| Vol. 8 | No. 2 | Spring 2006 |
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Dialogue
I’ve seen several different rating systems for vehicle emissions. How do they compare? |
The federal government's regulatory system for rating smog-forming emissions (such as nitrogen oxides and carbon monoxide) is known as Tier 2. Vehicles are categorized in "bins" ranging from 1 (best) to 10 (worst) depending on their emission performance.
A number of West Coast and Northeast states, however, have adopted California's more stringent LEV II standards, which place vehicles into four categories: zero emissions (ZEV), super ultra-low emissions (SULEV), ultra-low emissions (ULEV), and low emissions (LEV). The best category, ZEV, is roughly equivalent to the federal Bin 1, while LEV is equivalent to Bin 9.
The Environmental Protection Agency (EPA) also has a system for rating vehicle emissions, but its "air pollution score" works on a scale of 10 being best and 1 being worst. Consumers could therefore be confused by the fact that an EPA score of 1 is equivalent to Bin 10.
To see how these different ratings apply to hybrid vehicles, visit our Hybrid Center website at www.hybridcenter.org. For other vehicles, visit the Department of Transportation's website.
Also in this issue of Earthwise:
Close to Home
A Cleaner Water Heater
