Investigation of the discharge flow rate patterns at real-time traffic signal control intersections
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Summary
This study investigates the impact of variable queue lengths and green times on discharge flow rates at real-time managed signalized intersections, addressing a gap in literature that predominantly focuses on fixed-time systems. The research aims to understand how these factors influence traffic performance, specifically examining time headways and saturation flows to improve intersection management in urban areas prone to congestion. The methodology involved collecting traffic flow data from two fully actuated intersections in Mersin, Turkey: a four-leg intersection (CNR) and a roundabout (Kipa). Video records and signal timing data were obtained from the Mersin Metropolitan Municipality for morning peak hours over two days. The study analyzed 337 cycles with queue lengths exceeding eight vehicles, focusing on middle lanes to minimize turning vehicle effects. Time headways were calculated using MATLAB coding from video footage, and Analysis of Variance (ANOVA) tests were employed to statistically evaluate the effects of queue position and green time intervals on discharge rates. The results demonstrated that the time headways of the first four vehicles in a queue were statistically larger than those of subsequent vehicles (p-value < 0.05), indicating significant initial losses. Consequently, the discharge flow rate increased by approximately 30% after the first four vehicles, reaching saturation flow from the fifth vehicle onward. For the Kipa intersection, maximum flow occurred between the 13th and 16th vehicles, while for CNR, it occurred between the 9th and 13th. Regarding green time, significant differences in discharge rates were observed only during the initial phase: the first 12 seconds for Kipa and the first 6 seconds for CNR. After these initial periods, time headways remained statistically constant, suggesting that initial lost times negatively impact traffic flow, but discharge rates stabilize quickly thereafter. The findings confirm that saturation flow is achieved shortly after the start of the green phase, with the first few vehicles experiencing substantial delays. This consistency between queue length and green time analyses highlights the importance of accounting for initial lost times in traffic modeling. The study provides empirical evidence for real-time signal control systems, suggesting that performance evaluations should consider the rapid stabilization of discharge rates after the initial seconds of green time. These insights can aid traffic engineers in optimizing signal timing and improving intersection efficiency in urban environments.
Provenance
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| Stage | Outcome | Tool | Model | Prompt | Attempts | Completed |
|---|---|---|---|---|---|---|
| discover | success | OpenAlex-citations | — | — | 1 | 2026-06-20 |
| archive | success | unpaywall | — | — | 2 | 2026-06-26 |
| extract | success | cached | — | — | 2 | 2026-06-26 |
| clean | success | clean | — | — | 1 | 2026-06-20 |
| chunk | success | chunk | — | — | 1 | 2026-06-20 |
| embed | success | embed | Qwen/Qwen3-Embedding-8B | — | 1 | 2026-06-20 |
| promote | success | — | — | — | 1 | 2026-06-20 |
| summarize | success | llm | qwen3.6-27b-prismaquant | summ-v5 | 1 | 2026-06-26 |
| tag | success | vector_similarity | — | — | 6 | 2026-06-20 |
| verify | success | — | — | — | 1 | 2026-06-26 |
Summary generated by qwen3.6-27b-prismaquant on 2026-06-26; verification: verified.
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