经过多年采伐、南方林区的伐区已大部份进入边远的山帽地带、每公里林区公路所吸引的木材数量越来越少,林区公路的利用率越来越低。在这种情况下,即使我们采用规程中最低等级的公路进行延伸,在经济上也不见得合算。因此,南方的林道工程师就考虑修建一种比规程最低等级公路的标准还低的公路,其特点是路基更窄,一般为3.0m,不设错车道; After many years of logging, most of the cutting areas in the southern forest areas have entered the remote mountain-cap areas, and the number of trees attracted by the forest roads per kilometer is getting less and less. The utilization rate of the roads in the forests is getting lower and lower. In this case, even if we use the lowest grade of the road to extend the procedure, it is not economically justified. As a result, forest engineers in the South have considered building a road that is lower than the standard minimum grade highway, which is characterized by a narrower subgrade, typically 3.0 m, with no lanes,