High reliability of railway power systems is one of the essential criteria to ensure quality and rncost-effectiveness of railway services. Reliability analysis of traction power supply system rn(TPSS) is essential for identifying reliability critical components, which causes most of the rndisruptions, and providing necessary mitigation techniques. rnThe service quality of Addis Ababa Light Rail Transit Service (AALRTS) has repeatedly been rnaffected by the TPSS component failures that results in part routing, passenger clearing and more rnseverely operation interruption. Thus, analysis and improvement of AALRT TPSS reliability is rndefinitely an important and urgent issue. rnThe main objective of this thesis is conducting the qualitative and quantitative reliability analysis rnof AALRT TPSS. Fault mode and effect analysis (FMEA) and fault tree analysis (FTA) rnaccompanied by exponential distribution are selected to model the system and evaluate the rnreliability indices. The reliability evaluation indexes of AALRT TPSS are then calculated via rnMATLAB code by applying the exponential distribution equations. rnAccordingly, the reliability analysis showed that AALRT TPSS had poor reliability in the rnmission time of about three years. Hence, reliability mitigation techniques, such as fostering well rntrained personnel, applying various maintenance approaches, procuring and localizing high rnquality components, and introducing standby power systems, to improve the poor reliable rntraction power supply system operation, are suggested.