Lane departure warning

How this technology works

Lane departure warning systems detect markings on the road and warn a driver if he or she unintentionally leaves their lane without using the turn signal. Most systems use a forward facing camera mounted inside the windscreen by the rear view mirror. When the system finds that the vehicle is leaving its lane without a turn signal, it warns the driver with a warning light on the dashboard or a warning sound. Some systems vibrate the steering wheel or the driver's seat on the side the car is drifting towards.


  • These systems may only operate over limited speed ranges. Most operate at speeds over 60 km/hr
  • Warnings stop if the driver turns on the turn signal
  • Lane departure warning systems can be turned off

Other names for this technology

  • Lane departure system
  • Lane departure alert
As a car drifts off to the shoulder of the road, an alert appears.

As a car drifts off to the shoulder of the road, an alert appears.

Things for drivers to keep in mind

  • The warning system reacts when a vehicle appears to be drifting out of its lane
  • This is a warning system only
  • A lane departure warning systems does not take control of your vehicle or keep you from driving
  • These systems don't work without clear lane markings, on curvy roads, or in inclement weather
  • These systems may have limited operating speed ranges, make sure you know what they are for your vehicle
  • You should read your owner's manual to learn about your vehicle's system, including its capabilities and limits