Yup! The bases are extensive enough for it. No reason for their slow vehicles to add to any road congestion.
Dude you need to get down south a bit more....
Like around Atterbury lol, they run convoy training on the normal roads ALL the time. Yes they use the Camp as well, but that's for specific things. The training outside or off post is for more realistic drivers training so they know how to deal with traffic. and OMG on some of those convoys they have GUNS!!!!!!!!!
It's pretty real as well since people like you are going to be all pissy with the SLOW Vehicles