CALIFORNIA — The day a person can sit inside a car and travel anywhere without a human operating the controls is still years away, but autonomous vehicles in California are logging more miles than ever as they strive to make that vision a reality.

About four million autonomous miles were driven on public roads in 2021, according to a new report from the California Department of Motor Vehicles released Wednesday — double the number of miles logged a year earlier.

Every January, the California DMV requires the AV companies it has permitted to submit reports that detail the number of miles their autonomous vehicles have driven.

Fifty companies currently have valid permits to test AVs with a human safety driver as a backup, including Apple, BMW, Nissan, Tesla, Toyota and Volkswagen.

The record number of autonomous test miles with a safety driver took place even with 28 of the 50 California permit holders reporting they did not test AVs during the reporting period, from Dec. 1, 2020, to Nov. 30, 2021.