Evaluation of Retroreflective Sheetings for Use on Traffic Control Devices at Construction Work Zones

Ahmed, Samir A. · 1991 · ROSA P / Oklahoma. Department of Transportation

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Summary

This 1991 study by Samir A. Ahmed, conducted for the Oklahoma Department of Transportation and the Federal Highway Administration, evaluates the relative adequacy of three retroreflective sheeting grades—engineering, super-engineering, and high-intensity—for traffic control devices in construction work zones. The research was motivated by the critical need to ensure driver visibility, particularly for elderly motorists with diminished visual acuity, while balancing durability and economic constraints. Existing guidelines lacked empirical evidence regarding the performance limitations of these sheetings, leaving engineers to rely on subjective judgment. The primary objective was to determine which sheeting grade best met driver visibility needs, durability requirements, and economic efficiency for signs, barrels, barricades, and vertical panels. The methodology comprised six tasks: a literature review, controlled field experiments, real-world field experiments, accelerated weathering tests, a contractor survey, and an economic analysis. Field experiments involved 239 drivers across urban, rural, and controlled sites, measuring detection and recognition distances during both day and night. Drivers also completed questionnaires assessing device adequacy. Accelerated weathering tests compared sheeting performance against ASTM standards. A survey of Oklahoma traffic control contractors gathered data on service life, deterioration modes, fabrication issues, and costs. Economic analysis calculated the cost per year of service life and cost per project for each sheeting type. Results indicated that high-intensity grade sheeting provided the highest target value and detection distances, particularly in urban settings. However, it suffered from significant drawbacks, including glare complaints from drivers, lower durability, and higher costs. Super-engineering grade sheeting offered superior legibility for signs at night compared to high-intensity and engineering grades, with daytime recognition distances comparable to high-intensity but significantly better than engineering grade. For barrels and barricades, upgrading from engineering to super-engineering or high-intensity grades significantly increased conspicuity. Contractor surveys revealed that engineering grade was the most durable and easiest to fabricate, while high-intensity grade was prone to handling issues and had the shortest service life. Economic analysis showed high-intensity grade was the most costly, whereas super-engineering grade offered a cost-effective balance, with costs similar to engineering grade for most devices but lower than engineering grade for barricades. The study concludes that super-engineering grade sheeting is the most adequate choice for traffic control signs in both urban and rural construction projects, offering a balanced tradeoff between visibility, durability, and cost. While high-intensity grade provides higher detection values, its benefits are offset by glare, poor durability, and high expense. For barrels, barricades, and vertical panels, upgrading from engineering to super-engineering grade is recommended as the most cost-effective solution to improve detection and recognition distances. High-intensity grade may still be warranted in specific urban locations with excessive visual clutter or background lighting, but super-engineering grade is generally preferred for its practicality and performance.

Key finding

Super-engineering grade sheeting is the most cost-effective and balanced solution for traffic control devices at construction work zones, offering superior legibility and durability compared to high-intensity grade while providing significantly better visibility than engineering grade.

Methodology

mixed_methods

Sample size: 239

Provenance

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Topics

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• sign visibility legibility
• vehicle conspicuity
• emergency work zone conspicuity
• signage environment