Lane-Based Optimization for Macroscopic Network Configuration Designs

Abstract

Lane markings (arrows) at individual intersections serve as interfaces to connect upstream and downstream intersections in signal-controlled networks. Demand flows from origins to destinations may need to pass through a series of intersections. If lane markings are not well established to ban turns at intersections, then paths connecting origin and destination (OD) pairs could be inefficient. Due to indirect connections, road users need to take longer paths to reach their destinations. Conventionally, network configurations are fixed inputs for network analysis. In the present study, concepts of the lane-based designs for individual signalized intersections are extended for signal-controlled network designs. Taking OD demand flows as inputs, the proposed algorithm will optimize all lane markings and assigned lane flows on approach lanes. Paths (flows) will then be optimized by linking up the optimized lane markings across upstream and downstream intersections. Traffic signal settings at individual intersections will be optimized simultaneously by maximizing the reserve capacity for the entire OD demand flow matrix. The problem is formulated as a Binary-Mixed-Integer-Linear-Program (BMILP) and a standard branch-and-bound routine is applied to solve for global optimum solutions. A numerical example using a 4-intersection network will be given to demonstrate the effectiveness of the proposed design methodology.

Designs for Safer Signal-Controlled Intersections by Statistical Analysis of Accident Data at Accident Blacksites

“…Current signalized intersection designs usually optimize engineering performance by minimizing total vehicular delays or maximizing the reserve capacity (throughput) [37]- [40]. Basic safety measures in conventional design methods include implementation of (i) minimum green light durations, (ii) minimum red light durations, and (iii) minimum clearance times to prevent front bumper-rear bumper collisions and vehicle clashes resulting from incompatible vehicular and pedestrian movements inside common areas at intersections [41].…”

“…The traditional designs of signalized intersections have focused on optimizing signal timings, such as the cycle time and the start and duration of green-times of different phases, to maximize the overall intersection capacity or minimize the total delay experienced by users. These conventional stage-, group-(or phase-), and lane-based design optimization methods satisfy 'basic' safety requirements [37]- [40]. To enhance safety and prevent accidents at signalized intersections, it is expected that intersection geometries and lane usage patterns need to be refined.…”

Optimization of signalized network configurations using the Lane-based method

“…A modeling interface was established between the connectivity of network links and lane marking designs at intersections [35]. Maximizing the common flow multiplier to scale the whole OD (input) demand flow matrix, as done in a previous study [36], can maximize the capacities of all individual signalized intersections within a network and can generate lane markings for configuring the network connections [37]. However, equilibrium flow conditions and proper signal coordination were not considered.…”

“…To optimize the lane marking patterns at individual intersections, 13 sets of linear constraints are required, taking the turning flow patterns as model inputs for defining a feasible solution region for the traffic signal settings [25, 27, 37]. The constraints are set to (i) ensure that the number of lane marking arrows for turns from upstream do not exceed their respective numbers of downstream exit lanes; (ii) satisfy the requirements for flow conservation, equalizing the given turning flows and the sum of assigned lane flows; (iii) establish lane markings to provide consistency in the assigned turning flows; (iv) avoid (internal) conflicts of lane markings across adjacent approach lanes from the same approaches; (v) establish single lane markings (for a single turn) or shared lane markings (for multiple turns) on approach lanes, thus ensuring the use of all approach lanes; (vi) restrict the optimized cycle time to be within the users’ specified allowable range; (vii) ensure that the optimized green duration times exceed the users’ specified minimum duration of green times; (viii) restrain the starts of green times within the traffic signal cycle; (ix) provide minimum clearance times (or intergreen times) to separate the right-of-way of conflicting traffic movements; (x) introduce successor functions to regulate the signal display orders for conflicting pairs of traffic movements; (xi) synchronize the traffic signal settings for turns and lanes according to the optimized lane marking patterns; (xii) equalize the flow factors on adjacent approach lanes with identical lane marking designs on both approach lanes; and (xiii) restrict the maximum degree of saturation to below the users’ specified figure for all approach lanes.…”

“…The given OD flows might be forced to use the available but congested paths provided by inefficient link connections leading to sub-optimal flow distributions. In a recent study [37], lane markings were optimized by maximizing the common flow multiplier to the given OD matrix, thus generating network configurations. However, equilibrium flow conditions and the coordination of traffic signal settings were not modeled, leading to unrealistic results.…”