Quantitative Evaluation of Road Heating Systems Using Freezing Intensity (FI) and Cold Intensity (CI): A Case Study in Daejeon, South Korea

Winter road icing poses significant safety risks, particularly on steep urban slopes with vulnerable populations. While thermal-comfort indices such as UTCI, PMV, and PET have been used for summer conditions, this study focuses on operational indices that quantify road-icing risk. This study introduces and empirically validates two novel indices—Freezing Intensity (FI) and Cold Intensity (CI)—designed to quantify the likelihood and severity of road icing. A case study was conducted on Namgyeong-maeul Road in Daedeok-gu, Daejeon, South Korea, where IoT-based environmental monitoring, including automated weather stations, thermal cameras, and drone imaging, was deployed from December 2024 to January 2025. Results demonstrate that road heating systems (RHS) effectively increased surface temperatures by an average of 4.1 °C compared to non-heated segments, with maximum differences exceeding 12.5 °C. The FI of non-heated slopes reached critical levels above 2400, whereas heated roads reduced FI to near zero. Similarly, CI values dropped from hazardous levels (~12) to below 6 in heated zones, reducing icing severity by more than 50%. These findings confirm that FI and CI can serve as robust metrics for operational assessment of RHS performance, complementing traditional heat-related indices. By integrating FI and CI into monitoring and design, policymakers and engineers can establish data-driven activation thresholds, optimize energy efficiency, and ensure safer winter mobility for vulnerable groups. This research provides a structured operational framework for winter road icing quantification, advancing climate adaptation strategies equivalent in rigor to summer climate indices. Compared with temperature-only monitoring, FI and CI improved operational responsiveness and reduced residual icing duration by ≈50%.