停止乘坐小车的英文表达是 "stop riding in a car"。
"Stop" 是动词，意思是 "停止"。
"Riding" 是动词，意思是 "乘坐"。
"In" 是介词，意思是 "在……里面"。
"A" 是冠词，意思是 "一个"。
"Car" 是名词，意思是 "小车"。
下面是一些英文例句和中文翻译：
"I need to stop riding in the car and start taking the bus to work." (我需要停止乘坐小车，开始乘坐公交车去上班。)
"It's time for the kids to stop riding in the car and learn how to walk or ride their bikes." (现在是孩子们停止乘坐小车，学习走路或骑自行车的时候了。)
"I made the decision to stop riding in cars and start using pubpc transportation to reduce my carbon footprint." (我决定停止乘坐小车，开始使用公共交通工具以减少我的碳足迹。)