This paper introduces an interdisciplinary connection between public sector and private service provision in the course of privatisation considerations. Based on the fulfilment of public sector duties, it defines boundaries for the development of infrastructure, for the development of federal roads, and answers the following questions using the project planning phase for federal road projects: When can privatisation take place? What is to be privatised? How must privatisation be implemented? The requirement for an optimal development trend for privatisation, whilst taking into consideration the question of "by whom and for whom the fulfilment of public sector duties takes place" is a crucial element of this research, as the strict separation of economic viability in the interests of the public hand and economic viability in the interests of private parties. On the basis of interdisciplinary research methodology, private parties are brought into alignment with public service provision in a strictly defined sequence of processes. This is achieved by means of the intermediate steps awarding size, theoretical standardisation of the service to be awarded, and its complexity evaluation, as well as an award procedure based on a systematic consideration of all public and private sector parties concerned. A model is created which is intended to serve the user, the taxpayer as part of the social capital in a manner which is shaped by common welfare, freedom from self-interest, objectivity and economic efficiency (§ 7 Abs. 1 BHO). This model answers the following research question: "How must public authorities proceed, in order to move a private party from egocentric thinking to a comprehensive, objectively balanced project planning performance, free of self-interest, whilst simultaneously optimising the economic viability of the public sector interest?" The knowledge gained from this research comprises an analysis of strengths and weaknesses with no pretence of providing precise proof. Both research methodology and the results gained within the pre-determined limits of federal road projects and infrastructure projects as well as fulfilment of public sector duties are taken into consideration with relation to how well they can be transfered to subjects beyond the scope of the research subject itself. As a result of the interdisciplinary perspective of this paper, many varied and highly interesting related possibilities for further development are uncovered.