Sadiq Khan revealed plans for the entire 1.2-mile stretch of Oxford Street between Tottenham Court Road and Bond Street tube station to be pedestrianised by 2020.
The central London street welcomes more than 200 million visitors annually to its large department stores, and is used by about 270 buses every day.
The process will be rolled out in two stages to reduce disruption to the street, starting with the eastern section leading from Oxford Circus.
Cars, with the exception of taxis, are already banned from most of Oxford Street between 7am and 7pm every day apart from on Sundays.
In 2014, researchers from King's College London found Oxford Street was “the most polluted place on Earth”, even exceeding pollution levels in Beijing.
Valerie Shawcross, London’s deputy mayor for transport, told the London Assembly that bus movements in the area would be substantially reduced, rather than simply rerouting them to surrounding roads.
The number of shoppers coming to Oxford Street is expected to increase substantially with the opening of Crossrail, which will have two stations opening at Tottenham Court Road and Bond Street in December 2018.
The move comes as part of Mr Khan’s mayoral manifesto pledge to tackle London’s air pollution crisis over the next few years, having said last week a charge will be introduced for the highest polluting vehicles.
In May, Mr Khan revealed he has recently started suffering from asthma and attributed his condition to the quantity of toxic substances in London’s air.
In early July, Paris launched its latest drive to reduce air pollution by introducing a ban against vehicles built before 1997.
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