The local Whole Paycheck Foods has a section marked as "Fuel Efficient Vehicles Only". I am under the impression that they are referring to hybrids, diesels and electric cars. Of course the painted markings don't keep my ≈26MPG Miata out.
After all, it's far-more green to properly maintain and keep a twenty year-old car running than it is to consume the materials needed to build a new car. Plus, relative to the van, the Miata goes 60% farther on each gallon of fuel.