The streets of Paris will be transformed this Sunday, with thousands of people on foot and on bikes expected to take advantage of a ban on cars that covers almost half of the city centre.

Mayor Anne Hidalgo promoted the first Journée Sans Voiture a year ago, in response to a rise in air pollution that briefly made the French capital the most polluted city in the world. In March, she backed a regular Paris Respire (Paris Breathes) day on the first Sunday of the month, with traffic cleared from the eight lanes of the Champs Elysées and a number of surrounding streets, and is pushing through plans to pedestrianise a busy expressway along the Seine. This weekend, the French capital is closing 400 miles of streets to cars in an “XXL” version of the event to mark World Car-Free Day.

Airparif, an independent air pollution monitor, said that on Paris’s first car-free day – which covered around a third of the city – nitrogen dioxide levels dropped by up to 40% in some parts. Bruitparif, which measures noise, said sound levels fell by half in the centre.



A YouGov poll after Paris’s first car-free day in September last year found a majority of Londoners – including regular drivers – would support a similar monthly car ban in central London. The survey found that 63% of those asked supported a car-free day with motor vehicles banned from the central third of the city, with only 24% opposed. A smaller majority (58%) were in favour of making the event monthly.



Since his election in May, London’s new mayor Sadiq Khan has been consulting on plans to tackle air pollution – including an ultra low emissions zone in central London and a toxicity surcharge for more polluting vehicles. He has also pledged to pedestrianise Oxford Street, starting with car-free days and weekends along the busy shopping area, although firm plans have yet to be agreed. Greenwich, in south-east London, also looks set to get occasional car-free days.



Khan’s predecessor, Boris Johnson, promised to explore holding regular car-free days in London after being “blown away” by the success of Jakarta’s weekly event during a trip to the Indonesian capital in November 2014 – but nothing came of the idea. Eight miles of central streets are closed for a few hours one Sunday a year for the annual Prudential FreeCycle, with the event so popular that frequent bottlenecks make it impossible to ride parts of the course.



A spokesperson for Khan said: “The mayor is looking into a range of dynamic proposals on improving public spaces, including traffic-free days and plans for the pedestrianisation of Oxford Street. He is overseeing hard-hitting new measures to tackle London’s polluted air, and is supportive of events like car-free days that both lower toxic car fumes and encourage pedestrians to get out and enjoy their streets more.”



In 2016, though, car-free day coverage in those British cities taking part seems to be limited to single streets: Lambeth council is closing Cornwall Road on Saturday – for a bike market, food stalls and roller disco; elsewhere in the UK, Cardiff is closing one street – Park Place – today.



While some dismiss car-free days as a gimmick, others say they can act as a catalyst, allowing residents to see how their city could look without private traffic. Many other cities around the world are taking the opportunity to ban cars from large parts of the centre. Last weekend saw Brussels hold its 15th annual car-free day, while Copenhagen held its first car-free day since the 1970s.



Mexico City closes 35 miles of city centre streets to cars every Sunday, while Bogotá – a pioneer of regular traffic bans with its weekly Sunday Ciclovía event running since 1974 – is holding one of three annual Días Sin Carro today. Private cars and motorbikes are prohibited in the centre from 5am to 7.30pm, the largest working-day car ban in the world.



New York closed a swathe of the centre to cars to mark Earth Day in April, and has continued its popular Summer Street programme, where Park Avenue is pedestrianised on three Saturdays in August. Manhattan held a Shared Streets event this summer, which restricted cars to 5mph over 60 blocks of Financial District. Other American cities holding car-free events this weekend include Philadelphia and Detroit, while even car-oriented Los Angeles now regularly runs the biggest car-free events in the country.



Other cities are taking longer-term measures to cut motor traffic. Oslo has revealed plans to ban all private vehicles from the centre by 2019, Hamburg is developing a green network for people on foot and bikes that will span 40% of the metropolis, and Madrid intends to pedestrianise the urban core and expel cars by 2020.



So is London being left behind? The London Cycling Campaign said it would welcome a car-free day in London, but that it would be no match for long-term investment in infrastructure.

“The LCC would love to see car free days in London,” a spokesperson said. “We know many people want to cycle in our city, but currently feel scared because of the danger posed by heavy motor traffic. Car-free days would open up our streets so that more Londoners could enjoy the spaces where they live, work and play; and travel around the city by bike without fear.

“However, car-free days wouldn’t reduce the actual dangers that cyclists and pedestrians face day to day. London needs long-term investment in cycling and high-quality cycling infrastructure to make our streets safe for everyday journeys by bike and on foot, for people of all ages and abilities.”

Thursday 22 September is World Car-Free Day. Is your city taking part and closing streets to cars? If so, tweet your pictures and thoughts to @guardiancities