Interstate Highway System

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The Dwight D. Eisenhower National System of Interstate and Defense Highways, commonly called the Interstate Highway System, is a network of highways in the United States. The Interstate Highway System is a separate system within the larger National Highway System. With few exceptions, Interstate highways are controlled-access freeways that allow for safe high-speed driving.

Interstate highways are assigned a special level of federal funding, but they are owned, designed, built and maintained by the state in which they are located. The only exception is the federally-owned Woodrow Wilson Bridge on the Capital Beltway (I-95/I-495).

Image:Interstate Highways.png Image:Interstate5incentralvalley.jpg The highways in the system are typically known as Interstate XX or I-XX; sometimes Interstate Highway XX (IH XX) or Interstate Route XX (IR XX) is used. In some areas, the more generic Route XX or Highway XX is used.

The system serves all major U.S. cities. Unlike counterparts in most industrialized countries, Interstates go through downtown areas. This facilitated the emergence of automobile-oriented postwar suburban development patterns, a phenomenon pejoratively named "urban sprawl."

The system is prominent in American daily life. The distribution of virtually all goods and services involve Interstate Highways at some point. Residents of American cities commonly use urban Interstates to travel to employment. Most long-distance journeys of less than 300 miles (500 km), whether for vacation or business, use the interstate highway system at some point.

Alaska and Puerto Rico have roads designated as Interstates for funding purposes but which are neither planned for or currently built to Interstate standards. The public controlled-access highways of Puerto Rico are the Autopistas (PR-22, PR-52, and PR-53).

History

Image:Eisenhower Interstate System.svg The interstate system was authorized by the Federal-Aid Highway Act of 1956, popularly known as the National Interstate and Defense Highways Act of 1956. It was lobbied for by major U.S. automobile manufacturers and championed by President Dwight D. Eisenhower, and was influenced by both his experiences as a young soldier crossing the country in 1919 following the route of the Lincoln Highway, and by his appreciation of the German autobahn network.

Planning for a system of new superhighways began in the late 1930s, even before federal commitment to build the Interstate highway system came in the 1950s. Construction on the world's first public limited-access highway, the Bronx River Parkway, had begun in New York as early as 1907. By the 1920s, longer highways such as the New York City parkway system had been built as part of local or state highway systems. As automotive traffic increased, planners saw a need for such an interconnected national system to supplement the existing, largely non-freeway, United States Numbered Highway system. The General location of national system of interstate highways, including all additional routes at urban areas designated in September, 1955 maps what became the interstate system, and is informally known as the Yellow Book.

Although construction on the Interstate Highway system continues, it was officially regarded as complete in 1991 (though 1.5 miles of the original planned system remain unconstructed as of 2005 [1]). The initial cost estimate for the system was $25 billion over twelve years; it ended up costing $114 billion, taking 35 years to complete. As of 2004, the system contains over 42,700 miles (68,704 km) of roads, all at least four lanes wide.

The removal of the last traffic signal on Interstate 90 in Wallace, Idaho on September 15, 1991 is often cited as the completion of the Interstate System. However, due to the cancellation of the Somerset Freeway, Interstate 95 has not been completed in Pennsylvania and New Jersey; the Pennsylvania Turnpike/Interstate 95 Interchange Project will complete that route, the last section of the original (1947) plans to be completed (though a few routes, like Interstate 80 in central Ohio, have been majorly relocated). Several other routes have non-freeway sections (see list of gaps on Interstate Highways), but are considered to be complete.

Standards

Main article: Interstate Highway standards

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. These standards have become stricter over the years. 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 hours).

Speed limits

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Interstates generally have the highest speed limits of any road type. The highest rural speed limits are generally in western states, with 70 to 75 mph (112 km/h to 120 km/h) speed limits. The lowest rural speed limits are generally in northeastern states, with 60 to 65 mph (96 km/h to 104 km/h) speed limits. Urban interstate speed limits are generally 5 to 20 mph (8 km/h to 32 km/h) lower than rural limits.

Dual-purpose design

In addition to being designed to support automobile and heavy truck traffic, interstate highways are also designed for use in military and civil defense operations within the United States, particularly troop movements.

One potential civil defense use of the Interstate Highway System is for the emergency evacuation of cities in the event of a potential nuclear war. The Interstate Highway System has been used to facilitate evacuations in the face of hurricanes and other natural disasters. An option for maximizing throughput is to reverse the flow of traffic on one side so that all lanes become outbound lanes. This procedure is known as Contraflow, and could be seen in 2005 in the evacuations of New Orleans, Louisiana and Houston, Texas prior to hurricanes Katrina and Rita, respectively. Several Interstates in the South, including I-16 in Georgia, I-40 in North Carolina, I-65 in Alabama, I-10 & I-59 in Louisiana, and I-59 in Mississippi, are equipped and signed specifically for contraflow, with crossovers inland after major interchanges to distribute much of the traffic. This is however not limited to Interstates; US 49 from Gulfport to Jackson and State Road 528, in Central Florida, have the same setup.

"1 in 5" landing strip urban legend

A widespread urban legend states 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.[2] However, the Germans started using the Autobahn in World War II for just such a purpose. After the war, specific portions were custom-built and maintained throughout the Cold War. [3]

Terminology

While the name implies that these highways cross state lines, many Interstates do not. Rather, they are funded federally with money shared between the states. There are interstate highways in Hawaii, funded in the same way as in the other states, but entirely within the populous island of Oahu. They have the designation of H-X, and connect military bases. Similarly, both Alaska and Puerto Rico have public roads that receive funding from the Interstate program, though these routes are not signed as Interstate Highways.

Primary routes

The numbering scheme for the Interstate Highway System (as well as the U.S. Highway System) is coordinated by the American Association of State Highway and Transportation Officials (AASHTO), though their authority is occasionally trumped by a number written into Federal law. Within the continental United States, primary Interstates (also called main line Interstates or two-digit Interstates) are given one- or two-digit route numbers. Most Interstates have two numbers; there are only three one-digit Interstates in the system: I-4, I-5 and I-8. Within this category, 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. Numbers divisible by 5 are intended to be major among the primary routes, carrying traffic long distances. For example, I-5 runs from Canada to Mexico along the west coast (the only interstate to do so) while I-95 runs from Miami north to Canada. In addition, I-10 runs from Los Angeles, California to Jacksonville, Florida while I-90 runs from Seattle to Boston. However, not all primary routes divisible by 5 traverse long distances. I-45 runs from Galveston, Texas north to Dallas, Texas, a distance of only 284 miles. It is the only primary route divisible by 5 that does not cross state lines. See List of intrastate Interstate Highways for other primary routes that do not cross state lines.

It should be noted that I-50 and I-60 do not exist (and there are no even-numbered Interstates from 46 to 62), mainly because they would most likely have passed through the same states that already have US 50 and US 60. AASHTO rules discourage Interstate and US Highways with the same number to exist in the same state, although I-24 and US 24 exist at opposite ends of Illinois. Some planned Interstates do not follow this guideline - I-69 will intersect US 69 in Lufkin, Texas [4], I-74 will overlap US 74 in North Carolina, and I-41 will do the same with US 41 in Wisconsin.

Several two-digit numbers are shared between two roads at opposite ends of the country, namely I-76, I-84, I-86 and I-88. Some of these were the result of a change in the numbering system in the 1970s; 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. In the 1970s, AASHTO decided to eliminate these; some became additional two-digit routes, while others became three-digit routes (see below). Only two pairs of these exist; I-35 splits into I-35W and I-35E through both the Dallas-Fort Worth and the Minneapolis-St. Paul areas.

Strict adherence to the directional nature of the system results in some amusing oddities. For a ten-mile stretch east of Wytheville, Virginia, the driver can be traveling on both I-81 North and I-77 South at the same time (and vice versa) (see also Wrong-way concurrency).

For the sake of efficiency, some Interstates double up for short or sometimes long distances, as in the example above. Another notable example are Interstates I-90 and I-94, which double and then separate several times as they criss-cross the upper Midwest and Great Plains.

Three-digit Interstates

Three-digit route numbers, consisting of a single digit prefixed to the number of a primary Interstate highway, are used to designate usually short spur or loop routes from their "parent" route, either directly or via another three-digit Interstate. A route that spurs from its parent and ends at an intersection with no other Interstates is given an odd first digit; a route that returns to its parent is given an even first digit. The number given to the first digit of a route that spurs from the parent and ends at another Interstate depends on the state; some consider these routes spurs and give them odd numbers, while others consider them loop-style connectors and give them even numbers.

For instance, I-90 in New York has a full set of three-digit Interstates - I-190, I-290, I-390, I-490, I-590, I-690, I-790, I-890 and I-990. Due to the large number of these routes, they can be repeated in different places along the mainline; no two three-digit Interstates in the same state can share a number.

The Minneapolis-St. Paul area has a single loop around the entire Metro area. I-94 intersects the loop in two spots and runs directly through it separating it into a northern and southern half. The southern half of it is labeled I-494 while the northern half of it is labeled I-694.

Charlotte, North Carolina has a single loop around the city that intersects with both I-77 and I-85, but the entire loop is known as I-485. Similarly, Cincinnati, Ohio features a large loop around the city that intersects with I-71, I-74, I-75, and I-471. The entire 84-mile loop is labeled I-275. Houston has a loop, I-610 that intersects with both I-10 and I-45, as well as US 59, the future I-69.

The Baltimore-Washington metropolitan area has several spur routes off of I-95. The area has I-195, I-295, I-495, I-795 and I-895. It also has two routes numbered I-395 (in Baltimore and Washington) and two I-695s (one, the Baltimore Beltway, is signed, the other is a secret designation), as well as an unsigned route called I-595. No I-995 exists anywhere.

New York City has numerous spur routes off of I-78 and I-95, but none of I-78's spur routes actually intersect with I-78.

A three-digit spur off a letter-suffixed two-digit Interstate (see above) was given a number without a letter suffix, except for one case - I-184 in Idaho was I-180N.

Exceptions

Interstate 238 near Oakland, California is one of two major exceptions to the numbering scheme, as no Interstate 38 exists. This number exists because Interstate 238 replaced a segment of State Route 238, and no appropriate number was available. The other exception is Interstate 99 in Pennsylvania, which was written into law as I-99 by Pennsylvania Congressman Bud Shuster; I-99 (which is also U.S. Route 220) is west of several Interstates that are numerically less than 99, and was the nearest available unused two-digit number.

Some proposed future Interstate routes have been given similarly non-conforming designations by their legislative proponents. For example, backers of the proposed Third Infantry Division Highway, a route in Georgia and Tennessee, have suggested it be named Interstate 3, in honor of the division for which the highway is named.

Other notable examples

Interstate 82 lies fully north of Interstate 84, but I-84 was I-80N when I-82 got its number.

The following two-digit Interstates change signed direction from their normal (even=east-west, odd=north-south) direction:

Two-digit Interstates in Hawaii, as well as the "paper" Interstates of Alaska and Puerto Rico, are numbered sequentially in order of funding, without regard to the rules on odd and even numbers.

Business Loop and Business Spur Interstates are not subject to any of the Interstate standards. Their designation is simple - a Business Loop heads into a downtown area from its parent and returns to its parent; a Business Spur ends downtown, occasionally continuing from the end of the main Interstate. Business routes can split from either two- or three-digit Interstates, and can be repeated within a state. In a few cases, where an Interstate has been realigned, the old road has been designated a Business Loop because it is not up to standards.

Financing

About 56% (2003 FHWA summary) of the construction and maintenance costs are funded through user fees, primarily gasoline taxes, collected by states and the federal government, and tolls collected on toll roads and bridges. The rest of the costs come out of the federal budget. In the eastern United States, large sections of some Interstate Highways planned or built prior to 1956 are operated as toll roads. The taxes dedicated to the construction and maintenance of highways are often criticized as a direct subsidy from the government to promote and maintain auto-oriented development as we know it today.

As American suburbs push ever outward, the costs incurred of maintaining freeway infrastructure has started to catch up with the economy, leaving little in the way of funds for new interstate construction <ref>Field, David. "On 40th birthday, interstates face expensive midlife crisis." Insight on the News, 29 July 1996, 40-42.</ref>. This has led to the proliferation of the toll road (turnpike) as the new method of building limited-access highways in suburban areas. Also, some interstates are being privately maintained now (VMS in Texas, I-35) in order to cut rising costs of maintenance and allow state departments of transportation to focus on serving the fastest growing regions in their respective states. The future of the interstate system as we know it is in question. It is entirely possible that parts of the system will have to be tolled in the future to meet maintenance and expansion demands, as is done with adding toll HOV/HOT lanes in certain cities like San Diego, Minneapolis, Houston, Dallas, and Washington, D.C.

The federal role in financing

The dominant role of the federal government in road finance has enabled it to pass laws in areas outside of the powers enumerated in the federal Constitution. This has severely eroded states rights. By threatening to withhold highway funds, the federal government has been able to force state legislatures to pass a variety of laws. The first major example was the introduction of a maximum speed limit of 55 miles per hour (88km/h) . This was originally done to save fuel in the wake of the 1973 energy crisis, but stayed in force for more than two decades. The acceptance of the national speed limit emboldened various Presidents and Congress to enact several additional pieces of legislation, most of which have nothing to do with highways or transportaion. Examples include:

Increasing the legal drinking age to 21.

Passing Megan's Law legislation.

Lowering the legal intoxication level to 0.08%.

States must also meet minimum enforcement standards for all federally-mandated legislation (for example, minimum penalties for violation of these laws and a minimum number of per capita underage drinking convictions or a very compelling explanation regarding why this number is not met). This has proved to be controversial. Those who support this feel that it is a way to provide an impetus to states to pass uniform legislation. Others feel that using highway dollars in this fashion has upset the balance between federal and states rights in favor of the federal government, and effectively holds funds as ransom in order to coerce state governments into passing laws that would not have otherwised been introduced. Some have even argued that the current arrangement is unconstitutional. Law enforcement agencies in some states have bitterly complained that efforts to meet quotas for underage drinking convictions have distracted them from more pressing matters and needlessly strained relations with those under 21. Any state which were to lose federal highway funding would quickly face deteriorating infrastructure, fiscal impoverishment or both.

Of course, a state which lost federal highway funding could theoretically threaten to stop maintaining its highways, if that were politically palatable to its citizens.

Non-chargeable Interstate routes

In addition to Interstate highways financed with federal funds (Chargeable Interstate routes), federal laws allow other highways to be signed as Interstates, if they meet the Interstate Highway standards and are logical additions or connections to the System.

Called Non-Chargeable Interstate routes, these additions fall under two categories:

Routes that already meet Interstate standards. These may immediately be signed as Interstates once their proposed number is approved, or may be retained with a non-Interstate designation.
Routes not yet upgraded to Interstate standards. These cannot be signed as Interstates until they have been fully upgraded.

Signage

Interstate Highways are signed by a number on a red, white and blue sign as shown to the right. In the original design, the state was listed above the highway number, but in many states, this area is now left blank. The sign itself measures 36 inches high (91 cm) , and is 36 inches (91 cm) wide for two-digit interstates, or 45 inches (114 cm) for three-digit interstates.

Business Loop and Business Spur Interstates use a special shield where 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 majority of Interstates have exit numbers. 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). However, there are many local and regional variations in signage. The state of California is now adapting to an exit numbering system after many years as being the only state in the country that did not use such a system after being granted an exemption in the 1950's due to having an already largely completed and signed highway system. At the time placing exit signage on the signs across the state was deemed to be too expensive.

In most states, the exit numbers correspond to the mileage markers on the Interstates (with an exception being I-19 in Arizona, whose length is measured in kilometers instead of miles). Many northeastern states label exit numbers sequentially, regardless of how many miles have passed between exits. Maine, Georgia, Pennsylvania and Florida followed this system for a number of years, but recently converted to having the exit numbers correspond to mileage markers. On even-numbered Interstates, mileage increases to the east and decreases to the west (except on the I-90 portion of the New York State Thruway and the I-190 spur into O'Hare International Airport in Chicago, both of which count up going west); and on odd-numbered Interstates, mileage increases to the north and decreases to the south. In both cases, the exit numbers increase and decrease accordingly.

States still numbering sequentially are: Connecticut, Delaware, Massachusetts, New Hampshire, New York, Rhode Island and Vermont.

Trivia

Air rights: Structures built on top of Interstates

Several interstate highways have buildings over the highway, using air rights.

Vinita, Oklahoma — A McDonalds is built over the top of Interstate 44. It goes from one side of the interstate to the other, passing over the interstate. Customers can sit inside and eat while traffic drives beneath them. Aerial photo Photo: [5] from [6].

Kearney, Nebraska — The Great Platte River Road Archway Museum is built over the top of Interstate 80. The 1,500 ton structure spans 308 feet (93.87 meters) across the interstate and houses a museum dedicated to frontier culture. Photo: [7] from [8]

Reno, Nevada — A Walgreens store sits on top of a segment of Interstate 80 in downtown Reno. Aerial photo

Newton, Massachusetts — A Star Market supermarket is built over the top of Interstate 90. Traffic reporters refer to this point on the highway as the "Star Market overpass". The Sheraton Newton Hotel is also built atop I-90. Aerial photos: Star Market Sheraton Newton Hotel

Boston, Massachusetts — The Prudential Tower as well as Copley Place, in downtown Boston is built over Interstate 90 as well. A less known fact about Interstate 90 is that it is built over what used to be the largest railroad corridor in New England; photos from the 1950s show huge rail yards where I-90 now comes into the city. Many of the oddities on I-90 are the result of deals struck by the Massachusetts Turnpike Authority, Perini Corporation (which constructed the majority of the highway), and existing buildings at the time of construction. In return for not obstructing the highway project, the MTA went to lengths such as preserving the aforementioned Star Market. Aerial photos: Prudential Tower Copley Place

Atlanta, Georgia — The Civic Center MARTA station is located over the Downtown Connector (Interstate 75/85) at West Peachtree Street, making it the only subway station built over an Interstate highway. Aerial photo Photo: see second link on [9] (Angelfire images cannot be deep-linked.)

Illinois — The Illinois Tollway oasis is a type of rest area which spans the top of the interstate highway it is on [10]. There are seven of them which are on the Tri-State Tollway (Interstates 80, 94 & 294), Northwest Tollway (Interstate 90) and the Ronald Reagan Memorial Tollway (Interstate 88). Customers are able to sit inside the Oases and eat while traffic goes by beneath them. This type of development is common in the UK.

St. Louis, Missouri — There is a large bridge-like structure connecting two ends of The St. Louis Science Center built over Interstate 64. People walking through the structure can see cars going by, and use radar guns to measure their speed. Also, cars driving below can see the atmospheric condition of the general area every morning, as it is posted on an electronic sign on the side. Aerial photo

Seattle, Washington — The Freeway Park sits on top of Interstate 5 (NB and SB, including HOV express lanes) connecting downtown to the Capitol Hill and First Hill districts (locally, First Hill is also known as "Pill Hill" as this is Seattle's medical district). The park is multi-level and as such, there are areas where visitors are able to watch traffic pass by. The park is connected to the Washington State Convention Center which is also built on top of I-5. Aerial photos: Freeway Park Washington State Convention Center

Kansas City, Missouri — Bartle Hall Convention Center spans I-670 in downtown Kansas City. Aerial photo

Long-distance mileage signs on Interstates

Image:IMG 28052.jpg

Petersburg, Virginia — Heading southbound on Interstate 95 past Petersburg before the I-85 interchange, there are 2 signs that show Miami (which is 920 miles away) as the destination of I-95 and Atlanta (507 miles away) as the destination for the I-85 exit. Signs on southbound I-95 heading Richmond, Virginia at the I-295 interchange showing Miami (958 miles away) as a control city (via I-295) were removed in 2001. [11] Photos: Exit 52 sign from [12], Exit 51 sign pictured right.

Baltimore, Maryland — Near the east end of Interstate 70, while driving westbound, just after crossing the I-695/Baltimore Beltway interchange there is a sign that gives the distance (2200 miles) to Cove Fort, Utah, the town nearest to the west end of I-70. Photo: [13] from [14]

Barstow, California and Wilmington, North Carolina — At both termini of Interstate 40 are signs that give the distance along I-40 (2554 miles) to the other end. Photos: Western end at Barstow, CA from [15], Eastern end at Wilmington, NC from [16]

San Jon, New Mexico — Interstate 40 also has a mileage sign in New Mexico to the east of San Jon (a village to the east of Tucumcari, New Mexico) showing 1007 miles for Los Angeles, probably the longest distance on a conventional mileage sign. [17]

Other trivia

Most Interstates are maintained by the states or toll authorities. The Woodrow Wilson Bridge, part of Interstate 95 and Interstate 495, is maintained by the federal government. A few Interstates are maintained by local authorities:

Baltimore, Maryland: Interstate 70 and Interstate 83 in the city limits<ref>Maryland's Interstate System (PDF)</ref>
New York City: Small portions of Interstate 278<ref>New York State Department of Transportation - Region 11 (New York City) Built and Unbuilt Arterial System</ref>
Washington, D.C.: As the city and district are identical, the district maintains the portions of Interstate 66, Interstate 295, Interstate 395 and Interstate 695 inside the city.

The only concurrency of two auxiliary routes is Interstate 271 and Interstate 480 near Cleveland, Ohio.

See also

List of gaps on Interstate Highways

All but five state capitals are directly served by the Interstate System. Carson City, Nevada; Dover, Delaware; Jefferson City, Missouri; Juneau, Alaska; and Pierre, South Dakota are not.

Criticism

Charles Kuralt has argued, "It is now possible to travel from coast to coast without seeing anything!"<ref>Wilson, Amy. U.S. Route 66: Historic Road Is Time Line of America. National Geographic News. January 18, 2002. URL accessed 21:31, 18 February 2006 (UTC).</ref> This is an apparent reference to the tendency of Interstate highways to emphasize more rapid, uninterrupted transportation than other road networks.

References

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See also

Template:Ed rightMain Interstate Highways (major in pink)														Image:I-blank.svg
4	5	8	10	12	15	16	17	19	20	22	24	25	26	27	29
30	35	37	39	40	43	44	45	49	55	57	59	64	65	66	68
69	70	71	72	73	74	75	76 (W)		76 (E)		77	78	79	80	81
82	83	84 (W)		84 (E)		85	86 (W)		86 (E)		87	88 (W)		88 (E)
89	90	91	93	94	95	96	97	99	(238)		H-1	H-2	H-3
Unsigned			A-1	A-2	A-3	A-4	PRI-1		PRI-2		PRI-3
Lists		Main - Auxiliary - Suffixed - Business - Proposed - Unsigned Gaps - Intrastate - Interstate standards

External links

Template:Commons

Interstate Highway information
FHWA Route Log and Finder List
FHWA Turner-Fairbank Highway Research Center - Analysis and History of Interstate Highway System
3-digit Interstate Highways
Pictures of all Interstates
One of 100 milestone documents of American history
Federal Highway Administration's article on the act
Fortune magazine on history of the Interstate Highway System
Tony Graham's Exit List Collection A compilation of all Interstate exit lists available online
Another great Interstate Page, with facts on all 2-digit Interstates and links to their exit lists
Highway Heaven Contains exit lists for most Interstate highways
RoadGeek - A complete set of TrueType fonts for simulating Interstate and other highway signage
2006: 50th Aniversary of the Interstate Highway System Celebration - from the American Road & Transportation Builders Association
Interstate50th.org - A website that celebrates the system's golden anniversary, filled with facts and other interesting information about the highways, such as where the first miles of Interstate were builtbg:Междущатска магистрална система

de:Highway#Interstate Highway eo:Interŝtata Ŝosea Sistemo fr:Interstate highway ja:ドワイト・デーヴィッド・アイゼンハワー全米州間国防高速道路網 nl:Interstate highway zh:州际高速公路

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