The paper, Good Urban Transit: A Conservative Model by Paul M. Weyrich and William S. Lind, evaluates different modes of transit, namely regular transit, commuter transit, and growth-creating transit. From this paper:
Because streetcar lines have repeatedly proven they can both generate and channel economic development, growth-creating transit will almost always be provided by streetcars… Growth-creating transit has no typical “shape.” The location of streetcar lines will follow the city’s desire for development or redevelopment. Wherever it has a decayed area it wants to bring back, or a low-density area it wants to convert to high-density, the streetcar will go… Wherever streetcars run, service frequency should be high throughout the day… Why is such frequent service necessary? Because the purpose of streetcar lines is to create growth. They do that by acting as “pedestrian facilitators.” Frequent service means people can get off the streetcar, spend some time as a pedestrian, then easily and quickly get on another car. That time as pedestrians is what generates new growth. It is pedestrians, not people in automobiles or on streetcars, who shop, have meals in restaurants, go to shows and do all the other things that give an urban area life. Streetcars work their developmental magic by making all those activities easy.