匯智英語自學(xué)課堂突破口語中級篇突破口語D lesson53

The public transportation systems in most big cities in America are very good. New York, especially, has one of the largest and most useful subway and bus systems in the world. Public transportation helps to cut down on pollution and traffic. In big cities, with so many people, this is a very important problem. However, Americans do love their cars. The average family has two. So much more money goes into building roads, than new subway or train lines. In some cities, like Atlanta, this has meant a quick increase in pollution and traffic congestion as its population has grown.