Highway Signing Research: Phase II, Characterization of Sign-Facing Materials

Funnell, J. E.; Curtice, D. K. · 1966 · ROSA P / Southwest Research Institute

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Summary

This 1966 report by the Southwest Research Institute, conducted for the Texas Highway Department and the U.S. Bureau of Public Roads, addresses the inadequacy of existing performance specifications for highway sign-facing materials. The research was motivated by a lack of standardized, objective criteria for evaluating the serviceability, durability, and visual effectiveness of reflective signs. The study aimed to characterize commercially available sign materials to define objective performance criteria and examine test procedures that could reliably evaluate these materials under various environmental conditions. The investigation employed a combination of laboratory testing and field exposure studies. Researchers focused on three primary generic classes of retroreflective facings: flat-surface flexible sheeting, exposed-lens flexible sheeting, and beads-on-paint non-sheeting types. Backing materials, including plywood, steel, and aluminum, were also examined due to their influence on facing performance. The experimental design included photometric evaluations using a specialized 60-foot testing tunnel to measure reflective intensity at various divergence and incidence angles. Physical and mechanical properties were assessed through tests for abrasion resistance, adhesion, flexibility, thermal stability, cleanability, impact resistance, and tensile strength. Additionally, materials were subjected to accelerated laboratory tests and outdoor exposure racks in diverse climatic locations, including San Antonio and South Florida, to monitor deterioration mechanisms and weatherability. The findings indicated significant inadequacies in current specifications, particularly regarding the definition of service requirements. The study established that dry and wet reflectance should be the primary basis for rating sign performance, as these metrics directly correlate with brightness, brilliance, and contrast between lettering and background. Most changes in material performance resulting from treatments and exposures could be correlated through photometric measurements. While color plays a role in sign identification, the report concluded that fixing definite color values in performance specifications was unnecessary, though standardized calibration methods for comparing retroreflective color data across facilities were deemed essential. The research also highlighted that existing test methods and equipment were often insufficient for evaluating materials against objective criteria, leading to the development or modification of several testing procedures. The significance of this work lies in its contribution to a better understanding of the character, behavior, and performance of sign-facing materials. By identifying the relationship between material characteristics, deterioration mechanisms, and sign effectiveness, the study provided a foundation for formulating more robust specifications and test methods. The report pointed to areas requiring further study, including factors influencing durability and use-life expectancy, the development of improved instrumentation for photometric determinations, and the effects of nationwide service conditions on material longevity. Ultimately, the research supported the need for standardized, repeatable testing procedures to ensure the competitive purchase and satisfactory performance of highway signing materials.

Key finding

Dry and wet reflectance measurements provide the most effective basis for rating sign performance and serviceability, as they correlate directly with material deterioration and visual effectiveness.

Methodology

mixed_methods

Provenance

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

Topics

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• sign visibility legibility
• vehicle conspicuity
• signage environment
• roadway lighting effects