Environmental Research - Calculating the real carbon footprint of vehicles

Environmental Research Web recently posted “Calculating the real carbon footprint of vehicles“, an article by Mikhail V Chester and Arpad Horvath of the Department of Civil and Environmental Engineering, University of California, which looks at the environmental impact of various forms of transportation (Planes, Trains, Buses and Automobiles) over their entire lifetime, to determine overall greenhouse gasses and energy used. The study includes vehicle manufacture, infrastructure, fuel, delivery of fuel and operation of the vehicle.

The energy usage numbers were simplified into MJ/PKT, mega-joules per passenger-kilometer-traveled. When looked at this way, many passengers riding a single vehicle, even if relatively inefficient, actually use less fuel each. 2 people riding an SUV (.9 MJ/PKT) can use less energy, per passenger, than 5 riders in a standard city bus (4 MJ/PKT); however, the numbers change once the bus is full (.5 MJ/PKT). Large Jet aircraft (1.4 MJ/PKT) compare quite favorably, simply because of how many passengers they can carry.