With an aging, dwindling population, and polluted air, something needed to change in Dunkirk, France. So when Patrice Vergriete became mayor of the post-industrial city by the sea in 2014, he promised to make public transportation totally free.

Vergriete foresaw multiple benefits: Poor citizens who were already riding buses would save cash. Seniors could have an easier time making social connections. Families with cars who had never thought to ride transit to parks and stadiums would be prompted to consider the bus.

Speaking at CityLab Paris 2017, Vergriete described some citizens’ initial reaction to his proposal as a kind of “psychological shock.” “Inhabitants say, ‘How can you do that?’” he said. “’You must pay the salary of the bus driver, for the gas, for the bus.’ To them, it seems magical.” But in Dunkirk, as in many cities, rider fares amount to a small proportion of transit’s total cost. Eliminating fares is about shifting tax dollars and political priorities, Vergriete said.

The city started by eliminating fares on weekends in 2015, and saw ridership boom. When the city deploys daily free service in fall 2018, Vergriete thinks the scheme will continue to spark new life into Dunkirk’s downtown, and clean the air in the meantime. “We all know today that we have to do something for the environment,” he said of his fellow mayors gathered at the conference. “Free public transportation also adds a social dimension, because it links people together. That’s something mayors are very interested in developing.”