Lane Departure Warning

How does it work?

Lane departure warning (LDW) systems are those that provide alerts whenever a driver appears (i.e., a turn signal is not activated) to deviate too close to the edges of the lane or partially crosses the lane mark. They are primarily designed to reduce high-speed collisions on roads and highways.

LDW systems are usually composed of visual, audible and/or steering wheel vibrating warnings. LDW-only systems must be differentiated from lane-keeping assistance systems that automatically adjust steering to keep the vehicle in lane. Lane-keeping assistance systems can provide a warning before activating.

Lane departure warning is especially useful for drivers who drive a lot on highways and country roads. It is less useful for city drivers. The type of warning varies among automakers. Some use an alarm sound, while others cause the steering wheel or driver's seat to vibrate, creating the feeling of driving over rumble strips.

Graphic: lane departure warning icon


  • Current systems are compatible with turn signals for lane change, so this action is not a problem for this technology.
  • At this time, studies show that this type of technology represents a clear reduction in motorway collisions.
  • They help keep the driver focused in the event of any distraction. In addition, the lane-keeping assist features can be very useful on long journeys.


  • Lane marking quality (e.g., paint is scraped off by snow plow) and environmental conditions may affect LDW performance to the extent that they affect the system’s ability to identify traffic lanes.
  • Many systems rely on having good, visible road markings, and may not be able to detect an unmarked roadside.
  • Sensors such as cameras can be influenced by environmental factors such as lighting or precipitation.

Common names

  • Lane departure alert
  • Lane departure warning with steering assist
  • Lane departure warning
  • Lane departure warning system
  • Lane departure warning with Lane Keep Assist
  • Lane Keeping Assist with Lane Departure Warning
  • Lane keeping alert
  • LaneSense Lane Lane Departure Warning Plus

Latest Publications on PubMed

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