Determination of Passenger Car Unit for Urban Roads: A Case Study in Addis Ababa

Abstract

In Ethiopia, specifically on Addis Ababa city roads operating, vehicles are mixed with varying static and dynamic traffic characteristics that are very challenging for the traffic analyst to come up with a sole solution to the traffic malady. Under heterogeneous traffic, each vehicle type cannot be compared with other vehicle types since it shows different effects on the road. During the field observations, most of the drivers in Addis Ababa road networks did not follow proper lane discipline to use any available space on the road sections. Currently, Ethiopia is using the passenger car unit values from other countries' manuals, which don't represent the local traffic and roadway conditions. This study was initiated to establish the passenger car unit (pcu) to cater to the regional settings. Hence, the study's focus was to estimate the pcu values of multilane highways in Addis Ababa city and determine the influence of traffic volume and width of the road on the importance of pcu. The passenger car units were estimated for four vehicle types based on traffic volume and carriageway width variation. Dynamic PCU method was used to determine values and performed a Linear Regression analysis for model development. The developed model was used to estimate pcu values having the same traffic and roadway conditions in other countries. Results indicated that as the traffic volume and carriageway width increase, the passenger car unit also increases. Also, this study found out that pcu values were higher than those provided in Highway Capacity Manual. Hence, the pcu values obtained are recommended to reflect the existing traffic condition in the locality.