Back in April, I had some less-than-fun times with altitude sickness at the Grand Canyon. I got the whole drill: headache, nausea, inability to sleep, shortness of breath, extreme exhaustion. Basically, I experienced all the non-dangerous systems.
Good thing; if I'm going to get sick, I'd much prefer that it not be dangerous.
Denver was not a problem. We spent all our time a meager mile or so above sea level. The drive over the Rockies was a different matter. It never even occurred to me to worry about a few hour's drive.
I had problems just before we hit the Eisenhower Tunnel. At 10,158 feet, it was just too high. I had an instant headache, nausea and even some difficulty catching my breath. I was so exhausted that I had to stop driving and let CKL take over.
Turns out, my bout of altitude sickness made me the lucky one. As the passenger, I got to spend all my time marveling at the beauty of the Rockies. CKL had to watch the road.