## 5 Concluding Discussion
### Contributions, Limitations, and Future Research
However, the study showed that some frontrunners develop \"no-dig\", \"no build\" practices, breaking away from the business-as-usual scenario, which seems promising for more radical carbon emission reductions in the future. For the translators, the focus lies at the project level and largely on the calculation of carbon emission reductions. Such focus could potentially overlook what is big and what is small in terms of carbon emission reductions. However, some of these projects are embedded in an innovative structure, developed in collaboration with the procuring organization, which may ensure that carbon reductions are kept at a steady rate and in-line with national and global ambitions. Drivers are pushing the carbon emission context, as there is a discrepancy between national and global goals. However, it is important to note that none of the three types of projects are driving the international agenda. To reach further carbon emission reductions, it is clear that considerable cultural, managerial, and operational changes are required [25]. The next step in carbon emission reduction policy and the magnitude of action needed will depend on the actual projects' multilayered context. The construction industry is project-based, and an important part of sustainable development and carbon emission reduction can be overlooked when not considering the whole life cycle of the facilities and including, for example, the maintenance phase in the project, or at least already have requirements taking this into account in procurement, see e.g., [61; 62; 63]. This study has some identified limitations. The investigated projects and countries were chosen because they were deemed leaders in their implementation of requirements for carbon emission reductions and can, therefore, not be seen as average infrastructure projects. However, they are good representatives of flagship projects that act as drivers for different types of actions, and, as such, they provide a good overview of both success factors and challenges. The study focused on the construction phase of the infrastructure lifecycle, and a broader scope could, therefore, be of value in future research. Further studies developing the different roles taken in SPP implementation, and focusing more on the interactions between the different levels in each case, would also bring important contributions to the SPP field in a broader sense. The following are available online at [[https://www.mdpi.com/article/10](https://www.mdpi.com/article/10)]([https://www.mdpi.com/article/10](https://www.mdpi.com/article/10)) 3390/su132011182/s1. Conceptualization, S.L., J.A.O., A.K. ; methodology, S.L., J.A.O., A.K. ; validation, S.L., J.A.O., A.K., S.U. ; formal analysis, S.L., J.A.O. ; investigation, S.L., J.A.O., A.K., S.U. ; data curation, S.L., J.A.O. writing--original draft preparation, S.L., J.A.O. ; writing--review and editing, S.L., J.A.O., A.K. ; project administration, A.K. and S.U. ; funding acquisition, A.K. and S.U. All authors have read and agreed to the published version of the manuscript. This research was funded by Formas, grant number 254-2013-1837 and the Construction Climate Challenge, hosted by Volvo Construction Equipment. Mistra Carbon Exit grant nr 2016/12.