Lane Departure Warning Systems

Basic Description

Lane departure warning systems monitor the position of the vehicle and warn the driver when the vehicle starts to drift out of its lane (unless the signal is in use or the vehicle speed is below a certain threshold). Unintentional lane departure can be caused by driver distraction, inattention or drowsiness and can result in serious head-on collisions.

These systems generally employ a video sensor that detects lane markings. The camera takes an image of the road ahead of the car during the day or within the headlight beams at night. This visual image is sent to an electronic control unit, where it is analyzed. The lane markings are identified and subsequent changes are recorded. If the vehicle is threatening to stray outside the limits of the lane, the system alerts the driver with an audible alarm and by vibrating the steering wheel. The system takes the vehicle's speed into account, providing a warning earlier when the vehicle is travelling at higher speeds, so the driver has adequate time to correct the steering before the lane markings are crossed.

Lane departure warning systems monitor the turn signal’s status and issue lane departure warnings only when the driver does not use the vehicle’s turn signal in the direction of the lane change. In the most advanced systems, if no action is taken by the driver after the warning is given, torque is applied to the steering wheel by applying braking force to a steerable road wheel of the vehicle causing the car to return to a safe position.

Sensors

Vehicle speed sensor, optica or infraredl image sensor, turn signal sensor

Actuators

Audible warning alarm, steering wheel vibrator, brakes

Data Communications

• Communication with ECM: CAN bus

• Image sensor communication: AV IN*4

• Control Panel (LCD) communication: NTSC/I2C

Manufacturers

Assistware Technology, Continental, Delphi, Denso, Iteris, Mobileye, TRW, Valeo

For More Information

[1] AutoVue, Lane Departure Warning System, Philip Reed, Edmunds.com.

[2] Lane Departure Warning System, Brian Cooley, CNET video.

[3] Lane Departure Warning System, Wikipedia.

[4] Lane Departure Warning Systems(LDWS), FMCSA website, US Dept. of Transportation, July 2005.