I know here in Brazil there’s a minimum speed limit on highways of 50% the max, but there are no signs, and it doesn’t apply in heavy traffic.
In Denmark we have a single piece of highway were we have a “crawl lane”. It’s slightly uphill and outside the lane you must go at least 80km/h. I know it is more common in Southern Europe.
Here in Germany, the Autobahn has a minimum speed cars need to be able to go (60 kph) although it’s not a minimum speed you necessarily need to drive.
However, we do have a dedicated minimum speed sign, but it’s very rare and usually only used in very specific places. The only one I know is a long and windy bridge on the side of a small mountain where, depending on your lane, you need to go at least 60, 80 or 90, I think.
