Integrated American-European protocol for safety interventions on existing two-lane rural roads

Colonna, Pasquale; Intini, Paolo; Berloco, Nicola; Ranieri, Vittorio · 2017 · Crossref

DOI: 10.1007/s12544-017-0274-4

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Summary

This paper addresses the lack of standardized, quantitative methods for designing safety interventions on existing two-lane rural roads, particularly those not included in the Trans-European Network (TEN). While the EU Directive 2008/96/EC mandates safety management for TEN roads, it does not provide clear quantitative tools for minor rural roads, which often lack local Safety Performance Functions (SPFs) and Crash Modification Factors (CMFs). The study aims to integrate qualitative assessments (audits, inspections) with quantitative accident predictions to create a unified protocol. The primary research questions focus on identifying practical problems in applying such a protocol, determining necessary data requirements, and proposing solutions for these challenges. The authors developed an integrated operational protocol combining the Highway Safety Manual (HSM) predictive methods, EU regulations, local road design standards, and specific research developments. The protocol is structured into stages: network screening, diagnosis, and countermeasure selection. The screening stage utilizes the Level of Service of Safety (LOSS) method to assess a site’s safety relative to predicted accident frequencies. The diagnosis stage involves reconstructing road geometry, identifying homogeneous segments, analyzing accident history via collision diagrams, comparing existing conditions against design standards, evaluating skidding risk using the Friction Diagram Method, and conducting detailed road inspections. The protocol was applied to real two-lane rural road segments in the Puglia Region of Italy, which exhibited high accident frequencies. Results were compared with existing Italian SPFs to evaluate transferability and practical applicability. The application of the protocol highlighted several critical problems and corresponding solutions. Key issues included a lack of high-quality local data, difficulties in comparing existing road conditions with current standards to identify specific safety deficits, and the absence of methods for evaluating skidding risk along complex road layouts. The study also identified challenges in setting appropriate speed limits and optimizing the selection of countermeasures based on their specific aims and timely application. Furthermore, the availability and comparison of predictive methods posed significant hurdles, particularly regarding the transferability of SPFs and CMFs from other jurisdictions. The authors noted that while locally derived functions generally fit data better than calibrated foreign models, the cost and time required for local studies often make transferring existing methods necessary. The study concludes that the integrated protocol offers significant advantages, including a systematic approach to safety analysis, the ability to quantitatively assess the benefits of interventions, and potential transferability to other contexts lacking local data. However, the main disadvantages involve the difficulties in overcoming data scarcity and the challenges of calibrating accident prediction models to local conditions. The protocol provides a practical framework for practitioners to assess safety performance and design interventions on existing rural roads, bridging the gap between qualitative regulatory requirements and quantitative safety engineering needs.

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Summary generated by qwen3.6-27b-prismaquant on 2026-06-26; verification: verified.

Topics

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• perceptual countermeasures
• comparative international
• incidence prevalence
• regulatory evaluation
• roadway lighting effects

Information type

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• Applied Guidance: countermeasure evaluation, standards test procedures
• Empirical Findings: crash risk outcomes