A report in the NYT says that
while driving smaller and lighter cars saves fuel, “downsizing and down-weighting is also associated with an increase in deaths on the highway,” said Adrian Lund, the institute’s president.
“It’s a big effect — it’s not small,” he said
The test done was to crash a little car into a big car and see how the little car did. The answer, unsurprisingly, was badly. A little car is more fuel efficient than a big car so it’s better for the planet to drive one, and better for your wallet if carbon pricing ever happens. So the lesson I take from this test is that big cars are bad for the environment AND cause lots of deaths on the highway by crushing smaller cars in crashes.
Of course, individually it’s best to drive the big car, so an equilibrium is for everyone to drive big cars. Carbon pricing would do something about that, but it wouldn’t take into account the cost of the people killed. Should there be differences in road licencing charges between big and small cars to take account of that? I can’t really think of another mechanism by which the cost in lives is internalised. Lawsuits against people for driving big cars aren’t likely to succeed, and nobody’s going to get prosecuted for it if they kill a person.