How Lane Departure Technology Works

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 Lane Departure Button/Image Credit: Buick

Lane Departure Technology is designed to warn drivers that their vehicle is about to move out of its lane, unless a turn signal has been activated in the direction that the vehicle is moving. This technology is designed to minimize the chance of an accident, either through driver error, distraction, or drowsiness.

Let’s look at a typical situation: You’re traveling at 65 miles per hour in the middle lane of a three-lane highway. The view is clear ahead, even in the oncoming lanes. You see fire trucks and an ambulance stopped in the oncoming lane, and without ever lifting off of the accelerator, your gaze lingers on the fire apparatus for one or two seconds. Without even realizing it, you’ve applied subtle pressure to the steering wheel, and drifted over into the passing lane, where a car is in your blind spot.

It’s called target fixation, and an article at Cycle World explains it well: “When confronted with…something unusual suddenly appearing in our field of vision, our natural instinct is to look directly at the object posing the threat and exclude everything else. Unable to look away and even consider an escape route, we tend to go where our eyes take us, often directly into the object.”

It’s happened to all of us, and the idea behind Lane Departure Technology is to avoid it.

What Is Lane Departure Technology?

Ford Lane Departure Warning with Lane Keeping Aid/Image Credit: Ford Motor Company

There are three major types of Lane Departure Technology, in increasing levels of intervention:

  • Lane Departure Warning – warning the driver if the vehicle is veering out of its lane with visual, audible, and vibration warnings
  • Lane Keep Assist – warning the driver with audible and visual cues, and if no action is taken, only taking steps such as turning the wheel in the opposite direction to when the vehicle is about to drift out of its lane
  • Lane Centering Assist – actively assisting to keep the vehicle centered in its lane at all times

Your vehicle may have one, two, or all three of these types of technology.

How Lane Departure Technology Works

Lane Keep Assist operates thanks to one of three different types of technology:

  • Video sensors, typically mounted behind the windshield near the rear-view mirror
  • Laser sensors mounted on the front of the vehicle, usually behind the grille
  • Infrared sensors, mounted either behind the windshield or under the vehicle

Any of these sensors feed information to a computer with an algorithm whose only purpose is to detect the lines painted in the road. When the algorithm senses an edge of a lane marker, and that the vehicle is veering too close to it without a turn signal activated, it begins the process of alerting the driver, or taking evasive action.

Does My Car Have Lane Departure Technology?

This technology has been around longer than you might think. It started to appear on INFINITI FX and M vehicles in 2004, using a camera mounted in the overhead console to monitor lane markings. It simply triggered an audible alert when the driver began to drift over into the next lane.

In 2006, Lexus introduced technology on the LS460 that not only issued an audio/visual warning, but through the electric power steering system, could steer the vehicle to keep it in its lane.

In 2007, INFINITI updated the system it first introduced in 2004 to use the vehicle’s stability control system to maintain lane position by gently applying brake pressure to appropriate wheels.

The first American manufacturer to introduce the technology was General Motors, which included Lane Departure Warning on the Cadillac STS, DTS and Buick Lucerne. In the GM system, when the vehicle veered out of a lane, it issued an audible tone, a visual indication on the dash, and a vibration in the seat on side toward which the vehicle was turning.  

In 2012, Mobileye developed the technology to allow Lane Centering Assist, which is truly a Level 2 autonomous technology that will center the vehicle in a lane without input from the driver for a period of time.

The first challenge is figuring out if your car possesses this technology. Manufacturers always love to market their own names for similar technologies, so you may find that your car has this technology under any of these names:

  • GM Brands: Lane Keep Assist with Lane Departure Warning
  • Toyota and Lexus: Lane Keep Assist
  • Honda and Acura: Lane Keeping Assist System (LKAS)
  • Hyundai: Lane Keep Assist
  • Kia: Lane Keeping Assist
  • Nissan: Optimized Lane Assist
  • INFINITI: Lane Departure Prevention
  • Subaru: Lane Departure and Sway Warning, Lane Keeping Assist
  • Volvo: Pilot Assist with Lane Keeping Aid
  • Mercedes-Benz: Active Blind Spot Assist and Active Lane Keeping Assist with brake actuation
  • BMW: Active Lane Keeping
  • Audi: Active Lane Assist

To make this more confusing, all of these technologies may be – and typically ARE – bundled into a suite of safety technologies on any brand’s vehicles. For instance, Lane Keeping Assist is part of the EyeSight package of technologies on many Subaru vehicles. Similarly, Lane Departure Prevention is part of the ProPILOT Assist suite of technologies on many Nissan and INFINITI vehicles.

When Does Lane Departure Technology Not Work?

At the moment, all of this technology requires a clear view of the lane markings to work. Lots of things can cause the technology not to work, including a dirty sensor, unclear lane markings, or debris or snow obscuring the markings.

How To Disable Lane Departure Technology

Subaru Lane Departure Button Image Credit: Subaru of America

We’ve sampled almost every different variation of Lane Departure Technology in mainstream vehicles today, and they all do what they’re supposed to- to a degree. They get a little annoying, though, when you’re traveling the backroads where single lane roads are narrow, and corners make it almost impossible to avoid coming close to the edge of a lane marker.

The good news is, you can turn it off. Though it would be handy if all Lane Departure technology was mounted in the same location in every vehicle, that is not the case. The button to turn off Lane Departure technology can be on the right side of the instrument panel, on the left side of the instrument panel where things like fuel lid or trunk release switches are located, or it can be mounted right on the steering wheel. Check your owner’s manual to find where your switch is located.

It would also be nice if the technology was marked with the same iconography, but you’re out of luck there, too. There are three different basic icons you’ll find that turn the technology off:

The “hands off wheel” icon.

The “car going out of a lane” icon.

The “some variation of acronym” icon.

Some of these switches may have a light to indicate that the technology is on, some may not. They also may have a warning light on the dash when the technology is turned off, but that’s not standardized, either.

It’s also important to keep in mind that some of these switches are “non-latching,” meaning that they revert to their default “ON” position every time you turn the car off.

The most important piece of advice we can give is to read your owner’s manual, and watch any manufacturer-produced videos to understand what the technology does, how it works, and how to turn it on and off.

Like it or not, The National Highway Traffic Safety Administration (NHTSA) estimates that even the least aggressive Lane Departure Warning technology – that which only warns the driver and takes no evasive action – reduces the number of crashes by 26.1 percent, and the number of serious injuries from those crashes by 20.7 percent. This technology is here to stay, so get used to it.

Craig Fitzgerald began his automotive writing career in 1996, at AutoSite.com, one of the first online resources for car buyers. Over the years, he’s written for the Boston Globe, Forbes, and Hagerty. For seven years, he was the editor at Hemmings Sports & Exotic Car, and today, he’s the automotive editor at Drive magazine. He’s dad to a son and daughter, and plays rude guitar in a garage band in Worcester, Massachusetts.

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