That's a really interesting question. My unscientific hunch is that there were two different populations of drivers on MT roads at the time. Lets call them the

That's a really interesting question. My unscientific hunch is that there were two different populations of drivers on MT roads at the time. Lets call them the daredevils and the 65-ers. I'd bet that among the 65-ers, it probably did map pretty well--or at least approximately as well as it did in states that retained a 65mph speed limit. You might have seen a few people creep up maybe instead of setting your cruise to 72 mph, in hopes of skirting a ticket, you set it to 75 because... round number? The daredevils are pretty much by definition going to be exceeding the speed limit, but they could arguably be described as a different group, i.e. one that didn't internalize the 65 mph. A common narrative amongst Montanans of the time was that out-of-state types (most likely Californians, horror!) were coming to MT to treat our roads like a raceway. I'm sure that probably did happen to some extent, though who knows if it was actually a common occurrence.