Commuting is very precious time for me because I can keep certain amount of time for study.
Studying English is one option but I don't want to spend much time for it. English is just a tool so if I have a time for studying english, I want to spend time for another things.
Studying English is merely like a machinely training for me. It doesn't need intelligence. I don't want to waste my precious time for such a training.
(But english is good tool to get huge amount of information so I'm listening english materials at walking, transition period of station because I can't read books in such a situation )
By the way, first priority is reading books. I often read science articles using RSS feed via smartphone but book is special for me. Good books contain wonderful knowledge and wisdom so we can get such informations about $20-$30 per a book.
I also use MOOCS. If we have a certain subject to know about, MOOCS is very useful.
It's true from my experience.