On interstates I have a method that works great and is safe. I determine prevailing speed and then increase maybe 5 mph until I’m well clear of other traffic then I maintain a speed where I am not being passed much nor am I passing much. This avoids pack driving which is the most dangerous.
The safest speed is actually above the average. That curve is skewed significant;y to the right.
But be careful about reading too much into this.
It does not mean that one become safer by driving a little faster (if one is a slow driver). That slow driver, may be drunk, elderly, distracted, or an addle-brained-Freeper.
Note the log scale at left. Those who drive 30MPH below the average speed have a collision rate that is 1000x the rate for average-speed drivers!