My own needlessly complex idea
When you register your car, you get a token identifying your vehicle. When you pull up to the fueling station, your car's efficiency (miles per gallon) is read from the token (and, of course matched against the actual car via complementary tokens) and the price per gallon set against it using a forumla where there is an inverse relationship between MPG and the price (MPG goes down, price goes up). This creates a double-whammy against owning inefficient vehicles.
It also creates a black market for counterfeit tokens.
And a whole bunch of privacy concerns, naturally.
So, let us say that if your car gets 50 miles per gallon, fuel would be $2 per gallon. Somewhere down the line is the Hummer getting 10 miles per gallon, fuel would be $4 per gallon.
(This idea is completely teh suck, but sometimes you just feel like coming up with a needlessly complex and awful idea, just for kicks. And here is K5, the cesspool into which these stupid ideas can drain. Enjoy.)
As Washington State raises it's gas tax by another 8.5c to fund a massive freeway expansion (cuckoo, cuckoo), and planned unit developments reach ever farther up into the foothills and hinterlands, these observations from friends living in Europe: In town-house villages with limited parking, it's not uncommon for several people to jointly own a single vehicle, used for moving day or trips to the country. The daily commute is handled with bicycle, or walking to the nearby high-speed train, which departs every few minutes to all over the country, and connect to ports and airports. Shopping is at the small markets on the block. (OK, OK, American taxi unions and motor vehicle manufacturers would never allow this to happen. We would all die withoutr Safeways and Albertsons.) Diesel trucks in Europe don't have smoke stacks! How? The smoke is directed down under the cab into a large particulate filter box between the wheels. Besides cleaner fuels, this eliminates soot, fine particles of carbon that help start lung cancer. No plume of smoke behind Europe tractor-trailers. (OK, OK, American teamster unions and truck manufacturers would never allow this to happen.) EU vehicles are smaller, faster diesel cars that get 55mpg after you convert from liters/kilometer. Coincidentally, Renault was considering importing these rugged, enduring, high-mileage diesels into the US, but gave up over EPA regulations and the pressure of cheap, gas-powered Asia rice rockets. (ergo, Bush's famous, "Let the markets decide.") Towards the future, windfarms are springing up all along the EU coast, 100's of propellored towers. And they're doing more, pipelining marine ports straight into RORO rail, straight into dedicated high-speed rights-of-way, getting freight from the docks into European people's hands in mere days. (OK, OK, American teamster unions and truck manufacturers would never allow this to happen.) Face it, we are doomed to yahoo cowboy trainwreck. The frontier shoot-em-up ask questions later, get off my land mentality inevitably, inevitably will bring an end to America's version of civilization. That, and the fact that we're bankrupt, and Wall Street and Capitol Hill are corruption-incarnate. We will live to see the worst excesses imaginable in our country before the next Dust Bowl arrives. That's the way it is, in America's Final Century.