I think an international car-free day is not an effective way to reduce air pollution. Generally it is a good idea, but I do not think it would really work. Even if every person agreed to not use their cars for one day, it is just drop in the ocean, because, there is still 364 other days that are full of traffic fumes. Though, it is appealing as it would make people think more about ecology and the environment we live in. I believe the most effective way is to change all the traditional cars to electric, under the circumstance that there will be no other environmental issues caused by them.