|Dwight D. Eisenhower National System of Interstate and Defense Highways|
Highway shields for Interstate 80, Business Loop Interstate 80, and the Eisenhower Interstate System
|Length||48,191 mi (77,556 km)|
|Formed||June 29, 1956|
|Interstates||Interstate X (I-X)|
World War II
President of the United States
The Dwight D. Eisenhower National System of Interstate and Defense Highways, commonly known as the Interstate Highway System, is a network of controlled-access highways that forms part of the National Highway System in the United States. Construction of the system was authorized by the Federal Aid Highway Act of 1956. The system extends throughout the contiguous United States and has routes in Hawaii, Alaska, and Puerto Rico.
The U.S. federal government first funded roadways through the Federal Aid Road Act of 1916, and began an effort to construct a national road grid with the passage of the Federal Aid Highway Act of 1921. After Dwight D. Eisenhower became president in 1953, his administration developed a proposal for an interstate highway system, eventually resulting in the passage of the Federal Aid Highway Act of 1956. Construction of the Interstate Highway System was proclaimed complete in 1992, though some planned routes were canceled and several routes have stretches that do not fully conform with federal standards. The cost of construction of the Interstate Highway System was approximately $114 billion (equivalent to $521 billion in 2018). The original system has been expanded numerous times through the creation of new designations and the extension of existing designations.
Though much of their construction was funded by the federal government, Interstate Highways are owned by the state in which they were built. All Interstates must meet federal standards such as having controlled access, avoiding at-grade intersections, and complying with federal traffic sign specifications. Interstate Highways use a numbering scheme in which primary Interstates are assigned one- or two-digit numbers and shorter routes are assigned three-digit numbers where the last two digits match the parent route. The Interstate Highway System is partially financed through the Highway Trust Fund, which itself is funded by a federal fuel tax. Though federal legislation initially banned the collection of tolls, some Interstate routes are toll roads.
As of 2016 [update] , about one-quarter of all vehicle miles driven in the country used the Interstate Highway System, which had a total length of 48,191 miles (77,556 km). Several future routes are in development.
The United States government's efforts to construct a national network of highways began on an ad hoc basis with the passage of the Federal Aid Road Act of 1916, which provided $75 million over a five-year period for matching funds to the states for the construction and improvement of highways.The nation's revenue needs associated with World War I prevented any significant implementation of this policy, which expired in 1921.
In December 1918, E. J. Mehren, a civil engineer and the editor of Engineering News-Record , presented his "A Suggested National Highway Policy and Plan" 50,000-mile (80,000 km) system, consisting of five east–west routes and 10 north–south routes. The system would include two percent of all roads and would pass through every state at a cost of $25,000 per mile ($16,000/km), providing commercial as well as military transport benefits.during a gathering of the State Highway Officials and Highway Industries Association at the Congress Hotel in Chicago. In the plan, Mehren proposed a
In 1919 the U.S. Army sent an expedition across the U.S. to determine the difficulties that military vehicles would have on a cross-country trip. Leaving from the Ellipse near the White House on July 7, the Motor Transport Corps convoy needed 62 days to drive 3,200 miles to the Presidio army base on San Francisco Bay. They experienced significant difficulties including rickety bridges, broken crankshafts, and engines clogged with desert sand.
Dwight Eisenhower, then a 28-year-old lieutenant, accompanied the trip “through darkest America with truck and tank,” as he later described it. Some roads in the West were a “succession of dust, ruts, pits, and holes.” Eisenhower recalled that, “The old convoy had started me thinking about good two-lane highways... the wisdom of broader ribbons across our land.”
As the landmark 1916 law expired, new legislation was passed—the Federal Aid Highway Act of 1921 (Phipps Act). This new road construction initiative once again provided for federal matching funds for road construction and improvement, $75 million allocated annually.Moreover, this new legislation for the first time sought to target these funds to the construction of a national road grid of interconnected "primary highways", setting up cooperation among the various state highway planning boards.
The Bureau of Public Roads asked the Army to provide a list of roads that it considered necessary for national defense. 20,000 miles (32,000 km) of interconnected primary highways—the so-called Pershing Map.In 1922, General John J. Pershing, former head of the American Expeditionary Force in Europe during the war, complied by submitting a detailed network of
A boom in road construction followed throughout the decade of the 1920s, with such projects as the New York parkway system constructed as part of a new national highway system. As automobile traffic increased, planners saw a need for such an interconnected national system to supplement the existing, largely non-freeway, United States Numbered Highways system. By the late 1930s, planning had expanded to a system of new superhighways.
In 1938, President Franklin D. Roosevelt gave Thomas MacDonald, chief at the Bureau of Public Roads, a hand-drawn map of the United States marked with eight superhighway corridors for study.In 1939, Bureau of Public Roads Division of Information chief Herbert S. Fairbank wrote a report called Toll Roads and Free Roads, "the first formal description of what became the Interstate Highway System" and, in 1944, the similarly themed Interregional Highways.
The Interstate Highway System gained a champion in President Dwight D. Eisenhower, who was influenced by his experiences as a young Army officer crossing the country in the 1919 Motor Transport Corps convoy that drove in part on the Lincoln Highway, the first road across America. He recalled that, “The old convoy had started me thinking about good two-lane highways... the wisdom of broader ribbons across our land.”Eisenhower also gained an appreciation of the Reichsautobahn system, the first "national" implementation of modern Germany's Autobahn network, as a necessary component of a national defense system while he was serving as Supreme Commander of Allied Forces in Europe during World War II. In 1954, Eisenhower appointed General Lucius D. Clay to head a committee charged with proposing an interstate highway system plan. Summing up motivations for the construction of such a system, Clay stated,
It was evident we needed better highways. We needed them for safety, to accommodate more automobiles. We needed them for defense purposes, if that should ever be necessary. And we needed them for the economy. Not just as a public works measure, but for future growth.
Clay's committee proposed a 10-year, $100 billion program, which would build 40,000 miles (64,000 km) of divided highways linking all American cities with a population of greater than 50,000. Eisenhower initially preferred a system consisting of toll roads, but Clay convinced Eisenhower that toll roads were not feasible outside of the highly populated coastal regions. In February 1955, Eisenhower forwarded Clay's proposal to Congress. The bill quickly won approval in the Senate, but House Democrats objected to the use of public bonds as the means to finance construction. Eisenhower and the House Democrats agreed to instead finance the system through the Highway Trust Fund, which itself would be funded by a gasoline tax. In June 1956, Eisenhower signed the Federal Aid Highway Act of 1956 into law. Under the act, the federal government would pay for 90 percent of the cost of construction of Interstate Highways. Each Interstate Highway was required to be a controlled-access highway with at least four lanes and no at-grade crossings.
The publication in 1955 of the General Location of National System of Interstate Highways, informally known as the Yellow Book, mapped out what became the Interstate Highway System.Assisting in the planning was Charles Erwin Wilson, who was still head of General Motors when President Eisenhower selected him as Secretary of Defense in January 1953.
Some sections of highways that became part of the Interstate Highway System actually began construction earlier.
Three states have claimed the title of first Interstate Highway. Missouri claims that the first three contracts under the new program were signed in Missouri on August 2, 1956. The first contract signed was for upgrading a section of US Route 66 to what is now designated Interstate 44.On August 13, 1956, work began on US 40 (now I-70) in St. Charles County.
Kansas claims that it was the first to start paving after the act was signed. Preliminary construction had taken place before the act was signed, and paving started September 26, 1956. The state marked its portion of I-70 as the first project in the United States completed under the provisions of the new Federal-Aid Highway Act of 1956.
The Pennsylvania Turnpike could also be considered one of the first Interstate Highways, and is nicknamed "Grandfather of the Interstate System". 162 miles (261 km) of the highway now designated I‑70 and I‑76 opened between Irwin and Carlisle. The Commonwealth of Pennsylvania refers to the turnpike as the Granddaddy of the Pikes (referring to turnpikes).On October 1, 1940,
Milestones in the construction of the Interstate Highway System include:
The initial cost estimate for the system was $25 billion over 12 years; it ended up costing $114 billion (equivalent to $425 billion in 2006 or $521 billion in 2018 ) and took 35 years.
The system was proclaimed complete in 1992, but two of the original Interstates—I-95 and I-70—were not continuous: both of these discontinuities were due to local opposition, which blocked efforts to build the necessary connections to fully complete the system. I-95 was made a continuous freeway in 2018,and thus I-70 remains the only original Interstate with a discontinuity.
I-95 was discontinuous in New Jersey because of the cancellation of the Somerset Freeway. This situation was remedied when the construction of the Pennsylvania Turnpike/Interstate 95 Interchange Project started in 2010and partially opened on September 22, 2018, which was already enough to fill the gap.
However, I-70 remains discontinuous in Pennsylvania, because of the lack of a direct interchange with the Pennsylvania Turnpike at the eastern end of the concurrency near Breezewood. Traveling in either direction, I-70 traffic must exit the freeway and use a short stretch of US-30 (which includes a number of roadside services) to rejoin I-70. The interchange was not originally built because of a legacy federal funding rule, since relaxed, which restricted the use of federal funds to improve roads financed with tolls.Solutions have been proposed to eliminate the discontinuity, but they have been blocked by local opposition, fearing a loss of business.
The Interstate Highway System has been expanded numerous times. The expansions have both created new designations and extended existing designations. For example, I-49, added to the system in the 1980s as a freeway in Louisiana, was designated as an expansion corridor, and FHWA approved the expanded route north from Lafayette, Louisiana, to Kansas City, Missouri. The freeway exists today as separate completed segments, with segments under construction or in the planning phase between them.
In 1966, the FHWA designated the entire Interstate Highway System as part of the larger Pan-American Highway System,and at least two proposed Interstate expansions were initiated to help trade with Canada and Mexico spurred by the North American Free Trade Agreement (NAFTA). Long-term plans for I-69, which currently exists in several separate completed segments (the largest of which are in Indiana and Texas), is to have the highway route extend from Tamaulipas, Mexico to Ontario, Canada. The planned I-11 will then bridge the Interstate gap between Phoenix, Arizona and Las Vegas, Nevada, and thus form part of the CANAMEX Corridor (along with I-19, and portions of I-10 and I-15) between Sonora, Mexico and Alberta, Canada.
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Political opposition from residents canceled many freeway projects around the United States, including:
The American Association of State Highway and Transportation Officials (AASHTO) has defined a set of standards that all new Interstates must meet unless a waiver from the Federal Highway Administration (FHWA) is obtained. One almost absolute standard is the controlled access nature of the roads. With few exceptions, traffic lights (and cross traffic in general) are limited to toll booths and ramp meters (metered flow control for lane merging during rush hour).
Being freeways, Interstate Highways usually have the highest speed limits in a given area. Speed limits are determined by individual states. From 1974 to 1986, the maximum speed limit on any highway in the United States was 55 miles per hour (90 km/h), in accordance with federal law.
Typically, lower limits are established in Northeastern and coastal states, while higher speed limits are established in inland states west of the Mississippi River. 75 mph (120 km/h) in northern Maine, varies between 50 and 70 mph (80 and 115 km/h) from southern Maine to New Jersey, and is 50 mph (80 km/h) in New York City and the District of Columbia. Currently, rural speed limits elsewhere generally range from 65 to 80 miles per hour (105 to 130 km/h). Several portions of various highways such as I-10 and I-20 in rural western Texas, I-80 in Nevada between Fernley and Winnemucca (except around Lovelock) and portions of I-15, I-70, I-80, and I-84 in Utah have a speed limit of 80 mph (130 km/h). Other Interstates in Idaho, Montana, South Dakota and Wyoming also have the same high speed limits.For example, the maximum speed limit is
In some areas, speed limits on Interstates can be significantly lower in areas where they traverse significantly hazardous areas. The maximum speed limit on I-90 is 50 mph (80 km/h) in downtown Cleveland because of two sharp curves with a suggested limit of 35 mph (55 km/h) in a heavily congested area; I-70 through Wheeling, West Virginia, has a maximum speed limit of 45 mph (70 km/h) through the Wheeling Tunnel and most of downtown Wheeling; and I-68 has a maximum speed limit of 40 mph (65 km/h) through Cumberland, Maryland, because of multiple hazards including sharp curves and narrow lanes through the city. In some locations, low speed limits are the result of lawsuits and resident demands; after holding up the completion of I-35E in St. Paul, Minnesota, for nearly 30 years in the courts, residents along the stretch of the freeway from the southern city limit to downtown successfully lobbied for a 45 mph (70 km/h) speed limit in addition to a prohibition on any vehicle weighing more than 9,000 pounds (4,100 kg) gross vehicle weight. I-93 in Franconia Notch State Park in northern New Hampshire has a speed limit of 45 mph (70 km/h) because it is a parkway that consists of only one lane per side of the highway. On the other hand, Interstates 15, 80 and 84 in Utah have speed limits as high as 70 mph (115 km/h) within the Salt Lake City, Cedar City, and St. George areas, and I-25 in New Mexico within the Santa Fe and Las Vegas areas along with I-20 in Texas along Odessa and Midland and I-29 in North Dakota along the Grand Forks area have higher speed limits of 75 mph (120 km/h).
As one of the components of the National Highway System, Interstate Highways improve the mobility of military troops to and from airports, seaports, rail terminals, and other military bases. Interstate Highways also connect to other roads that are a part of the Strategic Highway Network, a system of roads identified as critical to the U.S. Department of Defense.
The system has also been used to facilitate evacuations in the face of hurricanes and other natural disasters. An option for maximizing traffic throughput on a highway is to reverse the flow of traffic on one side of a divider so that all lanes become outbound lanes. This procedure, known as contraflow lane reversal, has been employed several times for hurricane evacuations. After public outcry regarding the inefficiency of evacuating from southern Louisiana prior to Hurricane Georges' landfall in September 1998, government officials looked towards contraflow to improve evacuation times. In Savannah, Georgia, and Charleston, South Carolina, in 1999, lanes of I-16 and I-26 were used in a contraflow configuration in anticipation of Hurricane Floyd with mixed results.
In 2004 contraflow was employed ahead of Hurricane Charley in the Tampa, Florida area and on the Gulf Coast before the landfall of Hurricane Ivan;however, evacuation times there were no better than previous evacuation operations. Engineers began to apply lessons learned from the analysis of prior contraflow operations, including limiting exits, removing troopers (to keep traffic flowing instead of having drivers stop for directions), and improving the dissemination of public information. As a result, the 2005 evacuation of New Orleans, Louisiana, prior to Hurricane Katrina ran much more smoothly.
According to urban legend, early regulations required that one out of every five miles of the Interstate Highway System must be built straight and flat, so as to be usable by aircraft during times of war. There is no evidence of this rule being included in any Interstate legislation.
The numbering scheme for the Interstate Highway System was developed in 1957 by the American Association of State Highway and Transportation Officials (AASHTO). The association's present numbering policy dates back to August 10, 1973.Within the contiguous United States, primary Interstates—also called main line Interstates or two-digit Interstates—are assigned numbers less than 100.
While numerous exceptions do exist, there is a general scheme for numbering Interstates. Primary Interstates are assigned one- or two-digit numbers, while shorter routes (such as spurs, loops, and short connecting roads) are assigned three-digit numbers where the last two digits match the parent route (thus, I-294 is a loop that connects at both ends to I-94, while I-787 is a short spur route attached to I-87). In the numbering scheme for the primary routes, east–west highways are assigned even numbers and north–south highways are assigned odd numbers. Odd route numbers increase from west to east, and even-numbered routes increase from south to north (to avoid confusion with the U.S. Highways, which increase from east to west and north to south).This numbering system usually holds true even if the local direction of the route does not match the compass directions. Numbers divisible by five are intended to be major arteries among the primary routes, carrying traffic long distances. Primary north–south Interstates increase in number from I-5 between Canada and Mexico along the West Coast to I‑95 between Canada and Miami, Florida along the East Coast. Major west–east arterial Interstates increase in number from I-10 between Santa Monica, California, and Jacksonville, Florida, to I-90 between Seattle, Washington, and Boston, Massachusetts, with two exceptions. There are no I-50 and I-60, as routes with those numbers would likely pass through states that currently have U.S. Highways with the same numbers, which is generally disallowed under highway administration guidelines.
Several two-digit numbers are shared between road segments at opposite ends of the country for various reasons. Some such highways are incomplete Interstates (such as I-69 and I-74) and some just happen to share route designations (such as I-76, I-84, I‑86, I-87, and I-88). Some of these were due to a change in the numbering system as a result of a new policy adopted in 1973. Previously, letter-suffixed numbers were used for long spurs off primary routes; for example, western I‑84 was I‑80N, as it went north from I‑80. The new policy stated, "No new divided numbers (such as I-35W and I-35E, etc.) shall be adopted." The new policy also recommended that existing divided numbers be eliminated as quickly as possible; however, an I-35W and I-35E still exist in the Dallas–Fort Worth metroplex in Texas, and an I-35W and I-35E that run through Minneapolis and Saint Paul, Minnesota, still exist.Additionally, due to Congressional requirements, three sections of I-69 in southern Texas will be divided into I-69W, I-69E, and I-69C (for Central).
AASHTO policy allows dual numbering to provide continuity between major control points. 7.4-mile (11.9 km) section, called the Downtown Connector, is labeled both I‑75 and I‑85. Concurrencies between Interstate and U.S. Route numbers are also allowed in accordance with AASHTO policy, as long as the length of the concurrency is reasonable. In rare instances, two highway designations sharing the same roadway are signed as traveling in opposite directions; one such wrong-way concurrency is found between Wytheville and Fort Chiswell, Virginia, where I‑81 north and I‑77 south are equivalent (with that section of road traveling almost due east), as are I‑81 south and I‑77 north.This is referred to as a concurrency or overlap. For example, I‑75 and I‑85 share the same roadway in Atlanta; this
Auxiliary Interstate Highways are circumferential, radial, or spur highways that principally serve urban areas. These types of Interstate Highways are given three-digit route numbers, which consist of a single digit prefixed to the two-digit number of its parent Interstate Highway. Spur routes deviate from their parent and do not return; these are given an odd first digit. Circumferential and radial loop routes return to the parent, and are given an even first digit. Unlike primary Interstates, three-digit Interstates are signed as either east–west or north–south, depending on the general orientation of the route, without regard to the route number. For instance, I-190 in Massachusetts is labeled north–south, while I-195 in New Jersey is labeled east–west. Some looped Interstate routes use inner–outer directions instead of compass directions, when the use of compass directions would create ambiguity. Due to the large number of these routes, auxiliary route numbers may be repeated in different states along the mainline.Some auxiliary highways do not follow these guidelines, however.
The Interstate Highway System also extends to Alaska, Hawaii, and Puerto Rico, even though they have no direct land connections to any other states or territories. However, their residents still pay federal fuel and tire taxes.
The Interstates in Hawaii, all located on the most populous island of Oahu, carry the prefix H. There are three one-digit routes in the state (H-1, H-2, and H-3) and one auxiliary route (H-201). These Interstates connect several military and naval bases together, as well as the important cities and towns spread across Oahu, and especially the metropolis of Honolulu.
Both Alaska and Puerto Rico also have public highways that receive 90 percent of their funding from the Interstate Highway program. The Interstates of Alaska and Puerto Rico are numbered sequentially in order of funding without regard to the rules on odd and even numbers. They also carry the prefixes A and PR, respectively. However, these highways are signed according to their local designations, not their Interstate Highway numbers. Furthermore, these routes were neither planned according to nor constructed to the official Interstate Highway standards.
On one- or two-digit Interstates, the mile marker numbering almost always begins at the southern or western state line. If an Interstate originates within a state, the numbering begins from the location where the road begins in the south or west. As with all guidelines for Interstate routes, however, numerous exceptions exist.
Three-digit Interstates with an even first number that form a complete circumferential (circle) bypass around a city feature mile markers that are numbered in a clockwise direction, beginning just west of an Interstate that bisects the circumferential route near a south polar location. In other words, mile marker 1 on I-465, a 53-mile (85 km) route around Indianapolis, is just west of its junction with I-65 on the south side of Indianapolis (on the south leg of I-465), and mile marker 53 is just east of this same junction. An exception is I-495 in the Washington metropolitan area, with mileposts increasing counterclockwise because part of that road is also part of I-95.
The exit numbers of interchanges are either sequential or distance-based so that the exit number is the same as the nearest mile marker. Under the latter system, a single mile with multiple exits may be assigned letter suffixes, for example on I‑890 in New York.
AASHTO defines a category of special routes separate from primary and auxiliary Interstate designations. These routes do not have to comply to Interstate construction or limited-access standards but are routes that may be identified and approved by the association. The same route marking policy applies to both US Numbered Highways and Interstate Highways; however, business route designations are sometimes used for Interstate Highways.Known as Business Loops and Business Spurs, these routes principally travel through the corporate limits of a city, passing through the central business district when the regular route is directed around the city. They also use a green shield instead of the red and blue shield.
Interstate Highways and their rights-of-way are owned by the state in which they were built. The last federally owned portion of the Interstate System was the Woodrow Wilson Bridge on the Washington Capital Beltway. The new bridge was completed in 2009 and is collectively owned by Virginia and Maryland.Maintenance is generally the responsibility of the state department of transportation. However, there are some segments of Interstate owned and maintained by local authorities.
About 70 percent of the construction and maintenance costs of Interstate Highways in the United States have been paid through user fees, primarily the fuel taxes collected by the federal, state, and local governments. To a much lesser extent they have been paid for by tolls collected on toll highways and bridges. The federal gasoline tax was first imposed in 1932 at one cent per gallon; during the Eisenhower administration, the Highway Trust Fund, established by the Highway Revenue Act in 1956, prescribed a three-cent-per-gallon fuel tax, soon increased to 4.5 cents per gallon. Since 1993 the tax has remained at 18.4 cents per gallon. Other excise taxes related to highway travel also accumulated in the Highway Trust Fund. Initially, that fund was sufficient for the federal portion of building the Interstate system, built in the early years with "10 cent dollars", from the perspective of the states, as the federal government paid 90% of the costs while the state paid 10%. The system grew more rapidly than the rate of the taxes on fuel and other aspects of driving (e. g., excise tax on tires).
The rest of the costs of these highways are borne by general fund receipts, bond issues, designated property taxes, and other taxes. The federal contribution comes overwhelmingly from motor vehicle and fuel taxes (93.5 percent in 2007), as does about 60 percent of the state contribution. However, any local government contributions are overwhelmingly from sources besides user fees. As decades passed in the 20th century and into the 21st century, the portion of the user fees spent on highways themselves covers about 57 percent of their costs, with about one-sixth of the user fees being sent to other programs, including the mass transit systems in large cities. Some large sections of Interstate Highways that were planned or constructed before 1956 are still operated as toll roads. Others have had their construction bonds paid off and they have become toll-free, such as in Connecticut (I‑95), Maryland (I‑95), Virginia (I‑95), and Kentucky (I‑65).
As American suburbs have expanded, the costs incurred in maintaining freeway infrastructure have also grown, leaving little in the way of funds for new Interstate construction.This has led to the proliferation of toll roads (turnpikes) as the new method of building limited-access highways in suburban areas. Some Interstates are privately maintained (for example, the VMS company maintains I‑35 in Texas) to meet rising costs of maintenance and allow state departments of transportation to focus on serving the fastest-growing regions in their states.
Parts of the Interstate System might have to be tolled in the future to meet maintenance and expansion demands, as has been done with adding toll HOV/HOT lanes in cities such as Atlanta, Dallas, and Los Angeles. Although part of the tolling is an effect of the SAFETEA‑LU act, which has put an emphasis on toll roads as a means to reduce congestion, [ citation needed ]present federal law does not allow for a state to change a freeway section to a tolled section for all traffic.
About 2,900 miles (4,700 km) of toll roads are included in the Interstate Highway System. While federal legislation initially banned the collection of tolls on Interstates, many of the toll roads on the system were either completed or under construction when the Interstate Highway System was established. Since these highways provided logical connections to other parts of the system, they were designated as Interstate highways. Congress also decided that it was too costly to either build toll-free Interstates parallel to these toll roads, or directly repay all the bondholders who financed these facilities and remove the tolls. Thus, these toll roads were grandfathered into the Interstate Highway System.
Toll roads designated as Interstates (such as the Massachusetts Turnpike) were typically allowed to continue collecting tolls, but are generally ineligible to receive federal funds for maintenance and improvements. Some toll roads that did receive federal funds to finance emergency repairs (notably the Connecticut Turnpike (I-95) following the Mianus River Bridge collapse) were required to remove tolls as soon as the highway's construction bonds were paid off. In addition, these toll facilities were grandfathered from Interstate Highway standards. A notable example is the western approach to the Benjamin Franklin Bridge in Philadelphia, where I-676 has a surface street section through a historic area.
Policies on toll facilities and Interstate Highways have since changed. The Federal Highway Administration has allowed some states to collect tolls on existing Interstate Highways, while a recent extension of I-376 included a section of Pennsylvania Route 60 that was tolled by the Pennsylvania Turnpike Commission before receiving Interstate designation. Also, newer toll facilities (like the tolled section of I-376, which was built in the early 1990s) must conform to Interstate standards. A new addition of the Manual on Uniform Traffic Control Devices in 2009 requires a black-on-yellow "Toll" sign to be placed above the Interstate trailblazer on Interstate Highways that collect tolls.
Legislation passed in 2005 known as SAFETEA-LU, encouraged states to construct new Interstate Highways through "innovative financing" methods. SAFETEA-LU facilitated states to pursue innovative financing by easing the restrictions on building interstates as toll roads, either through state agencies or through public–private partnerships. However, SAFETEA-LU left in place a prohibition of installing tolls on existing toll-free Interstates, and states wishing to toll such routes to finance upgrades and repairs must first seek approval from Congress.
Interstate Highways financed with federal funds are known as "chargeable" Interstate routes, and are considered part of the 42,000-mile (68,000 km) network of highways. Federal laws also allow "non-chargeable" Interstate routes, highways funded similarly to state and U.S. Highways to be signed as Interstates, if they both meet the Interstate Highway standards and are logical additions or connections to the system. These additions fall under two categories: routes that already meet Interstate standards, and routes not yet upgraded to Interstate standards. Only routes that meet Interstate standards may be signed as Interstates once their proposed number is approved.
Interstate Highways are signed by a number placed on a red, white, and blue sign. The shield design itself is a registered trademark of the American Association of State Highway and Transportation Officials. 36 inches (91 cm) high, and is 36 inches (91 cm) wide for two-digit Interstates or 45 inches (110 cm) for three-digit Interstates.The colors red, white, and blue were chosen because they are the colors of the American flag. In the original design, the name of the state was displayed above the highway number, but in many states, this area is now left blank, allowing for the printing of larger and more-legible digits. Signs with the shield alone are placed periodically throughout each Interstate as reassurance markers. These signs usually measure
Interstate business loops and spurs use a special shield in which the red and blue are replaced with green, the word "BUSINESS" appears instead of "INTERSTATE", and the word "SPUR" or "LOOP" usually appears above the number.The green shield is employed to mark the main route through a city's central business district, which intersects the associated Interstate at one (spur) or both (loop) ends of the business route. The route usually traverses the main thoroughfare(s) of the city's downtown area or other major business district. A city may have more than one Interstate-derived business route, depending on the number of Interstates passing through a city and the number of significant business districts therein.
Over time, the design of the Interstate shield has changed. In 1957 the Interstate shield designed by Texas Highway Department employee Richard Oliver was introduced, the winner of a contest that included 100 entries; at the time, the shield color was a dark navy blue and only 17 inches (43 cm) wide. The Manual on Uniform Traffic Control Devices (MUTCD) standards revised the shield in the 1961, 1971, and 1978 editions.
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The majority of Interstates have exit numbers. Like other highways, Interstates feature guide signs that list control cities to help direct drivers through interchanges and exits toward their desired destination. All traffic signs and lane markings on the Interstates are supposed to be designed in compliance with the Manual on Uniform Traffic Control Devices (MUTCD). There are, however, many local and regional variations in signage.
For many years, California was the only state that did not use an exit numbering system. It was granted an exemption in the 1950s due to having an already largely completed and signed highway system; placing exit number signage across the state was deemed too expensive. To control costs, California began to incorporate exit numbers on its freeways in 2002—Interstate, U.S., and state routes alike. Caltrans commonly installs exit number signage only when a freeway or interchange is built, reconstructed, retrofitted, or repaired, and it is usually tacked onto the top-right corner of an already existing sign. Newer signs along the freeways follow this practice as well. Most exits along California's Interstates now have exit number signage, particularly in rural areas. California, however, still does not use mileposts, although a few exist for experiments or for special purposes. [ self-published source ] In 2010–2011, the Illinois State Toll Highway Authority posted all new mile markers to be uniform with the rest of the state on I‑90 (Jane Addams Memorial/Northwest Tollway) and the I‑94 section of the Tri‑State Tollway, which previously had matched the I‑294 section starting in the south at I‑80/I‑94/IL Route 394. The tollway also added exit number tabs to the exits.[ citation needed ]
Exit numbers correspond to Interstate mileage markers in most states. On I‑19 in Arizona, however, length is measured in kilometers instead of miles because, at the time of construction, a push for the United States to change to a metric system of measurement had gained enough traction that it was mistakenly assumed that all highway measurements would eventually be changed to metric;proximity to metric-using Mexico may also have been a factor, as I‑19 indirectly connects I‑10 to the Mexican Federal Highway system via surface streets in Nogales. Mileage count increases from west to east on most even-numbered Interstates; on odd-numbered Interstates mileage count increases from south to north.
Some highways, including the New York State Thruway, use sequential exit-numbering schemes. Exits on the New York State Thruway count up from Yonkers traveling north, and then west from Albany. I‑87 in New York State is numbered in three sections. The first section makes up the Major Deegan Expressway in the Bronx, with interchanges numbered sequentially from 1 to 14. The second section of I‑87 is a part of the New York State Thruway that starts in Yonkers (exit 1) and continues north to Albany (exit 24); at Albany, the Thruway turns west and becomes I‑90 for exits 25 to 61. From Albany north to the Canadian border, the exits on I‑87 are numbered sequentially from 1 to 44 along the Adirondack Northway. This often leads to confusion as there is more than one exit on I‑87 with the same number. For example, exit 4 on Thruway section of I‑87 connects with the Cross County Parkway in Yonkers, but exit 4 on the Northway is the exit for the Albany airport. These two exits share a number but are located 150 miles (240 km) apart.
Many northeastern states label exit numbers sequentially, regardless of how many miles have passed between exits. States in which Interstate exits are still numbered sequentially are Connecticut, Delaware, Massachusetts, New Hampshire, New York, Rhode Island, and Vermont; as such, five of the main Interstate Highways that remain completely within these states (87, 88, 89, 91, and 93) have interchanges numbered sequentially along their entire routes. Maine, Pennsylvania, Virginia, Georgia, and Florida followed this system for a number of years, but have since converted to mileage-based exit numbers. Georgia renumbered in 2000, while Maine did so in 2004. The Pennsylvania Turnpike uses both mile marker numbers and sequential numbers. Mile marker numbers are used for signage, while sequential numbers are used for numbering interchanges internally. The New Jersey Turnpike, including the portions that are signed as I‑95 and I‑78, also has sequential numbering, but other Interstates within New Jersey use mile markers.
There are four common signage methods on Interstates:
Following the passage of the Federal Aid Highway Act of 1956, the railroad system for passengers and freight declined sharply, but the trucking industry expanded dramatically and the cost of shipping and travel fell sharply. Suburbanization became possible, with the rapid growth of easily accessible, larger, cheaper housing than was available in central cities. Tourism dramatically expanded as well, creating a demand for more service stations, motels, restaurants and visitor attractions. There was much more long-distance movement to the Sun Belt for winter vacations, or for permanent relocation, with convenient access to visits to relatives back home. In rural areas, towns and small cities off the grid lost out as shoppers followed the interstate and new factories were located near them.
The system had a particularly strong effect in the Southern United States, as most Southern states had not previously been able to afford the construction of major highways. The construction of the Interstate Highway System facilitated the relocation of heavy manufacturing to the South and spurred the development of Southern-based corporations like Walmart and FedEx.
The Interstate Highway System has been criticized for contributing to the decline of some cities and for destroying predominantly African-American neighborhoods in urban centers.Other critics have blamed the Interstate Highway System for the decline of public transportation in the United States since the 1950s.
The United States Numbered Highway System is an integrated network of roads and highways numbered within a nationwide grid in the contiguous United States. As the designation and numbering of these highways were coordinated among the states, they are sometimes called Federal Highways, but the roadways were built and have always been maintained by state or local governments since their initial designation in 1926.
Interstate 238 (I-238) is an auxiliary Interstate Highway in the San Francisco Bay Area in the U.S. state of California. It comprises the northernmost 2.126 miles (3.421 km) of Route 238, as defined by the California Streets and Highways Code. Originally signed as State Route 238 (SR 238) until 1983, it connects I-580 in Castro Valley with I-880 in San Leandro.
Interstate 70 (I-70) is a major east–west Interstate Highway in the United States that runs from I-15 near Cove Fort, Utah, to a Park and Ride lot just east of I-695 in Baltimore, Maryland. I-70 approximately traces the path of U.S. Route 40 east of the Rocky Mountains. West of the Rockies, the route of I-70 was derived from multiple sources. The Interstate runs through or near many major cities, including Denver, Kansas City, St. Louis, Indianapolis, Columbus, Pittsburgh, and Baltimore. The sections of the interstate in Missouri and Kansas have laid claim to be the first interstate in the United States. The Federal Highway Administration has claimed the section of I-70 through Glenwood Canyon, Colorado, completed in 1992, was the last piece of the Interstate Highway system, as originally planned, to open to traffic. The construction of I-70 in Colorado and Utah is considered an engineering marvel, as the route passes through the Eisenhower Tunnel, Glenwood Canyon, and the San Rafael Swell. The Eisenhower Tunnel is the highest point along the Interstate Highway system, with an elevation of 11,158 ft (3,401 m).
Interstate 535 (I-535) is a 2.78-mile-long (4.47 km) Auxiliary Interstate Highway spur route of I-35 in the U.S. states of Minnesota and Wisconsin. It is paired with U.S. Route 53 (US 53) along its entire route.
State Route 237 is a state highway in the U.S. state of California that runs from El Camino Real in Mountain View to Interstate 680 in Milpitas. Known as the Southbay Freeway for most of its length, SR 237 runs south of the San Francisco Bay, connecting the East Bay to the Peninsula.
Interstate H-201 (H-201) is the only auxiliary Interstate Highway located in the U.S. state of Hawaii, serving the island of O‘ahu. The H-201 designation is also known as the Moanalua Freeway. The 4.1-mile-long (6.6 km) loop route connects exits 13 and 19 on H-1, passing Fort Shafter, Tripler Army Medical Center, and Red Hill.
A concurrency in a road network is an instance of one physical roadway bearing two or more different route numbers. When two roadways share the same right-of-way, it is sometimes called a common section or commons. Other terminology for a concurrency includes overlap, coincidence, duplex, triplex, multiplex, dual routing or triple routing.
Interstate 84 (I-84) is an Interstate Highway in the northeastern United States that extends from Dunmore, Pennsylvania, at an interchange with I-81 east to Sturbridge, Massachusetts, at an interchange with the Massachusetts Turnpike (I-90). Among the major cities that the road passes through is Hartford, Connecticut. Another highway named I-84 is located in the northwestern United States.
The Falmouth Spur is a short freeway connecting Interstate 95 (I-95) with I-295 and U.S. Route 1 (US 1) north of Portland, Maine, in the United States. It carries the unsigned designation of I-495. As part of the Maine Turnpike, the mainline of which carries I-95, the Falmouth Spur is a toll road. The spur has only two interchanges—one at each end—and a toll booth in the middle. It is signed only for its destinations—I-95, I-295 and US 1—to minimize driver confusion.
Interstate 540 (I-540) and North Carolina Highway 540 (NC 540) are part of a partially completed beltway around the city of Raleigh in the U.S. state of North Carolina forming the Raleigh Outer Loop. When complete, the route will completely encircle the city, meeting its parent route of Interstate 40 in one location.
The Massachusetts State Highway System in the U.S. state of Massachusetts is a system of state-numbered routes assigned and marked by the highway division of the Massachusetts Department of Transportation (MassDOT). U.S. Highways and Interstate Highways are included in the system; the only overlaps are with the end-to-end U.S. Route 3 and Route 3 and the far-apart Interstate 295, shared with Rhode Island, and Route 295, shared with New York State. A state highway in Massachusetts is a road maintained by the state, which may or may not have a number. Not all numbered routes are maintained or owned by the state.
Interstate 85 (I-85) is a major Interstate Highway that travels northeast-to-southwest in the U.S. state of Georgia. It enters the state at the Alabama state line near West Point, and Lanett, Alabama, traveling through the Atlanta metropolitan area and to the South Carolina state line, where it crosses the Savannah River near Lake Hartwell. I-85 connects northern Georgia with Montgomery, Alabama, to the southwest, and with South Carolina, North Carolina, and Virginia to the northeast. Within Georgia, I-85 is also designated as the unsigned State Route 403 (SR 403).
Interstate 90 (I-90) is a part of the Interstate Highway System that runs from Seattle, Washington, to Boston, Massachusetts. In the U.S. state of New York, I-90 extends 385.88 miles (621.01 km) from the Pennsylvania state line at Ripley to the Massachusetts state line at Canaan, and is the second-longest highway in the state after NY 17. Although most of the route is part of the tolled New York State Thruway, two non-tolled sections exist along I-90. Within New York, I-90 has a complete set of auxiliary Interstates, which means that there are interstates numbered I-190 through I-990 in the state, with no gaps in between. For most of its length in New York, I-90 runs parallel to the former Erie Canal route, New York State Route 5 (NY 5), U.S. Route 20 (US 20) and the CSX railroad mainline that traverses the state.
Interstate 70 (I-70) is a transcontinental Interstate Highway in the United States, stretching from Cove Fort, Utah, to Baltimore, Maryland. In Colorado, the highway traverses an east–west route across the center of the state. In western Colorado, the highway connects the metropolitan areas of Grand Junction and Denver via a route through the Rocky Mountains. In eastern Colorado, the highway crosses the Great Plains, connecting Denver with metropolitan areas in Kansas and Missouri. Bicycles and other non-motorized vehicles, normally prohibited on Interstate Highways, are allowed on those stretches of I-70 in the Rockies where no other through route exists.
In the U.S. state of Kansas, Interstate 70 (I-70) contains the first segment to start being paved and to be completed in the Interstate Highway System. It extends from the Colorado border near the town of Kanorado to the Missouri border in Kansas City. The route covers 424 miles (682 km) and passes through several of the state's principal cities in the process including Kansas City, Topeka, and Salina. The route also passes through the cities of Lawrence, Junction City, and Abilene.
In the United States, exit numbers are assigned to freeway junctions, and are usually numbered as exits from freeways. Exit numbers generally are found above the destinations of the exit, as well as a sign in the gore. Exit numbers typically reset at political borders such as state lines. Some major streets also use exit numbers. Freeway exits in the United States are usually numbered in two formats: distance-based and sequential.
The Delaware State Route System consists of roads in the U.S. state of Delaware that are maintained by the Delaware Department of Transportation (DelDOT). The system includes the portions of the Interstate Highway System and United States Numbered Highways system located in the state along with state routes and other roads maintained by DelDOT. All roads maintained by the state are assigned a maintenance road number that is only marked on little white markers at intersections and on auxiliary plates below warning signs approaching intersections. These numbers are only unique in a specific county, some roads can be designated with multiple road numbers, and numbers do not necessarily correspond to the signed Interstate, U.S., or state route numbers. DelDOT maintains a total of 5,386.14 miles (8,668.15 km) of roads, comprising 89 percent of the roads within the state. Some large bridges in the state are maintained by other agencies including the U.S. Army Corps of Engineers and the Delaware River and Bay Authority. Roads in the system include multilane freeways, multilane surface divided highways, and two-lane undivided roads serving urban, suburban, and rural areas. Some of the roads maintained by DelDOT are toll roads, in which motorists must pay to use.
Proposed I-41 in Wisconsin and partly completed I-74 in North Carolina respectively are possible and current exceptions not adhering to the guideline. It is not known if the U.S. Highways with the same numbers will be retained in the states upon completion of the Interstate routes.
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