From the Minneapolis Streetcar Feasibility Study:
Streetcars generally attract at least 15-50 percent more riders than bus routes in the same area. In many cases, the difference in ridership is much higher. Based on recent North American examples of streetcar implementation, there is a clear ridership boost that can be attributed directly to the implementation of streetcar service replacing bus service in a given corridor. In Toronto, on routes where streetcar service replaced a nearly identical bus service, ridership increased 15-25 percent. A particularly dramatic example can be found in Tacoma, where streetcar service is running on a future light rail transit (LRT) alignment. Transit ridership in the streetcar corridor increased by over 500 percent compared to the bus route that ran previously. The route charges no fares and offers free parking, conditions that were present on the previous bus route as well. San Francisco experienced a threefold increase over bus ridership on its historic F-line corridor since beginning streetcar service in 1995.