You start to see things that aren't there. Especially your night vision.
You'll se something ahead that you'd swear is a group of people and it's only bushes or shadows.
The first time I saw a joshua tree, it was off the side of the rig road (dirt access road to a drillsite) in the edge of the headlights.
I had driven for close to 28 hours on top of a 12 hour day, with a 1 hour nap, and a lot of coffee. My only stops had been to get rid of coffee, get more, and to get fuel and a handful of snacks. (A real meal would have put me to sleep).
By then, everything I saw was pretty much in black and white, and I was not sure they were even there--I just stayed on the road.
"I brake for hallucinations" is more than just a cute bumper sticker, too. Illumination aspect changes on things near the roadside give the impression of 'something' jumping out in front of the vehicle.
I am older and wiser now, and won't push the envelope anywhere near so hard unless it is a matter of life or death.
[it's only bushes or shadows.]
Moonlight, leaves, shadows cast on rocks - and a soft breeze to bring things to life.
Yep.