What is the Lane Departure Warning System (LDWS / Spurhalteassistent) on heavy commercial vehicles?

1. A navigation function that automatically changes lanes whenever the programmed route requires an exit
2. A system that keeps the truck centred in every situation, allowing the driver to stop monitoring lane position
3. A blind-spot warning that detects only vehicles alongside the passenger door
4. A camera-based system that monitors lane markings and warns the driver via acoustic signals, seat vibration, or steering torque if the vehicle drifts out of its lane without indicating