It's a good point, and one of my bugbears of getting on a crowded rush hour Sydney bus or train. Geez the amount of sneezing. That said Sydney generally has journeys that are way to expensive by car (you need to park) so public transport is the only option and conversely journeys that are epic by public transport but quite quick by car. There rarely feels like there is a "hmm what do I fancy today" kind of choice.