As you know, driving and studying don't go together, unless you find an audio course suited to your needs. Since the GMAT isn't exactly a motivational or a language course, you would not be able to utilize an audio course that well. That is exactly the reason why there are no popular audio courses on the GMAT. (although courses are offered..google for some names).
I used to commute via public transport when I first started my prep, in order to utilize my time well. Using flashcards (many GMAT prep companies provide them) helped a lot.
But, if you're still set on listening to audio courses, plenty of effective video content is available online and offline that you can download on your device(s) and listen.
P.S. Knewton offers an audio course (I have not used it), "Thursdays with Ron" vids are available free (have used, highly recommend).