If you are driving yourself to or from work, it’s silly to suggest you should wear a mask in the car. But cars can present a risk of coronavirus transmission with one or more passengers, like when using a ride sharing service like Uber. After all, cars are completely sealed spaces where airborne particles can be trapped, and social distancing is impossible. Brown University researchers used simulation models to study the ventilation in a small car. They found that about 10 percent of aerosols exhaled by one of the car’s occupants could reach the other person. Opening all the windows eliminated almost all of the aerosols, but that’s not a great option in the winter. For a common ride sharing seating arrangement, opening the windows opposite the driver and passenger – the front right window and back left window – essentially creates a barrier between the driver and the passenger. The researchers also found that opening the windows halfway provides the same benefit as opening them all the way.