The function of infrastructure systems is to support flows and activities of people, goods, materials, and information in the built environment. Built areas are created by the construction industry and its partners in real estate, banking, and development. Transportation and communications systems provide for flows of people, goods, and information. Water and energy sustain the economic and human sides of the built environment, and the waste management system handles its residuals. The next few paragraphs provide further detail on how the sectors and systems of infrastructure support the built environment.
Built environment. The built environment provides infrastructure in the form of buildings and drives demand for other network services. Residential, commercial, and other buildings require services from infrastructure systems and provide public services themselves. The networks that provide transportation, communications, water, energy, and waste management are integral parts of the built environment, but their fixed assets are accounted for within separate sectors.
Transportation. The transportation industry is not very integrated. Highways and streets are mostly operated by state and local governments and toll authorities, but transportation service and parking providers usually are separate. Transit bus and rail systems are operated mostly by local authorities. Intercity rail for passengers and freight is mostly in the private sector. Air transportation involves mostly government airports and private airline companies and general aviation. Other modes include ports, harbors, and waterways; pipeline freight transport; and intermodal transportation.
Communication. Service providers in this rapidly changing sector are mostly private businesses. The sector includes wired and wireless communications
Energy Sector. Electric power is provided by public and private utilities, including the federal government. Natural gas is conveyed by transmission companies and distributed by local utilities and companies. The utilities in the energy sector are mostly integrated in the sense that they own their own supply chains and distribution outlets, and the industry is integrated in the sense that it comprises mostly players devoted to their core businesses. Liquefied natural gas and propane are also significant energy supply sources for the built environment. Transportation relies heavily on petroleum.
Water Systems. Water supply is provided by public and private utilities, whereas wastewater service is provided mostly by government utilities. Water and wastewater utilities usually own their own process chains, and the industry is integrated in that it comprises mostly players devoted to the water business. The water industry also includes stormwater, irrigation and drainage, flood control, and hydropower.
Waste Management. The waste management business is not very integrated. Waste collection companies and agencies do not always own transfer and disposal facilities. Solid and hazardous wastes involve both public and private sector organizations, and nuclear wastes involve national political issues.