ASSESSMENT OF SELECTED ROUNDABOUTS IN AKURE, ONDO STATE, NIGERIA

Abstract

Assessment of facilities will enhance functionality and reduce/eradicate abuse. The objective of this work is to evaluate selected roundabouts in Akure, Ondo State, Nigeria. Lack of proper design, insufficient installation and lack of basic geometric features of modern roundabout contribute to roundabout failure. Looking at different approaches to roundabout design and analyses from different parts of the world, (France, United State of America, Australia, Germany, and United Kingdom) whose roundabouts are designed to operate at no more than 85 percent of the estimated capacity is the ultimate value for a reliable and functional roundabout. The most important element of operational performances of roundabout intersections is the capacity which is often expressed in terms of degree of saturation i.e demand volume over Capacity ratio (v/c) of 0.85 and the standard of the geometric features. The roundabout method adopted for the analysis evaluation in this thesis is based on the highway capacity manual 2010 approach which evaluates the entry capacities of these roundabouts based on each lane. This approach, which uses both roundabout geometry along side the users’ behaviours was adopted because it eliminates some roundabout geometric elements that were not found on some of the roundabouts in the selected study area. Approach entry capacity was analysed for each leg of the selected roundabout and the results obtained presented. After the redesign of the roundabouts at Hospital road, Owena motel and Oluwatuyi, it was observered that only the roundabout at Oluwatuyi can still function appropriately as a roundabout even when motorcycle is still allowed to ply the major roads around town. The roundabout at Hospital road and Owena motel both failed to accommodate the traffic at some of the legs because these legs are in the threshold of exceeding the required traffic flow recommended for roundabouts. Hence, a more detailed analysis of both roundabouts is recommended. Traffic data of intersections in Akure and environs should be regularly collected by the transport department of the Ondo state government for regular evaluation of intersection in Ondo state. However a well built modern roundabout can reduce travel time, delay and increase capacity