What is lane departure warning?

Developed to combat fatigue and driver distraction, lane departure warning is a camera-based system that monitors a vehicle's position within its lane by ‘watching’ the line markings.

If the system detects the vehicle wandering towards the edge of its lane, it triggers a warning – visual, audible, haptic – to get the driver to intervene and put it back on the right path.

Lane departure warning is the first step towards autonomous vehicles, but in its current state is relatively crude and can only warn the driver that something is wrong.

The warnings can be a beeper or buzzer, a haptic system which produces a rumble through the steering wheel similar to running over cats-eye lane dividers or a buzz through the driver’s seat, as in the case of the Holden Equinox, or a combination. Most also display a visual warning in the instruments or head-up display.

Prestige brands, such as Jaguar Land Rover, use a graphic display in the instrument binnacle to let the driver know when the system is fully operational, or when it can't identify the line markings – either the centreline or the line on the shoulder of the road. This icon resembles a vehicle on a road in perspective with centreline and shoulder marking displayed in green when both are visible to the system, or in white or grey if the system is unable to distinguish either or both from the video capture of the road ahead.

In the event the driver has actuated the indicator to change lanes, the lane departure warning system is disabled for the duration of the manoeuvre.

Lane departure warning systems should not be confused with other examples of driver-assist technology, such as blind-spot monitoring, cross-traffic alert or forward collision warning. And although lane departure warning is an integral part of lane keep assist technology, lane keep assist is an altogether more sophisticated type of safety feature.