Driver support systems of intelligent vehicles will predict potentially dangerous situations in heavy traffic, help with navigation and vehicle guidance and interact with a human driver. Important information necessary for traffic situation understanding is presented by road signs. A new kernel rule has been developed for road sign classification using the Laplace probability density. Smoothing parameters of the Laplace kernel are optimized by the pseudo-likelihood cross-validation method. To maximize the pseudo-likelihood function, an ExpectationMaximization algorithm is used. The algorithm has been tested on a dataset with more than 4 900 noisy images. A comparison to other classification methods is also given.Key words: Road sign recognition, Kernel density estimation, Expectation-maximization algorithm
Road Sign RecognitionIn an intelligent vehicle a Driver Support System (DSS) should work as a driver copilot, continuously monitoring the driver, vehicle and the environment in order to facilitate human decisions about immediate vehicle guidance and navigation (Nagel). To be able to help the driver with decision making, the DSS must understand the current traffic situation. Therefore, it should create and maintain a model of its neighborhood. Because of the dominant role of visual information for the corresponding author : pavel@ph.tn.tudelft.nl 1 The final work on the paper has been done in the Pattern Recognition Group, Delft Univ. of Technology, P.O. Box 5046, 2600 GA, Delft, The Netherlands human driver, computer vision methods are often used in intelligent vehicle prototypes for the creation of such model. Road signs offer, among the other traffic devices, a lot of important information about the current traffic situation. Two basic road sign groups exist -ideogram-based and text-based signs. While the first group uses simple ideographs to express the sign meaning, the second one contains road signs with texts, arrows and other symbols. This article is concerned with the recognition of ideogram-based road signs using statistical pattern recognition methods. A comprehensive study of road sign recognition presented by Lalonde and Li (1995) compiles information about related algorithms, research groups and results. Several research projects dealing with the road