Nissan is preparing to launch its own self-driving taxi service, a sign that the Japanese auto giant is interested in challenging Uber in the race to deploy a fleet of money-making autonomous vehicles. Riders based in the Minato Mirai district of Yokohama, in Japan’s Kanagawa Prefecture, will be able to hail one of the self-driving Nissan Leaf vehicles using a new app. The vehicles will be geofenced along a 4.5-kilometer route between Nissan’s global headquarters and the Yokohama World Porters shopping center. Safety drivers will remain behind the wheel of the vehicles, and a remote operations center has been set up to monitor the car trips. The companies say they will expand the service to a much wider market by 2020.