The Effect of Nighttime Lighting Systems on Workers’ Visibility and Safety [Tech Transfer Summary]

Ho, Chun-Hsing; Kim, Kyungki · 2025 · ROSA P / Smart Work Zone Deployment Initiative

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Summary

This study addresses the critical safety challenges posed by nighttime work zones, where the fatality rate is three times higher than during the day. While visibility is a primary design priority, many work zones are over-illuminated, creating harmful glare that impairs both construction workers and motorists. The research was motivated by the lack of specific guidelines in existing standards regarding how lighting characteristics—such as glare, luminance, and visibility—and the geometric arrangement of light towers affect visual performance. The primary goal was to identify optimal lighting configurations that maximize visibility while minimizing hazardous glare, thereby improving safety for all users in nighttime construction environments. The research employed a multi-faceted approach comprising a practitioner survey, controlled field experiments, and quantitative and qualitative assessments. The survey gathered feedback from contractors, Department of Transportation (DOT) inspectors, and maintenance crews regarding current lighting practices. Field tests were conducted at the University of Nebraska–Lincoln’s Midwest Roadside Safety Facility, utilizing portable light towers with LED and metal halide sources. Researchers measured photometric parameters, including horizontal illuminance for workers and pavement luminance and vertical illuminance for drivers, at multiple grid points. A glare index was calculated to assess driver safety, while qualitative tests evaluated workers’ ability to perform precise tasks, such as reading construction layouts and tape measures, under various lighting conditions. Key findings revealed that while 68% of respondents were satisfied with current systems, significant issues persisted, with 53% citing insufficient worker coverage and 36% reporting driver glare. These problems were primarily attributed to improper geometric configurations rather than inadequate lamp output. Field experiments identified optimal configurations featuring rotation angles of 40° to 50°, mounting heights of 12 to 13 feet, and aiming angles of 20° to 40°. Under these conditions, workers could read small text at 145 feet (halogen) and perform precise measurements at 300 feet (LED) with acceptable glare. Conversely, unsafe configurations, such as perpendicular orientations (90° rotation) or high rotation angles (130°–160°) with low aiming angles, produced excessive illuminance or unacceptable glare, with Veiling Luminance Ratios exceeding 0.4. Properly configured LED towers reduced insufficient illuminance points by approximately 47% and decreased average glare metrics by 20%. The significance of this research lies in its provision of specific, actionable recommendations for lighting design, demonstrating that geometric configuration is more influential than the choice of light source. By prioritizing optimal rotation, aiming, and height settings, agencies can significantly reduce glare and improve visibility. These findings offer supplemental guidance for state DOTs and contractors, supporting updates to lighting standards and promoting safer nighttime work zones. The study concludes that implementing these optimized configurations can enhance the safety and well-being of workers and motorists, particularly benefiting disadvantaged communities often affected by highway construction risks.

Key finding

Optimal nighttime work zone lighting configurations featuring rotation angles of 40° to 50°, mounting heights of 12 to 13 feet, and aiming angles of 20° to 40° significantly reduce glare and improve visibility for both workers and motorists compared to other setups.

Methodology

mixed_methods

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

Ranked by relevance to this paper. Hover a topic for its definition.

• emergency work zone conspicuity
• visibility analysis litigation
• roadway lighting effects
• disability glare
• discomfort glare