US 212 is a fine highway, it's the historic short route from Belle Fourche to Hardin and points west in Montana. Road is in excellent shape and traffic is nothing to worry about, and as hornet28 posted just above, fuel is available in Broadus, at least during normal working hours. Look for antelope and obey the speed limit when you're crossing tribal lands (generally on the western end of this route). Enjoy your trip!