Rating vehicles on a scale of 1 to 10, the new labels will take into account the particulate and greenhouse gas emissions and assign a corresponding score, to be displayed on the window. The higher the number, the better, with the cleanest vehicles on the road rating a 10. The state will also launch a website called DriveClean to help educate buyers about emissions levels for various cars.

A slogan on the label urges drivers to: "Protect the environment, choose vehicles with higher scores." The labels are part of the CARB (California Air Resources Board) plan to cut emissions by as much as 30% if it can achieve EPA (Environment Protection Agency) approval for the plan. All new cars sold in the state will be required to display the stickers by January 1, 2009, reports The Detroit News.

California's requirement mirrors a plan the EPA has adopted subject to legislation passed by Congress in December of last year. A completely voluntary program, the EPA's information includes greenhouse gas emissions, fuel efficiency and whether a vehicles dual-fuel or alternative-fuel capable.

The new emissions-labeling plan supplements the sweeping emissions reductions plan announced last week. An emissions trading program, a focus on renewable energy sources like wind and solar and more mass-transit and pedestrian-friendly city designs are all on the table as ways to cut back pollutant levels.