U.S. Fuel Consumption Outpaces Efficiency Gains

The fuel economy of light vehicles on U.S. roads has improved 40% from 1970 to 2010. But overall fuel consumption rose faster over the same period because American drove farther and carried fewer passengers, according to an analysis by the University of Michigan Transportation Research Institute.

UMTRI researcher Michael Sivak says miles traveled during the 40 years rose 155% and vehicle load the average number of occupants per vehicle fell 27%.

Average fuel consumption for the fleet dropped 40% to 4.6 gallons per 100 miles over the four decades. But the improvement was only 17% in terms of vehicle load. And that was more than erased by the surge in miles drive.

The bottom line, UMTRI says: Overall fuel consumption in the U.S. rose 53%.

Sivak estimates that a 20% improvement in a future vehicle's fuel economy would net an 18% decline in fuel consumption because the miles traveled would grow. More important, the improvement would affect only that vehicle and not the entire fleet.

Sivak figures a 20% gain in fuel efficiency for all light vehicles sold in a given year would lower the fuel consumption average for all cars and light trucks on the road by only 1%. He also notes that higher fuel taxes would have a more immediate effect by curbing miles driven for the entire fleet.