PUBLIC TRANSPORT PRIORITY WITHIN SCATS - A SIMULATION CASE STUDY IN DUBLIN

As part of the detailed study on the implementation of Dublin's proposed Light Rail Transit (LRT), an important concern is the interaction of the LRT with general traffic in the city center areas. More specificially, the concern was how LRT priority could be achieved within the existing Urban Traffic Control System (UTCS). In 1989, the city of Dublin introduced the area control Sydney Co-ordinated Adaptive Traffic System (SCATS), which is mainly implemented in Australian and Southeast Asian cities. At present in Dublin, SCATS has 170 traffic signals under its control and is continuously expanding. The city council identified four critical traffic loops (set of consecutive signal controlled junctions) within the city center area that are sensitive to disruptions, particularly at peak hours. If any one or more of these loops is constricted along any part of its length for even a short length of time, quite rapidly the entire loop will grind to a halt; soon after the other loops will be held up which will lead to gridlock in the city center. The principal objective of the study presented in this paper was to establish whether LRT priority at signalized intersections is possible and practical within the framework of Dublin's existing SCATS UTCS.