THE BLOG
11/09/2011 08:23 am ET Updated Jan 09, 2012

Has Driving Peaked in American Cities?

Last year, people drove roughly three trillion miles, which is the third-highest total mileage figure in history. If you're planning on driving this holiday season, you'll join the flood of people who have filled streets this year.

But while vehicles in general continue to rack up mileage, some road researchers have noticed that driving in major cities has reached an unexpected plateau, a phenomenon known as "peak car use." The Brookings Institution discovered this trend a few years back. Adam Millard-Ball and Lee Schipper confirmed it earlier this year and just last month a pair of Australian scholars reported that peak car use appears to be a global trend that's here to stay.

In the June issue of the journal "World Transport, Policy & Practice," Peter Newman and Jeff Kenworthy of the Curtin University Sustainability Policy Institute in Perth, reported that per capita vehicle kilometers traveled in several major cities around the world actually declined from 1995 to 2005. In Europe, London dropped 1.2 percent, Stockholm 3.7 and Vienna 7.6. In the United States, Atlanta fell 10.1 percent and Houston 15.2. Even Los Angeles fell 2 percent. The chart above shows a clear slowing of growth in car use in recent times.

The effects of this behavioral shift could change the structures of cities as we know them, according to Newman and Kenworthy.

"Peak car use suggests that we are witnessing the end of building cities around cars at least in the developed world," they write. The duo then offer six reasons why peak car use is occurring now, and why you should plan on leaving your car at home if you're heading to a major US city this holiday season:

1. Hitting the Marchetti Wall: The Marchetti "wall" or "constant" says that people don't like to take more than an hour out of their day for travel time. Once a city is an "hour-wide," its growth hits a wall.

2. The Growth of Public Transport: Once such a wall is reached by car use, write Newman and Kenworthy, much of the travel burden shifts to public transit. The growth of transit has an "exponential" impact on driving known as the "transit leverage" effect, they write. In other words, "even small increases in transit can begin to put a large dent in car use growth and eventually will cause it to peak and decline."

3. The Reversal of Urban Sprawl: Readers of this space are certainly familiar with the country's shifting population trends -- particularly the growing popularity of "walkable cities." Newman and Kenworthy point out that a rise in urban density typically acts as a "multiplier on the use of transit and walking/cycling."

4. The Aging of Cities: In their weakest point, the authors write that people in cities are getting older, and that older people tend to drive less. They probably missed a chance here to note an even more intriguing age-related trend: that the digital age may be diminishing people's desire to drive.

5. The Growth of a Culture of Urbanism: Essentially 3b.

6. The Rise in Fuel Prices: The logic here is that high gas prices have caused Americans either to drive less or to use other transport modes more (though, relatively speaking, US gas prices are actually pretty low). In reporting on Newman and Kenworthy's work, Streetsblog DC points out the strong correlation between economic downturns and driving decline.

Newman and Kenworthy close their report by telling regional planners to take note. In a recent feature, Fast Company took them at their word:

If all of these factors actually do cause a dramatic decline in car usage, city planners will have to think more about factoring light rail, buses, cycling, and walking routes into their plans.

But one might also argue that a balanced system of light rail, buses and bike lanes is exactly what good city planners think about, especially when they consider how to grow tourism in their area. It's actually the public officials with the power to fund such thoughts who should factor research like the present study into their plans.