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Freeway

From Academic Kids

For the rapper, see Freeway (rapper). For the film, see Freeway (movie). For the Mac HTML editor, see Softpress Freeway.
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A typical rural freeway (Interstate 5 in the Central Valley of California).

A freeway (also superhighway, expressway or motorway as further explained below) is a multi-lane highway (road) designed for high-speed travel by large numbers of vehicles, and having no traffic lights, stop signs, nor other regulations requiring vehicles to stop for cross-traffic.

Contents

In general

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Standard wrong-way sign package used on all freeway off-ramps in California (and since copied by Georgia and Virginia).

Freeways have high speed limits, multiple lanes for travel in each direction, and a large separation (either through distance or high crash barriers) between the lanes travelling in opposite directions. Crossroads are bypassed by grade (height) separation using underpasses and overpasses. Freeway entrances and exits are limited in number, and are designed with special onramps and offramps, so as to ensure that vehicles do not disrupt the main flow of traffic as they enter or leave the freeway. In some countries, the exits are numbered.

Where freeways cross, engineers provide interchanges with elaborate ramp systems that allow for smooth transitions between all through routes (as funds permit).

Because the high speeds reduce decision time, freeways usually have more traffic signs than the equivalent signs on most highways and roads; the signs are often also larger. In major cities, especially on freeways six lanes in width or wider, guide signs are mounted on overhead gantries so that drivers can see where each lane goes.

Another consequence of the high speeds and decreased decision time is that it is nearly impossible to avoid wrong-way drivers on freeways, and the subsequent head-on collisions are often fatal. Therefore, special signage is often used to discourage drivers from going the wrong way.

Freeways do not usually have traffic lights, but expressways may, in places where this distinction is made.

To minimize accidents, access to freeways is usually limited to vehicles capable of consistently maintaining a high speed, like automobiles, trucks, motorcycles, vans, and buses. Pedestrians, bicyclists, slow-moving vehicles, horses, horse-drawn vehicles, and anything else that might obstruct fast-moving vehicles are all prohibited.

In addition to the sidewalks attached to roads that go over or under a freeway, most countries also provide specialized pedestrian bridges and underground tunnels. Such structures enable pedestrians and cyclists to cross the freeway without having to make a long detour to the nearest road for which a grade separation has been provided.

In most parts of the world, there are public rest areas on freeways and expressways as well as other types of highways. In some U.S. states, public rest areas are located almost exclusively on freeways or expressways (since only those routes carry the high traffic necessary to justify the area's maintenance cost).

Nomenclature

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Stack interchanges often feature soaring ramps with stunning views of nearby scenery.

Worldwide

Freeway is the term used in most of the United States, parts of Canada, and parts of Australia, notably Melbourne and Perth; the United Kingdom, the rest of Australia and other Commonwealth countries prefer motorway, most of Canada uses expressway, while the province of Qubec uses Autoroute; Autoroute is also used in France and other francophone countries; Mexico and other spanish-speaking countries use the term Autopista; the German-speaking world uses Autobahn, the Dutch-speaking world uses autosnelweg; Italy and Poland use autostrada; and China and Japan use the term expressway, although they once used freeway.

The U.S. distinction between expressways and freeways

The United States definition, as accepted by civil engineers, is that an expressway is any highway to which adjoining property owners do not have a legal right of access. A freeway is an expressway which is free-flowing; that is to say, there are no traffic conflicts on the main line of the highway which must be mediated by a traffic signal, stop signs, or related traffic controls. Another way to look at it is that an expressway is limited-access, and a freeway is controlled-access, but this distinction is not universally accepted. Many non-engineers misapprehend the "free" in "freeway" to mean that such a highway must be free of charge to use. In some states, like California, the vast majority of freeways are toll-free (except where they cross an occasional toll bridge), while other states like Illinois and Florida have toll plazas at every exit on certain expressways.

A typical suburban freeway ( in ) with an  in the foreground
Enlarge
A typical suburban freeway (Interstate 405 in Irvine, California) with an interchange in the foreground

In the U.S., the terms expressway and freeway are legally defined by federal regulation and under the laws of most states according to civil engineering usage described above. However, the distinction between these two terms is not universal, and in several states which built freeways very early on (including Connecticut, Illinois, Massachusetts, New Jersey, New York, and Pennsylvania), the terms expressway and freeway have the same meaning, and usually expressway or just highway, an older usage, is preferred. (In New Jersey and Pennsylvania, newer roads are often officially styled freeways, where older roads retain the title "expressway".) In the rest of the country, freeway is the usual term; however, the distinction between freeways and expressways is not always as clear or well-understood as it is in California, which has many of both kinds of highway. Florida is an exception to these conventions, and the terms "expressway" and "freeway" have two separate and distinct meanings. In Florida, an "expressway" is defined as a limited-access toll road, while a "freeway" is any other limited- or controlled-access road which costs no money to travel on.

Some RIRO expressways may have at-grade intersections. Some commentators consider them to be freeways because they have design speeds of 65 mph or higher.

Construction issues

Freeways have been constructed both between urban centres and within them, making common the style of sprawling suburban development found near most modern cities. As well as reducing travel times, the ease of driving on them reduces accident rates, though the speeds involved also tend to increase the severity and death rate of the collisions (or crashes) that do still happen.

Frontage roads

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Interstate 80 is a major urban freeway in the San Francisco Bay Area (seen here near Berkeley, California). The frontage road on the far right typically becomes just as congested as the main freeway.

Because abutters do not have the right of access that they would have for an ordinary public road, the authority undertaking construction of a freeway is frequently required to provide alternate means of access to those landowners. This is frequently accomplished, in areas lacking a dense surface street network, by construction of two uncontrolled roads parallel to and on either side of the freeway, known as frontage roads. These often are designed with one-way traffic flow, but not always.

In Texas, where this pattern is perhaps at its zenith, such roads are frequently constructed in anticipation of a future freeway corridor, as many as ten years in advance, in order to influence development patterns on the adjoining land. Frontage roads are also often constructed in more densely-developed areas as a means to provide convenient direct access to and from the parallel freeway while minimizing the need for interchanges at every major cross street. However, some traffic studies have indicated that this particular type of access and the development that ensues generally causes significant traffic congestion and disrupts flows along major freeways. These studies prompted concern for TxDOT, which formally adopted a major shift in frontage road policy (http://www.abilenetx.com/comp/www.abilenecompplan.com/abilene_comp/documentframeset3fcd.html?docname=http://www.abilenecompplan.com:80/abilene_comp/docs/FrontageRoad.pdf) (2002) by stating that no new frontage roads will be built along any proposed limited-access freeways, thus ending a long-standing pattern of freeway-induced development in Texas. Access issues will continue to be assessed on a local basis, and frontage roads could still be constructed if warranted by traffic studies.

History

The concept of limited-access automobile highways dates back to the New York City area Parkway system, which began to be constructed in 19071908. Designers elsewhere also researched these ideas, especially in Germany, where the Autobahn became the first national freeway system. On December 30, 1940 California opened its first freeway, the Arroyo Seco Parkway, now called the Pasadena Freeway, which connected Pasadena with Los Angeles. Around the same time, Michigan opened its first freeway, the Davison Freeway, within Detroit. Today, many freeways in the United States belong to the extensive Interstate highway system (most of which was completed between 1960 and 1990). Almost all interstates are freeways, but the earlier United States highway system and the highway systems of U.S. states also have many sections that are limited-access (though these systems are mostly composed of uncontrolled roads). Only a handful of sections of the Interstate system are not freeways, such as I-81 as it crosses the American span of the 2-lane Thousand Islands Bridge.

Controversy

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Rush hour on I-45, downtown Houston.

Freeways have been heavily criticized by environmentalists and preservationists for the noise, pollution, and economic shifts they bring. Additionally, they have also been criticized by the driving public about the inefficiency in which they handle peak hour traffic. Often, rural freeways open up vast areas to economic development, generally raising property values. However, mature freeways in urban areas are quite often a source of lowered property values, contributing to the deleterious effects of urban blight. For this reason, almost no new urban freeways have been built in the U.S. since 1970, and some have even been demolished and reclaimed as boulevards, notably in San Francisco (Embarcadero Freeway) and Milwaukee (Park East Freeway). Some argue that freeway expansion is self-defeating, in that expansion will just generate more traffic. This is the debated induced demand hypothesis.

Pro-freeway advocates point out that properly designed and maintained freeways are aesthetically pleasing, convenient, and safe (in comparison to the uncontrolled roads they replace or supplement.) Freeways expand recreation, employment and education opportunities for individuals and open new markets to small businesses. And for many, uncongested freeways are fun to drive.

At present, freeway expansion has largely stalled in the United States, due to a multitude of factors that converged in the 1970s: higher due process requirements prior to taking of private property, increasing land values, increasing costs for construction materials, local opposition to new freeways in urban cores, the passage of the National Environmental Policy Act (which imposed the requirement that each new project must have an environmental impact statement or report), and falling gas tax revenues as a result of the nature of the flat-cent tax (it is not automatically adjusted for inflation) and the tax revolt movement. Dramatic improvements in vehicle gas mileage have also reduced gas tax revenues.

Recent developments

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The "Sound Tube" on the CityLink Freeway in Melbourne, Victoria, Australia).
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Autopista Central in Santiago, Chile.

Outside the U.S., many countries continue to rapidly expand their freeway networks. Examples include: Australia, Canada, Chile, China, France, India, Israel, Mexico, Malaysia and Taiwan. Australia and France in particular have been innovative in using the newest tunneling technologies to bring freeways into high-density downtowns (Sydney and Melbourne) and historic rural areas (Versailles). China already has the world's second largest freeway network in terms of total kilometers and will probably overtake the U.S. well before the end of the 21st century.

Meanwhile, major progress has been made in making existing U.S. freeways and expressways more efficient. Experiments include the addition of high-occupancy vehicle lanes (HOV lanes) to discourage driving solo, and building new roads with train tracks down the median (or overhead). California's Caltrans has been very innovative in squeezing HOVs into limited right-of-way (by elevating them), and in building special HOV-only ramps so that HOVs can switch freeways or exit the freeway without having to merge across regular traffic. Many states have added truck-only ramps or lanes on heavily congested routes, so that cars need not weave around slow-moving big rigs.

Intelligent transportation systems (ITS) are also increasingly used, with cameras to monitor and direct traffic, so that police, fire, ambulance, tow, or other assistance vehicles can be dispatched as soon as there is a problem, and to warn drivers via variable message signs, radio, television, and the web to avoid problem areas. Research has been underway for many years on how to partly automate cars by making smart roads with such things as buried magnets to guide sensor-equipped vehicles, with on-board GPS to determine location, direction, and destination. While these systems may eventually be used on surface streets as well, they are most practical in a freeway setting.

In the United States, a few short privatized tolled freeways have also been built by private companies with mixed success.

See also

External links

da:Motorvej de:Autobahn es:Autova fr:Autoroute ja:高速道路 it:Autostrada nl:Autosnelweg pl:Autostrada sv:Motorvg zh-cn:高速公路

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