Optimal Allocation of Lane Space and Green Splits of Isolated Signalized Intersections with Short Left-Turn Lanes

At an isolated signalized intersection, the capacity of the lane group with a short left-turn lane heavily depends on the short lane length and the effective green time allocated for the lane group, as does the capacity of the entire intersection. In this paper, three optimization models are formulated and solved to optimally allocate the lane space and green splits of an isolated signalized intersection with short left-turn lanes. Two intersection performance indexes are proposed to compare the performance of the three models and study its sensitivity to model parameters. The results indicate that all three models can produce satisfactory capacity and delay performances, but it is laborious to find a suitable parameter set when using the objective functions of maximizing intersection capacity and minimizing the weighted sum of the normalized intersection capacity and delay; it is easy when using the objective functions of minimizing intersection delay, maximizing capacity-to-delay ratio, and minimizing delay-to-capacity ratio. Moreover, many sets of noninferior solutions can be obtained by minimizing the delay-to-capacity ratio and adjusting some parameters. Finally, three variations of the formulated models are recommended for use, and the procedure for using these models is given for practical applications.