The principal road signs on highways and major roads are normed. Their detection and initial treatment essentially resembles that of traffic signs. The problem arises once the written content has to be evaluated. Considerable variations in the size of characters - even within the same road sign - as well as the mixture of symbols and text let it appear advisable to develop subagents responsible for the detection, tracking, and interpretation of road signs.
Experience with address label reading machines suggests that a mere capability to read single characters will not suffice in general. A dictionary of names which may appear on road signs as well as a data base of relations - capturing likely clusters of related names as well as rankings indicating which names are likely to appear together in a certain area on a particular road - may turn out to be required. Given the fact that a lot of related information has already been stored on CD-ROMs in vehicle navigation systems, it appears reasonable to exploit this information in order to increase the reliability of road sign interpretation.
One might even think about timely advice to the driver to slow down in order to secure the reliable scanning of road signs prior to critical junctions. Even if a navigation system may be advertised to provide independence from road signs, continuously cross checking the data base of the navigation system against road signs might decrease the risk to miss recent changes in the road network.