Identifying and analyzing crucial parameters that cause accidents in highways, can help improving traffic. This paper addresses a multi-parameteroptimization problem in order to identify the parameters affecting the severityof accidents on highways in Tehran city and uses a combination model ofNeural Network and Genetic Algorithm to perform the analysis. The methodof this research is descriptive-cross-sectional. The statistical population of thisstudy is the accidents data on the highways of Tehran during 2015-2016. Inthis research, it is attempted to identify and prioritize the parameters affectingthe severity of accidents in Tehran city using a combination model of neuralnetwork and genetic algorithm. For this purpose, in the hybrid model, theseverity of the accident is considered as the dependent variable and the fourgeneral categories of variables namely climate, road, vehicle and driver areconsidered as independent variables. Then, using artificial intelligence methodand data preprocessing, the optimal structure of the neural network model wasdetermined and finally, the result of the neural network model was consideredas the input of the genetic algorithm. The results not only determines andprioritizes the main parameters affecting the severity of accidents inTehran(including: 1-driver behavior, 2-how the vehicle is moving, 3-type ofvehicles and 4-highways safety status), but also Indicates that the combinationmodel of Neural Network and Genetic Algorithm has a good performance inidentifying the parameters affecting crash severity in Tehran, And couldprovide a new insight into designing a pattern to understand better and preventfuture accident-related accident injuries.