Across the world,the news of COVID-19 was followed by 'lockdowns' that lim-ited societal activity and mobility to a greater or lesser degree.In China,how-ever,the situation was unique because the travel lockdown occurred in the middle of the year's most hectic travel season oc-curring around Chinese Lunar New Year(chunyun).
It is worth spending a moment to appreciate how massive chunyun is as an event.Chunyun,or 'Spring Trans-port'in Chinese,is literally the world's largest annual human migration[1],in 2016 estimated to result in almost 3 billion journeys[2].It starts around 15 days before New Year's Day and lasts for about 40 days.