A study to mitigate rural high-speed horizontal curve crashes in Kansas.

Momeni, Hojr; Russell, Sr., Eugene R.; Rys, Malgorzata J. · 2015 · ROSA P / Kansas. Dept. of Transportation. Bureau of Materials & Research

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Summary

This study addresses the persistent safety challenge of rural high-speed horizontal curve crashes in Kansas, which account for approximately 25% of all fatal highway crashes despite comprising a small fraction of roadway mileage. The research was motivated by the need to identify effective, low-cost countermeasures to reduce crash frequency and severity on these hazardous segments. The authors aimed to evaluate existing safety treatments and analyze the impact of specific interventions, such as speed limit reductions, on crash outcomes. The methodology utilized a nine-year Kansas Department of Transportation (KDOT) crash database spanning 2004 to 2012. Researchers identified eleven counties with high numbers of horizontal curve-related crashes and analyzed implemented countermeasures at selected sites. A primary case study focused on K-5 Highway in Leavenworth County, where the speed limit was reduced from 55 mph to 50 mph in June 2009. The effectiveness of this reduction was evaluated using a statistical t-test comparing crash occurrences over a seven-year period, comprising 3.5 years before and 3.5 years after the intervention. The study also conducted a comprehensive literature review of low-, intermediate-, and high-cost treatments, including pavement markings, signage, rumble strips, and geometric improvements. Key findings indicate that navigating horizontal curves imposes significant workload on drivers, often leading to speed misjudgment and run-off-road incidents. The analysis of K-5 Highway demonstrated that the speed limit reduction had a measurable effect on crash occurrences, though the specific statistical significance details are summarized through the application of the t-test method. The literature review highlighted that low-cost countermeasures, such as centerlines, edge lines, chevron alignment signs, and advisory speed signs, are critical for providing visual cues and guiding driver behavior. Specifically, chevrons were noted as strong guidance cues for anticipatory control, while pavement markings provided the strongest curvature guidance. The study also detailed the costs and effectiveness of various treatments, noting that combinations of measures, such as markings with rumble strips, often yield improved safety outcomes. The significance of this research lies in its contribution to evidence-based transportation safety planning. By linking specific countermeasures to crash data, the study provides KDOT and other agencies with actionable insights for mitigating rural curve crashes. The findings support the implementation of targeted, low-cost interventions like improved delineation and speed management to address the disproportionate number of fatalities occurring on horizontal curves. The report concludes with recommended countermeasures for specific curve types, emphasizing the importance of design consistency and adequate driver warning systems to reduce workload and prevent crashes.

Key finding

The statistical t-test analysis was used to evaluate the effect of the speed limit reduction on crash occurrences, though the specific numerical result of the test is not explicitly stated in the provided text.

Methodology

dataset

Provenance

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Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

Topics

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• road geometry
• perceptual countermeasures
• roadway lighting effects
• rail grade crossings

Information type

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• Empirical Findings: crash risk outcomes