All About Lane Departure Warning (LDW) Systems

by JRO on September 23, 2013

A lane departure warning system acts as a safety feature that is helpful to drivers. When a driver is about to leave their lane, the LDW system acts by sounding a warning or by creating a vibration that alerts the driver to stay within the lane. Crashes caused by drivers who depart from their designated lanes are often serious. Some crashes are fatal, especially when a car hits a stationary object or rolls over.

There are many things that can cause drivers to veer from their lane.

– Inattentive driving due to distractions like reaching for something, looking away from the road briefly, answering a cell phone, and text messaging.

– Drowsiness from not getting enough sleep, staying out late, or driving while fatigued. This is a common problem for commercial truck drivers and for others who spend a lot of time driving.

– Inexperienced drivers can have difficulty judging where lane marking lines are and how close they are to them. Better judgment comes with experience.

Two Types of Lane Departure Warning Systems

There are two types of lane safety systems. One gives drivers a warning using audible or sensory signals to let them know they are veering from their lane. This is a lane departure warning (LDW) system. The other type physically performs an action, helping the driver to get back into the correct lane position. This is done by automated braking and steering adjustments when it’s determined that a driver has begun to swerve or go out of the lane. This system is often known as Lane Keeping Assist or Lane Keeping System (LKS).

The lane departure warning system can sound an alarm, flash lights on the dashboard, or a start a vibration either in the steering wheel or in the seat, depending on the model of car or the type of detection system that is installed. Systems often work with the help of cameras mounted on the rear view mirror that signal the computer in the car where lane markings are, and when a deflection is made from the lane.

Drawbacks to Lane Departure Warning Systems

There are some drawbacks to these systems. Road conditions, weather conditions, and driver error sometimes cannot be overcome by a LDW system. Things that lessen the system’s effectiveness include:

– Lanes that are not marked well: lightly painted lines or non-existent lines can make a lane departure warning system less useful.

– Weather conditions like snow, ice, mud, rain, or standing water in the roadway all take away from the effectiveness of the system.

– Roads with lower speed limits normally will cause a lane departure warning system to be non-operational.

– Driving through construction areas. Driving where lanes shift, lanes change, and lane markings are either temporary or non-existent will hinder LDW systems. This is when drivers must be sure they are alert and paying attention to lane shifts in the roadway and to lower speeds through construction areas.

– Driver error, like driving for long periods with a turn signal on, can deactivate the lane departure system.

Safe Driving is Always Up to the Driver

No matter what alarm systems or helpful safety systems are found in a vehicle, it’s ultimately up to the driver to operate the car safely. No safety system is a substitute for an attentive, alert, and safe driver.


Myron Pratt is a freelance writer based in Cleveland, Ohio. Fascinated readers looking to learn more about the shipping and transportation industries should check out the resources from Stevens Transport.




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