True, but not only that - those diesel emissions are much more toxic than gasoline exhaust fumes. Three known carcinogens and more than 40 harmful toxins in diesel fumes.

And by the way: is the practice of 18 wheeler drivers just leaving their truck running all the dang time still a valid method of operation in today's world, where helping the environment and trying to clean the air is not just "hip" but is the means to avoid future catastrophe to the Earth?

(OK, I'm off the soapbox for now, but that stuff really peeves me !! )