Analysis of Operational Capacity Of Selected Rotary Intersections in Obio/Akpor local Government Area, Rivers State

Abstract

This research investigates the capacity of major rotary intersections within Obio/Akpor Local Government Area, with emphasis on Agip and Eliozu rotary intersections. Data were obtained through manual traffic volume count, spot speed studies, and geometric measurement of each intersection. The analysis employed the Highway Capacity Manual (HCM 2010) procedures, to estimate entry capacities, delays, and levels of service. Traffic volume count and analysis was carried out at the intersections and converted to Equivalent Passenger Cars Unit per hour (PCU/hr). Thus, Agip  intersection generates a traffic volume of 3217 PCU/hr with a practical rotary capacity of 3069 PCU/hr. Eliozu intersection also generates a traffic volume of 4051 PCU/hr with a practical capacity of 2131 PCU/hr. These capacities generated by these intersections are higher than the recommended rotary capacity of 3000 PCU/hr given by the Indian Road Congress (IRC) making the present design of rotary intersections inadequate and incapable of handling the present traffic set-up leading to traffic problems. Analysis carried out on the four approaches of Agip intersection revealed that they are under saturated with degree of saturation of 0.26 (26%), 0.31 (31%), 0.42 (42%), and 0.29 (29%) for the North, East, South and West approaches. This is an average of about 0.66 (66%) below 0.85 (85%) of recommended traffic demand. Meanwhile analysis carried out at Eliozu intersection revealed that they are also under saturated with degree of saturation of 0.51 (51%), 0.38 (38%), 0.36 (36%), and 0.35 (35%) for the North, East, South and West. This is an average of about 0.40 (40%) below 0.85 (85%) of recommended traffic demand.  The study therefore recommends an improved design of the intersection, and stop to illegal trading, and improvement of alternative routes leading to the intersection.