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Ahighway is any public or privateroad or other public way on land. It includes not just major roads, but also other public roads andrights of way. In the United States, it is also used as an equivalent term tocontrolled-access highway, or a translation formotorway,Autobahn,autostrada,autoroute, etc.[1]
According toMerriam-Webster, the use of the term predates the 12th century. According toEtymonline, "high" is in the sense of "main".
InNorth American andAustralian English, major roads such as controlled-access highways orarterial roads are oftenstate highways (Canada:provincial highways). Other roads may be designated "county highways" in the US andOntario. These classifications refer to the level of government (state, provincial, county) that maintains the roadway. InBritish English, "highway" is primarily a legal term. Everyday use normally implies roads, while the legal use covers any route or path with a public right of access, includingfootpaths etc.
The term has led to several related derived terms, includinghighway system,highway code,highway patrol andhighwayman.
Major highways are often named and numbered by the governments that typically develop and maintain them. Australia'sHighway 1 is the longest national highway in the world at over 14,500 kilometres (9,000 mi) and runs almost the entire way around the continent. China has the world's largest network of highways, followed closely by the United States. Some highways, like thePan-American Highway or theEuropean routes, span multiple countries. Some major highway routes includeferry services, such asUS Route 10, which crossesLake Michigan.
Traditionally highways were used bypeople on foot or onhorses. Later they also accommodatedcarriages,bicycles and eventuallymotor cars, facilitated by advancements inroad construction. In the 1920s and 1930s, many nations began investing heavily in highway systems in an effort to spurcommerce and bolster national defence.
Major highways that connect cities in populousdeveloped anddeveloping countries usually incorporate features intended to enhance the road's capacity, efficiency, and safety to various degrees. Such features include areduction in the number of locations for user access, the use ofdual carriageways with two or more lanes on each carriageway, andgrade-separated junctions with other roads and modes of transport. These features are typically present on highways built asmotorways (freeways).
The general legal definition deals with right of use, not the form of construction; this is distinct from e.g. the popular use of the word in the US. A highway is defined in Englishcommon law by a number of similarly worded definitions such as "a way over which all members of the public have the right to pass and repass without hindrance"[2] usually accompanied by "at all times"; ownership of the ground is for most purposes irrelevant, thus the term encompasses all such ways from the widest trunk roads in public ownership to the narrowest footpath providing unlimited pedestrian access over private land.
A highway might be open to all forms of lawful land traffic (e.g. vehicular, horse, pedestrian) or limited to specific modes of traffic; usually a highway available to vehicles is also available to foot or horse traffic, a highway available to horse traffic is available to cyclists and pedestrians; but there are exceptional cases in which a highway is only available to vehicles, or is subdivided into dedicated parallel sections for different users.
A highway can share ground with a private right of way for which full use is not available to the general public: for example farm roads which the owner may use for any purpose but for which the general public only has a right of use on foot or horseback. The status ofhighway on most older roads has been gained by established public use, while newer roads are typicallydedicated as highways from the time they are adopted (taken into the care and control of a council or other public authority). In England and Wales, a public highway is also known as "The King's Highway".[3]
The core definition of a highway is modified in various legislation for a number of purposes but only for the specific matters dealt with in each such piece of legislation. This is typically in the case of bridges, tunnels and other structures whose ownership, mode of use or availability would otherwise exclude them from the general definition of a highway. Recent examples include toll bridges and tunnels which have the definition ofhighway imposed upon them (in a legal order applying only to the individual structure) to allow application of most traffic laws to those using them but without causing all of the general obligations or rights of use otherwise applicable to a highway.
Limited access highways for vehicles, with their own traffic rules, are called "motorways" in the UK.[4]
Scots law is similar to English law with regard to highways but with differing terminology and legislation. What is defined in England as ahighway will often in Scotland be what is defined by s.151Roads (Scotland) Act 1984 (but only "in this act" although other legislation could imitate) simply as aroad, that is:
The wordhighway is itself no longer a statutory expression in Scots law[5] but remains in common law.
In American law, the word "highway" is sometimes used to denote any public way used for travel, whether a "road, street, and parkway";[6] however, in practical and useful meaning, a "highway" is a major and significant, well-constructed road that is capable of carrying reasonably heavy to extremely heavy traffic.[7] Highways generally have a route number designated by the state and federal departments of transportation.[clarification needed]
California Vehicle Code, Sections 360, 590, define a "highway" as only a way open for use by motor vehicles, but the California Supreme Court has held that "the definition of 'highway' in the Vehicle Code is used for special purposes of that act" and that canals of the Los Angeles neighborhood ofVenice are "highways" that are entitled to be maintained with state highway funds.[8]
Large scale highway systems developed in the 20th century asautomobile usage increased. The first United Stateslimited-access road was constructed on Long Island, New York, and known as theLong Island Motor Parkway or the Vanderbilt Motor Parkway. It was completed in 1911.[11] It included many modern features, includingbanked turns,guard rails and reinforced concretetarmac.[12] Traffic could turn left between the parkway and connectors, crossing oncoming traffic, so it was not acontrolled-access highway (or "freeway" as later defined by the federal government'sManual on Uniform Traffic Control Devices).
Italy was the first country in the world to build controlled-access highways reserved for fast traffic and for motor vehicles only.[9][10] TheAutostrada dei Laghi ("Lakes Highway"), the first built in the world, connectingMilan toLake Como andLake Maggiore, and now parts of theA8 andA9 highways, was devised byPiero Puricelli and was inaugurated in 1924.[10] This highway, calledautostrada, contained only one lane in each direction and no interchanges.
TheSouthern State Parkway opened in 1927, while theLong Island Motor Parkway was closed in 1937 and replaced by theNorthern State Parkway (opened 1931) and the contiguousGrand Central Parkway (opened 1936). In Germany, construction of theBonn-Cologne Autobahn began in 1929 and was opened in 1932 byKonrad Adenauer, then the mayor ofCologne.[13] Soon the Autobahn was the first limited-access, high-speed road network in the world, with the first section fromFrankfurt am Main toDarmstadt opening in 1935.[14]
In the US, theFederal Aid Highway Act of 1921 (Phipps Act) enacted a fund to create an extensive highway system. In 1922, the first blueprint for a national highway system (thePershing Map) was published. TheFederal Aid Highway Act of 1956 allocated $25 billion for the construction of the 66,000-kilometre-long (41,000 mi)Interstate Highway System over a 20-year period.[15]
InGreat Britain, theSpecial Roads Act 1949 provided the legislative basis for roads for restricted classes of vehicles and non-standard or no speed limits applied (later mostly termedmotorways but now with speed limits not exceeding 70 mph);[16] in terms of general road law this legislation overturned the usual principle that a road available to vehicular traffic was also available to horse or pedestrian traffic as is usually the only practical change when non-motorways are reclassified asspecial roads. The first section of motorway in the UK opened in 1958 (part of the M6 motorway) and then in 1959 the first section of theM1 motorway.[17]
Often reducing travel times relative to city or town streets, highways with limited access and grade separation can create increased opportunities for people to travel for business, trade or pleasure and also provide trade routes for goods. Highways can reduce commute and other travel time but additional road capacity can also releaselatent traffic demand. If not accurately predicted at the planning stage, this extra traffic may lead to the new road becoming congested sooner than would otherwise be anticipated by considering increases in vehicle ownership. More roads allow drivers to use their cars when otherwise alternatives may have been sought, or the journey may not have been made, which can mean that a new road brings only short-term mitigation of traffic congestion.
Where highways are created through existing communities, there can be reducedcommunity cohesion and more difficult local access. Consequently, property values have decreased in many cutoff neighborhoods, leading to decreased housing quality over time. Mostly in the U.S., many of these effects are fromracist planning practices from before the advent ofcivil rights. This would result in the vast majority of displacement and social effects mostly going to people like African Americans.[19]
In recent times, the use offreeway removal or the public policy ofurban planning to demolish freeways and create mixed-use urban areas, parks, residential, commercial, or other land uses is being popular in many cities to combat most of the social problems caused from highways.[20]
In transport,demand can be measured in numbers of journeys made or in total distance travelled across all journeys (e.g.passenger-kilometres forpublic transport or vehicle-kilometres of travel (VKT) forprivate transport).Supply is considered to be a measure of capacity. Theprice of the good (travel) is measured using thegeneralised cost of travel, which includes bothmoney andtime expenditure.
The effect of increases in supply (capacity) are of particular interest in transport economics (seeinduced demand), as the potential environmental consequences are significant (seeexternalities below).
In addition to providing benefits to their users, transport networks impose bothpositive andnegative externalities on non-users. The consideration of these externalities—particularly the negative ones—is a part of transport economics. Positive externalities of transport networks may include the ability to provideemergency services, increases inland value andagglomeration benefits. Negative externalities are wide-ranging and may include localair pollution,noise pollution,light pollution,safety hazards,community severance andcongestion. The contribution of transport systems to potentially hazardousclimate change is a significant negative externality which is difficult to evaluate quantitatively, making it difficult (but not impossible) to include in transport economics-based research and analysis. Congestion is considered a negativeexternality by economists.[21]
A 2016 study found that for the United States, "a 10% increase in a region's stock of highways causes a 1.7% increase in regional patenting over a five-year period."[22] A 2021 study found that areas that obtained access to a new highway experienced a substantial increase in top-income taxpayers and a decline in low-income taxpayers. Highways also contributed to job and residential urban sprawl.[23]
Highways are extendedlinear sources ofpollution.
Roadway noise increases with operating speed so major highways generate more noise thanarterial streets. Therefore, considerablenoise health effects are expected from highway systems.Noise mitigation strategies exist to reduce sound levels at nearbysensitive receptors. The idea that highway design could be influenced byacoustical engineering considerations first arose about 1973.[24][25]
Air quality issues: Highways may contribute feweremissions than arterials carrying the same vehicle volumes. This is because high, constant-speed operation creates an emissions reduction compared to vehicular flows with stops and starts. However, concentrations of air pollutants near highways may be higher due to increased traffic volumes. Therefore, the risk of exposure to elevated levels of air pollutants from a highway may be considerable, and further magnified when highways havetraffic congestion.
New highways can also causehabitat fragmentation, encourageurban sprawl and allow human intrusion into previously untouched areas, as well as (counterintuitively) increasing congestion, by increasing the number of intersections.
They can also reduce the use ofpublic transport, indirectly leading to greater pollution.
High-occupancy vehicle lanes are being added to some newer/reconstructed highways in the United States and other countries around the world to encouragecarpooling and mass transit. These lanes help reduce the number of cars on the highway and thus reduces pollution and traffic congestion by promoting the use of carpooling in order to be able to use these lanes. However, they tend to require dedicated lanes on a highway, which makes them difficult to construct in dense urban areas where they are the most effective.
To address habitat fragmentation,wildlife crossings have become increasingly popular in many countries. Wildlife crossings allow animals to safely cross human-made barriers like highways.[26]
Road traffic safety describes the safety performance of roads and streets, and methods used to reduce the harm (deaths, injuries, and property damage) on the highway system fromtraffic collisions. It includes the design, construction and regulation of theroads, thevehicles used on them and the training of drivers and other road-users.
A report published by theWorld Health Organization in 2004 estimated that some 1.2 million people were killed and 50 million injured on the roads around the world each year[27] and was the leading cause of death among children 10–19 years of age.
The report also noted that the problem was most severe in developing countries and that simple prevention measures could halve the number of deaths.[28] For reasons of clear data collection, only harm involving a road vehicle is included.[29] A person tripping with fatal consequences or dying for some unrelated reason on a public road is not included in the relevant statistics.
The United States has the world's largest network of highways, including both theInterstate Highway System and theUnited States Numbered Highway System. At least one of these networks is present in every state and they interconnect most major cities. It is also the world's most expensive mega-project,[30] as the entirety of the Interstate Highway System was estimated to cost $27 billion in 1955 (equivalent to $240 billion in 2023[31]).[32]
China's highway network is the second most extensive in the world, with a total length of about 3,573,000 kilometres (2,220,000 mi).[33][34][35][36][37] China'sexpressway network is the longest Expressway system in the world, and it is quickly expanding, stretching some 85,000 kilometres (53,000 mi) at the end of 2011.[38][39] In 2008 alone, 6,433 kilometres (3,997 mi) expressways were added to the network.[40]
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| Country | Highway | Bus lanes (km) | Section | Notes |
|---|---|---|---|---|
| Australia | M2 Hills Motorway | 21.4 | Abbott Road–Beecroft Road (Sydney) | |
| Australia | Eastern Freeway | 11 | Hoddle Street–DoncasterPark & Ride (Melbourne) | Under construction, to be finished 2027-2028 |
| Canada | Don Valley Parkway | 0.458 | Shoulder converted as bypass lane from Lawrence Avenue East to York Mills Road | |
| Canada | Ontario Highway 417 | 7 | Eagleson Road–Ontario Highway 417 (Ottawa) | |
| Canada | Ontario Highway 403 | 6 | Mavis Road–Winston Churchill Boulevard (Mississauga) | |
| Hong Kong | Tuen Mun Road | 19.4 | ||
| India | National Highway (India) | 19 | 30 lanes Road, (Mumbai) | |
| Netherlands | A1 motorway (Netherlands) | 119 | End of A6-Vechtbrug (Muiden) | |
| South Korea | Gyeongbu Expressway | 137.4 | Hannam IC (Seoul) ~ Sintanjin IC (Daejeon) | |
| United States | El Monte Busway | 19 | Shared use Busway between Interstate 10 betweenLos Angeles Union Station andEl Monte Station (Los Angeles)[48] |
InSouth Korea, in February 1995 abus lane (essentially anHOV-9) was established between the northern terminus and Sintanjin for important holidays and on 1 July 2008 bus lane enforcement between Seoul and Osan (Sintanjin on weekends) became daily between 6 a.m. and 10 p.m. On 1 October this was adjusted to 7 a.m. to 9 p.m. weekdays, and 9 a.m. to 9 p.m. weekends.
InHong Kong, some highways are set up with bus lanes to solve the traffic congestion.
| District | Highway | Section |
|---|---|---|
| Tuen Mun |  Tuen Mun Road | So Kwun Wat toSham Tseng |
| Sha Tin |  Lion Rock Tunnel | The entry of the tunnel |
Traffic congestion was a principal problem in majorroads andhighways in thePhilippines, especially inMetro Manila and other major cities. The government decided to set up some bus lanes in Metro Manila like in theEpifanio delos Santos Avenue.
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The following is a list of highways by country in alphabetical order.
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The 'phenomenal' number of vehicles on Hwy. 401 as it cuts through Toronto makes it the busiest freeway in North America...
