What does lane keep assist do?

Lane keep assist is a system that gently tries to guide your car back between the lines if it’s about to drift over the lines. The drift is usually caused by distraction, inattention or microsleeps, so lane keep assist is a valuable safety feature that can help prevent you running off the road or causing a head-on crash.

There are two systems that are used:

1. Lane departure warning: this system alerts the driver if the vehicle is crossing the lines with a combination of a sound, visual warning and/or steering wheel vibration
2. Lane keep assist: this system applies a small amount of corrective steering to bring the car back into the lane. If the manoeuvre was intentional, the driver can easily override this.

The bottom right-hand button can be used to turn lane keep assist off. This is useful in areas where there will be a lot of false positives, such as city streets with a lot of old marked lines.

Lane departure systems have a variety of names, depending on the manufacturer offering it, such as lane keeping assist and lane departure warning system.

Combined with radar cruise control a lane keep assist system provides a very low level of autonomous driving; the vehicle may be capable of keeping in a fundamentally straight line in a motorway lane.

Lane keep assist flaws

As the systems rely on cameras they can be defeated by snow, highly reflective wet tarmac, where the lines have been burned off (but not well enough) and where there are a lot of converging or diverging lines. They won’t work on rural B roads with no marked lines or if the cameras are dirty.