WASHINGTON, June 12 (Reuters) - The National Highway

Traffic Safety Administration said Wednesday it is seeking

additional details about a series incidents that raise concerns

about the performance of Alphabet's Waymo self-driving

vehicles.

In May, the U.S. auto safety regulator opened an

investigation after 22 reports of its robotaxis exhibiting

driving behavior that potentially violated traffic safety laws,

or demonstrating other "unexpected behavior," including 17

collisions.

The agency on Wednesday said Waymo is to respond to a

series of detailed questions by Aug 6 including comprehensive

details of all travel on public roads by the company's

driverless vehicles.