Done it towing a pup. It is just a little curvy, and the speed limit drops to 50 a couple of times. But after all, it is an interstate, so it is not bad at all. just don't get in a big hurry. Black Mountain is your steepest grade. However if you go up 26 to 40 you will miss it. And Saluda grade becomes the steepest. Not bad as BM though. Neither is anything to worry about, as they have slow lanes going up to use.