 If I-94 and I-29 can accommodate 75 mph traffic, I see no reason why US-2, US-83 can't handle at least 83 from Bismarck to Minot. If it's four lanes, I don't see why it can't handle 75 mph traffic. You have to slow down before you get to the towns anyway. It's not like you need to slow down traffic in the middle of nowhere.