Hard infrastructure
Hard infrastructure, also known as tangible or built infrastructure, is the physical infrastructure of roads, bridges, tunnels, railways, ports, and harbors, among others, as opposed to the soft infrastructure or "intangible infrastructure of human capital in the form of education, research, health and social services and "institutional infrastructure" in the form of legal, economic and social systems. This article delineates both the capital goods, or fixed assets, and the control systems, software required to operate, manage and monitor the systems, as well as any accessory buildings, plants, or vehicles that are an essential part of the system. Also  included are fleets of vehicles operating according to schedules such as public transit buses and garbage collection, as well as basic energy or communications facilities that are not usually part of a physical network, such as oil refineries, radio, and television broadcasting facilities. Attributes. Hard infrastructure in general usually has the following attributes: Capital assets that provide services. These are physical assets that provide services. The people employed in the hard infrastructure sector generally maintain, monitor, and operate the assets, but do not offer services to the clients or users of the infrastructure. Interactions between workers and clients are generally  limited to administrative tasks concerning ordering, scheduling, or billing of services. Large networks. These are large networks constructed over generations and are not often replaced as a whole system. The network provides services to a geographically defined area, and has a long life because its service capacity is maintained by continual refurbishment or replacement of components as they wear out. Historicity and interdependence. The system or network tends to evolve over time as it is continuously modified, improved, enlarged, and as various components are rebuilt, decommissioned or adapted to other uses. The system components are interdependent and not usually capable  of subdivision or separate disposal, and consequently are not readily disposable within the commercial marketplace. The system interdependency may limit a component life to a lesser period than the expected life of the component itself. Natural monopoly. The systems tend to be natural monopolies, insofar that economies of scale means that multiple agencies providing a service are less efficient than would be the case if a single agency provided the service. This is because the assets have a high initial cost and a value that is difficult to determine. Once most of the system is built, the marginal cost of  servicing additional clients or users tends to be relatively inexpensive, and may be negligible if there is no need to increase the peak capacity or the geographical extent of the network. In public economics theory, infrastructure assets such as highways and railways tend to be public goods, in that they carry a high degree of non-excludability, where no household can be excluded from using it, and non-rivalry, where no household can reduce another from enjoying it. These properties lead to externality, free ridership, and spillover effects that distort perfect competition and market efficiency. Hence, government becomes the best  actor to supply the public goods. Transportation. In 1990, Grübler discussed the history and importance of transportation infrastructures like canals, railroads, highways, airways and pipelines. Energy. The OECD classifies coal mines, oil wells and natural gas wells as part of the mining sector, and power generation as part of the industrial sector of the economy, not part of infrastructure. Communications. OECD lists communications under its economic infrastructure Common Reporting Standard codes.