A Communications Trade-Off Study for Computerized Traffic Control: Vol. 1, Final Report

Scott, J.; Gordon, R. · 1978 · ROSA P / United States. Federal Highway Administration. Offices of Research & Development

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Summary

This 1978 report, prepared by Sperry Systems Management for the Federal Highway Administration, addresses the need to reduce communication system costs for future computerized urban traffic control systems. The study aims to provide engineers and planners with tutorial material, cost computation procedures, and specification examples to facilitate the selection of optimal communication methods. The research was motivated by the growing complexity of traffic control networks and the significant expense associated with installing and maintaining the communication links required to connect intersection equipment with central control computers. The methodology involved a comprehensive review of fifteen existing or planned traffic control systems to identify common characteristics and communication requirements. The researchers developed function block diagrams for three basic processing architectures: centralized, hierarchical, and network. They examined eight potential communication methods classified by transmission medium, ultimately selecting five as currently applicable: wire pairs (user-owned or leased), coaxial cable, atmospheric optical spectrum (air-path optics), and optical fibers. The study also analyzed various transmission techniques, including frequency-division multiplexing (FDM), time-division multiplexing (TDM), and direct current switching. A trade-off analysis was conducted using cost computation procedures and utility measures, illustrated with examples for each architecture. Additionally, the report provides a detailed example specification for a hierarchical system using wire pairs and air-path optics. The findings indicate that no single communication method is universally optimal; the best choice depends on local conditions, such as terrain, existing infrastructure, and desired traffic control features. Wire pairs, coaxial cable, air-path optics, and fiber optics were identified as viable options. The study found that distributed processing architectures (hierarchical and network) allow for the use of communication methods with lower data rates, potentially reducing costs. Conversely, power lines were deemed unsuitable due to data rate limitations and jurisdictional issues, while baseband microwave radio was rejected due to a lack of demonstrated feasibility. UHF radio spectrum was identified as technically feasible and potentially low-cost but was not yet commercially viable for complete two-way traffic control systems. The significance of this work lies in its provision of a structured framework for evaluating communication trade-offs in traffic control design. The report concludes that while current technologies offer viable solutions, further research and development are necessary to establish the economic and technical feasibility of radio communication techniques in urban environments. Specifically, the authors recommend a development program to address equipment availability and Federal Communications Commission (FCC) authorization for UHF radio systems. The report serves as a practical guide for estimating costs, defining requirements, and specifying communication subsystems, thereby aiding in the efficient deployment of computerized traffic control infrastructure.

Key finding

Viable communication methods for computerized traffic control include wire pairs, coaxial cable, air-path optics, and fiber optics, with the optimal choice depending on local conditions and desired traffic control features.

Methodology

review

Provenance

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

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• v2x connected vehicle