The GMC Suburban Arms Race
Unintended Consequences of Automobile Safety
There’s been an uproar on urbanist twitter. When Barrett O’Neill posted a picture of their totaled car and a cautionary tale about keeping his family safe, it inspired a myriad of responses.
Jerimiah Lee Lanca responded with a similar sentiment. They tweeted about how they purchased a large SUV in order to keep their family safe from traffic violence.
Most responses were frustrated or mocking. The underlying sentiment was that in the effort to keep their families safe, these two men had, in fact, made the roads a more dangerous place for everyone else.
One meme in particular made the rounds. Each quote tweet suggesting an even more ridiculous vehicle that one might buy to protect one’s family: from an A1 Abrams Tank to an AT-AT Imperial Walker from Star Wars. The implicit message was: this logic of having the bigger vehicle to keep safe can clearly get out of hand to the point of absurdity. It points out how automobile safety is a kind of arms race.
An arms race is a type of vicious cycle characterized by positive feedback loops driven by retaliation resulting in a downward spiral in which everyone is worse off with respect to the independent outcome than they were before. Take for example the naval arms race between Britain and Germany prior to WWI. It began with Britain's “two-power” standard, the policy that their navy should be at least the size of the next two largest navies combined, in order to maintain their naval supremacy and security as an island nation. In response to worsening relations between the two nations, German admiral Tirpitz wanted to increase the size of the German navy to threaten British supremacy and force Britain to make diplomatic concessions. But it didn’t work that way. Instead, in 1906 Britain launched the first Dreadnought class ship. The largest gunship ever seen at that point. Germany responded by commissioning their own Dreadnought ships in 1908. In response the British public demanded the production of more dreadnought ships, which further escalated Germany’s naval construction. All told, Britain made 19 Dreadnoughts while Germany made 13. Britain's goal in all this was to maintain the safety of their country, while Germany hoped it would spur more favorable diplomacy. Instead the build up and resulting increased tensions contributed to the breakout of WWI. The outcome was quite literally the opposite of what both nations intended.
As SUVs have become more popular in the United States, we see a similar phenomenon with regard to safety. SUVs have several safety benefits in and of themselves, but they also make those around them less safe.
First, the basic physics of an automobile impact advantages the person in the heavier vehicle. The heavier vehicle transfers more force to the smaller vehicle, and thus to the occupants of that vehicle. But this works the other way too. In a collision with a large vehicle like a freight truck the difference in weights won’t be quite so large and so it won’t be quite so much of a loosing proposition.
Second, in the event of two vehicles of different sizes colliding, the vehicle with the higher bumper height is going to fare better. The bumper is your first line of defense against a crash. It absorbs some of the energy of the crash so that you don’t have to. Over the years, car manufacturers have added more and increasingly sophisticated energy absorbing structures to cars, like crumple zones, which means relatively little of the energy of the collision actually makes it to the occupants. Unfortunately, many of those energy absorbing structures align with the bumper height. So the higher above your bumper the main structure of the other vehicle is, the less effective your car's energy absorption is going to be, and the more likely you are to be hurt. SUVs and trucks have relatively high bumper heights, and getting higher, which means extra safety in the event of a collision.
But you may have noticed the flip side to both of these benefits. Those in compact or even normal sized sedans are less safe. Each person that chooses an SUV or truck over a car increases the chances that when a car driver is in an accident it will be with a heavier vehicle with a higher bumper height. So it isn’t just a one way street. Choosing a truck or SUV makes you safer, and those in smaller cars less safe.
We might now see how the mechanism of retaliation works. With each oversized vehicle on the road, it becomes a more dangerous place for the rest of us. The safety of the person inside that vehicle goes up, but the safety of everyone outside goes down. So some of those others also choose a big oversized vehicle to ensure their safety. For each person that makes such a choice, the danger increases to those who have yet to make it, thus pushing harder and harder on those who remain outside to buy such a vehicle. Each new adopter adds motivation which further increases adoption: a positive feedback loop.
So what's the problem? Everyone gets a big car and we’re back to where we were with no one having any advantages except now everyone is a little safer from freight trucks and the like right?
There are three main problems with this sentiment. First, without a source of negative feedback there is no equilibrium to this system. It doesn’t end with everyone in bigger vehicles and a little bit safer. It ends with those with the means getting increasingly large and dangerous vehicles. A stratification of safety based on how many resources you can dedicate to your own personal tank.
Second, there are innumerable secondary and tertiary consequences to larger vehicles aside from safety. They degrade roads more quickly (a phenomenon called the fourth power law) and thus increase the cost of infrastructure maintenance. They take up more room, meaning more room that must now be dedicated to roads and parking and less space dedicated to good places to be. It forces people who might dislike cars and the lifestyles they necessitate to buy a car and spend that money on a way of life that makes them less happy. Even assuming the inaccurate picture of everyone being equally safe, there would still be negative consequences.
But the problem I want to focus on is that large trucks and SUVs are not actually safer for the occupants. They are also dramatically less safe for people outside of the vehicles as well. Therefore the end result is actually that everyone is less safe.
One reason large vehicles are less safe is because they make it more difficult to avoid an accident. The same physics that protects the occupants gives a larger vehicle more momentum. More momentum means it is more difficult to change directions or slow down and stop. SUVs and trucks have longer stopping distances. SUVs and trucks are also less maneuverable. These same vehicles also have larger blind spots, especially in the front of the vehicle. So while the occupant of an SUV or truck is less likely to be as injured or killed in an accident, driving one also makes accidents much more likely to occur, thus offsetting those safety gains.
In addition, the safety gains of a larger vehicle are primarily from front and rear end collisions. Side collisions, or collisions while maneuvering can actually be *more* dangerous in a Truck or SUV. This is because of their increased risk for rollovers. Not only are rollover accidents more likely in a large vehicle, but they are substantially more dangerous than other kinds of collisions. Being safer in a front or rear end collision seems like less of a benefit when you simultaneously increase your chances of being in a more dangerous kind of collision.
This doesn’t just play out against other vehicles either. The vehicular arms race is devastating for those outside of a vehicle. For pedestrians and cyclists, death risk is strongly correlated with vehicle height. Vehicle weight also increases the risk of death for pedestrians and cyclists. Your chances of survival as a person outside the vehicle are highly dependent on vehicle speed. But heavier vehicles are more dangerous at those lower speeds, making pedestrians and cyclists chances of surviving being hit by a larger vehicle much lower than from a smaller car.
Even the ones purchasing these behemoths might find themselves on the receiving end of this increased danger. Like it or not we cannot stay encapsulated in our vehicles. We get in and out from our homes. We must walk through parking lots. We may even enjoy a stroll, if just around our quiet suburban neighborhood. Perhaps we even moved there so that our kids could have a yard to play in. But it turns out these are actually the most dangerous places to be, especially for children.
Even though speeds are low, drivers are more likely to be distracted in parking lots. We may think that our kids are safest playing in our suburban neighborhoods, but this is where they are most likely to be struck by vehicles. In fact, it is where 70% of injuries or deaths of children caused by auto collisions occur. Deaths that are made more likely by the increased hood heights, weights, and blind spots of giant SUVs.
Worst of all, Barrett and Jarimiah have made it more likely that they will be the ones to kill their own children by purchasing large SUVs. As cars have gotten larger, frontovers and backovers have gotten more common. Frontover accidents alone are the leading cause of automobile related deaths for children, about 30% of all children killed under the age of 14. I cannot personally imagine what it would be like to be responsible for the death of my own child. Much less if it was because of a vehicle I had expressly purchased to keep them safe.
That's why I get a little frustrated seeing so many people mock or belittle the people behind these tweets. We are in a vehicular arms race. It isn’t caused by the cruelty and malicious intent of the people driving these large vehicles. I know some of that does exist (I mean, I live in Albuquerque. I’ve seen the lifted trucks driving around), but that isn’t what causes this problem. Though not to the same extent, even the drivers of these massive vehicles are victims of the arms race because it reduces safety for *everyone*.
The cause of the arms race is systemic. Each SUV driver is making a rational choice to keep their family safe. No one wants to be the one in the compact car that gets crushed under the lifted F-150. But the positive feedback of retaliation ensures that, even though all the actors may be behaving rationally, the outcome is irrational. Though all actors may be trying to maximize safety, the end result is everyone is less safe, and some more so than others. That is what is so insidious about arms races.
Worse, the vehicular arms race is also emergent. It isn’t the result of two competing nations, but of millions of people all making their own choices about how they get around. We cannot sign a treaty to de-escalate. We will not be able to talk or reason our way out of this arms race. The only option going forward is to undo the incentives which cause people to choose larger and larger vehicles. We must create the negative feedback to counteract the existing positive feedback loops and thus create a safer equilibrium.
This is an arms race, we have to understand how an arms race works in order to get out of it. We can’t sign a treaty, so we have to undo the incentives. Do we want to endlessly piss and moan or solve it? If we make it into a culture war the policies will be harder to implement. Because these aren’t ignorant or irrational people, quite the opposite.
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