Nissan Motor Co. said a self-driving version of its electric Leaf car made its first foray onto public roads. Its guidance system, called Autonomous Drive, senses road conditions and operates the car's steering, acceleration and braking as it merges into traffic, changes lanes and makes adjustments to keep a safe distance from other vehicles.

The Leaf drove on Japan's Sagami Expressway in Kanagawa prefecture, southwest of Tokyo. Nissan vice chairman Toshiyuki Shiga and the prefecture's Governor, Yuji Kuroiwa, rode in the car...