Investigation of Rainfall Impact on Traffic Characteristics of Urban Roads

Adverse weather conditions such as rainfall, significantly affect road safety and traffic performance by altering surface conditions and driver behavior. This study aimed to investigate how varying intensities of rainfall influence key traffic characteristics and the resulting stopping sight distance (SSD) on the Kabale–Kisoro road in Uganda. Using rainfall data from the Kabale meteorological station, the study categorized rainfall into low, moderate, and heavy intensities. Traffic data were collected during both dry and rainy conditions and analyzed to determine changes in speed, flow, density, and headway. A comparative analysis was then used to assess the impact of these changes on SSD. The findings reveal that increasing rainfall intensity consistently reduces mean speed, traffic flow, and critical speed, while increasing time headway. Consequently, stopping sight distance is significantly reduced under wet conditions, highlighting the heightened safety risks posed by rainfall. These results underscore the need for adaptive traffic management and road design strategies that account for weather variability in regions prone to frequent rainfall.