According to an article on the Australian website
Drive new medical research shows that traveling in an old clunker rather than a late-model vehicle could protect you from catching the flu. Apparently the poorer seals in older cars let a lot of infectious airborne particles out of the vehicle, unlike newer, better-sealed cars that hold air in. Dr Scott Bell, Director of Thoracic Medicine at the Prince Charles Hospital in Brisbane is quoted, in part:
Put simply, if you are travelling for around 90 minutes in a relatively modern car with air circulation on low, you are almost certain to catch influenza from another infected passenger.
