Externalities, SUVs and Driving with Your Brights On

My physics sucks. I don’t remember much from high school or college, and its not like I use it on a regular basis. But as I recall, almost everything in classical mechanics can be derived from F = ma. (Force = mass times acceleration.)

Consider two accidents. In Accident A, 2 battleships collide, where each is going about 10 mph (yeah, I know, they don’t measure ship speed in mph, but how many of us at this blog know what knots are?). In Accident B, 2 subcompacts, each going at the other at 10 mph collide. If I understand the F= ma formula, it means that all else equal, you should prefer to be in one of the subcompacts than in one the battleships, because the “m” in accident B is so much less than the “m” in accident A, which means the “F” you face in accident A is going to be so much larger.

Now let me meander a bit more. Close to where I live, there is a big road that runs from North to South (and of course, from South to North in the other direction). There are protected left hand turn lanes facing each other. Thus, a car going North that wants to turn left, and a car going South that wants to turn left will each enter the protected turn lane, and face each other across the intersection.

Now, something I’ve noticed. It often happens that if the first car in one of the protected lanes is an SUV, cars in the other protected lane will net turn, even if there are no other cars on the road in the direction the SUV came from. This is especially with large SUVs – Hummers, Excursions, Yukons, etc. Having been in that position myself, I can state categorically, the reason is that you cannot see around the SUV.

SUVs are also hard to see around in other situations, and that forces other drivers to change their driving patterns, slowing down traffic. They also slow down traffic in another way – they have a larger footprint, reducing the number of vehicles that can occupy the same amount of limited road space. I would guess if the data were available, one could show that congestion gets worse faster when there are a lot of SUVs on the road. Put another way, the SUV driver is imposing externalities on the drivers of other vehicles.

Now, it seems we cannot prevent people from SUVs. After all, Americans have rights, and that includes the right of inconveniencing others. But do they always? An example where people’s rights are limited is that one is not normally allowed to drive with one’s bright lights on.

There are many similarities between driving with one’s bright lights on and driving an SUV. In both cases, all else being the same, the driver is made safer because visibility is improved. In both cases, the increased safety comes at the cost of the safety of others; those facing oncoming bright lights or anywhere on the road with an SUV have less visibility themselves. Furthermore, the benefits of either disappear when enough other people do the same. (Decreased visibility, and in the case of two SUVs crashing, well, there’s F= ma.)

I would guess that that driving with one’s bright lights on is illegal, and driving a Hummer is not, is precisely because it is possible for everyone to drive with their bright lights on. Heck, even a driver of very modest means can strap a searchlight to the roof of their vehicle if they’d like. On the other hand, I believe a Hummer costs about $100K.

Is there any other reason? Am I missing something? And one other question… I’ve heard libertarians argue that there’s nothing wrong with driving an SUV. Would a libertarian argue the same about driving with a very large laser pointer on one’s hood, and if not, why not?