A Closer Look

To illustrate dependencies among critical systems, let’s take a more in-depth look at some of the most universally important infrastructure sectors – Communications, Energy, Transportation, and Water. While all 16 sectors are considered critical, these four sectors are fundamental to the operation of practically every other critical infrastructure sector, which is particularly evident in systems’ increasing connectivity to and reliance on IT communications and electric power to operate. Please note that while this tool focuses its examples on these four fundamental sectors, all 16 critical infrastructure sectors have dependencies amongst themselves that can impact each other's operation.

Navigate through the four highlighted infrastructure sectors by either clicking on the corresponding icon or by using the next and previous buttons. Each closer look includes information about the sector's systems, components, services provided, and upstream and downstream dependencies.


Communication infrastructure consists of both physical and cyber components that deliver voice, video, and data services. Communication infrastructure is comprised of the following interrelated systems:
  • Broadcasting
  • Cable
  • Satellite
  • Wireless
  • Wireline

Communications systems are critical to virtually every societal function a community provides, both big and small. Whether it’s calling Grandma, using the internet to do homework, or dispatching fire and EMS response, communications systems connect us and allow us to instantly transmit information. Beyond that, communication systems are needed to monitor, control, and manage nearly every aspect of infrastructure operations — without them, everything from providing clean water to managing the flow of electricity becomes much more difficult.

Communication networks are geographically widespread, creating a complex web that enables people and systems to contact one another, access information instantly, and communicate remotely. Communications systems are generally provided by the private sector and often have multiple operators.


Virtually all modern infrastructure systems are at least in part reliant on communications networks. The Communications sector provides critical services to:

  • Energy systems to aid in monitoring and controlling the delivery of electricity and the management and monitoring and control of fuel and gas pipelines and terminals.
  • Transportation systems to monitor and control the flow of surface, sea, and air traffic.
  • Water and wastewater systems, which use communications systems to monitor water quality, manage treatment processes, and control water distribution.
  • Emergency Services for directing resources, coordinating response, operating public alert and warning systems, receiving emergency 911 calls, coordinating law enforcement activities, and managing dispatch and communications between utility crews.
  • The Information Technology sector enabling delivery and distribution of applications and services.
  • Financial Services for the transmission of transactions and operations of financial markets.

The Communications sector relies on services from the following critical infrastructure sectors:

  • Energy to provide electricity to power cellular towers, central offices, and other critical communications facilities.
  • Information Technology for critical control systems and services, physical architecture, and Internet infrastructure.
  • Transportation systems for delivery of diesel fuel needed to power backup generators.


Energy infrastructure consists of three main systems — electricity, oil, and natural gas.
  • Electric systems generally consist of power generation, transmission, and distribution systems connected to large regional power grids.
  • Oil and natural gas systems generally include production (mining and extraction), refining, storage, and distribution systems (pipelines and fuel terminals, railways, trucking, and marine vessels).

The Energy sector powers every other critical infrastructure system and is critical to the delivery of essential services such as education, healthcare, and media, and is one of the underlying services that enables local economy. Fundamentally, energy systems keep the lights on, buildings warm, food cool, vehicles moving, and information flowing.

Energy infrastructure is geographically dispersed, often crossing multiple jurisdictional boundaries. Energy assets and systems can be owned by private, Federal, State, or local entities that serve the public. Systems may also be owned, operated, and used by specific energy consumers.


Virtually all other critical infrastructure systems depend on electricity to power their operations. Petroleum fuels and natural gas are also critical to a number of sectors, especially transportation, and are commonly used to power generators during power outages.

Energy systems themselves rely on services from transportation, information technology, communications, finance, water, and government infrastructure.


Transportation infrastructure consists of three main systems — air systems, surface systems, and maritime systems.
  • Air Systems consist of airports, heliports, landing strips, air traffic control systems, aircraft (manned and unmanned), and support services.
  • Surface Systems consist of roads, bridges, pipeline systems, rail, mass transit, and postal/shipping services.
  • Maritime Systems consist of waterways, ports, and intermodal landside connections.

Transportation systems support basic societal functions by facilitating the movement of people and everyday necessities. Without them, our schools would be empty, ambulances couldn’t respond to emergencies, and store shelves would be bare.

Transportation infrastructure is the collection of systems needed to move people and goods and are generally categorized as air, maritime, or surface systems.


The Transportation sector depends on:

  • Communications to control and monitor traffic
  • Information technology to manage and route deliveries and manage supply chains
  • Energy to deliver fuel and power facilities such as warehouses, distribution centers, and depots

Transportation infrastructure plays the central role in supply chain operations, thus impacting most other critical infrastructure systems, as well as businesses and individuals. Examples of critical services provided by transportation infrastructure include:

  • Personal mobility
  • Movement of raw materials and components to factories and processing facilities, such as chemical deliveries to treatment plants
  • Delivery of products to consumers, and
  • Shipment of agriculture and food products

Transportation system hubs, such as ports, significantly impact critical industry making them an important nexus of infrastructure services and local and regional economies.

Water & Wastewater

Drinking water components include:
  • a water source
  • conveyance
  • pump stations
  • treatment plants
  • operational controls
  • storage tanks
  • monitoring
  • distribution pipelines
  • business systems
  • operators
Wastewater components include:
  • collection lines
  • lift stations
  • treatment plants
  • outflow and solid waste disposal
  • operational controls
  • monitoring
  • business systems
  • operators

Water infrastructure consists of both drinking water and wastewater systems, which are essential to the fulfillment of basic societal functions. Drinking water is required for sustaining life and protecting public health. Collection and treatment of wastewater is vital for preventing disease and protecting the environment.

Water and wastewater systems provide critical services in the form of drinking water, fire suppression, and sanitary services to virtually all residential, commercial, governmental, and industrial facilities. Without water systems, faucets would run dry, toilets could not flush, schools would have to close, public facilities and commercial buildings could not operate, and the local economy would suffer.

Drinking water and wastewater systems can vary in size and be publicly or privately owned. Both systems contain physical, cyber, and human assets necessary for operations and monitoring.


Water infrastructure relies on services from other critical infrastructure sectors, including: energy, communications, transportation, chemical, information technology, dams, and critical manufacturing.



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