SAN FRANCISCO—Japan’s Toyota Motor and Aurora Innovation Inc, a U.S. developer of automated driving systems, have started testing autonomous ride-hailing fleet in Texas, with two safety operators and no passenger on board, Aurora said on Tuesday. Toyota’s Sienna minivans, retrofitted with Aurora’s self-driving system, will be tested on highways and suburban streets in the Dallas-Fort-Worth area, with the operation including trips enroute to an airport. Autonomous vehicle startups are under pressure to generate meaningful revenue from billions of dollars of engineering investment, but scaling up the fleet is a challenge as technological hurdles remain. “The route showcases Aurora’s ability to safely operate at highway speeds, a key technical differentiator that allows it to prioritize popular and lucrative rides,” the U.S. company said in a statement. Aurora’s rival Waymo charges passengers of its driverless minivans for rides in limited suburban areas in Phoenix, and airport pickups are not available. Waymo said …