A General Motors Co. executive credited Silicon Valley companies, including Alphabet Inc.’s Google car division and Tesla Motors Inc., for accelerating the development of autonomous vehicle technology and shortening the timetable for when safer self-driving cars hit the road.

Richard Holman, a 30-year automotive veteran running GM’s foresight and trends unit, said Tuesday that three years ago most industry participants would have estimated 2035 as a reasonable timetable for self-driving cars. Speaking to a conference in suburban...