In the United States, the Environmental Protection Agency (EPA) sets and regulates air pollution standards, including the implementation of a ratings system for all consumer vehicles. Now here's where it gets a bit technical, so fasten your jargon belt.
When a mechanic tests your car for air pollution, he'll be looking for several major pollutants in its exhaust, including nitrogen oxide (N20), which helps form smog when combined with hydrocarbons in the atmosphere; carbon monoxide (CO), which can be lethal; and formaldehyde (HCHO). The ratings also check for non-methane organic gases (NMOG), non-methane hydrocarbons (NMHC), and total hydrocarbons (THC), which are all carbon-containing compounds. Finally, the ratings measure particulate matter (PM), which is the black, sooty stuff that belches forth from tailpipes and settles in people's lungs.
To find out how your specific vehicle scores, or if you're shopping and want to see how a certain car would fare, take a look at the EPA's Green Vehicle Guide online. You'll also find information on vehicle greenhouse gas scores. These scores rank vehicles by the amount of carbon dioxide and other heat-trapping gases they emit (10 is the best possible score, meaning your car emits no pollutants at all).
Scientists believe that greenhouse gases are responsible for global warming. Knowing your car's greenhouse gas score, as well as its air pollution score, and choosing to drive cars that score high on both indexes are three very important tenets of the green driving movement.
Also, make sure that you don't forget your car's mileage. The higher the car's fuel efficiency, the fewer total pollutants and greenhouse emissions it will put out. The EPA also maintains a storehouse of online data about the fuel consumption of different models at fueleconomy.gov.
Now that you know what these scores mean, you can use them to help you or someone you know decide on his or her next vehicle -- with eco-friendly driving in mind. If you're looking for additional insight on fuel efficiency and green driving, take a look at the links on the next page.