1. An imaging system for a vehicle, said imaging system comprising: an imaging sensor, wherein said imaging sensor comprises a two-dimensional array of light sensing photosensor elements, and wherein said imaging sensor has a rearward field of view when mounted at the vehicle; a display device for displaying images representative of image data captured by said imaging sensor; and wherein said imaging system generates a plurality of graphic overlays on said displayed images to enhance the driver's cognitive awareness of an object rearward of the vehicle, said graphic overlays comprising a plurality of graphic overlay segments, said graphic overlay segments conveying three dimensional information to a person viewing said displayed images and said graphic overlays.