Comprehensive Investigation of Visibility Problems on Highways: Developing Real Time Monitoring and Prediction System for Reduced Visibility and Understanding Traffic and Human Factors Implications

Rodgers, Michael O.; Wilson, Alana M.; Schaffer, Kaitlyn G. · 2017 · ROSA P / Georgia. Dept. of Transportation. Office of Materials & Research

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Summary

This study addresses the significant safety hazards posed by reduced visibility on Georgia’s highways, driven by fog and smoke-enhanced fog (non-photochemical smog). Georgia ranks fifth nationally for reduced-visibility-associated crash frequency, with historical incidents including a major 125-vehicle pileup on I-75N. The research was motivated by the need to understand the spatial and temporal distribution of these visibility events to inform road weather management and safety treatments. The primary objective was to create an initial fog climatology for the state using historical data to anticipate the frequency of fog and smoke occurrences. The methodology involved analyzing data from Automated Weather Observing System/Automated Surface Observing System (AWOS/ASOS) units and fire frequency data from the National Oceanic and Atmospheric Administration (NOAA) and the Georgia Forestry Commission (GFC). A visibility event was defined as any 20-minute interval with recorded visibility less than 5/8 statute miles. The researchers employed Kriging interpolation in ArcGIS to generate fog frequency maps across the state for the period 2014–2016. Additionally, the study calculated the fraction of time major Interstate highways were impacted by reduced visibility during each season. The report also reviewed fog formation mechanisms, types of fog (radiation, advection, frontal, upslope), and existing detection and advisory technologies. The results indicate that visibility hazards in Georgia correlate strongly with topography and season. Fog frequency was highest during the fall season, with the greatest regional impacts observed in the North Georgia mountains and along the coast. Analysis of Interstate corridors revealed that visibility reduction was most prevalent in winter and fall. For example, I-75S experienced reduced visibility 1.72% of the time in winter and 0.80% in fall, while I-95 saw 1.70% in winter and 1.26% in fall. Summer visibility impacts were lowest across all corridors, generally ranging between 0.27% and 0.58%. The study also mapped fire frequency, noting that smoke contributes to visibility reduction, particularly when combined with fog. The significance of this research lies in its provision of the first comprehensive fog climatology for Georgia, identifying specific high-risk corridors and seasons. The authors conclude that the observed frequencies of reduced visibility are high enough to warrant safety countermeasures. They recommend that the Georgia Department of Transportation (GDOT) conduct higher-resolution evaluations of specific roadway segments, particularly I-95 in Coastal Georgia, I-16 from Savannah to Metter, state routes in the North Georgia Mountains, and routes crossing reservoirs. Furthermore, the study suggests revising design policies to include provisions for reduced-visibility treatments in these designated locales to mitigate crash risks.

Key finding

Fall seasons exhibited the highest frequency of reduced visibility events across Georgia, with North Georgia mountains and coastal regions experiencing the greatest regional impact.

Methodology

dataset

Provenance

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

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• weather rain fog snow