Carry a railroad timetable in case the plane is ground.

带一份火车时刻表，以免飞机误点。

youdao

So, if you're looking back, say, from the end of the nineteenth century, it's not easy to see, but you can see these-- don't ever think that history runs on railroad tracks, and all you need is the timetable to show when modernization shows up.

所以,当你回顾历史,从十九世纪的末尾开始,虽然不太容易,但还是可以看出...,别以为历史是在固定轨道上行进的,别以为你只用拿时刻表,就知道新时代什么时候来临

耶鲁公开课 - 欧洲文明课程节选