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Citroen C4. Lane warning system - Ben79
From Citroen.com about the new C4:

- The Lane Departure Warning System is a major step forward in driving safety. On motorways or main roads, this innovative system warns the driver if the car crosses the lane markings, if he has not activated the indicator. A vibrating mechanism mounted in the car seat is triggered on the side corresponding to the direction of vehicle drift to alert the driver who may, for example, be feeling drowsy.

Sounds like a nightmare to me! I hope it can be switched off. Imagine what would happen on a quiet road whenever you cross the line? For my driving, the vibrating mechanism in the seat would be broken in days!

Still the car looks nice.
Citroen C4. Lane warning system - NowWheels
I can imagine some people being tempted to drive on the lane markings just to enjoy the vibrations ...