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A lane departure warning system (LDW) is a mechanism designed to warn a 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.
The first production LDW system in Europe was the system developed by Iteris for Mercedes Actros commercial trucks. The system debuted in 2000 and is now available on most trucks sold in Europe. In 2002, the Iteris system became available on Freightliner trucks in North America. In Japan, Mitsubishi Fuso implemented the system in 2007. In all of 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. If a turn signal is used, no warnings are generated.
The first passenger vehicle system available in North America was the system jointly developed by Valeo and Iteris for Nissan Motors and is fitted as an option to their Infiniti FX and Infiniti M vehicles. In this system, a camera mounted in the overhead console above the mirror monitors the lane markings on a roadway. A warning tone is triggered when the vehicle begins to drift over the marking to alert the driver who may, for example, be feeling drowsy or distracted.
In 2008, Infiniti will offer a new version of this feature, which it calls the Lane Departure Prevention (LDP) system. This feature will utilize the vehicle stability control system to help assist the driver in maintaining lane position by applying gentle brake pressure.
In Europe CitroĆ«n first offered LDW on their 2005 C4 and C5 models, and now also on their C6. This system uses infrared sensors under the front bumper to monitor lane markings on the road surface. A vibration mechanism in the seat alerts the driver of deviations.
In 2006, Lexus introduced a multi-mode Lane Keep Assist feature which utilizes multiple stereocameras, infrared sensors, along with object and pattern recognition processors. On the Lexus LS, this system allows the vehicle to issue audiovisual warnings and apply corrective steering responses to steer the vehicle back to its lane.
In 2007, General Motors introduced Lane Departure Warning on its 2008 model year Cadillac STS, DTS and Buick Lucerne models. The General Motors systems warn the driver in much the same way Infiniti started, with an audible tone and a warning indicator in the dashboard. Also in 2007, BMW introduced Lane Departure Warning on the 5 series and 6 series using a vibrating steering wheel to warn the driver of unintended departures. Finally Volvo introduced the Lane Departure Warning system along with the Driver Alert Control on its 2008 model year Volvo S80 and on the new Volvo V70 and XC70 executive cars. Volvo's lane departure warning system uses a camera to track road markings and sound an alarm when drivers depart their lane without signaling.
The systems used by BMW, Volvo, Cadillac and Buick are based on technology from Mobileye. An aftermarket (retrofit) version of the technology that combines Forward Collision Warning (FCW), Lane Departure Warning (LDW) and Headway Monitoring (HWM) became available in 2006.