People here in America are used to more personal space because it is not over populated. But in other countries with crowed houses and overpopulation you would not even be able to walk in your own space.
Because cars use oil and oil is a fossil fuel. And when you drive the engine heats up which make the smoke come out of the exhaust pipe and it gets into the air and pollutes which is dangerous for any creature that flies.
The answer is obviously 64.