The traffic light detection system is one of the key components of the vision traffic law enforcement system, such as red light runner detecting, turning against traffic light, and stopping at the non-stopping zone. With various conditions of both open outdoor environments and device setups, the traffic light detection must be robust to weather and illumination conditions, and also tolerant to various perspective angles.An automatic traffic light detection system at intersections is presented in this paper. It performs traffic light detection on traffic videos without any signals from the traffic light controllers. This system is useful to be integrated with another ITS (Intelligent Transportation System) components. Background images are first generated by the system and in the mean time illumination parameters are estimated. The HSI color model is employed, and fuzzy methods together with morphological technique are utilized to acquire the candidate traffic light areas. With the relative spatial and temporal information, the scales, positions, and timing sequences of traffic lights are obtained. Some results from a preliminary trial are reported, and the associated researches are in progress