What is highway used for?

A highway is any public or private road or other public way on land. It is used for major roads, but also includes other public roads and public tracks. In the United States, it is used as an equivalent term to controlled-access highway, or a translation for autobahn, autoroute, etc.

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.

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 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 of America. 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 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 progressively more modern highway systems to spur commerce and bolster national defence.

Major modern 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).

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" 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 types of traffic or combinations of types of traffic; usually a highway available to vehicles is available to foot or horse traffic, a highway available to horse traffic is available to pedestrians but exceptions can apply usually in the form of a highway only being available to vehicles or 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 as often will be the case with 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 Queen's Highway".

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, examples in recent years are commonly 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.

What is called 'highway' in the context of motor vehicles is called 'motorway' in the UK context.

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:

The word highway is itself no longer a statutory expression in Scots law 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"; 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. Highways generally have a route number designated by the state and federal departments of transportation.

California Vehicle Code, Sections 360, 590, define a "highway" as only a way open for use of 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, California, are "highways" that are entitled to be maintained with state highway funds.

Modern highway systems developed in the 20th century as the automobile gained popularity. The first United States limited access road was constructed on Long Island New York known as the Long Island Motor Parkway or the Vanderbilt Motor Parkway. It was completed in 1911.

In Italy the Milano-Varese 49-kilometre-long (30 mi) autostrada was opened in 1924.

Construction of the Bonn–Cologne autobahn began in 1929 and it was opened in 1932 by the mayor of Cologne, Konrad Adenauer.

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 66,000-kilometre-long (41,000 mi) Interstate Highway System over a 20-year period.

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 mph); 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.

Reducing travel times relative to city or town streets, modern highways with limited access and grade separation create increased opportunities for people to travel for business, trade or pleasure and also provide trade routes for goods. Modern highways 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.

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.

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.

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.

A 2016 study finds 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." 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.

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.

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.

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 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. For reasons of clear data collection, only harm involving a road vehicle is included. 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 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.

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). China's expressway 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. In 2008 alone, 6,433 kilometres (3,997 mi) expressways were added to the network.

Some countries incorporate bus lanes onto highways.

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.

In Hong Kong, some highways are set up with bus lanes to solve the traffic congestion.

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.

Highways form an integrated network of well-maintained thoroughfares that promote the interruption-free flow of commuter traffic, goods transport, and vacation traffic around cities, states, and the country. They are important to minimize traffic delays, interconnect cities, and even connect rural communities across the nation.

There are 4 main types of highways in most countries. National highways are large roadways built to ease the transport of people and goods across the nation. Interstate highways connect neighboring states, state highways promote travel locally within a state. County highways are mostly rural.

Types of highways can be known by various names in different countries, but the principles stay the same. The quality of the highway and the entity responsible for the upkeep of the highway will differ for each highway type.

National highways are usually the major, multi-lane routes that span large distances across the country. These routes are known by various names in different countries. These routes are known as Inter-state highways in the US, but inter-state has a different meaning in other parts of the world.

The main highways are planned, funded, built, and administered by the national government in most nations. The local state, or province, is tasked with the upkeep and maintenance of the national highways that fall within the boundaries of the state or province.

The national government may, but not always, offer funding for maintenance of the roads to the regions tasked with maintenance.

The quality of these roads is usually superior to all the other highway types. The design usually includes multiple lanes in each direction to promote ease of traffic flow and high speeds on the good quality road surface.

National highways generally have controlled access and fewer entrance and exit points than other highway types. National highways will often be directed around the outskirts of major cities. They may become part of the urban access to the city, with smaller highways diverging from or converging with the national route.

These convergence and divergence interconnections can result in complex interchanges between the highway types.

National highways, other than around cities where they can become congested, are also intended to promote a free flow of traffic, which saves on wear-and-tear and fuel costs on transport vehicles. The lack of stop/start driving on these routes helps in this regard.

The road surface on these highways can be asphalt, but the high traffic zones commonly use concrete for the road surface.

Concrete is harder-wearing of high traffic and heavy loads than asphalt, making it the surface of choice in high traffic zones on national highways or inter-states as they are known in the USA.

The Autobahn in Germany is a famous national highway that, in certain sections, has no upper-speed limit for certain classes of motor vehicles.

In the USA, national highways are known as interstate highways, but in other parts of the world, interstate highways are smaller highways that connect smaller cities that the national highways bypass.

Smaller inter-state highways connect neighboring states to promote commerce and trade between the states, where the national highways do not reach.

The planning, funding, design, and building of these highways is normally the state’s responsibility or a collaboration between states, which does not include the national government.

The administration, upkeep, and maintenance of these roads are usually done via the state, and state funds are used for this purpose.

Some of these inter-state highways can carry extremely large traffic volumes if the area and commerce warrant the traffic. This has led to many of these provincial or state-controlled highways being of similar standard and quality to the national highways.

However, many other inter-state highways are smaller roadways, with single lanes of traffic going each way, but still with a good quality surface to promote travel at higher speeds.

The road surface of inter-state highways can be concrete or asphalt or combinations thereof, depending on how heavy or light the traffic is on the section of the highway.

State highways are smaller than inter-state highways and generally connect smaller towns in a state with each other, or a larger city, or state capitol.

The quality of these roads is generally determined by how important the town or highway is to the state’s commerce. As with interstate highways, many of these highways can be of the same size and quality and national highways routes, depending on the level of traffic on the highway, needs to cater to.

Likewise, the quality of the surface will vary greatly, from national highway-quality surface to poorly maintained single-lane roadways to smaller towns and cities.

State highway surfaces are more commonly asphalt than concrete. Asphalt is cheaper, making more sense for states that do not have large budgets for road building. Some state highways around larger cities may use concrete surfaces, but this will normally be in zones where heavy vehicles traverse the highway.

County highways have a wide range in size and surfaces, varying from large double-lane highways to gravel roads.

County highways connect smaller, often rural towns and settlements and are used primarily by the agriculture sector. The construction and maintenance of these county highways are normally created from the county budget, and consequently, often reflect the level of commerce and income within the county.

The condition of these roads can be variable, depending on the available funds in the county and the equipment available to maintain the roads. Potholes are a frequent hazard on the smaller county roads.

Gravel roads are often easier to maintain, which is why many rural counties opt to keep the road surface as gravel rather than laying down a blacktop, which has a high capital outlay and high ongoing maintenance costs.

These highways are often policed by local sheriff offices rather than highway patrol.

Many countries upgrade their old national highways and routes, but these older highways are still in place and maintained because they still serve a purpose or have historical value.

In the USA, highways that fall into this category are the US Route 21, a north-south route spanning 394 miles, and the famous US Route 66, built in 1926.

Route 66 is an east-west route and is considered a national treasure. Many people from around the world visit the USA to travel Route 66 as tourists.

Conclusion Highways are constructed from different materials and using different designs, depending on their intended purpose and the traffic volumes they are intended to carry.

From the unlimited high speeds of the Autobahn to a small county gravel surface highway, each has its own peculiar charm.

• National highways.
• State highways.
• District roads.
• Rural roads or village roads.

Highways are usually the quickest route for driving between one city and another. Highways were originally built to connect cities and towns, and since they're wide and have high speed limits, they decreased the travel time.