An economist at UC San Diego has made a startling finding: The peculiarly American system of having one fuel efficiency standard for cars and a different, less stringent one for SUVs and trucks is increasing highway fatalities.

The problem is that under the existing, two-tiered system, increases in fuel efficiency standards force car makers to shrink cars even faster than they shrink trucks and SUVs (which by law have to remain above a certain weight, anyway). This means a greater disparity in the size of cars and trucks/SUVs, which leads to more fatalities as giant tanks kick efficient little hatchbacks all over the road.

Indeed, economist Mark Jacobsen estimates that under the existing system, every one MPG increase in efficiency standards leads to 150 additional traffic fatalities per year. Or in other words, one additional Joplin, Missouri per year.

Jacobsen's solution is as simple as it is elegant: Mandate a single, unified fuel efficiency standard for all cars and trucks, and peg it to the average MPG of the entire U.S. fleet of vehicles. Under this standard, every one MPG increase in efficiency would lead to only 5.6 percent as many deaths as our current standard, or about eight per year. To reduce that, people might have to learn to drive without crashing into each other.

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