U.S. vehicle safety regulators have said the artificial intelligence system piloting a self-driving Google car could be considered the driver under federal law, a major step toward ultimately winning approval for autonomous vehicles on the roads.

The National Highway Traffic Safety Administration told Google, a unit of Alphabet Inc, of its decision in a previously unreported Feb. 4 letter to the company posted on the agency’s website this week.

(Reporting by Paul Lienert in Detroit and David Shepardson in Washington; Editing By Cynthia Osterman)