Aggression and Accidents

Last post, I presented research showing that men are more deadly than women when behind the wheel. Researchers presume this is because men have a predisposition toward aggression and thrill-seeking, thanks to the testosterone that helped our male ancestors stalk, struggle and seduce their way to successful gene replication.

This narrative makes the assumption that aggression and sensation-seeking lead to bad driving. Do they?

Marianne Junger, Robert West, and Reinier Timman think so. They examined traffic accidents in the Netherlands, using police data to determine if the reckless driver in each crash had a criminal record. They found that drivers who contributed to accidents were much more likely than the general public to have been guilty of violent crime, vandalism, property crime, and serious traffic violations. Aggression and risk-taking do indeed appear to be associated with bad driving.

The authors attribute the apparent link between lawlessness and risky driving to “a general disregard for the long term adverse consequences of [one's] actions [which] could be labeled risk-taking, impulsiveness, or lack of self-control.” So, on the admittedly unlikely chance that Dennis Rodman offers you a ride in the near future, think twice.

Is a predisposition to this kind of aggression and thrill-seeking a biological trait? Many researchers believe it is, but other work suggests the issue may be cultural as well. Scholar Michael Sivak has done interesting research on the issue of aggression, thrill-seeking and bad driving, this time on a society-wide basis instead of an individual one.

Sivak examined traffic fatalities in the 50 states plus DC. There is a surprisingly wide gap in accident rates between states. Hard as it may be to believe for those of us who have braved the roads of Boston, the safest state is Massachusetts. Its residents experience about one third the number of fatalities per mile driven as residents of Montana, the most dangerous state.

Sivak tested a number of factors that might cause a place to have more or fewer road fatalities. Three variables came up as statistically significant. The first was the share of the population of drivers who are under age 25. States with proportionately more young drivers tend to have more road fatalities. As anyone who has ever: 1) been a 16-year-old, or 2) been driven by one can tell you, the fact that young drivers have safety issues is not necessarily something we need lots of fancy econometrics to adduce. More on the behavior of young drivers another time.

The other significant variables were homicide rates and accidental death rates; when all else is held equal, both are generally higher in states with lots of deadly traffic accidents. (In fairness to the good people of Montana, their state, with a low murder rate, is an exception.) So our suspected link between aggression (murders), thrill-seeking (non-auto accidental deaths) and fatal crashes appears to be confirmed.

Sivak helpfully updated the original study in 2009. This time, he found that seven variables are important predictors of fatal traffic accident levels on a state-by-state basis:

  • homicide rates (a + relationship with road deaths)
  • the size of the state’s physician population (a -? relationship with road deaths, presumably because more doctors indicates better medical care)
  • the share of older drivers (+ deaths, which I’ll also address another time)
  • gender (more men equals + deaths, confirming what we’ve learned earlier)
  • seat belt usage rates ( – deaths, for obvious reasons)
  • income per capita ( – deaths as income rises)
  • statewide deaths from alcoholism (a variable designed to capture drunk driving levels and a +)

As a package these variables were very powerful predictors of fatality rates. And the single most significant variable was the homicide rate. (Note that this model didn’t include a non-auto accidental deaths variable.)

It is doubtful that fatal traffic accidents are causing drowning in swimming pools or that committing the act of murder somehow causes a person to drive recklessly (except maybe when he’s driving the getaway car).

So there is almost certainly a hidden force at work, which varies across societies and which causes criminal aggression, thrill-seeking, reckless behavior and bad driving. I can only speculate, but perhaps this general incivility has to do with things like the effectiveness of local policing, the local unemployment rate, and particularly local cultural and behavioral norms, for example in terms of attitudes towards authority.

In any event, I’m pleased to say that we in Los Angeles County have an extremely low auto fatality rate, below even that of Massachusetts. Undoubtedly this is because we are a more sophisticated and urbane bunch than those of you in the rest of the country. Or perhaps it’s because traffic here never moves fast enough for our crashes to be fatal.

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  1. zeelurker says:

    I suspect the low fatality rate in Los Angeles County is not due to the fact that residents are safer drivers but instead a result of the slow speeds due to rampant gridlock throughout the county.

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  2. Traciatim says:

    Maybe they just have really low blood sugars? All these guys need to eat more cookies, the world would be a much safer place.

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  3. ScottF says:

    What about a correlation to how rural or urban the population of a state is?

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  4. Finn says:

    Traffic in Massachusetts, like that in LA County, tends to be at relatively low speeds because of congestion. The speed factor may be far more important than the other issues mentioned–and would account for the low murder rate and high traffic mortality rate in Montana.

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  5. Sally says:

    Yeah, I live in Montana. I’m pretty confident two of the big causes of fatalities we have are drunk driving (we are one of the worst in the nation) and horrible road conditions. In the winter our crazy mountain roads get coated with ice and snow and make for great fun.

    So again, driverless cars FTW!

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  6. YX says:

    I drive through Boston everyday to/from work, and I seriously doubt at any given time I was going fast enough to kill anyone.

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  7. John B. Chilton says:

    Like first commenter my guess is “the hidden force at work” is the average highway speeds. Low average tends to mean congestion due to high volume — e.g. your own example of L.A.

    As to Montana, there’s little congestion and there are long distances to travel to get anywhere. If I’m not mistaken folks drive well over the posted speed limit.

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  8. GoBobbyGo says:

    Your last sentence reads like a throwaway, but I wonder if there’s more to it.

    Has anyone looked at the proportion of highway miles driven to local road miles driven?

    Based on other things you’ve written on the subject, I’d be stunned if that weren’t a factor. And it feels intuitive that people do more highway driving in Montana than they do in Massachusetts.

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