Public Roads: A Journal of Highway Research and Development, Vol. 40 No. 1

Smoak, W. Glenn; Miller, Allan S.; Cron, Frederick W.; McGee, Hugh W.; Warren, D.L.; Roberts, King; Klipple, Alfred G.; Horn, Burkhard E.; Diewald, Walter · 1976 · ROSA P / United States. Government Printing Office

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Summary

This issue of *Public Roads* (Vol. 40, No. 1, 1976) presents three distinct studies addressing highway infrastructure durability, safety equipment, and geometric design standards. The first article, by W. Glenn Smoak, addresses the deterioration of concrete bridge decks caused by chloride intrusion from deicing salts. Motivated by the failure of previous protective systems, the study evaluates a polymer impregnation process developed by the Bureau of Reclamation and the Federal Highway Administration (FHWA). The method involves drying newly constructed concrete decks using insulated enclosures and propane heaters, followed by the application of a monomer system composed primarily of methyl methacrylate (MMA) and trimethylolpropane trimethacrylate (TMPTMA). The monomer is allowed to penetrate the concrete before being polymerized through heat activation. A field demonstration on a bridge in Denver, Colorado, confirmed that the process reduced water absorption in the treated zone to less than 1 percent, compared to 9 percent in untreated concrete. Laboratory tests on similar slabs showed resistance to over 200 freeze-thaw cycles without significant chloride buildup. The estimated cost for this treatment is approximately $27 per square yard. The second article, by Allan S. Miller, examines the development of breakaway Type III construction barricades to improve safety for errant vehicles. Traditional wooden barricades were found to be hazardous and difficult to salvage after impact. In response, the Nevada Department of Highways designed a barricade using polyvinyl chloride (PVC) pipe components. Impact tests conducted in 1974 using standard and compact vehicles at speeds up to 55 mph demonstrated that the PVC barricades were superior to wooden ones. The breakaway design allowed components to scatter upon impact, resulting in minimal vehicle damage (minor dents and cracked windshields) and no injuries. Approximately 90 percent of the barricade components were salvageable and reusable. The PVC barricades also offered economic advantages, costing $55.31 each compared to $78.15 for conventional wooden barricades, representing a 29 percent cost reduction. The lightweight design facilitated easy transport and rapid reassembly, though stability required anchoring with fire-extinguisher type U-clamps rather than sandbags. The third article, by Frederick W. Cron, provides a historical review of the development of rational geometric design systems for highways, specifically focusing on curve design and speed determination. It details early 20th-century research by the Bureau of Public Roads (BPR), which sought to establish design standards based on driver comfort and safety. Researchers determined that a side skid coefficient of 0.30 caused uncomfortable side pitch for vehicle occupants. Through road tests involving hundreds of volunteers, the BPR established that a side friction factor of 0.16 was appropriate for design speeds up to 60 mph. The article explains the adoption of the "design speed" concept, defined as the speed adopted by the faster group of drivers, typically corresponding to the 95th or 98th percentile of traffic. This approach replaced previous practices that relied on legal speed limits, allowing for consistent geometric design features such as superelevation and transition curves based on actual driver behavior and vehicle dynamics.

Key finding

Surface impregnation reduced concrete water absorption to 1 percent, PVC breakaway barricades achieved a 29 percent cost reduction compared to wooden ones, and rational geometric design standards were established using 95th percentile driver speeds.

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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• perceptual countermeasures
• roadway lighting effects
• rail grade crossings