📖 The Quick Answer
A forward camera watches the painted lane lines. If the car begins to cross a line without a turn signal, the system alerts the driver. Unlike Lane Keep Assist, LDW does not move the steering wheel. It only warns.
⚙ How It Works (Sensors and Algorithm)
A camera behind the rearview mirror runs lane-line detection at about 30 frames per second. The ADAS computer estimates lateral position and rate of drift. If the car is about to cross a line and the turn signal is off, the system fires a warning, typically a flashing lane icon on the dash, an audible chime, and on some cars a haptic buzz through the steering wheel or seat.
🛡 What It Protects Against
Drowsy-driver lane departures, distracted-driver drifts, single-vehicle run-off-road crashes, and head-on collisions caused by crossing the centerline. IIHS estimates LDW reduces single-vehicle, sideswipe, and head-on injury crashes by about 21 percent.
⚠ Limitations and When It Fails
Faded or missing lane lines, snow or salt covering the paint, construction zones with conflicting paint, sharp curves, and night driving with poor contrast all disable LDW. A dirty windshield in front of the camera disables it entirely. LDW also does not work below a minimum speed (typically 35 to 40 mph).
🚗 Which Vehicles Have It
Bundled with LKA on virtually every new US vehicle since 2019. Common names: Honda Sensing Lane Departure Warning, Toyota Lane Departure Alert (LDA), Subaru EyeSight Lane Departure Warning, Ford Lane-Keeping Alert, Hyundai/Kia Lane Departure Warning, Nissan Lane Departure Warning.
🔧 Related TSBs and Recalls
TSBs typically cover false alerts on grooved concrete and after windshield replacement. After any windshield service the forward camera must be recalibrated.