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In road-transport terminology, a lane departure warning system 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 lane departure warning system in Europe was the system developed by America's 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' trucks in North America. 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.

More effective lane departure warning systems are now combining prevention with risk reports in the transportation industry. Viewnyx applies video based technologies to assist fleets in lowering their driving liability costs. Firstly, by addressing the main causes of collisions: driving error, distraction and drowsiness. Secondly, by providing Safety Managers with driver and fleet risk assessment reports and tools to facilitate proactive coaching & training to eliminate high risk behaviors. The Lookout solution is currently being used by North American fleets.

There are two main types of systems:

• 
  
• systems which warn the driver if the vehicle is leaving its lane.
  
• systems which warn the driver and if no action is taken automatically take steps to ensure the vehicle stays in its lane.

[edit] Timeline

2001: Nissan Motors began offering a Lane Keeping Support system on the Cima sold in Japan.^[1] In 2004, the first passenger vehicle system available in North America was jointly developed by Iteris and Valeo for Nissan on the Infiniti FX and in 2005 the M vehicles.^[2] 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. In 2007 Infiniti offered a newer version of this feature, which it calls the Lane Departure Prevention (LDP) system. This feature utilizes the vehicle stability control system to help assist the driver maintain lane position by applying gentle brake pressure to the appropriate wheels.^[3]

2002: Toyota introduced its Lane Monitoring System^[4] on vehicles such as the Cardina^[5] and Alphard sold in Japan, this system warns the driver if it appears the vehicle is beginning to drift out of its lane.^[6] In 2004, Toyota added a Lane Keeping Assist feature to the Crown Majesta which can apply a small-counter steering force to aid in keeping the vehicle in its lane.^[7] In 2006, Lexus introduced a multi-mode Lane Keeping Assist system on the LS 460 which utilizes stereo cameras along with more sophisticated object and pattern recognition processors, this system can issue an audiovisual warning and also using the Electric Power Steering (EPS) steer the vehicle to hold its lane, this system also applies counter-steering torque to help ensure the driver does not over-correct or "saw" the steering wheel while attempting to return the vehicle to its proper lane,^[8] if the radar cruise control system is engaged the Lane Keep function works to help reduce the driver's steering input burden by providing steering torque, however the driver must remain active otherwise the system will deactivate.^[9]

2003: Honda launched their Lane Keep Assist System (LKAS) on the Inspire.^[10][11] 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.^[12] A camera is 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 you're locked into a particular lane, monitors how sharp the curve is and uses factors such as yaw and vehicle speed to calculate what steering input is required.^[13]

2005: Citro?n became first in Europe to offer LDWS 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.^[14]Audi began offered its Audi Lane Assist feature on the A4. This system unlike the Japanese "assist" systems will not intervene in the actual driving rather vibrate the steering wheel if the vehicle appears to be exiting its lane.^[15]

2007: General Motors introduced Lane Departure Warning on its 2008 model year Cadillac STS, DTS and Buick Lucerne models. The General Motors system warns the driver, with an audible tone and a warning indicator in the dashboard. BMW also introduced Lane Departure Warning on the 5 series and 6 series using a vibrating steering wheel to warn the driver of unintended departures. Volvo introduced the Lane Departure Warning system along with the Driver Alert Control on its 2008 model year S80 and on the new 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, and General Motors are based on technology from Mobileye.

2009: Mercedes-Benz began offering a Lane Keeping Assist function on the new E-class.^[16] This system warns the driver with a vibrating steering wheel if it appears the vehicle is beginning to leave its lane. And a new feature will automatically deactivate and reactivate if it ascertains the driver is intentionally leaving his lane, for instance if the driver is aggressively cornering. However this system will not automatically correct the vehicle to ensure it stays in its lane like the Japanese "assist" systems.

FIAT is also launching its Lane Keep Assist feature based on TRW lane detect system. Peugeot introduced the same system than Citro?n in its new 308.