Tadesse, Samuel (PhD)Abate, Asnake2018-06-202023-11-112018-06-202023-11-112015-03http://etd.aau.edu.et/handle/12345678/1996Most of the roads constructed in Ethiopia fail prematurely before serving the design life due to various causes arising from many factors. One of these roads failed before reaching design life time is the Addis Ababa-Modjo Trunk Road. The Addis Ababa-Modjo road is approximately 50 km trunk road and very crucial for the country’s transportation and tourism sector as it is the main import export corridor to and from the capital, Addis Ababa. The road carries the highest daily traffic in the country. This road was constructed and opened to traffic in the year 2000. The design pavement life was estimated 15 years, however; pavement structure failure have been manifested since 2005, within the first 5 years after opening to traffic. From end of 2007 to date the Addis -Modjo trunk road is repeatedly under periodic maintenance. Considerable resources have been spent during this period for periodic maintenance but without solving the basic problem. This maintenance is not working as each maintained section is failing with in short period, hence, it needs finding the root causes of the failure to come up with appropriate solution. Field and laboratory investigations which include visual condition survey, Benkelman Deflection measurement, test pitting and pavement layer profiling, materials sampling and testing have been conducted in order to investigate causes of failure moreover, the past traffic data was collected and analysed. Finally based on the investigation, expansive subgrade soil, side drain problem, workmanship problems, use of substandard materials are found to contribute for the pavement failure. However, it is noted that the traffic load take the highest share for the cause of pavement failure. Proper treatment of expansive subgrade soil, use of quality construction materials, proper maintenance design based on the forecasted traffic are recommended as mitigation measures. Key Words: Pavement Failure, Condition Survey, Traffic Loading, Maintenance, Benkelman Beam, Deflection.enKey Words; Pavement Failure; Condition Survey; Traffic Loading;Maintenance; Benkelman Beam;Deflection