Driving in Snow and Risk Homeostasis : The Frontal Cortex

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Jonah Lehrer is a contributing editor at Wired. He's also written for The New Yorker, Seed, Nature, and the New York Times and is a contributor to Radiolab. He's the author of Proust Was A Neuroscientist. His new book is How We Decide.

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Driving in Snow and Risk Homeostasis

Posted on: December 4, 2007 10:05 AM, by Jonah Lehrer

I had the pleasure of driving for a few hours in yesterday's New England blizzard. (I was coming back from a radio interview for "On Point," which is broadcast out of WBUR in Boston. You can listen to me here.) While driving up a white I-93, I counted more than a dozen vehicles that had lost control, zoomed off the highway shoulder, and ended up trapped in snow banks. So far, so normal. A snow storm makes for treacherous driving. But here's the surprising observation (at least, it was surprising to me): 8 of the 13 cars were trucks. Big, brawny 4x4's. The kind of vehicle that people buy because it can drive in the snow.

Obviously, my sample size was small. But I wonder if truck-drivers in inclement weather drive with a false sense of confidence. It's better to have four-wheel drive in the snow, but an icy road is still an icy road. This hypothesis would dovetail with research showing that drivers with various safety options (air-bags, ABS, etc.) tend to drive more recklessly and are responsible for more accidents. (This is known as risk homeostasis.) In other words, the safer we perceive our cars to be, the less safely we tend to drive them.

For more this research, check out the work of Fred Mannering.

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Comments (15)

I don't own a truck, but doesn't one need some counterweight in the flatbed to balance the engine block's weight for winter driving? Height only gets you above the snow to drive through it.

Posted by: mdiehl | December 4, 2007 10:35 AM

The link on my name is to an article Barry Ritholtz wrote four years ago on the subject. He noticed the same phenomenon you did. I've noticed it as well: the 4WD truck drivers get overconfident and don't slow down.

mdiehl: I think he was referring to SUVs, not pickup trucks (this is metro Boston), but yes, that's something to worry about.

Posted by: Eric Lund | December 4, 2007 10:45 AM

We see that (4x4's in ditches) all the time in Wisconsin. You know when you step on the brake all the vehicles are 0-drive, and the folks in the big, usually fancy trucks seem to miss that. They can get out sometimes with that 4x4 though. Also the first snow of the year always has a lot of accidents. People forget how to drive and storms that in March would be almost shrugged off are big deals in November.

Posted by: Markk | December 4, 2007 10:49 AM

For a good layman's discussion, see Malcolm Gladwell's New Yorker article, Big and Bad, published in January 2004. It is reprinted in full on his website (gladwell.com). In it, he argues that consumers equate big and heavy with safe, and that hence it is their desire for safety and not the reality of safety that drives them to buy 4x4's, SUV's or whatever we choose to call these behemoths. In other words, it is a feeling rather than a rational calculation, and one that they continue to hold even when presented with hard evidence that their big car is not as nimble or as safe as smaller cars. They refuse to abandon the feeling of safety! Apparently, the US auto industry has made extensive use of the work of a Frenchman named Rapaille on the cortex impressions of consumers--he is interviewed in the article. Fascinating.
Here in the Seattle area, radio announcers have taken to referring to "rollovers" when they report freeway accidents, and everyone knows that means the accident involves an SUV.

Posted by: peggy | December 4, 2007 11:10 AM

There was a blizzard? Here in Somerville we only got a couple of inches; hardly worth counting.

It's just like the people who end up getting killed in their SUVs because they aren't wearing their seat belts, a lot of drivers just assume they're safer than they really are because of the 4-wheel drive and the size of the vehicle. If these cars are going off the road, it's likely operator error. I drove a tiny Honda Civic through ten years of New England and upstate New York winters and never had that kind of problem.

Posted by: Moopheus | December 4, 2007 11:10 AM

A lot of these drivers can't seem to grasp the idea that if the vehicle can go in the snow, that doesn't necessarily mean it can stop in the snow.

Posted by: NJ | December 4, 2007 11:13 AM

We just had our first real snow as well and the same thing happened. The simple fact is that they don't know how to drive them.

One of the things I enjoy doing is sitting in my favorite coffee shop and watching a soccer mom with the white lexus suv slide through a red light in middle of a storm. Every season I see at least 5 or 6 of these. The expression on their faces is priceless.

Posted by: tim | December 4, 2007 11:17 AM

Risk homeostasis may be playing a role, but so may selection bias - 4-wheel drives are less likely to get snowed into a parking space or stuck, so they're more likely to be on the road after a snowstorm and people who have some reason to want to drive on heavy snow are more likely to buy a 4-wheel drive.

Heightened risk and taking preventative measures are generally correlated, making frequency comparisons from the general population to determine the effectiveness of the preventative measure inherently iffy - for example, I'd expect people who own bullet-proof vests to be fatally shot much more often than those who don't, but not because bullet proof vests make them less safe.

Posted by: MattXIV | December 4, 2007 11:35 AM

In my humble opinion, risk homeostasis could have been a factor even though your sample was small.
We are so inclined to think in stereotypes as shortcuts in this modern, complex world! So, thinking my vehicle is safe,(maybe invincible, LOL) due to the 4 wheel drive and big tires, so that gets pidgin holed into the, "don't have to think about it anymore box" and away they go! Unfortunately sometimes into the snow bank!
Without the shortcuts to allow us some sort or calm baseline homeostasis modern life would be way too much!
Hopefully your post has reminded some drivers that driving safety may be a good concept to keep out of pidgin holes! ( and snow banks too!) LOL!
Dave Briggs :~)

Posted by: Dave Briggs | December 4, 2007 12:56 PM

Another factor is that a higher driving position decreases the perception of speed. See, for example:

http://www.experts.renault.com/dsc2001/speed-and-safety.pdf

Posted by: mph | December 4, 2007 1:53 PM

and how many of these had masshole plates? what was the ratio there?

quick quiz, the aircooled VW bus is the best snow cah evah. why?

Posted by: BikeMonkey | December 4, 2007 2:50 PM

There are a lot of factors involved, but the biggest is just plain driver stupidity. As far as sureness of stopping was concerned the best vehicle I had was a frontwheel drive 79 Suburu. For some reason the status of your wheels traction was transmitted to your brake foot. The worst for stopping was a Toyota Landcruiser (one of the best for going), in it you didn't know your vehicle was skidding except to look out the window and see the orientation of the vehicle changing!

I have driven zillions of miles in snow (up to 3feet unplowed) in Wisconsin, and the mountains, you see the same effect with the ability to get cars to go. A lot of clueless drivers have SUVs and just can't make them go(or stop) in snow. A little knowledge of physics, and about skidding goes a lot further than technology. The only intrinsic problem with the fourwheel drives is that if you don't occasionally tap the brakes hard to test stopping ability, you might become unaware of how slippery the road has become.

Posted by: bigTom | December 4, 2007 5:36 PM

The number of people who drive SUVs and use the size of the vehicle to intimidate other drivers appears, to me, to be on the increase.
Whatever psychosis drives it I think there should be legislation to make SUV drivers consider their actions.
This could be a sliding scale of speeding tickets $50 for a 1 ton vehicle $250 for a 2.5 ton vehicle or some other scheme that reflects the fear they impose on other road users.

Posted by: driving course | December 5, 2007 7:37 AM

Trucks have a higher center of gravity that naturally makes them more dangerous and unstable at high speeds on roads.
Combine physics with risk homeostasis and a little survivor bias and you have a pretty good explanation.

Posted by: Invictus | December 5, 2007 3:56 PM

I have the same perception "driving course" does about SUV drivers. It seems that some (often male) knowingly use the superior size/heft of their vehicle to intimidate other drivers (by driving too closely behind someone going the speed limit, passing on the right, etc.), or use the superior size/heft of their vehicle to justify multi-tasking behind the wheel and hence driving distractedly, erratically and dangerously (often female). Obviously, I have no scientific evidence to back my claim, and realize I could be charged with thinking in terms of sexual stereotypes. That's okay with me; I trust both my empirical and subjective sense of the experience I have of driving these days to run the risk and even plead guilty as charged.
In the last six months I have seen one SUV driver making sandwiches while driving (several sandwiches, a real industrialized production, with pieces of bread spread out across the front seat), and another reading a catalogue while talking on the phone and driving 60 mph across a bridge in bad weather. Both were women. I will refrain from making a generalization based on this limited experience, but the phenomenon is nonetheless troubling.
I cannot count the number of male SUV drivers I have seen slaloming down the highway, weaving in and out of lanes, tailgating at high speeds, etc. I have also seen many drivers of other, smaller vehicles endangering the lives of others by driving as if they were playing a video game (could there be a connection?), so I'll resist the temptation of generalizing about male SUV drivers.
Obviously, it is unfair to single out those behind the wheel of an SUV as the only reckless drivers on the road. But I sometimes wonder if, because they feel safer, they allow themselves to drive in ways that endanger the lives of other people. And on some very deep level, that just does not seem right.

Posted by: peggy | December 6, 2007 6:00 PM