The four of us carpool to work by taking turns driving, which saves money and helps the environment.

carpool 是由 car（汽车）和 pool（池、汇集）组成的复合词，字面意思是"汇集汽车"，指多人共乘一辆车上下班或出行，通过轮流驾驶来分摊费用和减少碳排放的出行方式。