Impaired Walking Vs. Impaired Driving: Pick Neither

Q: I’ve heard that if you’re drunk it’s more dangerous to walk home than drive home. Is that true?

A: If you were to watch any impaired driving PSA from the Washington Traffic Safety Commission you might notice that among the suggestions for how to get home safely, walking isn’t included. Impaired walking is dangerous. Over half of pedestrians killed in traffic crashes were walking impaired.

However, to say that it’s more dangerous than driving impaired is misleading. I mean, you could (mis)use data to make that point but, if you make a proper comparison, impaired driving remains the number one risk factor in traffic fatalities.  

You didn’t mention where you heard it, but there seems to be one primary source – the economist/journalist team that wrote the book Freakonomics and has a podcast by the same name. If you heard it somewhere else, it’s likely that you could follow a trail back to the Freakonomics guys.

I’m a fan of Freakonomics, both the books and the podcast. These guys are way smarter than me and I’m uncomfortable saying they’re wrong. But on this one, I think they made a mistake. They state that it’s eight times more dangerous for an impaired person to walk a mile than to drive a mile. I’m not challenging their source data; I’m willing to trust that they were thorough in their information gathering. Here’s the problem; they used miles traveled to make their comparison. That works fine when comparing modes of transportation with similar speeds. For example, it’s useful when comparing the risk of riding a motorcycle versus driving a car. (In case you’re wondering, the fatality rate when riding a motorcycle is nearly 28 times that of driving a car, per mile traveled.)

Comparing cars and motorcycles works because similar travel speeds mean similar times of exposure to risk. If a motorcycle and a car both travel the same 50-mile stretch of road at 50 mph, they’ll both have one hour of exposure. Because vehicle miles traveled is a measure of exposure using distance instead of time, it’s really only useful for vehicles that travel at similar speeds.

Adult humans walk at a pace of about three miles per hour. When you add up all the road types we drive on, we average somewhere between 35 and 45 miles per hour when we drive. Your own average may be more or less than that depending on where you live and where you go, but it’s close. An hour of walking will get you about as far as four-and-a-half minutes of driving. Based on exposure time, driving impaired is still about 50 percent more deadly than walking impaired.

And regardless of which one is more dangerous, there’s still the issue of who is at risk (and the Freakonomics guys pointed this out too.) An impaired pedestrian is a threat to themselves; an impaired driver is a threat to everyone on (or near) the roadway. In Washington, half of all traffic fatalities involve an impaired driver. That’s over 3000 people in the past decade.  I began this by noting the risk of walking impaired, but some of that isn’t the fault of pedestrians. Fifteen percent of impaired pedestrians killed in traffic crashes are struck by impaired drivers.

But it’s not a binary choice. We have better options – taking a cab, rideshare, or bus, choosing a designated driver, staying with a friend, booking a hotel room, you can probably come up with more. With all these options there’s no excuse for impaired driving. Driving and walking impaired can both be avoided by some basic planning ahead.