Well we also used to have no speed limit. Back in the Moderately Prudent days it was more common to get passed by a semi like you were standing still while going 100+ in a blizzard through a canyon. That was until nightfall, then the speed limit dropped to 55 on highways and 65 on the freeway. It was insane.

But it did result in a two speed system. Most of the highways are 75 during the day and 65 at night. Which to me just seems smarter.

Then again it has been over a decade since I was in Montana.