Peak Motorization: Measuring Rates of Auto Ownership and Distances Driven

University of Michigan transportation researcher Michael Sivak released his 10th "peak motorization" report last month [see abstract (pdf)] in a series that began June 2013. Sivak, who founded and directs Sustainable Worldwide Transportation at the University of Michigan Transportation Institute (UMTRI), focuses on two aspects of "peak car:" changes in ownership of passenger vehicles and distance driven, or vehicle miles traveled (VMT).

Both are measured as rates, per person and per household, as opposed to total VMT, which the Federal Highway Administration reports monthly in Traffic Volume Trends. The period examined was 1984 to 2016.

Southern California comparison

According to research released last month by the UCLA-Institute of Transportation Studies on causes for the decline in public transit ridership in Southern California, increased auto ownership was the primary reason.

Between 2000 and 2015, private vehicle ownership dramatically increased among households in the Southern California Association of Governments region, from 1.7 to 2.4 vehicles per household.

Contrast those nationwide rates provided by Dr. Sivak: 2.031 vehicles per HH in 2000 to 1.950 per HH in 2015. The UMTRI data would appear to more than verify the findings of UCLA-ITS in pointing to increased car ownership as the primary reason for the decline in transit ridership in Southern California.