Indexing Auto Effects on the Environment

Gary S. Vasilash

The air is getting better.

So indicates a new index developed at the University of Michigan Transportation Research Institute (UMTRI), which looks at the exhaust emissions created by drivers of newly purchased vehicles since October 2007 (the nominal start of the ’08 model year). It’s called the “Eco-Driving Index” (EDI).

According to Michael Sivak, a research professor at UMTRI, the environmental impact of internal combustion engines—as in CO2, other gases, and particulates—is dependent on the amount of fuel used. “The EDI estimates this amount by taking into account two primary variables—the fuel economy of the vehicle and the distance driven.”


They calculate the fuel used per driving distance (EDIf) based on monthly sales figures for models and the EPA fuel economy ratings for those models. They also calculate the distance driven per individual (EDId), based on information provided by the Federal Highway Administration. (There are other factors deployed, as well, such as days of the month, the tendency for drivers to drive more when their fuel economy improves, and number of drivers per vehicle.)

Taking all of that into account they create the EDI, which is down 14% since late 2007.

So if you’re interested in cleaner air, perhaps you should go buy a new car.