Effect of Land Use and Mixed-use on Traffic Congestion at Urban Intersections: Implications for Transportation Planning

Abstract

Abstract Land-use patterns play a crucial role in trip generation and spatial demand, leading to high traffic congestion in urban areas due to a rapidly increasing population. Today, the urban movement in Baghdad is paralyzed by heavy traffic congestion at major intersections, and this crisis is closely linked to poor integration between land use as an essential factor in transportation planning, and traffic modelling and management. Traditional models, however, concentrate more on traffic volume and less on the dynamics of functionality in an urban setting. This gap is addressed by incorporating Mixed Use (MU) into traffic performance modelling to investigate its influence on “Traffic congestion” (measured as back-of-queue length). The approach used a two-phase Multiple Linear Regression (MLR) analysis with 120 independent observation periods at high-density intersections. Traffic flow inputs were validated rigorously by comparing outputs from the SIDRA Intersection software and the Highway Capacity Manual (HCM 2010) methods with traffic footage. By using an Entropy Index to measure functional diversity (Mixed use), the research extended the range of simple density measurement on involving mixed use effects on intersection capacity. The results prove that the inclusion of mixed-use variables significantly improve model performance (from R2=0.613 to R2=0.840). A main outcome from this research is that contrary to classical urban theory, in Baghdad, higher land-use diversity causes more congestion. This “Mixed Use Paradox” is caused by natural functional overlaps and gross underinvestment in infrastructure that causes shaping “functional friction” at-grade intersections. Additionally, the research points out that commercial density and high volume “trip bursts” of people driving to school from an educational (or college) zone act as major contributors to delays and are exacerbated by excessive through traffic pushing past smaller local facilities. These results are important for transportation planning and indicate that simply expanding roads will not solve Baghdad’s traffic woes. What we need, rather, is an approach that coordinates heterogeneous land use with intelligent traffic signalization and structural deconcentration to address the functional overlap that currently clogs the city’s network.