WASHINGTON (Reuters) - U.S. auto safety regulators said Tuesday they have opened an investigation into the performance of Alphabet's Waymo self-driving vehicles after reports of its robotaxis exhibiting driving behavior that potentially violated traffic safety laws.

The National Highway Traffic Safety Administration said its preliminary evaluation into an estimated 444 Waymo vehicles follows 22 reports of 22 incidents including 17 collisions.

The agency said in some of those cases the automated driving systems "appeared to disobey traffic safety control devices" and some crashes occurred shortly after the automated driving systems "exhibited unexpected behavior near traffic safety control devices."

(Reporting by David Shepardson; Editing by Andrew Heavens)