New Orleans Vessel Traffic Service Watchstander Analysis

Devoe, Donald B.; Royal, J. W.; Abernethy, C. N. · 1979 · ROSA P / United States. Coast Guard

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Summary

This 1979 interim report by the U.S. Department of Transportation’s Transportation Systems Center analyzes the performance and workload of watchstanders at the New Orleans Vessel Traffic Service (NOLA VTS). The study was motivated by the need to understand human factors in VTS operations to improve current services and plan future ones, specifically focusing on how watchstander skills affect the quality of traffic advisories intended to prevent collisions and groundings. The research team conducted a field study at the NOLA VTS from April 10–14, 1978, supplemented by data from October 1977. Methods included 13 hours of direct observation of watchstander activities, timed measurements of tasks, collection of center logs and forms, and photographs of workspace layouts. Additionally, the team conducted 10 in-depth interviews with center personnel, 11 critical incident interviews, and administered stress questionnaires to 11 watchstanders. The NOLA VTS is a voluntary system covering the Mississippi River and associated channels, divided into four sectors monitored by watchstanders using VHF-FM radio and computer-generated Cathode Ray Tube (CRT) displays. Notably, the center lacked direct radar or television surveillance, relying instead on vessel reports and automatic dead-reckoning updates. The analysis revealed that during peak daylight traffic, approximately 100 vessels were underway with a 75% participation rate. Watchstanders spent 39 minutes per hour on communications (22% of duty time) and 26 minutes on computer tracking activities (34% of duty time). Monitoring, job-related conversation, and non-job-related activities accounted for the remaining 30%. Interviews identified three primary operational concerns: poor participation by mariners, a lack of positive surveillance capabilities, and communication problems. Stress questionnaire results indicated appreciable stress levels among watchstanders, largely attributed to low confidence in the accuracy of advisories due to incomplete or erroneous user inputs, the absence of direct surveillance, and communication difficulties. The study concluded with eight recommendations to improve operations. The highest priority was assigned to acquiring surveillance aids, such as radar or closed-circuit television, to provide positive monitoring. Other suggestions included redesigning sector boundaries to match transmitter capabilities, reassigning radio channels to reduce interference with lock transactions, enhancing computer display capabilities for vessel identification and simultaneous list viewing, and emphasizing the symbolic nature of the radar-simulated display during training. The report noted that while the voluntary nature of the system presented drawbacks, there was no immediate recommendation to make participation mandatory.

Key finding

Watchstanders allocated 34% of their duty time to tracking and computer activities, 30% to monitoring, and 22% to communications, with stress levels primarily driven by lack of confidence in advisories due to incomplete surveillance and user input errors.

Methodology

field_study

Sample size: 11

Provenance

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

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• signal detection theory