Will Transportation Investments Keep Up With the Way Americans Travel?

Phineas Baxandall is a senior analyst at the U.S. Public Interest Research Group.

It’s now common knowledge that annual changes in the volume of driving no longer follow the old patterns.

For 60 years, the amount of vehicle miles traveled (VMT) rose steadily. Predicting more driving miles next year was like predicting that the sun would rise or that computer chips would be faster. The only direction seemed to be up.

Then, after 2004, per-capita VMT fell 6 percent, which has led to a decline in total VMT since 2007.

The most recent data are from July, traditionally America’s biggest month for driving. In July 2012, Americans clocked over 258 billion miles behind the wheel, a billion fewer miles than the previous July despite a slightly stronger economy and cheaper gasoline. In fact, you’d need to go back to 2002 to find a July when Americans drove fewer miles than July 2012.

Has America’s long increase in driving turned a corner or just taken a prolonged pause? The answer matters a lot. Consider four scenarios:

Graph: Phineas Baxandall, U.S. PIRG
  1. If the volume of annual vehicle miles traveled switches back to the average rate of increase between 1987 and 2005, then by 2025 VMT will be 27 percent greater than the 2012 level.
  2. If VMT changes at the average rate it sustained over the entire period between 1987 to 2012, then it will grow by almost 19 percent by 2025.
  3. If instead VMT changes at the average rate that has prevailed since 2004, then the number of miles driven will fall 2.3 percent by 2025.
  4. And if VMT changes at the average rate that has prevailed since 2007, then VMT would fall off by almost 8 percent by 2025

    Table: Phineas Baxandall, U.S. PIRG

The difference spanning these scenarios amounts to over a trillion vehicle miles per year. How we decide to invest in transportation should be very different, depending on which scenario we are planning for – especially since the roads, railways and other infrastructure we build today will be with us long past 2025. Continuing to build new highways at the current pace might arguably make some sense if driving were to return to pre-2005 rates of growth. But those outlays indisputably would be a colossal waste if more recent trends prevail.

There are good reasons to believe the current slowdown in driving may persist. A report by the U.S. Public Interest Research Group earlier this year showed that youth are leading the trend toward less driving. Americans aged 16 to 34 reduced their miles driven by 23 percent between 2001 and 2009. Changing patterns in the use of information technology may be a major factor in reduced driving that is also encouraging growing transit ridership.

It won’t be surprising if an upturn in the economy leads to some increase in driving, especially if gas prices don’t also surge. But it’s harder to imagine that we will switch back to the sizeable increases in VMT that took place almost every year for six decades after World War II. Even if driving continues to increase at the rate of population, this would be a long-term slowdown that should correspond to major changes in transportation policy. While we can’t yet see “the new normal,” it’s a good bet that it won’t be the same as the old normal.

You wouldn’t know that from the last transportation bill. Congress needs to stop trying to build out our grandparents’ transportation system.

15 thoughts on Will Transportation Investments Keep Up With the Way Americans Travel?

  1. It would be informative to look at the correlation between VMT and a lot of the variables that are often associated with it: GDP change; employment change; transit ridership; gas prices; change in # of licensed drivers; population change; change in population for different groups; etc. Wherever there are statistically significant correlations among these categories, there are great opportunities to drill down to see what’s really going on. In particular, it would be important to show that the recent VMT trend is not purely a function of GDP + wage stagnation. 

  2. The funny thing is that their grandparents’ transportation system was built out already, and then doubled, and that’s not enough for some people. 

    There’s really no end to the redundant, half-useless extensions of highway lanes in America, especially not when politicians like Andrew Cuomo act as if mega-super-highways are projects that are  impervious to cost-benefit analysis. They nitpick over every park or firehouse in densely populated areas, but hardly blink at committing $5 billion to an ultimately-$10-billion single-mode triple-redundant bridge between suburban counties along nobody’s cargo route.

    We don’t need a reworked transportation bill, we need a change in psychology and priorities on a national level.

  3. Oh, I’m absolutely sure if the economy picks up and gas prices go down people would start driving more again. This decrease is simply due to people not being able to afford cars (car, insurance and gas). People are more broke than ever, particularly the young ones who have hard time finding good jobs.

  4. No.

    At some point the road system stopped expanding as fast as VMT.  And now there will be no money for roads or transit.  We’ll be lucky to keep, or in the case of the Tappan Zee replace, what we’ve got.

    Which is why bicycles and the internet make sense.  Low cost for a bankrupted country.

  5. Well isn’t the most important fact that the reversal preceded the recession by a couple of years. Becoming pretty clear that this is more likely a discontinuity with the past pattern and not just a pause from it. Anyway that increase could not continue indefinitely and there is plenty of other evidence that suggests that the culture, all across the developed world, has turned significantly away from the previous pattern. Bet get your policy in line with a new reality boys and girls.

  6. This is a great point, but there is no practical method for addressing it. The VMT measures here are at a national scale (I think), while the problem with too many cars on the road is mainly felt at a regional scale. Further, funding to address the problem (FHWA and FTA funding) is directed toward Transportation Management Areas, geographies not necessarily congruent with the regional scale. The only way to address the issue in the way it is presented here would be to totally re-do transportation funding throughout the nation.
    Even then, though, big complication: fast-growing MSAs (Houston) still need additional capacity for SOVs despite the per-capita decrease in VMT; while slower-growing (or more stable) MSAs may not…

  7. Great stuff, Phineas. No doubt policymakers are finding it difficult to react to these changes. Probably because they do not exactly know or understand the cause, because it is complicated. The dramatic and fundamental shifts in driving habits—that essentially went unchanged for decades—is not the result of one thing. More likely is that the changes we are seeing are due to a confluence of factors: Structural changes (women entering the workforce, civil rights); changes in consumer preferences for mode and housing choice (transit, telework); restrictions or constraints to driving (tougher licensing rules (GDL), national recession).

    Almost irrespective of the reason, the point is that there are direct implications for how billions of dollars in public funding are spent.

    Re GDP: more research is clearly needed a simple correlation between GDP and aggregate VMT and VMT per capita shows near total correlation before the recession and almost none after. Burwell also discusses this “decoupling” of VMT and GDP in the US and the UK. (http://www.guardian.co.uk/environment/2012/jun/12/america-motor-car-transport)

  8. I think what you are seeing is the continuing dissolution of the post industrial landscape.  Before the Industrial Revolution people lived on farms and small villages and did not travel because everything was right at hand. With the advent of huge factories and huge centralized information systems (book keepers, clerks, secretaries, engineering, design & executive decision makers ) big cities developed because of the necessity to be “close”.  Not true any more!  I look to a semi-urban form to develop.  The Metro Detroit area will lead the way too.  The core city will look much like the suburbs; people will work and live in neighborhoods.  The core city needs to “de-road” (much more radical than a “road diet”)  The I-375 spur and the M-10 Lodge below I-94 will be removed and returned to surface streets, housing and small business.  I-96 will be reduced to 3 lanes in each direction. M-39 will be a Boulevard too!   I will not live long enough to see these changes but filling in these vast moats full of steel crocodiles will erase these artificial barriers and enable neighborhoods to flourish once again! 

  9. Rob, I think if you take a long range look at VMT and GDP (like on a decennial basis), you’ll see there was near correlation in growth rates from the 1960s through the 1980s, but that it broke down substantially (GDP grew substantially faster than VMT) starting in the 1990s and continuing through the 2000s.

  10. Definitely see that in the decade-by-decade correlations but our data didn’t really see it as far back as the 1990s. it was really after 2000 that they diverged pretty substantially.

    But the literature does back up your point and the exceptional returns from public investments didn’t hold up. Although the benefits and savings for trucking alone justify one-third to one-half of the federal highway investments between 1950 and 1973 (largely the interstates) the productivity did not continue as investments have lost focus and direction. In 2004, Shirley and Winston study found that the transportation investments the U.S. made in the 1970s generated an 18 percent return followed by a 5 percent return for 1980s investments, and only a 1 percent return for the 1990s.

    (Shirley, Winston: http://www.fhwa.dot.gov/policy/otps/060320d/index.htm also Mamuneas: http://www.fhwa.dot.gov/policy/otps/summaries.htm)

    I believe, though, that the literature on the correlation between economic growth and VMT is a bit all over the place and not totally conclusive.

  11. This is interesting and informative. I guess as time goes by, our way of traveling also changes. We should be able to adapt to certain changes like this one.

  12. The chart showing VMT leveling off is almost the exact shape shape as the figures showing global oil production.   It’s almost a one for one relationship.

    VMT cannot increase as oil supplies decrease, even considering modest improvements in vehicle efficiency that may (or may not) happen in the future.

    http://www.peaktraffic.orgPeak Traffic and Transportation Triage:cancel trillion dollar highway expansion plansprepare for post peak travel

  13. It’s hard to imagine that this trend is the result of slackening oil production. That change would affect US driving behavior through gas prices and the ups and downs don’t track that well with changes in the volume of driving.

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