Self-Enforcing Roadways : A Guidance Report

Donnell, Eric T.; Kersavage, Kristin; Donnell, Eric T. · 2018 · ROSA P / United States. Federal Highway Administration

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Summary

This guidance report, published by the Federal Highway Administration (FHWA) in 2018, addresses the critical safety issue of speeding-related crashes on two-lane rural highways. The research is motivated by data indicating that over 13,000 people are killed annually in speeding-related crashes, with rural areas accounting for the majority of fatalities and exhibiting a fatal crash rate more than 2.5 times higher than urban areas. Specifically, 65% of speeding-related crashes occur on roadways with speed limits between 45 and 80 mph. The report aims to provide transportation professionals with methods to design or retrofit "self-enforcing" (or self-explaining) roadways—roadways planned and designed to encourage drivers to select operating speeds consistent with posted speed limits, thereby reducing crash severity. The document synthesizes existing literature and engineering principles to identify six specific concepts for achieving self-enforcing roadways. These methods include: (1) the speed feedback loop process, which checks consistency between geometric design elements and anticipated operating speeds during preliminary engineering; (2) the inferred design speed approach, which evaluates the maximum speed for which all design criteria are met; (3) design consistency methods, utilizing operating speed prediction models to establish limits; (4) the application of existing geometric design criteria, leveraging features with known relationships to operating speed; (5) the combination of signs and pavement markings to manage speeds on existing roadways where reconstruction is not feasible; and (6) the setting of rational speed limits using expert systems like FHWA’s USLIMITS2. The report details the step-by-step processes for implementing these concepts, supported by equations for horizontal and vertical alignment, cross-section design, and speed prediction models. To illustrate the application of these methods, the report presents case studies of two rural highways: US Route 6 in Pennsylvania and SR 865 (Rockfish Road) in Virginia. These examples demonstrate the use of the inferred design speed approach, the Interactive Highway Safety Design Model (IHSDM), and USLIMITS2 to analyze speed profiles and design consistency. The analysis compares historical crash data with predicted crashes to evaluate safety performance. The findings emphasize that for new or major reconstruction projects, geometric design methods (speed feedback loop, inferred design speed, design consistency, and geometric criteria) are the most effective strategies and should be incorporated early in the planning process. For existing roadways where major reconstruction is not planned, retrofits using signs and pavement markings are recommended. The significance of this report lies in its provision of a structured framework for integrating speed management into roadway design. By aligning operating speeds with posted limits through geometric design and traffic control devices, the report suggests that less severe crash outcomes can be achieved. It concludes that while the specific safety performance of these methods is not yet fully quantified, the implied outcome of effective speed management is a reduction in crash severity. The guidance serves as a practical tool for state departments of transportation and researchers to mitigate speeding-related fatalities on moderate- and high-speed rural highways.

Key finding

Six self-enforcing road concepts are identified and described to guide the geometric design of two-lane rural highways to produce operating speeds consistent with posted speed limits.

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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• road geometry
• speed management
• speed choice
• perceptual countermeasures
• roadway lighting effects
• rail grade crossings

Information type

What kind of knowledge this paper contributes, grouped by family — independent of topic (what it is about) and method (how it was studied).

• Empirical Findings: crash risk outcomes