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Interstate Frequently Asked Questions


Who created the Interstate System?

The concept of an Interstate system as we know it was first described in a 1939 report to Congress called Toll Roads and Free Roads. The report rejected the toll superhighway network Congress had suggested; revenue from tolls on most segments would not support the bonds issued for their construction. However, the report added that the country needed a toll-free express highway network. Thomas H. MacDonald, Chief of the U.S. Bureau of Public Roads, and Herbert S. Fairbank, Chief of the agency's Division of Information, prepared the report. The ideas expressed in the "free roads" portion of the report evolved through further study and experience before approval of the Federal-Aid Highway Act of 1956, but the Interstate System began with MacDonald and Fairbank.

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Why is President Dwight D. Eisenhower called the "Father of the Interstate System"?

Although the Federal-Aid Highway Act of 1944 authorized designation of a "National System of Interstate Highways," the legislation did not authorize an initiating program to build it. After taking office in January 1953, President Eisenhower made revitalizing the Nation's highways one of the goals of his first term. As an army Lieutenant Colonel in 1919, Eisenhower had accompanied a military convoy across the United States and saw the poor condition of our Nation's roads. Later, during his World War II stint as Commander of the Allied Forces, his admiration for Germany's well-engineered Autobahn highway network reinforced his belief that the United States needed first-class roads. As a result, Eisenhower formed internal committees to study the idea, enlisted the Nation's Governors to offer suggestions, and met with Members of Congress to promote the proposal. When legislation failed in 1955, observers predicted that in the presidential election year of 1956, the Democratic Congress would not approve such a significant plan sought by a Republican President. Nevertheless, President Eisenhower continued to urge approval and worked with Congress to reach compromises that made approval possible. The President signed the Federal-Aid Highway Act of 1956 on June 29, 1956.

Through the remainder of his years as President, he searched for ways to solve the problems that plagued the program in its early years and pushed for continued work on the Interstate System. His leadership in promoting the 1956 Act and moving the program forward on schedule has earned President Eisenhower the title "Father of the Interstate System."

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What was President Franklin D. Roosevelt’s role in creation of the Interstate System?

On February 2, 1938, President Franklin D. Roosevelt asked the U.S. Bureau of Public Roads, to study the feasibility of building toll superhighways on routes he had drawn on a U.S. map showing three east-west transcontinental routes and five north-south routes, with excess right-of-way that could be sold or rented to help pay for construction. Congress, hearing about the study, asked for a report on the topic. President Roosevelt transmitted Toll Roads and Free Roads to Congress on April 17, 1939. BPR had concluded that the toll superhighway network he had envisioned could not support itself financially, but that the country needed a toll-free interregional express highway network – the first formal outline of what would become the Interstate System. He followed up on April 14, 1941, by establishing a National Interregional Highway Committee to investigate the need for a limited system of national highways. The committee essentially finished its work by the end of the year, but the country’s entry into World War II delayed release of the report until January 12, 1944, when FDR transmitted Interregional Highways to Congress. The report, which refined the toll-free express highway vision from Toll Roads and Free Roads, prompted Congress in include a provision in the Federal-Aid Highway Act of 1944 calling for designation of a “National System of Interstate Highways.” Although the Act authorized designation of the network, it did not provide special funds for it or initiate a construction program. As a result, the country made only limited progress on the Interstate System until the Federal-Aid Highway Act of 1956 established a construction program, including a funding mechanism, for a nationwide freeway network.

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How long is the Interstate System?

Currently, the Interstate System is 46,876 miles long. The Federal-Aid Highway Act of 1956 imposed a statutory limitation on the Interstate mileage that would be built with Interstate Construction funds under the new program (41,000 miles at the time). Later legislation increased the limitation to 43,000 miles, of which a total of 42,795 miles has been used. Separate legislation allows the Federal Highway Administration to approve additional mileage if it meets full Interstate standards and would be a logical addition or connection. Beyond the 42,795 miles, this additional mileage is not "chargeable"—that is, it is not eligible for Interstate Construction funds under the 1956 Act, as amended, although the State may use other Federal-aid funds to help with construction.

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Who built the Interstate System?

The Interstate System was built under the principles of the Federal-aid highway program, which was established in 1916. The Federal Government made Interstate Construction funds available to the State highway/transportation agencies, which built the Interstates.

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Who owns it?

The States own and operate the Interstate highways.

The one exception is the Woodrow Wilson Memorial Bridge (I-95/495) over the Potomac River in the Washington area. The U.S. Bureau of Public Roads built the bridge under special legislation approved by President Dwight D. Eisenhower in August 1954. Although the District of Columbia, Maryland, and Virginia operate the bridge, it is owned by the Federal Highway Administration. When the first span of the replacement bridge, now under construction, is opened, the old bridge will be removed. The States will own the new Woodrow Wilson Memorial Bridge.

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What did it cost?

The final estimate of the cost of the Interstate System was issued in 1991. It estimated that the total cost would be $128.9 billion, with a Federal share of $114.3 billion. This estimate covered only the mileage (42,795 miles) built under the Interstate Construction Program. It excluded turnpikes incorporated into the Interstate System within the mileage limitation and the mileage added as a logical addition or connection outside the limitation but financed without Interstate Construction funds.

In all, Federal-aid legislation authorized a total of $119 billion to pay the Federal share of the cost of Interstate construction. (Interstate Construction funds were authorized through Fiscal Year 1996.)  

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Why does the Federal Government pay 90 percent of the cost?

The Federal-Aid Highway Act of 1944 authorized designation of a 40,000-mile "National System of Interstate Highways," but did not establish a program or special funding for its construction. The first such funding came under the Federal-Aid Highway Act of 1952, which authorized a token amount of $25 million a year for the Interstate System in Fiscal Years (FY) 1954 and 1955. The 1952 Act retained the standard matching ratio (Federal share: 50 percent). The Federal-Aid Highway Act of 1954 authorized $175 million a year for the Interstate System (FYs 1956 and 1957), with a Federal-State matching ratio of 60-40. The increased Federal share reflected the common understanding that the Interstate System is vitally important to national goals.   

As President Dwight D. Eisenhower began to promote creation of a program to build the Interstate Construction Program, the Nation's Governors made clear to him that they did not want to be forced to increase State taxes to pay the additional matching funds for the national program. Therefore, the President proposed to increase funds for the Interstate System, while boosting the Federal share to 90 percent. Under his proposal, the States would continue paying the same amount in matching funds for the Interstate System that they had been paying under the 1954 Act. When the program took shape in the Federal-Aid Highway Act of 1956, it differed in some ways from the President's proposal, particularly with regard to the source of funding for the program, but Congress retained the Federal-State matching share of 90-10 as a reflection of the Interstate Construction Program's importance to national goals. (In the western States with large amounts of untaxed public land, the Federal share could be increased to 95 percent.)

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Did construction of the Interstate System contribute to the national debt?

President Eisenhower insisted that the financing mechanism for the Interstate System be "self-liquidating," so that it could not add to the national debt. The president favored a toll highway network financed by bonds, but his aides convinced him that traffic volumes would not generate enough revenue in most corridors to repay bondholders with interest. Therefore, the plan the President submitted to Congress called for establishment of a Federal Highway Corporation to issue bonds to pay for the Interstate System up-front, with the Federal excise tax on gasoline and lubricating oil (which then went to the general Treasury without a linkage to highways) was dedicated to bond retirement. Congress rejected this plan, but adopted a proposal to finance the Interstate System on a pay-as-you-go basis with revenue from highway user taxes. The revenue was credited by the Department of the Treasury to the Highway Trust Fund established under the Federal-Aid Highway Act of 1956.

The Interstate Construction Program, like the Federal-aid highway program of which it is a part, operates on a reimbursement basis. After FHWA authorizes a State to proceed with a project, the State pays the bills for eligible activities, and then submits bills to the FHWA, which reimburses the State for the Federal share. The FHWA makes a commitment (or "obligation") to reimburse the Federal share, but Interstate development takes several years. As a result, the FHWA obligation results in reimbursements to the State for the Federal share over several years. The 1956 Act included a provision named after Senator Harry Flood Byrd (D-VA), the Chairman of the Senate Finance Committee, to ensure the Highway Trust Fund would contain enough money to pay the bills. If sufficient funds are not available, the program must be reduced administratively in proportion to the imbalance.

The Highway Trust Fund financing mechanism established in the 1956 Act satisfied President Eisenhower's "self-liquidating" demand. As a result, construction of the Interstate System did not contribute to a Federal deficit.

(In 1982, the Highway Trust Fund was divided into a Highway Account and a Transit Account, which also receives some highway user tax revenue.)

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Why did it cost so much more than expected?

During debate leading up to the Federal-Aid Highway Act of 1956, Congress used an estimate of $27 billion. This estimate was flawed in several ways. It was based on a report by the U.S. Bureau of Public Roads (BPR), which covered only the 37,700 miles designated in 1947. The BPR estimated that to build this mileage in 10 years to meet 1974 traffic needs would cost $23.2 billion, based on midyear 1954 prices. Second, President Eisenhower's Advisory Committee on a National Highway Program under General Lucius D. Clay (Rt.)—known as the "Clay Committee"—added only $4 billion for urban feeders and collectors, bringing the total to $27.2 billion. Considering that the BPR had assumed urban-rural costs for the mileage designated in 1947 would be split $12.5 billion-$10.7 billion, and that an additional 2,300 miles of urban routes had been designated in 1955, the Clay Committee's estimate was flawed.

Beyond the errors in the initial estimate, the 1956 Act added 1,000 miles to the Interstate System. The Federal-Aid Highway Act of 1968 added 1,500 miles, and subsequent legislation increased the mileage as well. In addition, design standards were stricter beginning in 1956, and compliance with essential environmental requirements enacted in the 1960s added to the cost of projects. As might be expected, inflation was a major factor as well.

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What was the first Interstate?

On August 2, 1947, the Federal Works Administrator, Major General Philip B. Fleming, approved the first 37,700 miles of the Interstate System recommended by Commissioner of Public Roads Thomas H. MacDonald. Although Congress had not established a program to build the network, the States used Federal-aid primary funds to build many projects in the designated Interstate corridors.

With the approval of the Federal-Aid Highway Act of 1956, the  formal Interstate Construction Program began, with higher design standards, a funding program, and a national commitment.. Two States can claim the first project, depending on how "first" is defined.

The first project to go to construction with Interstate Construction funds under the 1956 Act was in Missouri. The project on U.S. 40 (later designated the I-70 Mark Twain Expressway) in St. Charles County got underway on August 13, 1956. Officials erected a sign stating, "This is the first project in the United States on which actual construction was started under provisions of the new Federal-Aid Highway Act of 1956." 

Kansas had begun a construction project on U.S. 40 (I-70) west of Topeka before the 1956 Act, but awarded the final paving contract under the new legislation. Because this was the first paving under the 1956 Act, Kansas erected a sign claiming, "This is the first project in the United States completed under provisions of the new Federal-Aid Highway Act of 1956."

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When did the program end?

It didn't. The program authorized by the Federal-Aid Highway Act of 1956 includes one last piece of Interstate that is likely to be built under the terms of the 1956 Act. It is a connection north of Philadelphia to close the last gap in I-95. The project involves an I-95 interchange with the Pennsylvania Turnpike and an additional bridge over the Delaware River parallel to the existing bridge. Review of the proposed project under the National Environmental Policy Act of 1969 has been completed and detailed design is underway.

In addition, States continue to develop routes outside the 1956 Act program that may be added to the Interstate System under existing legislation or that have been or will be declared "future Interstates" by Federal legislation.

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Who sets traffic rules on the Interstate System?

Because the States own and operate the Interstates, the States establish the operating requirements, such as speed limits. The States also are responsible for enforcement.

The National Committee on Uniform Traffic Laws and Ordinances (NCUTLO), which includes State motor vehicle administrators and police officers, publishes a compendium of model traffic laws and rules of the road. The goal of NCUTLO is to promote uniformity across the States, but each State is free to adopt its own traffic laws and rules based on its unique circumstances.

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What happened to the 55 mph Federal speed limit?

There never was a national speed limit of 55 mph. The States determine speed limits.

The impression of a "national speed limit" stems from the Emergency Highway Energy Conservation Act, which President Richard M. Nixon signed on January 2, 1974. In the midst of an energy crisis touched off by conflict in the Middle East and a subsequent oil embargo imposed by the Organization of Petroleum Exporting Countries that forced Americans into long lines at gas stations, the Act was part of a nationwide effort to reduce oil consumption. The law prohibited the Federal Highway Administration from approving highway projects in any State having a maximum speed limit over 55 mph. The States could retain higher speed limits if they wished, but at the cost of losing Federal-aid highway funding. As a result, all States complied with the legislation.

The Surface Transportation and Uniform Relocation Assistance Act of 1987 allowed the States to increase speeds to 65 mph on rural Interstate routes without penalty. The National Highway System Designation Act of 1995 extended the authority to all roads. The States now have full control of speed limits.  

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Is the left lane for higher speeds?

Although the left lanes of multi-lane freeways are widely viewed as the "high speed lanes" or "the fast lanes," the speed limit applies to all lanes on any given street or highway. The intent is that vehicles going slower than the posted speed limit should stay to the right.

Why are bicycles prohibited from using the Interstate shoulders?

Each State establishes the operating rules that determine which vehicles are allowed on the Interstate highways under their jurisdiction. Most States do not allow bicyclists on the Interstate shoulders, but bicycle use is permitted in some States, particularly in the west where there is less traffic and where good alternative routes may not exist for bicycles. Determining if bicycle access should be permitted is done only after careful study and consideration of how bicyclists and motor vehicle traffic can safely negotiate on- and off-ramps. The safety of all roadway users must be considered. In addition, some Interstate highways, mainly in urban areas, have been built with bicycle paths.   

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Are the Interstates really safer?

One of the primary reasons for building the Interstate System was to improve the safety of the highway users: drivers, passengers, and pedestrians. Over the past 50 years, the Interstate System has done much to make highway travel safer and more efficient. Relative safety is measured by the "fatality rate" (fatalities per 100 million vehicle miles traveled, a measure used so data can be compared as traffic volumes change). The Interstate System is the safest road system in the country, with a fatality rate of 0.8—compared with 1.46 for all roads in 2004.

When the Interstate Construction Program began in 1956, the national fatality rate was 6.05. This improvement in safety has been the result of many factors working together:  the shifting of traffic onto the safer Interstate highways and technological advances in safety, such as wider shoulders; slid-resistant pavements; better guardrail, sign, and markings; clearer sight distances; and breakaway sign posts and utility poles. In addition, many other factors have contributed to improved safety on the Nation's highway system, including new vehicle safety features, such as shatter proof glass, padded interiors, safety belts and air bags; programs to reduce impaired driving; and the combined, coordinated efforts of many private organizations and public agencies working together to make the Nation's highways ever safer.

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Why don't you put metric speed and distance signs on the Interstate System?

In the 1970's, the Federal Highway Administration (FHWA) considered converting highway signs, such as speed limit signs, to metric units of measurement. After the proposal was made public, the agency received an unusually high number of comments—more than 5,000 comments, about 98 percent of which were negative. The idea was dropped.

The recent effort to convert the country to metric units of measurement dates to the Omnibus Trade and Competitiveness Act of 1988, which requires all Federal Agencies to use metric units in their procurements, grants, and other business-related activities except to the extent that it is impractical or likely to cause significant inefficiencies or loss of markets to U.S. firms. Based on this requirement, the FHWA reconsidered the subject of sign conversion, but the public reaction was again overwhelmingly negative. To avoid a public backlash against metric conversion, the FHWA issued a policy statement in April 1994 indicating that the FHWA would not pursue sign conversion. The following year, the National Highway System Designation Act of 1995 prohibited the Secretary from requiring the States to use Federal-aid highway or State funds "to construct, erect, or otherwise place or to modify any sign relating to a speed limit, distance, or other measurement on a highway for the purpose of having such sign establish such speed, limit, distance, or other measurement using the metric system." Under current law, a State may, if it chooses, use Federal-aid funds to include metric measurements on distance or speed signs, but none is doing so as of late 2018.

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Who numbered the Interstates?

Following enactment of the Federal-Aid Highway Act of 1956, officials of the U.S. Bureau of Public Roads (BPR) and the American Association of State Highway Officials (AASHO) agreed that AASHO should apply numbers to the Interstate System, as it did to the U.S. numbered highways. In fact, the numbering plan for U.S. numbered highways was the model for the Interstate System—but in mirror image (for example, U.S. 1 is on the East Coast, while I-5 is on the West Coast; U.S. 10 is in the north while I-10 is in the south). With basic guidelines in hand, AASHO's Executive Secretary, A. E. "Alf" Johnson, applied numbers to the Interstate map. His handiwork was approved by AASHO's Route Numbering Subcommittee and Executive Committee and adopted by the BPR in September 1957.

Because the States own the Interstates, cooperation with AASHO (and its successor, the American Association of State Highway and Transportation Officials [AASHTO]) in the numbering of Interstates has continued. However, under Title 23, Code of Federal Regulations, Subsection 470.115(a) ("Approval authority"), the Federal Highway Administration (FHWA) has the ultimate authority to approve/disapprove Interstate route numbers: 

The Federal Highway Administration will approve Federal-aid highway system actions involving the designation, or revision, of routes on the Interstate System, including route numbers, future Interstate routes, and routes on the National Highway System.

In view of the Federal-State partnership, the State transportation departments submit applications to AASHTO when new numbers are needed or numbering changes are desired. AASHTO submits the applications to the FHWA, which informs AASHTO of its position. AASHTO then acts on the proposal, consistent with the FHWA's action. If disagreement were to occur on a numbering proposal, the FHWA and AASHTO would resolve the issue before AASHTO acted.

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Why doesn't the Interstate System have an I-50?

The Interstate numbering plan was based on the plan used to number the U.S. numbered highways, but in mirror image (for example, U.S. 1 is on the East Coast, while I-5 is on the West Coast; U.S. 10 is in the north while I-10 is in the south). In both plans, numbers ending in zero are used for transcontinental and other major multi-State routes. However, one of the rules for Interstate numbering is that numbers are not duplicated on Interstate highways and U.S. numbered routes in the same State. Duplicate numbers would be confusing for motorists; for example, if told to take "Route 50," the motorist might follow the wrong one. Because the Interstate numbering plan is a mirror image of the U.S. numbered highway plan, I-50 would be located in some of the same States as U.S. 50 (Ocean City, Maryland, to Sacramento, California). Therefore, "50" has not been used for an Interstate route.

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I-99 is out of sequence—what can be done about it?

Although State and Federal officials normally select Interstate route numbers, Congress made the choice of "99" for upgraded U.S. 220 in Pennsylvania. Section 322 of the National Highway System Designation Act of 1995 states that the specified section of U.S. 220 ". . . is designated as Interstate Route I-99."  Therefore, only a statutory revision can change the number.

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Why don't you correct inconsistencies in numbering?

Although Federal and State officials try to be consistent in Interstate System numbering, an occasional inconsistency is inevitable in a complicated, evolving network. They cause little difficulty for the traveling public. Most motorists are not aware of the numbering pattern; when driving in areas with which they are unfamiliar, motorists choose routes based on maps, signs, or directions received along the way.

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Who designed the Interstate shield?

Following enactment of the Federal-Aid Highway Act of 1956, the American Association of State Highway Officials (AASHO) asked State highway officials to suggest designs for an Interstate marker. Dozens of proposals were submitted. The best were displayed along a road when State highway officials attended a meeting in Illinois so they could observe the signs in different  situations, such as day and night. Based on the officials' observations, AASHO's Route Numbering Subcommittee adopted the design submitted by Texas, with the addition of the word "Interstate" as proposed by the Missouri design for the top portion of the shield. It was approved on August 14, 1957. AASHO secured Trademark Registration 835.635 for the shield in 1967,  to prevent private entities from using  Interstate-like advertising signs near the highways where they might confuse motorists.

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What is the story behind the "Eisenhower Interstate System" signs—and why don't all the States put them up?

On October 15, 1990, President George H. W. Bush signed Public Law 101-427 changing the official name of the Interstate System to honor the President who did so much to bring it about. Based on an amendment in the Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA), it is now called the Dwight D. Eisenhower National System of Interstate and Defense Highways.

Section 6012 of ISTEA directed the Secretary of Transportation to determine an appropriate system or emblem to be placed on Interstate highway signs to commemorate the former President's vision. In conducting the study, the Federal Highway Administration (FHWA) created a partnership with the American Association of State Highway and Transportation Officials (AASHTO) and representatives of the Eisenhower family, the Eisenhower Center, and the Eisenhower Society (collectively, the Eisenhower group).

After considering over 50 designs submitted by AASHTO member States and FHWA employees, a committee of the partners selected three designs and forwarded them to AASHTO and the Eisenhower group for comment. At a meeting of its Executive Committee, AASHTO indicated its preference for one design, recommending only a minor color change. The Eisenhower group, working independently of AASHTO, recommended the same design. The FHWA, which accepted the two independent decisions, altered the color on the preferred design and made some other minor improvements. The sign was described in a report submitted to Congress on January 14, 1993:  "The official symbol commemorating the vision of President Eisenhower in creating the Dwight D. Eisenhower [National] System of Interstate and Defense Highways [will] be a 36-inch by 36-inch square blue sign, with five silver stars in a circle on the upper half of the sign, and the words EISENHOWER INTERSTATE SYSTEM in white on a lower half of the sign."

The sign was unveiled in the Mike Mansfield Room of the U.S. Congress on July 29, 1993. Participants included Senators Bob Dole (R-KS), Max Baucus (D-MT), and John Chafee (R-RI); Representatives Norman Y. Mineta (D-CA), Nick J. Rahall (D-WV), and Bud Shuster (R-PA); members of the Eisenhower family including President Eisenhower's son John Eisenhower, and granddaughter Susan Eisenhower; and Federal Highway Administrator Rodney E. Slater.

The State transportation departments may use regular Federal-aid highway funds, which are made available to the States on a formula basis, to install Eisenhower Interstate System signs. However, each State determines whether to install them. As a result, motorists will see the signs in some States, but not in others.

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Was President Eisenhower really surprised to discover that the Interstate System included urban freeways?

The urban freeways were an important element of the Interstate System from its unveiling in the 1939 report to Congress: Toll Roads and Free Roads. During congressional hearings in 1955 and 1956, Mayors and municipal associations testified in favor of the Interstate System because of the benefits the cities expected to receive from urban highway segments. In fact, the U.S. Bureau of Public Roads had published General Location of National System of Interstate Highways in September 1955 with 100 pages of maps showing the urban Interstates. This publication—known as the Yellow Book because of the color of its cover—was distributed to the Members of Congress as well as State highway agencies and city governments.

However, President Eisenhower was not aware of the urban highway segments. His model for the Interstate System had been Germany’s autobahn: the rural highway network he had seen during and after World War II. In the summer of 1959, rumor has it that he discovered the existence of urban highway segments when he passed construction of the Capital Beltway while being driven to the presidential retreat at Camp David. An alternative theory is that he discovered the truth when he talked with urban planners about the District of Columbia’s freeway network. Whichever way he found out, President Eisenhower asked his friend and adviser, retired General John Bragdon, to conduct a broad review of the Interstate program.

On April 6, 1960, the President met with Bragdon, Secretary of Commerce Frederick Mueller, Federal Highway Administrator Bertram Tallamy, and others, to review Bragdon’s preliminary findings, including his view that the Interstates should include only roads that carry intercity traffic around and into cities. Other urban Interstates should be eliminated. Mueller and Tallamy objected. The President responded that he now knew that the city officials and Members of Congress understood the urban highway segments were part of the program, even if they were contrary to his views. By then, he had heard of, but not seen, the Yellow Book (Mueller handed him a copy) and had been told that it was one of the prime reasons Congress passed the Federal-Aid Highway Act of 1956. Although the concept was against his wishes, he felt his hands were tied. The urban Interstates would remain part of the program.

The meeting ended, and so did the issue.

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If I want to suggest another Interstate, how should I go about it?

Suggestions for building or designating another Interstate should be submitted to the State transportation department. The Federal Highway Administrator may act only on requests submitted by a State transportation department (or departments in the case of multi-State routes). The route must be built to Interstate standards, be a logical addition or connection, and coordinated with affected jurisdictions. If the route is not yet complete, the State may request designation as a future part of the Interstate System.

No special Interstate funding is available to build the route to Interstate standards, but the State may use regular Federal-aid highway funds, made available each year by statutory formula, for the route on a priority basis within funding limits. From a motorist's standpoint, there is no difference between Interstate highways funded under the 1956 Act, as amended, and Interstates funded in some other way.

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How can I get more lanes on my Interstate?

Because the Interstates are owned by the States and operated by the State transportation departments, anyone concerned about operation of an Interstate highway should contact State transportation officials. They are in the best position to discuss proposals to upgrade Interstate highways. They also can explain the project development process, which includes compliance with environmental requirements such as the National Environment Policy Act, public involvement, and identification of funding through the statewide transportation planning process (or metropolitan transportation planning process).

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How can we get an interchange built to improve access to the Interstate System?

The Interstate System has full access control. This means only interchanges designed for safe, efficient operation provide access. Although States own the Interstate highways, the Federal Highway Administration (FHWA) has retained authority to approve any change in access, including new or modified interchanges.

State transportation officials must initiate consideration of additional interchanges by submitting an Interchange Justification Report to the FHWA Division Office in the State. The FHWA may approve the access point for the interchange if it complies with the policy on "Additional Interchanges to the Interstate System" published in the Federal Register on February 11, 1998 ( If the access point is approved, the State transportation department is responsible for following the normal project development stages (assessment of environmental impacts, detailed design, and, if needed, acquisition of right-of-way) before construction can begin.

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There's a big pothole on my Interstate-who could I contact?

Contact the State transportation department and let its maintenance officials know of the problem.

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How can the States charge tolls on Interstates I paid taxes to build?

The Interstate System is free of tolls for the most part, but tolls are collected on some segments. Most major toll roads were planned or built before the Congress authorized significant amounts of Federal funding for the Interstate highway program. These segments were built by toll authorities created by State or local legislation to issue bonds as a way of financing construction. Toll revenue is used to retire bonds and cover operating and maintenance expenses.

One of the controversial issues Congress considered before passing this legislation was what to do with the turnpikes that had been built or planned in Interstate corridors without Federal funding. In an extensive congressional debate, members considered purchasing the bonds to allow removal of the tolls, but this option would have cost hundreds of millions of dollars without creating any new Interstate mileage. Another option was considered—constructing toll-free Interstate highways in these corridors—but it would have diverted funds needed for new highways in areas not served by Interstate-type facilities. It also would have jeopardized the legitimate right of the toll authorities to pay their bondholders. Therefore, Congress decided to include some toll facilities in the Interstate System to ensure connectivity.

Federal law has changed over the years to allow turnpikes on the Interstate System under other circumstances. In all, the 46,876-mile Interstate System includes approximately 2,900 miles of turnpikes.

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How can I get a commemorative name for the Interstate in my town/county/State?

Although the Federal Government provided funds to help build the Interstate System, States own and operate the roads. As a result, the Federal Highway Administration (FHWA) does not have the authority to name the routes. The States may, if they wish, name any highway under their jurisdiction. Each State has its own mechanism for doing so. In some cases, the State legislature must take the initiative in passing a law to name the route. In other cases, the State transportation department is responsible.

Although the FHWA is not involved in the naming of highways, the FHWA is concerned about how the name is used or memorialized. This concern is based on safety and operational considerations. For example, if an Interstate highway is named after an important person, the FHWA would be opposed to placing a statue of the person on the roadside where it could have deadly consequences if struck by a vehicle. Similarly, a sign providing information on the individual, military unit, or historic event should be placed in a location, such as a safety rest area, where it will not create safety or operational difficulties. Once a highway is officially named, resolution of the sign placement and location issue is a matter to be cooperatively determined between the State transportation department and the FHWA.

Congress also can name Interstate highways by including the designation in the statutory language of a Federal law, such as the multi-year reauthorization bills for the Federal-aid highway program or the annual appropriations acts for the U.S. Department of Transportation.

Anyone interesting in naming an Interstate highway should ask the State transportation department about the steps that would have to be followed in that State.

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Is it true that one out of five miles is straight so airplanes can land on the Interstates?

No. This is a myth that is so widespread that it is difficult to dispel. Usually, the myth says the requirement came from President Dwight D. Eisenhower or the Federal-Aid Highway Act of 1956. However, no legislation, regulation, or policy has ever imposed such a requirement. Airplanes do sometimes land on Interstates in an emergency, but the highways are not designed for that purpose.

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Is it true that every so often there has to be a curve in a section of Interstate, to help keep drivers from falling asleep?

Yes and no. Design standards don’t require curves to keep drivers from falling asleep, but that is one reason curves may be included.

Although design standards don’t require curves at specific distances in the alignment of an Interstate highway, curves are introduced for a variety of reasons. The reasons including taking advantage of the terrain along the route; avoiding obstacles or cultural development in the path; and, accommodating environmentally sensitive areas or mitigating impacts on them. A curvilinear alignment also reduces the boredom of driving along extremely long tangent sections (engineer speak for “straight roads”), keeping the driver alert.

Excessive curvature or poor combinations of curvature limit capacity, cause economic losses due to increased travel time and operating costs, and detract from a pleasing appearance. Alignments should be as direct as practical; and consistent with the topography, developed properties, and community values. A flowing line that conforms generally to the natural contours of the land is preferable to an alignment with long tangents slashing through the terrain. Construction scars can be kept to a minimum and natural slopes and growth can be preserved.

The alignment of a proposed highway should be determined by a detailed study of the area through which the road passes. The finished highway, road, or street should be an economical, pleasant, and safe facility on which to travel.

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Can I set up a business in safety rest areas or welcome centers selling food or other products to motorists?

No. Section 111 of Title 23 ("Highways"), United States Code, prohibits the States from commercializing the right-of-way along the Interstate System. The commercial prohibition in Section 111 dates to 1956 when Congress was considering the legislation that launched the Interstate Highway Program. The Members considered following the model of the toll turnpikes that provided commercial facilities in service areas for motorists who would otherwise have to leave the facility and pay a toll to continue their journey. Congress rejected this model by enacting the Section 111 prohibition on commercialization. The intent was to avoid State approved or supported monopolies for traveler services, such as those provided on toll roads. During the debate, Representative Charles A. Vanik (D-OH) explained what Congress had in mind:  "Let the highway traveler turn off the Interstate system if he requires food, motor-vehicle service, lodging or Stuckey's pecans."

The Surface Transportation Assistance Act of 1982 modified the commercial restriction by permitting vending machines in rest and recreation areas constructed or located on the Interstate right-of-way.

Safety rest areas are intended to serve motorists by allowing them to take a short break, use the rest rooms, shake off drowsiness, and then move on. The absence of commercial services (except for vending machines) means motorists can stop without any pressure to make purchases. For food, gasoline, lodging, and other commercial services, motorists can leave the highway and return to it without a toll charge.

Section 1310 of the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users, approved August 10, 2005, provides that the Secretary of Transportation shall establish an Interstate oasis program for designating facilities off the Interstate right-of-way that offer products and services to the public, 24-hour access to restrooms, and parking for automobiles and heavy trucks, and meet other standards to be determined. Thus, as in the past, Congress has chosen an alternative for accommodating Interstate motorists that does not involve commercial services within the Interstate right-of-way (again, with vending machines as the exception).

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Why don't you pick up the litter?

Litter along the highways has been a problem for years, long before the Interstate System came into existence. States enact laws imposing fines for littering, but can enforce the law only if a police officer sees an act of littering. Litter is part of each State's road maintenance responsibility, with funding for litter control coming from State sources.

One approach to litter pick-up is the Adopt-A-Highway concept. It began in Texas in 1985 as a way of meeting a public need by tapping the tremendous public spiritedness of citizens. Each State and each community can adapt the concept to its own unique situation. In general, when a group or individual agrees to clear litter periodically from a stretch of road, the State transportation department (or county or city) provides training to ensure litter is collected safely, along with trash bags, a sign displaying the name of the organization that adopted the highways, reflective vests, and other equipment.

Anyone concerned about roadside litter along the Interstates is encouraged to contact the State transportation department to discuss the Adopt-A-Highway program or other methods the State may use to collect litter.

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Didn't the Lady Bird Johnson Act ban billboards along the Interstate System?

The Highway Beautification Act of 1965 (HBA), enacted with the help of Lady Bird Johnson and signed by her husband, President Lyndon B. Johnson, did not abolish billboards, or even abolish all billboards along certain highways, such as the Interstate System. Rather, as amended over the years, it requires the Federal Highway Administration to ensure that the State transportation departments maintain "effective control of the erection and maintenance" of signs, displays, or devices, including outdoor advertising signs that are visible from the highway, beyond 660 feet of the Interstate right-of-way outside urban areas, and erected with the purpose of their message being read from the highway. Signs not subject to meeting those criteria are limited to directional and official signs; signs advertising products for sale on the property on which they are located; signs lawfully in existence before enactment of the HBA; and, those advertising the distribution by nonprofit organizations of free coffee to individuals traveling on the Interstates.

The HBA also allows State and local officials to impose more stringent controls on billboards than those mandated by Federal law. The result varies from State to State and even from community to community, with some States essentially banning billboards while others allow them to the maximum extent permitted under the HBA.

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Can I pick the beautiful wildflowers along the Interstate? 

Many departments of transportation have begun planting wildflowers not only for their beauty but to save costs on mowing grass and trimming other plant growths. Enjoy the increasing roadside wildflowers, but leave them for the pleasure of others. It is especially dangerous to stop on a highway shoulder to pick or photograph these flowers. It is also illegal in most States. By the time you arrive at your destination, the wildflowers will likely have wilted anyway. You will have lost their beauty, and we will have lost another seed source.

There is only one condition where you may dig up native wildflowers, grasses, ferns, etc., along the Interstate. Every other condition is illegal and/or unsafe. Highway construction projects are planned many years ahead. If you know of a native plant remnant that should be salvaged and moved to a safe location before construction begins, contact your State transportation department to ask permission.

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Can my science class or community organization plant trees or flowers on Interstate rights-of-way near our city? 

Yes, but you must contact your State transportation department to locate an appropriate spot and learn how to plant safely. Many States require a plan and a permit for volunteer plantings in rest areas, city entry sites, or other locations. Remember that trees are fixed objects and can be deadly if struck by a vehicle moving at high speed, so trees must be planted in areas where they will not cause safety problems. Some States have special planting programs within Adopt-A-Highway or Adopt-A-Spot volunteer programs. Call and learn more.

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Why do we call Interstate turnpikes “freeways” if they charge tolls?


The term “freeway” refers to how motorists enter and leave the highway, not how the highway was financed. A freeway has full control of access to provide for high levels of safety and efficiency in the movement of large volumes of traffic at high speeds. Freeways have grade separations at all railroads and public crossroads, with interchanges at selected crossroads for access. Traffic can enter on via the interchanges.

The toll turnpikes that have been incorporated into the Interstate System are freeways. They must have full control of access to prevent motorists from using the facility without paying the toll.

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What is vertical clearance and why did the Department of Defense (DOD) object to the minimum vertical clearance for the Interstate System in the 1950s?

“Vertical clearance” is the distance from the top of the pavement to the bottom of structures crossing over the highway. It is typically at least 1 foot higher than the legal vehicle height, plus an allowance for future resurfacing that could raise the top of the pavement.

Although the Federal-Aid Highway Act of 1956 added the words “and defense” to the name of the Interstate System (now the Dwight D. Eisenhower National System of Interstate and Defense Highways), the primary justification for the network was its civilian benefits, such as economic opportunity, safety, relief of congestion, and evacuation of cities. At the height of the Cold War and with an atomic or hydrogen bomb attack a conceivable possibility, Congress added “and Defense” to the name in recognition of the fact that the Interstate System would benefit the military, too. However, the emphasis on civilian needs was consistent with the position of the Department of War (now Defense, of course) dating to the early 1920s—if we build a road network adequate for civilian needs, it will serve defense needs as well, with some additions to connect with bases or military plants. It would not be possible to justify such an expenditure solely on the basis of military needs.

In developing minimum design standards for the Interstate System, the State highway agencies and the Bureau of Public Roads (BPR) agreed in July 1956 to include a minimum vertical clearance of 14 feet in Policy on Design Standards – Interstate System prepared by the American Association of State Highway Officials (AASHO) and adopted by the BPR for use on Interstate projects. This figure wasn't pulled out of thin air. The DOD had previously indicated, in 1949 and 1955, that a 14-foot vertical clearance was adequate for most military vehicles. However, after the Soviet Union launched its Sputnik satellite in October 1957, the DOD determined that a 17-foot vertical clearance was needed for some larger equipment, such as the Atlas intercontinental ballistic missile, that could not be transported by rail.

This change led to a debate between the DOD and the BPR that that was resolved by a compromise in 1960. On January 27, 1960, the BPR issued instructions to its field offices changing the minimum standard to 16 feet for Interstate highways in rural areas. In urban areas, “application of the 16-foot clearance shall be limited to a single routing where the revised vertical clearance can be developed most economically, even though that single route is indirect.”  All projects under design or construction were to be revised according to the new standard. The first construction project affected by the change was in Michigan, where highway officials using hydraulic jacks lifted the Clear Lake Road overpass on I-94 near Lansing from a clearance of 14-feet, 6-inches to 16-feet, 3-inches.

As for the routes built to the old standard, DOD, Federal Highway Administration (FHWA), and AASHO agreed in 1969 on a 26,000-mile priority network that had 350 deficient structures and served about 95 percent of the major military installations. On the priority network, the States were encouraged to implement, as rapidly as practical, those modifications necessary to obtain a 16-foot clearance. Off the priority network, the 16-foot clearance would be implemented only in conjunction with other construction work. The FHWA explained that, “If the work necessary to obtain the clearance is a logical addition and the cost is not excessive, it should be incorporated into the overall project.”

The DOD remains concerned about vertical clearance. Today, the minimum vertical clearance standards apply to all rural Interstates (not just a priority network) and a single Interstate through each urban area. All exceptions to this requirement, whether for new construction or a reconstruction project that does not provide for the 16-foot minimum vertical clearance, would be coordinated with the DOD. The FHWA stressed that this agreement applied to the full roadway width, including shoulders for the through lanes, as well as ramps and collector-distributor roadways in Interstate-to-Interstate interchanges. The vertical clearance policy has been incorporated into Policy on Design Standards – Interstate System.

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When did President Eisenhower sign the Highway Revenue Act of 1956?

The Highway Revenue Act of 1956 was not a separate piece of legislation.

On February 6, 1956, Representative Hale Boggs (D-La.) of the House Ways and Means Committee introduced H.R. 9075, the Highway Revenue Act of 1956. It contained a financing mechanism for the Interstate System based on the concept that all revenue from highway user taxes would be set aside for highway purposes. At the suggestion of Secretary of the Treasury George Humphrey during testimony a few days later, Representative Boggs modified the bill to provide the linkage by creating a Highway Trust Fund modeled on the Social Security Trust Fund.

The Boggs Bill was submitted to the Committee on Public Works where Representative George H. Fallon (D-Md.), Chairman of the Subcommittee on Roads, combined it with his authorizing bill, the Federal-Aid Highway Act of 1956. Although congressional action would modify the Highway Revenue Act of 1956 in some ways, it would remain part of the bill the House of Representatives and Senate approved on June 26, 1956. As a result, the bill President Eisenhower signed on June 29, 1956, and that became Public Law 84-627, included the Highway Revenue Act of 1956 as Title II. Title I was called the Federal-Aid Highway Act of 1956.

In short, the President had to sign only one bill, not two, to create the program that gave the country the Interstate System.