Safety Evaluation of Edge-Line Rumble Stripes on Rural Two-Lane Horizontal Curves
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Summary
This study evaluates the safety effectiveness and economic viability of edge-line rumble stripes (ELRSs) on rural two-lane horizontal curves. ELRSs are a variation of shoulder rumble strips where the pavement marking is installed directly over the rumble strip, positioning the alert mechanism closer to the travel lane. This design aims to alert drowsy or distracted drivers earlier than traditional shoulder rumble strips and enhances edge-line visibility during nighttime and wet conditions. The research was conducted under the Federal Highway Administration’s Evaluation of Low-Cost Safety Improvements Pooled Fund Study to provide quantitative crash modification factors (CMFs) and benefit–cost (B/C) ratios for transportation agencies. The researchers utilized an empirical Bayes (EB) before–after analysis to assess crash data from treated sites in Kentucky and Ohio. This methodological approach accounted for selection bias, regression-to-the-mean, changes in traffic volumes, and unrelated time trends in crash counts by using reference groups of untreated rural horizontal curves with similar characteristics. The analysis specifically isolated the effects on horizontal curves, excluding tangents, intersection-related crashes, and animal crashes. Due to a simultaneous statewide curve warning sign upgrade in Ohio, the results for the two states were analyzed separately rather than combined. The findings demonstrated statistically significant reductions in crashes for both states. In Kentucky, ELRSs reduced total crashes by 25% (CMF 0.75), injury crashes by 36% (CMF 0.64), run-off-road (ROR) crashes by 26% (CMF 0.74), and nighttime crashes by 37% (CMF 0.63). In Ohio, the treatment resulted in significant reductions across all crash types, with CMFs of 0.79 for total and injury crashes, 0.78 for ROR crashes, 0.75 for nighttime crashes, and 0.71 for nighttime ROR crashes. Disaggregate analysis suggested larger safety benefits for curves with higher average annual daily traffic (AADT) and higher pre-treatment crash frequencies, though differences by AADT were not statistically significant at the 95% confidence level. The study concluded that ELRSs are a highly cost-effective safety countermeasure. Estimated B/C ratios ranged from 189:1 to 467:1 for Kentucky and 272:1 to 672:1 for Ohio. These high ratios are attributed to the corridor-wide installation costs being applied to the specific safety benefits observed on horizontal curves, which have inherently higher crash rates. While curve-specific installations would likely yield lower B/C ratios due to higher per-mile deployment costs, the results confirm that ELRSs significantly reduce crash frequency and severity on rural two-lane horizontal curves, supporting their implementation as a low-cost safety improvement.
Key finding
Edge-line rumble stripes reduced total crashes by 21 to 25 percent and run-off-road crashes by 22 to 26 percent on rural two-lane horizontal curves in Kentucky and Ohio.
Methodology
field_study
Provenance
The full processing record for this entry. Every stage of this paper's journey through the pipeline is logged — what ran, with which tool and model, how many attempts it took, and when it last completed. Discovered via bulk_ingest_rosap on 2026-05-23 (6 acquisition events logged).
| Stage | Outcome | Tool | Model | Prompt | Attempts | Completed |
|---|---|---|---|---|---|---|
| discover | success | rosap | — | — | 2 | 2026-05-23 |
| archive | success | — | — | — | 1 | 2026-05-23 |
| extract | success | cached | — | — | 2 | 2026-06-10 |
| clean | success | — | — | — | 1 | 2026-06-01 |
| chunk | success | — | — | — | 1 | 2026-06-01 |
| embed | success | — | — | — | 1 | 2026-06-02 |
| enrich | success | — | — | — | 1 | 2026-05-23 |
| promote | success | — | — | — | 1 | 2026-05-23 |
| summarize | success | llm | qwen3.6-27b-prismaquant | summ-v5 | 3 | 2026-06-10 |
| tag | success | vector_similarity | — | — | 19 | 2026-06-11 |
| verify | success | — | — | — | 2 | 2026-06-10 |
Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.
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Information type
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- Applied Guidance: countermeasure evaluation
- Empirical Findings: crash risk outcomes