Public Roads: A Journal of Highway Research and Development, Vol. 37. No. 7

True, Justin; Rosen, Dan; Byington, Stanley R.; Rosenbaum, Merton J.; Irick, P.E.; Mobley, Arthur B.; Greig, Robert A.; Armstrong, William L. · 1973 · ROSA P / United States. Government Printing Office

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Summary

This article introduces the "moving merge" control system, a novel approach to freeway entrance ramp management designed to assist drivers in merging safely with mainline traffic. The research addresses the high accident rates and driver difficulties associated with merging, particularly at ramps with poor visibility, short acceleration lanes, or complex geometries where reconstruction is impractical. While conventional ramp metering systems regulate traffic volume to prevent congestion, they do not directly aid the driver in identifying safe gaps. The moving merge system operates on the "gap acceptance" principle, using vehicle detectors and computers to identify adequate spaces in the freeway’s right lane and communicating this information to ramp drivers via rampside displays. The study details the development and testing of two prototype systems—the "pacer" and the "green band"—conducted by the Raytheon Company in cooperation with the Federal Highway Administration and the Massachusetts Department of Public Works. These systems were tested on the Route 38 entrance ramp to Route 128 in Woburn, Massachusetts. Both systems utilized pavement-embedded loop detectors to monitor freeway and ramp traffic, feeding data to a Raytheon Model 703 computer. The pacer system used a series of sequential green lights to pace the driver’s speed, while the green band system illuminated moving bands of green light representing acceptable gaps. Both systems operated in a "moving mode" during light traffic and a "stopped mode" during peak congestion, where vehicles were held at a signal until a gap was found. Results from driver questionnaires indicated that approximately 80 percent of users found the systems helpful in improving merging positions. Drivers expressed a clear preference for the green band system, citing it as easier to understand and more economical than the pacer system. Based on these findings, the article describes the selection of the Ashley Street entrance ramp to Interstate 75 in Tampa, Florida, for a permanent experimental installation of the green band system. This site was chosen due to its severe merging challenges, including an elevated structure with no shoulder and a short acceleration lane. The Tampa project involves a multi-agency collaboration, including the University of Florida and the City of Tampa, to evaluate the system’s long-term viability in reducing accidents and improving traffic flow at problematic interchanges.

Key finding

Approximately 80 percent of drivers found moving merge control systems beneficial, with a preference for the green band system which was deemed technically feasible and more economical than the pacer system.

Methodology

mixed_methods

Sample size: 210

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

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• perceptual countermeasures
• rail grade crossings
• work zones

Information type

What kind of knowledge this paper contributes, grouped by family — independent of topic (what it is about) and method (how it was studied).

• Applied Guidance: countermeasure evaluation
• Empirical Findings: observational prevalence
• Methodological Resource: dataset resource