Essay: Replacing a roundabout with a signalized intersection using VISSIM

1. Introduction
1.1. Background
The Accra- Kumasi- Gonokrom Road, classified by the Ghana Highway Authority as Route N6, is one of the major roads in Ghana of international importance within the West African sub-region it forms a vital link between Ghana and La Cote d’Ivoire as well as other countries using the port facilities in Ghana for trans-shipment of freight. Since the beginning of the political conflict in La Cote d’Ivoire in 2003, Route N6 has come under increased use by heavy-goods vehicles (HGVs) as a number of the landlocked neighbouring countries, which hithero had been using the port facilities in Abidjan, have now diverted to the use of the port facilities in Ghana for obvious reasons. To improve safety and traffic flow on the route, a 50km section of the road leading to the Kumasi Metropolis approaching from Accra was rehabilitated with a granted from the Danish government
To ease congestion on the approaches to the metropolis, a 12.4km portion of the section loading to the metropolis was redesigned as a four lane divided highway. As part of the rehabilitation, four intersections within and abutting the metropolis were redesigned as modern roundabouts. The first roundabout on the section, sniveling away from the Kumasi Metropolis in the direction of Accra, is located adjacent to the Kwame Nkrumah University of Science and Technology (KNUST) Police Station, it replaced a four-legged intersection formed by a minor road from the university which crosses Route N6. The second, located at the intersection of route N6 and the Boadi Road and the third at the intersection of the N6 and the Anwomaso Road both replaced intersections which were originally T-intersections. The fourth, located within the Ejisu Township also replaced a four-legged intersection
1.2. Problem Statement
The ending growth of the socio-economic needs of the nation has given rise to an increase in vehicle ownership and as such there’s congestion at intersections and road links. The single lane circulation roundabout is normally congested during the morning and evening peak periods of the day. Long vehicular queues are observed to be formed on the approaches of the roundabout. This results in undesirable delays in traffic. This undermines the performance of the roundabout as well as its safety and. The delays also adversely affect the cost of travel as more fuel is consumed. This study analyses the traffic situation at a roundabout on the Osei-Tutu Boulevard of the Accra-Kumasi-Gonokrom highway (Route N6) within Kumasi and determines how much more feasible it would be to use a signalized intersection.
1.3. Justification
The outcome of this project would give a means of:
‘ providing relief to drivers who use the roundabout,
‘ reduce noise and fumes within the study area,
‘ provide design parameters that would cater for future growth.
Findings from this project will serve as a foundation for using VISSIM for the assessment of other roundabouts within Kumasi and the country.
1.4. Aims and Objectives
The objective of this project:
‘ is to model the current condition at the roundabout and replace the roundabout in this model with a signalized intersection using VISSIM, a microscopic multi-modal traffic flow simulation software.
‘ use VISSIM to assess and compare the traffic parameters and determine the factors that contribute to delay at the stated intersection.
‘ make recommendations as to which of the two forms of intersections would be more efficient.