Carbon emissions emanating from infrastructure construction are substantial, and public infrastructure clients have begun to include carbon reduction goals in their procurement requirements. This is a new and complex field where practices vary and are still developing. Based on project documentation and interviews we map and analyze the design and implementation of carbon reduction requirements in projects by leading infrastructure clients in Australia, the Netherlands, Sweden, the US and the UK. Procurement requirements were influenced by concerns for tender competition, transaction costs and innovation, and further adapted to project delivery models, market maturity and client capabilities. Increasing awareness of practical and contextual constraints often led to modified strategies. This paper identifies factors that should be considered when designing carbon policies and requirements. This knowledge is important for clients and governments in order to develop more effective strategies for learning between contexts. Policies and future research should address client capabilities to drive long-term innovation.

The infrastructure construction sector is a significant source of carbon emissions, and more stringent procurement requirements are central to meeting reduction targets in this demand-led and project-based industry. This paper aims to analyze the implementation of international policies for reducing carbon emissions in infrastructure construction, focusing on the interaction between policy ambitions and procurement practices. Based on case studies of large projects and their contexts in five countries worldwide: Australia, the Netherlands, Sweden, the UK, and the US, a cross-country comparison is performed of how policies and practices for carbon reduction develop across multiple implementation levels. Three levels are included in the analysis: policy, industry, and project level. We identify the projects as either drivers of policy goals, frontrunners in industry-level development processes, or translators of national policy. These roles, and the associated pathways for carbon emission reduction, are context-specific and depend on the policy ambitions at the national or regional level, the maturity of the supplier market, and, often, on the strategies of individual champions at the project level. Long-term learning processes, both within and between the various levels, are essential for advancing carbon reduction.