Mandatory since 2022
How does lane departure warning work?
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Lane departure warning systems intervene if a vehicle accidentally drifts out of its lane. The practical helpers are now mandatory equipment for new cars.
All it takes is a moment of inattention for a vehicle to veer out of its intended lane and endanger other road users or veer off the road. Lane departure warning systems can prevent this often dangerous and unfortunately not uncommon moment and keep vehicles in the intended lane before leaving the lane. In contrast to the so-called lane departure warning system, which only warns acoustically or, for example, with a vibrating steering wheel, lane keeping assistants actively intervene in the steering and steer the vehicle back into the lane.
This assistant was first offered in a Nissan Cima sold in Japan from 2001. Lane keeping assistants are now widespread. Since 2022, they have even been mandatory for new cars in Germany. Since this year they have been mandatory for all new cars.
Car constantly monitors its own lane
The technology of the lane keeping assistant and lane departure warning system is identical in terms of sensors: the car constantly monitors its own lane in order to detect departure. This is almost always done via a camera on the windshield, but can also be achieved using infrared sensors on the vehicle floor, for example. In addition to this visual information, driving parameters such as steering angle and speed are also included in the situation analysis. The optical sensors are primarily based on the road markings. If these are confusing, for example in construction sites, lane departure warning systems often cannot interpret this information correctly.
The system detects unintentional lane departure because the driver does not use the turn signal. If the vehicle threatens to leave the marked lane area without signaling, the lane departure warning system intervenes. In cars with electronic power steering, the system countersteers at this moment and gently maneuvers the car back to the center of the road. Models in which direct steering intervention by the computer is not possible usually rely on the Electronic Stability Program (ESP). It enables targeted braking of individual wheels. The short deceleration on the inside wheels pushes the car back into line. This is much rougher than steering intervention, but it also wakes up the inattentive driver.
Hands off the wheel is only possible for a short time
In many newer vehicles, lane departure warning systems allow the driver to take their hands off the steering wheel for a certain period of time. If the lane departure warning system is active, the steering is continuously adjusted in small steps to keep the vehicle exactly in the lane. However, if the driver does not put his hands on the steering wheel for several seconds, the on-board system asks him to take control. If this does not happen, there is usually a multi-stage warning that the lane keeping function will be automatically ended.
Anyone who is bothered by the constant steering interventions usually has the option of switching off the lane departure warning system. In the vast majority of cases, they are automatically reactivated the next time the engine is started and must therefore be deactivated again after each restart.
No carte blanche for distracted driving
Lane departure warning systems can prevent many accidents, but they are not a license for inattentive driving. In order for the technology to work, the system must, above all, correctly recognize the road markings. Most vehicles display the function of the assistant in the instrument cluster – as long as this indicator light is not lit, the assistant does not work. But even if all requirements are met, the systems do not detect every unintentional lane change. Many lane departure warning systems stop working, especially after repeated intervention.
Even with the assistant on board, the driver's full attention is required. If the computer accidentally countersteers, you can always override it with a little force.
