European cities are increasingly looking toward free transport in a bid to combat air pollution.

Anne Hidalgo, the Paris mayor, is the latest local leader hoping to make public transport free across the city, emulating the success of a handful of small towns across France which let residents board buses and trams without paying a cent.

The German government is also considering rolling out free transport across the entire country - with the same aim as in France of reducing air pollution - if a pilot scheme in five big cities this year works out.

Niort in western France has been running free buses since last September for its 125,000 inhabitants.

The scheme has been an enormous success, boosting passenger numbers by 130 per cent on some routes, slightly reducing the number of cars on the roads, and costing the town little more than when people had to buy tickets, said mayor Jérôme Baloge.