To save money, he often goes to the city by hitchhiking on the roadside.

hitchhiking 是动词 hitchhike 的现在分词形式。hitchhike 由 hitch（搭便车）和 hike（远足、徒步旅行）组成，字面意思是"搭车旅行"，指在路上竖起大拇指请求免费搭乘过路车辆的行为。