The environmental value of transport infrastructure in the UK: An EXIOBASE analysis

Five life cycle assessment (LCA) methods to calculate a project's environmental value are described: (a) process-based, (b) hybrid, (c) pseudo, (d) simplified, and (e) parametric. This paper discusses in detail and compares the two methods with the least inherent uncertainty: process-based LCA (a bottom-up methodology involving mapping and characterising all processes associated with all life cycle phases of a project) and a hybrid LCA (the EXIOBASE analysis, which incorporates top-down economic input-output analysis and is a wider sector-by-sector approach). The 'bottom-up' nature of process-based LCA, which quantifies the environmental impacts for each process in all life cycle phases of a project, is particularly challenging when applied to the evaluation of infrastructure as a whole. Conversely, combining the environmental impact information provided in EXIOBASE tables with the corresponding input-output tables allows decision makers to more straightforwardly choose to invest in infrastructure that supports positive environmental outcomes. Employing LCA and a bespoke model using Pearson's correlation coefficient to capture environmental interdependencies between the transport sector and the other four 'economic infrastructures' showed the transport and energy sectors to be most closely linked. Both integrated planning and innovative technologies are needed to radically reduce adverse environmental impacts and enhance sustainability across transport, waste, water, and communication sectors.