How does the author describe the highway in Chapter 12?

From the text:

HIGHWAY 66 IS THE main migrant road. 66—the long concrete path across the country, waving gently up and down on the map, from the Mississippi to Bakersfield—over the red lands and the gray lands, twisting up into the mountains, crossing the Divide and down into the bright and terrible desert, and across the desert to the mountains again, and into the rich California valleys.