What have you been able to learn during your commute (and how)?

I commute by bicycle, and my brain doesn't absorb things well through spoken word (so audio books aren't very useful to me). So I don't learn much new during my commute.

However, that commute time is of immense value to me. Much like shower time, I often find myself reviewing various technical problems and coming up with "aha" insights about them. Perhaps not the sort of learning that you're talking about, but I think it counts as learning nonetheless.

I have gone to YouTube lecture series for a few years for my 1hr/day commute (by car). Some notable topics that work well are history, law, psychology. Generally it depends entirely on the lecturer. Many old school lecturers don't take advantage of visual aid. Unfortunately the more technical the lecture the more it relies on visual aid and the less I am able to learn purely auditorially.

https://m.youtube.com/user/YaleCourses/playlists

I've also found success with Audible and podcasts.

I take naps if I get a seat, otherwise, close my eyes and listen to music. I don't really learn well or retain much when I'm tired.