User-centered Smart Traffic Sign Development Study

Morris, Nichole L.; Rajamani, Rajesh; Drahos, B D; Zhenming, X; Alexander, L.; Kessler, William · 2023 · ROSA P / Minnesota. Department of Transportation. Office of Research & Innovation

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Summary

This study addresses the critical safety issue of work zone intrusions, where flaggers protecting maintenance workers are at high risk of being struck by distracted or aggressive motorists. Motivated by the high fatality rates among road workers and the limitations of existing smart signage systems—which are often too cumbersome, expensive, or confusing for drivers—the research aimed to develop a low-cost, automated intrusion detection system. The primary goal was to create a device that could alert drivers approaching unsafely while minimizing the physical risk to flaggers who must stand in the roadway. The project employed a user-centered design approach, beginning with a human factors assessment of maintenance workers. Workers expressed a preference for a modified traffic signal over traditional STOP/SLOW signs, citing driver confusion regarding the requirement to "stop and remain stopped" and the danger of flaggers standing in traffic. Consequently, the engineering team developed a portable traffic signal prototype equipped with low-cost radar sensors, embedded electronics, and audio-visual alarms. The system used radar to track vehicle trajectories, estimate position and velocity, and detect potential intrusions. Usability testing was conducted in two phases using an immersive driving simulator. The first phase compared the experimental traffic signal against a traditional flagger. The second phase iteratively improved the design, incorporating high-visibility borders and an audiovisual alarm into a modified STOP/SLOW flagger paddle to enhance conspicuity and clarity. Initial simulator results indicated that drivers had lower compliance and higher stop failure rates with the experimental traffic signal compared to a traditional flagger, though the auditory alarm helped some drivers correct initial stopping errors. However, the iterative design significantly improved performance. In the second phase, the audiovisual-enhanced STOP/SLOW flagger system demonstrated near-perfect compliance, with no initial stop failures for drivers encountering it first and only one failure for those encountering it second. Furthermore, the rate of drivers stopping but failing to remain stopped dropped from 22.8% with the traditional flagger to 10% with the alert system. Engineering tests validated the sensor system’s capability to simultaneously track multiple vehicles within a 60-meter range and 120-degree azimuth, correctly detecting all staged intruding vehicles in experimental trials. The study concludes that an audiovisually enhanced STOP/SLOW flagger system, rather than a standalone traffic signal, is the most effective embodiment for this technology. The findings suggest that integrating automated alerts into familiar signage improves driver understanding and compliance, thereby enhancing worker safety. The authors recommend advancing the alert STOP/SLOW system to field implementation studies to assess real-world efficacy, worker acceptance, and the impact of environmental noise on the auditory alarms. This work provides a validated, low-cost pathway for improving work zone safety through user-centered smart signage.

Key finding

An audiovisually enhanced STOP/SLOW flagger paddle with an automated intrusion detection alarm demonstrated superior driver compliance and safety compared to a modified traffic signal prototype in simulated work zone conditions.

Methodology

simulator

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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• emergency work zone conspicuity
• signage environment
• vru facing ehmi
• ehmi external hmi
• sign visibility legibility
• signaling behavior

Information type

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• Methodological Resource: tool software, validation psychometrics