July 8, 2008 - Starting January 1, 2009, California will expand its Smog Index Label for new cars to include data on greenhouse gas emissions.

The new regulation creates a simple ranking system that will help buyers know which car is the most environmentally friendly. Showroom models could start showing these labels as early as July 2008, according to the California Air Resources Board (ARB), which will administer the program.

The new label is an expansion of the state’s Smog Index label, which has been in use since 1998.

The label will provide two scores on a scale of 1-10, a Smog Score and a Global Warming Score. The average new car will score five on both scales. The higher the score the less impact the car has on the environment.

"This label will arm consumers with the information they need to choose a vehicle that saves gas, reduces greenhouse gas emissions and helps fight smog all at once," says ARB chairman Mary Nichols. "Consumer choice is an especially powerful tool in our fight against climate change."

Environmental performance data will be also be posted on ARB's DriveClean website. Search for the cleanest vehicles here.

The cleanest cars, as assessed by the state of California, are:

1. 2008 Tesla Roadster (Battery Electric)
2. 2008 GEM e2, e4, e6, eL, eL XD, eS
3. 2008 Toyota Prius (Hybrid)
4. 2008 Honda Civic GX (CNG)
5. 2008 Honda Civic (Hybrid)
6. 2008 Nissan Altima (Hybrid)
7. 2008 Ford Escape (Hybrid)
8. 2008 Mazda tribute (Hybrid)
9. 2008 Mercury Mariner (Hybrid)