Automatic detection and interpretation of road signs

Automatic sign interpretation on highways and roads is a real-time imaging application with utility in autonomous vehicle operation, intelligent highway systems and sign inventory systems for transportation departments. We propose a step-wise multistage sign recognition and interpretation strategy. The approach relies on independent examination of spectral and spatial features. The spectral processing step utilizes color cues to extract candidate target pixels in the image. In the next stage, spatial features extracted from the image are matched against attributes derived from object models. Relational feature analysis can further refine the results after the spatial analysis step. Color images of a variety of signs including speed limit, yield, stop and route number signs formed the training set. The accuracy of the method is measured for different types of signs and the results are discussed.