It's also a good idea, because the Auto Asthma Index (AAI) calculates non-automotive factors like wind, natural emissions, geography and temperature as well as automobile emissions to give each driver an accurate measure of their emissions. The site uses "searchable data on over 10,000 models using 2.5 million records culled from California Smog Check stations. The database measures vehicle exhaust on a scale from 1 to 10, 10 being the dirtiest and the most likely to cause an asthma attack. You can search for your car or look at the best and worst by vehicle type - small car, SUV, station wagon, etc. - by model year and location. Locations figures into the calculations because of an area's unique smog composition," wrote Carrie Gouldin, who worked on the project. It should surprise absolutely no one that the most polluting car is the Hummer (GM is the Automaker with the worst score for 2001-2006 vehicles). A somewhat more surprising result is that, on average, 1993 models are sixteen times dirtier than 2000 models.
I punched in my car's details and found out that it rates a four. Also, the AAI's user interface leaves a little to be desired. I suppose I'll focus my energy on the former of those two negatives, as that's the one I can do something about.
[Source: Auto Asthma Index, tip submitted by Carrie Gouldin of the Environmental Working Group, which helped develop the AAI]