It makes no sense that traveling makes you tired, all you do is sit in the car/airplane/train/whatever and wait, amirite?

I think the lack of interesting stimulation sucks the life out of me.

It's called jet lagg

It's exactly just that though. You are sitting there, doing nothing. Moving around is stimulating and causes you to not feel tired. Sitting there allows your mind to relax and you become sleepy.

When driving you constantly think mustnotcrashmuststayawakemustnotcrashmuststayawakemustnotcrashmuststayawakemustnot
crashmuststayawakemustnotcrashmuststayawakemustnotcrashmuststayawakeZITCHDOG!!must
notcrashmuststayawakemustnotcrashmuststayawakemustnotcrashmuststayawake...