In the early 2000s, automobile use in the United States began to decline, after climbing almost steadily since motorized vehicles first hit the roads more than a century earlier.
Between 2004 and 2014, the number of miles driven by Americans fell by an average of almost 600 miles per person per year, according to government statistics. The data also revealed that young adults — so-called millennials born in the 1980s and early 1990s — were particularly inclined to stay off the roads.
This trend has been linked to the global economic crisis of 2007-2008, but also to other factors, including rising gas prices, increased household debt and changing lifestyles among young adults, including shifting attitudes toward travel.
The decline in automobile use has intrigued health researchers, who wondered if it might not only result in fewer automobile deaths, but also in Americans becoming more physically fit as they swap driving for walking and biking.
A new study, published online Thursday in the American Journal of Preventive Medicine, offers an answer that is both positive and, well, rather discouraging. It found that although the drop in per-capita miles driven was associated with a decrease in motor vehicle-related deaths, it did not appear to have any impact on activity levels.
“Despite predictions to the contrary, a substantial decline in auto use has not been accompanied by an increase in time spent in active travel nor in reallocating travel time to exercise,” writes Noreen McDonald, who conducted the study and chairs the Department of City and Regional Planning at the University of North Carolina at Chapel Hill.
Less time behind the wheel
For the study, McDonald used motor vehicle fatality data from the National Highway Traffic Safety Administration and auto travel and physical activity data (measured in daily minutes) from the Bureau of Labor Statistics’ American Time Use Survey.
The data covered a 12-year period, 2003 through 2014, and included adults aged 20 to 59.
McDonald’s analysis of the data revealed that daily automobile travel decreased by an average of 9.2 minutes between 2003 and 2014. The largest drop (21.7 minutes daily) was among men aged 20 to 29.
Not surprisingly, motor vehicle deaths fell during that period as well. The drop was 5.8 deaths per 100,000 people for all of the study’s age groups. But, again, the greatest drop (15.3 deaths per 100,000) was among young men.
“Many factors could explain this decline [in motor vehicle deaths],” writes McDonald, “ including improved driver safety training, such as graduated driver licenses, safer vehicles, and enhanced enforcement of device restrictions while driving. But, the decrease could also be explained by the large and significant drop in driving.”
No increase in time spent active
Although McDonald found that people were spending less time driving, she did not find any changes in the amount of time people spent being physically active.
According to her analysis, Americans spent an average of 19.1 minutes daily engaged in active travel (such as walking or biking), sports or other physical activity in 2014 — up only slightly (but not statistically significantly) from 18.6 minutes in 2003. Among young adults (men and women), daily physical activity remained remarkably stable: an average of 22.9 minutes in 2003 and 22.3 minutes in 2014.
“These results accord with analyses from the transport literature that show the drop in driving occurred because Americans were going fewer places, not because they were switching from cars to travel by bus, foot, or bicycle,” writes McDonald.
“Americans have stayed home more in the recent decade for a complex set of inter-related factors,” she adds. “Technological advances have eliminated the need for some face-to-face interaction. High gas prices, rising debt, stagnant incomes, and increases in unemployment have made driving more costly. Finally, delays in employment, partnering, and parenthood have lowered the need for certain types of trips.”
The trend shifts again
As McDonald points out in her study, people have recently begun to get back behind the wheel, with both driving time and motor vehicle fatalities increasing in 2015. Indeed, motor vehicle deaths rose nationally by 8 percent in 2015 — the largest one-year percentage increase in more than half a century, according to the National Safety Council.
In Minnesota, traffic deaths increased 14 percent in 2015. A total of 411 people lost their lives on the Minnesota’s roads that year, compared with 361 a year earlier.
“Our analysis shows that the nearly unprecedented decade-long decline in fatalities that the U.S. experienced through 2014 was connected to declining driving,” said McDonald in a released statement. “This greatly benefited public health through reduced roadway fatalities. The challenge that we must all now work towards is how to maintain the safety record on American roads as population growth, low gas prices, and an improving economy lead to more travel.”
FMI: You can read McDonald’s study in full on the American Journal of Preventive Medicine’s website.