Responding to Cox and Poole, Part 1: Nothing to See Here?

Sure, a six decade-long trend of ever-increasing driving has shifted to a prolonged period of stagnation. But it’s long been understood that growth in driving per-capita was slowing and would continue to slow in the decades to come. So what’s the big deal?


We’ve been waiting for the pushback from the all-highways-all-the-time crowd to our May report on the policy implications of changing driving trends, A New Direction. And sure enough, it has arrived, in the form of a blog post from Wendell Cox and two articles from the Reason Foundation’s Robert Poole.

It’s going to take a few posts to respond to their arguments, but it’s important to do so in detail, since Cox and Poole hurl a lot of facts and pseudo-facts at our hypothesis and it’s going to take some work to clear away the fog and see the issue clear.

(If you’re looking for a quick summary of their apparent take on things, though, you can catch the gist of their argument in this brief video right here.)

The strange thing about Cox and Poole’s approach to the issue of changing driving trends is that, on some level, they just don’t seem to get what all the fuss is about. Sure, a six decade-long trend of ever-increasing driving has shifted to a prolonged period of stagnation. But it’s long been understood, they remind us, that growth in driving per-capita was slowing and would continue to slow in the decades to come. So what’s the big deal?

The idea that the rapid increase in demand for driving couldn’t go on forever has indeed been with us for a long time. As British transportation expert Phil Goodwin explains in his marvelous paper for the recent International Transportation Forum roundtable on long-term travel demand, academics have been trying to locate the point of saturation in demand for vehicle travel since at least the 1950s. In the United States, Charles Lave, Steven Polzin and others started pointing to slowing vehicle-miles traveled (VMT) growth rates in the early 1990s (a good initial summary of that research can be found here). And Cox shouts out a 1999 paper (PDF) from commuting guru Alan Pisarski that he claims makes this case as well.

Robert Poole uses this history to suggest that the data in our report showing declining vehicle travel are “nothing new.”

There are two important points, however, that Poole glides by. The first is that there is an important distinction between slowing growth in per-capita driving and the decline in per-capita driving the United States has experienced since 2004. The former represents a paler version of past trends – a situation in which the main cause of increased driving may be population growth, but driving is still increasing, albeit more slowly. The latter, however, represents a complete break with the past – a situation in which the total number of miles driven is not increasing at all.

Americans are currently driving in total about as much as we did in 2004, despite population growth of about 7 percent during that period. The implications for transportation planning of a prolonged period of stagnation in driving are profound. Think for a moment of all the new highway capacity we wouldn’t need, all the extra congestion we wouldn’t face, if that trend continues and people are driving as many miles on our roads in 2020 as they do today. 

The second point Poole evades is that, even if it has been well known among transportation experts that vehicle travel would someday hit a saturation point, that knowledge has had next to zero influence to date on public policy.

The evidence is piling up from around the country that transportation planners and public officials have erred badly in their forecasts of future driving over the last decade. We cite several examples in our report, but there are others, such as a welter of failed traffic forecasts for recent toll roads, the examples of traffic overestimation we highlighted in our recent report in Wisconsin, and the many examples Clark Williams-Derry at the Sightline Institute has documented in the Pacific Northwest.

Despite those experiences, our current transportation policy remains irrationally geared toward the construction of new or expanded highways (even amidst evidence that the congestion these projects are intended to relieve is on the decline) and assumes the continuation of sufficient revenue from the gas tax to pay for it all.

The question we wrestled with in our report is whether the peak in per-capita VMT that Poole implies is a theoretical necessity may have already occurred. If it has occurred, then, as we argue in the report, all recent forecasts of vehicle travel growth need to be revised, and so too do our priorities for how we invest transportation dollars in the future.

Poole doesn’t address that question in his critique, nor does he deal at all with the policy implications of the slowing growth in per-capita VMT he acknowledges as a reality. He and Cox do have a lot to say, however, about media coverage of the Millennial generation’s changing transportation habits and dramatic decline in driving in the past decade.

We’ll address that part of their argument in our next post.


Tony Dutzik

Associate Director and Senior Policy Analyst, Frontier Group

Tony Dutzik is associate director and senior policy analyst with Frontier Group. His research and ideas on climate, energy and transportation policy have helped shape public policy debates across the U.S., and have earned coverage in media outlets from the New York Times to National Public Radio. A former journalist, Tony lives and works in Boston.