Understanding ADAS: Lane Keep Assist

lane keep assist

Noticed an LKAS light on your dash? LKAS, or Lane Keep Assist is a vehicle safety technology that aims to prevent unintentional lane departure crashes. From 2014 to 2018, Lane Keep Assist went from being almost unheard of to being available on 23% of new passenger vehicles in the United States. Five years later, it’s available (standard or optional) on the majority of passenger vehicles in the country.   

In this article, we will explain what Lane Keeping Assist is and how it works, tell how it differs from similar lane control systems, provide examples of LKAS on the market, and give advice about proper LKAS calibration.  

What is Lane Keep Assist? 

What does LKAS mean in a car? Lane Keep Assist, or LKAS for Lane Keeping Assist System, is an advanced driver assistance system (ADAS) that helps keep cars in their lane. When a car with LKAS begins to leave its marked lane, an audible, visual, or haptic lane departure warning (LDW) is initiated. Next, the Lane Keep Assist system takes over, providing steering and sometimes braking to safely move the vehicle back into the lane to prevent deadly crashes.  

But, what does LKAS mean for drivers? When you are driving on a highway and get distracted, it means that your car can help keep you in your lane. And, if you do leave your lane, you spend less time out of it. Drivers seem happy with LKAS. Seventy-four percent of owners in a Consumer Reports survey with LKAS on their vehicles report being very satisfied with their Lane Keeping Assist system. What’s more, 35% even said that their LKA system helped to avoid a crash.  

How does Lane Keep Assist work? 

Designed for highway driving, Lane Keep Assist uses windshield-mounted, forward-facing cameras to watch for and track both dots and other lane markings — starting at about 40 mph, varying by model. Lane Keep Assist is specifically engineered to ensure that the vehicle maintains its lane position by gently steering the car back into the center of the lane if it begins to drift without signaling. This feature of Lane Keep Assist enhances driver safety and comfort, particularly on long journeys where driver fatigue can set in. Lane Keep Assist also functions seamlessly with other safety features, providing an integrated safety system that supports the driver in maintaining proper lane discipline throughout the drive.

Rather than just alerting you, as lane departure warning does, Lane Keep Assist steers to keep you in your lane. How does this work? LKA systems use either one or two forward camera sensors. These cameras track lane markings ahead of you. When you begin to drift out of your lane, as calculated by LKAS sensors, you get a warning and a nudge via steering.  

LKAS is easily deactivated via a slight pull of the wheel and won’t activate when your turning indicator is on.  

Lane Keep Assist vs. Lane Departure Warning vs. Lane Centering 

Industry-wide ADAS naming is complicated. Each automaker has its own naming conventions to describe systems with varying capabilities. Nevertheless, there are three basic types of advanced driver assistant systems that deal with lateral movement and unwanted lane departures: 

  1. Lane Departure Warning (LDW) — An ADAS that warns drivers when they begin to leave their lane when the blinker is not on. Most basic lane ADAS. Just an alert/warning. Driver must provide any braking or steering.  
  1. Lane Keep Assist (LKA, LKAS) — An ADAS that steers you back into your lane when you begin to leave your marked lane. LKA builds upon LDW, steering you back into your lane when you don’t immediately react to LDW’s alerts.  
  1. Lane Centering — Also called lane tracing, this ADAS continuously provides adaptive steering to keep you aimed toward the center of your lane. Often used in tandem with ACC for a semi-autonomous feel on highways. (a level 2 on the (0-5) autonomous scale).  

Lane Departure Warning vs. Lane Keep Assist

Both LKAS and LDW are ADAS features that help keep drivers in their lane and when a departure does occur, minimizes the time outside the lane. Lane departure warning uses sensors to tell when you are starting to leave your lane. LDW provides driver alerts. If the driver doesn’t react quickly, the LKA system steers you back into your lane.  

Lane Keep Assist vs. Lane Centering 

Both are ADAS features that provide drivers with steering assistance based on sensor data. The difference lies in when and how they work.  

ADAS Lane Centering continually, proactively steers toward the center of your lane, whereas Lane Keep Assist is only activated once you start to drift out of your lane and fail to respond to the LDW warnings. Lane centering is proactive and LKA is more reactive.  

That’s the gist. And, while it’s easy to prescribe labels, few auto manufacturers’ lane assist systems fall neatly under just one label. It’s likely for there to be more blurred lines between these three systems in actual practice, especially between Lane Keep and Centering. It’s more of a spectrum between these two.  

4 Examples of Lane Keep Assist and Lateral Support ADAS 

These days, most automakers offer new vehicles with some sort of Lane Keep Assist system, though it likely goes by some other variation of the name. Each automaker has its own spiel and each system, though similarly named, can work very differently.  

To help you spot cars with lane keeping assistance, here are a few examples of OEM lane assist systems. You will notice that they all work a little differently, but all provide steering assistance, though some are closer to traditional LKAS, others are closer to lane centering on the spectrum. Read on to learn more.  

Subaru Lane Keep Assist and Sway Warning 

Subaru’s ADAS suite, called EyeSight, uses two windshield-mounted cameras and includes LDW, LKA, and what it calls Sway Warning. Subaru describes how these features work together, like this:  

“To help you stay safely in your lane at all times, EyeSight features Lane Departure and Sway Warning with Lane Keep Assist. As you’re driving, it watches for lane markings to detect if you’re drifting. Lane Departure Warning can alert you before you leave your lane without signaling. And with Lane Sway Warning, EyeSight can alert you if you begin to sway. If you don’t correct quickly enough, the Lane Keep Assist feature can even intervene and help steer you back in.”  

Honda Lane Keep Assist System 

Honda’s LKAS is more like lane centering. From the Honda Sensing ADAS suite of features, Honda describes its LKAS system like this:  

“Honda’s Lane Keeping Assist System, LKAS, is designed to make driving more convenient by helping to keep your vehicle in the middle of a detected lane and provides alerts if the vehicle is detected drifting out of its lane. LKAS uses a windshield-mounted camera to detect lane markings and employs the Electronic Power Steering to help guide the vehicle to the middle of the detected lane.”  

Mazda Lane Keep Assist 

With Mazda’s Lane Keep Assist, you can have it both ways. Here’s how Mazda explains its multi-pronged Lane-Keep Assist System

“Mazda’s Lane-Keep Assist System (LAS) promotes safer driving by providing appropriate steering assistance. The system allows drivers to choose between Lane-Trace, which provides steering assistance early in order to help keep the vehicle centered in the lane and Lane Departure Avoidance, which only comes into play if the vehicle begins to leave its lane. LAS uses a windshield-mounted camera to recognize lane-markings on the road and activates at speeds above 60 km/h. 

When Lane Departure Avoidance is selected, the system works to prevent unintentional lane departures due to driver inattention. If the system predicts that the vehicle is about to stray from its lane, it provides steering assistance to return the car toward the center of the lane. 

When Lane Trace is selected the system reduces the burden of driving by providing continuous steering assistance to help keep the vehicle centered in its lane. On bends, the systems help the driver to drive more safely by guiding them toward a steering angle that matches the curvature of the road. Lane Trace is achieved simply by having LAS provide steering assistance from an earlier stage than with Lane Departure Avoidance.” 

Toyota Lane Departure, Steering Assist, and Lane Tracing 

Part of the Toyota Safety Sense 2 suite, lane tracing assist is available on many new Toyota vehicles. Toyota’s system is meant to automatically work when Dynamic Radar Cruise Control, its version of adaptive cruise control, and Lane Departure Alert with Steering Assist are enabled and active. Lane Tracing makes “constant steering inputs” to keep your vehicle centered in the lane.  

Today, most new cars either come with lane departure prevention standard or provide it as an optional safety package upgrade. However, not all lane keeping assist systems provide the most satisfying experience for drivers. In a recent Consumer Reports survey covering 72,000 vehicles with ADAS systems in model years 2015-2019, the most satisfying lane keeping assist systems came from Cadillac, Genesis, Kia, and Tesla. The least satisfying LKA experiences were from brands Acura, Audi, Honda, and Lincoln.  

LKAS & Automation 

Lane Keep Assist systems all vary and some LKAS are better than others. No matter the type of lateral support (LKAS, lane centering, or LDW), it doesn’t mean you have an autonomous vehicle. Reactive LKAS doesn’t fall within the parameters of SAE’s driving automation classifications. This is because it isn’t performing on a “sustained basis, but rather provide momentary intervention during potentially hazardous situations,” as SAE puts. They are considered automated functions and don’t change or eliminate the driver’s role. On the other hand, because of its sustained basis, lane centering is a Level 1 Automation.  

Here’s where things get interesting. Add adaptive cruise control to the lane centering, and your vehicle moves up to Level 2 automation. In Level 2, vehicles can provide both steering and braking/acceleration, constantly affecting your lateral and forward movement. However, even at Level 2 (out of 0-5), these features are still driver support features rather than automated driving features by SAE. This means that, as SAE puts it, “You must constantly supervise these support features; you must steer, brake or accelerate as needed to maintain safety.” Level 2 is still the highest automation level available in production vehicles in the U.S.  

LKAS Limitations 

As they are today, lateral advanced driver assistance systems improve safety. LKAS has the potential to save the most lives, because it impacts some of the deadliest types of crashes. They are estimated to impact 1.12 million crashes and save over 20,000 lives annually. However, LKA systems aren’t infallible. Even with active lane centering or lane tracing, constant supervision is necessar. This is due to a variety of potential issues you might encounter. Several things limit how well LKAS works, including:  

These limitations mean that even Level 2 active driving systems have been deemed “not capable of sustained vehicle operation without constant driver supervision” by American Automobile Association (AAA) Foundation for Traffic Safety. In fact, the same research found that during naturalistic evaluations, an issue with Level 2 Automation, primarily from LKAS, happened once every eight miles, highlighting the need for drivers to be actively driving.  

Another limitation of LKAS, LDW, and Lane centering alike is that drivers are somewhat reluctant to use them. The likely culprit is false positives, which routinely require drivers to ignore lane departure warnings or override steering support. In an IIHS study, many drivers (49%) had their lane maintenance system turned off. Additionally, drivers have a harder time with trusting lane centering than systems that control distances like ACC. 

LKAS Calibration 

If you noticed that your Lane Keep Assist system starts prematurely, doesn’t engage soon enough, or isn’t working the way it used to, you may need calibration. 

Lane keeping systems rely on ADAS sensors for information about the world. Sensor alignment has a large impact on the LKAS system, driver experience, and driving performance. Like most ADAS sensors, forward-facing sensing cameras need to be calibrated professionally. When something happens to affect their alignment, like collisions, suspension and alignment changes, and even windshield replacement. Your LKA system won’t always know when it needs calibration. The safety features simply do not protect as they were engineered. 

ADAS Calibration Technology & Services 

At Car ADAS Solutions, we provide a turn-key solution to help you open and operate ADAS calibration centers. Through our unique partnerships with ADAS industry leaders, we help take the unknown out of implementing ADAS calibrations. We offer site certification, ADAS technician training, management software and ongoing support.  

Need a solution for ADAS calibrations? Consider owning your own calibration center.  

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