EVALUATING ROAD CAPACITY BASED ON TRAFFIC FLOW OF URBAN SEGMENT IN ADDIS ABABA CITY, ETHIOPIA

Abstract

Estimation of road capacity is one of the fundamental requirements for designing, operation, layout planning and management of a road network system. Capacity values play an important role for further modification of roads. Various geometric measures like road width and traffic patterns related to different roads. For the present study six midblocks were selected of them four were multilane with 7 km road length and two were two lane length of 1.2 km directional traffic study were done in Addis Ababa city. Traffic volume count was conducted on all these six midblocks from morning 7:00AM to 6:00PM for eleven hours. Meanwhile speed study was also conducted during both peak and non-peak hour period. Road inventory survey was done to determine width of the road, median, capacity estimation was done on basis of space mean speed and traffic volume (PCU/hr). Passenger car equivalents (PCE) are used for road capacity analysis with heterogeneous traffic conditions. Mathematical model is developed which uses field measured variables on which multiple regression analysis is performed by using SPSS software for capacity values provided for urban roads. Relation between capacity and road width, percentage of heavy vehicles, road side activities were developed and identified that drives capacity effecting zones. This relation helps in studying variation with respect to various capacity affecting variables. Level of service (LOS) was found out in all selected midblocks based on HCM criteria among each midblock. As shown traffic data collected from the field the midblock are congested during peak periods. The level of service (LOS) of the entire stretches was found to be at the level of service E during the entire survey.