Lane-Based Optimization Method for Minimizing Delay of Isolated Signal-Controlled Junctions

Discrete Dynamics in Nature and Society

Liu

2017

Self Cite

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.

Section: Discrete Dynamics In Nature and Societymentioning

confidence: 99%

Lane-Based Optimization for Macroscopic Network Configuration Designs

Discrete Dynamics in Nature and Society

Liu

2017

Self Cite

“…More recently, a lane-based optimization method for isolated signal-controlled junctions was formulated to include lane-marking layouts as design variables for analysis (Wong et al, 2000;Wong and Wong, 2003a), in which the signal settings for traffic movements and pedestrian crossings were optimized in a unified framework. The lane markings, which were considered as discrete permitted movements in individual traffic lanes, were defined as binary variables to which only 0 or 1 could be assigned to represent their existence during the optimization process.…”

Section: Introductionmentioning

confidence: 99%

A Lane-Based Optimization Method for the Multi-Period Analysis of Isolated Signal-Controlled Junctions

Wong¹,

Tong

2006

Transportmetrica

Self Cite

Recently, a lane-based optimization method was developed for the design of isolated signal-controlled junctions. The lane markings are relaxed as binary-type control variables and are integrated into the design framework, in which the lane markings and signal settings can be optimized simultaneously to maximize the overall junction performance. To take into account the time-varying effects of traffic demand, the lane-based optimization method has been enhanced to cater for multi-period demand patterns. To eliminate ambiguity, only a single set of lane markings (also referred to as the permitted movements) can be established on the ground for operation throughout all of the design periods, which implies that during various design periods road users that approach a junction will be guided by the same set of lane markings. In accordance with the specific traffic conditions in different design periods, road users can make their own choice of traffic lane for turning, provided that they do not violate the permitted movement patterns. In the present formulation, the actual lane utilization patterns are referred to as the effective movements. A set of linear constraints is developed to relate all of the lane-based control variables and to prescribe the feasible solution region. The optimization for the usual objective function is formulated as a mathematical program. Standard and heuristic solution methods are derived, and numerical examples are also given for demonstration.

“…Excess green durations along the approaching traffic lanes from Legs 2 and 4 could be extracted and reassigned to overflowing approaching traffic lanes from Legs 1 and 3. To facilitate this refinement process, Δ = 1 s has been adopted to satisfy the constraints of (12) and (13). To refine the signal settings from the maximizing capacity in the morning peak period, the excess green duration from Leg 2 is extracted first (8 s), and then the excess green duration from Leg 4 (9 s) is extracted.…”

Section: Refining Traffic Signal Settings Under Fixed Cycle Lengthmentioning

confidence: 99%

“…Short lanes will overflow. Existing lane-based traffic signal optimization tends to design longer green times and longer cycle lengths to maximize the overall intersection capacity [13][14][15][16]. To overcome this weakness, we propose a new set of refinements to modify the traffic signal settings at isolated intersections to prevent overflow.…”

Section: Introductionmentioning

confidence: 99%

“…In the past few decades, traffic signal settings at signalcontrolled intersections have been optimized using different optimization frameworks, including the stage-based method [1][2][3][4], the group-based method [5][6][7][8][9][10][11][12], and the lane-based method [13][14][15][16]. Traffic signal settings are optimized by maximizing the overall intersection capacity or by minimizing the total intersection delay.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Refining Lane-Based Traffic Signal Settings to Satisfy Spatial Lane Length Requirements

Liu

Journal of Advanced Transportation

2017

Self Cite

In conventional lane-based signal optimization models, lane markings guiding road users in making turns are optimized with traffic signal settings in a unified framework to maximize the overall intersection capacity or minimize the total delay. The spatial queue requirements of road lanes should be considered to avoid overdesigns of green durations. Point queue system adopted in the conventional lane-based framework causes overflow in practice. Based on the optimization results from the original lanebased designs, a refinement is proposed to enhance the lane-based settings to ensure that spatial holding limits of the approaching traffic lanes are not exceeded. A solution heuristic is developed to modify the green start times, green durations, and cycle length by considering the vehicle queuing patterns and physical holding capacities along the approaching traffic lanes. To show the effectiveness of this traffic signal refinement, a case study of one of the busiest and most complicated intersections in Hong Kong is given for demonstration. A site survey was conducted to collect existing traffic demand patterns and existing traffic signal settings in peak periods. Results show that the proposed refinement method is effective to ensure that all vehicle queue lengths satisfy spatial lane capacity limits, including short lanes, for daily operation.