Distributed Traffic Signal Control for Network Throughput
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Solution Overview
Problem
Existing traffic signal control systems face scalability issues and inefficiencies in managing traffic flow, particularly in large road networks, as they rely on pre-defined split plans and heuristic approaches that do not account for real-time differential traffic backlogs and flow rates.
Innovation Solution
A distributed traffic signal control method that activates phases based on current differential traffic backlogs and flow rates between upstream and downstream links, using a control unit to determine the optimal phase that maximizes network throughput by multiplying backlog and flow rate parameters for each unique link combination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If optimization-based approaches are used for traffic signal control, then traffic flow efficiency is improved, but scalability to large road networks deteriorates
Solution Approach 1:
The patent divides the traffic network into individual junctions, each with its own controller that operates independently using local queue information. This segmentation allows each controller to make optimized decisions for its local area without requiring global network optimization, thereby maintaining efficiency while improving scalability to large networks.
Solution Approach 2:
Each junction controller uses local queue length information from upstream and downstream links to determine phase activation. This local quality approach allows decisions to be made based on immediate local conditions rather than requiring global network state, enabling the system to scale to large networks while maintaining responsive traffic flow management.
2Productivity
If backpressure routing is applied to traffic signal control, then network throughput is maximized, but implementation feasibility deteriorates due to unrealistic assumptions
Solution Approach 1:
The traffic signal system serves itself by using local queue information available at each junction to make phase activation decisions. Each controller independently determines when to activate phases based on the differential backlog between upstream and downstream links, eliminating the need for external global control or unrealistic assumptions about vehicle destinations and routing.
3Device complexity
If pre-defined split plans are used in traffic signal control, then control simplicity is maintained, but adaptability to real-time traffic conditions deteriorates
Solution Approach 1:
The system dynamically adjusts phase activation timing based on real-time queue length measurements from upstream and downstream links. Instead of using fixed pre-defined split plans, the controller continuously adapts its decisions to current traffic conditions, activating phases when the differential backlog indicates it will maximize throughput.
Solution Approach 2:
The controller uses feedback from queue length sensors on upstream and downstream links to determine when to activate phases. This feedback mechanism allows the system to adapt to real-time traffic conditions while maintaining simple control logic based on the differential backlog comparison.
Data Source
AI summary
A distributed traffic signal control method is provided for a directed network comprising a plurality of junctions, each junction having a plurality of links connected thereto, the links comprising one or more upstream links and one or more downstream links, the method comprising: activating one of a plurality of phases of the junction for a predetermined time period which maximizes the directed network throughput based on current differential traffic backlogs between said one or more upstream links and said one or more downstream links, each phase providing a unique combination of traffic signals at the junction for guiding traffic from the upstream link(s) to the downstream link(s). There is also provided a corresponding traffic signal controller, a traffic control system comprising the traffic signal controller, and a computer readable medium having stored therein computer executable codes for instructing a computer processor to execute the distributed traffic signal control method.