Nissan Leaf passes autonoumous driving test on Japanese highway.

We're not sure how to translate "ghost-riding the whip" in Japanese, but Nissan appears to have mastered the concept. Earlier this week, the Japanese automaker tested a self-driving Nissan Leaf electric vehicle on public roads for the first time and proclaimed the exercise a success in driverless motoring.

Nissan equipped the vehicle with its so-called Autonomous Drive feature and took the car out onto Sagami Expressway in Kanagawa prefecture. The car, the first with Autonomous Drive to receive a license plate in Japan, is programmed to merge, change lanes and maintain a safe distance relative to other vehicles, all without the aid of a driver's controls.

Nissan has joined a growing list of companies that are testing the concept of autonomous driving, which in some circles is seen to potential improve both safety and fuel economy. Most notably, Swedish automaker Volvo last year tested its Sartre road train project in Spain. Volvo used three vehicles equipped with cameras, radar and laser sensors that tailed a truck for about 120 miles going about 53 miles per hour. The cars were about 20 feet apart and were programed to accelerate, brake and turn in the same way as the lead truck, which all worked as planned.