Distinct track irregularities contribute a large impact on the vibrations of a railcar fromrndifferent railway lines. However, the track irregularities and track stiffness will alterrnover time due to the loading and environmental conditions. The measurements of railrnirregularities are required to assess and to determine their impact on railcar vibrations.rnIgnoring these can significantly increase future maintenance costs on both vehicle andrntrack. Therefore, this research is about assessing the impact of track irregularities on thernrail vehicle vibration for the case of Addis Ababa Light Rail Transit(AALRT). Thernequations of motion of the half railcar model with 12 dof have derived analytically andrnsolved using MATLAB. The irregularities used as excitation input to the MATLABrnmodel were measured along the track segment of AALRT lines at an interval of 150 mrneach using a universal railway measuring ruler gauge for the track. For simplicity andrnwithout loss of generality, the MATLAB model neglected the Hertzian contact effects.rnOn the other hand, the Finite Element Method (FEM) was used to validate thernanalytical model equations by using modal analysis of the 3D railcar bogie. The naturalrnfrequencies provided by FEM are compared with those obtained using lumpedrnparameter models. Then, the effect of suspension parameters on the railcar vibrationrnbehaviour was investigated. The carbody responses of 14.89Hz and 13.89Hz fromrnMATLAB and ABAQUS respectively. The match of frequencies in both modelsrnprovided confidence in the correctness of the analytical model. These frequencies are inrnthe range of human sensitivity to vibrations, which is 0 to 20Hz as specified by ISOrn2631. Thus, the vertical suspension components are very critical in vibrations of thernlight rail vehicle and should be maintained regularly. It was also found that sleeperrnstiffness variation has a small impact on vertical vibration responses on the railcar. Thernresearch output may help to reduce the maintenance cost of the railcar by minimizingrnthe impact of track irregularities on rail vehicle vibration.