Like any highway system, the federal airways have their main trunk line.

同任何公路系统一样，联邦航空线路也有其主航线。

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The highway is open to traffic the mileage and wills have the significant increment, the grade has the exaltation, will set up at a high speed the highway is the main National Freeway trunk line net .

公路通车里程将有大幅度的增加，等级有所提高，将建成以高速公路为主的国道干线网。

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Then divides the highway network into four levels: main trunk line, sub-trunk, feeder and connecting line, and also positions functions of the four levels.

进而按照通达程度将公路网划分为四个等级：主干线、次主干线、支线和连接线，并分别对四个层级进行了功能定位；

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