Dwight D. Eisenhower was responsible for jump starting the federal interstate highway system. Often referred to as the National Interstate and Defense Highways Act of 1956. This of course was lobbied by several United States automobile Manufacturers. Today it is very clear that they're lobbying has paid off.

The interstate highway system is widely used to carry freight, to serve as evacuation routes and for public transportation such as buses. However, the other main purpose of the interstate highway system was for United States Defense. Military vehicles could move around the country quickly and efficiently using the interstate highway system. Contrary to popular belief, the interstate highway system was never designed to be used as airport runways.

The interstate highway system as of 2004 was 46,837 miles (75,376 km) long. It is considered substantially complete, but small sections are still being added today such as the recently added Harbor Tunnel in Boston on interstate route 90.

The interstate highway system was officially launched in 1956 under the National Interstate and Defense Highways Act of 1956 and was spearheaded by Dwight D. Eisenhower. The highway's primary uses were for quick and easy automobile transportation between major US cities and also doubles as national defense highways.

The interstate highway system has many standards including requiring at least two lanes in each direction and a minimum median width of 36 feet in rural areas. The minimum outer shoulder width must be at least 10 feet and the minimum inner shoulder width must be at least four feet. However, the minimum travel lane width must be least 12 feet.

Contraflow is used mainly for evacuations from a storm such as a hurricane. This is when all lanes of interstate highway are used for one direction of travel only. This requires one side of the highway to handle traffic in the opposite direction that it normally goes. This allows for more people to evacuate and it also reduces traffic congestion.

Interstate highways that that run east and west use even numbers for their route numbers. The longest running highways use multiples of five that are even such as 10, 50 and 90. One good example is interstate highway 90 that runs from Seattle, Washington to Boston, Massachusetts.

Interstate highways that run north and south use odd numbers for their route numbers. The longest running highways use multiples of five that are odd such as 5, 55 and 95. One good example is interstate highway 95 that runs from Houlton, Maine to Miami, Florida.

Concurrency is when two interstate highway routes share the same physical road. This most often occurs for efficiency reasons and works well in rural areas where there is not too much traffic congestion. One good example is routes 90 and 94 sharing the same physical highway in the sparsely populated upper midwest and great plains.

Three digit interstate highway numbers are used for spurs and loops along a major interstate corridor. A spur runs into a city and uses an odd number in front of its parent route number, an example being route 395. A loop that runs around the city uses an even number in front of its parent route number, an example being route 495. Highways that run through cities or terminate don't use special route number designations.

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