Research On Transition Methods In Traffic Signal Control For Urban Roads

Multiple signal timing schemes are usually set in the Urban traffic signal control system because congestion period occurs in different time of day. Between two successive timing schemes, transition is need to reduce the undesired impacts derived from the switching process. The scenarios of an independent intersections and a coordinated intersection group are in different in designing the transition. Off-set is need to be considered for a coordinated intersection group.In this research, merits of multiple traditional transition methods were fused to alleviate the problem that green time jumps twice during the transition period when cycle length of the two successive timing schemes were significantly different. In detail, the transition foundation and green time allocation which was separately used by traditional methods were overall considered to design a new transition method with fixed step width (TM-FSW) for the two scenarios, i.e. with- and without-offset, respectively. Furthermore, a novel transition method with dynamic step width (TM-DSW) was proposed based on the fuzzy control theory, as the transition methods with fixed step width may not cover all transition needs that triggered by time-varying traffic demand at intersections.Paramics simulation software was used to test the control performance of the proposed methods.In the scenario of without-offset, both the proposed transition method, whatever with fixed or dynamic step width, perform better during the phase from off-peak hours to peak hours than the phase from peak hours to off-peak hours. On the same time, TM-DSW outperforms TM-FSW. In the scenario of with-offset, the proposed methods yield better control performance than the traditional methods under the condition that each signal phase was assigned similar green time for any of the intersection in the coordinated group. Moreover, TM-DSW produces better queue and delay control when comparing with TM-DTW.