Development of Crash Modification Factors for Continuous Flow Intersections
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Summary
This paper addresses the lack of documented safety benefits for Continuous Flow Intersections (CFIs), an innovative intersection design that displaces left-turn movements upstream to allow concurrent left and through traffic. While CFIs are known to increase capacity and reduce conflict points, their actual safety performance remains under-documented due to limited implementation data. The study aims to develop Crash Modification Factors (CMFs) for CFI conversions in Utah, specifically for partial CFIs where left turns are displaced on two approaches. The authors employed the Empirical Bayes (EB) methodology, which combines site-specific crash data with Safety Performance Functions (SPFs) to account for regression-to-the-mean bias. The analysis utilized six years of crash data (2008–2013) from the Utah Department of Transportation. The treatment group consisted of eight intersections converted to CFIs (seven partial, one full), while the comparison group included five comparable four-legged signalized intersections. The study defined the intersection influence area as a 76-meter radius and excluded the year of implementation from the "after" period analysis. Local calibration factors were derived from the comparison sites to adjust the SPFs for Utah conditions. The results indicate that partial CFIs experience a reduction in total crashes. The calculated CMF for CFI conversion is 0.877, corresponding to a Crash Reduction Factor of approximately 12.3% (± 4.6%). This suggests that converting a conventional intersection to a partial CFI reduces the expected number of total crashes by about 12%. The analysis relied on observed versus predicted crash frequencies, with the EB method providing a statistically robust estimate of the treatment's effectiveness. The significance of this work lies in providing the first published CMFs for CFI conversions, offering quantitative evidence of safety benefits for this unconventional design. The findings support the use of partial CFIs as a safety countermeasure, particularly in high-volume arterials. However, the authors note limitations, including the small sample size, the short duration of post-implementation data, and the exclusion of crash severity and type analysis. Future research is recommended to expand the dataset, refine local calibration factors, and analyze specific crash modes to further validate and optimize CFI designs.
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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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- Empirical Findings: crash risk outcomes