This report analyzes recent trends in the amount of energy needed to transport a person in the U.S. a given distance either in a light-duty vehicle or on a scheduled airline flight. After observing that the energy intensity of driving (BTU per person mile) is 57% greater than that of flying, calculations were made to estimate how much improvement would need to be achieved in either vehicle fuel economy or passenger load to make driving the less energy intensive of these two modes of transportation. The main findings are that to make driving less energy intensive than flying, the fuel economy of the entire fleet of light-duty vehicles would have to improve from the current 21.5 mpg to at least 33.8 mpg, or vehicle load would have to increase from the current 1.38 persons to at least 2.3 persons. The report briefly discusses the difficulties in achieving these improvements. Furthermore, it points out that, because the future energy intensity of flying will be better than it currently is, the calculated improvements underestimate the improvements that need to be achieved for driving to be less energy intensive than flying. Finally, it is emphasized that, although flying is less energy intensive than driving, flying is a viable alternative to driving only for a subset of driving trips that involve relatively long distances. (Author/publisher)
Abstract