Comprehensive assessment of side friction impacts on urban traffic flow: A case study of Hilla City, Iraq

Abstract This study provides a comprehensive evaluation of the impact of side friction (SF) elements on urban traffic flow in Hilla City, Iraq, with a particular focus on how both static and dynamic SF elements such as parked vehicles, pedestrian activities, and irregular vehicular entry–exit maneuvers affect traffic performance and road capacity. The research aims to address the gap in the literature regarding the combined effects of these elements, particularly in rapidly urbanizing cities with diverse traffic conditions. Using data collected from strategically positioned video cameras on four key urban roads, the study analyzes traffic behavior during peak and off-peak hours over multiple days. The Roadside Friction Index and Friction units were employed to quantify the intensity of SF impacts, and regression models were developed to predict changes in traffic behavior under varying SF scenarios. Findings indicate that high levels of SF can lead to significant reductions in vehicle speeds by up to 49% during peak hours, emphasizing the need for targeted interventions. Practical recommendations include stricter parking regulations, the enhancement of pedestrian infrastructure, and the integration of SF data into Intelligent Transport Systems for real-time traffic management. This research provides valuable insights for urban planners and policymakers in developing effective traffic management strategies that mitigate the adverse effects of SF and enhance road safety and efficiency in rapidly developing urban environments.