Restrictions that keep highly polluting cars out of certain areas -city centers, “school streets”, even individual roads-are a response to the absence of a larger effort to properly enforce existing regulations and require auto companies to bring their vehicles into compliance. (2020英二 Text3)
主干：Restrictions are a response to the absence
定语从句：that keep highly polluting cars out of certain areas，修饰Restrictions
同位语：city centers, “school streets”, even individual roads，解释说明certain areas
介词短语作定语：of a larger effort to properly…into compliance，修饰absence，其中and并列enforce existing…与require auto companies to…
参考译文：
限制高污染汽车进入某些区域——市中心、“学校街道”，甚至是私人道路——是对缺乏更大努力来正确执行现有法规和要求汽车公司将其车辆纳入法规的回应。
