Why should miles be the denominator? What if Americans just drive around pointlessly because their built environment requires it? Does that lower the impact o

Why should miles be the denominator? What if Americans just drive around pointlessly because their built environment requires it? Does that lower the impact of traffic deaths? Urban form and the external cost of transportation are inextricably linked. You can't say that of course it's safer in Sweden because they drive less, because it's safer in Sweden _because_ they drive less! That's the point!