In 2021, the average American traveled 9 times farther by road than by air

08 August 2022

by Michael Sivak, Sivak Applied Research.

This post examines the distances that the average American traveled by passenger road vehicle and by plane in 2021. In both instances, the distances to be compared are person miles.

The derivation of person miles traveled by air is straightforward from the available monthly data: In 2021, the airline revenue passenger miles for domestic operations totaled 572 billion miles.

The derivation of person miles traveled by passenger road vehicles is a bit more complex, and it involves summing up calculated person miles traveled by light-duty vehicles (cars, SUVs, pickup trucks, and vans), buses, and motorcycles. (In other words, all vehicles except for medium and heavy trucks.) The procedure will be illustrated by the derivation of person miles traveled by light-duty vehicles.

In 2021, the distance traveled by all road vehicles amounted to 3,228 billion miles. At this point, we need to consider distance driven by light-duty vehicles only and the average number of persons per light-duty vehicle. However, these data points are not yet available for 2021. Therefore, we will rely here on the 2020 data.

Assuming that the percentage of distance traveled by light-duty vehicles in 2021 was the same as in 2020 (88.5%), we obtained that the vehicle distance traveled by light-duty vehicles in 2021 was 2,857 billion miles. Assuming that the vehicle load in light-duty vehicle in 2021 was the same as in 2020 (1.68 persons), we end up with 4,800 billion person miles.

Analogous calculations show that in 2021 buses accumulated 339 billion person miles and motorcycles 23 billion person miles. Adding these two person distances to the person distance accumulated by light-duty vehicles, yields a total of 5,162 billion passenger-vehicle person miles.

Dividing the passenger-vehicle person miles (5,162 billion) by the revenue air miles (572 billion) results in 9.0. Thus, for each mile of domestic air travel, Americans traveled about 9 miles on the road.

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