Evaluation of ground mounted diagrammatic entrance ramp approach signs : research implementation plan.

Zwahlen, Helmut T. · 2006 · ROSA P / Ohio Research Institute for Transportation and the Environment. Human Factors and Ergonomics Laboratory

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Summary

This research implementation plan evaluates the effectiveness of ground-mounted diagrammatic entrance ramp approach signs on urban multi-lane arterials leading to freeways. The study was motivated by the need to provide drivers with advance information regarding interchange geometry, thereby allowing more time for necessary lane changes. The primary objective was to assess these signs based on driver information acquisition, behavior, safety, and traffic throughput. The study specifically isolated the effect of sign content rather than brightness by ensuring that "before" condition signs were new or nearly new, and by leaving signs at the interchange itself unchanged. The research was conducted at six highway-freeway interchanges in the Greater Columbus, Ohio area. The methodology employed a "before" and "after" field study design. Traffic flow video footage was collected prior to the installation of the diagrammatic signs and repeated after installation. This footage was automatically analyzed using Mobilizer PC software to extract vehicle count, speed, and headway data. These metrics served as inputs for a closed-form analytical model designed to calculate the probability of drivers successfully changing lanes before reaching the freeway entrance gore. Additionally, eye movement recordings were conducted at night at all six sites to assess potential visual distraction. The theoretical model was further validated using data from additional interchange evaluations involving unfamiliar test drivers. The findings indicated that the presence of ground-mounted diagrammatic signs significantly improved driver performance. Theoretical analysis showed a much higher probability of successful lane changes for unfamiliar drivers when these signs were present. Empirical data from test drivers corroborated this, demonstrating that drivers executed needed lane changes much earlier with the diagrammatic signs. Regarding safety and distraction, eye movement analysis revealed that drivers did not look at the signs excessively often or for excessive durations. The overall median first look distance to the signs was 125 meters. Furthermore, evaluations by ODOT and FHWA officials resulted in strong support for the implementation of these signs, with the vast majority of evaluators embracing the concept. The significance of this study lies in its validation of ground-mounted diagrammatic signs as an effective treatment for improving traffic flow and safety on freeway approaches. The research supports the development of standard sign designs and specifications, which were scheduled for completion by December 31, 2006. The findings suggest that these signs provide critical advance information without causing driver distraction, thereby enhancing the efficiency of lane changes and reducing potential conflicts near interchange entrances. The results were disseminated through a final report available online and distributed to state departments of transportation and national repositories, facilitating broader adoption of this traffic engineering practice.

Key finding

Drivers executed needed lane changes earlier with ground-mounted advance diagrammatic signs, and the signs drew a median first-look distance of 125 m without excessive glances.

Methodology

field_study

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