Highway

{{Short description|Public road or other public way on land}} {{About|public roads|other uses of highway|Highway (disambiguation)|high-speed freeways|Controlled-access highway}} {{Use dmy dates|date=April 2025}} [[File:Street, Oguz (P1090484).jpg|thumb|A street in Oğuz, Azerbaijan]] [[File:Lakalaivan eritasoliittymä 1.jpg|thumb|An aerial view of the Lakalaiva interchange in the Tampere Ring Road between the Highway 3 (E12) and Highway 9 (E63) near city of Tampere]]

A '''highway''' in the broadest sense of the term is any public or private road or other public way on land, including not just major roads but also other public roads and rights of way. In the United States, the term means a major road that carries motor traffic at considerable speed, denoting a controlled-access highway (either a secondary highway or a limited-access highway) and being a translation for ''motorway'', ''Autobahn'', ''autostrada'', ''autoroute'', etc.<ref>{{Cite web|date=3 February 2021|title=What is the Freeway? - Definition & Meaning|url=https://www.autonewseye.com/what-is-the-freeway/|access-date=6 February 2021|website=Auto News Eye|language=en-US|archive-date=20 April 2021|archive-url=https://web.archive.org/web/20210420095829/https://www.autonewseye.com/what-is-the-freeway/|url-status=dead}}</ref>

According to Merriam-Webster, the use of the term predates the 12th century. According to Etymonline, "high" is in the sense of "main".

In North American and Australian English, major roads such as controlled-access highways or arterial roads are often state highways (Canada: provincial highways). Other roads may be designated "county highways" in the US and Ontario. These classifications refer to the level of government (state, provincial, county) that maintains the roadway. In British 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, including footpaths etc.

The term has led to several related derived terms, including highway system, highway code, highway patrol and highwayman.

== Overview == [[File:RA3 - Località Sant'Antonio.jpg|thumb|Raccordo autostradale RA3 In Italy, which connects the Tuscan cities of Florence and Siena]]

Major highways are often named and numbered by the governments that typically develop and maintain them. Australia's Highway 1 is the longest national highway in the world at over {{convert|145,00|km}} 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 the Pan-American Highway or the European routes, span multiple countries. Some major highway routes include ferry services, such as US Route&nbsp;10, which crosses Lake Michigan.

Traditionally highways were used by people on foot or on horses. Later they also accommodated carriages, bicycles and eventually motor cars, facilitated by advancements in road construction. In the 1920s and 1930s, many nations began investing heavily in highway systems in an effort to spur commerce and bolster national defence.

Major highways that connect cities in populous developed and developing countries usually incorporate features intended to enhance the road's capacity, efficiency, and safety to various degrees. Such features include a reduction in the number of locations for user access, the use of dual carriageways with two or more lanes on each carriageway, and grade-separated junctions with other roads and modes of transport. These features are typically present on highways built as ''motorways'' (''freeways'').

== Terminology ==

=== England and Wales === 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 English common 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"<ref>Diplock LJ, Suffolk County Council v. Mason [1979] AC 705</ref> 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 of ''highway'' on most older roads has been gained by established public use, while newer roads are typically ''dedicated'' 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''".<ref>{{cite encyclopedia |year = 2013 |url = http://oxforddictionaries.com/definition/english/Queen%27s%2Bhighway |archive-url = https://web.archive.org/web/20130502093225/http://oxforddictionaries.com/definition/english/Queen%27s%2Bhighway |url-status = dead |archive-date = 2 May 2013 |title = Queen's highway |encyclopedia = Oxford Dictionaries |publisher = Oxford University Press }}</ref>

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 of ''highway'' 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.<ref>Defining Safe Automated Driving Insurer Requirements for Highway Automation Thatcham Research 2019.</ref>

=== Scotland === Scots law is similar to English law with regard to highways but with differing terminology and legislation. What is defined in England as a ''highway'' will often in Scotland be what is defined by s.151 Roads (Scotland) Act 1984 (but only "in this act" although other legislation could imitate) simply as a '''road''', that is: *"any way (other than a waterway) over which there is a public right of passage (by whatever means [and whether subject to a toll or not]) and includes the road's verge, and any bridge (whether permanent or temporary) over which, or tunnel through which, the road passes; and any reference to a road includes a part thereof"

The word ''highway'' is itself no longer a statutory expression in Scots law<ref>{{cite book |first1 = Ann |last1 = Faulds |first2 = Trudi |last2 = Craggs |first3 = John |last3 = Saunders |name-list-style = amp |chapter-url = http://uk.practicallaw.com/books/9781845927806/chapter04 |chapter = Chapter&nbsp;4: The Definition of a Road? |title = Scottish Roads Law |edition = 2nd |publisher = Practical Law Company |date = 31 January 2008 |access-date = 21 March 2014 }}</ref> but remains in common law.

=== United States === [[File:Atlanta 75.85.jpg|thumb|The I-75/I-85 Downtown Connector in Atlanta, Georgia, in the United States]]

In American law, the word "highway" is sometimes used to denote any public way used for travel, whether a "road, street, and parkway";<ref name="23 U.S. Code § 101 (a)-(11)">{{cite web |title = 23 US Code § 101 |url = https://www.law.cornell.edu/uscode/text/23/101 }}</ref> 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.<ref>{{Cite web|url=https://www.merriam-webster.com/dictionary/highway|title=Definition of HIGHWAY|website=www.merriam-webster.com|language=en|access-date=9 March 2020}}</ref> Highways generally have a route number designated by the state and federal departments of transportation.{{Clarify|date=July 2010}}

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 of Venice are "highways" that are entitled to be maintained with state highway funds.<ref>{{Cite news |url = http://law.justia.com/cases/california/supreme-court/2d/3/184.html |title = City of Long Beach v. Payne |newspaper = Justia Law |access-date = 14 February 2017 |language = en }}</ref>

== History == {{See also|Road|History of road transport}} [[File:Autostrada between Varese and Como.jpg|thumb|right|The Italian ''Autostrada dei Laghi'' ("Lakes Highway" in the 1950s; now parts of the Autostrada A8 and the Autostrada A9), the first controlled-access highway ever built in the world<ref name="independent"/><ref name="motorwebmuseum"/>]]

Large scale highway systems developed in the 20th century as automobile usage increased. The first United States limited-access road was constructed on Long Island, New York, and known as the Long Island Motor Parkway or the Vanderbilt Motor Parkway. It was completed in 1911.<ref name="Autobahnhistory">{{cite web |url = http://german.about.com/library/blgermyth08_autobt.htm |title = An Autobahn Timeline |publisher = About.com |access-date = 10 April 2010 |archive-date = 23 June 2006 |archive-url = https://web.archive.org/web/20060623225946/http://german.about.com/library/blgermyth08_autobt.htm |url-status = dead }}</ref> It included many modern features, including banked turns, guard rails and reinforced concrete tarmac.<ref name="NYT_LIMP">{{cite news |last = Patton |first = Phil |date = 9 October 2008 |title = A 100-Year-Old Dream: A Road Just for Cars |work = The New York Times <!-- |access-date = 16 September 2009--> }}</ref> Traffic could turn left between the parkway and connectors, crossing oncoming traffic, so it was not a controlled-access highway (or "freeway" as later defined by the federal government's Manual 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.<ref name=independent>{{Cite news |first=Thea |last=Lenarduzzi |url=http://www.independent.co.uk/travel/europe/the-worlds-first-motorway-piero-puricellis-masterpiece-is-the-focus-of-an-unlikely-pilgrimage-a6840816.html|title=The motorway that built Italy: Piero Puricelli's masterpiece|date=30 January 2016|newspaper=The Independent|access-date=12 May 2022}}</ref><ref name="motorwebmuseum">{{cite web|url=https://www.motorwebmuseum.it/en/places/varese/the-milano-laghi-by-piero-puricelli-the-first-motorway-in-the-world/|title=The "Milano-Laghi" by Piero Puricelli, the first motorway in the world|access-date=10 May 2022}}</ref> The ''Autostrada dei Laghi'' ("Lakes Highway"), the first built in the world, connecting Milan to Lake Como and Lake Maggiore, and now parts of the A8 and A9 highways, was devised by Piero Puricelli and was inaugurated in 1924.<ref name="motorwebmuseum"/> This highway, called ''autostrada'', contained only one lane in each direction and no interchanges.

The Southern State Parkway opened in 1927, while the Long Island Motor Parkway was closed in 1937 and replaced by the Northern State Parkway (opened 1931) and the contiguous Grand Central Parkway (opened 1936). In Germany, construction of the Bonn-Cologne Autobahn began in 1929 and was opened in 1932 by Konrad Adenauer, then the mayor of Cologne.<ref>{{cite web |url = http://german.about.com/library/blgermyth08.htm |title = German Myth 8: Hitler and the Autobahn |work = German.about.com |url-status = dead |archive-url = https://web.archive.org/web/20060508183403/http://german.about.com/library/blgermyth08.htm |archive-date = 8 May 2006 |df = dmy-all }}</ref> Soon the Autobahn was the first limited-access, high-speed road network in the world, with the first section from Frankfurt am Main to Darmstadt opening in 1935.<ref>{{cite web | url=https://www.iamexpat.de/expat-info/driving-germany/german-autobahn#:~:text=With%20the%20opening%20of%20the%20first%20section%20between,to%20complete%201.000%20kilometres%20of%20road%20per%20year. | title=The German autobahn {{!}} Driving in Germany }}</ref>

In the US, the Federal 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 (the Pershing Map) was published. The Federal Aid Highway Act of 1956 allocated $25 billion for the construction of the {{convert|41000|mi|km|adj=mid|-long|order=flip}} Interstate Highway System over a 20-year period.<ref>{{cite web |url = https://highways.dot.gov/highway-history/interstate-system/50th-anniversary/history-interstate-highway-system |title = History of the Interstate Highway System |publisher = Federal Highway Administration |access-date = 10 April 2010 }}</ref>

In Great Britain, the Special Roads Act 1949 provided the legislative basis for roads for restricted classes of vehicles and non-standard or no speed limits applied (later mostly termed motorways but now with speed limits not exceeding 70&nbsp;mph);<ref>{{cite web |url = http://www.opsi.gov.uk/acts/acts1949/pdf/ukpga_19490032_en.pdf |title = Special Roads Act 1949 |work = Office of Public Sector Information }}</ref> 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 as ''special 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 the M1 motorway.<ref>{{cite web |url = http://www.ciht.org.uk/motorway/m1m10m45.htm |title = M1 London: Yorkshire Motorway, M10 and M45 |work = Motorway Archives |access-date = 10 April 2010 |url-status = dead |archive-url = https://web.archive.org/web/20100416080957/http://www.ciht.org.uk/motorway/m1m10m45.htm |archive-date = 16 April 2010 }}</ref>

== Design == === Classification === In the United States, Federal Highway Administration classifies highways into the following categories: * Principal arterial (freeways and expressways, and other), which can be further recognized in urban and rural forms * Minor arterial * Collector (major, minor), which can be further recognized in urban and rural forms * Local This classification is based on the concept of accessibility and mobility. High mobility roads are considered arterial roads, roads with high accessibility are considered local roads, while those balancing between mobility and accessibility are called collectors.<ref>{{cite book |title=Highway Functional Classification, Criteria and Procedures Concepts |url=https://gis.penndot.pa.gov/BPR_pdf_files/Documents/Traffic/Highway_Statistics/2023_FHWA_Functional_Classification_Guidelines.pdf |publisher=Federal Highway Administration |access-date=7 September 2025 |date=February 2023 |pages=2, 6}}</ref>

Similarly in Europe, the European Commission defines the road categories as:<ref>{{cite web |title=Road classification |url=https://road-safety.transport.ec.europa.eu/european-road-safety-observatory/statistics-and-analysis-archive/roads/road-classification_en |publisher=European Commission |access-date=7 September 2025 |language=en}}</ref> * Arterial / through traffic flow routes (motorways, express roads, and some urban ring roads) are roads with a flow function, which encourage efficient throughput of (long distance) motor vehicles and can be further divided to primary and local arterials. * Distributor roads are roads with an area distribution function which permits transition from residential, industrial, recreational areas to scattered destinations. These roads can be further divided to primary and local distributors. * Access roads are roads with an access function, allowing actual access to road-side properties.

=== Metrics === There are three speed performance measures for highways:<ref name="Roess2004">{{cite book |last1=Roess |first1=Roger P. |last2=Prassas |first2=Elena S. |last3=McShane |first3=William R. |title=Traffic engineering |date=2004 |publisher=Pearson/Prentice Hall |location=Upper Saddle River, N.J |isbn=0-13-142471-8 |edition=3rd}}</ref>{{rp|pp=728-730}} * Free-flow speed: a speed selected by most drivers when they are driving alone on the subject highway with green lights, but facing other restrictions such as pedestrians, parking, and road geometrics. Free-flow speed reflects the driving "environment" and may vary by the time of the day. * Running speed / average running speed: average vehicle speed while in motion, which might be {{cvt|5|-|10|mph}} slower than free flow speed. * Average travel speed: actual traveling speed, a metric used for determining the subject highway's level of service.

An additional metric involves delays. Control delays are delays caused by traffic control devices.<ref>{{cite web |title=4.5.1 Control Delay |url=https://www.txdot.gov/manuals/des/tsp/chapter-4-traffic-analysis-methodology--tools--and/4-5-moes/4-5-1-control-delay.html |website=Traffic and Safety Analysis Procedures Manual |publisher=Texas Department of Transportation |access-date=7 September 2025}}</ref> According to ''Highway Capacity Manual'', control delay at a signalized intersection may be calculated as a sum of uniform delay, incremental delay, and initial queue delay:<ref name="Roess2004" />{{rp|pp=730-731}} <math display="block">DELAY_{control} = DELAY_{uniform} + DELAY_{incremental} + DELAY_{initial\ queue} </math> where: * <math display="inline">DELAY_{uniform} = \frac{0.5C (1 - \frac{g}{C})^{2}}{1-min(1,X)\frac{g}{C}} \times f_{progression}</math> * <math display="inline">DELAY_{incremental} = 900T[(X-1) + \sqrt{(X-1)^2 + \frac{8kIX}{cT}}]</math> * <math display="inline">DELAY_{incremental}</math> = delay due to pre-existing queue before the next arrival, seconds per vehicle * <math display="inline">C</math> = cycle length, s * <math display="inline">g</math> = effective green time, s * <math display="inline">X</math> = volume-to-capacity ratio * <math display="inline">f_{progression}</math> = progression adjustment factor, to account for the timing of traffic arriving in platoon, and decreases as the platoon arrival performance increases<ref name="Roess2004" />{{rp|p=608}} * <math display="inline">T</math> = duration of analysis period, hour * <math display="inline">k</math> = incremental delay adjustment for actuated control * <math display="inline">I</math> = incremental delay adjustment for upstream signals filtering and equals to 1.0 when the intersection is isolated * <math display="inline">c</math> = capacity of the lane group, vehicle per hour

=== Preservation of highway functions === As local community grows, the function of the highway may get degraded. To maintain a good balance between accessibility and mobility, design methods such as access management, context sensitive design, transit-oriented development, travel demand management, and corridor management planning are used.<ref>{{cite web |last1=Hard |first1=Edwin N. |last2=Bochner |first2=Brian S. |last3=Li |first3=Yingfeng (Eric) |last4=Qi |first4=Yi (Grace) |last5=Damnjanovic |first5=Ivan |last6=Frawley |first6=William E. |title=Preserving The Functionality/Asset Value Of The State Highway System: Technical Report |url=https://library.ctr.utexas.edu/hostedpdfs/tti/0-6208-1.pdf |website=Texas Transportation Institute, Texas A&M University |date=February 2010}}</ref> Some of the enhancements are done during future rehabilitation projects after the highway constructions are finished, especially for the right-of-way arterial highways.<ref name="Roess2004" />{{rp|p=745}}

{{main|Frontage road}} To minimize local activities' disruptions to the arterial roads, some arterials have frontage road to separate from these activities.<ref name="Roess2004" />{{rp|p=744}}

== Social effects == [[File:Construction on Century Freeway overpass on Harbor Freeway.jpg|thumb|The construction of Harbor Freeway, and its subsequent displacement of homes in Los Angeles, California.{{cn|date=October 2024}}]]

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 release latent 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.

[[File:Home_Owners'_Loan_Corporation_Philadelphia_redlining_map.jpg|thumb|The use of "Redlining" often would dictate where in cities highways would go through.<ref>{{Cite web|url=https://www.lincolninst.edu/publications/articles/2023-05-five-ways-urban-planners-addressing-inequity|title=Five Ways Urban Planners Are Addressing a Legacy of Inequity |date=15 May 2023 |publisher=Lincoln Institute of Land Policy}}</ref>]]

Where highways are created through existing communities, there can be reduced community 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 from racist planning practices from before the advent of civil rights. This would result in the vast majority of displacement and social effects mostly going to people like African Americans.<ref>{{Cite web|url=https://www.npr.org/2021/04/07/984784455/a-brief-history-of-how-racism-shaped-interstate-highways|title=A Brief History Of How Racism Shaped Interstate Highways|first=Noel|last=King|publisher=NPR }}</ref>

In recent times, the use of freeway removal or the public policy of urban 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.<ref>{{Cite web|url=https://www.lincolninst.edu/publications/articles/2020-03-deconstruction-ahead-urban-highway-removal-changing-cities|title=How Urban Highway Removal Is Changing Our Cities|date=14 April 2020 |publisher=Lincoln Institute of Land Policy}}</ref>

== Economic effects == {{Main|Transport economics}} In transport, demand can be measured in numbers of journeys made or in total distance travelled across all journeys (e.g. passenger-kilometres for public transport or vehicle-kilometres of travel (VKT) for private transport). Supply is considered to be a measure of capacity. The price of the good (travel) is measured using the generalised cost of travel, which includes both money and time expenditure. [[File:Leipzig-Halle Airport Condor.jpg|thumb|right|A taxiway crossing the Autobahn, near Leipzig]]

The effect of increases in supply (capacity) are of particular interest in transport economics (see induced demand), as the potential environmental consequences are significant (see ''externalities'' below).

In addition to providing benefits to their users, transport networks impose both positive and negative 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 provide emergency services, increases in land value and agglomeration benefits. Negative externalities are wide-ranging and may include local air pollution, noise pollution, light pollution, safety hazards, community severance and congestion. The contribution of transport systems to potentially hazardous climate 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 negative externality by economists.<ref>{{Cite book |last1 = Small |first1 = Kenneth A. |first2 = José A. |last2 = Gomez-Ibañez |name-list-style = amp |year = 1998 |title = Road Pricing for Congestion Management: The Transition from Theory to Policy |publisher = The University of California Transportation Center, University of California at Berkeley |page = 213 }}</ref>

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."<ref>{{Cite journal |title = Roads and Innovation |journal = The Review of Economics and Statistics |volume = 99 |issue = 3 |pages = 417–434 |doi = 10.1162/REST_a_00619 |year = 2017 |last1 = Agrawal |first1 = Ajay |last2 = Galasso |first2 = Alberto |last3 = Oettl |first3 = Alexander |s2cid = 7268833 }}</ref> 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.<ref>{{Cite journal|last1=Fretz|first1=Stephan|last2=Parchet|first2=Raphaël|last3=Robert-Nicoud|first3=Frédéric|date=2021|title=Highways, Market Access, and Spatial Sorting*|url=https://doi.org/10.1093/ej/ueab070|journal=The Economic Journal|volume=132 |issue=643 |pages=1011–1036 |doi=10.1093/ej/ueab070|issn=0013-0133|hdl=10419/173046|hdl-access=free|url-access=subscription}}</ref>

== Environmental effects == thumb|Noise, light and air pollution are negative environmental effects highways can have on their surroundings. {{Main|Environmental impacts of roads}}

Highways are extended linear sources of pollution.

Roadway noise increases with operating speed so major highways generate more noise than arterial streets. Therefore, considerable noise health effects are expected from highway systems. Noise mitigation strategies exist to reduce sound levels at nearby sensitive receptors. The idea that highway design could be influenced by acoustical engineering considerations first arose about 1973.<ref>{{cite book |first = John |last = Shadely |title = Acoustical analysis of the New Jersey Turnpike widening project between Raritan and East Brunswick |publisher = Bolt Beranek and Newman |year = 1973 }}</ref><ref>{{cite conference |first = Michael |last = Hogan |title = Highway Noise |conference = 3rd Environmental Pollution Symposium, sponsored by AIAA, ACS, ASME, SAE |publisher = SRI International |location = Menlo Park, CA |date = 17–18 April 1973 }}</ref>

Air quality issues: Highways may contribute fewer emissions 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 have traffic congestion.

New highways can also cause habitat fragmentation, encourage urban 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 of public 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 encourage carpooling 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.<ref>{{cite web |url = http://grist.org/list/these-beautiful-bridges-are-just-for-animals/ |title = These beautiful bridges are just for animals |first = Jess |last = Zimmerman |date = 9 July 2012 }}</ref>

Highways may have some positive impact on nature only in the distant future: * They can prevent the spread of forest and steppe fires; * High-speed roads contribute to urbanization, in which millions of people move to richer large cities, and thousands of abandoned small impoverished settlements gradually disappear and become overgrown with dense forests;<ref>[https://www.australiangeographic.com.au/travel/2025/05/adventure-awaits-in-dubbo-and-the-great-western-plains/ Adventure awaits in Dubbo and the Great Western Plains]</ref><ref>[https://aif.ru/auto/roads/sploshnye_plyusy_razvitie_trass_razgruzit_goroda_i_uluchshit_ekologiyu Сплошные плюсы. Развитие трасс разгрузит города и улучшит экологию | Аргументы и Факты]</ref> * Thanks to expressways, not only the material well-being of the population of poorly developed countries is improving, but even its traditional culture is changing. Freed from age-old prejudices, highly educated and independent women in these countries tend not to burden themselves with heavy family responsibilities and rarely give birth to children, which is why the demography of the Earth may decrease, which will ease the burden on the ecology.

== Road traffic safety == {{Main|Road traffic safety}}

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 from traffic collisions. It includes the design, construction and regulation of the roads, the vehicles used on them and the training of drivers and other road-users.

A report published by the World 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<ref>{{cite web |url =https://www.who.int/violence_injury_prevention/publications/road_traffic/world_report/en/index.html |title = World report on road traffic injury prevention |publisher = World Health Organization |access-date = 14 April 2010 }}</ref> 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.<ref name=bbc>{{cite news |url = https://news.bbc.co.uk/2/hi/in_depth/7776127.stm |title = UN raises child accidents alarm |work = BBC News |date = 10 December 2008 }}</ref> For reasons of clear data collection, only harm involving a road vehicle is included.<ref name="National Motor Vehicle Crash Causation Survey">{{cite web |url = http://www-nrd.nhtsa.dot.gov/Pubs/811059.PDF |archive-url = https://web.archive.org/web/20090117181902/http://www-nrd.nhtsa.dot.gov/Pubs/811059.PDF |url-status = dead |archive-date = 17 January 2009 |title = National Motor Vehicle Crash Causation Survey |publisher = United States Department of Transportation |access-date = 7 August 2014 }}</ref> A person tripping with fatal consequences or dying for some unrelated reason on a public road is not included in the relevant statistics.

== Statistics == thumb|upright=0.7|International sign used widely in Europe denoting the start of special restrictions for a section of highway classed as a motorway [[File:M8-RUS.svg|thumb|100px|Russian Federal M8 highway sign]] [[File:CBX Parkchester 6 jeh.JPG|thumb|upright=0.75|The Cross Bronx Expressway in New York, United States uses asphalt and concrete pavement, both of which are popular road surfaces on highways.]]

The United States has the world's largest network of highways, including both the Interstate Highway System and the United 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,<ref>{{cite web | url=https://www.designingbuildings.co.uk/wiki/Top_10_most_expensive_construction_projects_in_the_world#:~:text=the%20project%20over.-,1.,expensive%20construction%20project%20to%20date | title=Top 10 most expensive construction projects in the world }}</ref> as the entirety of the Interstate Highway System was estimated to cost $27 billion in 1955 (equivalent to ${{formatprice|{{inflation|US-GDP|27000000000|1955|r=-6}}}} in {{inflation-year|US-GDP}}{{inflation-fn|US-GDP}}).<ref>{{Cite web |first = Richard |last = Weingroff |url=https://www.fhwa.dot.gov/infrastructure/target.cfm|title=Target: $27 Billion - The 1955 Estimate|work = Highway History |publisher = Federal Highway Administration}}</ref>

China's highway network is the second most extensive in the world, with a total length of about {{Convert|3,573,000|km|mi}}.<ref>{{cite news |url = http://uk.reuters.com/article/idUKPEK18598420071116 |archive-url = https://archive.today/20120730190327/http://uk.reuters.com/article/idUKPEK18598420071116 |url-status = dead |archive-date = 30 July 2012 |work = Reuters |title = China says needs extra million km of roads by 2020 |first = Emma |last = Graham-Harrison |date = 16 November 2007 }}</ref><ref name="China Nationa Bureau of Statistics 2007 Yearbook-Transport Section">{{cite web |url = http://www.stats.gov.cn/tjsj/ndsj/2008/html/P1503E.HTM |title = 15-3 Length of Transport Routes at Year-end by Region |publisher = China National Bureau of Statististcs |date = 2007 |access-date = 12 January 2013 }}</ref><ref>{{cite web |url = http://www.chinagate.cn/english/choice/50301.htm |title = China Has 3.48 Mln Km of Highways in Operation |publisher = Chinagate.cn |date = 6 March 2007 |access-date = 12 January 2013 |archive-url = https://web.archive.org/web/20130810000842/http://www.chinagate.cn/english/choice/50301.htm |archive-date = 10 August 2013 |url-status = dead }}</ref><ref>{{cite web |url = http://www.chinadaily.com.cn/bizchina/2008-01/07/content_6374334.htm |title = National highway target set for year |publisher = Chinadaily.com.cn |date = 7 January 2008 |access-date = 12 January 2013 }}</ref><ref>{{cite web |url = http://www.okokok.com.cn/Abroad/Class121/Class129/200812/121827.html |title = China Road Construction Report, 2007–2008 |publisher = Okokok.com.cn |date = 22 December 2008 |access-date = 12 January 2013 |archive-url = https://web.archive.org/web/20130809085805/http://www.okokok.com.cn/Abroad/Class121/Class129/200812/121827.html |archive-date = 9 August 2013 |url-status = dead }}</ref> China's expressway network is the longest Expressway system in the world, and it is quickly expanding, stretching some {{Convert|85,000|km|mi}} at the end of 2011.<ref>{{cite web |author = Staff |url = http://www.newgeography.com/content/002003-china-expressway-system-exceed-us-interstates |title = China Expressway System to Exceed US Interstates |date = 10 February 2011 |work = New Geography |access-date = 21 March 2014 }}</ref><ref>{{cite web |url = http://www.csytv.com/news/china/2011-12-31/116464.html |title = 中国高速公路总里程达8.5万公里 今年新增1.1万&nbsp;– 沈阳广播电视台官方网站&nbsp;– 沈阳电视台&nbsp;– 资讯潮流 趣味生活 尽在沈视网！ |publisher = Csytv.com |access-date = 12 January 2013 |url-status = dead |archive-url = https://web.archive.org/web/20130202052902/http://www.csytv.com/news/china/2011-12-31/116464.html |archive-date = 2 February 2013 }}</ref> In 2008 alone, {{Convert|6,433|km|mi}} expressways were added to the network.<ref>{{cite web |url = http://www.chinadaily.com.cn/china/2009-01/16/content_7403145.htm |title = More rural roads planned this year |work = China Daily |date = 16 January 2009 |access-date = 12 January 2013 |author = Xin Dingding }}</ref>

;Longest international highway: The Pan-American Highway, which connects many countries in the Americas, is nearly {{Convert|25,000|km|mi|-2}} long {{As of|2005|lc=on}}.{{Citation needed|date=August 2010}} The Pan-American Highway is discontinuous because there is a significant gap in it in southeastern Panama, where the rainfall is immense and the terrain is entirely unsuitable for highway construction. ;Longest national highway (point to point): The Trans-Canada Highway has one main route, a northern route through the western provinces, and several branches in the central and eastern provinces. The main route is {{convert|7,821|km|mi}} long {{As of|2006|lc=on}} alone, and the entire system is over {{convert|10,700|km|mi}} long. The TCH runs east–west across southern Canada, the populated portion of the country, and it connects many of the major urban centres along its route crossing all provinces, and reaching nearly all of their capital cities.<ref name=Canada>{{cite news |url = https://www.cbc.ca/archives/topic/trans-canada-highway-bridging-the-distance |title = Trans-Canada Highway: Bridging the Distance |access-date = 20 December 2006 |work = CBC Digital Archives }}</ref> The TCH begins on the east coast in Newfoundland, traverses that island, and crosses to the mainland by ferry. It crosses the Maritime Provinces of eastern Canada with a branch route serving the province of Prince Edward Island via a ferry and bridge. After crossing the remainder of the country's mainland, the highway reaches Vancouver, British Columbia on the Pacific coast, where a ferry continues it to Vancouver Island and the provincial capital of Victoria. Numeric designation is the responsibility of the provinces, and there is no single route number across the country. ;Longest national highway (circuit): Australia's Highway 1 at over {{convert|14,500|km|mi|-2}}.{{Citation needed|date=August 2010}} It runs almost the entire way around the country's coastline. With the exception of the Federal Capital of Canberra, which is far inland, Highway 1 links all of Australia's capital cities, although Brisbane and Darwin are not directly connected, but rather are bypassed short distances away. Also, there is a ferry connection to the island state of Tasmania, and then a stretch of Highway 1 that links the major towns and cities of Tasmania, including Launceston and Hobart (this state's capital city). ;Largest national highway system: The United States of America has approximately {{Convert|6.43|e6km|mi}} of highway within its borders {{As of|2008|lc=on}}.<ref>{{cite web |url = http://www.indexmundi.com/g/r.aspx?c=us&v=115 |title = Transportation: Roadways |author = Central Intelligence Agency |work = CIA World Factbook }}</ref> ;Busiest highway: Highway 401 in Ontario, Canada, has volumes surpassing an average of 500,000 vehicles per day in some sections of Toronto {{As of|2006|lc=on}}.<ref name=Ontario>{{cite web |title = Ontario government investing $401 million to upgrade Highway 401 |url = http://ogov.newswire.ca/ontario/GPOE/2002/08/06/c0057.html?lmatch=&lang=_e.html |access-date = 20 December 2006 |date = 6 August 2002 |author = Ministry of Transportation (Ontario) |archive-url = https://web.archive.org/web/20070914064434/http://ogov.newswire.ca/ontario/GPOE/2002/08/06/c0057.html?lmatch=&lang=_e.html |archive-date = 14 September 2007 }}</ref><ref name=Highway>{{cite news |url = http://www.urbanplanet.org/forums/index.php?showtopic=3459 |title = GTA Economy Dinged by Every Crash on the 401: North America's Busiest Freeway |first = Brian |last = Gray |newspaper = Toronto Sun |via = Urban Planet |date = 10 April 2004 |access-date = 18 March 2007 |quote = The 'phenomenal' number of vehicles on Hwy. 401 as it cuts through Toronto makes it the busiest freeway in North America... }}</ref> ;Widest highway (maximum number of lanes): The Katy Freeway (part of Interstate 10) in Houston, Texas, has a total of 26 lanes in some sections {{As of|2007|lc=on}}.{{Citation needed|date=August 2010}}<ref>{{cite web |url = http://www.inautonews.com/list-of-world-record-highways |title = List of World record highways |publisher = Inautonews.com |access-date = 21 March 2014 |archive-url = https://web.archive.org/web/20131111223514/http://www.inautonews.com/list-of-world-record-highways |archive-date = 11 November 2013 |url-status = dead |df = dmy-all }}</ref> However, they are divided up into general use/ frontage roads/ HOV lanes, restricting the traverse traffic flow. ;Widest highway (maximum number of through lanes): Interstate 5 along a {{convert|2|mi|km|adj=mid|-long|order=flip}} section between Interstate 805 and California State Route 56 in San Diego, California, which was completed in April 2007, is 22&nbsp;lanes wide.<ref>{{cite news |first = Steve |last = Schmidt |url = http://www.signonsandiego.com/uniontrib/20070328/news_1mi28merge.html |title = Four new southbound lanes at I-5/805 merge set to open |work = San Diego Union-Tribune |date = 28 March 2007 |url-status = dead |archive-url = https://web.archive.org/web/20110718110916/http://www.signonsandiego.com/uniontrib/20070328/news_1mi28merge.html |archive-date = 18 July 2011 }}</ref> ;Highest international highway: The Karakoram Highway, between Pakistan and China, is at an altitude of {{convert|4693|m|ft}}.{{Citation needed|date=August 2010}} ;Highest national highway: National Highway 5, in India, connecting Amritsar in Punjab with Manali in Himachal Pradesh & Leh in Ladakh, reaches an approximate altitude of {{convert|4900|m|ft}}.{{Citation needed|date=August 2010}} The highest motorable road passes through Umling La at an altitude of {{convert|5883|m|ft}} falls under the branch highway connecting National Highway 5 in India.{{cn|date=April 2025}}

== Bus lane == {{unreferenced section|date=December 2012}} [[File:Gyeongbu Expressway Bus Only Lane.JPG|thumb|Highway bus lane on Gyeongbu Expressway in South Korea]]

{| class="wikitable" |+Examples of highways with bus lanes !Country || Highway || Bus lanes (km) || Section !Notes |- | Australia || M2 Hills Motorway ||21.4|| Abbott Road–Beecroft Road (Sydney) | |- |Australia |Eastern Freeway |11 |Hoddle Street–Doncaster Park & 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 between Los Angeles Union Station and El Monte station (Los Angeles)<ref>{{Cite web|url=https://thesource.metro.net/tag/el-monte-busway/|title=El Monte Busway|date=30 October 2020|website=The Source}}</ref> |}

=== South Korea === In South Korea, in February 1995 a bus lane (essentially an HOV-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.

* On the dotted line, vehicles except buses can make a right turn and temporarily pass for joining. However, when the lanes are not open, it is treated as white dotted lines. * On the double-dotted line, bus-only is implemented even during hours other than commuting. Vehicles except for buses can temporarily pass for right turns and joining. However, when the dedicated vehicle is not operating hours, it is treated as a white dotted line. * On the solid line, vehicles except buses are prohibited from driving, but it is operated flexibly according to the time and day of the week. When it is not operating hours for exclusive vehicles, it is treated as a white solid line. *On the double line, buses will be operated even during hours other than commuting hours. However, if the cars are not operated, it will be treated as solid white lines.

=== Hong Kong === In Hong Kong, some highways are set up with bus lanes to solve the traffic congestion. {| class="wikitable" |- ! District || Highway || Section |- | Tuen Mun|| 20px Tuen Mun Road || So Kwun Wat to Sham Tseng |- | Sha Tin|| 20px Lion Rock Tunnel || The entry of the tunnel |}

=== Philippines === Traffic congestion was a principal problem in major roads and highways in the Philippines, especially in Metro Manila and other major cities. The government decided to set up some bus lanes in Metro Manila like in the Epifanio delos Santos Avenue.

== Gallery == <gallery mode="packed" heights="130"> File:Spaghetti-Junction-Crop.jpg|Gravelly Hill Interchange in Birmingham, England File:Autostrada del Sole - Italy - panoramio.jpg|Autostrada A1 runs through Italy linking some of the largest cities of the country: Milan, Bologna, Florence, Rome and Naples File:S1 1.JPG|A Polish expressway in Bielsko-Biała File:5, 70870 Kuopio, Finland - panoramio.jpg|National road 5 in Kuopio, Finland File:E4 Nyköpingsbro.jpg|E4 motorway with rest area outside Nyköping, Sweden File:Garching Bundesautobahn 9.jpg|Multi-lane Autobahn 9 in Munich, Germany File:A22 Autostrada - Brenner Pass from Verona to Bolzano (5994736833).jpg|Autostrada A22 runs through Po Valley and Alps linking Modena, Italy, to Brenner Pass, a mountain pass which forms the border between Italy and Austria File:Pan-American Highway-Mancora, Peru.jpg|The Pan-American Highway where it serves as the main street in Máncora, Peru File:PRC Expressway.jpg|A typical expressway in China File:S85(Guizhou) Duyun Direction Exit 332 close to G75.jpg|An expressway exit in Guizhou, China File:North Lantau Highway near Citygate (Hong Kong).jpg|North Lantau Highway in Hong Kong File:Delhi Gurgaon Toll Gate.jpg|32-lane toll plaza at Delhi-Gurgaon Expressway in Gurgaon, India File:HIghway Chennai Bangalore.jpg|Chennai-Bangalore Highway in India File:Express highway.jpg|Mumbai Pune Expressway, India File:Kordestan-Resalat-Hakim.jpg|A highway interchange in Tehran, Iran File:Tokyo EXP way.JPG|The Metropolitan Expressway in Tokyo, Japan File:Kuwait highway.jpg|A highway in Kuwait City, Kuwait File:Jisu IC in Namhae Expressway.JPG|Namhae Expressway in Jinju, South Korea File:The-Expressway at Ja-ela.jpg|Ja-Ela Interchange in the Airport Expressway(E03) in Ja-Ela, Sri Lanka File:Fort of Bard.JPG|Autostrada A5 connects Turin and the Aosta Valley (Italy) to France through the Mont Blanc Tunnel File:Dubai Roads on 1 May 2007.jpg|3/4 highway interchange in Dubai, United Arab Emirates </gallery>

== Highways by country == <!--Alphabetically by country:--> The following is a list of highways by country in alphabetical order. [[File:Renumbered National Highways map of India (Schematic).jpg|thumb|upright=1.15|National highways of India]] [[File:Italia - mappa rete autostradale.svg|thumb|upright=1.15|Autostrade (highways) of Italy]] * Algeria East–West Highway * Autobahns of Austria * ''Autoput'' and ''Autocesta'' {{small|(Bosnia and Herzegovina)}} * ''Rodovia'' {{small|(Brazil)}} * ''Avtomagistrala'' {{small|(Bulgaria, Ukraine)}} * Highways in Canada * Expressway {{small|(China)}} * ''Autocesta'' {{small|(Croatia)}} * ''Dálnice'' {{small|(Czech Republic)}} * ''Autostrada'' {{small|(Egypt, Poland, Romania)}} * ''Autoroute'' {{small|(France)}} * Autobahns of Germany * ''Aftokinitodromos'' {{small|(Greece)}} * ''Autópálya'' {{small|(Hungary)}} * National Highways and Expressways {{small|(India)}} * Motorway {{small|(Ireland)}} * List of highways in Israel * Autostrade of Italy {{small|(Italy)}} * ''Kōsokudōro'' {{small|(Japan)}} * ''Lebuhraya'' {{small|(Malaysia)}} * ''Autopista de Carretera Federal'' {{small|(Mexico)}} * ''Autoroute'' {{small|(Morocco)}} * ''Avtopat'' {{small|(North Macedonia)}} * ''Motorvei'' {{small|(Norway)}} * Motorways and National Highways of Pakistan * Philippine highway network * ''Autoestrada''&nbsp;<ref>Notable for the introduction of the world's first electronic toll collection system, the ''Via Verde''.</ref> {{small|(Portugal)}} * Russian federal highways {{small|(Russia)}} * ''Autoput'' {{small|(Serbia)}} * ''Avtocesta'' {{small|(Slovenia)}} * Expressways in South Korea * ''Autopista'' {{small|(Spain)}} * ''Motorväg'' {{small|(Sweden)}} * Autobahns of Switzerland * Freeways in Taiwan * Thai highway network {{small|(Thailand)}} * State Highways (Ukraine) {{small|(Ukraine)}} * Highways in the United Kingdom * ''Autofamba'' {{small|(Zimbabwe)}} {{Clear}}

== See also == <!-- PLEASE RESPECT ALPHABETICAL ORDER --> {{div col}} * Bypass route * Controlled-access highway * Divided highway (dual carriageway) <!--No explicit section on highways, roads: * Earthquake engineering--> * Freeway * Highway systems by country * Highwayman * Infrastructure * Limited-access road * List of roads and highways * Motorway * Parkway * Passing lane * Ring road * Road * Road junction * Road safety * Road transport * Roadway air dispersion modeling * Roadway noise * Toll road * Undivided highway (single carriageway) {{div col end}} {{clear}}

== References == {{Reflist}}

== External links == {{Wiktionary|highway}} {{Wikiquote}} {{Commons category|Highways}} * [http://www.elbruz.org/eroads/AGR_2.htm Full list of Euroroutes with distances] * [http://www.greenroads.org/ The Greenroads Rating System] {{Webarchive|url=https://web.archive.org/web/20150921040729/https://www.greenroads.org/ |date=21 September 2015 }} * [https://web.archive.org/web/20070303005314/http://www.kscourts.org/kscases/ctapp/1999/19991119/81647.htm Legal opinion, Kansas, US] * [http://transglobalhighway.com/ Proposed Trans-Global Highway] * [http://cornwallfreenews.com/2011/06/letter-to-the-editor-erhardt-peper-of-new-dundee-ontario-wants-an-ontario-super-highway-system-june-18-2011/ Ontario Super Highway Program (June 19, 2011)] * [https://www.youtube.com/watch?v=GMtusG5tuC8 Video of Highway 401 through Greater Toronto] * [https://www.gutenberg.org/ebooks/66482 Highways and Highway Transportation] by George R. Chatburn (1863-1940)

{{Road types}} {{Authority control}}

Category:Highways Category:Road infrastructure Category:Types of roads