SUVs, Bright Lights, Externalities: Angry Bear speaks

Having just lectured on "Externalities" as part of an "Environmental Economics" introduction I must say that I like this post by the Angry Bear who describes his Blog as "Slightly left of center economic commentary on news, politics, and the economy."

The 53 comments left on this thread shows it obviously touched a nerve. Interesting reading.

SUVs, Bright Lights, Externalities, take 2

I normally don’t revisit old posts, but I don’t always get my point across. I’m going to try again on the SUV externality issue, and I’m going to be more concise.

1. Being in an SUV increases the visibility of the vehicle driver
2. The presence of SUVs reduces the visibility of other vehicles on the road
3. As a result of #2, SUVs impose negative externalities (e.g., reduced safety, wasted time) on occupants of other vehicles.

Similarly,

a. Driving with one’s bright lights on increases the visibility of the vehicle driver
b. The presence of vehicles driving with their bright lights on reduces the visibility of other vehicles on the road
c. As a result of item b, vehicles with their brights on impose negative externalities (e.g., reduced safety, wasted time) on occupants of other vehicles.

I assume none of this is in dispute. So… why is driving with one’s bright lights on illegal, and driving an SUV legal?

Conjecture… the difference is that SUVs are externalities imposed by the wealthy, whereas bright lights are externalities that can be imposed by anyone. (A Hummer costs $100K, while even very poor car owners can afford to strap a searchlight to the hood of their vehicle.) Agree? Disagree? Am I missing something?