Moving Off the Roads: PIRG Piles Up More Evidence of Peak Traffic


As I've written, I'm proud of my home state of Maryland and its clear commitment to delivering transportation choices other than driving to its citizens, for the sake of quality of life and the environment. However, here as elsewhere I find conventional wisdom which isn't wise at all. Take, for example, a conversation at an Advisory Committee meeting for Maryland's annual "Attainment Report," which I served on in '09 and again for the upcoming '14 iteration. This report assesses attainment of a long list of performance metrics, and we debated traffic (vehicle miles of travel or VMT) trends in Maryland. I noted the recent, remarkable decline and the quick retort from a very smart official there was that the faltering economy accounted for it.

Somewhat understandable, since when examining trendlines its safest to look long-term and VMT has been on an upward slope for decades. But look more closely, as some including Alan Pisarski and Cindy Burbank have done, and you'll see that the growth rate has dropped decade-by-decade since the 1950s. So flattening or even negative projections don't seem unreasonable, despite government projections (federal and state) to the contrary.

Enter the industrious, smart Phineas Baxandall at PIRG. He has done yeoman's work in recent years digging into this trend and the reasons for it (much more than any government agency seems to have done, which is puzzling). This morning he rolled out his latest examination of it, aptly titled "Moving Off the Roads." What he has done is pretty elegant in its simplicity, namely lit up the question of the relationship between VMT and economic performance from a different angle by asking how the performance of all 50 states and DC on both fronts correlate. The skinny is that the "study finds that declining rates of driving do not correspond with how badly states suffered economically in recent years" as illustrated by some useful graphs and maps including this one:

The first thing that jumps out on this map is North Dakota. This is more evidence of the environmental downside to the oil boom in that state, with the most strikingly visible one being the wasteful flaring of gas from new wellheads as shows below at night courtesy of


All that oil has to be transported, and so do the workers and other residents of boomtowns, so an old-fashioned resource-exploitation boom explains North Dakota's spike. There are four other outiers: Louisiana (Phineas speculates this is because migration and recovery activities in the aftermath of Katrina), Alabama and Nevada. But the vast majority of states saw VMT declines in the past decade.

The report looks at various potential contributors to these state trends, including telecommuting, urbanization, employment and unemployment. These last two are, of course, most at issue if the question is whether or not the economy is what's driving traffic down. What did Phineas find? To quote:

  • Among the 23 states in which driving miles per person declined faster than the national average, only six saw unemployment increase faster than the nation as a whole.
  • Among the 10 states with the largest declines in driving per person, only two rank among the ten with the largest increases in unemployment.
  • Among the 23 states where driving declined faster than the national average, only 11 saw faster-than-average declines in the unemployed share of their working-age population.
  • Among the 10 states with the greatest reductions in the employed share of population, only two were also among the ten staets with the largest reductions of driving (Georgia and the District of Columbia).

Pretty compelling evidence that the there's more to peak driving than the economy being sluggish. As Phineas says, this is something that transportation planners and engineers should take seriously. Plans, programs, and projects need to be revisited.

Fortunately Phineas is no longer a voice in the wilderness on this. Just this month one conservative blogger writes about the folly of projecting endless traffic growth as justification for more big highways, one of the nation's largest highway-building firms advises against adding new capacity willy-nilly as in the past and a writer for Fortune magazine publishes a book quoting representatives from other big companies such as Pulte and Toll Brothers who are diversifying suburban product-lines so buyers can walk or take transit instead of drive (see an interview with the author here).

This all should good news for the transportation world, since we can't seem to muster the political will to pay for the infrastructure capacity necessary for a continued sprawl-addiction.

Another reason the time is now for government agencies -- metropolitan planning organizations, state transportation departments, and federal agencies -- to catch up with the growing number of smart analysts and reporters like Phineas. It's time to take a serious look at a future that's more complex, and more hopeful, than simply taking a ruler and extrapolating traffic growth linearly ad infinitum.

Transportation planners and engineers, are you listening?