Fatigue is a matter of opinion. The bad thing, is that the officer can think you are fatigued since you did not sleep well last night. It does not mean that you were unsafe. I have been fatigued running many shifts as a medic. I have to be able to think and save a life which is more stressful and harder than trucking. Fatigue is present on long shifts. Like I said, it is a matter of opinion.
Been there RM...but in the medic unit...many things are instinctual in your care and treatment of the patient...driving long unrested hours down a boring interstate (Kansas I-70 west half) can get to a driver when fatigue is already present.
I do the long lonely drives as well. I still say that fatigue is a matter of opinion. When an officer can ticket for it and not really know the facts of the driver, it will lead to many problems. As far as medical, instinct may be there, but not truly. One must pay attention.