by Michael Sivak.

In a recent article, I examined changes in distance driven in the United States during the period from 1984 through 2017. Distance driven per person reached a maximum in 2004. While this rate has been on a rebound since 2013, the 2017 rate is still down from 2004 by 5.2%.

The present study analyzes corresponding changes in the number of vehicles during the same period. The focus is on vehicles per person, as opposed to the absolute number (which depends, in part, on the continuously increasing size of the U.S. population).

Numbers of light-duty vehicles (passenger cars and light trucks) were obtained from the Federal Highway Administration. Resident population came from ProQuest.

The results are shown in the chart below.

The main findings (summarized in the table below) are as follows: Vehicles per person increased by 18.2% from 1984 to 2006 (from 0.665 vehicles to 0.786 vehicles), then decreased by 5.3% by 2012 (to 0.744 vehicles), and then increased by 3.4% by 2017 (to 0.769 vehicles).

In conclusion:

• Vehicles per person reached a maximum in 2006, two years after a maximum for distance driven per person.

• Vehicles per person has been on a rebound since 2012, but it is still down from 2006 by 2.2%. In comparison, distance driven per person is down by 5.2% from its maximum.

Michael Sivak is the managing director of Sivak Applied Research and the former director of Sustainable Worldwide Transportation at the University of Michigan.