Performance analysis of urban road intersections and its environmental implication - a case study of the Lagos metropolitan area

Abstract

Urban road intersections are a major factor that influences the effectiveness of traffic flow systems. This paper is aimed at examining the performance of road intersections in the Lagos metropolitan area using the “Y-junction” of OgaIkorodu (Lagos, Nigeria) as the case study. The study examines the delay factors, time wastage and traffic conflicts. The study uses a reconnaissance survey, delay analytical tool, vehicle spot speed study and traffic volume survey to assess the level of delay, economic loss and traffic flow interruption. The study reveals that there are varying Levels of Service (LOS) obtainable at different times of the day on different carriageways, while Ayangburen Road records the best LOS of B in the morning, the afternoon and evening recorded C and D respectively. A different scenario holds for both Lagos and Sagamu as they record the worse LOS of E in the evening peak. In a related manner, the percentage of vehicle stoppage falls between 41.1%–87.8% indicating that vehicles tend to experience a stop scenario than not-stop at each approach especially during the peaks. It is therefore pertinent to note that the road intersection operates at a very low level of service especially during the evening peak when controlled by traffic wardens. It is therefore recommended that a Diamond-at-grade intersection be constructed in the area instead of the round-a-bout. The introduction of an automated traffic control system with full control of access and total removal of on-street parking will remove the road users’ burden in that area.