Driver inattention and poor judgment are the major causes of motor vehicle accidents (MVA). Extensive research has shown that intelligent driver assistance systems can significantly reduce the number and severity of these accidents. The driver's visual perception abilities are a key factor in the design of the driving environment. This makes image processing a natural candidate in any effort to impact MVAs. The vision system described here encompasses 3 major capabilities: (i) Lane Departure Warning (ii) Headway Monitoring and Warning (iii) Forward Collision Warning. This paper describes in detail the different warning features, the HMI (visual and acoustic) application design rules, and results of a study in which the system was installed in a commercial fleet and passenger vehicles.