OKOHAMA, Japan -- The robotic tugging beneath my light grip on the steering wheel was at once both slightly unnerving and reassuring.
Unnerving because of the erratic and constant wheel adjustments. Reassuring because it was proof that the computer brain of this "self-driving" car was duly at the helm.
Such was my first test drive of Nissan's new semi-autonomous driving technology in the real world sprawl of Yokohama's winding, elevated urban highways.
The technology, dubbed ProPilot, debuted this summer in the Nissan Serena, a Japan-market van. It is the first step toward Nissan Motor's goal of putting fully self-driving cars on the market by 2020.
ProPilot comes to Europe in the Qashqai crossover next year and eventually will be offered in the United States and China. Nissan and French alliance partner Renault plan to launch more than 10 vehicles with autonomous driving technology in four years.
The ProPilot system acts like an advanced adaptive cruise control in keeping pace with the cars ahead and braking to a full stop in traffic jams and at intersections.
The novelty is that the car can also steer itself around curves.
This allows the driver to sit back more relaxed in monotonous highway driving or mind-numbing congestion. Drivers can't completely let go of the wheel for more than a few seconds. If they do, the system will beep before disengaging the auto-steer function. But merely having two fingertips on the wheel is enough to keep it going.
The difference between driving and turning on ProPilot is noticeable. Even on Japan's busy city expressways, which frequently snake around buildings, bays and hills, ProPilot's self-steering function lightens the load of driving.
Self-steering kicks in at speeds over 50kph and only when the car's mono camera clearly detects lane lines on both sides.
But if you are in ProPilot mode, the self-steering function is mostly automatic. If it detects the lanes and you are driving stably between them, it takes over without having to push a button.
If you flick your blinker to change lanes or suddenly wrest control of the wheel, you break the self-driving spell. But after you switch lanes and switch off the turn indictor, ProPilot automatically resumes steering the car when it judges it safe to do so. The transition was usually seamless, making the ride all the more stress-free.
The twitching of the wheel back and forth seemed a bit more fitful than movements guided by a smooth human touch. And at high speeds around tight curves, the auto-steer function didn't seem to work as well. If the driver is not paying attention in such situations, the vehicle can drift lanes.
Choosing ProPilot also adds anywhere between 176,040 yen (about 1,550 euros) and 237,600 yen (2,100 euros) to the sticker price of the Serena in Japan, depending on the grade.
But for marathon drives and stop-and-go commutes, shelling out extra may be worth it.
Hans Greimel is Asia editor for Automotive News Europe sister publication Automotive News.