Planning for the End of the Driving Boom

March 27th, 2014

Americans are driving less and owning fewer cars, which means we have to make different decisions about where to spend scarce transportation resources.

In a fascinating post in the Atlantic Cities, Eric Jaffe doesn’t waste words with assumptions but rather relies on actual data to inform us that America has already reached “peak driving” and that the future of transportation in America is no longer linked to ever-increasing vehicle miles traveled (VMT).

This should come as no surprise, given that VMT has missed forecasted estimates since the early 2000’s. Just check out this handy chart from the U.S. Department of Transportation’s Conditions and Performance Report (PDF) to Congress.

Figure 1. U.S. VMT (in trillions) as tracked by FHWA’s Travel Volume Trends (“Actual”) and as projected by U.S. DOT’s C&P reports (by year reports are dated). Via SSTI. Click image for original:


Regional roadway planners are already beginning to embrace this thinking, as the chart from the State Smart Transportation Initiative illustrates in its analysis of MDOT’s transportation plans. These plans not only acknowledge declining VMT, but now omit traffic projections altogether.


From S.S.T.I. via Atlantic Cities.


Why should we in the D.C. region be especially cognizant of this? Because we are about to make commitments to hundreds of billions of dollars in transportation investments,(PDF) and we ought to make ones that are built for the future, not the past. This region just might be leading the way in terms of charting a course towards a new mobility paradigm, and here’s why.

This new mobility paradigm is due in part to a shift in thinking from our newest cohort just now entering adulthood. Generation Y is not only driving less, but opting to own fewer cars. The emergence of Generation Y (aka Millennials) are the fastest-growing segment of regional population growth (PDF). Moreover, they are primary reason that this region is experiencing an urban renaissance: almost all of the District’s population growth between 2000 and 2010 was due to young adults age 20 to 34, whose numbers swelled 23 percent.

This group not only drives less, and owns fewer cars, they have fewer driver licenses. From 1983 to 2008, the share of 16- to 39-year-olds with driver’s licenses declined markedly (PDF).  In 1983, 92 percent of individuals aged 20-24 had drivers licenses. By 2008, this figure was down to 82 percent, a 10 percentage point drop! Even among 35-39 year old drivers, the decline was 3.2 percent.

Federal Highway Administration data confirms that this trend is continuing. According to a 2012 analysis of their data, the share of 20- to 34-year-olds with a driver’s license decreased from 89.6 percent in 2000 to 84.3 percent in 2010.

Compounding that fact, for those that still do get licenses, car sharing is becoming the new normal. Given that each shared car in existence takes 10-15 “owned vehicles” off the streets – and also since the average owned vehicle spends 95% of its time sitting in one location – We may need to revisit the extent to which planning for “owned” vehicles is the primary function of roadway planners and instead focus more attention paid to the science of planning for “fractionally-owned” vehicles (car sharing).

A recent Transportation Planning Board analysis picked this up last year:  just check out how the way this region’s commute is changing.  Lots of increases in transit, walking, biking, and telework.  Driving cars – on the decline (even for carpools).


Commute Mode Share, from a MWCOG assessment of Changes in Regional Commuter Patterns 2000 – 2011.

We can see this at Metro, where driving alone and parking at Metro is the preferred access mode of only 26% of our riders in 2012.  In fact, park and ride was down 11% between 2007 and 2012 even while total peak trips were up over the same time period. Meanwhile, car sharing companies are proliferating and competition for the fractional car owner market is fierce.


With car ownership down and car sharing up, the streets might just be less clogged with parked vehicles – car sharing vehicles tend to be in motion rather than sitting still – and we may need to program less overall physical space for storing vehicles, freeing up space for moving people on buses and bikes (hint – bus ridership and bike ridership are on the rise). Most importantly, we might need to double- or triple-down on the transit investments we are making. After all, if we are to plan our region’s future on the demands of the future generation of leaders, entrepreneurs, bankers, scientists, and educators, we should probably avoid building for them their parents’ transportation network.

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  1. Alan
    March 28th, 2014 at 11:20 | #1

    I think in the future car sharing will need to become a separate category. The couple of times a month I just need to drive I can always rent a zipcar or a car2go. I pay about $100 a year for the privelege of having those options at my finger tips when I need them and it’s totally worth it. As they gain a better foothold, I expect they will infiltrate the inner suburbs more thoroughly as well.

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