A national highway network is the arterial tier of a road hierarchy: a state-administered set of trunk routes whose function is to carry long-distance and heavy through traffic between state capitals, ports, industrial centers, and other high-generation nodes, as distinct from local roads serving access. The governing design principle is separation of through movement from local access — capacity is matched to traffic volume and vehicle character through lane widening and grade separation, while access control (bypasses, service roads, encroachment removal, restriction of roadside distraction) preserves free flow, because uncontrolled frontage growth, or ribbon development, mixes local with through traffic and degrades speed and safety. Within transport infrastructure and highway engineering, the topic connects network planning and functional classification to pavement research, mechanized construction, bridge and level-crossing structures, cost-recovery financing such as tolling, and regulatory instruments such as national permits that make an interstate network operationally continuous.
A national highway network is the arterial tier of a road hierarchy: a state-administered set of trunk routes whose function is to carry long-distance and heavy through traffic between state capitals…