1. An imaging system for a vehicle comprising: an imaging device having a field of view exteriorly and forward of the vehicle in its direction of travel, said imaging device being operable to capture images representative of the exterior scene in the forward field of view; and an image processor operable to process the captured images in accordance with an algorithm, said algorithm comprising a sign recognition routine and a character recognition routine, said image processor processing the captured images to detect signs in the field of view of said imaging device, said image processor applying said sign recognition routine to the captured images to determine a sign type of the detected sign, said image processor being operable to apply said character recognition routine to the captured images to determine information on the detected sign, said image processor applying said character recognition routine to the captured images in response to an output of said sign recognition routine being indicative of the detected sign being a sign type of interest.