This study has been made on behalf of the Swedish Transport Administration to study the work of the department National Projects. The Swedish construction industry has for many years been characterized by low productivity. By being the largest purchaser of contracts in the industry the Swedish Transport Administration has a unique opportunity to influence the productivity. In order to improve in productivity The Swedish Transport Administration is adopting a new role in which they will order more turnkey projects. In our study, we will focus on how one department within the Swedish Transport Administration, National Projects, can perform successful turnkey projects. To clarify how the department National Projects can perform successful projects, this study identifies critical factors for projects and their links to different phases of the project. Existing theory regarding projects presents a large number of critical factors but there is a lack of connection between the factors and specific project phases. Linking factors to phases facilitates focus on and control of the different phases, as it highlights the factors that are important in each phase for project success. The method of the study is qualitative, five project managers were interviewed, in two sets of interviews, on various projects. Also information has been collected from different project documents. The result of the study shows a number of critical factors, both specific for National Projects and also more general factors that can be used in other projects of a similar nature. All factors are linked to the phases identified in the analysis. The result also contains a definition of project success in the department National Projects. This study is a contribution in regards to theoretical knowledge to existing theory regarding projects and practical knowledge for National Projects to use for improvements of their turnkey projects. Knowledge which we believe is useful for National Projects and their future work with turnkey projects.