Operational study of roundabouts and signal-controlled intersections in Kaunas City
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Summary
This study addresses the comparative operational efficiency of roundabouts and signal-controlled intersections in urban environments, specifically focusing on traffic safety. Motivated by the high prevalence of accidents in built-up areas and the need to minimize infrastructure costs while ensuring safety, the authors sought to determine which intersection type performs better under varying traffic conditions. The research was conducted in Kaunas City, Lithuania, a region with significant accident rates, to provide evidence-based recommendations for urban planning. The methodology involved analyzing 15 four-leg, at-grade intersections within an 8 km² study area in northern Kaunas, comprising five roundabouts and ten signal-controlled intersections. Traffic volume measurements were taken during the evening peak hours (16–18 h) in November 2011 to determine capacity, as traffic jams indicated saturated flow. These peak-hour volumes were used to calculate the Annual Average Daily Traffic (AADT) for each intersection using relative loading coefficients derived from national road data. Accident data for fatal and injury incidents occurring between 2007 and 2010 were obtained from the Traffic Police Board. Accidents were attributed to intersections if they occurred within the junction or within 100 meters of its approaches. The safety performance was quantified using an event-based accident rate (AR), defined as the number of accidents per million passing vehicles. The results revealed distinct trends in safety performance relative to traffic volume. For signal-controlled intersections, there was a weak inversely proportional relationship between traffic capacity and accident risk; as traffic volume increased, the accident rate decreased. Conversely, roundabouts exhibited a direct relationship where the accident rate increased with higher traffic volumes. The authors identified a "breaking point" at approximately 3,890 vehicles per hour. Below this threshold, roundabouts were safer, but above it, signal-controlled intersections demonstrated superior safety performance. The study attributes the increased accident risk in high-volume roundabouts to a growing number of conflict points due to complex designs and driver indiscipline caused by time losses. In contrast, signal-controlled intersections maintained lower accident rates at high volumes due to enforced driver discipline and grouped vehicle movement, which simplifies navigation. The significance of this study lies in its provision of a specific quantitative threshold for selecting intersection types based on traffic volume and safety outcomes. It suggests that for intersections accommodating high traffic flows exceeding 3,890 veh/h, signal control is more favorable than roundabouts. The authors conclude that while safety is a critical metric, a comprehensive evaluation including time expenditure, fuel consumption, and operating costs is necessary for sustainable urban development. They also note that the studied intersections were designed according to Soviet-era standards, implying that future research should examine intersections built to modern safety standards to validate these findings.
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| Stage | Outcome | Tool | Model | Prompt | Attempts | Completed |
|---|---|---|---|---|---|---|
| discover | success | Crossref | — | — | 1 | 2026-06-25 |
| archive | success | semantic_scholar | — | — | 6 | 2026-06-26 |
| extract | success | cached | — | — | 2 | 2026-06-26 |
| clean | success | clean | — | — | 1 | 2026-06-26 |
| chunk | success | chunk | — | — | 1 | 2026-06-26 |
| embed | success | embed | Qwen/Qwen3-Embedding-8B | — | 1 | 2026-06-26 |
| enrich | success | openalex | — | — | 1 | 2026-06-26 |
| promote | success | — | — | — | 1 | 2026-06-25 |
| summarize | success | llm | qwen3.6-27b-prismaquant | summ-v5 | 1 | 2026-06-26 |
| tag | success | vector_similarity | — | — | 6 | 2026-06-26 |
| verify | success | — | — | — | 1 | 2026-06-26 |
Summary generated by qwen3.6-27b-prismaquant on 2026-06-26; verification: verified.
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- Empirical Findings: crash risk outcomes