Though we have talked about air pollution for many years, there are still a lot of people around the world that don't care about it. This reminds me of a great Chinese saying that goes "only when a person bumps into a wall, can he then go back". It means that someone doesn’t realize that they are making some mistakes, even though others try to prevent them but failed.They keep doing wrong things until they get punishments from their mistakes. It’s the same with air pollution. People drive cars every day and never consider that their vehicle exhaust causes air pollution. If you tell them the truth, they even take some deep breaths to show that they are healthy. It's really hard to change someone's mind. They just care about themselves. They can't see the bad results caused by air pollution. In that case, if you ask them to join a car-free day activity, they might think that you are silly. It won't appeal to them, but if the law tells them to reduce driving to protect the environment, they would carefully think about the relationship between vehicles and air pollution, so as to uphold the law.