The product planning decisions of a handful of powerful companies have an immense influence on the environmental health of the United States and the world.

Automaker Rankings 2007: The Environmental Performance of Car Companies analyzes the bottom-line environmental performance of eight companies, which together account for 96 percent of cars and trucks sold in the United States—the world’s largest vehicle market.

The analysis uses sales and emissions data from the U.S. Environmental Protection Agency and Department of Transportation for model year 2005. Overall scores are based on a 50/50 weighting of average per-mile emissions of smog-forming and global warming pollutants from each manufacturer’s vehicles.

The average across all eight automakers is defined as a score of 100 and lower scores indicate less pollution. Even the leaders in these rankings should be doing more, especially when it comes to global warming.

Conventional technologies can cut global warming emissions by 40 percent; hybrids can reduce emissions even further. The next time you purchase a car or truck, choose one with the lowest emissions and highest fuel economy that meets your needs and budget. Automakers need a strong signal that consumers care about the environmental impact of their vehicle choices. When all else is equal, use these rankings to reward the best overall automaker.

Honda retains its title as the Greenest Automaker. Honda has the best smog performance in four out of the five classes of vehicles it produced, and better-than-average global warming scores in every class.