GMC 2004 Sierra - Manual (Page 341)

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 mirrors and your
instruments frequently.
• 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.
Hill and Mountain Roads
Driving on steep hills or mountains is different from
driving in flat or rolling terrain.
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