Car safety choices

I’ve just read a great post about vehicle size and the probability of getting killed, go The Economist.  It says that, although you are less likely to die if you are in an accident and you are in an SUV, you are more likely to be in an accident if you are in an SUV, and therefore we can’t just say that having a bigger car will make us safer.  Now the reason I think SUV’s get into more accidents is that people feel safer in SUV’s and so drive more aggressively.

Let us now completely ignore this point and look at a slightly different issue.  Say you were certain that at some point you were going to be in an accident.  In this case, all other things equal, you want to choose a car that gives you a greater probability of living.  As a result, you choose an SUV.  Furthermore, if everyone in society felt the same sort of way, they would buy SUV’s as well.

However, your probability of living also depends on the type of car the person you crash into is driving.  If you have an SUV and they have a Honda Civic, you will destroy them, your probability of living will be high and they will be in trouble.  If they also have an SUV, then you are both likely to get munched as you both have big cars.  Now what happens in the hypothetical case when you and the other person have Honda Civics?  You will be worse off than if you were in an SUV, but you will be better off than if they were in an SUV.  The interesting question is, how does this compare to the case when you are both driving SUV’s?

If the probability of living is higher when you are both driving Honda Civics than in the case when you are both driving SUV’s we have a prisoner’s dilemma.  Both you and the other crash victim would be better off if you were both in Honda Civics than if you were both in SUV’s.  However, incentives convince the individual to buy an SUV.

If the probability of dieing in a Civic vs Civic crash are lower than an SUV vs SUV crash, then we have another reason (beyond the moral hazard aggressive driving reason and the environmental reason) for why the government should regulate the size of vehicles it imports.

  • Kimble

    How would that look for the government? Forcing people to buy smaller cars KNOWING that it poses a greater risk because of the other SUVs already on the road.

  • Matt Nolan

    I agree, it is also quite a restriction on people liberty’s. But if it will save lives, the government might be sellable 😉

  • rauparaha

    I don’t see why we have to ban SUVs. As harsh as it may sound, this is an externality effect of owning an SUV: maybe licensing fees or petrol taxes could make it more expensive to own an SUV. I’ve no idea what the social cost of owning an SUV is, but I don’t imagine it is astronomical. Wouldn’t banning them be a gross overreaction? After all, there are people (eg. farmers) who might find it immensely practical to own one. The cost of enforcing some scheme by which you apply for a license to own a large vehicle may well be greater than the benefit of reducing the number of SUVs on the road.

  • Matt Nolan

    I agree that banning is a huge over-reaction, and since SUV’s consume more fuel than Civics we could include it in an externality tax. Or even more directly, a registration fee based on the safety risk of the car. Two things I appeal to in defense are:

    1) Ceteris Paribus, I was assuming that all other things about everything in the world were constant and only the safety effect mattered (thats what I was doing when I said “in this case, all other things equal”).

    2) My prescriptive statement (the last paragraph) was a throw away line, I do not actually endorse that regulation, I just had to write something to close up the article.

    I’ll admit it, I just really wanted to talk about a prisoners dilemma 😉 .

  • The risks are in fact not greater for smaller cars. The risks, if you get in an accident are, but you are less likely to be in the accident in the smaller car. Aggressive driving may play a role in the increased risks of driving a large SUV to your safety, but I have always thought the main reason was that big SUVs are less able to maneuver to avoid accidents (and people do a very poor job of compensating – by doing the opposite of aggressive driving – which is the proper strategy if you chose a risky vehicle and want to avoid the consequences of accidents).

    I think a significant part of the dilemma is that people falsely believe that large SUVs are safer. Based on this false believe they buy them and make everyone less safe (including themselves). This is not the only reason people buy large SUVs so large SUVs would not be eliminated if people could just understand the fact they were increasing risk to themselves and their family by driving large SUVs.