Self-driving tractor-trailers heading for U.S. roads

On a three-lane test track along the Monongahela River, an 18-wheel tractor-trailer rounded a curve. No one was on board.

A quarter-mile ahead, the truck's sensors spotted a trash can blocking one lane and a tire in another. In less than a second, it signaled, moved into the unobstructed lane and rumbled past the obstacles.

The self-driving semi, outfitted with 25 laser, radar and camera sensors, is owned by Pittsburgh-based Aurora Innovation Inc. Late this year, Aurora plans to start hauling freight on Interstate 45 between the Dallas and Houston...