Sitting in a car with other people increases the risk of contracting airborne infectious diseases, such as COVID-19. So is it possible to safely take a taxi or offer a ride to a friend? To find out, physicist Varghese Mathai, from the University of Massachusetts Amherst, USA, and his colleagues performed computer simulations of the airflow and movement of particles and aerosols in a car carrying two people. They concluded that the best way to reduce the risk is to keep all windows open. When that is not possible—on a rainy day, for example—the most efficient measure is to open the windows farthest from the occupants: the right front and the left rear, if the passenger is sitting on the right in the rear seat (Science Advances, January 1). This creates an airflow barrier between the driver and the passenger.
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