Those Colorado Springs signs are about a mile from the house. I have seen them many times and wondered why.
I have theorized that it was a metric conversion. However, that is not the case.
So, my only other theory is that it is done to make the signs attract more attention. Being an odd # would catch your eye quicker.
I don't not think any system (speedometers, radar guns) used to monitor speed reads in decimals.
So, there you have it, see them all the time and have no clue.
On a side note, there is a round-about in the same area as those signs. If you want a good laugh, sit and watch Americans try to negotiate a round-about.
Clearly we are not used to them. I find it a bit unnerving to ride though.