The idea of making public transport free is gaining ground. By the end of 2021, 36 towns and cities in France had adopted it. Its supporters defend its benefits in terms of equality and modal shift, while its detractors criticise the cost and question the benefits. But what do the results of the experiment tell us? What are the problems that emerge, and what are the solutions? Arnaud Passalacqua, member of the French Observatory of free transport, and Philippe Duron, president of TDIE, debate on the use of free transport as a response to contemporary mobility challenges.