Infrastructure projects are today major contributors to global warming. However, various strategies for reduction of greenhouse gas emission are available, as described in sustainability assessment schemes and performed in infrastructure projects. Beyond the choice of methodology, greenhouse gas reduction represents an important challenge, namely to engage involved actors. The establishment of a common sustainability policy, reflected in procurement requirements could be a solution. However, often in subject of complications such as misunderstandings or increased cost. Impres, a research project aiming to streamline the process of greenhouse gas reduction in the infrastructure sector, conducts case studies around the world in which useful methods and examples are assimilated. In cooperation with Impres, the present report includes the case study of California High-Speed Rail (CHSR). The aim of this report is to compare strategies for greenhouse gas reduction of sustainability assessment schemes for infrastructure projects, and evaluate the feasibility as procurement requirements. Furthermore, to identify corresponding processes of greenhouse gas reduction in the case study of CHSR, as well as revealing important factors towards realization. The course of work involves a study of the schemes Envision, BREEAM Infrastructure, CEEQUAL, IS Rating System as well as the standard PAS 2080. Regarding the case study, the sustainability policy, procurement requirements and project reports are the main used sources. Moreover, qualitative interviews with involved actors have been performed in California. Finally, to create a comparative matrix for greenhouse gas reduction processes, standards ISO and PAS 2080 have been reviewed. The results show that greenhouse gas criteria of the studied schemes not are mandatory to perform in anyone but PAS 2080. Which means that further requisites might be needed in order for the schemes to be useful as procurement requirements. Furthermore, the outlining of processes reveals a weakness in the setting of a greenhouse gas reference point, and while every scheme includes a greenhouse gas quantity assessment, there is a difference in the priority of reduction. Regarding CHSR, an exclaimed policy goal is to perform climate neutral construction. While procurement requirements are limited to quantification of emitted greenhouse gases and the use of effective construction machinery, which is insufficient to meet the goal. Nevertheless, the Authority in charge is performing CO2 compensating measures, such as planting trees. Finally, a variety of driving forces, success factors and challenges for realizing greenhouse gas reduction have been identified. For example, personal motivation and legislation as driving forces. Whereas, sustainability as a core mission, experience and communication are seen as success factors, and resistance to transfer sustainability goals to procurement is an exclaimed challenge. As a conclusion, sustainability assessment schemes do have certain processes for greenhouse gas reduction in common. However, they present criteria with different degrees of obligation, affecting feasibility as procurement requirements. In CHSR, similar processes are found, where further reduction of greenhouse gases can be achieved, especially by an optimized choice of construction materials. In the end, personal motivation seems to be an important factor for introducing and realizing greenhouse gas reduction goals in infrastructure projects. / Impres