地铁：subway， 公交车：bus， 轻轨：light rail， 火车：train
对环境有好处 ：benefits the environment
成本高： be far more costly than xxx
排放尾气 ：pollute the air and emit greenhouse gas
占用空间： take up a lot of valuable space
本可以用来： could have been used for other purpose, building a library, garden, park or playground for the kids
制造噪音： create lots of noise
如果政府鼓励大家使用公交的话，这会降低“交通”水平, 会减少交通拥堵 。
If government encourages the use of public transportation, it will decrease the level of traffic and reduce the chance to get stuck on the road.
You do not have to worry about finding a place to park or filling up the gas like you would if you drove your own vehicle.
Some people prefer to 有自己的车, other prefer to mainly use 公共交通. Which do you agree with? Explain why.