The Momentum Externality

Pounds that Kill: The External Costs of Vehicle Weight 
Michael Anderson, Maximilian Auffhammer 
NBER Working Paper No. 17170 



  1. There's another policy prescription. One could also change the material used to build cars or increase the extent of the "crumble" zone. Part of what makes a bike helmet effective is that it absorbs a large chunk of the impact, collapsing inward upon contact so that your head is protected. Cars do have that today, but I suspect it could be improved to lessen this externality. We could also build cars out of sponges.

  2. How does risk homeostasis play into all of this?

  3. I didn't know what "risk homeostasis" was, but if this is what you meant: http://en.wikipedia.org/wiki/Risk_homeostasis
    Then I would say it might be something to think about in policy design. I don't love that model, I think it's a kind of simplistic way to think about how individuals cope with risk. But economic theory would predict that if individuals are more protected from some type of risk, they might be more willing to take on additional risks elsewhere. If the govt began taxing automobile mass, then perhaps drivers would drive faster. But we already punish people for driving too fast, so perhaps limiting mass would be effective.

  4. "Heavier vehicles are safer for their own occupants but more hazardous for the occupants of other vehicles." That makes a lot of sense. That, it seems, is a reason why these vehicles are taxed more.