Lane departure warning is part of the so-called circle of safety: adaptive cruise control pacing you against the car in front, lane departure warning or lane keep assist watching ahead and to the side, blind spot detection watching for cars coming up in adjacent lanes, and rear parking sonar and a camera behind (sometimes on all four sides) watching behind when you’re backing up. Lane departure warning/lane keep assist is so good now, the best systems could keep you centered for miles and miles. It’s really a self-driving car at that point. All of them cut out after a few seconds if they detect no hands on the steering wheel.