US Environmental Protection Agency (EPA) and the National Highway Traffic Safety Administration (NHTSA) proposed new fuel economy labels for cars and light-trucks coming to showrooms.

The new labels for fuel efficiency come on the heels of recently improved standards for fuel economy and global warming pollution finalized last April. The standards, which phase in during model years 2012 to 2016, increase the average fuel economy of new vehicles to 34.1 miles per gallon and hold emissions of greenhouse gases to no more than 250 grams of CO2 per mile starting the mandate from 2012.

EPA and NHTSA have proposed two label designs. The new labels also introduce greenhouse gas emissions rates (in gCO2/mile) and a fuel consumption rate (gallons/100 mi) along with traditional miles per gallon metric and an estimated annual fuel cost. The fuel consumption metric is helpful because it relates directly to operational costs and environmental performance. For example, when comparing two cars that differ in fuel consumption rates by 20 percent, their fuel costs and global warming emissions will also differ by 20 percent. The redesign of the fuel economy label was partly driven by the need to label emerging vehicles that run, at least partially, on electricity instead of gasoline or diesel fuel to compare the value of these new non-petroleum technologies with their conventional oil-powered counterparts.

EPA and NHTSA propose to further simplify the process of finding the cleanest, most efficient vehicles by grading all cars, minivans, SUVs and pickups with A+ (best) to D (worst) letter grades. The letters summarize the characteristics of fuel efficiency, global warming pollution and cost of operation.