For much of the route the altitude shifts are buffered by the grade restrictions of the U.S. interstate system. In other words, nothing too extreme. If your car is powerful enough and you're in a hurry, you may not realize how high you're climbing.
This got me thinking about the gradual ascent, the steady accretion of duties, the daily growth of a child that's invisible to you until she sees distant relatives who say, "How much you've grown!"
So much happens to us slowly, invisibly, without our permission. It's probably better that way.