by the way=顺便说下 它还有“在途中”的意思？

by the way
incidentally (used to introduce a minor topic not connected with what was being spoken about previously)
顺便说说，顺便提起
oh, by the way, while you were away I had a message.
哦，顺便提一句，你不在的时候我收到了一条消息。
during the course of a journey
在路上，在途中
you will have a fine view of Moray Firth by the way.
在途中你将欣赏到马里湾的美丽景色。

-新牛津英汉双解大词典

by the way是顺便的意思，by the way of...是通过...途径

by the way [简明英汉词典]
adv.在途中, 顺便

没有吧
on the way 是在途中的意思