If you traveled by air over the holidays, you may have landed with a bit of green guilt. Conventional wisdom says that driving a relatively fuel-efficient car is usually better for the environment than flying.
That may no longer be the case, though, according to new calculations from the University of Michigan’s Transportation Research Institute.
Over the last four decades, driving has steadily lost the fuel-efficiency edge it once held over flying. In 1970, the per-passenger-mile fuel intensity for flying was twice that of an average car trip.
“That is no longer the case for the average vehicle,” says Michael Sivak, director of Michigan’s sustainable transportation program, which produces a monthly “eco-driving” index of greenhouse emissions from U.S. drivers.
In fact, matching the fuel intensity of an average flight now requires a car get at least 33.8 mpg or have more than two occupants, according to Sivak’s latest paper, “Making Driving Less Energy Intensive Than Flying.”
Since 1970, the fuel intensity of both driving and flying have decreased, but air travel has seen far greater efficiency gains — a 74 percent decrease in BTUs per pa... Read more