Alternating Zone Traffic Light Control for Bidirectional Green Waves
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Solution Overview
Problem
Existing traffic control methods are unable to effectively generate bidirectional green waves of traffic, as they are typically limited to one direction and fail to synchronize lights for simultaneous green waves in both directions.
Innovation Solution
The method involves dividing a roadway into an even number of zones, alternating the lighting states between these zones, and synchronizing the traffic light durations with the speed limit to allow continuous green waves in both directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If traffic lights are synchronized to create green waves in one direction, then travel time is reduced for that direction, but cross-traffic must be interrupted and the opposite direction cannot have a green wave
Solution Approach 1:
The roadway is divided into multiple zones along its length, with each zone containing traffic lights that can be independently controlled. This segmentation allows different sections of the road to have different light states (green or red) at the same time, enabling green waves to form in both directions simultaneously by coordinating which zones are green for each direction.
Solution Approach 2:
The invention transitions from traditional one-dimensional sequential control (all lights green then all red) to two-dimensional spatial-temporal control by dividing the roadway into zones and assigning different states to different zones. This dimensional expansion allows simultaneous green waves in opposite directions by having alternating zones green for each direction.
2Productivity
If traffic lights are controlled to allow cross-traffic, then intersection capacity is maintained, but continuous green wave flow in both directions cannot be achieved
Solution Approach 1:
The system implements periodic alternation between two operational modes: a first state where odd zones allow through-traffic and even zones allow cross-traffic, and a second state where the roles are reversed. This periodic switching enables both continuous green wave flow for through-traffic and adequate capacity for cross-traffic to proceed during their designated time windows.
Solution Approach 2:
The controller pre-coordinates the timing and duration of green phases for both through-traffic and cross-traffic in each zone before executing them. By calculating and setting the light duration based on zone length and speed limit, the system ensures that green waves are established in advance, allowing vehicles to proceed without stopping while cross-traffic gets guaranteed time windows.
3Ease of operation
If traditional traffic light timing is used, then all directions can proceed periodically, but stop-and-go situations occur and lane throughput is significantly reduced
Solution Approach 1:
The system dynamically adjusts traffic light states based on the direction of travel and position along the roadway, transitioning from static uniform timing to dynamic zoned control. Traffic lights are timed so that as vehicle platoons pass by lights in their direction, the lights are green, creating smooth continuous flow without stop-and-go situations while maximizing lane throughput.
Data Source
AI summary
A method of managing traffic lights that generates waves of unimpeded traffic in both directions of a roadway. The roadway is divided into an even number of zones of equal length, which are divided into two groups of alternating zones. A traffic speed and a traffic light duration are selected so that the zone length equals the traffic speed times the light duration. Initially all lights in all zones of one group are set to green, and all lights in all zones of the other group are set to red; then lights are switched in the next cycle to red for the first group and green for the other group. This pattern repeats. The arrangement of alternating zones and the relationship between zone length, speed, and light duration allows vehicles moving in either direction at the specified speed to encounter only green lights, enabling dramatic reductions in travel time.