Modeling and analyzing of vehicle speed under roadside interactions and traffic stream parameters along the main highway in Finote Selam, Ethiopia
摘要
This study investigates the combined impact of roadside interactions-specifically on-street parking and pedestrian flow-and traffic parameters on vehicle operating speeds along the main highway in Finote Selam Town, Ethiopia. While urban traffic flow is well-researched, the interplay between parking, pedestrians, and vehicles remains poorly understood in low- and middle-income contexts. Using empirical mixed-traffic data, macroscopic modeling, and regression analysis, this research fills that gap. The Greenberg model demonstrated the strongest fit (R2 = 0.695), estimating a free-flow speed of 66.99 km/h and a jam density of 78.24 veh/km. The study found that on-street parking significantly reduces effective capacity: legal parking by 23% and double parking by 27%, culminating in a total 50% loss. Pedestrian flow was the dominant factor reducing speed (0.564 km/h per additional pedestrian), followed by parking occupancy and traffic flow. A quadratic model best captured the speed-flow relationship (R2 = 0.8), revealing a significant concave curve where speed reduction tapers off at high volumes-consistent with platooning and saturation. This nonlinear dynamic reflects congestion behavior and capacity-drop phenomena. Sensitivity analysis confirmed the robustness of this relationship and showed that peak combined conditions of parking, pedestrians, and traffic can reduce speeds by up to 75%, while moderate interactions cause a 34.4% decline, indicating that congestion occurs well before saturation. These findings extend classical speed-flow-density theory by integrating the lateral friction from pedestrians and parked vehicles, underscoring the limitations of traditional models in mixed-traffic environments. Practically, the results support integrated policy strategies, including parking regulation, enhanced pedestrian infrastructure, park-and-ride systems, and adaptive traffic management. The analytical framework offers a transferable approach for similar urban settings across Sub-Saharan Africa and South Asia, aiding evidence-based strategies to improve corridor efficiency, safety, and multimodal mobility.