Speed management toolbox for rural communities.

Hallmark, Shauna L.; Hawkins, Neal; Knickerbocker, Skylar · 2013 · ROSA P / Iowa. Dept. of Transportation

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Summary

This report presents a "Speed Management Toolbox" designed to assist rural communities in managing vehicle speeds, particularly within transition zones where drivers enter built-up areas from rural highways. The primary objective is to summarize the effectiveness, placement, advantages, disadvantages, and costs of various roadway-based traffic-calming treatments. The research was conducted by the Center for Transportation Research and Education at Iowa State University, sponsored by the Iowa Department of Transportation, the Federal Highway Administration, and the Midwest Transportation Consortium. The study focuses exclusively on physical and visual roadway treatments, excluding education, enforcement, and policy strategies, though it acknowledges their potential complementary role. The methodology involved a comprehensive review of existing literature, analysis of prior research by the authors, and consultations with transportation professionals. The identified treatments were categorized into seven strategies: horizontal physical displacement, vertical physical displacement, narrowing, surroundings, pavement markings, traffic control signs, and other strategies. For each treatment, the report provides detailed summaries including Crash Modification Factors (CMFs) where available, which estimate the percentage change in crashes or speed reductions associated with specific countermeasures. The report emphasizes that these estimates are generic and must be adjusted for site-specific conditions, adhering to the Manual on Uniform Traffic Control Devices (MUTCD) and local guidelines. The findings detail specific treatments within each category. Horizontal physical displacement includes bulb-outs, chicanes, realigned intersections, roundabouts, and mini-roundabouts. For instance, roundabouts are noted to reduce crashes significantly, with CMFs indicating up to a 65% reduction in serious or minor injury crashes compared to traditional intersections. Chicanes were found to reduce the 85th percentile speed by approximately 6% in some studies. Vertical displacement treatments, such as speed humps and tables, provide physical feedback to drivers. Narrowing strategies, including center islands and shoulder widening, psychologically compel drivers to reduce speed. Surroundings and pavement markings, such as community gateways, banners, and optical speed bars, serve to alert drivers to speed changes. The report highlights that while some treatments like roundabouts have high installation costs and right-of-way requirements, others like pavement markings are low-cost but may have reduced effectiveness. The significance of this toolbox lies in providing a structured, evidence-based resource for transportation agencies and rural communities to select appropriate speed management strategies. By consolidating information on treatment effectiveness, costs, and appropriateness, the report aids in making informed decisions that balance safety improvements with practical constraints. It underscores the importance of judicious application to avoid driver disregard and unnecessary maintenance costs. The inclusion of CMFs allows for quantitative assessment of safety benefits, supporting the integration of traffic calming into broader rural safety programs. This resource is particularly valuable for communities seeking to enhance safety at transition zones without relying solely on enforcement measures.

Key finding

The report provides a catalog of specific traffic-calming treatments with associated effectiveness data, such as a 2.6 mph speed reduction for narrowing treatments and a 51 percent crash reduction for roundabouts, rather than conducting new empirical field tests.

Methodology

review

Provenance

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

Topics

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• speed management
• perceptual countermeasures
• signage environment