Abstract
Left-turn bays may be provided at paired intersections when heavy left-turn demands exist on some approaches. Such left-turn bays may have significant effects on intersection operations. Considering the settings of left-turn bays, two single-objective optimization models are developed for paired intersections with uncoordinated and coordinated signals, respectively. Numerical examples are fulfilled to demonstrate and compare the formulated models, and the orthogonal simulation experiments are carried out. Assuming that the relevance of traffic flow exists, the results show that the optimized effective green times and left-turn bay lengths depend on traffic demand, whereas the optimized offset between paired intersections is sensitive to intersection spacing; the optimization model with coordinated signals outstrips that with uncoordinated signals at 99% confidence level when the distance between paired intersections is not too far and traffic demand is not too low, whereas the former may be inferior to the latter when traffic demand is low enough and intersection spacing is far enough.
Highlights
IntroductionTo accommodate the relatively heavy left turns at intersections, left-turn bays (i.e., short left-turn lanes) are usually provided on intersection approaches so that the capacity and level of service of the entire intersection can be improved. e length of such a left-turn bay is generally limited, but such turn bays (i.e., short lanes) are viewed as normal exclusive turn lanes in the Highway Capacity Manual [1]
To accommodate the relatively heavy left turns at intersections, left-turn bays are usually provided on intersection approaches so that the capacity and level of service of the entire intersection can be improved. e length of such a left-turn bay is generally limited, but such turn bays are viewed as normal exclusive turn lanes in the Highway Capacity Manual [1]
At 1% significance level, the findings indicate that the following: (1) the intersection spacing has no significant effects on all the decision variables and performance indices, whereas the traffic demand only has no significant effects on the offset between paired intersections; (2) the optimization model does not have significant impacts on all the effective green times, left-turn bay lengths, and performance indices but has significant impacts on the offset between paired intersections; and (3) the combination of the optimization model and intersection spacing has no significant effects on the optimization outcomes, whereas the combination of the optimization model and traffic demand and that of the traffic demand and intersection spacing both have significant impacts on the optimization outcomes
Summary
To accommodate the relatively heavy left turns at intersections, left-turn bays (i.e., short left-turn lanes) are usually provided on intersection approaches so that the capacity and level of service of the entire intersection can be improved. e length of such a left-turn bay is generally limited, but such turn bays (i.e., short lanes) are viewed as normal exclusive turn lanes in the Highway Capacity Manual [1]. E length of such a left-turn bay is generally limited, but such turn bays (i.e., short lanes) are viewed as normal exclusive turn lanes in the Highway Capacity Manual [1]. Such a treatment ignores the impacts of turn bays on traffic flow operations because of being underused. Wu [7] presented a theoretical-empirical model to estimate the total approach capacity at signalized intersections with short left-turn lanes and shared through-right lanes. The theoretical delay models were given for protected left-turn operations at signalized intersections with left-turn bays during heavy traffic [10]. Li and Elefteriadou [11] proposed a method to maximize the throughput of an approach with left-turn or Mathematical Problems in Engineering right-turn bays and suggested to repeat the phase twice in the cycle for such an approach
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