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In urban areas, conventional transit priority systems (e.g., passive priority) present some problems, such as causing too many traffic delays and degradation of on line performance due to the lack of real-time data. The purpose of this study is to develop an on line adaptive priority strategy to optimize traffic operation at a series of consecutive grade crossings in urban areas. The proposed strategy takes into account the impact on cross-street traffic as well. A mathematical model of non linear programming with linear constraints is formulated to minimize overall passenger delays at grade crossings for light rail transit and to minimize the impact on cross-street traffic. The optimization is enabled by real-time arrival-time prediction with GPS-equipped vehicles. To exhibit the anticipatory performance of the proposed strategy, both a numerical analysis and a simulation test are conducted with trolley operation along a stretch of C Street in San Diego. Compared with current signal timings, those obtained from the proposed strategy demonstrate promising results. DOI: 10.1061/(ASCE)TE.1943-5436.0000344. (C) 2012 American Society of Civil Engineers.