This paper introduces a new general equilibrium approach to evaluate economic impact of public transportation capital stock in the US. By treating public transportation capital as separated factor accounts, the model enables us to assess the economic impact of public transportation stock for four modes: road, air, transit, and water transportation. The study provides a direct and easy way for policymaker and transportation planning practitioner to compare social and economic benefits of different modes of public transportation. Findings reveal that road stock has the highest contribution to the growth of GDP and levels of social welfare; public transit and other ground passenger transportation have the least impact on the US economy among the four modes.