Survivor bias: Who walks away from automobile crashes?

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This photo of a damaged car has little to do with this post. 

Then my friend Alex E. asked, “Is there a reason why?”

I can’t leave such a question hanging. I thought I read that somewhere, and it was probably in Tom Vanderbilt’s book, Traffic. What I found in there mostly referred to trucks (the semi-trailer type) because of their mass and how people not driving trucks behave around them on the road. The second part explained the statistics around who lives and dies in crashes involving a drunk driver.

Knowing that, and knowing the story I tweeted a link to, you’ll see that the event didn’t involve a truck and my relating them was perhaps unsuitable. It did involve drunk driving, but I may have misread the book text.

Here’s what Traffic says about trucks

“When trucks and cars collide, nearly nine of ten times it’s the truck driver who walks away alive.” Vanderbilt discusses how that is (page 247).

…we all likely have proof of the dangerous nature of trucks. We have seen cars crumpled on the roadside. We’ve heard news stories of truck drivers, wired on stimulants, forced to drive the deregulated trucking industry’s increasingly long shifts. We can easily recall being tailgated or cut off by some crazy trucker.

Just one thing complicates this image of trucks as the biggest hazard on the road today: In most cases, when cars and trucks collide, the car bears the greater share of what are called “contributory factors”.

Really? Car drivers caused crashes with trucks and then die from it?

Instead of relying on drivers’ accounts, he [Daniel Blower at Michigan Transport Research Institute] looked at “unmistakable” physical evidence. “In certain crash types like head-ons, the vehicle that crosses the center much more likely contributed to the crash than the vehicle that didn’t cross the center line”.

After examining more than five thousand fatal truck-car crashes, Blower found that in 70 percent of cases, the driver of the car had the sole contributing responsibility in the crash.

Basically, the car drivers in a car-truck crash caused the crash and ended up being the ones dying.

…the reason trucks are dangerous seems to have more to do with the action sof car drivers combined with the physcial characteristics of trucks and less to do with the actions of truck drivers. “The caricature that we have that the highways are thronged with fatigued, drug-addled truck drivers is, I think, just wrong”, Blower said.

“In a light vehicle, you are correct to be afraid of them, but its not because the drivers are disproportionately aggressive or bad drivers”, Blower said. “It’s because of physics, truck design, the different performance characteristics. You can make a mistake around a Geo Metro and live to tell about it. You make that same mistake around a truck and you could easily be dead.”

What Traffic says about drunk driving

Of the 11,000 drunk-driving fatalities studied by economists Steven D. Levitt and Jack Porter, 72% were the crash-causing drunk driver or their passengers, and 28% were the other drivers (most of whom were not drunk themselves) (page 251).

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About Steven Vance

Enthusiast for urbanism, bicycling as transportation, and open data. Building a bicycle culture in Chicago.
  • Jennifer

    Does it get any more Robot Car than “killed when the SUV they were in fell at least 50 feet”?

    Are you disagreeing with Vanderbilt on car-truck crashes? Because I think there’s some truth to what he says. Drivers pull similar stunts around both bikes and trucks, it’s just that trucks are much, much larger.

    • http://www.stevevance.net/ Steven Vance

      I wasn’t disagreeing at all with Vanderbilt. The whole book gives all the research references. I meant that my memory was bad and I applied what I thought I knew to the wrong situation.
      Why *are* Robot Cars jumping off bridges with their occupants?

  • http://twitter.com/aka60643 AKA60643

    The idea that car drivers are at fault in most car-truck crashes is consistent with my experience on the road. Most truck drivers drive in predictable, safe ways. If other road users (car drivers, cyclists, pedestrians, etc.) share that space in predictable, safe ways and are mindful of a truck’s slower stopping time and less maneuverable nature when making any move that creates a potential conflict path with that of the truck, then crashes generally don’t happen. However, too many folks are distracted, sleepy or just not mindful of a truck’s limitations, and then s*@! happens.

    How many people make the mistake of assuming that a truck driver can see them, forgetting or just being unaware that a truck driver’s sightlines are extremely limited compared to most other road users? When I’m riding my bike on south side streets where I encounter big trucks, I make a point to smile and wave when I see them coming. It’s not just to be friendly. I’m trying to make sure they see me before they get too close.

    Occasionally I see problems due to truck drivers speeding or appearing to be overtired or distracted, but most of them are professionals out there.