But what if that Suburban were packed to capacity, with nine people aboard? On the highway, that would translate to 189 passenger miles per gallon, which should be more than enough to shame that solo Prius driver in the HOV lane, wallowing in her own smugness. Of course, if Ms. Prius filled up her car, overall fuel efficiency would increase, too.
That got us to thinking how efficient different forms of transportation are, not just in terms of a vehicle’s mileage rating, but in terms of a per seat comparison. In other words, if you are really interested in reducing your carbon footprint, what’s the greenest way to travel?
Making Up The Rules
To keep this comparison somewhat grounded, we excused electric cars from the competition, since no national charging infrastructure yet exists. (Mileage ratings for electric cars are hardly reliable at this point, anyway.) We also decided to try and show each form of transportation under ideal conditions. This means with a full passenger load and smooth traveling conditions, free of any weather problems, traffic delays, or other interruptions. Our comparison also doesn’t take into account a traveler’s time.