Evaluation of retroreflective sheetings for use on traffic control devices at construction work sites (FHWA-OK-91-06) 2177

Abstract

The overall objective of this project was to evaluate the relative adequacy of the engineering grade, super-engineering grade, and high-intensity grade sheetings when used on traffic control devices at construction work zones. Evaluation criteria included driver visibility needs, durability and economics, and other practical considerations. To meet the objectives of this project, a research plan consisting of literature review, controlled field experiments, real-world field experiments, accelerated weathering tests, survey of Oklahoma traffic control contractors, and economic analysis was adopted. The results of these tasks formed the basis for the findings and conclusions of this study. While the high-intensity grade sheeting has the highest target value of the three sheeting grades, the tradeoff between detection and legibility of traffic control signs was interpreted to favor the use of the super-engineering grade on signs in both urban and rural construction projects. Durability, economics, and other practical issues emphasized by traffic control contractors support this conclusion. Nevertheless, use of the high-intensity grade sheeting in urban construction projects may be warranted at locations with visual clutter and excessive background lights. The beneficial effects of upgrading the type of sheeting used on barrels, barricades, and vertical panels from engineering grade to high-intensity grade or super-engineering grade were demonstrated by the significant increase in both the detection and recognition distances of these devices. Yet, the benefits of upgrading to the high-intensity grade were found to be offset by the significant increase in cost, the less durability of the sheeting material, and the problems with fabrication and handling. Upgrading to super-engineering grade offers the most cost-effective and balanced solution.