A main or trunk line (in transport or communications): a primary route such as a main railway line, roadway, or trunk communication line.
通勤には地下鉄の幹線を使うと速い。
Using the subway's main line is faster for commuting.
この幹線道路は朝夕の渋滞がひどい。
This trunk road is heavily congested in the morning and evening.
データは幹線回線を通じて各地の支店に配信される。
Data is distributed to branches around the country via the trunk line circuits.