CITY dwellers and planners should build on the dramatic changes swept in by COVID-19 to create a more sustainable and low-carbon future, urban experts told a virtual meeting of global leaders on Monday. Rigid school and office hours have given way to a more flexible system of working during the pandemic that puts less pressure on transport systems and energy grids, heard a "net-zero" cities panel organised by the World Economic Forum. "If you can actually reschedule cities thanks to the newfound flexibility following the pandemic there could be ... a big impact," said Carlo Ratti, director of the SENSEable…