Assessing agglomeration impacts of large-scale transport infrastructure

Large-scale transport infrastructure can influence national patterns of population and employment, and induce agglomeration effects and long-term economic development. However, conventional appraisal methods often do not capture these indirect impacts. This study investigates how transport investments may affect the spatial distribution of population and employment and the resulting agglomeration effects and productivity changes, using East West Rail in England as a case study. We develop an extended land use–transport interaction (LUTI) model with industry-level disaggregation. It integrates a recursive gravity framework with a multimodal transport network and iteratively updates residential and employment distributions in response to accessibility changes. Results reveal that the rail line stimulates significant growth within the region, particularly along its route, but attracts limited inflows from more distant areas. Employment relocation (particularly in retail and service sectors) responds more sensitively to accessibility gains than residential patterns. When we apply our model to the national level (England and Wales), we capture the net benefits of agglomeration and disagglomeration. We find significant productivity gains in the corridor, with an estimated uplift of about 0.7%, and a modest but positive impact at the national scale around 0.02%. The results suggest that part of the corridor-level gain reflects redistribution through displacement from elsewhere rather than wholly additional national output. The analysis can thus contribute to the understanding of granular spatial patterns related to agglomeration and disagglomeration that arise from transport investments.