Ed Braddy of New Geography provides some clear explanations that without cars mass transit goes broke!
The quote below provides a quick summary, but the full article is very informative.
Yet in pursuing this transit-friendly future political leaders rarely confront this inescapable reality: public transportation is fiscally unsustainable and utterly dependent on the very car-drivers transit boosters so often excoriate. For example, a major source of funding for transit comes from taxes paid by motorists, which include principally fuel taxes but also sales taxes, registration fees and transportation grants. The amount of tax diversion varies from place to place, but whether the metro region is small or large the subsidies are significant.
Read it here: Who is Dependent on Cars? Mass Transit!
The passage below is a reality comparison between roads and transit--what is fiscally sustainable and what is not:
Many policy makers fail to focus on developing a fiscally sustainable plan for public transit. They miss the fundamental problem that anything heavily subsidized –particularly in a period of budget cuts– is unsustainable. Roads are subsidized at about a half-penny per passenger mile; transit subsidies are 100 times higher.