The location technology company and satnav maker TomTom reports a traffic index for hundreds of cities based in part on data from satnav users. The index suggests how much longer a journey would take to complete than in ideal conditions. In Paris, for instance, in normal conditions, it was usual for the congestion index to exceed 100%, meaning that a journey would take more than twice as long as it would on empty roads. For each of these cities we compared the average 2019 congestion index for peak hours of every day to the 2020 index, to show where lockdowns bit hardest, where they began earliest, and where they are starting, fitfully, to be released.

The Chinese city of Wuhan, where the virus was first observed, is only slowly emerging from an intense, months-long lockdown. Shanghai also experienced restrictions as authorities sought to contain a local outbreak in China's biggest city. It is striking, though, how quickly the city of 23m people returned to normal levels of circulation.

Lombardy, the northern Italian region with Milan at its centre, was the first place in Europe to go into lockdown. But initially only a few small areas were affected by restrictions. As the seriousness of the situation became apparent, the lockdown was extended to the whole region and then to the rest of Italy.

By the middle of March, a tale of two cities was in play between the French and British capitals. Paris locked down earlier than London, and the restrictions there have been more rigorously enforced: citizens are obliged to print off a slip detailing the reason whenever they leave their homes.

Sweden has resisted a lockdown of the sort common across most of Europe. But its government has advised citizens to practise social distancing. While the contrast with neighbouring Denmark is stark, it is clear that even in Stockholm, traffic levels reduced sharply in the last weeks of March.

Taiwan so far seems to have controlled the spread of Covid-19 without lockdowns, and traffic levels in its capital are not far from normal. Sapporo, on the northern Japanese island of Hokkaido, was locked down until 12 April, after which traffic started to increase slowly, until a new lockdown was imposed when cases again began to increase. Many countries are now watching anxiously for such second waves, even as they aim to ease restrictions.