Public Roads: A Journal of Highway Research and Development, Vol. 39 No. 2

Tignor, Samuel; Hess, Joseph W.; Moore, Kenneth R.; Clear, Kenneth C.; Nelson, David S.; Allen, William L. Jr.; Cron, Frederick W. · 1975 · ROSA P / United States. Government Printing Office

archive: archived pipeline: cataloged verified

Get this paper ↗ (full text — opens at the source; we link to it, we don't host it)

Summary

This issue of *Public Roads* presents two distinct research efforts by the Federal Highway Administration (FHWA) aimed at improving highway infrastructure efficiency and durability. The first article addresses the operational inefficiencies of diamond interchanges in urban areas, where heavy traffic demand often leads to congestion. The second article tackles the premature deterioration of concrete bridge decks caused by reinforcing steel corrosion, focusing on the development of rapid, nondestructive inspection tools. The diamond interchange study, conducted in cooperation with the California Department of Transportation and the City of Los Angeles, utilized simulation models and field tests to optimize traffic signal control. Researchers developed both microscopic and macroscopic simulation models to analyze geometric design and signal timing. They derived a new fixed-time signalization methodology by combining Webster’s and Inose’s algorithms, which was validated against field data from 160 interchanges. Field tests at the Western Avenue and Santa Monica Freeway interchange in Los Angeles employed TRADAC instrumentation to measure travel time, stopped time, and stops. Additionally, a prototype real-time control system using a Varian 620 I minicomputer and 49 inductive loop detectors was developed and tested to adapt signal timing to changing traffic demands. The bridge deck study focused on creating a "Rolling Pachometer" to expedite the measurement of concrete cover over reinforcing steel. Traditional hand-held pachometers were found to be tedious and slow. The FHWA, in collaboration with the Oklahoma State Department of Highways, developed a mobile system featuring a modified hand-held pachometer, a battery-operated strip chart recorder, and a speedometer. The device operates at a constant speed of 1 mph, recording magnetic flux variations as it passes over rebar. Field evaluations in Oklahoma, Pennsylvania, and West Virginia compared the Rolling Pachometer against hand-held units and core samples. The device proved accurate and capable of gathering data 20 times faster than conventional methods, though researchers noted a constant bias effect caused by magnetite in concrete sand, which requires calibration correction via coring. The findings demonstrate significant improvements in both domains. For diamond interchanges, the new fixed-time methodology reduced average travel time, stopped time, and number of stops despite increased traffic demand. The real-time control system further reduced total delay by 25 percent compared to existing systems and by 11 percent compared to the improved fixed-time method. The study also found that a minimum configuration of 18–20 detectors could achieve similar benefits, with installation costs estimated between $66,000 and $91,000. For bridge decks, the Rolling Pachometer provided a reliable, efficient tool for quality control and inspection, allowing for rapid identification of rebars outside specified depth tolerances. These advancements offer practical solutions for enhancing traffic flow in congested urban interchanges and extending the service life of concrete bridges through better monitoring of corrosion risks.

Key finding

Total delay was reduced by 25 percent when a real-time control system was used compared to fixed-time control at the tested diamond interchange.

Methodology

mixed_methods

Provenance

The full processing record for this entry. Every stage of this paper's journey through the pipeline is logged — what ran, with which tool and model, how many attempts it took, and when it last completed. Discovered via bulk_ingest_rosap on 2026-05-23 (6 acquisition events logged).

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

Topics

Ranked by relevance to this paper. Hover a topic for its definition.

• perceptual countermeasures
• rail grade crossings
• roadway lighting effects
• signage environment