Abstract
Vehicle movements at signalized intersections should follow the guidance of lane marking arrows. Turns are permitted or banned depending on the existence of lane marking arrows establishing network link connectivity. Lane markings are the interface that joins consecutive upstream and downstream intersections. Traffic flows from origins to destinations across intersections should be governed by lane markings. In this study, conventionally fixed lane markings are relaxed as binary variables to be optimized by maximizing the green bandwidths. The proposed methodology is innovative in that it extends the lane-based design framework to incorporate green band maximization for enhancing traffic signal coordination. Path flows are controlled to satisfy flow conservations and to compile turning flows at intersections. With these turning flows as inputs, lane markings can be optimized together with the coordinated traffic signal settings. Path flows, path travel times, and path choices are evaluated through new linear constraints. For path travel times, cruise times along lanes and total delays at the ends of lanes are evaluated. The non-linear total delays are approximated by the proposed linearized delay function. The model coefficients are calibrated by network data as in a previous study. The problem is formulated as a binary-mixed-integer-linear-program and solved by standard branch-and-bound techniques using a CPLEX solver. To avoid non-linearity in the problem formulation, the bandwidth maximization approach is adopted instead of minimizing the total network delay in the design of the signalized network. A network with four intersections is provided to demonstrate how optimized lane markings can create efficient network link configurations. The numerical results are promising compared with those obtained in previous studies and show that the overall network performance can be improved.
Highlights
Links with shorter travel times are preferred by users over travel between origins and destinations (OD)
Apart from mathematical constraint sets developed in previous sections, which relate the adjacent upstream and downstream intersections, it must be noted that the actual bandwidth should always be shorter than or equal to the green duration times operating at individual intersections for the traffic moving along the selected major routes and OD pairs
Green bandwidth maximization enables the coordination of traffic signal settings in a network system
Summary
Links with shorter travel times are preferred by users over travel between origins and destinations (OD). Apart from mathematical constraint sets developed in previous sections, which relate the adjacent upstream and downstream intersections, it must be noted that the actual (green) bandwidth should always be shorter than or equal to the green duration times operating at individual intersections for the traffic moving along the selected major routes and OD pairs. A similar concept and linearization technique is applied to evaluate the delay time at the end of a lane that is related to its lane flow (including turning and straight-ahead movements), proportion of a signal cycle which is effectively green, and degree of saturation. In Eq (27), an auxiliary binary variable Pn;i;k for lane k from arm i at intersection n is forced to be zero when the flow factor yn,i,k is smaller than or equal to the proportion of a signal cycle which is effectively green, Fn;i;k for unsaturation conditions. Mðao;d;h0o;d À 1Þ wo;d;ho;d À wo;d;h0o;d Mð1 À ao;d;ho;d Þ; 8o 2 f1; 2; . . . ; Og; d 2 f1; 2; . . . ; Dg; ho;d 2 f1; 2; . . . ; H o;dg; h0o;d 61⁄4 ho;d
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