In jargon, the “operating speed is a critical factor in determining an appropriate speed limit for a speed zone.” In English, speed limits should not be so low that they make everybody a criminal. This has been a recognized standard for 70 years. Using this standard, one can objectively say that this speed limit is good and this speed limit is bad. You will find a disagreement of 5 MPH here and there. What you don’t get is one person honestly applying the rule saying speed limit 25 and another saying speed limit 45.
The standard is the so-called “85th percentile rule.” If fewer than 85 percent of drivers are obeying the speed limit, the speed limit is probably too low. It doesn’t have to be exactly the 85th percentile. The basic principle is people going with the flow of traffic should not get speeding tickets — not even if they have dark skin and out of state plates. Not even if there is zero-tolerance camera enforcement.