After reading the article about how cars are killing humans through air pollution and knowing that “pollution now kills three times as many people worldwide as Aids, tuberculosis, and malaria combined. ”and it is also “the world’s most significant threat to children’s health”. People should replan Transport in a way maximizing its social benefits while minimizing harm. For example，Japanese metro system. Most people take trains instead of driving their own car since the trains are always faster than cars and arrival on time. On the other hand，The electric mass transit technology in Japan is the most developed，so the electric car does not cause as much as the pollution the normal car does.