Trunk Line is about studies in infrastructure. So what is infrastructure?
[Fr. (1875 in Robert), f. INFRA- + STRUCTURE n.]
A collective term for the subordinate parts of an undertaking; substructure, foundation.
substructure: That part which supports something else.
foundation: The solid ground upon which another structure is erected.
(OED usage dates to 1927.)
(1) substructure, organization, structure, setup, arrangement, groundwork, frame, foundation, base
(2) public service, public transport, communications, power supply, water supply, broadcasting, telecommunications, networks, transportation