Two apparent weaknesses in current signal setting methodology are addressed, namely the identification of the optimum number of phases and the optimisation of left-turn phasing (e.g., protected, permissive, or both). The proposed method integrates these two elements into the signal timing process for isolated intersections, which also entails the optimisation of cycle length and splits. The method directly considers the effect of minimum green times, practical cycle lengths, and permissive left-turn capacity models in an attempt to reach an optimal decision. Although primarily applicable to pretimed signal control the logic may also be adapted to single-ring actuated controllers. The scope of the method is limited to intersection geometries with exclusive left-turn lanes on all approaches and no overlap phasing.
Abstract