Guide to Lane Departure Warning and Lane Keeping Assist

Both of these advanced safety features help prevent drivers from veering out of their lane.
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Lane-departure warning (LDW) and lane-keeping assist (LKA) are advanced driver assistance technologies that help prevent drivers from straying out of their lane. Although they sound similar and are often paired together, these systems operate differently — LDW only warns drivers while LKA physically steers drivers back into their lane.

Studies show that the deadliest car collisions occur due to lane departures or drivers veering off of the road. Lane-assistance systems like LDW and LKA can help drivers avoid accidental lane departures and reduce the occurrence and severity of some collisions.

How lane-departure warning and lane-keeping assist work

LDW alerts you with a flashing light, audible warning or vibration, when your vehicle touches or crosses side or center lane markers. The safety feature uses a front-facing camera located near the rearview mirror to detect lane markers around your car. To this end, the system will only work when lane markers are clearly painted and will not typically recognize road curbs. Keep in mind that most LDW systems are not activated when your turn signal is on.

LKA is a more advanced version of LDW. Like LDW, LKA uses a front-facing camera to identify lane markers. But unlike LDW, LKA engages the wheel to steer a car back to the center of the lane if a driver doesn't respond to the lane-departure warning.

Some cars combine LDW and LKA technology to alert as well as assist drivers. These lane systems usually operate automatically, but drivers can manually turn them off via a button usually located near the front dashboard or the steering wheel.

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Lane-centering assist (LCA) is another advanced lane-assistance system. It uses cameras to detect center and side lane markers and automatically adjusts the steering wheel to keep a vehicle centered in the appropriate lane.

What to know about lane-departure warning and lane-keeping assist

LDW and LKA function optimally on highways. In fact, some systems only work above certain speeds. Additionally, because these systems rely on cameras to detect lane markers, they might not work when lane markers are faded, poorly painted or obstructed in some way, as by snow or dirt.

Most new cars come with advanced lane-assistance systems like LDW and LKA. And while most automakers use the standardized names for these systems, some use slightly different branded names. For example, BMW refers to the LKA and LDW features as Active Lane Keeping Assistant, while Toyota calls it Lane-Departure Alert with Steering Assist.