Tech’splaining: What is Lane Keeping Assist and How Does It Work?

  • Christian Wardlaw has 25 years of experience serving in automotive editorial leadership roles with Autobytel, Edmunds, J.D. Power, and Tribune Publishing. A married father of four, Chris is based in the Los Angeles suburbs and believes fuel cell electric vehicles will power the future.

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Distracted drivers kill nine people and injure more than 1,000 every single day of every single week. That sobering statistic comes from the Centers for Disease Control and Prevention (CDC), and includes any type of distraction from daydreaming to text messaging.

Lane keeping assist systems can help when a driver is distracted. Typically, there are three different lane-keeping technologies, and not every vehicle equipped with lane keeping functions will include all of them:

  • Lane departure warning
  • Lane keeping assist
  • Lane centering assist

Lane departure warning and lane keeping assist are commonly paired together, while lane centering assist works separately in conjunction with adaptive cruise control.

Often a driver can program how sensitive they are to lane wander, the type of alert they issue, and how urgent that alert is. The subtler the alert and steering intervention, the more likely a driver is to keep these functions turned on rather than off.

What is Lane Departure Warning?

Subaru EyeSight Lane Departure Warning System
Lane departure warning systems issue visual, audible, or tactile alerts that your vehicle is unintentionally departing from the intended lane of travel. (Subaru)

 

Lane departure warning alerts a driver that he or she is leaving the lane of travel. If the driver signals a lane change, the lane departure warning system won’t alert the driver. If the driver makes a lane change without signaling, an alert will likely occur.

Drivers can often program a lane departure warning system to personal preferences:

  • Early, immediate or late warnings
  • Audible, visual, or tactile alert styles
  • How urgently the technology issues the alerts

For example, using the driver information system, you can set lane departure warning to alert you before you cross the lane markings, at the same time you’re crossing them, or shortly after you’ve crossed them. You can choose between a visual alert showing in the instrument cluster or head-up display, an audible alert, or a tactile alert that is usually a vibration through the steering wheel or the driver’s seat. You can determine whether you want alerts to be obvious or subtle.

Another option is to turn off the lane departure warning system. This is common when system alerts are loud and frequent, which is why tuning the settings to personal preference is so important.

What is Lane Keeping Assist?

Ford Explorer Co-Pilot360 Lane Keeping Assist
Lane keeping assist systems will steer or brake in order to nudge your vehicle back toward the center of the intended lane of travel, preventing an unintended lane departure. (Ford)

 

Lane keeping assist nudges a vehicle that is drifting out of its lane back into the intended lane of travel. This technology is frequently, but not always, included when a vehicle has a lane departure warning system.

To prevent the vehicle from drifting out of the lane, the steering makes a small correction or a small degree of braking force is applied to the front wheel opposite of the one about to drift out of the lane. When the correction occurs, the driver must center the vehicle in the lane of travel.

If the driver fails to center the car, it will drift to the opposite side of the lane where the lane keeping assist will once again steer or brake to prevent a lane departure. At this point, the car is essentially bouncing between the lane markings. Ultimately, without driver intervention, the angle of lane departure becomes too severe and the lane keeping assist system cannot prevent the vehicle from leaving the lane.

What is Lane Centering Assist?

2020 Ford Explorer Co-Pilot360 Lane Centering Assist System
Lane centering assist works with adaptive cruise control to center your vehicle within the intended lane of travel by making small steering adjustments. (Ford)

 

Available only in vehicles with adaptive cruise control, lane centering assist continually attempts to center a vehicle in the lane of travel. The idea is to make long-distance travel easier and less fatiguing.

Cadillac Super Cruise technology is the only adaptive cruise control and lane centering system that can be used, hands-free, for extended periods of time. Cadillac recommends the use of Super Cruise only on freeways and divided highways. I know. You thought Tesla’s Autopilot was the most advanced system available. As this article is written, Autopilot is not as capable as Super Cruise.

Other adaptive cruise control and lane centering assist systems are less capable than Super Cruise, but can still allow for short periods of hands-free driving. Depending on the vehicle, the warning to put your hands back on the steering wheel could come in just a few seconds, or as long as a minute later.

Some lane centering systems work in subtle fashion; you’re barely aware that they’re operational. Others are too aggressive in their quest, causing a driver to fight to override their constant steering corrections, which creates unpleasant ride motions for passengers.

How do Lane Keeping Assist Systems Work?

Subaru EyeSight Cameras Mounted Behind Windshield
Lane keeping systems depend on a camera or pair of cameras to see road markings ahead. Snow, mud, weather, and bright light can affect their ability to see lane markings – provided they exist in the first place. (Subaru)

 

Lane keeping systems use a camera to monitor lane markings. It is usually mounted behind the windshield opposite of or near to the rearview mirror. Based on what the camera sees, the lane keeping systems issue alerts, makes corrections, or centers the vehicle in the lane.

Because these technologies are camera-based, visibility is critical to proper operation. If snow, or mud, or another obstacle is blocking the camera, the lane keeping systems won’t work. Likewise, if snow, or mud, or another obstacle is covering the lane markings, the system won’t work.

Lane markings are necessary for lane keeping assist systems to work properly. If they’ve been scraped off by snowplows, or have faded into obscurity, or you’re driving through a construction zone with fresh unmarked blacktop, don’t expect the lane keeping system to work.

Sometimes, driving into bright sunlight can cause lane-keeping systems to deactivate, or down a sun-dappled road where light and shadows can make it hard for the camera to see lane markings. Rain and fog can also impact a lane keeping assist system’s ability to see the road markings.

In other words, lane departure warning, lane keeping assist, and lane centering assist are not substitutes for an attentive driver. Rather, they are safety nets during moments of distraction.


About the Author

  • Christian Wardlaw has 25 years of experience serving in automotive editorial leadership roles with Autobytel, Edmunds, J.D. Power, and Tribune Publishing. A married father of four, Chris is based in the Los Angeles suburbs and believes fuel cell electric vehicles will power the future.

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