During the “great recession” when oil prices dipped, fuel efficiency took a backseat to other issues. But due to the improving economy and chaos in the Middle East, the price of oil is quickly climbing back up. Will the summer of 2011 be a repeat of 2008? I certainly hope not, because I personally believe if that happened it could sink us into a depression.
That being said, there is one good thing (and only one) that comes about from higher fuel prices; people are refocusing on energy efficiency.
I thought this would be an appropriate time to compare the efficiency of various modes of transportation. Because not everything is powered by petroleum, for consistency all figures below are based on megajoules/MJs (physics refresher: a joule is the unit of energy used by the International Standard of Units). Data come from Wikipedia, U.S. Department of Transportation, Good.is, and my trusty calculator.
Passenger Car – 2.302 MJ per passenger-kilometer
That’s the number quoted by the U.S. Department of Transportation but it could be considered a bit misleading, because it assumes there are an average of 1.57 passengers in the car (I’m scared to ask how you put 0.57 of a person in a car!). Obviously if you’re just driving by yourself, then your energy consumption per person would be much higher.
Plane – 2.138 MJ per passenger-kilometer
That assumes an average of 96.2 passengers per aircraft. Who would have thought it would be so similar to passenger cars?!
It’s important to point out though that this figure does not mean the miles per gallon, per passenger is similar between cars and planes. For a Boeing 737 with 175 passengers, it only takes 2.4 gallons per passenger to travel 350 miles. But to make it even more confusing, remember that jet fuel is extremely high octane.
Walking – 0.33 MJ (330 kJ)
As expected, walking is an extremely energy efficient form of transportation. Wikipedia says a 140 lb person walking at 3 miles per hour uses about 330 kJ per mile. However according to Good.Is, if gas was converted to calories, walking is actually less fuel efficient than a motor coach carrying 50 people (that link will also show you hybrids, trains, cruise ships, motorcycles and more).
Bicycling – 0.18 MJ (180 kJ)
Wikipedia says bicycling is “about half the energy” of walking but didn’t break down the numbers, so I had to do quite a few calculations to come up with this! Based on a 140 lb person, indeed, the energy needed is almost exactly half that of walking. It appears this is the most energy efficient form of transportation.
Although this comparison is an interesting way of looking at energy efficiency of various modes of transportation, it is by no means an apples-to-apples comparison. I think what’s more important than the amount of energy needed, is how that energy is being created! Obviously, burning petroleum products is far worse for the environment than the energy created by our body’s metabolic process.