial drivers as the primary culprits. Is this the case?
AP: There is no question that fatigue is probably the number one cause of crashes in that group. But the [drowsy-driving] problem in noncommercial drivers is actually larger in terms of numbers of crashes.
Still, commercial drivers are a significant risk group for fall-asleep crashes. They spend many hours on the road. They frequently drive at night. Many of them keep very irregular schedules and are chronically sleep-deprived. Some data also suggest that commercial drivers have an increased risk of sleep apnea. One of the major risk factors for sleep apnea is obesity; it's the fat in your neck that helps close your airway when you go to sleep. And we know that commercial drivers as a group are more obese than the rest of the population, so it makes sense that sleep apnea is more common in this group.
There are also serious issues about where commercial drivers sleep. The number of rest areas and truck stops across the country is woefully inadequate. So, these drivers may feel really sleepy and want to pull off the road somewhere and sleep but there aren't always places for them to do that. They often pull over on the shoulder of the road and just fall asleep. But often what happens is that the police move them on because they are frightened that the trucks on the shoulder of the road are a safety hazard. Some towns have actually passed ordinances that make it illegal for truck drivers to pull over to the shoulder and sleep.
There is also a lack of information about drowsy driving among truck drivers. We did a focus group with commercial drivers, and not one of them had ever heard of sleep apnea. If there's one group in the country who needs to know about sleep and sleep apnea, it's commercial drivers.
BB: What are the best countermeasures for drowsy-driving-related crashes? And what are the best ways for highway safety and public health professionals to be involved?
AP: I believe that the single most important thing is prevention. People will debate whether you can educate people to really take sleep seriously. I think you can. With alcohol we didn't say, "Look, it's ok to take a few drinks and then if you are really impaired just drink some coffee and you'll get home." We said, "This is unacceptable." And I believe that drowsy driving is unacceptable.
If you look at the drowsy-driving survey in New York State, 50 percent of drivers involved in a drowsy-driving collision had been awake for more than 13 hours at the time of the crash. Twenty percent had been awake for more than 20 hours. So there are two clear risk factors: driving at times of increased sleep need and driving after long periods of prior wakefulness. The most important thing we can tell people is to make sure they have adequate sleep before driving, and to really think about it if they are going to do all-night driving, because that's when most of these crashes occur.
BB: In addition to educating drivers, what else can states do to prevent fall-asleep crashes?
AP: Continuous shoulder rumble strips have been shown to be very effective. With rumble strips, anyone who has a single vehicle roadway departure will hit the strips, wake up, and realize that they are leaving the road. There are fairly good data showing that these can reduce crash rates. Rumble strips are not a new concept. They were first introduced on the Garden State Parkway in New Jersey in 1955, but they have taken a long time to be implemented. The best study was done in 1985 in the Mojave Desert, where there was a 46 percent reduction in single vehicle roadway departure crashes in areas that had rumble strips.
BB: So why aren't they everywhere on the highways?
AP: That's a really good question. When I was with the National Sleep Foundation, we believed that all major rural interstates should have continuous shoulder rumble strips and we were aggressively pushing to implement them. New York State now has a policy to install rumble strips whenever major roads and rural roads are repaved. The Pennsylvania Turnpike has them across the whole turnpike. Yet here in the Philadelphia area, we have the Atlantic City Expressway, which is probably dangerous because of all the people coming back from the casinos late at night. It still doesn't have rumble strips. There is an area down near Hammonton (New Jersey) the police call the "dead man's zone." They have a big sign with a flashing light on it saying "Don't Fall Asleep". It is pretty clear they know they have a problem, and yet there are still no rumble strips on that expressway. The important message to get out to the traffic safety community is that they need to develop policies with respect to rumble strips. A National Sleep Foundation consensus panel concluded that the data support that all major roadways should have them. And they are very cheap to install.
BB: What other groups should traffic safety and injury prevention professionals be working with to reach some of the at-risk populations?
AP: First, there are a number of accredited sleep centers around the country. The American Sleep Disorders Association [1610 14th Street, N.W., Suite 300, Rochester, MN 55901, phone (507) 287-6006] accredits sleep centers and can provide a list of them. Most states have at least one or two. So that's a way for state officials and injury prevention professionals to get expertise about sleep. Second, both the National Sleep Foundation and the AAA Foundation for Traffic Safety have been very active in the issue [see article, this page]. There are AAA clubs all over the country that provide a good way to reach drivers.
Bill Cullinane, executive director of SADD, is very interested in this issue. And because of the interaction between sleep and alcohol, it is important that organizations that target youth begin to incorporate drowsy driving into their messages.
Physicians can also play a major role. Sleep physicians are very passionate about this issue and are very committed to what we are doing. Primary care physicians don't know as much about sleep as we would like them to know, and might not take it as seriously as we would like them to. The reason for that is fairly straightforward: until recently, most medical students never heard anything about sleep and sleep disorders. The National Institutes of Health [NIH] has recognized that this is a big issue and has awarded a number of research grants in the area. Some of these grantees are developing model curricula on sleep-related issues for medical schools as well as ways of reaching primary care physicians. NIH has a public awareness and physician awareness campaign about sleep apnea and has been involved in programs about sleep issues at national meetings of primary care physicians. Primary care physicians need to become part of the solution, but that's going to take a real educational effort. Remember, physicians are also a critical target group, because they are at risk themselves as shift workers.
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