Comprehensive Review Of Pedestrian And Nmt Roadside Friction Impacts On Heterogeneous Urban Traffic Systems

Urban traffic in developing countries is complex due to heterogeneous traffic, with mixed motorized and non-motorized vehicles (NMVs), poor lane discipline, and roadside friction from pedestrians, bus stops, on-street parking, and commercial encroachments. This review synthesizes 50 studies to quantify impacts on traffic speed and capacity in mixed traffic settings. Pedestrian movements reduce speeds by 0.35 km/h to 67% and capacities by 0–63% (200–5,700 PCU/hr, higher reductions at unspecified volumes), with minimal impact below 220 Peds/hr but significant losses at 1,360 (up to 50%) and 1,550 Peds/hr (up to 40.73%). NMVs and parking reduce speeds by up to 36% and capacities by up to 57%, with lane width reductions causing similar drops. Conventional homogeneous traffic models fail to capture these dynamics, as shown by field observations, VISSIM simulations, headway analysis, and midblock capacity studies. A novel Roadside Friction Index (RSFI) integrates these friction elements, offering urban planners a standardized tool for strategies like bus bays and dynamic parking systems. This enhances urban mobility, aligning with SDG 11 (sustainable cities). Future research should refine the RSFI with real-time data and develop adaptive traffic control to optimize flow in heterogeneous conditions.