If your idea of a car is something bigger than a penalty box, or more powerful than a moped, or maybe slightly fun to drive, then I suggest you get yourself down to your local dealer (assuming he hasn’t already folded), pronto, and buy yourself something pretty. It might just be your last chance for a good long while.

President Obama put his signature to new CAFE rules last week, requiring that by 2016, automakers must meet fleet-wide gas mileage averages of 39 mpg for cars and 30 for trucks. This is easy enough to accomplish — build smaller vehicles with smaller engines. Although I can tell you how well that’s going to go over here in Colorado, where getting trapped behind a Prius (or an Aveo or any other wind-up toy car) on a steep incline means growing a full beard before cresting the hill.

Now imagine a Ford F-150 trying to make it up to the Eisenhower Tunnel with a full load of construction equipment and a two-liter four-banger under the hood. You’ll have facial growth like one of the ZZ Top guys before it’s all over, maybe even if you’re a girl.

If you think I’m exaggerating, think again. The anonymous “Mechanic,” writing for Edmunds, worries that the new CAFE standards

won’t save much fuel and won’t save the planet, but they will crush the life out of the car business. From here on out, cars are going to shrink in size, shrivel in power and grow more expensive.

With a goal of a corporate fleet average of 39 mpg for cars by 2016 model year it’s not just V8s that are dead, but V6s and decent-size fours. Of course all the SUVs and the Camaro, Mustang and Corvette as we know them are doomed, that’s obvious, but so are reasonably size minivans, midsize sedans like the Accord and Camry, and anything fun.

And if you have even any small interest in seeing what’s left of Detroit survive, now would be a good time to look on Obama’s works, ye mighty, and despair. Chrysler’s plan is to somehow, someday import FIAT’s small cars. GM has never competed well in the small-car segment, and Ford can’t even sell its well-regarded “Euro Focus” domestically at a profit.