the train on which she was traveling was late 这里可以用by which吗

问题描述:

the train on which she was traveling was late 这里可以用by which吗

介词 on 是 travelling on the train
用 by which的话
把 定冠词 the 去掉
但是 这句句子主干是 the train was late(此处the 不可省略)
所以 用by which是不合适的