Folks drive at what they feel is a safe speed for themselves. The posted speed limit doesn’t really seem to impact much, when the road is wide, the lanes are big, and there aren’t many turns or traffic calming elements, people will go fast because others are going fast.
That’s been my lived experience, and generally is supported by research that its road design more than anything that dictates speed.
Should is the key word here. You pay a lawyer to find out, which probably isn’t worth it.