Lane Keep Assist is a forward-camera-based safety feature that steers the car back into its lane when you drift out without indicating. Distinct from Lane Departure Warning (which only warns) and Lane Centring (which keeps the car constantly in the middle of the lane). Standard on most UK cars from 2018 onwards, and now required on new car types under UK vehicle safety law.
Lane Keep Assist (LKA) is the system that actively steers the car back into its lane when you drift across a line without indicating. A forward-facing camera mounted behind the windscreen watches the road markings, calculates the car's position relative to them, and applies a brief steering correction when you cross or drift. Some platforms also vibrate the steering wheel as a warning.
Three terms get muddled. They're related but distinct:
New car types sold in the UK now have to carry at least LDW + LKA as standard under UK vehicle safety law. Lane Centring is usually a premium option, though it's becoming more common.
LKA is camera-based. Almost universally, the camera sits behind the windscreen near the rear-view mirror, looking down the road through the upper portion of the glass.
The camera reads two things: the position of the white or yellow lines marking the edges of your lane, and the position and trajectory of your car relative to those lines. When the camera detects that you're about to cross a line without an indicator, the steering system applies a brief corrective input through the electric power steering motor.
The correction is intentionally light. LKA doesn't fight the driver. Hold the wheel firmly and the input is overridden. Indicate before changing lanes and the system stays out of it. Drift unintentionally without an indicator and the steering nudges you back.
This is also why LKA is the more controversial ADAS feature among UK drivers, particularly on narrow rural roads where intentional lane positioning (passing parked cars, hugging the inside of a bend) can trigger false corrections.
Light on the road matters. LKA struggles when lane markings are faded, when night driving exposes only one edge of the lane, when heavy rain reduces camera contrast, and on roads with no markings at all (rural single-carriageway, residential streets). In these conditions most systems disable themselves automatically and flash a 'Lane Assist Unavailable' message.
Lane Keep Assist depends on the forward camera being aligned to a precise reference. Anything that disturbs the camera, the windscreen it sits behind, or the bracket holding it triggers a need for recalibration.
Most common triggers in our network:
The symptom is usually 'Lane Assist Unavailable' or 'Lane Departure Warning Fault' on the instrument cluster. See our Lane Assist fault guide for the make-specific naming.
No. Lane Departure Warning (LDW) only warns the driver when the car drifts out of its lane (beep, dashboard symbol, sometimes a seat vibration). Lane Keep Assist (LKA) adds active steering input that briefly nudges the car back into its lane.
Most modern cars carry both as standard, with each system's activation thresholds set by the manufacturer (typically from around 35 to 40 mph upwards for the active steering function).
On narrow rural roads or when passing parked cars, intentional lane positioning can trigger LKA corrections, which is the most common complaint. The system is calibrated for motorway and dual-carriageway lane discipline, where staying centred matters most. Most cars let you adjust LKA sensitivity in the driver-assist menu, or turn it off temporarily through a steering-wheel button.
Not in the self-driving sense. LKA only applies brief corrective inputs when the car drifts without an indicator. The driver has to keep hands on the wheel and remain in control.
Lane Centring (a separate, higher-tier feature) holds the car continuously in the centre of the lane but still requires hands on the wheel on UK roads. Hands-off systems like Ford BlueCruise are available on a few cars but only on approved motorway stretches.
Usually one of three reasons. Speed too low: most systems only engage above 35-40 mph. No or faded lane markings: the camera needs visible lines on both sides. Poor visibility: heavy rain, snow, fog, or low sun glare can all disable the system temporarily. If the warning persists in normal conditions after a windscreen or front-end repair, the system likely needs recalibration.
If your car has a forward-facing camera mounted behind the windscreen (and most cars since 2018 do), then yes. The camera that powers LKA is the same camera that powers forward collision warning and most lane-departure features. Recalibration after the new glass is fitted is part of the £199 windscreen calibration tier.
The calibration certificate confirms LKA, LDW, AEB and any other windscreen-mounted system is back within tolerance.
If the warning hasn't cleared after a windscreen swap or interior trim work, head to the homepage form. We come back with the calibration tier, the nearest accredited workshop, and the soonest available slot.