The New Year brings a number of news reports fretting (or hoping) that the amount of travel we do has peaked or plateaued. Given that cars are becoming more fuel-efficient, that means that the total amount of energy we use driving will significantly decline. However, the real implications of the claim are far more dire.
The news reports are actually based on a paper published by researchers at Stanford University more than a year ago. The researchers followed the time-honored technique of looking at past data trends, drawing a dotted line into the future, and claiming it as a prediction. Reality is somewhat more complicated.
A much more interesting report, published more than a decade ago by the Minnesota Department of Transportation, compared population and job densities with travel behavior in 31 cities. “Land use, at least at the aggregate level studied here, is not a major leverage point in the determination of overall population travel choices,” the study found. “On the one hand, certain relationships emerge which correspond to generally held beliefs, for example that high residential concentration increases transit share,” though it did not reduce driving or congestion. “On the other hand, aggregate land use characteristics had little or no discernable impact on other measures of travel behavior.”
“Much policy seems to be based on the belief that relatively small changes to land use will have a big impact on travel choices,” the study concluded. “The findings here imply just the opposite; that even very big, widespread differences in land use have very little impact on travel behavior, in good ways or in bad.”
While that conclusion supports the Antiplanner’s beliefs, I want to point to an intermediate step in the study. “There are two important competing theories of the link between travel behavior and land use,” the author notes. The “travel minimization” theory assumes that people want to avoid travel if they can. The “time budget” theory, on the other hand, says that people will devote so much time–both a maximum and a minimum amount of time–to travel each day.
If you believe the travel minimization theory, then you might agree that packing more land uses into a given amount of land will allow people to travel less. The time budget theory, however, suggests that people are going to spend time traveling every day irrespective of land uses. While the Minnesota paper does not firmly conclude that either theory is perfect, it does find that “The evidence comes down pretty strongly on the side of travel time budgets.”
If the time budget theory is right, then travel increases mainly by increasing average travel speeds. Conversely, we reach peak travel only if average speeds stop increasing. This seems to be the case. “My basic thesis is, ‘There ain’t room on the road,’” says the author of the peak-travel paper. In other words, travel has peaked because congestion has slowed people down, and they can’t travel more without exceeding their time budgets.
Rather than cheering this result, transportation planners should do everything they can to make sure peak travel doesn’t happen anytime soon. Increased travel speeds in the 20th century led to unprecedented increases in productivity, incomes, and personal freedom. Stagnant travel speeds will lead to a stagnant economy and a stagnant society.
Instead of building streetcars, light rail, and other archaic and slow substitutes for driving on congested highways, planners should work to reduce that congestion. One way is to remove bottlenecks; another is to use congestion pricing, which actually increases the capacity of roads to move travel during rush-hour periods. Driverless cars will be a longer-run solution that could lead to a huge increase in travel and all the benefits it provides.