A Handbook for Signal Design: Alarms, Alerts, and Warnings in Air Traffic Control

Ruskin, Keith J; Rice, Stephen; Ruskin, Anna Clebone · 2022 · ROSA P / United States. Department of Transportation. Federal Aviation Administration. Human Factors Division

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Summary

This report presents the preliminary draft of a handbook designed to guide the creation and modification of alarms, alerts, and warnings (signals) in Air Traffic Control (ATC). The research addresses the challenge of "alarm fatigue" and the "cry-wolf effect," where high rates of false alarms and nuisance signals degrade controller trust in automation and impair performance. The authors, affiliated with the University of Chicago and Embry-Riddle Aeronautical University, draw on parallels between ATC and anesthesiology to establish a signaling philosophy aimed at enhancing situation awareness, reducing cognitive workload, and maintaining safety within the National Airspace System. The methodology involves a comprehensive review of human factors literature, analysis of Aviation Safety Reporting System (ASRS) reports, and structured interviews with subject matter experts. The core contribution is a novel signal design framework that provides a common language for designers, engineers, and controllers. This framework categorizes signals into four priority levels based on the required intervention: Priority 1 (immediate danger), Priority 2 (risk of harm), Priority 3 (informational), and Priority 4 (diagnostic/equipment failure). The design process utilizes an objective scoring sheet and structured interviews to evaluate signals across fifteen properties organized into five categories: HOW, WHAT, WHERE, WHEN, and WHAT. Key findings and recommendations include the need for signals to be unique, prioritized, timely, understandable, and relevant. The handbook advocates for enhancing signal efficacy through multimodal approaches, such as using acoustically rich auditory signals (e.g., earcons, spearcons) that encode urgency and are easily localizable, particularly in noisy environments. Visual signals should utilize shapes in addition to colors to account for environmental limitations, such as bright lighting in control towers. The report also suggests that automation should indicate its confidence level in a hazard and allow controllers to suppress auditory signals while maintaining visual data blocks, provided the suppression mechanism does not compromise safety. The significance of this work lies in providing the Federal Aviation Administration with a standardized tool to objectively evaluate and design ATC signals. By establishing clear design principles and a structured evaluation framework, the handbook aims to reduce nuisance alarms, improve controller trust in automated systems, and ensure that signals effectively support critical decision-making. The authors note that while developed for ATC, these signal design techniques may have broad applicability across other safety-critical domains. The framework is intended for validation in subsequent project phases, with the ultimate goal of keeping the National Airspace System safe through improved human-system interaction.

Key finding

The study proposes a four-priority signaling framework and a structured design handbook to objectively evaluate and improve air traffic control alarms, alerts, and warnings.

Methodology

review

Provenance

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

Topics

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• auditory warnings
• warning design
• signal detection theory
• multimodal feedback

Information type

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• Applied Guidance: design guidelines