Evaluation of the Monitor-CTA Automatic Vehicle Monitoring System

Miller, Harold G.; Basham, William M. · 1974 · ROSA P / United States. Urban Mass Transportation Administration

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Summary

This 1974 report evaluates the Chicago Transit Authority’s (CTA) Monitor-CTA Automatic Vehicle Monitoring (AVM) system to determine its technical validity and whether federal funding for its expansion was justified. Conducted by the Department of Transportation’s Transportation Systems Center (TSC) from July to August 1972, the evaluation assessed the system’s operational status, schedule adherence, accuracy, response rates, reliability, and cost benefits. The Monitor-CTA system uses radio transmitters at fixed points ("signposts") and onboard bus units to track vehicle location and elapsed time, allowing central dispatchers to monitor schedule adherence in near real-time. The evaluation revealed significant technical and operational deficiencies that rendered the system non-operational. Schedule and headway adherence tests on three routes showed no significant improvement over non-monitored buses, attributed to biased data, dispatcher inability to effectively control buses, and favorable summer traffic conditions. Technical testing identified a mean accuracy error of +0.5 minutes and a low valid response rate of 52% during night shifts, with 26% of monitored buses failing to respond entirely. Reliability analysis indicated that while most subsystems were adequate, the bus receiver-transmitter units were inadequate, with a Mean Time Between Failures (MTBF) of only 80 days compared to an estimated one year. Operationally, dispatchers lacked confidence in the data, faced union jurisdiction issues, and struggled with an inadequate console design that hindered effective analysis and control. Despite these operational failures, the cost-benefit analysis concluded that the system represented a sound financial investment. The projected net present value of savings, primarily from reducing supervisor staff, was $5,657,930, with the system paying for itself within six years regardless of schedule adherence improvements. However, the authors argued that the system’s long-term goal should be operational command and control rather than mere cost reduction. Consequently, the report recommends that further government funding be withheld until specific corrective actions are taken: redesigning the display and control hardware/software, training dispatchers in analytical rather than reactive modes, increasing technical support staff, improving the reliability of bus receiver-transmitter units, and conducting new adherence tests. Until these steps are completed, the Monitor-CTA system cannot be considered fully operational.

Key finding

The Monitor-CTA system was deemed non-operational due to inadequate receiver-transmitter reliability and low response rates, although cost-benefit analysis projected a positive return on investment within six years.

Methodology

field_study

Provenance

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

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• dms validation

Information type

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• Applied Guidance: countermeasure evaluation