These fare-dodging collectives' egalitarian dream happens to align with some hopes of U.S. policy makers. There’s an intuitive, consequentialist argument that making public transit free would get drivers off the road and reduce greenhouse-gas emissions. In the U.S., where government subsidies cover between 57 and 89 percent of operating costs for buses and 29 to 89 percent of those for rail, many public-transit systems are quite affordable, costing in most cases less than $2, on average. If it might make transit more accessible to the masses and in the process reduce traffic and greenhouse-gas emissions, why not go all the way and make transportation free?

The earliest urban experiment in free public transit took place in Rome in the early 1970s. The city, plagued by unbearable traffic congestion, tried making its public buses free. At first, many passengers were confused: “There must be a trick,” a 62-year-old Roman carpenter told The New York Times as he boarded one bus. Then riders grew irritable. One “woman commuter” predicted that “swarms of kids and mixed-up people will ride around all day just because it doesn’t cost anything.” Romans couldn't be bothered to ditch their cars—the buses were only half-full during the mid-day rush hour, “when hundreds of thousands battle their way home for a plate of spaghetti.” Six months after the failed, costly experiment, a cash-strapped Rome reinstated its fare system.

Three similar experiments in the U.S.—in Denver, Colorado, and Trenton, New Jersey, in the late 70s, and in Austin, Texas, around 1990—also proved unfruitful and shaped the way American policy makers viewed the question of free public transit. All three were attempts to coax commuters out of their cars and onto subway platforms and buses. While they succeeded in increasing ridership, the new riders they brought in were people who were already walking or biking to work. For that reason, they were seen as failures.

A 2002 report released by the National Center for Transportation Research indicated that the lack of fares attracted hordes of young people, who brought with them a culture of vandalism, graffiti, and bad behavior—which all necessitated costly maintenance. The lure of "free," the report implied, attracted the "wrong" crowd—the "right" crowd, of course, being wealthier people with cars, who aren't very sensitive to price changes. The NCTR report concluded that eliminating fares “might be successful for small transit systems in fairly homogenous communities, it is nearly certain that fare-free implementation would not be appropriate for larger transit systems.”

Another report followed up 10 years later, revisiting the idea of a fare-free world. The report reviewed the roughly 40 American cities and towns with free transit systems. Most of the three dozen communities had been greatly successful in increasing ridership—the number of riders shot up 20 to 60 percent “in a matter of months.” But these successes were only to be found in communities with transit needs different from those of the biggest cities; almost all of the areas studied were either small cities with few riders, resort communities with populations that “swell inordinately during tourist seasons,” and college towns. In other words, slashing fares to zero is something that likely wouldn’t work in big cities.