Forward Collision Warning (FCW) systems from TRW use radar-based sensors and cameras to monitor the road ahead. They help provide object recognition and detect relative speeds between the vehicle and an impending object. When the speed of the object is such that it represents a risk of collision, the driver receives an audible, visual or haptic warning.
Camera-based FCW

A forward-looking camera with object recognition capability is mounted on the windscreen behind the rearview mirror. This technology provides a low-cost sensor that is able to provide advanced audible, visual or haptic warnings of potential accidents.  FCW is able to provide additional functions, such as Lane Departure Warning.
Radar-based FCW

A forward-looking 24GHz radar sensor is mounted near the radiator grille at the front of the vehicle. Warning options are the same as those found within the camera-based system. Radar-based FCW features a higher-performance sensor that can measure distance and relative speed directly. This system is also very effective in all weather and lighting conditions.