the tours travel from the initial boreal forests through tundra to the toklat river or kantishna. several portions of the road run alongside sheer cliffs that drop hundreds of feet at the edges. there are no guardrails. as a result of the danger involved, and because most of the gravel road is only one lane wide, drivers must be trained in procedures for navigating the sharp mountain curves, and yielding the right-of-way to opposing buses and park vehicles.