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For energy efficiency, planes beat new cars

By Michael Sugerman, Daily Staff Reporter
Published January 13, 2014

Could a 12,000 pound airplane be more fuel efficient than a car?

It may sound unlikely, but according to a report by Michael Sivak, a research professor at the University's Transportation Research Institute, on a per capita basis airplanes are more environmentally friendly than cars.

The report compared levels of fuel consumption for a given mileage for a light-duty vehicle versus a commercial airline flight.

Results were evaluated by British thermal unit — a unit of energy output — per person per mile. The domestic operations of all certified air carriers were considered to calculate the average energy intensity of airplanes, whereas all “light-duty” vehicles — cars, SUVs, pickups and vans — were considered to calculate that of cars.

Sivak observed that between 1970 and 2010, air carriers collectively reduced their energy intensities by 74 percent, whereas the improvement for driving was only a 17 percent bump. In 2010, the energy used for driving surpassed that of flying by 57 percent.

Sivak also addressed electric cars in his report, adding that their limited prolificacy — less than 1 percent of all vehicles on the road — made them unnecessary to include in his calculation of light-duty vehicle energy output.

He also wrote that without any improvement in fuel economy, an increase in average vehicle load from 1.38 to 2.3 persons would match the energy intensity of driving and flying.

“The fuel economy of the entire fleet of light-duty vehicles would have to improve from the current 21.5 miles per gallon to at least 33.8 miles per gallon,” Sivak wrote.

However, neither of these changes will be easy to implement. Even as new technology yields better fuel economy for light-duty vehicles, their introduction into the current fleet of cars in use will have a marginal effect on the total energy intensity produced by driving.

However, the number of passengers on an average trip has decreased in recent years — increasing the per capita energy intensity of each trip. The downward trend in vehicle load means the 67 percent load increase needed to reduce energy intensity may not be a realistic expectation.

“It is important to recognize that the energy intensity of flying will continue to improve,” Sivak said. “Consequently, because the future energy intensity of flying will be better than it currently is, the (suggested) improvements … underestimate the improvements that need to be achieved for driving to be less energy intensive than flying.”


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