GMC 1993 Safari Owner's Manual page 190

Your Driving and the Road
On two-lane highways or undivided multilane highways that do not have
controlled access, you'll want to watch for some situations not usually found
on freeways. Examples are: stop signs and signals, shopping centers with
direct access to the highway, no passing zones and school zones, vehicles
turning left and right off the road, pedestrians, cyclists, parked vehicles, and
even animals.
Highway Hypnosis
Is there actually such a condition as "highway hypnosis?" Or is it just plain
falling asleep at the wheel? Call it highway hypnosis, lack of awareness, or
whatever.
There is something about an easy stretch of road with the same scenery,
along with the hum of the tires on the road, the drone of the engine, and the
rush of the wind against the vehicle that can make you sleepy. Don't let it
happen to you! If it does, your vehicle can leave the road in less than a
second, and you could crash and be injured.
What can you do about highway hypnosis? First, be aware that it can
happen.
Then here are some tips:
Make sure your vehicle is well ventilated, with a comfortably cool interior.
Keep your eyes moving. Scan the road ahead and to the sides. Check
your
rearview mirrors frequently and your instruments from time to time.
This can help you avoid a fixed stare.
Wear good sunglasses in bright light. Glare can cause drowsiness. But
don't wear sunglasses at night. They will drastically reduce your overall
vision at the very time you need all the seeing power you have.
If you get sleepy, pull off the road into a rest, service, or parking area
and take a nap, get some exercise, or both. For safety, treat drowsiness
on the highway as an emergency.
As in any driving situation, keep pace with traffic and allow adequate
following distances.
4-34