During rush hours, you often see cars lined up with just one person inside, each car polluting the environment.

rush 的意思是"匆忙、急促"，在这里指"交通高峰期"。 hours 是 hour 的复数形式，意思是"小时、时间段"。 rush hours 指一天中交通最繁忙的时段，即"高峰时段"。