It's a bit more ethical because you don't have to worry about all the pollution

这样做很符合社会公德，因为你不用担心会产生污染，

地铁的好处 - SpeakingMax英语口语达人

It has to do with the way things should be because of issues of pollution and sin.

它跟规矩有关,它跟亵渎和罪孽有关。

耶鲁公开课 - 心理学导论课程节选

Plus, it removes unnecessary cars from the road, which of course will reduce pollution.

另外，它减少了路面上多余的车辆，当然这样可以减轻污染。

地铁的好处 - SpeakingMax英语口语达人

But again, the more people cycle, the less pollution we have.

但是再次地，人们骑自行车越多，污染就会越少。

我使用自行车 - SpeakingMax英语口语达人