The Obama Administration proposed this week 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 be 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, administrator of the National Highway Traffic Safety Administration.
He said the alternative labels also would include a code that, when read by a cell phone, would deliver further information about the vehicle.
The 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. A 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.
Dave McCurdy, chief executive of the Alliance of Automobile Manufacturers, an industry group, said the rating system "falls short because it is imbued with school-yard memories of passing and failing."
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: "Overall it's a B."
Mr. Becker said he questioned whether battery-powered cars qualified as "zero emissions."
He said the sticker for electric cars should also take note of pollutants emitted by power plants when they produce the electricity that charges the cars.