Guide to Lane Departure Warning & Lane Keeping Assist

Along with lane centering assist, these systems sound the same but work quite differently

By Keith Barry

Many new vehicles come with systems that can exert some control over steering. But these features can operate very differently, and drivers are divided on which ones they like. Consumer Reports members who responded to our latest safety survey told us they favor systems that can help ease stress during highway drives, but they don’t love warning systems that can sometimes be startling or too sensitive.

In responses to the CR survey, the owner of a 2020 Toyota Corolla praises its lane centering assist (LCA) for guiding the car between lane lines on long road trips. “This has resulted in less stress in my hands, arms and overall while driving,” they wrote. At the same time, the owner of a 2020 Toyota Camry complained about its overzealous lane departure warning (LDW) system. “I don’t randomly wander around the lanes in the road,” they said. “If I change lanes it is because I intend to, because there is something blocking my lane of traffic, like a bicyclist.”

So what are these systems, and how do they differ?

Lane departure warning (LDW) will provide visual, audible, and/or tactile warnings—such as through steering wheel or seat vibrations—to alert the driver when the car approaches or crosses lane markings. These systems do not intervene when the turn signal is active.

Lane keeping assistance (LKA) gives steering support to assist the driver in preventing the vehicle from departing the lane.

There is another system called Lane centering assist (LCA) that provides automatic steering to continually center the vehicle in its lane. None of these three systems are designed to steer a car without a driver’s input.

All these lane features use forward-facing cameras to detect the lane lines around your vehicle. LDW and LKA are often “linked” so that they are used together in a vehicle. LDW and LKA features are often on by default. If a driver wishes to turn them off, they usually must push a button (featuring a symbol with lane lines and a car crossing a line) or make a selection in a vehicle menu. Meanwhile, LCA is usually activated by a button on the steering wheel, featuring a symbol with lane lines flanking a steering wheel. Many brands require adaptive cruise control to be activated in conjunction with using LCA.

In our survey, we asked CR members to rate their experiences with the advanced safety and driver assistance systems on their model-year 2017 to 2022 cars. Respondents answered questions about their satisfaction with the systems. The survey covered about 47,000 vehicles.

Unlike other advanced safety systems, a very slim majority of drivers said they were “very satisfied” with LDW and LKA. A larger number said they liked LCA. But many respondents indicated that they were confused about how lane systems work, and the differences among multiple, similarly named systems.

What Should Car Buyers Look for in LDW and LKA, and LCA Systems?

The most frequent complaints about LDW systems are that they sound an audible or tactile warning even when a driver is intentionally crossing a lane line.

“I wish the system could sense potholes, objects on the road, pedestrians and bicyclists that are not in your travel lane, but require you to shift [over],” says the owner of a Mazda CX-5. “The lane departure warning and lane keep assist are the only safety features I don’t particularly like about my Forester, simply because they are wrong much more often than they are right,” says the owner of a 2017 Subaru. “I frequently get alerts when I haven’t left my lane, or, for example, when I try to give a large vehicle, disabled vehicle, or bicyclist extra room.” A 2021 Tesla Model Y driver said it “bings at me when I’m departing [a] lane when I am moving over due to [a] biker or runner. Shouldn’t be as sensitive off highways or ideally should see the biker/runner and recognize I am moving over line to give them more room.”

On some vehicles, the complaints involve the warnings themselves, which can be distracting, says Kelly Funkhouser, manager for vehicle technology at CR. “Drivers prefer systems that have a steering wheel or seat vibration over those that have an audible beep,” she says. “However, the steering wheel in many Honda and Acura vehicles shudders so much that it can feel like you’re losing control of the steering wheel.”

The driver of a 2017 Honda CR-V agrees: “When I am passing a vehicle on an expressway and it moves toward my lane, and I react by moving left in my lane, the steering wheel jiggles as a lane departure warning,” they wrote. “I am depending on the wheel to move me away from danger on the right, watching for danger on the left. The jiggling wheel is a dangerous distraction.”

Even though LCA systems are more popular than LDW or LKW, Funkhouser says that different vehicles interpret “centering” very differently. “Some try as hard as they can to keep your vehicle in the dead center of the lane, while others allow drivers to steer smoothly within lane lines to avoid potholes,” she says.

Many drivers report fighting against LCA’s inputs. “We don’t see eye to eye on where I should be in my lane,” a 2019 Subaru Outback driver says. “I often turn it off.”

Some survey respondents expected LKA systems to work more like LCA systems, but that’s not the case. “LKA features are not designed to continuously steer the vehicle,” Funkhouser says. “They are meant to intervene at the last moment before a lane departure occurs to keep the vehicle within its lane.”

LKA, LDW, and LCA systems are only as good as the lines on the road, and they can become confused by multiple markings painted during road construction, lane lines that are faded or covered by snow, markings that suddenly disappear or merge as lanes come together, or if the camera lens is blinded by direct sunlight.

“It responds badly to merge lanes not recognizing loss of lane,” says the driver of a 2019 Chevrolet Traverse.

Ultimately, Funkhouser says that drivers should try these systems out during an extended test drive if they expect to use them, and they should read the owner’s manual to learn about their limitations and idiosyncrasies. “Even though some lane centering systems are quite impressive, they are a convenience system that’s no substitute for staying in control of the vehicle,” she says.

Brand Names for Lane Systems

CR, AAA, J.D. Power, and the National Safety Council have agreed on standardized, specific names for about 20 individual safety systems in order to reduce confusion and improve consumer understanding of what they do. Still, manufacturers often use their own names for these systems. These are some of the names that automakers use or have used.

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