Zupan’s measurements are formulaic, and in every case the formula is based on two things—land use and density, the pattern of building that pools people to live or shop in proximity to each other and hence to transportation services. The more we congregate, the more we fill our buses. The more buses we fill, the more we get. It is a chain. The more buses we get, the better transit works and the fewer cars we need. When we house fewer cars, density can rise—and the more we fill our buses and can insert rail.
