Reliability-based assessment of road design features and crash risk using a socio-economic index for safety prioritization
DOI: 10.1038/s41598-026-36005-3
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Summary
This study addresses the need for a comprehensive framework to assess highway crash risk by integrating geometric design features with socio-economic factors. Traditional models often analyze crash frequency or costs separately and lack a formal probabilistic assessment of uncertainty. To bridge this gap, the authors developed a reliability-based assessment method applied to a 186-kilometer segment of Highway No. 36 in Iran. The primary motivation was to create a tool that simultaneously incorporates social crash costs, construction costs, and geometric variables to prioritize safety interventions more effectively than deterministic approaches. The methodology combined Empirical Bayes crash predictions from the Highway Safety Manual with severity-based social crash costs and construction cost estimates from the Florida Department of Transportation. A socio-economic risk index was calculated by comparing predicted social losses to construction costs. This index was incorporated into a reliability framework using limit-state functions and Monte Carlo simulations to compute the exceedance probability of crash risk. Data collected between 2019 and 2023 included geometric characteristics (e.g., lane width, shoulder type, embankment slope) from field surveys, as well as traffic and crash records from the Khorasan Razavi Road Maintenance and Transportation Organization. Statistical analysis confirmed that most risk variables followed a Gamma distribution, while the overall risk index followed a Lognormal distribution. The results identified specific geometric features that significantly influence crash risk. Horizontal curves exhibited the highest crash risk, whereas segments longer than 4 km showed the lowest risk values. Risk increased with wider lanes, gravel shoulders, greater shoulder widths, and embankment slopes steeper than 4%. Conversely, grades between 0 and 3% reduced risk, while steeper grades elevated it. Guardrails demonstrated mixed effects, reducing risk at lower index levels but not consistently at higher ones, likely due to their association with other adverse roadside conditions. The analysis suggested that wider lanes and shoulders may increase perceived safety, encouraging higher speeds and thus increasing crash severity rather than frequency. The significance of this study lies in its development of a unified probabilistic framework for safety prioritization. By multiplying the socio-economic risk index by the exceedance probability, the authors generated a reference risk curve to rank segments for safety improvements. This approach offers a methodological advantage over traditional deterministic models by explicitly accounting for uncertainty and integrating both societal burdens and economic trade-offs. The findings provide a rational basis for allocating limited resources to high-risk projects, ensuring that safety interventions are targeted where the potential social benefits outweigh the financial investment. This framework advances highway safety policy by offering a holistic, data-driven tool for managing transportation risks.
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| Stage | Outcome | Tool | Model | Prompt | Attempts | Completed |
|---|---|---|---|---|---|---|
| discover | success | Crossref | — | — | 1 | 2026-06-25 |
| archive | success | canonical_url | — | — | 1 | 2026-06-26 |
| extract | success | cached | — | — | 2 | 2026-06-26 |
| clean | success | clean | — | — | 1 | 2026-06-25 |
| chunk | success | chunk | — | — | 1 | 2026-06-25 |
| embed | success | embed | Qwen/Qwen3-Embedding-8B | — | 1 | 2026-06-25 |
| promote | success | — | — | — | 1 | 2026-06-25 |
| summarize | success | llm | qwen3.6-27b-prismaquant | summ-v5 | 1 | 2026-06-26 |
| tag | success | vector_similarity | — | — | 6 | 2026-06-25 |
| verify | success | — | — | — | 1 | 2026-06-26 |
Summary generated by qwen3.6-27b-prismaquant on 2026-06-26; verification: verified.
Topics
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- induced exposure
- incidence prevalence
- demographic disparities
- roadway lighting effects
- comparative international
Information type
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- Empirical Findings: crash risk outcomes