This been attempted in quite a few places: https://www.theguardian.com/cities/2018/oct/15/i-leave-the-c...

> 'in 2017 there were 99 fare-free public transport networks around the world: 57 in Europe, 27 in North America, 11 in South America, 3 in China and one in Australia. Many are smaller than Dunkirk and offer free transit limited to certain times, routes and people.'