The Obama administration proposed on Monday two alternatives to the window stickers in new vehicles, including one that would assign letter grades for fuel economy and greenhouse gas emissions.
The letter grades—from A+ to D—were immediately denounced by some industry groups, which said the government should not be making value judgments for consumers about vehicles.
If the grading system were applied now, many 2010 vehicles could get fairly low grades because the ratings favor fuel-efficient electric and hybrid models.
The second possible window sticker would also contain information about fuel economy and emissions, but would not assign a letter grade. Both stickers offer estimates of annual fuel costs.
Either way, officials said, the new sticker would amount to the biggest change to the window labels since they were created three decades ago. The current window sticker provides fuel economy estimates for city and highway driving.
“The old labels are just not good enough anymore,” said David Strickland, the administrator of the National Highway Traffic Safety Administration.
He said the alternative labels would also include a code that, when read by a cellphone, would deliver further information about the vehicle.
The new stickers were developed by the safety agency and the Environmental Protection Agency in response to the Energy Independence and Security Act of 2007, which called on the two agencies to rate vehicles on fuel economy, greenhouse gases and smog-forming pollutants. The new label will be affixed to cars and trucks beginning in the 2012 model year.
The agencies will accept public comment for 60 days before choosing one of the two stickers.
Gina McCarthy, E.P.A. assistant administrator for air and radiation, said in a conference call that the grading system would compare cars against a full range of models, “not just S.U.V.’s against S.U.V.’s.” She said there would be no failing marks.
The highest grade, A+, with fuel economy rated as equivalent to 117 miles per gallon and up, would be reserved in a sample rating for “zero emission” electric cars. Plug-in hybrid electric cars (which get rated at the equivalent of 59 to 116 miles per gallon) would get an A grade, and some conventional hybrids, like the Toyota Prius and Ford Fusion, would get an A-. Other hybrids, like the Nissan Altima, Ford Escape and Toyota Camry, would receive B+ grades.
If the grading system existed now, under assumptions developed by the agencies, 306 small cars from model year 2010 would receive a B, only eight S.U.V.’s would receive a B+ (68 would get a C), and the highest grade for a van would be a C+, officials said.
Dave McCurdy, chief executive of the Alliance of Automobile Manufacturers, an industry group, said the rating system “falls short because it is imbued with schoolyard memories of passing and failing.”
In an e-mail, Gloria Bergquist, a vice president with the group, wrote, “Note to media: Your spokesperson tried to give the proposal a D but was told not to do so by her boss.”
Some environmental and consumer groups reacted more positively. Dan Becker, director of the Safe Climate Campaign, which is part of the Center for Auto Safety, a consumer advocacy group in Washington, said in an e-mail: “Over all it’s a B.”
Mr. Becker said he questioned whether battery cars qualified as “zero emissions.” He said that the sticker for electric cars should also take note of what are called “upstream emissions,” which are pollutants emitted by power plants when they produce the electricity that charges the cars.
Such a system would probably require dividing the United States into separate regions, because some parts of the country have higher concentrations of coal-burning plants and thus a greater upstream burden.
During the conference, Ms. McCarthy said information about those emissions would be addressed at an E.P.A. Web site, but Mr. Becker said it belonged on the label. “Anyone who buys a car will see the label, but only a few will search out information on a Web site,” he said.