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Article

QUEUE DISCHARGE HEADWAY: CHARACTERISTICS, DISTRIBUTIONS AND EFFECTS ON SATURATION FLOW RATES AT SELECTED SIGNALIZED INTERSECTIONS IN LAGOS

DOI: 10.7708/ijtte2022.12(1).09


12 / 1 / 123 - 139 Pages

Author(s)

Olanrewaju Akinfala - Department of Geography, University of Lagos, Lagos, Nigeria -

Folorunso Ogunwolu - Department of Systems Engineering, University of Lagos, Lagos, Nigeria -

Emmanuel Ege - Department of Geography, University of Lagos, Lagos, Nigeria -

Shakirudeen Odunuga - Department of Geography, University of Lagos, Lagos, Nigeria -


Abstract

Saturation flow rate (SFR) and headway are highly localized essential parameters for accurate and effective performance analysis and optimization of signalized intersections. This study examined the saturation flow rate (SFR) and characterized headways at eight signalized intersection approaches, six of which were ideal while two were typical approaches of Lagos conditions. Over 700 cycle to cycle headway data was collected and analyses such as Fuzzy level 1; statistical tests such as Wilcoxon-Signed rank, Mann-Whitney and Shapiro-Wilks tests were performed on the observed headways. The average SFR observed for ideal approaches was 1,927 veh/hr/lane which is higher than values observed in many developed countries, while at typical approaches, it was 1,342 veh/hr/lane. Statistically, SFR differed significantly during peak and off-peak periods (230 veh/hr/lane) and at ideal and typical approaches (between 460-750 veh/hr/lane). Across all traffic conditions observed, the Burr group of distributions were the overall best fit for modelling headways. A fuzzy-based SFR of 1,789 veh/hr/lane was proposed. This study shows that indeed, headway and SFR differ considerably spatiotemporally. Therefore, appropriate SFR and headway values which reflect actual operating conditions must be adopted to ensure optimal operational performance at signalized intersections.


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