NS is the largest train operating company on the Dutch railway network. With a growing demand in train movements, the railway infrastructure is subject to changes. These infrastructural mutations are a collaboration between NS, as Train Operating Company, and ProRail, as infrastructure manager. Various complexities arise due to the close relationship between the railway infrastructure, the timetable of the train services, the deployment of rolling stock and crew scheduling. This thesis discusses the complexities in the process of infrastructure mutations from the viewpoint of NS. This is done by means of a process analysis and the assessment of a tool that is used within NS for the creation of rolling stock circulations. The process (of infrastructure mutations) can be seen as a system, in which the subsequent planning processes for the timetable, rolling stock and crew are regarded as subsystems. This system is analysed by means of a reconstruction of the normative situation (the as-is situation). This normative situation is then compared with a real-life situation. Next to the reconstruction of the process, bottlenecks in the normative process are identified. These bottlenecks can be subdivided in the following categories: problems with information management, unclear definition of the process and its roles, and a lack of top-level management for (larger) mutations. Subsequently, a similar analysis is done for a real-life situation. In this thesis, the DSSU project is used for this purpose. The DSSU project is a comprehensive renewal of the shunting yards at the central station of Utrecht, in the heart of the Dutch railway network. Looking at the planning process at NS, the following bottlenecks can be identified: Unclear definition of the process and the definition of its roles, time limitations, a lack of planning resources, a lack of top-level management and issues with the realisation of the train service after the completion of the construction works. For these bottlenecks, various improvements are suggested in this thesis, based on experience from within NS, as well as from literature. The key finding of the process improvement is that using a more integral approach in the process of infrastructure mutations, both in information housekeeping and collaboration between actors, can avoid bottlenecks and result in better solutions in terms of timetable products and rolling stock deployment. As a solution to the bottleneck of limited overview of the impact of mutations, an evaluation of rolling stock circulation tool ‘TAM’ is performed. To evaluate the use of TAM in practical situations, three cases were assessed. From the assessments it can be concluded that the tool indeed can give useful information on the effects of an infrastructure mutation on the rolling stock planning, but the results are highly dependent on patronage-prognoses and inputs from other parts of the planning process, like the (altered) timetable. Besides this, the tool is (in its current form) not able to make optimal solutions, due to pre-defined turn-around patterns that constrain the model. Since TAM is a made to generate circulations, the (microscopic) shunting planning is not part of the tool. Conclusively, TAM is a useful tool to obtain insights in the impact of infrastructure mutations, but it does not cover all effects and does not necessarily provide optimal alternative circulations.