  Road signs detection and recognition in natural scenes is one of the most
important tasksin the design of Intelligent Transport Systems (ITS). However,
illumination changes remain a major problem. In this paper, an efficient
ap-proach of road signs segmentation based on photometric invariants is
proposed. This method is based on color in-formation using a hybrid distance,
by exploiting the chro-matic distance and the red and blue ratio, on l Theta
Phi color space which is invariant to highlight, shading and shadow changes. A
comparative study is performed to demonstrate the robustness of this approach
over the most frequently used methods for road sign segmentation. The
experimental results and the detailed analysis show the high performance of the
algorithm described in this paper.
