The Partnership for Downtown St. Louis is working with the East-West Gateway Council of Governments and Bi-State Development Agency to improve mobility in St. Louis, Missouri. A key element of this program is a potential new streetcar system serving two corridors in the central city. The Partnership retained RSG as part of a team to determine the feasibility of this project, and RSG was responsible for estimating of the order-of-magnitude ridership potential of two new streetcar lines. Together, these lines are designed to improve corridor circulation and provide a last mile connection between the regional Metrolink LRT system and destinations in each corridor. The forecasting methodology was based on the Federal Transit Administration Aggregate Rail Ridership Forecasting (ARRF) model, which was adjusted to match observed streetcar ridership in other cities in the United States. This approach enabled RSG to generate realistic estimates of streetcar ridership in a new market within two weeks of commencing the project.