Improving Traffic Flow in Emerging Cities: A SIDRA Intersection Based Traffic Signal Design

Adeleke, Oyetunde Oluwafemi; Oguntayo, Daniel Oluwafemi; Ayobami, Iyunade Tiwalade; Ogunkunbi, Gabriel Ayobami · 2023 · OpenAlex-citations

DOI: 10.3311/pptr.18018

archive: archived pipeline: cataloged verified

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Summary

This study addresses the critical issue of traffic congestion and safety at unsignalized intersections in emerging cities, specifically focusing on the Gaa-Akanbi intersection in Ilorin, Nigeria. The authors argue that intersections are primary conflict points where inefficient traffic discharge leads to significant delays, accidents, and socioeconomic costs. In Nigeria, the absence of functional traffic signals often results in manual control by traffic wardens, which is inefficient. The research aims to design an effective fixed-time traffic signal scheme to optimize traffic flow, reduce delays, and enhance safety at this specific T-intersection located in the Central Business District. The methodology involved a comprehensive field study and software-based design. First, the geometric layout of the intersection was surveyed using a Total Station and measuring tape to determine lane widths, lane counts, and distances to nearby intersections. Second, a 12-hour classified traffic count was conducted manually over seven days in May 2019, with data recorded at 15-minute intervals. The traffic data, categorized into five vehicle classes (motorcycles, tricycles, light vehicles, buses, and heavy vehicles), was converted to Passenger Car Units (PCU) using Nigerian highway manual specifications. The authors used SIDRA Intersection 8.1 software to design the signal timing, adhering to the Highway Capacity Manual (HCM) methods. The design targeted a Level of Service (LOS) "D" using the minimum delay method, incorporating the peak hour volumes and movement patterns identified in the field study. The results indicate that the intersection experiences high traffic volumes, particularly on weekdays, with light vehicles comprising approximately 52% of the total flow. The analysis justified signalization based on multiple warrants, including peak hour volume and vehicular volume. The study proposes a 3-phase traffic signal plan with an optimum cycle length of 150 seconds. The specific timing includes an amber time of 6 seconds for all phases, with green times of 48, 46, and 38 seconds for phases 1, 2, and 3, respectively. The designed signal achieves a degree of saturation of 0.983 and an average delay of 97.5 seconds. The critical movements were identified as 1↔2, 2↔3, and 3↔1. The proposed scheme ensures that the intersection operates at LOS "D," providing a comfortable experience for road users while minimizing delay. The significance of this study lies in its practical application for improving urban mobility in developing nations. By replacing manual control with a scientifically designed signal system, the authors demonstrate that traffic efficiency can be significantly enhanced. The proposed signalization is expected to reduce delays, decrease fuel consumption, and lower pollutant emissions. The study concludes that the metropolitan traffic management agency should adopt this design to improve traffic management at the Gaa-Akanbi intersection, serving as a model for similar unsignalized intersections in emerging cities.

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Topics

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• intersection design