What it does
Lane departure warning alerts you as a wheel nears the line without the turn signal on. The alert may be a chime, a symbol, a buzz through the seat or a vibration in the steering wheel.
Lane keeping assist goes one step further and applies a small steering correction, or brakes one side of the car, to ease you back inside the line.
Lane centering steers continuously to hold the middle of the lane. It is usually paired with adaptive cruise control, and it still expects your hands on the wheel.
How it senses
A camera behind the windshield looks for painted lane lines and, on some cars, the edge of the road. A sensor in the steering column, or a touch-sensitive rim, checks that your hands are on the wheel.
What sets it off
Drifting toward a line at or above the system’s minimum speed with no turn signal on. Using the signal tells the car the move is deliberate, and it stays quiet. If you take your hands off the wheel, lane centering will warn you, then usually switch itself off.
Where it stops
- Worn, faded or missing paint, and lines covered by snow, water or glare.
- Construction zones, where old and new markings cross each other.
- Sharp curves and narrow lanes, where the correction it is allowed to make is not enough.
- Speeds below the minimum, which on many cars rules out town driving.
- None of these features makes the car self-driving. They can switch off without much warning when they lose the lines.
Check for your car
- Which of the three features your car has. The names vary by maker, so read the description, not the badge.
- The speed it starts working at.
- How it tells you it can see the lines. Often a green or white lane symbol means active and a grey one means standing by.
- How to switch between warning only and steering help.
This guide describes how the system generally works. Makers tune and name their systems differently, so your owner’s manual is the final word for your vehicle.
Next guideBlind Spot Monitoring
