Estonia has become the first country in the world to offer free public transport to all its residents, a move the Baltic state says will not only reduce air pollution and traffic congestion, but also foster commercial activity in its city centers, according to the World Economic Forum.

Expand chart Metro fares collected by Axios from news reports, municipal websites, and PriceofTravel; Chart: Harry Stevens/Axios

Why it matters: The metro can be a touchy subject (just ask D.C. residents), and for good reason. Public transportation is a huge factor in making major cities affordable and convenient to live and work in. Combine rapid urbanization with crumbling infrastructure, and you’ve got a tricky and expensive problem to solve.

The big picture: Around the world, national and municipal governments are experimenting with ways to cope with growing transportation demands in the face of economic and environmental pressures — some more successfully than others.