请解释ought to have gone along 为什么to 后面有have呢,

题目

请解释ought to have gone along 为什么to 后面有have呢,
A policeman approached Jimmy and told him he ought to have gone along a side-street as Jumbo was holding up the traffic.

答案

楼上的解释不对
ought to have done
虚拟语气,应该做某事而未做某事
这句话的意思是：警察告诉违章的Jimmy,因为交通管制,他应该走小巷.（事实是Jimmy没走小巷）