The Tesla was operating in Autopilot mode. It raised some questions about whether drivers were lulled into a false sense of security by the technology.
"From the beginning, we worried about that situation," said Kiwamu Aoyanagi, a manager in Nissan's autonomous driving and advanced safety development group.
Nissan's new technology, dubbed ProPilot, is the first of a three-stage ramp-up to urban autonomous driving by around 2020. ProPilot debuts in the redesigned Serena family van scheduled to go on sale in Japan in late August. Nissan said it will offer ProPilot in the Qashqai crossover in Europe next year and also bring it to vehicles in the U.S. and China.
It didn't give a timeline for those latter introductions.
ProPilot enables single-lane semiautonomous driving in highway conditions. Like an advanced cruise control, the technology keeps the vehicle a safe distance from the vehicle ahead by modulating speed.
It also can brake the car to a complete stop when necessary. It equates to Level 2 autonomy under the National Highway Traffic Safety Administration's system. Fully autonomous drive is Level 4.
ProPilot introduces the autonomous function of self-steering the car to keep the vehicle centered in the lane. It also steers the vehicle smoothly around curves.
While the system allows drivers to loosen their grip on the wheel, it won't let the driver let go for long. A torque sensor on the steering column senses whether a hand is at the helm.
If not, a warning light comes on. If the driver still doesn't take hold, a warning beeper starts to chime. If there is no grip for several seconds, the self-driving function disengages.
"We've taken many countermeasures," Aoyanagi said of keeping drivers alert.
For starters, salespeople are being trained to carefully educate customers about the technology's limits. As another precaution, ProPilot can't be used when the windshield wipers are turned to either low or high mode because the system doesn't have good visibility in heavy rain. If the wipers are on, the engineers reasoned, it must be raining. It still works when wipers are in intermittent mode, when rain is presumed to be lighter.
The system to be deployed in Japan uses a mono camera supplied by TRW Automotive Holdings Corp. and an image processing technology from Mobileye NV.
ProPilot packages for other markets might employ other sensors, such as millimeter wave radar, to increase the range or speed of object detection, Aoyanagi said. High-speed driving on Germany's autobahn, for example, would require longer vision and faster reaction.
Despite the extra precautions to manage driver expectations, ProPilot largely achieves its goal of lightening the load on the driver. Nissan envisions it as a tool to break the monotony of long-range highway driving or mind-numbing stop-and-go traffic jams.
During a brief test around Nissan's Oppama Proving Ground south of Tokyo, the steering wheel required only the lightest touch to keep the system activated. Two fingertips were enough. And the system relieved the driver of having to work the brake and gas pedals.
To spur quick adoption of the technology, Nissan said it will be available in Japan in vehicles priced below ¥3 million ($28,900). It did not give specific pricing details.
The current Serena starts at $20,260 and runs as high as $31,310. Nissan did not say what versions of the vehicle will get ProPilot.
The autonomous driving technology aims to dent the number of traffic accidents that are caused by human error, which Nissan says is 93 percent. The goal is a car that senses dangerous scenarios and avoids them before drivers are even aware of the looming perils.
"That is the kind of technology we are trying to develop," Sakamoto said.
The Japanese automaker plans to build upon ProPilot with a more advanced system due around 2018 that will allow automated driving across multiple lanes.
The rollout will culminate in a sophisticated autonomous system that will allow "intersection autonomy" by around 2020. That function will allow cars to navigate city intersections and urban traffic without driver intervention, Nissan promises.
Nissan and its French alliance partner Renault SA say they plan to launch more than 10 vehicles with autonomous driving technology in the next four years.
The race for autonomously driven cars is heating up across the industry, with all major manufacturers planning some kind of introduction over the next several years.
IHS Automotive forecasts annual sales of nearly 21 million autonomous vehicles in 2035, as automakers, suppliers and technology companies pump money into developing next-generation cars. The U.S. will see the earliest adoption, with several thousand autonomous vehicles on the road in 2020 and some 4.5 million sold annually in 2035.
Looking ahead, Nissan executives said there is still much work to be done to improve the capabilities of today's autonomous driving systems.
The resolution of image detection must increase, the formulas for decision analysis must be improved, and the rate of computation must speed up to boost reaction times.
Meanwhile, human machine interface must become more intuitive, and vehicle connectivity must be fully harnessed so cars can connect to the Internet and get a fuller picture of all surrounding traffic conditions, both those nearby and those out of sight.