Then the selection problem of transportation route is studied.

接着研究了路线的选择问题.

Thin river ice is a significant issue because winter travel is mainly achieved by using the frozen rivers as a transportation route via snow machines or sled dogs.

河面上的冰层十分重要，当地人冬季出行主要就是通过雪车或狗拉雪橇走冰面上的交通路线。