WASHINGTON, D.C. — Nissan's Lane Departure Prevention system will debut this fall on the Infiniti EX35 compact crossover utility vehicle, providing drivers an additional safety net beyond today's existing electronic back-ups such as stability control and Infiniti's own Lane Departure Warning (LDW), explained Bob Yakushi, director of product safety for Nissan North America, Inc.

Fifty-five percent of all fatal crashes in the U.S. involve the vehicle leaving the road, he said, so keeping a car in its lane is a good start at eliminating some of those crashes.

The LDP system functions only if the driver ignores the warning from the LDW system, he said. As with LDW, the LDP system is disabled by the use of the turn signal, so intentional lane changes do not trigger a response. Similarly, if the computer notices that the driver has turned the steering wheel so the vehicle heads out of its lane, it will assume that the lane change is on purpose. But if the steering wheel is steady and the car reaches the line dividing its lane from the adjacent one, the LDP system leaps into action.

LDP does not have the ability to take over steering the car. What it does instead is use the tools of the electronic stability control system, the independent braking of individual wheels, to nudge the car back into the center of its own lane.

To use the LDP system, EX35 drivers will have to press an "on" button for it each time they start the car, ensuring they have decided that they want it working. Most drivers won't find the system bothersome, promised Yakushi, who tests Nissan's technologies himself. "The intervention when driving in a straight line is very light," he said. "It is more forceful on curves," he added, because of the extra amount of turning needed to keep the car in the lane in a curve.

Early prototypes of the system were more aggressive and might have bothered customers, but that is not the case with the version that Nissan is bringing to market, he said. "Initially it intervened very hard, but the latest version has been very acceptable."

What this means to you: One more electronic safety system. As long as they remain in the background, looking over our shoulders, the more the merrier. If it suffers too many unnecessary interventions, drivers probably won't be happy.