In road-transport terminology, a lane departure warning system (LDWS) is a mechanism designed to warn the driver when the vehicle begins to move out of its lane (unless a turn signal is on in that direction) on freeways and arterial roads. These systems are designed to minimize accidents by addressing the main causes of collisions: driver error, distractions and drowsiness. In 2009 the U.S. National Highway Traffic Safety Administration (NHTSA) began studying whether to mandate lane departure warning systems and frontal collision warning systems on automobiles.
There are four types of systems: Lane departure warning (LDW): Systems which warn the driver if the vehicle is leaving its lane with visual, audible, and/or vibration warnings Lane keeping assist (LKA/LKS): Systems which warn the driver and, with no response, automatically take steps to ensure the vehicle stays in its lane Lane centering assist (LCA): Systems which assist in oversteering, keeping the car centered in the lane, and asking the driver to take over in challenging situations Automated lane keeping systems (ALKS): Designed to follow lane markings with no human driver.
Another system is the emergency lane keeping (ELK). The emergency lane keeping applies correction to a vehicle which drifts beyond a solid lane marking.
Rationale and method
One of the main causes of single vehicle crashes and frontal crashes is lane departure. The goal of the lateral support systems (LSS) is to help to avoid such crashes.
Without those LSS systems, lane departure can be unintentional; the car drifts towards and across the edge of the lane. The car then reach a potentially dangerous situation. This system does not work when the edge of the lane is not marked by a line.
A lane detection system used behind the lane departure warning system uses the principle of Hough transform and Canny edge detector to detect lane lines from realtime camera images fed from the front-end camera of the automobile. A basic flowchart of how a lane detection algorithm works to help lane departure warning is shown in the figures.
Lane warning/keeping systems are based on: Video sensors in the visual domain (mounted behind the windshield, typically integrated beside the rear mirror) Laser sensors (mounted on the front of the vehicle) Infrared sensors (mounted either behind the windshield or under the vehicle)
In Europe, the lane departure warning system should be compatible with a visible lane marking identification standard such as commission regulation EU-351/2012.
History
The concept and a working model of this technology was invented and fitted to a Rover SD1 in England by British inventor Nick Parish in 1988. Patent application No 8911571.1 was made in 1989.
The first production lane departure warning system in Europe was developed by the United States company Iteris for Mercedes Actros commercial trucks. The system debuted in 2000, and is now available on many new cars, SUVs, and trucks.
In 2002, the Iteris system became available on Freightliner Trucks' North American vehicles. In both these systems, the driver is warned of unintentional lane departures by an audible rumble strip sound generated on the side of the vehicle drifting out of the lane. No warnings are generated if, before crossing the lane, an active turn signal is given by the driver.
2001
Nissan Motors began offering a lane-keeping support system on the Cima sold in Japan.
2002
Toyota introduced its lane monitoring system on models such as the Caldina and Alphard sold in Japan; this system warns the driver if it appears the vehicle is beginning to drift out of its lane.
2003
Honda launched its Lane Keep Assist System (LKAS) on the Inspire. It provides up to 80% of steering torque to keep the car in its lane on the highway. It is also designed to make highway driving less cumbersome, by minimizing the driver's steering input. A camera, mounted at the top of the windshield just above the rear-view mirror, scans the road ahead in a 40-degree radius, picking up the dotted white lines used to divide lane boundaries on the highway. The computer recognizes that the driver is "locked into" a particular lane, monitors how sharp a curve is, and uses factors such as yaw and vehicle speed to calculate the steering input required.