Less cars means less pollution.
减少交通流量就会减少空气污染。
A I think the best way to reduce traffic and pollution is more public transport.
A 我认为最便捷的方式来减轻交通流量和污染是开发更多的公共交通工具。
B More buses and subways mean less cars.
B 更多公共汽车和地铁轨道就等于更少量的私家汽车。
A And less cars means less pollution and less traffic jams.
A 少量的汽车就等于减少污染和交通堵塞的状况。
B And more people cycling! Lots of good healthy exercise.
B 更多骑自行车的人！对身体健康很有益。
请记住，当你比较两样事物时，如: more / 更多 和 less / 更少
如：More buses and trains means less cars / 更多的公共交通设施等于更少的汽车；
And less cars means less traffic jams / 更少的阿汽车就等于更少的阿堵塞状况。 

练习：
More cars means more traffic.
Less traffic means less pollution.
More cycling is better for health.

更多汽车导致更多堵塞。
减少交通流量就会减少空气污染。
更多骑自行车就会更健康。