Assessment of Drainage Structures and Their Impact on Traffic Flow Along an Urban Arterial Road Corridor

Abstract

The condition of drainage infrastructure along urban arterial roads is vital to the performance of the transportation system. Poor or blocked drainage leads to flooding, pavement deterioration, and increased congestion, especially during peak hours. This study assessed the drainage system and its impact on traffic flow and road performance along the 3.3 km University of Ibadan (UI) First Gate to Nigeria Institute of Social and Economic Research (NISER) corridor in Ibadan, Nigeria. Twelve structures (two bridges and ten culverts) were inventoried and rated as Good, fair, poor, or very poor. Traffic volumes were recorded over six days during morning and afternoon peak hours, with data collected at 15-minute intervals and categorized by vehicle type. Volume-to-capacity (v/c) ratios and Level of Service (LOS) were calculated for north- and south-bound approaches. Only six drainage structures (50%) were rated good, one (8.3%) fair, and five (41.7%) poor, with issues such as blocked box culverts, cracked bridge piers, and clogged drains. The southbound lane had the highest traffic (68,682 vehicles), a v/c ratio of 1.75, and LOS E, indicating unstable flow. The study recommends immediate rehabilitation, desilting, unblocking culverts, and additional drainage to meet current demands. This action, along with road redesign and transportation improvements, is essential to restoring service on this high-traffic corridor.