For flexible pavement design Ethiopia uses the existing load equivalency factor method which was adopted from oversea road note 31and it was empirically derived using sub grade strain criteria. In this method only axle load is considered as a parameter for equivalent axle load factor calculation. But in the existing literatures there are different parameters such as overloading, tire inflation pressure and transversal road slope. Due to leaving these factors the flexible pavement damage is underestimated. The damage exponent value in the existing LEF method is assumed to be 4.5 and valid for all pavement structures. Since the thickness and stiffness of the pavement layers has impact on its values a representative pavement layer sections should be considered. In this study a LEF method has been developed by considering axle load including overloading, tire pressure, camber slop and pavement considering Ethiopian conditions. In this study a secondary traffic axle load data from ERA and the tire inflation pressure of 100 trucks was surveyed by the author using tire inflation pressure gun on two truck parking stations was considered. The camber slop values (2.5%, 3%, 4% and 8%) have been assumed from ERA 2013 manual. For tire inflation pressure correction factor, a selected pavement sections are extracted from ERA flexible pavement design manual 2013 for both thickness and modulus criteria. The camber slop correction factor is developed by considering a truck-trailer truck type using mathematical equations. For damage exponent value estimation 41 pavement sections has been considered. The tensile strain at the bottom of the asphalt layer and vertical compressive strain at the top of sub grade layer was analyzed using KENPAVE software. Adjustment factor of tire pressure coefficient (Ktp) and damage exponent values are calculated using fatigue and rutting criteria. Based on the analysis result, the Ktp value for fatigue failure criteria was found higher than rutting failure criteria. The camber slop correction factor was estimated from free body diagram using mathematical equation and its value was 1.10, 1.13, 1.16 and 1.41 for camber slop values of 2.5%, 3%, 4% and 8% respectively. The damage exponent (n) value for rutting and fatigue failure case is found a power relation. For validating the developed model a comparison of load equivalency factor values between the developed and existing load equivalency factor method was made. The root mean square mean value (RMSE of 2.44%) was found and it shows that the adjusted load equivalency factor method can be reasonably used for design traffic load estimation for flexible pavement design. Key Words: Equivalent Axle Load Factor, KENPAVE, Damage Exponent 1