You should check with the road authority because they might be fake.
One day I was driving down a road that I’d driven down many times when I spotted a new speed limit. It was posted in a weird location and the speed was odd.
I contacted the local main roads department and learnt that they didn’t know about these signs. The next day they were gone.
Agreed, having a minimum speed sign on a stroad is just begging for pedestrian deaths. It would be such an obvious liability that nobody in charge of transportation would allow it.
Every municipality has a minimum speed limit so you can’t just have someone driving 1km/h down the road creating a rolling blockade. Most are posted on the entrance into the municipality.
There are reasons for both sides to have and not have specific laws.
Where are these municipalities?
These are US signs and this isn’t a thing anywhere that I have traveled to across the US other than the 40 minimum on some interstates and highways.
Where I’m from it’s just 20 less than the max. Conditions apply but that’s because they reduce the max
I’m a traffic engineer and I’ve literally never heard of such a thing (except on freeways).
https://www.epermittest.com/road-signs/minimum-speed-limit
Supposedly minimum speed limit signs do exist in California? No issue with checking anyway, I was curious is all
Freeways/expressways around me are 45 mph minimum. They are normally mounted below the limit sign.
https://www.twincities.com/2015/05/20/more-than-700-miles-of-interstates-in-wisconsin-to-be-70-mph/
But I have seen small tack on signs that are the same in most regards.
https://commons.m.wikimedia.org/wiki/File:SPEED_LIMIT_75mph_MINIMUM_SPEED_50mph_NO_TOLERANCE.png