Every urban planner wants to avoid the “Oxford Street problem”. London’s famous 1.2 mile (1.9km) long shopping street is notoriously congested. Buses trundle along it at barely more than walking speed, spewing out the world’s highest concentrations of nitrogen dioxide.
Cities across the world are slowing down as they grow. Average traffic speeds in central London, according to TfL, fell from 9.2mph in the first quarter of 2010-11 to 7.4mph in the first quarter of 2017-18.
In central Manhattan, average travel speeds have fallen by a fifth since 2010 and in Bogotá, Colombia, drivers spend on average 272 hours sitting in traffic every year, according to analytics company Inrix.
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