Evaluation of ground mounted diagrammatic entrance ramp approach signs : final report, October 2000.

Zwahlen, Helmut T.; Schnell, Thomas · 2000 · ROSA P / Ohio Research Institute for Transportation and the Environment. Human Factors and Ergonomics Laboratory

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Summary

This study evaluates the effectiveness of ground-mounted diagrammatic entrance ramp approach signs in improving driver navigation and safety at highway-freeway interchanges. The research was motivated by the limitations of conventional trailblazer assemblies, which provide minimal advance notice of lane requirements, often leading to erratic last-minute lane changes, reduced throughput, and increased traffic volume due to missed entrances. While overhead diagrammatic signs are effective, they are costly; this project investigated whether ground-mounted alternatives could provide similar benefits at a lower cost, building on successful implementations in Europe and previous U.S. studies. The research was conducted at six highway-freeway interchanges in the Greater Columbus, Ohio area. The methodology involved a multi-faceted approach: first, traffic flow video footage was collected before and after the installation of the experimental diagrammatic signs. This data was analyzed using Mobilizer PC software to extract vehicle counts, speeds, and headway gaps, which served as inputs for a closed-form analytical model to calculate the probability of successful lane changes. Second, eye movement recordings were performed at night to assess visual attention and potential distraction. Third, twenty unfamiliar test drivers were monitored in instrumented vehicles to measure actual lane change behavior. Finally, ODOT and FHWA evaluators provided expert opinions on the signage. The results demonstrated significant improvements in driver performance. The theoretical analysis indicated a much higher probability that unfamiliar drivers could successfully execute required lane changes when diagrammatic signs were present. This was corroborated by the test driver evaluation, which showed that drivers executed necessary lane changes much earlier with the new signage compared to the conventional system. Eye movement analysis revealed that the signs were not excessively distracting; drivers did not look at them too frequently or for too long, with an overall median first-look distance of 125 meters. Expert evaluators overwhelmingly supported the use of diagrammatic signs. The study concludes that ground-mounted diagrammatic entrance ramp approach signs are an effective, cost-efficient alternative to overhead signing for providing advance guidance to unfamiliar drivers. By enabling earlier and safer lane changes, these signs reduce erratic maneuvers and improve interchange throughput. The report provides specific application guidelines for implementing these signs, supporting their adoption to enhance safety and efficiency at complex freeway interchanges.

Key finding

Drivers executed required lane changes significantly earlier and with higher probability when ground-mounted diagrammatic signs were installed compared to conventional trailblazer assemblies.

Methodology

field_study

Sample size: 20

Provenance

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

Topics

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• signage environment
• perceptual countermeasures
• sign visibility legibility
• rail grade crossings
• signaling behavior