PURPOSES : In this study, the relationship between the types of road pavement markings and the visibility distance under adverse weather conditions was evaluated. METHODS : Rainy and foggy conditions at the weather proving ground were replicated in this study. The researchers recorded the visibility distance corresponding to each experiment scenario comprising the weather conditions and pavement marking types. RESULTS : Visibility distances under adverse weather conditions decreased more than those of normal weather conditions. Under rainy conditions, the average visibility distance across all pavement markings decreased by 33%. However, the average visibility distance across all pavement markings foggy conditions decreased by 46.8%. Based on the test results of the visibility distance, the speed reduction rates corresponding to the adverse and normal weather conditions, i.e., 24% and 36% speed reduction under rainy and foggy conditions, respectively, were established. CONCLUSIONS : This study validated the reduction in the visibility distance affected by weather conditions by applying actual road scale weather proving ground. In addition, speed reduction was recommended for safe driving under adverse weather conditions.

Temporal and spatial characteristics of the frequency of several weather types and the change in air pollutant concentrations according to these weather types were analyzed over a decade (2007-2016) in seven major cities and a remote area in Korea. This analysis was performed using hourly (or daily) observed data of weather types (e.g., mist, haze, fog, precipitation, dust, and thunder and lighting) and air pollutant criteria (PM10, PM2.5, O3, NO2, CO, and SO2). Overall, the most frequent weather type across all areas during the study period was found to be mist (39%), followed by precipitation (35%), haze (17%), and the other types (≤ 4%). In terms of regional frequency distributions, the highest frequency of haze (26%) was in Seoul (especially during winter and May-June), possibly due to the high population and air pollutant emission sources, while that of precipitation (47%) was in Jeju (summer and winter), due to its geographic location with the sea on four sides and a very high mountain. PM10 concentrations for dust and haze were significantly higher in three cities (up to 250 μg/m3 for dust in Incheon), whereas those for the other four types were relatively lower. The concentrations of PM2.5 and its major precursor gases (NO2 and SO2) were higher (up to 69 μg/m3, 48 ppb, and 16 ppb, respectively, for haze in Incheon) for haze and/or dust than for the other weather types. On the other hand, there were no distinct differences in the concentrations of O3 and CO for the weather types. The overall results of this study confirm that the frequency of weather types and the related air quality depend on the geographic and environmental characteristics of the target areas.