On the government website, fueleconomy.gov, the smart is listed in a category of coupe and not small car? The other small cars, are the honda civic, civic prius, honda fit, etc. I GUESS the car DOES have 2 doors and not four, but the smart would be the #2 best mileage car, lowest carbon footprint in that category, and not #1 in the coupe category. OF COURSE it is going to be the #1 in the coupe category.
The other thing is, that the smart has the lowest carbon footprint of any combustion only vehicles. I think that is something special. At least 10% lower than the next place car, and just 10% worse then a hybrid.
Go figure