Custer to Badlands

all those roads are 2 lane, but good pavement. check locals to be sure. I have been on them all on my Harley during sturgis bike week and if you stay on those state hiways, you are good to go.

You certainly can go that way, but if your intent is to drive the loop road thru the Badlands towards the east, you'll already be past it when you get to Interior. Instead, when you get to 44, you'll only be 3 miles south of I-90 East. Continue east on I-90 to the west entrance to the Badlands, thru the entire loop road and back to I-90, 50 miles later. Its worth the drive. Stark but beautiful scenery in its own way.
I've always wondered what the first settlers headed west thought when they entered the Badlands.

44 is mostly straight, flat 2 lane highway with very little traffic. The road through the Badlands is also an easy drive with a lot of turnouts. You shouldn't have any problems.