1. Autos
Send to a Friend via Email

Your suggestion is on its way!

An email with a link to:


was emailed to:

Thanks for sharing About.com with others!

You can opt-out at any time. Please refer to our privacy policy for contact information.

What Are Lane Departure Warning Systems?


What Are Lane Departure Warning Systems?

Systems like Audi Active Lane Assist are able to provide corrective action whenever a vehicle begins to drift.

Image © Audi of America

Lane departure warning systems are a group of safety technologies that that are primarily designed to prevent high speed accidents on highways and freeways. There are a few different types of lane departure warning systems, and some of them are more proactive than others. By warning the driver, or even taking automatic corrective actions, these systems are able to prevent many collisions and run-off-road accidents.

How Do Lane Departure Warning Systems Work?

There are two primary types of lane departure systems. The first type is typically referred to as a Lane Departure Warning (LDW) system. These systems monitor the lane markings on the roadway, which allows them to sound an alarm whenever a vehicle starts to deviate from its lane. The driver can then take corrective action, which can prevent a run-off-road accident or a collision with another vehicle.

The other type of lane departure warning system is more proactive, so it is often referred to as a Lane-Keeping System (LKS), Lane-Keeping Assist, or other similar name. These systems also monitors lane markings, but they are capable of taking corrective action. If the driver doesn’t respond to an initial warning, a Lane-Keeping System can typically take action to keep the vehicle from drifting.

Early lane departure warning systems used single video cameras to monitor lane markings, but modern systems that use visual information typically use video cameras. Other modern systems use laser or radar sensors instead.

The methods that these systems use to provide corrective actions also differ from one situation to another. Some of the first lane-keeping systems made use of electronic stability control systems to keep a vehicle in its lane. This was accomplished by applying a slight braking pressure to the appropriate wheels. Modern systems are able to tap into power steering controls to actually provide a gentle steering correction.

What’s the Point of Lane Departure Warning Systems?

According to the National Highway Transportation Administration, about 70 percent of all single-vehicle highway fatalities in the United States occur in run-off-road accidents. Since run-off-the-road accidents occur when a vehicle leaves its lane and drives off the roadway, lane departure warning systems have the potential to help prevent many fatal accidents.

How Do I Use a Lane Departure Warning System?

If your vehicle has a lane departure or lane-keeping system, it’s a good idea to figure out which type you have. Since these two categories of lane departure systems offer different levels of protection, it’s important to know which one you’re dealing with. It’s also vital to understand the limitations of these systems.

Vehicles that are equipped with an LDW system will issue a warning if your vehicle starts to drift out of its lane. If you’re familiar with the audible warning, or looking for the visual cue on your dash, you’ll be able to take corrective action to prevent an accident.

If your vehicle is equipped with Lane-Keeping Assist, you have an additional layer of protection. However, these systems are not an excuse for distracted driving. They are able to provide small amounts of corrective braking or steering, but it’s still vital to remain aware of your surroundings whenever you’re on the road. It might seem like a car equipped with LKA and adaptive cruise control can drive itself, but technology is still a poor substitute for an alert driver.

What Are the Limitations of Lane Departure Warning Systems?

Modern lane departure warning systems are more reliable than earlier iterations of the technology, but even the most advanced examples have limitations. These systems often rely on visual information to track the relative position of a vehicle within its lane, so anything that obscures the lane markers will render the technology useless. That means you usually can’t rely on your LDW or LKS in heavy rain, snow, or if there is excessive glare from the sun.

Turn signals can also shut down your lane departure or lane-keeping system. These systems are all designed to shut off if a turn signal is activated, which prevents the technology from fighting you whenever you change lanes. If you accidentally leave your turn signal on after changing lanes, the system will remain dormant.

  1. About.com
  2. Autos
  3. Car Tech
  4. Safety Tech
  5. Beyond Safety: ADAS, Convenience, and Comfort Tech
  6. What Are Lane Departure Warning Systems?

©2014 About.com. All rights reserved.