Background: Traffic accidents are among major causes of death all over the world. In Iran, it has become a social problem, with lots of people involved in; and the youth include the most victims of traffic accidents. The main objective of this research is to review the experience of the youth (18-24 years old in Tehran, Iran) with traffic accidents, and to develop a model to specify the factors. Materials and Methods: This study is based on Grounded Theory, in which a sample group of 50 young people, 18-24 years old, in Tehran, Iran, were selected and interviewed, using stratified purposive and snowball sampling method. Data is mainly collected by interviewing the youth in 7 key topics. To analyze the data, Grounded Theory is used through production of themes, components and concepts. Results: There are 11 general components for traffic accidents according to the ideas of the youth which will come in 3 categories including: individual factors (emotions, sensorymotor skills, and physical-mental health); environmental factors (road and traffic problems, a companion, using cellphone, or front individual, including carless drivers or passersby); and underlying factors (gender, legal and cultural infrastructures). And finally, the core category of carelessness, which is the leading cause in traffic accidents. Conclusion: The findings indicate that a chain of various factors may cause traffic accidents with lots of devastating consequences. It is therefore necessary to modify driving culture, to internalize the attitude of caution, to use polyhedral strategies, and to apply them all correctly.