Study shows that driving drowsy is as dangerous as driving drunk

they drive by night
Screen capture They Drive by Night

In Toronto, Canada yesterday, at least 29 pedestrians and cyclists were hit by cars; one died. Many are calling it a public health crisis yet the Toronto Police department spokesperson tells the local paper that “I have no idea why it’s happening. It could be the weather, the darkness … anything.” This seems to be the standard response in most cities: nobody has any idea.

Perhaps we can suggest one: Cars are heavy machinery and need to be operated slowly and carefully when it is dark and the weather is crummy. Furthermore they should not be operated while drowsy, which many people are during the evening drive-home hours; a new study by the American Automobile Association determined that driving while sleep-deprived is as dangerous as driving drunk. 35 percent of drivers get less than the recommended seven hours sleep every night and drowsy driving contributes to more than one in five fatal crashes in the US each year.

sleeptime© AAA

“You cannot miss sleep and still expect to be able to safely function behind the wheel,” said Dr. David Yang, executive director for the AAA Foundation for Traffic Safety. “Our new research shows that a driver who has slept for less than five hours has a crash risk comparable to someone driving drunk.”

The AAA study used data from the NHTSA’s National Motor Vehicle Crash Causation Survey, which looked at a sample of police-reported crashes. It probably understates the problem because it excludes people who had heart attacks or strokes before the accident, even though sleep deprivation might have contributed to those. It only includes those crashes where the police are called, and most oddly, excludes crashes that happen between midnight and 6 AM, because that’s how the original crash causation study was set up. But the conclusions are still dire.

impaiment© AAA

This study’s estimate of the crash risk associated with driving after having slept for 4- 5 hours in the past 24 hours compared with 7 hours or more is similar to the NHTSA’s estimates of the crash risk associated with driving with a BAC [Blood alcohol concentration] equal to the level that all U.S. states have set as the per se legal limit, and the crash risk associated with having slept for less than 4 hours is comparable to the crash risk associated with a BAC of roughly 0.12 – 0.15.


Which brings full circle and back to Toronto. There is a reason that pill bottles say “may cause drowsiness, do not operate a car or heavy machinery”- because that is what cars are, heavy machinery. Driving is hard, perhaps the hardest thing most people do in their lives regarding attention, forethought and hand/foot/eye coordination. The fact that a lack of sleep or a glass of wine has such a dramatic effect on our ability to drive is just more proof of how hard it is.


Cars are brilliantly designed to protect the occupant with air bags and crush zones, but they are still deadly to those outside. The very popular SUVs and pickup trucks are even more deadly. Yet it seems that the people who get the most attention and blame are those who get hit, those kids in black clothes and headphones who just jump out of nowhere. Even though the statistics show that 60 percent of those who are hit are senior citizens, not kids. So what does the Toronto Police do? It shows a poor old lady with a walker staring ahead at six lanes of speeding traffic and tells her to be alert and think.

Meanwhile, this morning, Toronto’s Constable Brister says he has no idea why these crashes are happening, but everybody knows it is dark at night, and that it sometimes rains while it is dark. He knows perfectly well what is happening: People are driving too fast for the conditions, and our roads are designed to carry cars at high speed, not to protect pedestrians and cyclists.

Erica StarkGlobe and Mail/Screen capture

Furthermore, drivers have no incentive to slow down, because it is almost risk free; they are relatively safe in their bubble and they know what happens if they kill someone in their car: not much. They read the news and note what happened to the driver who recently drove onto the sidewalk and killed a woman just standing there, minding her own business and her dog; she lost her licence for a month and was fined a thousand bucks.

There are many things that the City and the other levels of government could do:

  • Get serious about Vision Zero and redesign our streets for safety, not speed;
  • Make SUVs and pickups comply with the same safety standards as conventional cars;
  • Take the driving licences away from people who kill with their cars;
  • Recognize that driving is hard, requires real skill, and have harder tests with regular retesting.
  • And most importantly, stop pretending “we don’t know why this is happening”. Everybody does, it is a choice society has made. But as shown in Sweden with Vision Zero, it’s not the only choice.

Tags: Cities | Transportation

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