B. Spot Light Detection (S LD)Despi

B. Spot Light Detection (S LD)Despite the fact that traffic lights can be very different, all share the common property to emit light. Therefore a robust SLD appears to be the best base for TLR. The aim of this SLD step is to miss the fewes t sought lights as possible. This task is not an easy task due to the complexity of an urban scene and especially when tr ying to detect small spots light in order to detect far traffic lights.To detect spots light in the source image we use an algorithm we already descri bed in [8]. This algorithm uses the top-hat morphological operator [9]-[10] to detect the bright areas and then appl ies shape filtering and region growing algorithm to keep only the consistent areas. Only grayscale information is used in the SLD step. Therefore, it is few sensitive to illumination variation and color distortion.The SLD we use detect up to 90% of all the visible lights emitted from the traffic lights and is able to find any spot light as soon as it is 4 pixels wide or more. Fig. 4 illustrates the result of the SLD algorithm.