The main contribution of this study is to bring the multiple-representative household CGE approach to a model of the entire South Asian region, as opposed to the single-country models examined earlier in the paper, and to apply this model to changes in transportation infrastructure. The model that we have developed is a multi-country CGE with 16 production sectors and 47 regional households. In principle, the model should have applications for numerous policy questions concerning South Asia, especially in relation to international trade and economic integration. The scenarios that we considered in this paper reflect the potential implications of proposed investments in land transport infrastructure in the SASEC region. These investments should result in reductions in the land transport component of international transport margins, which vary bilaterally by commodity. We found that all SASEC economies benefited from reductions in aggregate welfare, with the largest gains to India in absolute terms but the largest relative gains to Nepal, followed by Bangladesh, and Sri Lanka, when the margin reduction is prorated to intra-South Asian trade rather than just SASEC. Hence, in terms of overall impact, the largest gains are to the smallest economies in the region. We used the discounted present value of the EV stream to provide a (lower bound) estimate of the total ‘one-off’ benefit of the margin reductions, which is suitable for comparison with project cost estimates should these become available.