Traffic
Overview
 
Traffic on roads may consist of pedestrian
Pedestrian
A pedestrian is a person traveling on foot, whether walking or running. In some communities, those traveling using roller skates or skateboards are also considered to be pedestrians. In modern times, the term mostly refers to someone walking on a road or footpath, but this was not the case...

s, ridden or herded animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...

s, vehicle
Vehicle
A vehicle is a device that is designed or used to transport people or cargo. Most often vehicles are manufactured, such as bicycles, cars, motorcycles, trains, ships, boats, and aircraft....

s, streetcars and other conveyances, either singly or together, while using the public way for purposes of travel. Traffic laws
Traffic code
Traffic code refers to the collection of local statutes, regulations, ordinances and rules that have been officially adopted in the United States to govern the orderly operation and interaction of motor vehicles, bicycles, pedestrians and others upon the public ways.The traffic code generally...

 are the law
Law
Law is a system of rules and guidelines which are enforced through social institutions to govern behavior, wherever possible. It shapes politics, economics and society in numerous ways and serves as a social mediator of relations between people. Contract law regulates everything from buying a bus...

s which govern traffic and regulate vehicles, while rules of the road are both the laws and the informal rules
Norm (sociology)
Social norms are the accepted behaviors within a society or group. This sociological and social psychological term has been defined as "the rules that a group uses for appropriate and inappropriate values, beliefs, attitudes and behaviors. These rules may be explicit or implicit...

 that may have developed over time to facilitate the orderly and timely flow of traffic.

Organized traffic generally has well-established priorities, lanes, right-of-way, and traffic control at intersection
Intersection (road)
An intersection is a road junction where two or more roads either meet or cross at grade . An intersection may be 3-way - a T junction or fork, 4-way - a crossroads, or 5-way or more...

s.

Traffic is formally organized in many jurisdictions, with marked lane
Lane
A lane is a part of the roadway within a road marked out for use by a single line of vehicles in such a way as to control and guide drivers for the purpose of reducing traffic conflicts. Most public roads have at least two lanes, one for traffic in each direction, separated by Lane markings...

s, junction
Junction (traffic)
A junction, when discussed in the context of transport, is a location where traffic can change between different routes, directions, or sometimes modes, of travel.-Historical significance:...

s, intersections
Intersection (road)
An intersection is a road junction where two or more roads either meet or cross at grade . An intersection may be 3-way - a T junction or fork, 4-way - a crossroads, or 5-way or more...

, interchange
Interchange (road)
In the field of road transport, an interchange is a road junction that typically uses grade separation, and one or more ramps, to permit traffic on at least one highway to pass through the junction without directly crossing any other traffic stream. It differs from a standard intersection, at which...

s, traffic signals, or sign
Traffic sign
Traffic signs or road signs are signs erected at the side of roads to provide information to road users. With traffic volumes increasing over the last eight decades, many countries have adopted pictorial signs or otherwise simplified and standardized their signs to facilitate international travel...

s.
Encyclopedia
Traffic on roads may consist of pedestrian
Pedestrian
A pedestrian is a person traveling on foot, whether walking or running. In some communities, those traveling using roller skates or skateboards are also considered to be pedestrians. In modern times, the term mostly refers to someone walking on a road or footpath, but this was not the case...

s, ridden or herded animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...

s, vehicle
Vehicle
A vehicle is a device that is designed or used to transport people or cargo. Most often vehicles are manufactured, such as bicycles, cars, motorcycles, trains, ships, boats, and aircraft....

s, streetcars and other conveyances, either singly or together, while using the public way for purposes of travel. Traffic laws
Traffic code
Traffic code refers to the collection of local statutes, regulations, ordinances and rules that have been officially adopted in the United States to govern the orderly operation and interaction of motor vehicles, bicycles, pedestrians and others upon the public ways.The traffic code generally...

 are the law
Law
Law is a system of rules and guidelines which are enforced through social institutions to govern behavior, wherever possible. It shapes politics, economics and society in numerous ways and serves as a social mediator of relations between people. Contract law regulates everything from buying a bus...

s which govern traffic and regulate vehicles, while rules of the road are both the laws and the informal rules
Norm (sociology)
Social norms are the accepted behaviors within a society or group. This sociological and social psychological term has been defined as "the rules that a group uses for appropriate and inappropriate values, beliefs, attitudes and behaviors. These rules may be explicit or implicit...

 that may have developed over time to facilitate the orderly and timely flow of traffic.

Organized traffic generally has well-established priorities, lanes, right-of-way, and traffic control at intersection
Intersection (road)
An intersection is a road junction where two or more roads either meet or cross at grade . An intersection may be 3-way - a T junction or fork, 4-way - a crossroads, or 5-way or more...

s.

Traffic is formally organized in many jurisdictions, with marked lane
Lane
A lane is a part of the roadway within a road marked out for use by a single line of vehicles in such a way as to control and guide drivers for the purpose of reducing traffic conflicts. Most public roads have at least two lanes, one for traffic in each direction, separated by Lane markings...

s, junction
Junction (traffic)
A junction, when discussed in the context of transport, is a location where traffic can change between different routes, directions, or sometimes modes, of travel.-Historical significance:...

s, intersections
Intersection (road)
An intersection is a road junction where two or more roads either meet or cross at grade . An intersection may be 3-way - a T junction or fork, 4-way - a crossroads, or 5-way or more...

, interchange
Interchange (road)
In the field of road transport, an interchange is a road junction that typically uses grade separation, and one or more ramps, to permit traffic on at least one highway to pass through the junction without directly crossing any other traffic stream. It differs from a standard intersection, at which...

s, traffic signals, or sign
Traffic sign
Traffic signs or road signs are signs erected at the side of roads to provide information to road users. With traffic volumes increasing over the last eight decades, many countries have adopted pictorial signs or otherwise simplified and standardized their signs to facilitate international travel...

s. Traffic is often classified by type: heavy motor vehicle (e.g., car
Čar
Čar is a village in the municipality of Bujanovac, Serbia. According to the 2002 census, the town has a population of 296 people.-References:...

, truck
Truck
A truck or lorry is a motor vehicle designed to transport cargo. Trucks vary greatly in size, power, and configuration, with the smallest being mechanically similar to an automobile...

); other vehicle (e.g., moped
Moped
Mopeds are a type of low-powered motorcycle designed to provide economical and relatively safe transport with minimal licensing requirements.Mopeds were once all equipped with bicycle-like pedals , but moped has been increasingly applied by governments to vehicles without pedals, based on their...

, bicycle
Bicycle
A bicycle, also known as a bike, pushbike or cycle, is a human-powered, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A person who rides a bicycle is called a cyclist, or bicyclist....

); and pedestrian
Pedestrian
A pedestrian is a person traveling on foot, whether walking or running. In some communities, those traveling using roller skates or skateboards are also considered to be pedestrians. In modern times, the term mostly refers to someone walking on a road or footpath, but this was not the case...

. Different classes may share speed limit
Speed limit
Road speed limits are used in most countries to regulate the speed of road vehicles. Speed limits may define maximum , minimum or no speed limit and are normally indicated using a traffic sign...

s and easement, or may be segregated. Some jurisdictions may have very detailed and complex rules of the road while others rely more on drivers' common sense and willingness to cooperate.

Organization typically produces a better combination of travel safety and efficiency. Events which disrupt the flow and may cause traffic to degenerate into a disorganized mess include: road construction, collisions
Car accident
A traffic collision, also known as a traffic accident, motor vehicle collision, motor vehicle accident, car accident, automobile accident, Road Traffic Collision or car crash, occurs when a vehicle collides with another vehicle, pedestrian, animal, road debris, or other stationary obstruction,...

 and debris in the roadway. On particularly busy freeways, a minor disruption may persist in a phenomenon known as traffic wave
Traffic wave
Traffic waves, also called stop waves or traffic shocks, are travelling disturbances in the distribution of cars on a highway. Traffic waves usually travel backwards in relation to the motion of the cars themselves, or "upstream". The waves can also travel downstream, however, more commonly become...

s. A complete breakdown of organization may result in traffic jams and gridlock
Gridlock
The term gridlock is defined as "A state of severe road congestion arising when continuous queues of vehicles block an entire network of intersecting streets, bringing traffic in all directions to a complete standstill; a traffic jam of this kind." The term originates from a situation possible in...

. Simulations of organized traffic frequently involve queuing theory, stochastic process
Stochastic process
In probability theory, a stochastic process , or sometimes random process, is the counterpart to a deterministic process...

es and equations of mathematical physics
Mathematical physics
Mathematical physics refers to development of mathematical methods for application to problems in physics. The Journal of Mathematical Physics defines this area as: "the application of mathematics to problems in physics and the development of mathematical methods suitable for such applications and...

 applied to traffic flow
Traffic flow
Traffic flow, in mathematics and civil engineering, is the study of interactions between vehicles, drivers, and infrastructure , with the aim of understanding and developing an optimal road network with efficient movement of traffic and minimal traffic congestion problems.-History:Attempts to...

.

Traffic in English is taken from the Arabic word taraffaqa, which means to walk along slowly together.

Rules of the road

Rules of the road are the general practices and procedures that road
Road
A road is a thoroughfare, route, or way on land between two places, which typically has been paved or otherwise improved to allow travel by some conveyance, including a horse, cart, or motor vehicle. Roads consist of one, or sometimes two, roadways each with one or more lanes and also any...

 users are required to follow. These rules usually apply to all road users, though they are of special importance to motorists
Motor vehicle
A motor vehicle or road vehicle is a self-propelled wheeled vehicle that does not operate on rails, such as trains or trolleys. The vehicle propulsion is provided by an engine or motor, usually by an internal combustion engine, or an electric motor, or some combination of the two, such as hybrid...

 and cyclists
Bicycle
A bicycle, also known as a bike, pushbike or cycle, is a human-powered, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A person who rides a bicycle is called a cyclist, or bicyclist....

. These rules govern interactions between vehicles and with pedestrian
Pedestrian
A pedestrian is a person traveling on foot, whether walking or running. In some communities, those traveling using roller skates or skateboards are also considered to be pedestrians. In modern times, the term mostly refers to someone walking on a road or footpath, but this was not the case...

s. The basic traffic rules are defined by an international treaty under the authority of the United Nations
United Nations
The United Nations is an international organization whose stated aims are facilitating cooperation in international law, international security, economic development, social progress, human rights, and achievement of world peace...

, the 1968 Vienna Convention on Road Traffic
Vienna Convention on Road Traffic
The Vienna Convention on Road Traffic is an international treaty designed to facilitate international road traffic and to increase road safety by standardising the uniform traffic rules among the contracting parties...

. Not all countries are signatory to the convention and, even among signatories, local variations in practice may be found. There are also unwritten local rules of the road, which are generally understood by local drivers.

As a general rule, drivers are expected to avoid a collision with another vehicle and pedestrians, regardless of whether or not the applicable rules of the road allow them to be where they happen to be.

In addition to the rules applicable by default, traffic sign
Traffic sign
Traffic signs or road signs are signs erected at the side of roads to provide information to road users. With traffic volumes increasing over the last eight decades, many countries have adopted pictorial signs or otherwise simplified and standardized their signs to facilitate international travel...

s and traffic light
Traffic light
Traffic lights, which may also be known as stoplights, traffic lamps, traffic signals, signal lights, robots or semaphore, are signalling devices positioned at road intersections, pedestrian crossings and other locations to control competing flows of traffic...

s must be obeyed, and instructions may be given by a police officer, either routinely (on a busy crossing instead of traffic lights) or as road traffic control around a construction zone, accident, or other road disruption.

These rules should be distinguished from the mechanical procedures required to operate one's vehicle. See driving
Driving
Driving is the controlled operation and movement of a land vehicle, such as a car, truck or bus.Although direct operation of a bicycle and a mounted animal are commonly referred to as riding, such operators are legally considered drivers and are required to obey the rules of the road...

.

Directionality

Traffic going in opposite directions should be separated in such a way that they do not block each other's way. The most basic rule is whether to use the left or right side of the road.

Traffic regulations

In many countries, the rules of the road are codified, setting out the legal requirements and punishments for breaking them.

In the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

, the rules are set out in the Highway Code
Highway Code
The Highway Code is the official road user guide for Great Britain. In Northern Ireland the applies while the Republic of Ireland has its own Rules of the Road. It contains 306 numbered rules and 9 annexes covering pedestrians, animals, cyclists, motorcyclists and drivers...

, which includes obligations but also advice on how to drive sensibly and safely.

In the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, traffic laws are regulated by the states and municipalities through their respective traffic code
Traffic code
Traffic code refers to the collection of local statutes, regulations, ordinances and rules that have been officially adopted in the United States to govern the orderly operation and interaction of motor vehicles, bicycles, pedestrians and others upon the public ways.The traffic code generally...

s. Most of these are based at least in part on the Uniform Vehicle Code
Uniform Vehicle Code
The Uniform Vehicle Code is a privately prepared set of United States traffic laws prepared by the National Committee on Uniform Traffic Laws and Ordinances, a private non-profit organization. Most of the members are state governments, in addition to some related organizations. The extent to which...

, but there are variations from state to state. In states such as Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...

, traffic law and criminal law
Criminal law
Criminal law, is the body of law that relates to crime. It might be defined as the body of rules that defines conduct that is not allowed because it is held to threaten, harm or endanger the safety and welfare of people, and that sets out the punishment to be imposed on people who do not obey...

 are separate, therefore, unless someone flees a scene of an accident, commits vehicular homicide or manslaughter, they are only guilty of a minor traffic offense. However, states such as South Carolina
South Carolina
South Carolina is a state in the Deep South of the United States that borders Georgia to the south, North Carolina to the north, and the Atlantic Ocean to the east. Originally part of the Province of Carolina, the Province of South Carolina was one of the 13 colonies that declared independence...

 have completely criminalized their traffic law, so, for example, you are guilty of a misdemeanor simply for travelling 5 miles over the speed limit.

Priority (right of way)

Vehicles often come into conflict with other vehicles and pedestrians because their intended courses of travel intersect, and thus interfere with each other's routes. The general principle that establishes who has the right to go first is called "right of way", or "priority". It establishes who has the right to use the conflicting part of the road and who has to wait until the other does so.

Signs, signals, markings and other features are often used to make priority explicit. Some signs, such as the stop sign
Stop sign
A Stop sign is a traffic sign to notify drivers that they must stop before proceeding.-Specifications:The Vienna Convention on Road Signs and Signals proposed standard stop sign diameters of 0.6, 0.9 or 1.2 metres. UK and New Zealand stop signs are 750, 900 or 1200 mm, according to sign...

, are nearly universal. When there are no signs or markings, different rules are observed depending on the location. These default priority rules differ between countries, and may even vary within countries. Trends toward uniformity are exemplified at an international level by the Vienna Convention on Road Signs and Signals
Vienna Convention on Road Signs and Signals
The Vienna Convention on Road Signs and Signals is an international treaty designed to increase road safety and aid international road traffic by standardising the signing system for road traffic in use internationally.This convention was agreed upon by the United Nations Economic and Social...

, which prescribes standardized traffic control devices
Road traffic control device
Traffic Control Devices are markers, signs and signal devices used to inform, guide and control the traffic and the pedestrians. These devices are usually placed adjacent, over and/or along the highways, roads, traffic facilities and other public areas that require traffic control.The most popular...

 (signs, signals, and markings) for establishing the right of way where necessary.

Crosswalks (or pedestrian crossings) are common in populated areas, and may indicate that pedestrians have priority over vehicular traffic. In most modern cities, the traffic signal is used to establish the right of way on the busy roads. Its primary purpose is to give each road a duration of time in which its traffic may use the intersection in an organized way. The intervals of time assigned for each road may be adjusted to take into account factors such as difference in volume of traffic, the needs of pedestrians, or other traffic signals. Pedestrian crossings may be located near other traffic control devices; if they are not also regulated in some way, vehicles must give priority to them when in use. Traffic on a public road usually has priority over other traffic such as traffic emerging from private access; rail crossings and drawbridge
Drawbridge
A drawbridge is a type of movable bridge typically associated with the entrance of a castle surrounded by a moat. The term is often used to describe all different types of movable bridges, like bascule bridges and lift bridges.-Castle drawbridges:...

s are typical exceptions.

Uncontrolled traffic

Uncontrolled traffic comes in the absence of lane markings and traffic control signals
Traffic light
Traffic lights, which may also be known as stoplights, traffic lamps, traffic signals, signal lights, robots or semaphore, are signalling devices positioned at road intersections, pedestrian crossings and other locations to control competing flows of traffic...

. On road
Road
A road is a thoroughfare, route, or way on land between two places, which typically has been paved or otherwise improved to allow travel by some conveyance, including a horse, cart, or motor vehicle. Roads consist of one, or sometimes two, roadways each with one or more lanes and also any...

s without marked lanes, drivers tend to keep to the appropriate side if the road is wide enough. Drivers frequently overtake others. Obstructions are
common.

Intersections have no signals or signage, and a particular road at a busy intersection may be dominant – that is, its traffic flows – until a break in traffic, at which time the dominance shifts to the other road where vehicles are queued. At the intersection of two perpendicular roads, a traffic jam may result if four vehicles face each other side-on.

Turning

Drivers will often want to cease to travel a straight line and turn onto another road or onto private property. The vehicle's directional signals (blinkers) are often used as a way to announce one's intention to turn, thus alerting other drivers. The actual usage of blinkers varies greatly amongst countries, although its purpose should be the same in all countries: to indicate a driver's intention to depart from the current (and natural) flow of traffic well before the departure is executed (typically 3 seconds as a guideline).

This will usually mean that turning traffic will have to stop in order to wait for a breach to turn, and this might cause inconvenience for drivers that follow them but do not want to turn. This is why dedicated lanes and protected traffic signals for turning are sometimes provided. On busier intersections where a protected lane would be ineffective or cannot be built, turning may be entirely prohibited, and drivers will be required to "drive around the block" in order to accomplish the turn. Many cities employ this tactic quite often; in San Francisco, due to its common practice, making three right turns is known colloquially as a "San Francisco left turn". Likewise, as many intersections in Taipei City are too busy to allow direct left turns, signs often direct drivers to drive around the block to turn.

Turning rules are by no means universal. In New Zealand, for example, left turning traffic must give way to opposing "right turning" traffic, i.e., traffic turning into a driver's path (unless there are multiple lanes to turn into). New Zealand will abolish this particular rule on 25 March 2012. NZ Officials estimate the change will prevent 1 death, 13 serious injuries and 84 minor injuries each year.

On roads with multiple lanes, turning traffic is generally expected to move to the lane closest to the direction they wish to turn. For example, traffic intending to turn right will usually move to the rightmost lane before the intersection. Likewise, left-turning two rightmost lanes will be of authority; for example, it is common for drivers to observe (and trust) the turn signals used by other drivers in order to make turns from other lanes. For example if several vehicles on the right lane are all turning right, a vehicle may come from the next-to-right lane and turn right as well, doing so in parallel with the other right-turning vehicles.

Intersections

In most of Continental Europe
Continental Europe
Continental Europe, also referred to as mainland Europe or simply the Continent, is the continent of Europe, explicitly excluding European islands....

, the default rule is to give priority to the right
Priority to the right
Priority to the right is a right-of-way system, in which a driver of a vehicle shall give way to vehicles approaching from the right at intersections...

, but this may be overridden by signs or road markings, and does not apply at T-shaped junctions in some of these countries, such as France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

. There, priority was initially given according to the social rank of each traveler, but early in the life of the automobile
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...

 this rule was deemed impractical and replaced with the priorité à droite (priority to the right) rule, which still applies. At a traffic circle
Traffic circle
A traffic circle or rotary is a type of circular intersection in which traffic must travel in one direction around a central island. In some countries, traffic entering the circle has the right-of-way and drivers in the circle must yield. In many other countries, traffic entering the circle must...

 where priorité à droite is not overridden, traffic on what would otherwise be a roundabout
Roundabout
A roundabout is the name for a road junction in which traffic moves in one direction around a central island. The word dates from the early 20th century. Roundabouts are common in many countries around the world...

 gives way to traffic entering the circle. Most French roundabouts now have give-way signs for traffic entering the circle, but there remain some notable exceptions that operate on the old rule, such as the Place de l'Étoile
Place de l'Étoile
The Place Charles de Gaulle, , historically known as the Place de l'Étoile , is a large road junction in Paris, France, the meeting point of twelve straight avenues including the Champs-Élysées which continues to the east. It was renamed in 1970 following the death of General and President Charles...

 around the Arc de Triomphe
Arc de Triomphe
-The design:The astylar design is by Jean Chalgrin , in the Neoclassical version of ancient Roman architecture . Major academic sculptors of France are represented in the sculpture of the Arc de Triomphe: Jean-Pierre Cortot; François Rude; Antoine Étex; James Pradier and Philippe Joseph Henri Lemaire...

. Traffic at this intersection is so chaotic that French insurance companies deem any accident on the roundabout to be equal liability. Priority to the right where used in continental Europe may be overridden by an ascending hierarchy of markings, signs, signals, and authorized persons.

In the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

, priority is always indicated by signs or markings, so that every junction between public roads (except those governed by traffic signals) has a concept of a major road and minor road. The default give-way-to-the-right rule used in Continental Europe causes problems for many British and Irish
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...

 drivers who are accustomed to having right of way by default unless they are specifically told to give way.

Other countries use various methods similar to the above examples to establish the right of way at intersections. For example, in most of the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, the default priority is to yield to traffic from the right, but this is usually overridden by traffic control devices or other rules, like the boulevard rule
Boulevard rule
The boulevard rule is a principle in United States traffic law which states that the driver of a vehicle entering a highway from a smaller road or entrance must stop and yield the right of way to all oncoming highway traffic...

. This rule holds that traffic entering a major road from a smaller road or alley must yield to the traffic of the busier road, but signs are often still posted. The boulevard rule can be compared with the above concept of a major and minor road, or the priority roads that may be found in countries that are parties to the Vienna Convention on Road Signs and Signals.

Perpendicular intersections
Also known as a "four-way" intersection, this intersection is the most common configuration for roads that cross each other, and the most basic type.

If traffic signals do not control a 4-way intersection, signs or other features are typically used to control movements and make clear priorities. The most common arrangement is to indicate that one road has priority over the other, but there are complex cases where all traffic approaching an intersection must yield and may be required to stop.

In the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

, and Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

, there are four-way intersections with a stop sign
Stop sign
A Stop sign is a traffic sign to notify drivers that they must stop before proceeding.-Specifications:The Vienna Convention on Road Signs and Signals proposed standard stop sign diameters of 0.6, 0.9 or 1.2 metres. UK and New Zealand stop signs are 750, 900 or 1200 mm, according to sign...

 at every entrance, called four-way stops. A failed signal or a flashing red light is equivalent to a four-way stop, or an all-way stop
All-way stop
An all-way stop is an intersection system used predominantly in the United States of America, Canada and South Africa where traffic approaching it from all directions is required to stop before proceeding through the intersection...

. Special rules for four-way stops may include:
  1. In the countries that use four-way stops, pedestrians always have priority at crosswalks – even at unmarked ones, which exist as the logical continuations of the sidewalks at every intersection with approximately right angles – unless signed or painted otherwise.
  2. Whichever vehicle first stops at the stop line – or before the crosswalk, if there is no stop line – has priority.
  3. If two vehicles stop at the same time, priority is given to the vehicle on the right.
  4. If three vehicles stop at the same time, priority is given to the two vehicles going in opposite directions, if possible.
  5. If four vehicles stop, drivers usually use gestures and other communication to establish right-of-way.


In Europe and other places, there are similar intersections. These may be marked by special signs (according to the Vienna Convention on Road Signs and Signals
Vienna Convention on Road Signs and Signals
The Vienna Convention on Road Signs and Signals is an international treaty designed to increase road safety and aid international road traffic by standardising the signing system for road traffic in use internationally.This convention was agreed upon by the United Nations Economic and Social...

), a danger sign with a black X representing a crossroads. This sign informs drivers that the intersection is uncontrolled and that default rules apply. In Europe and in many areas of North America the default rules that apply at uncontrolled four-way intersections are almost identical:
  1. Rules for pedestrians differ by country, in the United States and Canada pedestrians generally have priority at such an intersection.
  2. All vehicles must give priority to any traffic approaching from their right,
  3. Then, if the vehicle is turning right or continuing on the same road it may proceed.
  4. Vehicles turning left must also give priority to traffic approaching from the opposite direction, unless that traffic is also turning left.
  5. If the intersection is congested, vehicles must alternate directions and/or circulate priority to the right one vehicle at a time.

Pedestrian crossings

Pedestrian
Pedestrian
A pedestrian is a person traveling on foot, whether walking or running. In some communities, those traveling using roller skates or skateboards are also considered to be pedestrians. In modern times, the term mostly refers to someone walking on a road or footpath, but this was not the case...

s must often cross from one side of a road to the other, and in doing so may come into the way of vehicles traveling on the road. In many places pedestrians are entirely left to look after themselves, that is, they must observe the road and cross when they can see that no traffic will threaten them. Busier cities usually provide pedestrian crossings, which are strips of the road where pedestrians are expected to cross.

The actual appearance of pedestrian crossings varies greatly, but the two most common appearances are: (1) a series of parallel white stripes or (2) two long horizontal white lines. The former is usually preferred, as it stands out more conspicuously against the dark pavement.

Some pedestrian crossings also accompany a traffic signal which will make vehicles stop at regular intervals so the pedestrians can cross. Some countries have "intelligent" pedestrian signals, where the pedestrian must push a button in order to assert his intention to cross. The traffic signal will use that information to schedule itself, that is, when no pedestrians are present the signal will never pointlessly cause vehicle traffic to stop.

Pedestrian crossings without traffic signals are also common. In this case, the traffic laws usually states that the pedestrian has the right of way when crossing, and that vehicles must stop when a pedestrian uses the crossing. Countries and driving cultures vary greatly as to the extent to which this is respected. In the state of Nevada the car has the right of way when the crosswalk signal specifically forbids pedestrian crossing.

Some jurisdictions forbid crossing or using the road anywhere other than at crossings, termed jaywalking
Jaywalking
Jaywalking is an informal term commonly used in North America to refer to illegal or reckless pedestrian crossing of a roadway. Examples include a pedestrian crossing between intersections without yielding to drivers and starting to cross a crosswalk at a signalized intersection without waiting...

. In other areas, pedestrians may have the right to cross where they choose, and have right of way over vehicular traffic while crossing.

In most areas, an intersection is considered to have a crosswalk, even if not painted, as long as the roads meet at approximate right angles. Examples of locations where this rule is not in effect are the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 and Croatia
Croatia
Croatia , officially the Republic of Croatia , is a unitary democratic parliamentary republic in Europe at the crossroads of the Mitteleuropa, the Balkans, and the Mediterranean. Its capital and largest city is Zagreb. The country is divided into 20 counties and the city of Zagreb. Croatia covers ...

.

Pedestrian crossings may also be located away from intersections.

Level crossings

A level crossing is an at-grade intersection of a railway by a road. Because of safety issues, they are often equipped with closable gates
Boom barrier
A boom barrier is a bar, or pole pivoted in such a way as to allow the boom to block vehicular access through a controlled point. Typically the tip of a boom gate rises in a vertical arc to a near vertical position. Boom gates are often counterweighted, so the pole is easily tipped...

, crossing bells and warning signs.

Speed limits

The higher the speed of a vehicle, the more difficult collision avoidance becomes and the greater the damage if a collision does occur. Therefore, many countries of the world limit the maximum speed allowed
Speed limit
Road speed limits are used in most countries to regulate the speed of road vehicles. Speed limits may define maximum , minimum or no speed limit and are normally indicated using a traffic sign...

 on their roads. Vehicles are not supposed to be driven at speeds which are higher than the posted maximum.

To enforce speed limits, two approaches are generally employed. In the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, it is common for the police to patrol the streets and use special equipment (typically a radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...

 unit) to measure the speed of vehicles, and pull over any vehicle found to be in violation of the speed limit. In Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

, Colombia
Colombia
Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...

 and some European countries, there are computerized speed-measuring devices spread throughout the city, which will automatically detect speeding drivers and take a photograph of the license plate (or number plate), which is later used for applying and mailing the ticket. Many jurisdictions in the U.S. use this technology as well.

A mechanism that was developed in Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 is the Grüne Welle, or green wave
Green wave
A green wave is an intentionally induced phenomenon in which a series of traffic lights are coordinated to allow continuous traffic flow over several intersections in one main direction....

, which is an indicator that shows the optimal speed to travel for the synchronized green lights along that corridor. Driving faster or slower than the speed set by the behavior of the lights causes the driver to frequently encounter red lights. This discourages drivers from speeding or impeding the flow of traffic. See related traffic wave
Traffic wave
Traffic waves, also called stop waves or traffic shocks, are travelling disturbances in the distribution of cars on a highway. Traffic waves usually travel backwards in relation to the motion of the cars themselves, or "upstream". The waves can also travel downstream, however, more commonly become...

.

Overtaking

Overtaking
Overtaking
Overtaking or passing is the act of one vehicle going past another slower moving vehicle, travelling in the same direction, on a road. The lane used for overtaking another vehicle is almost always a lane further from the road shoulder — that is, to the left in places that drive on the right,...

(or passing) refers to a maneuver by which one or more vehicles traveling in the same direction are passed by another vehicle. On two-lane roads, when there is a split line or a dashed line on the side of the overtaker, drivers may overtake when it is safe. On multi-lane roads in most jurisdictions, overtaking is permitted in the "slower" lanes, though many require a special circumstance. See "Lanes" below.

In the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 and Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

, notably on extra-urban roads, a solid white or yellow line closer to the driver is used to indicate that no overtaking is allowed in that lane. A double white or yellow line means that neither side may overtake.

In the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, a solid white line means that lane changes are discouraged and a double-white line means that the lane change is prohibited.

Lanes

When a street is wide enough to accommodate several vehicles traveling side-by-side, it is usual for traffic to organize itself into lanes, that is, parallel
Parallel (geometry)
Parallelism is a term in geometry and in everyday life that refers to a property in Euclidean space of two or more lines or planes, or a combination of these. The assumed existence and properties of parallel lines are the basis of Euclid's parallel postulate. Two lines in a plane that do not...

 corridors of traffic. Some roads have one lane for each direction of travel and others have multiple lanes for each direction. Most countries apply pavement markings to clearly indicate the limits of each lane and the direction of travel that it must be used for. In other countries lanes have no markings at all and drivers follow them mostly by intuition
Intuition (knowledge)
Intuition is the ability to acquire knowledge without inference or the use of reason. "The word 'intuition' comes from the Latin word 'intueri', which is often roughly translated as meaning 'to look inside'’ or 'to contemplate'." Intuition provides us with beliefs that we cannot necessarily justify...

 rather than visual stimulus.

On roads that have multiple lanes going in the same direction, drivers may usually shift amongst lanes as they please, but they must do so in a way that does not cause inconvenience to other drivers. Driving cultures vary greatly on the issue of "lane ownership": in some countries, drivers traveling in a lane will be very protective of their right to travel in it while in others drivers will routinely expect other drivers to shift back and forth.

Designation and overtaking

The usual designation for lanes on divided highway
Divided Highway
Divided Highway is a compilation album by American rock band The Doobie Brothers, released in 2003. . All tracks are taken from the albums Cycles and Brotherhood .-Track listing:...

s is the fastest lane is the one closest to the center of the road, and the slowest to the edge of the road. Drivers are usually expected to keep in the slowest lane unless overtaking
Overtaking
Overtaking or passing is the act of one vehicle going past another slower moving vehicle, travelling in the same direction, on a road. The lane used for overtaking another vehicle is almost always a lane further from the road shoulder — that is, to the left in places that drive on the right,...

, though with more traffic congestion all lanes are often used.

When driving on the left:
  • The lane designated for faster traffic is on the right.
  • The lane designated for slower traffic is on the left.
  • Most freeway exits are on the left.
  • Overtaking is permitted to the right, and sometimes to the left.


When driving on the right:
  • The lane designated for faster traffic is on the left.
  • The lane designated for slower traffic is on the right.
  • Most freeway exits are on the right.
  • Overtaking is permitted to the left, and sometimes to the right.


Countries party to the Vienna Convention on Road Traffic
Vienna Convention on Road Traffic
The Vienna Convention on Road Traffic is an international treaty designed to facilitate international road traffic and to increase road safety by standardising the uniform traffic rules among the contracting parties...

 have uniform rules about overtaking and lane designation. The convention details (amongst other things) that "Every driver shall keep to the edge of the carriageway appropriate to the direction of traffic", and the "Drivers overtaking shall do so on the side opposite to that appropriate to the direction of traffic", notwithstanding the presence or absence of oncoming traffic. Allowed exceptions to these rules include turning or heavy traffic, traffic in lines, or situation in which signs or markings must dictate otherwise. These rules must be more strictly adhered to on roads with oncoming traffic, but still apply on multi-lane and divided highways. Many countries in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

 are party to the Vienna Conventions on traffic and roads. In Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

 (which is not a contracting party), traveling in any lane other than the "slow" lane on a road with a speed limit at or above 80 km/h (49.7 mph) is an offence, unless signage is posted to the contrary or the driver is overtaking.

Many areas in North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

 do not have any laws about staying to the slowest lanes unless overtaking. In those areas, unlike many parts of Europe, traffic is allowed to overtake on any side, even in a slower lane. This practice is known as "passing on the right" in the United States (where it is common) and "overtaking on the inside" and "undertaking" in the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

.
When referring to individual lanes on dual carriageways, one does not consider traffic travelling the opposite direction. The inside lane (i.e. the one beside the hard shoulder) refers to the lane used for normal travel, while the middle lane is used for overtaking cars on the inside lane. The outside lane (i.e. closest to oncoming traffic) is used for overtaking vehicles in the middle lane. The same principle lies with dual carriageways with more than three lanes.

U.S.-state-specific practices

In some U.S. state
U.S. state
A U.S. state is any one of the 50 federated states of the United States of America that share sovereignty with the federal government. Because of this shared sovereignty, an American is a citizen both of the federal entity and of his or her state of domicile. Four states use the official title of...

s (such as Louisiana
Louisiana
Louisiana is a state located in the southern region of the United States of America. Its capital is Baton Rouge and largest city is New Orleans. Louisiana is the only state in the U.S. with political subdivisions termed parishes, which are local governments equivalent to counties...

, Massachusetts
Massachusetts
The Commonwealth of Massachusetts is a state in the New England region of the northeastern United States of America. It is bordered by Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north; at its east lies the Atlantic Ocean. As of the 2010...

 and New York
New York
New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...

), although there are laws requiring all traffic on a public way to use the right-most lane unless overtaking, this rule is often ignored and seldom enforced on multi-lane roadways. Some states, such as Colorado
Colorado
Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...

, use a combination of laws and signs restricting speeds or vehicles on certain lanes to emphasize overtaking only on the left lane, and to avoid a psychological condition commonly called road rage
Road rage
Road rage is an aggressive or angry behavior by a driver of an automobile or other motor vehicle. Such behavior might include rude gestures, verbal insults, deliberately driving in an unsafe or threatening manner, or making threats. Road rage can lead to altercations, assaults, and collisions...

.

In California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

, cars may use any lane on multi-lane roadways. Drivers moving slower than the general flow of traffic are required to stay in the right-most lanes (by California Vehicle Code (CVC) 21654) to keep the way clear for faster vehicles and thus speed up traffic. However, faster drivers may legally pass in the slower lanes if conditions allow (by CVC 21754). But the CVC also requires trucks to stay in the right lane, or in the right two lanes if the roadway has four or more lanes going in their direction. The oldest freeways in California, and some freeway interchanges, often have ramps on the left, making signs like "TRUCKS OK ON LEFT LANE" or "TRUCKS MAY USE ALL LANES" necessary to override the default rule. Lane splitting
Lane splitting
Lane splitting refers to a two-wheeled vehicle moving between lanes of vehicles that are proceeding in the same direction. More narrowly, it refers to passing stopped or slower moving traffic between lanes at a speed greater than surrounding traffic....

, or riding motorcycles in the space between cars in traffic, is permitted as long as it is done in a safe and prudent manner.

One-way roadways

Main articles: One-way traffic
One-way traffic
One-way traffic is traffic that moves in a single direction. A one-way street is a street either facilitating only one-way traffic, or designed to direct vehicles to move in one direction.-General signs:...

 and Dual carriageway
Dual carriageway
A dual carriageway is a class of highway with two carriageways for traffic travelling in opposite directions separated by a central reservation...



In order to increase traffic capacity and safety, a route may have two or more separate roads for each direction of traffic. Alternatively, a given road might be declared one-way.

High-speed roads

Main articles: Limited-access road
Limited-access road
A limited-access road known by various terms worldwide, including limited-access highway, dual-carriageway and expressway, is a highway or arterial road for high-speed traffic which has many or most characteristics of a controlled-access highway , including limited or no access to adjacent...

 and Controlled-access highway
Controlled-access highway
A controlled-access highway is a highway designed exclusively for high-speed vehicular traffic, with all traffic flow and ingress/egress regulated...



In large cities, moving from one part of the city to another by means of ordinary streets and avenues can be time-consuming since traffic is often slowed by at-grade junctions, tight turns, narrow marked lanes and lack of a minimum speed limit
Speed limit
Road speed limits are used in most countries to regulate the speed of road vehicles. Speed limits may define maximum , minimum or no speed limit and are normally indicated using a traffic sign...

. Therefore, it has become common practice for larger cities to build roads for faster through traffic. There are two different types of roads used to provide high-speed access across urban areas:
  • The controlled-access highway
    Controlled-access highway
    A controlled-access highway is a highway designed exclusively for high-speed vehicular traffic, with all traffic flow and ingress/egress regulated...

     (freeway or motorway), is a divided multi-lane highway with fully controlled access and grade-separated intersections (no cross traffic). Some freeways are called expressways
    Controlled-access highway
    A controlled-access highway is a highway designed exclusively for high-speed vehicular traffic, with all traffic flow and ingress/egress regulated...

    , super-highways, or turnpikes, depending on local usage. Access to freeways is fully controlled; entering and leaving the freeway is permitted only at grade-separated interchanges.
  • The limited-access road
    Limited-access road
    A limited-access road known by various terms worldwide, including limited-access highway, dual-carriageway and expressway, is a highway or arterial road for high-speed traffic which has many or most characteristics of a controlled-access highway , including limited or no access to adjacent...

     (often called expressway in areas where the name does not refer to a freeway or motorway) is a lower-grade type of road with some or many of the characteristics of a controlled-access highway: usually a broad multi-lane avenue, frequently divided, with some grade separation
    Grade separation
    Grade separation is the method of aligning a junction of two or more transport axes at different heights so that they will not disrupt the traffic flow on other transit routes when they cross each other. The composition of such transport axes does not have to be uniform; it can consist of a...

     at intersections.


Motor vehicle
Motor vehicle
A motor vehicle or road vehicle is a self-propelled wheeled vehicle that does not operate on rails, such as trains or trolleys. The vehicle propulsion is provided by an engine or motor, usually by an internal combustion engine, or an electric motor, or some combination of the two, such as hybrid...

 drivers
Driving
Driving is the controlled operation and movement of a land vehicle, such as a car, truck or bus.Although direct operation of a bicycle and a mounted animal are commonly referred to as riding, such operators are legally considered drivers and are required to obey the rules of the road...

 wishing to travel over great distances within the city will usually take the freeways or expressways in order to minimize travel time. When a crossing road is at the same grade
Grade separation
Grade separation is the method of aligning a junction of two or more transport axes at different heights so that they will not disrupt the traffic flow on other transit routes when they cross each other. The composition of such transport axes does not have to be uniform; it can consist of a...

 as the freeway, a bridge
Bridge
A bridge is a structure built to span physical obstacles such as a body of water, valley, or road, for the purpose of providing passage over the obstacle...

 (or, less often, an underpass) will be built for the crossing road. If the freeway is elevated, the crossing road will pass underneath it.

Minimum speed signs are sometimes posted (although increasingly rare) and usually indicate that any vehicle traveling slower than 40 mph (17.9 m/s) should indicate a slower speed of travel to other motor vehicles by engaging the vehicle's four-way flashing lights. Alternative slower-than-posted speeds may be in effect, based on the posted speed limit of the highway/freeway.

Systems of freeways and expressways are also built to connect distant and regional cities, notable systems include the Interstate highways, the Autobahnen and the Expressway Network of the People's Republic of China
Expressways of China
The Expressway Network of the People's Republic of China is one of the longest in the world. The network is also known as National Trunk Highway System . The total length of China's expressways was at the end of 2010, the world's second longest only after the United States and slightly longer...

.

One-way streets

In more sophisticated systems such as large cities, this concept is further extended: some streets are marked as being one-way, and on those streets all traffic must flow in only one direction, but pedestrians on the sidewalks are generally not limited to one-way movement. A driver wishing to reach a destination he already passed must use other streets in order to return. Usage of one-way streets, despite the inconveniences it can bring to individual drivers, can greatly improve traffic flow since they usually allow traffic to move faster and tend to simplify intersections.

Congested traffic

In some places traffic volume is consistently, extremely large, either during periods of time referred to as rush hour or perpetually. Exceptionally, traffic upstream of an accident or an obstruction, such as construction, may also be constrained, resulting in a traffic jam. Such dynamics in relation to traffic congestion
Traffic congestion
Traffic congestion is a condition on road networks that occurs as use increases, and is characterized by slower speeds, longer trip times, and increased vehicular queueing. The most common example is the physical use of roads by vehicles. When traffic demand is great enough that the interaction...

 is known as traffic flow
Traffic flow
Traffic flow, in mathematics and civil engineering, is the study of interactions between vehicles, drivers, and infrastructure , with the aim of understanding and developing an optimal road network with efficient movement of traffic and minimal traffic congestion problems.-History:Attempts to...

. Traffic engineers
Traffic engineering (transportation)
For the engineering of communications and computer networks, see Teletraffic engineering.Traffic engineering is a branch of civil engineering that uses engineering techniques to achieve the safe and efficient movement of people and goods on roadways...

 sometimes gauge the quality of traffic flow in terms of level of service
Level of service
Level of service is a measure used by traffic engineers to determine the effectiveness of elements of transportation infrastructure. LOS is most commonly used to analyze highways by categorizing traffic flow with corresponding safe driving conditions...

.

In measured traffic data, common spatiotemporal empirical features of traffic congestion
Traffic congestion: Reconstruction with Kerner’s three-phase theory
Vehicular traffic can be either free or congested. Traffic occurs in time and space, i.e., it is a spatiotemporal process. However, usually traffic can be measured only at some road locations...

 have been found that are qualitatively the same for different highways in different countries. Some of these common features distinguish the wide moving jam and synchronized flow phases of congested traffic in Kerner’s
Boris Kerner
Boris S. Kerner is the pioneer of the much-discussed three-phase traffic theory.- Life and work :Boris S. Kerner is a leading expert in intelligent transportation systems and in the theory of pattern formation in dissipative physical, chemical, biological systems. He was born in Moscow, Soviet...

 three-phase traffic theory.

Rush hour

During business days in most major cities, traffic congestion
Traffic congestion
Traffic congestion is a condition on road networks that occurs as use increases, and is characterized by slower speeds, longer trip times, and increased vehicular queueing. The most common example is the physical use of roads by vehicles. When traffic demand is great enough that the interaction...

 reaches great intensity at predictable times of the day due to the large number of vehicles using the road at the same time. This phenomenon is called rush hour
Rush hour
A rush hour or peak hour is a part of the day during which traffic congestion on roads and crowding on public transport is at its highest. Normally, this happens twice a day—once in the morning and once in the evening, the times during when the most people commute...

or peak hour, although the period of high traffic intensity often exceeds one hour.

Rush hour policies

Some cities adopt policies to reduce rush-hour traffic and pollution and encourage the use of public transportation. For example, in São Paulo
São Paulo
São Paulo is the largest city in Brazil, the largest city in the southern hemisphere and South America, and the world's seventh largest city by population. The metropolis is anchor to the São Paulo metropolitan area, ranked as the second-most populous metropolitan area in the Americas and among...

, Manila
Manila
Manila is the capital of the Philippines. It is one of the sixteen cities forming Metro Manila.Manila is located on the eastern shores of Manila Bay and is bordered by Navotas and Caloocan to the north, Quezon City to the northeast, San Juan and Mandaluyong to the east, Makati on the southeast,...

and in Mexico City
Mexico City
Mexico City is the Federal District , capital of Mexico and seat of the federal powers of the Mexican Union. It is a federal entity within Mexico which is not part of any one of the 31 Mexican states but belongs to the federation as a whole...

, each vehicle has a specific day of the week in which it is forbidden from traveling the roads during rush hour. The day for each vehicle is taken from the license plate number, and this rule is enforced by traffic police and also by hundreds of strategically positioned traffic cameras backed by computerized image-recognition systems that issue tickets to offending drivers.

In the United States and Canada, several expressways have a special lane (called an "HOV Lane" - High Occupancy Vehicle Lane) that can only be used by cars carrying two (some locations-three) or more people. Also, many major cities have instituted strict parking prohibitions during rush hour on major arterial streets leading to and from the central business district. During designated weekday hours, vehicles parked on these primary routes are subject to prompt ticketing and towing at owner expense. The purpose of these restrictions is to make available an additional traffic lane in order to maximize available traffic capacity. Additionally, several cities offer a public telephone service where citizens can arrange rides with others depending on where they live and work. The purpose of these policies is to reduce the number of vehicles on the roads and thus reduce rush-hour traffic intensity.

Metered freeways are also a solution for controlling rush hour traffic. In Phoenix, Arizona and Seattle, Washington, among other places, metered on-ramps have been implemented. During rush hour, traffic signals are used with green lights to allow one car per blink of the light to proceed on to the freeway.

Pre-emption

In some areas, emergency responders
Emergency service
Emergency services are organizations which ensure public safety and health by addressing different emergencies. Some agencies exist solely for addressing certain types of emergencies whilst others deal with ad hoc emergencies as part of their normal responsibilities...

 are provided with specialized equipment, such as an Mobile Infrared Transmitter
Mobile Infrared Transmitter
A Mobile Infrared Transmitter is an electronic traffic preemption device that city buses and emergency vehicles use to control the traffic control equipment for intersections they are approaching, in order to pass through the intersection as efficiently or safely as possible.-Description:A MIRT...

, which allows emergency response vehicles, particularly fire fighting apparatus
Fire apparatus
A fire apparatus, fire engine, fire truck, or fire appliance is a vehicle designed to assist in fighting fires by transporting firefighters to the scene and providing them with access to the fire, along with water or other equipment...

, to have high-priority travel by having the lights along their route change to green. The technology behind these methods have evolved, from panels at the fire department (which could trigger and control green lights for certain major corridors) to optical systems (which the individual fire apparatus can be equipped with to communicate directly with receivers on the signal head). In other areas, public transport bus
Bus
A bus is a road vehicle designed to carry passengers. Buses can have a capacity as high as 300 passengers. The most common type of bus is the single-decker bus, with larger loads carried by double-decker buses and articulated buses, and smaller loads carried by midibuses and minibuses; coaches are...

es have special equipment to get green lights.

During emergencies where evacuation of a heavily populated area is required, local authorities may institute contraflow lane reversal
Contraflow lane reversal
Contraflow lane reversal refers to plans that alter the normal flow of traffic, typically on a controlled-access highway , to either aid in an emergency evacuation or, as part of routine maintenance activities, to facilitate widening or reconstruction of one of the highway's carriageways...

, in which all lanes of a road lead away from a danger zone regardless of their original flow. Aside from emergencies, contraflow may also be used to ease traffic congestion during rush hour or at the end of a sports event (where a large number of cars are leaving the venue at the same time). For example, the six lanes of the Lincoln Tunnel
Lincoln Tunnel
The Lincoln Tunnel is a long tunnel under the Hudson River, connecting Weehawken, New Jersey and the borough of Manhattan in New York City.-History:...

 can be changed from three in-bound and three out-bound to a two/four configuration depending on traffic volume. The Brazilian highways Rodovia dos Imigrantes
Rodovia dos Imigrantes
Rodovia dos Imigrantes is a highway in the state of São Paulo, Brazil.The highway connects the city of São Paulo to the Atlantic coast and with the seaside cities of São Vicente and Praia Grande. It follows the route of Rodovia Anchieta and is also one of Brazil's busiest highways, particularly on...

 and Rodovia Anchieta
Rodovia Anchieta
Rodovia Anchieta is a highway connection between São Paulo and the Atlantic coast, the cities of Cubatão and Santos, in Brazil...

 connect São Paulo
São Paulo
São Paulo is the largest city in Brazil, the largest city in the southern hemisphere and South America, and the world's seventh largest city by population. The metropolis is anchor to the São Paulo metropolitan area, ranked as the second-most populous metropolitan area in the Americas and among...

 to the Atlantic coast. Almost all lanes of both highways are usually reversed during weekends to allow for heavy seaside traffic. The reversibility of the highways requires many additional highway ramps and complicated interchanges
Interchange (road)
In the field of road transport, an interchange is a road junction that typically uses grade separation, and one or more ramps, to permit traffic on at least one highway to pass through the junction without directly crossing any other traffic stream. It differs from a standard intersection, at which...

.

Intelligent transportation systems

An intelligent transportation system
Intelligent transportation system
The term intelligent transportation systems refers to information and communication technology that improve transport outcomes such as transport safety, transport productivity, travel reliability, informed travel choices, social equity, environmental performance and network operation...

 (ITS) is a system of hardware, software, and operators that allow better monitoring and control of traffic in order to optimize traffic flow. As the number of vehicle lane miles traveled per year continues to increase dramatically, and as the number of vehicle lane miles constructed per year has not been keeping pace, this has led to ever-increasing traffic congestion
Traffic congestion
Traffic congestion is a condition on road networks that occurs as use increases, and is characterized by slower speeds, longer trip times, and increased vehicular queueing. The most common example is the physical use of roads by vehicles. When traffic demand is great enough that the interaction...

. As a cost-effective solution toward optimizing traffic, ITS presents a number of technologies to reduce congestion by monitoring traffic flows through the use of sensors and live cameras or analysing cellular phone data travelling in cars (floating car data
Floating Car Data
Floating car data , also known as floating cellular data, is a method to determine the traffic speed on the road network. It is based on the collection of localisation data, speed, direction of travel and time information from mobile phones in vehicles that are being driven...

) and in turn rerouting traffic as needed through the use of variable message boards (VMS), highway advisory radio, on board or off board navigation devices and other systems through integration of traffic data with navigation systems
Integration of traffic data with navigation systems
Integration of traffic data with navigation systems occurs in many different ways.According to Consumer Reports, the data may be transmitted through Bluetooth, FM, or XM....

. Additionally, the roadway network has been increasingly fitted with additional communications and control infrastructure to allow traffic operations personnel to monitor weather conditions, for dispatching maintenance crews to perform snow or ice removal, as well as intelligent systems such as automated bridge de-icing systems which help to prevent accidents.

See also

  • Air traffic control
    Air traffic control
    Air traffic control is a service provided by ground-based controllers who direct aircraft on the ground and in the air. The primary purpose of ATC systems worldwide is to separate aircraft to prevent collisions, to organize and expedite the flow of traffic, and to provide information and other...

  • Bicycle safety
    Bicycle safety
    Bicycle safety is the use of practices designed to reduce risk associated with cycling. Some of this subject matter is hotly debated: for example, the discussions as to whether bicycle helmets or cyclepaths really deliver improved safety...

  • Cross-sea traffic ways
    Cross-sea traffic ways
    Cross-sea traffic ways are vehicle or railroad traffic ways across the sea. Such traffic ways could include bridges or tunnels.-Existing sea bridges: Donghai Bridge Hangzhou Bay Bridge - Oresund Bridge - King Fahd Causeway Bandra-Worli Sea Link Chesapeake Bay Bridge-Tunnel Cross-sea traffic...

  • Induced demand
    Induced demand
    Induced demand, or latent demand, is the phenomenon that after supply increases, more of a good is consumed. This is entirely consistent with the economic theory of supply and demand; however, this idea has become important in the debate over the expansion of transportation systems, and is often...

  • Institute of Transportation Engineers
    Institute of Transportation Engineers
    The Institute of Transportation Engineers or ITE is an international educational and scientific association of transportation professionals who are responsible for meeting mobility and safety needs. ITE was founded in 1930 as the Institute of Traffic Engineers and its first president was Ernest P...

  • International Regulations for Preventing Collisions at Sea
    International Regulations for Preventing Collisions at Sea
    The International Regulations for Preventing Collisions at Sea 1972 are published by the International Maritime Organization , and set out, inter alia, the "rules of the road" or navigation rules to be followed by ships and other vessels at sea in order to prevent collisions between two or more...

  • Journal of Transport and Land Use
    Journal of Transport and Land Use
    The Journal of Transport and Land Use is an open access peer-reviewed academic journal covering the interaction of transport and land use that was established in 2008. As of August 2011, it is the official journal of the World Society on Transport and Land Use Research...

  • Line source
    Line source
    A line source is a source of air, noise, water contamination or electromagnetic radiation that emanates from a linear geometry...

  • Road traffic control device
    Road traffic control device
    Traffic Control Devices are markers, signs and signal devices used to inform, guide and control the traffic and the pedestrians. These devices are usually placed adjacent, over and/or along the highways, roads, traffic facilities and other public areas that require traffic control.The most popular...

  • Road traffic safety
  • Road safety
  • Road transport
    Road transport
    Road transport or road transportation is transport on roads of passengers or goods. A hybrid of road transport and ship transport is the historic horse-drawn boat.-History:...

  • Australian Road Rules
    Australian Road Rules
    The Australian Road Rules are a set of model road rules developed by the National Road Transport Commission which form the platform for State and Territory road rules across Australia...

  • Rules of the road in the People's Republic of China
    Rules of the road in the People's Republic of China
    Traffic law in mainland China is still in its nascent stage . Therefore, the rules of the road in the People's Republic of China are understood to mean both the codified and uncodified practices, procedures and norms of behavior generally followed by motorists, cyclists and pedestrians in the...

  • Rules of the road in New Zealand
  • Traffic law
  • Three-phase traffic theory
  • Traffic psychology
    Traffic psychology
    Traffic psychology is a young, expanding and wide field in psychology. Whereas traffic psychology is primarily related to the study of the behavior of road users and the psychological processes underlying that behavior as well as to the relationship between behavior and accidents, transportation...

  • Traffic congestion: Reconstruction with Kerner’s three-phase theory
    Traffic congestion: Reconstruction with Kerner’s three-phase theory
    Vehicular traffic can be either free or congested. Traffic occurs in time and space, i.e., it is a spatiotemporal process. However, usually traffic can be measured only at some road locations...

  • Transport
    Transport
    Transport or transportation is the movement of people, cattle, animals and goods from one location to another. Modes of transport include air, rail, road, water, cable, pipeline, and space. The field can be divided into infrastructure, vehicles, and operations...

  • Transportation forecasting
    Transportation forecasting
    Transportation forecasting is the process of estimating the number of vehicles or people that will use a specific transportation facility in the future. For instance, a forecast may estimate the number of vehicles on a planned road or bridge, the ridership on a railway line, the number of...

  • Web traffic
    Web traffic
    Web traffic is the amount of data sent and received by visitors to a web site. It is a large portion of Internet traffic. This is determined by the number of visitors and the number of pages they visit...


External links


Further reading

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