Counting calories on the road

People seem innately programmed to devote a fixed amount of metabolic energy–an average of 240 calories, or the energy in a hot dog–to traveling around each day, according to an analysis of the habits of thousands of people in England. That’s about a tenth of a person’s total daily energy outlay, the analysts say.

The finding may give transportation planners a new tool for predicting travel behavior, such as how much bike riding a person might do after his or her bus commute from work, says civil engineer Robert Kölbl of the University of Technology Vienna in Austria. He and physicist Dirk Helbing of the Dresden University of Technology in Germany present their analysis in the on-line New Journal of Physics.

In the past, researchers have found that the average time people spend traveling each day remains roughly constant. For example, if their commute time to work decreases, they travel more in their off hours.

Based on data on British travelers from 1972 to 1998, Kölbl and Helbing find that average daily travel time actually does vary for users of different transportation modes–say walking versus driving. Even so, the travelers’ average daily metabolic expenditures in terms of calories are the same, the researchers say. An important implication, says Kölbl, is that making travel faster and easier–and therefore less calorie-intensive–won’t reduce the overall amount of traveling people do.


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