The biggest source of energy is petroleum, including oil and natural gas. Together, they supply 65 percent of the energy we use. According to the U.S. Energy Information Administration, oil furnishes 40 percent of our energy, natural gas 25 percent, coal 22 percent, nuclear 8 percent, and renewables make up 4 percent.

Natural gas pipelines transport natural gas. Liquid petroleum (oil) pipelines transport liquid petroleum and some liquefied gases, including carbon dioxide. Liquid petroleum includes crude oil and refined products made from crude oil, such as gasoline, home heating oil, diesel fuel, aviation gasoline, jet fuels, and kerosene. Liquefied ethylene, propane, butane, and some petrochemical feedstocks are also transported through oil pipelines.

Crude oil is liquid petroleum that is found underground. Depending on where it is found and the conditions under which it was formed, crude oil can vary widely in density, viscosity, and sulfur content. Crude oil is processed by oil producing companies to make refined products that we can use, such as gasoline, home heating oil, diesel fuel, aviation gasoline, jet fuels, and kerosene.

A vast number of products that are used in our daily lives are made possible through the use of oil. Oil products fuel our transportation, whether it is by plane, train, car, truck, bus, or motorcycle. Oil is used to heat our homes and provide the energy that powers our factories. Chemicals made from oil are used to make a wide variety of products, ranging from clothing to cosmetics to pharmaceuticals. Modern plastics made from oil are used extensively in producing numerous products that are used daily in all facets of our lives.

Natural gas supplies 25 percent of all the energy Americans consume. It's our second largest source of energy. Only oil provides more energy than natural gas. Natural gas has many different uses. For example, power companies use it to generate electricity, industries use it for heat and as a source of power, and millions of households rely on natural gas for heating and cooking. Liquid propane gas and compressed natural gas, which are produced from natural gas, provide the convenience of natural gas to locations where pipeline distribution is not available.

The nation's pipelines are a transportation system. Pipelines enable the safe movement of extraordinary quantities of energy products to industry and consumers, literally fueling our economy and way of life. The arteries of the Nation's energy infrastructure, as well as the safest and least costly ways to transport energy products, our oil and gas pipelines provide the resources needed for national defense, heat and cool our homes, generate power for business and fuel an unparalleled transportation system.

The nation's more than two million miles of pipelines safely deliver trillions of cubic feet of natural gas and hundreds of billions of ton/miles of liquid petroleum products each year. They are essential: the volumes of energy products they move are well beyond the capacity of other forms of transportation. It would take a constant line of tanker trucks, about 750 per day, loading up and moving out every two minutes, 24 hours a day, seven days a week, to move the volume of even a modest pipeline. The railroad-equivalent of this single pipeline would be a train of 75 2,000-barrel tank rail cars everyday. These alternatives would require many times the people, clog the air with engine pollutants, be prohibitively expensive and -- with many more vehicles on roads and rails carrying hazardous materials -- unacceptably dangerous.

Pipeline systems are the safest means to move these products. The federal government rededicated itself to pipeline safety in 2006 when the PIPES Act was signed. It mandates new methods and makes commitments for new technologies to manage the integrity of the nation's pipelines and raise the bar on pipeline safety.

Pipeline systems consist of a few major components:

• Pipelines that collect products from sources, such as wells on land (gathering lines) or offshore, or from shipping, such as tankers for oil or liquefied natural gas (LNG). These systems move the product to storage, processing (such as treatment for gas or refining of petroleum).
• Transmission pipelines that transport large quantities of hazardous liquids or natural gas over longer distances; transmission lines deliver natural gas to distant power plants, large industrial customers and to municipalities for further distribution; petroleum transmission lines deliver crude oil to distant refineries or refined products to distant markets, such as airports or to depots where fuel oils and gasoline are loaded into trucks for local delivery.
• Distribution lines are a part of natural gas systems, and consist of main lines that move gas to industrial customers, down to the smaller service lines that connect to businesses and homes throughout a municipality.

Along these pipelines are pump stations for liquids and compressor stations for natural gas, storage and distribution facilities and automated control facilities to manage the product movement and maintain safety. Should a pipeline fail, a drop in pressure normally triggers systems that close valves to isolate the failed pipeline.

The federal authority for pipeline safety is PHMSA, the Pipeline and Hazardous Materials Safety Administration of the U.S. Department of Transportation. PHMSA's Office of Pipeline Safety is responsible for regulating the safety of design, construction, testing, operation, maintenance, and emergency response of U.S. oil and natural gas pipeline facilities.

In 2003, there were over 2.3 million miles of pipelines in the U.S. carrying natural gas, and hazardous liquids (chiefly petroleum and refined petroleum products, as well as chemicals and hydrogen). Here is a breakdown:

PHMSA safety jurisdiction over pipelines covers more than 3,000 gathering, transmission, and distribution operators as well as some 52,000 master meter and liquefied natural gas (LNG) operators who own and/or operate approximately 1.6 million miles of gas pipelines, in addition to over 200 operators and an estimated 155,000 miles of hazardous liquid pipelines.

Review an expansive discussion of pipelines or read more Pipeline FAQs.