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October 11, 2013

Analysis of Recent Changes in Driving Behavior

Recent studies highlight changing driver behaviors, which could impact GO TO 2040 priorities related to congestion management.  A new report from the U.S. Public Interest Research Group (U.S. PIRG), "Moving Off the Road: A State-by-State Analysis of the National Decline in Driving," documents the recent decline in vehicle-miles traveled (VMT), a measure of overall driving, and argues that this decline cannot be attributed to the relatively high unemployment rates that remain after the Great Recession.  In this and another U.S. PIRG report from earlier this year, the organization argues that changing preferences in the Millennial generation -- i.e., a shift away from driving in favor of transit, biking, walking, and telecommunications -- are the cause of this decline in driving and that federal transportation policy should be reformed to accommodate that shift.

This past summer, two reports from the University of Michigan also focused on young drivers.  The first found that driver's licensing among young people has declined in recent years.  Today only 60 percent of those aged 17-19 hold a driver's license, compared to 80 percent in the 1980s.  The second study investigated the reasons why young people have delayed or forgone obtaining a driver's license.  Survey respondents identified a range of reasons, with the most frequently cited reasons (primary or secondary) including being "too busy" to obtain a license (37 percent), the expense of owning and operating a vehicle (32 percent), and the ability to receive transportation from others (31 percent).  Looking at the attractiveness of alternative modes, 22 percent of respondents cited a preference for walking or biking, 17 percent cited a preference for public transit, and 8 percent cited the ability to complete various interactions online.


The U.S. PIRG reports have generated some debate among transportation analysts.  The data show a decline or stabilization in driving, particularly among young people, but the reasons why are less clear.  Some have argued that the recent decline in driving is a result of taking fewer and/or shorter trips, not a shift in favor of alternative modes of travel.  A recent event at the Volpe National Transportation Systems Center identified several potential causes of the decline in driving, including the impact of relatively high gas prices on younger drivers, tougher teen driving laws, the large costs of owning and maintaining a vehicle, the state of the economy, and broader demographic trends. 

In fact, transportation analysts have for some time predicted a moderation in VMT growth as the result of broad demographic shifts.  The stabilization of average household sizes, female labor force participation, and female driver's licensing; the aging of the Baby Boomer generation; and other demographic trends all suggest that VMT will not continue to increase as fast as it had throughout the second half of the 20th Century.

Despite the recent decline and stabilization of VMT, commuting mode shares have remained fairly stable over the past decade.  CMAP's analysis of U.S. Census Bureau commuting data for the seven-county region shows that the share of commuters driving alone and taking transit have stayed relatively stable between 2000-10, while the shares for carpooling declined and bicycling and telecommuting increased.  Further, the Volpe event also found the recent decline in VMT doesn't appear to be driven by alternative modes of travel, noting that "gains in transit, biking or walking, and teleworking each account for only about 1% of the recent decline in VMT."


There is not yet sufficient data to determine whether the observed decline and stabilization in driving represents a long-term shift and whether there has been a substantive change in young people's travel preferences.  While measures of overall driving have declined recently, it is important to note that urban congestion is increasing after the Great Recession and commuting mode shares haven't changed substantially in the past decade. 

GO TO 2040 sets a goal to maintain the 2010 levels of congestion – 1.8 million congested hours of travel per day – even as the region adds over 2 million new residents by 2040.  The plan relies on more efficient land use patterns, targeted improvements, congestion pricing, and other strategies to do so.  As this discussion suggests, the plan may also be aided by broad demographic trends that indicate a long-term moderation in driving.