The completion of the missing links of the ring road sections of the highway network system in the Greater Tokyo Area will bring about significant and wide-ranging changes to the economic activities of the area. To properly estimate the spatial economic impacts of the highway project, this study builds a spatial computable general equilibrium, TMU spatial economic (TMUSE) model, which features the aspects of iceberg transport cost, economy of agglomeration, and municipality-level regional classification. The theoretical framework is based on the Dixit-Stiglitz general equilibrium model of monopolistic competition. The model classifies the area at the municipality level into 376 subregions with three industrial sectors. Starting from the rougher classified interregional data, we develop a procedure to calibrate the benchmark equilibrium for the detailed regional classification. The empirical study compares the benchmark economic state under the current road network situation with the new equilibrium state under full network completion. The analysis identifies the regions that would gain more from the highway project and estimates the changes in the sectoral outputs for each region.