The circular economy aims to tackle climate change and other global challenges such as waste, pollution and biodiversity loss, by reducing resource consumption, keeping assets components and materials at their highest value and promoting regenerative and restorative design. This must be achieved while maintaining the safety and technical function of services, assets and components. Transport Infrastructure Ireland (TII) is responsible for delivery and operation of the national road, light rail and Metro networks in Ireland and has set about transformation to a circular economy approach to its assets components and materials. TII has created an organisation wide policy and strategy informed by an international “state of the art” review of circular economy in transport. Implementation workbooks and guidelines were created to support the transition of projects and programmes to a circular approach for road, light rail and greenway assets. Systems mapping was undertaken along with organisation wide and external collaboration. Applicable TII standards and specifications are being updated with some already complete for pavement and earthworks as priority. Projects undertaken in support of the transition included a performance-based pavement design tool, the Irish Analytical Pavement Design Tool (IAPDM) and a mass haul earthworks optimisation tool. Use of Environmental Product Declarations has been promoted through development of Product Category Rules for key material types. This enables evidence based environmental value driven material selection. This paper sets out actions taken by a major transportation agency in their transition to applying circular economy approaches to all projects and programmes funded by TII. The paper also outlines learning from the process which might beneficially be implemented by other transport agencies internationally.