Originally Posted By: dishdude
I think you're combining two separate systems. There is lane departure that uses a camera to see the painted lines on the road and will alert you if you're riding on one of the lines without your signal. This is usually alerted by vibrating the steering wheel or seat. As soon as you get off the line it stops.
Blind spot detection is typically a light in the side mirrors and an audible warning that operates by sonar. It will sound if you attempt to enter a lane when a car is present with the signal on.
Our Subaru's Eyesight uses two cameras (stereoscopic) to monitor depth and location, and will provide lane departure, adaptive cruise, and pre-collision braking.
IIRC, the lane departure will beep at me not only when I start to cross the lane, but if I swerve suddenly. I've had it beep at me while driving along curvy roads, since I like to pretend I'm in a rally-cross (at sane speeds) and hug each line. It doesn't vibrate the seat or steering wheel, just beeps.
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Do cars really employ sonar for location? I think it would make more sense to use radar. I could be wrong, but I believe sonar can be heard and radar is not audible. I can imagine some really old sailors losing it when another car drives by and goes active!