Rubenerd

As defined by page 45 of the New South Wales Road Users' Handbook, the early warning signs of fatigue are:

• Yawning.
• Poor concentration.
• Tired or sore eyes.
• Restlessness.
• Drowsiness.
• Slow reactions.
• Boredom.
• Feeling irritable.
• Making fewer and larger steering corrections.
• Missing road signs.
• Having difficulty staying in the lane.

I'd add heat. A lot of people I talk to claim to feel cold when fatigued; for some reason I feel as though I'm burning up. I also feel overconfident in my joke telling abilities.

And something I didn't know:

During peak holiday travel periods, such as Christmas, Easter and holiday long weekends, almost 100 Community Driver Reviver sites operate throughout NSW. These are places to take a break during a long journey and have a free cup of tea or coffee and a snack. Local volunteers are on hand to offer advice about road conditions.

That's really cool.