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A freeway is a type of road designed for safer high-speed operation of motor vehicles through the elimination of at-grade intersections. This is accomplished by preventing access to and from adjacent properties and eliminating all cross traffic through the use of grade separations and interchange; railroad crossings are also removed. Such highways are usually divided with at least two lane in each direction. Because traffic never crosses at-grade, there are generally no traffic lights or stop signs. Some countries have roads that function as freeways but use different names. These include autobahn, autovía, autoroute, autopista, autostrada, autosnelweg, motorway and expressway.

The word freeway first surfaced in the mid-1930s in proposals for the improvement of the New York Citymarker parkway network. It is currently in regular use in the United Statesmarker as well as parts of South Africa, Canadamarker, and Australia.

In the United Statesmarker, the term freeway is frequently used. In some regions of the U.S., other terms are also used, including Interstate, thruway, highway, expressway, and turnpike. While some people use these terms interchangeably, turnpikes and thruways have specific associations with toll roads and other limited access highways, such as the New Jersey Turnpike, Ohio Turnpike, Pennsylvania Turnpike, West Virginia Turnpike, Florida's Turnpikemarker, and New York State Thruway; consequently, the term freeway is often used in contrast to refer only to a toll-free road as opposed to its original meaning – in which the component "free" implies freedom from traffic interference rather than "at no cost" – still used in other countries and in parts of the U.S.

General characteristics

Freeways, by definition, have no at-grade intersections with other roads, railroads or multi-use trails. Movable bridges, such as the Interstate Bridgemarker on I-5 between Oregonmarker and Washingtonmarker, may require drivers to yield to cross traffic on the river. Not all roads bearing the name of freeway are in fact freeways by definition; for example, the William L. Wilson Freeway (U.S. Route 340) by Harpers Ferry, West Virginiamarker, is a two-lane undivided roadway featuring at-grade intersections.

The crossing of freeways by other routes is typically achieved with grade separation either in the form of underpasses or overpasses. In addition to sidewalks (footpaths) attached to roads that cross a freeway, specialized pedestrian footbridges or tunnels may also be provided. These structures enable pedestrians and cyclists to cross the freeway at that point without a detour to the nearest road crossing.

Access to freeways is typically provided only at grade-separated interchanges, though lower-standard right-in/right-out access can be used for direct connections to side roads. In many cases, sophisticated interchanges allow for smooth, uninterrupted transitions between intersecting freeways and busy arterial roads. However, sometimes it is necessary to exit onto a surface road to transfer from one freeway to another. An example of this would be Interstate 70 in the town of Breezewood, Pennsylvaniamarker.

Speed limits are generally higher on freeways, and are occasionally nonexistent (as on much of Germany's Autobahn network). Because higher speeds reduce decision time, freeways are usually equipped with a larger number of guide signs than other roads, and the signs themselves are physically larger. Guide signs are often mounted on overpasses or overhead gantries so that drivers can see where each lane goes. Exit numbers are commonly derived from the exit's distance in miles or kilometers from the start of the freeway. In some areas, there are public rest areas or service areas on freeways, as well as emergency phones on the shoulder at regular intervals.

In the United States, mileposts start at the southern or westernmost point on the freeway (either its terminus or the state line). Californiamarker, Ohiomarker, and Nevadamarker uses a postmile system where markers indicate mileage through the state's individual counties; however, Nevada, Ohio, and much of the Kern County portion of California State Route 58 also use the standard milepost system concurrently with their respective postmile systems on freeways only.

Cross sections

Two-lane freeways, often undivided, are sometimes built when traffic volumes are low or right-of-way is limited; they may be designed for easy conversion to one side of a four-lane freeway. Otherwise, freeways typically have at least two lanes in each direction; some busy ones can have as many as 16 or more lanes in total.

In Mississauga, Ontariomarker, Highway 401 uses collector-express lanes for a total of 18 lanes through its intersection with 403/410 and 427. In San Diego, Californiamarker, Interstate 5 has a similar system of express and local lanes for a maximum width of 21 lanes on a two-mile segment between Interstate 805 and California State Route 56.

These wide freeways may use separate collector and express lanes to separate through traffic from local traffic, or special high-occupancy vehicle lanes, either as a special restriction on the innermost lane or a separate roadway, to encourage carpooling. These HOV lanes, or roadways open to all traffic, can be reversible lanes, providing more capacity in the direction of heavy traffic, and reversing direction before traffic switches. Sometimes a collector/distributor road, a shorter version of a local lane, shifts weaving between closely-spaced interchanges to a separate roadway or altogether eliminates it.

In some parts of the world, notably parts of the US, frontage roads form an integral part of the freeway system. These parallel surface roads provide a transition between high-speed "through" traffic and local traffic. Frequent slip-ramps provide access between the freeway and the frontage road, which in turn provides direct access to local roads and businesses.

Except on some two-lane freeways (and very rarely on wider freeways), a median separates the opposite directions of traffic. This strip may be as simple as a grassy area, or may include a crash barrier such as a "Jersey barrier" or a "Ontario Tall Wall"" to prevent head-on collisions. On some freeways, the two carriageways are built on different alignments; this may be done to make use of available corridors in a mountainous area or to provide narrower corridors through dense urban areas.

Some roads in Ohiomarker that conform to freeway criteria use at-grade intersections in lieu of over/under-passes, with occasional interchanges to avoid signalized traffic interruption (i.e., traffic lights are omitted). Examples include US 23 between OH-15's eastern terminus and Delaware, Ohiomarker, along with highway 15 between its eastern terminus and I-75, US-30, OH-29/US-33, and US-35 in western and central Ohio. These roads are fundamentally expressways, but expressways tend to have lower design speeds, and signalized at-grade intersections.

Access restrictions

A bicyclist using a freeway legally

To reduce the probability that high-speed freeway traffic will have to slow down for slower same-direction traffic, access to freeways is usually limited to drivers of motor vehicles which are powerful enough to maintain a certain minimum speed. Some East Asian countries partially restrict the use of motorcycles or ban them completely from freeways (or expressways in countries where that term is used) (see restrictions on motorcycle use on freeways).

Travelers in a low-powered transportation class (such as pedestrian, bicyclist, equestrian, and moped driver) are banned at all times from the freeways in many areas by default. In some jurisdictions, these classes are allowed on the shoulders of certain freeways (usually where the freeway completely replaced an existing road) or on sidepaths.

Legal definitions


The OECD has defined a motorway [freeway] as:
French Equivalent: Autoroute
Road, specially designed and built for motor traffic, which does not serve properties bordering on it, and which:

:(a) is provided, except at special points or temporarily, with separate carriageways for the two directions of traffic, separated from each other, either by a dividing strip not intended for traffic, or exceptionally by other means;

:(b) does not cross at level with any road, railway or tramway track, or footpath;

:(c) is specially sign-posted as a motorway and is reserved for specific categories of road motor vehicles.

Entry and exit lanes of motorways are included irrespectively of the location of the sign-posts. Urban motorways are also included.

United States

In the United States, a "freeway" is defined by the federal government’s Manual on Uniform Traffic Control Devices as a divided highway with full control of access. This means two things. First, adjoining property owners do not have a legal right of access, meaning that they cannot connect their lands to the highway by constructing driveways, although frontage roads provide access to properties adjacent to a freeway in many places. When an existing road is converted into a freeway, all existing driveways must be removed and access to adjacent private lands must be blocked with fences or walls.

Second, traffic on a freeway is "free-flowing". All cross-traffic (and left-turning traffic) is relegated to overpasses or underpasses, so that there are no traffic conflicts on the main line of the highway which must be regulated by traffic lights, stop signs, or other traffic control devices. Achieving such free flow requires the construction of many overpasses, underpasses, and ramp systems. The advantage of grade-separated interchanges is that freeway drivers can almost always maintain their speed at junctions since they do not need to yield to vehicles crossing perpendicular to mainline traffic.

In contrast, an expressway is defined as a divided highway with partial control of access. Expressways may have driveways and at-grade intersections, though these are usually less numerous than on ordinary arterial roads.

This distinction was apparently first developed in 1949 by the Special Committee on Nomenclature of what is now the American Association of State Highway and Transportation Officials. In turn, the definitions were incorporated into AASHTO's official standards book, the Manual on Uniform Traffic Control Devices, which would become the national standards book of the U.S. Department of Transportation under a 1966 federal statute. The same distinction has also been codified into the statutory law of seven states: Californiamarker, Mississippimarker, Missourimarker, Nebraskamarker, North Dakotamarker, Ohiomarker, and Wisconsinmarker. However, each state codified the federal distinction slightly differently. California expressways do not necessarily have to be divided, though they must have at least partial access control. For both terms to apply, in Wisconsin, a divided highway must be at least four lanes wide; and in Missouri, both terms apply only to divided highways at least long that are not part of the Interstate Highway System. In North Dakota and Mississippi, an expressway may have "full or partial" access control and "generally" has grade separations at intersections; a freeway is then defined as an expressway with full access control. Ohio's statute is similar, but instead of the vague word generally, it imposes a requirement that 50% of an expressway's intersections must be grade-separated for the term to apply.

The term expressway is also used for what the federal government calls "freeways"; see the expressway article for further information. Where the terms are distinguished, freeways can be characterized as expressways upgraded to full access control, while not all expressways are freeways.

In contrast, there are at least three highways in the United States which are technically expressways (under the federal definition) but contain the word "freeway" in their names: State Fair Freeway in Kansas, Rockaway Freeway in New York, and Shenango Valley Freeway (a portion of U.S. Route 62) in Pennsylvania.

South Africa

In South Africa, a freeway is a road where certain restrictions apply. These are not allowed on a freeway:
  • a vehicle drawn by an animal;
  • a pedal cycle (such as a bicycle);
  • a motor cycle having an engine with a cylinder capacity not exceeding 50 cubic centimetres or which is propelled by electrical power;
  • a motor tricycle or motor quadrucycle;
  • pedestrians

Drivers may not use hand signals on a freeway (except in emergencies) and the minimum speed on a freeway is . Drivers in the rightmost lane of multi-carriageway freeways must move to the left if a faster vehicle appraches it from behind to overtake.

It is a common misconception that "freeway" means a road with at least two lanes, but single carriageway freeways do exist, such as portions of the N1 between Bloemfonteinmarker and Johannesburgmarker.

Effects and controversy

Freeways have been constructed both between urban centers and within them, leading to the sprawling suburban development found near most modern cities. Freeways reduced travel times and accident rates, though the higher speeds have increased the severity and death rates of the collisions that do occur.

Freeways have been heavily criticized by environmentalists, urbanists, and preservationists for the noise, pollution, and economic shifts they bring. Additionally, they have also been criticized by the driving public for the inefficiency with which they handle peak hour traffic.

Often, rural freeways open up vast areas to economic development, generally raising property values. In contrast to this, above ground freeways in urban areas are often a source of lowered property values, contributing to urban decay. Even with overpasses and underpasses, above ground freeways divide neighborhoods — especially impoverished ones where residents are less likely to own a car, or to have the political and economic influence to resist construction efforts. Beginning in the early 1970s, the U.S. Congress identified freeways and other urban highways as responsible for most of the noise exposure of the U.S. population. Subsequently, computer models were developed to analyze freeway noise and aid in their design to help minimize noise exposure.

Some freeways have even been demolished and reclaimed as boulevards or parks, notably in Portlandmarker (Harbor Drive), New York Citymarker (West Side Highway), Bostonmarker (Central Arterymarker), San Franciscomarker (Embarcadero Freeway) and Milwaukeemarker (Park East Freeway).

An alternative to surface or above ground freeway construction has been the construction of underground urban freeways using tunnelling technologies. This has been extremely successful in the Australian cities of Sydneymarker (which has five such freeways) and Melbournemarker (which has two such freeways). This has had the benefit of removing traffic from surface roads and in the case of Melbourne's Eastlink Motorway, has helped preserve an ecologically sensitive area from destruction.

Other Australian cities face similar problems (lack of available land, cost of home acquisition, aesthetic problems, and community opposition). Brisbane, which also has to contend with physical boundaries (the river) and heavy population increases, has embraced underground tunnel freeways. There are currently three under active development, one of which (the North-South Bypass Tunnel) is currently under construction. All of the planned tunnels include provisions for public transport, whether underground or in reclaimed space on the surface.

Freeway opponents have found that freeway expansion is often self-defeating: expansion simply generates more traffic. That is, even if traffic congestion is initially shifted from local streets to a new or widened freeway, people will begin to run errands and commute to more remote locations. Over time, the freeway and its environs become congested again as both the average number and distance of trips increases. This idea is known as induced demand.
Interstate H-1 eastbound into Honolulu, Hawaii.
Urban planning experts such as Drusilla Van Hengel, Joseph DiMento, and Sherry Ryan, argue that although properly designed and maintained freeways may be convenient and safe, at least in comparison to uncontrolled roads, they may not expand recreation, employment and education opportunities equally for different ethnic groups, or for people located in certain neighborhoods of a given city. Still, they may open new markets to some small businesses.

Construction of urban freeways for the U.S. Interstate Highway System, which began in the late 1950s, led to the demolition of thousands of city blocks, and the dislocation of many more thousands of people. The citizens of many inner city areas responded with the freeway and expressway revolts. Through the study of Washington's response, it can be shown that the most effective changes came not from executive or legislative action, but instead from policy implementation. One of the foremost rationales for the creation of the U.S. Department of Transportation (DOT) was that an agency was needed to mediate between the conflicting interests of interstates and cities. Initially, these policies came as regulation of the state highway departments. Overtime, DOT officials re-focused highway building from a national level to the local scale. With this shift of perspective came an encouragement for alternative transportation, and locally based planning agencies.

At present, freeway expansion has largely stalled in the United Statesmarker, 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 federally-funded 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), the tax revolt movement, and growing popular support for high-speed mass transit in lieu of new freeways.


The concept of limited-access automobile highways dates back to the New York Citymarker area Parkway system, whose construction began in 1907–1908; but parkways are traditionally distinguished from freeways by lower design speeds and a ban on commercial traffic. Some parkways, notably the Taconic Parkway, Sprain Brook Parkway, and Saw Mill Parkway have at-grade intersections, although direct access to property adjacent to the parkways is prohibited. Designers elsewhere also researched similar ideas, especially in Germanymarker, where the Autobahn would become the first national freeway system.

However, in 1925, Italymarker was technically the first country to build a freeway-like road, which linked Milanmarker to Lake Comomarker. It is known in Italy as the Autostrada dei Laghi.

Meanwhile, in Great Britainmarker, the related concept of the motorway was first proposed by Sidney Webb in a 1910 book, The King's Highway, but was not formally embraced by the government until the passage of the Special Roads Act 1949. In 1926, the English intellectual Hilaire Belloc recognized the necessity of grade-separated roads for "rapid and heavy traffic", but thought they would be the exception rather than the rule:

The creation of a great network of local highways suitable for rapid and heavy traffic is impossible. Even if the wealth of the community increases, the thing would be impossible, because it would mean the destruction of such a proportion of buildings as would dislocate all social life.

Connecticutmarker's Merritt Parkway was one of the first long-distance freeways in America when it opened on June 29, 1938, but its design standards are well below modern best practices. Two years later, the Pennsylvania Turnpike opened on October 1, 1940, connecting the outskirts of Harrisburgmarker and Pittsburgmarker. It was designed so that straightaways could handle maximum speeds of 102 miles per hour, and curves could be taken as fast as 90.

In stages from 1938 to 1940, Californiamarker opened its first significant freeway, the Arroyo Seco Parkway (now called the Pasadena Freeway) which connected Pasadenamarker with Los Angelesmarker. And in 1942, Detroit, Michiganmarker opened the world's first urban depressed freeway, the Davison Freeway.Portions of the first freeway in Texasmarker and the Southern United States, the Gulf Freeway in Houstonmarker, opened in 1948. Meanwhile, traffic in Los Angeles continued to deteriorate and local officials began planning the huge freeway network for which the city is now famous.

Today, many freeways in the United States belong to the extensive Interstate Highway system (most of which was completed between 1960 and 1990). Starting in the 1970s freeways began to consider environmental factors, particularly noise and air quality in their location and design. Nearly all Interstate Highways are freeways. The earlier United States highway system and the highway systems of U.S. states also have many sections that are built to controlled-access standards (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 and a segment of Interstate 93 through Franconia Notchmarker, New Hampshiremarker that is a 2-lane road with partial access control.

Recent developments

Australia has been innovative in using the newest tunneling technologies to bring freeways into its high-density central business districts (Sydneymarker, Perthmarker and Melbournemarker). Brisbanemarker currently has three major freeway tunnels under development. The city of Adelaidemarker pioneered the concept of a dedicated reversible freeway. The M2 Southern Expressway operates toward the city centre in the morning and away from the city centre in the afternoon and evening. Its ramps are designed so that they can double as on- or off-ramps, depending upon the time of day. Gates and electronic signage prevent motorists from driving in the wrong direction.

Around the world, major progress has been made in making existing freeways and expressways more efficient. Innovations include the addition of high-occupancy vehicle lanes (HOV lanes) to discourage driving solo, and building new roads, or retro-fitting existing roads with train tracks down the median (or overhead). In the U.S., 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 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.

Public-private partnerships in the United States

Until the late 1990s, funding of construction and maintenance of the Interstate Highway System was by the national gasoline tax. Originally, revenues generated by the national gasoline tax were intended solely for the maintenance and expansion of the country's highway system. During the Clinton Administration, federal legislation was passed allowing the use of gasoline tax revenues to fund other government programs and projects not related to highways or transportation. Since this reduced the amount of money available for the intended purpose of maintaining America's road network, many projects were either delayed, canceled, or scaled back.

Additionally, the original Highway Act of 1956 prohibited states from collecting tolls on Interstate-funded freeways. As more miles of freeways were completed, the cost of maintaining the infrastructure increased dramatically. A major issue that has slowed new freeway construction in America has been the application of highway funds to maintaining and repairing existing infrastructure. Most of the freeways in America are near or have exceeded their designed life span, which necessitates replacing of bridges and overpasses and reconstruction of the driving surfaces on many freeways nationwide.

To address the issue of lack of funding for new freeways and maintenance of existing roads, legislation enacted in 1998 gives states greater flexibility in funding major highway projects. Specifically the legislation, known as TEA-21 in official documents, authorizes states to add tolls to Interstate-funded freeways. Additionally, it gave states the latitude to enter into public-private partnership P3 arrangements to facilitate expansion and maintenance of the freeway network. Texasmarker, Floridamarker, Virginiamarker, and Californiamarker quickly took advantage of the TEA-21 legislation and began on massive projects to expand their respective states' freeway networks, complementing existing Interstate freeways with privately funded and operated tollways. In 2004, Illinoismarker sealed a $1.8 billion deal with Macquarie Infrastructure Group and Cintras to operate the Chicago Skywaymarker for 99 years. In a similar P3 arrangement in Indianamarker, the Cintras-Macquarie joint venture assumed responsibility for the Indiana East-West Toll Road for 75 years on June 30, 2006 in a very controversial $3.8 billion deal, which for political purposes was dubbed Major Moves. As of late 2006, Pennsylvaniamarker is actively pursuing the P3 toll road concept, but still has to clear challenges in the state legislature before such an arrangement can be implemented on the Pennsylvania Turnpike. Also in late 2006 Delawaremarker has plans to enter into an agreement with a private firm to design, build, and operate a planned 17 mile (27 km) bypass of U.S. Route 301 between Delaware Route 1 and the Maryland state line. Meanwhile in New Yorkmarker and Massachusettsmarker, the respective state public authorities that operate the New York State Thruway and Massachusetts Turnpike have generated enough revenue to assume maintenance of other freeways beyond the roads on which tolls are collected. The Massachusetts Turnpike Authority provided more than 50 percent of the funding to complete the Big Digmarker project in Boston, and later assumed responsibility for operating the Central Artery, the Sumner Tunnelmarker, and the Callahan Tunnelmarker following the project's completion in 2005.

As federal funding dries up for expanding and maintaining America's freeway network, states are looking to innovative solutions using a combination of state and federal funding, toll collection through public authorities, and private sector investment.

See also


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