Montana for quite a few years had an official speed limit of 55 outside cities.
If stopped driving a “safe speed” above that limit, the LEO collected an on-site “fine” of $5 and send you on your way. No points or record.
We called it the speeding fee.
When I lived in Montana the speed limit was 55 at night because of open ranges. During the daytime it was, "reasonable and prudent" which often meant 90.
Driving from Reno to Great Falls the speed limit is currently 75. Has anyone calculated what an extra 4 hours at 55 would be in terms of gallons-per-hour?