Read the following passage and answer the item that follows. Your answer to this item should be based on the passage only.

Our cities cannot possibly sustain reliable public transit unless financing mechanisms are put in place. Building and running a metro or bus network requires heavy investment: acquiring vehicles, laying tracks or dedicated lanes, and maintaining stations so that services stay safe and frequent enough for daily use. If our cities were rich enough to meet the entire cost, transit could be provided free. They are not.

What is the most logical and crucial message conveyed by the passage?