Abstract Carbon emissions emanating from infrastructure construction projects are substantial and stem primarily from production of construction materials and use of energy for construction transport and site activities. In recent years, public infrastructure clients world-wide have begun to include carbon reduction goals in their procurement requirements. This is however a new and complex field where practices vary and are still developing. In this paper, we compare models for carbon reduction requirements in infrastructure construction projects based on case studies of large projects in Australia, USA, the Netherlands, Sweden and UK. We found that open, functional carbon reduction requirements were considered innovative but entailed costs for calculating baselines and risks for speculation. Also, high time pressure in projects limits contractors’ opportunities to explore reduction opportunities. Thus, specific, prescriptive requirements may play an important role in client-led, long-term innovation processes. Organizational competence and resources on the buyer side are essential, and policies for carbon reduction should aim to increase client capacity. Further, procurement practices are developed in mutual interaction between clients and suppliers over longer periods of time, which limits possibilities to transfer procurement policies and requirements between contexts.