Between May 9 and June 3, 150 clusters of new coronavirus cases emerged in France, according to the country’s
national public health body. Defined as three cases or more of Covid-19 linked by contact, these clusters occurred largely in the sort of places you might predict they would....
...What was striking however, was the number of clusters associated with public transit:
There weren’t any. For almost a month, not a single Covid-19 cluster had emerged on France’s six metro systems, 26 tram and light rail networks or numerous urban bus routes....
... a combination of masking, limited exposure time and some exchange of air could make conditions safer than those in enclosed places where people are close together and unmasked for hours at a time.