Material Flow Analysis of the British Road Network: Stock, Flows and Implications for Circular and Low Emission Construction

Abstract

Road networks represent one of the largest material stocks within national infrastructure systems and play a critical role in shaping future material demand, recycling potential, and greenhouse gas mitigation strategies. This study presents a material flow analysis (MFA) of Great Britain's road network, quantifying the material stocks and flows associated with construction and maintenance activities over the period 2000 – 2020. A hybrid top down and bottom-up MFA approach was applied to asphalt, granular materials, concrete, other paving materials and individual composite materials. The results show that non-metallic aggregates dominate both stock and flows. Granular materials represent the largest stock, while asphalt constitutes the most dynamic flow due to frequent maintenance cycles of upper road layers. About 92% of material inputs are associated with maintenance rather than new construction, highlighting the maturity of the British road network. Despite significant recycling activity, only a limited fraction of reclaimed asphalt is reused in asphalt production, indicating substantial unused recycling potential. Increasing recycling rates would also further reduce greenhouse gas emissions and material demand. However, a continuous material demand remains due to continuous network growth and loss of surface materials due to road usage. Finally, roads could act as a carbon sink when a systemic approach is combined with balancing material consumption, service life and performance.