Well motortrend has this real world mileage test where they hook up an complex looking device to the back of the car. Something like that surely can be employed by manufacturers, magazines, colleges, etc, and the EPA.<p>From reading the article it should not be difficult to extend the testing abilities to cover all pollutants you want to measure<p><a href="http:&#x2F;&#x2F;www.motortrend.com&#x2F;news&#x2F;real-numbers-mpg-101&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.motortrend.com&#x2F;news&#x2F;real-numbers-mpg-101&#x2F;</a>