The Factors that Affect the Free Flow Speed on an Arterial in Ilorin, Nigeria

Abstract

Generic factors (weather, environment, vehicles, fixed roadway characteristics, pedestrian and traffic streams) singly or jointly influence the free flow speed. This paper, therefore, presents the outcome of the quantitative evaluation of the influence of these factors on the free flow speed on an arterial in a medium-sized urban settlement in Nigeria. Instantaneous speeds of forty test vehicles were observed at lull periods on the 7.1km-Offa Garage-Emir’s Road, Ilorin, with simultaneous collection of data on drivers’ and vehicle ages, passenger occupancy, roadside parked vehicles and businesses. The geometric properties of the arterial were earlier established and segmented to four uniform sections. Result of computations using the category and statistical analysis show that the environment, pedestrian and roadway geometry have negative influences on the free flow speed. This can be confirmed by the poor relationship between free flow speed and these factors, with R2 values of 14.9-55%, and lower average free flow speed of commercial saloon cars on wet pavement than on dry pavement, with 12% percentage reduction. Adoption of design and analysis of traffic stream in Ilorin and other urban settlements in Nigeria is, therefore, recommended.