Traffic Congestion Reporting Using Subsection Free-Flow Speeds
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Solution Overview
Problem
The 'toll plaza effect' in vehicular traffic systems leads to inaccurate traffic condition estimates due to varying speed reports from probe vehicles, causing rapid fluctuations in congestion messages, known as 'thrashing', as vehicles approach or leave toll plazas, leading to incorrect color coding of road segments on maps.
Innovation Solution
Assigning specific free-flow speeds to subsections of road segments containing bottlenecks, such as toll plazas, to calculate traffic congestion based on the observed speed ratio, known as the jam factor, and communicating this information to clients for accurate traffic condition reporting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If probe vehicles transmit speed observations to a vehicular traffic system, then traffic condition data is collected, but the system may mistakenly interpret low speeds as congestion rather than toll payment behavior
Solution Approach 1:
The patent divides a road segment into multiple subsections, with each subsection having its own specific free-flow speed characteristic. This allows the system to differentiate between genuine congestion (where observed speed is significantly below the local free-flow speed) and normal variations in speed patterns, thereby improving measurement precision while reducing misinterpretation of speed data.
Solution Approach 2:
The road segment is segmented into multiple subsections, each with distinct free-flow speed parameters. This segmentation enables the system to compare observed speeds against location-specific expectations, allowing accurate distinction between congestion and toll payment behavior based on whether the observed speed deviates from the subsection's characteristic free-flow speed.
2Productivity
If the vehicular traffic system determines congestion based on probe reports, then traffic information is provided to users, but rapid fluctuations in congestion messages occur due to varying probe locations and timing
Solution Approach 1:
By assigning specific free-flow speeds to different subsections of the road segment, the system creates stable, location-specific reference values. Congestion determination becomes stable because it compares observed speeds against these fixed subsection characteristics rather than varying overall segment averages, reducing thrashing while maintaining responsive reporting.
3Ease of operation
If a single free-flow speed is assigned to an entire road segment, then the system is simple to operate, but it cannot accurately distinguish congestion from toll payment effects
Solution Approach 1:
The system segments the road into multiple subsections, each with its own free-flow speed parameter. This segmentation improves measurement precision by allowing accurate distinction between congestion and toll effects, while maintaining ease of operation through automated assignment of subsections and their characteristics based on probe vehicle data and map information.
Solution Approach 2:
The system automatically determines subsection boundaries and assigns free-flow speed characteristics to each subsection based on probe vehicle observations and map data. This self-service approach eliminates manual configuration complexity while enabling accurate congestion detection through localized speed comparisons.
Data Source
AI summary
Methods for reporting traffic conditions on road segments containing a bottleneck include: (a) calculating an amount of traffic congestion on a segment of a roadway, the segment containing a bottleneck, based on a free-flow speed specific to a subsection of the segment from which a report of an observed speed is received; and (b) communicating, by the computer processor, information indicative of the amount of traffic congestion on the segment to a client. Apparatuses for reporting traffic conditions on road segments containing a bottleneck are described.