# BMW Explained: Lane Departure Warning



## tim330i (Dec 18, 2001)

https://www.youtube.com/watch?v=cMd9Fym_3fU

Fatigue or inattentiveness on the road can cause a driver to unintentionally leave a lane. This could result in the vehicle driving into a lane with oncoming traffic or ditches at the side of the road. BMW's lane departure warning is a driver assistance system designed to inform the driver in good time of unintentional course deviations by means of vibrations in the steering wheel intended to prompt the driver to make corrective steering movements.

The lane departure warning is a driver assistance system. The area in front of the vehicle is captured by a camera. This makes it possible for the roadway markings to the right and left of the current lane to be detected. If the vehicle approaches a roadway marking in the absence of a turn indication, the driver is informed of the course deviation by steering wheel vibrations before the vehicle crosses the line. The camera is fitted near the rear-view mirror behind the windscreen and its camera images to the control unit on a data line.

The control unit contains the software that determines the position of the vehicle in the lane from the camera images. The lane departure warning is designed for operation on highways, major roads and well maintained country roads. A warning is issued if the system (current driving conditions within a specific time frame being equal) detects that the vehicle is crossing the roadside border line. The warning can be felt as a vibrating of the steering wheel.

When the ignition is switched on, the lane departure warning system always reverts to the state that was active when the vehicle was last switched off (last function mode). The display indicating whether the lane departure warning is switched on or off is output by the instrument cluster or, optionally, by the head-up display. When the lane departure warning is switched on, there is an additional display indicating whether the system is primed or not. The system is only primed if it is switched on and has detected one or two roadside border lines with the vehicle travelling at a speed faster than 45 mph and deactivates at speeds below 42 mph.

https://www.youtube.com/watch?v=4jq_Mq2SfLE

*Availability of the Lane Departure Warning*
The system is available when:

No system fault is present
The lane departure warning system is calibrated correctly
The vehicle speed is above the activation threshold (see following table)
At least one roadway marking has been detected by the system with sufficient certainty
The vehicle is not in a construction site area with several possible roadway markings
The vehicle is on a road with an average lane width of more than 8 feet

*Land Departure Warning*
The lane departure warning function only outputs a warning to the driver if the system is switched on and available. The system outputs the warning to the driver if the driver approaches a detected roadway marking. To do so, the system calculates the anticipated time before the roadway marking is crossed. The warning is output in time before the vehicle crosses the marking. Since warning situations may arise more frequently on narrow roads, the warning is output later by tendency on these kinds of road.

*Warning Duration*
The warning ends when:

The driver steers back into the lane
A lane change is completed
The vehicle drives on the line for longer than 2.5 seconds 
The turn signal is operated
The brake pedal is depressed with force (brake-pressure-dependent)

Note: A warning is output only once on approach to a roadway marking. The warning lasts no more than 2.5 s. If the vehicle remains on the line, no new warning will be issued. A new warning can only be issued if the vehicle has been steered back into the lane or the vehicle has completed a change of lane.

*Suppression of the Warning*
A warning is suppressed despite the display of primed status if the following conditions exist on one side:

Turn signal operated before the vehicle is driven towards the warning trigger
One-touch turn signal indicated on the side from which a warning would be triggered
There is no warning suppression if the hazard warning flashers are switched on


----------



## AntDX316 (Nov 3, 2009)

Lane departure somewhat saved me today. I passed a car, I was on the left lane the whole time, going slower on the right to go right to make a turn coming up. The steering wheel alerted me and I realized if I have a signal on and it still alerts something must be up. I checked and saw the triangle flashing and the cars lights near the rear fender. I think I was making the turn without looking thinking I did clear it but the alerts made me look one very last time and realize to abort the lane change. I just wish computers assisted with more things in real-life than just this, vehicle wise.


----------



## GeorgeBush234 (Jan 31, 2012)

the vibration of the streering wheel it s a fair warning for safe lane change.


----------

