Traffic congestion

# Traffic congestion

Overview
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
Queueing theory
Queueing theory is the mathematical study of waiting lines, or queues. The theory enables mathematical analysis of several related processes, including arriving at the queue, waiting in the queue , and being served at the front of the queue...

. The most common example is the physical use of roads by vehicles. When traffic demand is great enough that the interaction between vehicles slows the speed of the traffic stream, this results in some congestion. As demand approaches the capacity of a road (or of the intersections along the road), extreme traffic congestion sets in.
Discussion

Recent Discussions
Encyclopedia
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
Queueing theory
Queueing theory is the mathematical study of waiting lines, or queues. The theory enables mathematical analysis of several related processes, including arriving at the queue, waiting in the queue , and being served at the front of the queue...

. The most common example is the physical use of roads by vehicles. When traffic demand is great enough that the interaction between vehicles slows the speed of the traffic stream, this results in some congestion. As demand approaches the capacity of a road (or of the intersections along the road), extreme traffic congestion sets in. When vehicles are fully stopped for periods of time, this is colloquially known as a traffic jam or traffic snarl-up.

## Causes

Traffic congestion occurs when a volume of traffic or modal split
Mode choice
Mode choice analysis is the third step in the conventional four-step transportation forecasting model, following trip generation and trip distribution but before route assignment. Trip distribution's zonal interchange analysis yields a set of origin destination tables which tells where the trips...

generates demand for space greater than the available road capacity; this point is commonly termed saturation
Degree of saturation (traffic)
In traffic engineering, the degree of saturation of an intersection or road is a measure of how much demand it is experiencing compared to its total capacity....

. There are a number of specific circumstances which cause or aggravate congestion; most of them reduce the capacity of a road at a given point or over a certain length, or increase the number of vehicles required for a given volume of people or goods. About half of U.S. traffic congestion is recurring, and is attributed to sheer weight of traffic; most of the rest is attributed to traffic incidents, road work and weather events.

Traffic research still cannot fully predict under which conditions a "traffic jam" (as opposed to heavy, but smoothly flowing traffic) may suddenly occur. It has been found that individual incidents (such as accidents or even a single car braking heavily in a previously smooth flow) may cause ripple effects (a cascading failure
A cascading failure is a failure in a system of interconnected parts in which the failure of a part can trigger the failure of successive parts.- Cascading failure in power transmission :...

) which then spread out and create a sustained traffic jam when, otherwise, normal flow might have continued for some time longer.

### Mathematical theories

Some traffic engineers have attempted to apply the rules of fluid dynamics
Fluid dynamics
In physics, fluid dynamics is a sub-discipline of fluid mechanics that deals with fluid flow—the natural science of fluids in motion. It has several subdisciplines itself, including aerodynamics and hydrodynamics...

to traffic flow, likening it to the flow of a fluid in a pipe. Congestion simulations and real-time observations have shown that in heavy but free flowing traffic, jams can arise spontaneously, triggered by minor events ("butterfly effect
Butterfly effect
In chaos theory, the butterfly effect is the sensitive dependence on initial conditions; where a small change at one place in a nonlinear system can result in large differences to a later state...

s"), such as an abrupt steering maneuver by a single motorist. Traffic scientists liken such a situation to the sudden freezing of supercooled fluid
Supercooling
Supercooling, also known as undercooling, is the process of lowering the temperature of a liquid or a gas below its freezing point without it becoming a solid....

.
However, unlike a fluid, traffic flow is often affected by signals or other events at junctions that periodically affect the smooth flow of traffic. Alternative mathematical theories exist, such as Boris Kerner
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...

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...

).

Because of the poor correlation of theoretical models to actual observed traffic flows, transportation planners and highway engineers attempt to forecast 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...

using empirical models. Their working traffic models typically use a combination of macro-, micro- and mesoscopic features, and may add matrix entropy
Entropy
Entropy is a thermodynamic property that can be used to determine the energy available for useful work in a thermodynamic process, such as in energy conversion devices, engines, or machines. Such devices can only be driven by convertible energy, and have a theoretical maximum efficiency when...

effects, by "platooning" groups of vehicles and by randomising the flow patterns within individual segments of the network. These models are then typically calibrated by measuring actual traffic flows on the links in the network, and the baseline flows are adjusted accordingly.

It is now claimed that equations can predict these in detail:
Phantom jams can form when there is a heavy volume of cars on the road. In that high density of traffic, small disturbances (a driver hitting the brake too hard, or getting too close to another car) can quickly become amplified into a full-blown, self-sustaining traffic jam...

A team of MIT mathematicians has developed a model that describes how and under what conditions such jams form, which could help road designers minimize the odds of their formation. The researchers reported their findings May 26 in the online edition of Physical Review E.

Key to the new study is the realization that the mathematics of such jams, which the researchers call 'jamitons,' are strikingly similar to the equations that describe detonation waves produced by explosions, says Aslan Kasimov, lecturer in MIT's Department of Mathematics. That discovery enabled the team to solve traffic jam equations that were first theorized in the 1950s.

### Economic theories

Congested roads can be seen as an example of the tragedy of the commons
Tragedy of the commons
The tragedy of the commons is a dilemma arising from the situation in which multiple individuals, acting independently and rationally consulting their own self-interest, will ultimately deplete a shared limited resource, even when it is clear that it is not in anyone's long-term interest for this...

. Because roads in most places are free at the point of usage, there is little financial incentive for drivers not to over-use them, up to the point where traffic collapses into a jam, when demand becomes limited by opportunity cost
Opportunity cost
Opportunity cost is the cost of any activity measured in terms of the value of the best alternative that is not chosen . It is the sacrifice related to the second best choice available to someone, or group, who has picked among several mutually exclusive choices. The opportunity cost is also the...

. Privatization of highways
Private highway
A private highway is a highway owned and operated for profit by private industry. Private highways are common in Asia and Europe; in addition, a few have been built in the United States on an experimental basis...

Road pricing is an economic concept regarding the various direct charges applied for the use of roads. The road charges includes fuel taxes, licence fees, parking taxes, tolls, and congestion charges, including those which may vary by time of day, by the specific road, or by the specific vehicle...

have both been proposed as measures that may reduce congestion through economic incentives and disincentives. Congestion can also happen due to non-recurring highway incidents, such as a crash
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,...

Construction
In the fields of architecture and civil engineering, construction is a process that consists of the building or assembling of infrastructure. Far from being a single activity, large scale construction is a feat of human multitasking...

, which may reduce the road's capacity below normal levels.

Economist Anthony Downs
Anthony Downs
Anthony Downs is a scholar in public policy and public administration, and since 1977 is a Senior Fellow at the Brookings Institution in Washington D.C..-Education:...

argues that 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...

traffic congestion is inevitable because of the benefits of having a relatively standard work day
Business hours are the hours during the day in which business is commonly conducted. Typical business hours vary widely by country. By observing common informal standards for business hours, workers may communicate with each other more easily and find a convenient divide between work life and...

. In a capitalist
Capitalism
Capitalism is an economic system that became dominant in the Western world following the demise of feudalism. There is no consensus on the precise definition nor on how the term should be used as a historical category...

economy, goods can be allocated either by pricing (ability to pay) or by queueing (first-come first-serve); congestion is an example of the latter. Instead of the traditional solution of making the "pipe" large enough to accommodate the total demand for peak-hour vehicle travel (a supply-side solution), either by widening roadways or increasing "flow pressure" via automated highway systems, Downs advocates greater use of road pricing
Road pricing is an economic concept regarding the various direct charges applied for the use of roads. The road charges includes fuel taxes, licence fees, parking taxes, tolls, and congestion charges, including those which may vary by time of day, by the specific road, or by the specific vehicle...

to reduce congestion (a demand-side solution, effectively rationing demand), in turn plowing the revenues generated therefrom into public transportation projects.

## Classification

Qualitative classification of traffic is often done in the form of a six letter A-F 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...

(LOS) scale defined in the Highway Capacity Manual
Highway Capacity Manual
The Highway Capacity Manual is a publication of the Transportation Research Board in the United States. It contains concepts, guidelines, and computational procedures for computing the capacity and quality of service of various highway facilities, including freeways, highways, arterial roads,...

, a US document used (or used as a basis for national guidelines) worldwide. These levels are used by transportation engineer
Transport engineering
Transportation engineering is the application of technology and scientific principles to the planning, functional design, operation and management of facilities for any mode of transportation in order to provide for the safe, rapid, comfortable, convenient, economical, and environmentally...

s as a shorthand
Shorthand
Shorthand is an abbreviated symbolic writing method that increases speed or brevity of writing as compared to a normal method of writing a language. The process of writing in shorthand is called stenography, from the Greek stenos and graphē or graphie...

and to describe traffic levels to the lay public. While this system generally uses delay as the basis for its measurements, the particular measurements and statistical methods vary depending on the facility being described. For instance, while the percent time spent following a slower-moving vehicle figures into the LOS for a rural two-lane road, the LOS at an urban intersection incorporates such measurements as the number of drivers forced to wait through more than one signal cycle.

Traffic congestion occurs in time and space, i.e., it is a spatiotemporal process. Therefore, another classification schema of traffic congestion is associated with some common spatiotemporal 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...

found in measured traffic data. Common spatiotemporal empirical features of traffic congestion are those features, which are qualitatively the same for different highways
Highway
A highway is any public road. In American English, the term is common and almost always designates major roads. In British English, the term designates any road open to the public. Any interconnected set of highways can be variously referred to as a "highway system", a "highway network", or a...

in different countries measured during years of traffic observations. Common features of traffic congestion are independent on weather
Weather
Weather is the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur in the troposphere, just below the stratosphere. Weather refers, generally, to day-to-day temperature and precipitation activity, whereas climate...

, road conditions and road infrastructure, vehicular technology, driver characteristics, day time, etc. Examples of common features of traffic congestion are the features [J] and [S] for, respectively, the wide moving jam and synchronized flow traffic phases found in Kerner’ three-phase traffic theory. The common features of traffic congestion can be reconstructed in space and time with the use of the ASDA and FOTO
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...

models.

## Negative impacts

Traffic congestion has a number of negative effects:
• Wasting time of motorists and passengers ("opportunity cost
Opportunity cost
Opportunity cost is the cost of any activity measured in terms of the value of the best alternative that is not chosen . It is the sacrifice related to the second best choice available to someone, or group, who has picked among several mutually exclusive choices. The opportunity cost is also the...

"). As a non-productive activity for most people, congestion reduces regional economic health.
• Delays, which may result in late arrival for employment, meetings, and education, resulting in lost business, disciplinary action or other personal losses.
• Inability to forecast travel time accurately, leading to drivers allocating more time to travel "just in case", and less time on productive activities.
• Wasted fuel increasing air pollution
Air pollution
Air pollution is the introduction of chemicals, particulate matter, or biological materials that cause harm or discomfort to humans or other living organisms, or cause damage to the natural environment or built environment, into the atmosphere....

and carbon dioxide emissions
Greenhouse gas
A greenhouse gas is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone...

owing to increased idling, acceleration and braking.
• Wear and tear on vehicles as a result of idling in traffic and frequent acceleration and braking, leading to more frequent repairs and replacements.
• Stressed and frustrated motorists, encouraging 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...

and reduced health of motorists
• Emergencies: blocked traffic may interfere with the passage of emergency vehicles traveling to their destinations where they are urgently needed.
• Spillover effect
Spillover effect
Spillover effects are externalities of economic activity or processes that affect those who are not directly involved. Odours from a rendering plant are negative spillover effects upon its neighbours; the beauty of a homeowner's flower garden is a positive spillover effect upon neighbours.In the...

from congested main arteries to secondary roads and side streets as alternative routes are attempted ('rat running'), which may affect neighborhood amenity
Amenity
In real property and lodging, amenities are any tangible or untangible benefits of a property, especially those that increase its attractiveness or value or that contribute to its comfort or convenience...

and real estate
Real estate
In general use, esp. North American, 'real estate' is taken to mean "Property consisting of land and the buildings on it, along with its natural resources such as crops, minerals, or water; immovable property of this nature; an interest vested in this; an item of real property; buildings or...

prices.

## Countermeasures

It has been suggested by some commentators that the level of congestion that society tolerates is a rational (though not necessarily conscious) choice between the costs of improving the transportation system (in infrastructure or management) and the benefits of quicker travel. Others link it largely to subjective lifestyle choices, differentiating between car-owning and car-free households.

• Junction
A road junction is a location where vehicular traffic going in different directions can proceed in a controlled manner designed to minimize accidents. In some cases, vehicles can change between different routes or directions of travel.-Origins:...

improvements
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...

, using bridges (or, less often, tunnels) freeing movements from having to stop for other crossing movements
• Ramp signalling
Ramp meter
A ramp meter, ramp signal or metering light is a device, usually a basic traffic light or a two-section signal light together with a signal controller, that regulates the flow of traffic entering freeways according to current traffic conditions...

, 'drip-feeding' merging traffic via traffic signals onto a congested motorway-type roadway
• Reducing junctions
• Local-express lanes
Local-express lanes
A Local-express lane system is an arrangement of roadways within a major highway providing one of more roadways for express lanes with a limited number of entrances and exits and also separate roadways for local or collector lanes which provide access to all interchanges...

, providing through lanes that bypass junction on-ramp and off-ramp zones
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...

, roads that limit the type and amounts of driveway
Driveway
A driveway is a type of private road for local access to one or a small group of structures, and is owned and maintained by an individual or group....

s along their lengths
• Reversible lane
Reversible lane
A reversible lane , called a counterflow lane or contraflow lane in transport engineering nomenclature, is a lane in which traffic may travel in either direction, depending on certain conditions...

s, where certain sections of highway operate in the opposite direction on different times of the day/ days of the week, to match asymmetric demand. This may be controlled by Variable-message signs or by movable physical separation
• Separate lanes for specific user groups (usually with the goal of higher people throughput with fewer vehicles)
• Bus lanes as part of a busway system
Bus rapid transit
Bus rapid transit is a term applied to a variety of public transportation systems using buses to provide faster, more efficient service than an ordinary bus line. Often this is achieved by making improvements to existing infrastructure, vehicles and scheduling...

• HOV lane
High-occupancy vehicle lane
In transportation engineering and transportation planning, a high-occupancy vehicle lane is a lane reserved for vehicles with a driver and one or more passengers...

s, for vehicles with at least three (sometimes at least two) riders, intended to encourage carpool
Carpool
Carpooling , is the sharing of car journeys so that more than one person travels in a car....

ing
• Slugging
Slugging
Slugging, also known as casual carpooling, is the practice of forming ad hoc, informal carpools for purposes of commuting, essentially a variation of ride-share commuting and hitchhiking. While the practice is most common and most publicized in the congested Washington, D.C. area, slugging also...

, impromptu carpooling at HOV access points, on a hitchhiking
Hitchhiking
Hitchhiking is a means of transportation that is gained by asking people, usually strangers, for a ride in their automobile or other road vehicle to travel a distance that may either be short or long...

or payment basis
• Market-based
Market economy
A market economy is an economy in which the prices of goods and services are determined in a free price system. This is often contrasted with a state-directed or planned economy. Market economies can range from hypothetically pure laissez-faire variants to an assortment of real-world mixed...

carpooling with pre-negotiated financial incentives for the driver

### Urban planning and design

City planning
Urban planning
Urban planning incorporates areas such as economics, design, ecology, sociology, geography, law, political science, and statistics to guide and ensure the orderly development of settlements and communities....

and urban design
Urban design
Urban design concerns the arrangement, appearance and functionality of towns and cities, and in particular the shaping and uses of urban public space. It has traditionally been regarded as a disciplinary subset of urban planning, landscape architecture, or architecture and in more recent times has...

practices can have a huge impact on levels of future traffic congestion, though they are of limited relevance for short-term change.
• Grid plan
Grid plan
The grid plan, grid street plan or gridiron plan is a type of city plan in which streets run at right angles to each other, forming a grid...

s including Fused Grid
Fused Grid
The Fused Grid is a street network pattern first proposed in 2002 and subsequently applied in Calgary, Alberta and in Stratford, Ontario . It represents a synthesis of two well known and extensively used network concepts: the "grid" and the “Radburn” pattern, derivatives of which are found in most...

road network geometry, rather than tree-like network topology
Network topology
Network topology is the layout pattern of interconnections of the various elements of a computer or biological network....

which branches into cul-de-sac
Cul-de-sac
A cul-de-sac is a word of French origin referring to a dead end, close, no through road or court meaning dead-end street with only one inlet/outlet...

s (which reduce local traffic, but increase total distances driven and discourage walking by reducing connectivity). This avoids concentration of traffic on a small number of arterial road
An arterial road, or arterial thoroughfare, is a high-capacity urban road. The primary function of an arterial road is to deliver traffic from collector roads to freeways, and between urban centres at the highest level of service possible. As such, many arteries are limited-access roads, or feature...

s and allows more trips to be made without a car.
• Zoning laws that encourage mixed-use development
Mixed-use development
Mixed-use development is the use of a building, set of buildings, or neighborhood for more than one purpose. Since the 1920s, zoning in some countries has required uses to be separated. However, when jobs, housing, and commercial activities are located close together, a community's transportation...

, which reduces distances between residential, commercial, retail, and recreational destinations (and encourage cycling and walking)
• Carfree cities, car-light cities, and eco-cities designed to eliminate the need to travel by car for most inhabitants.
• Transit-oriented development
Transit-oriented development
A transit-oriented development is a mixed-use residential or commercial area designed to maximize access to public transport, and often incorporates features to encourage transit ridership...

are residential and commercial areas designed to maximize access to public transport.

### Supply and demand

Congestion can be reduced by either increasing road capacity (supply), or by reducing traffic (demand). Capacity can be increased in a number of ways, but needs to take account of latent 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...

otherwise it may be used more strongly than anticipated. Critics of the approach of adding capacity have compared it to "fighting obesity
Obesity
Obesity is a medical condition in which excess body fat has accumulated to the extent that it may have an adverse effect on health, leading to reduced life expectancy and/or increased health problems...

by letting out your belt" (inducing demand that did not exist before). Reducing road capacity has in turn been attacked as removing free choice as well as increasing travel costs and times.

Increased supply can include:
• Adding more capacity at bottlenecks (such as by adding more lanes at the expense of hard shoulders or safety zones, or by removing local obstacles like bridge supports and widening tunnels)
• Adding more capacity over the whole of a route (generally by adding more lanes)
• Creating new routes
• Traffic management improvements (see separate section below)

Reduction of demand can include:
• Parking restrictions
Parking
Parking is the act of stopping a vehicle and leaving it unoccupied for more than a brief time. Parking on one or both sides of a road is commonly permitted, though often with restrictions...

, making motor vehicle use less attractive by increasing the monetary and non-monetary costs of parking, introducing greater competition for limited city or road space. Most transport planning experts agree that free parking distorts the market in favour of car travel, exacerbating congestion.
• Park and ride
Park and ride
Park and ride facilities are car parks with connections to public transport that allow commuters and other people wishing to travel into city centres to leave their vehicles and transfer to a bus, rail system , or carpool for the rest of their trip...

facilities allowing parking at a distance and allowing continuation by public transport
Public transport
Public transport is a shared passenger transportation service which is available for use by the general public, as distinct from modes such as taxicab, car pooling or hired buses which are not shared by strangers without private arrangement.Public transport modes include buses, trolleybuses, trams...

or ride sharing. Park-and-ride car parks are commonly found at metro station
Metro station
A metro station or subway station is a railway station for a rapid transit system, often known by names such as "metro", "underground" and "subway". It is often underground or elevated. At crossings of metro lines, they are multi-level....

s, freeway entrances in suburban areas, and at the edge of smaller cities.
• Reduction of road capacity to force traffic onto other travel modes
Modal share
Modal share, Mode split or Modal split, is a traffic / transport term that describes the number of trips or percentage of travelers using a particular type of transportation....

. Methods include traffic calming
Traffic calming
Traffic calming is intended to slow or reduce motor-vehicle traffic in order to improve the living conditions for residents as well as to improve safety for pedestrians and cyclists. Urban planners and traffic engineers have many strategies for traffic calming...

and the shared space
Shared space
Shared space is an urban design concept aimed at integrated use of public spaces. It encourages traffic engineers, urban planners and experts from other fields to consult with users of public space when planning and designing streets and squares in both built and non-built environments...

concept.
Road pricing is an economic concept regarding the various direct charges applied for the use of roads. The road charges includes fuel taxes, licence fees, parking taxes, tolls, and congestion charges, including those which may vary by time of day, by the specific road, or by the specific vehicle...

, charging money for access onto a road/specific area at certain times, congestion levels or for certain road users
• "Cap and trade", in which only licensed cars are allowed on the roads. A limited quota of car licences are issued each year and traded in a free market
Free market
A free market is a competitive market where prices are determined by supply and demand. However, the term is also commonly used for markets in which economic intervention and regulation by the state is limited to tax collection, and enforcement of private ownership and contracts...

fashion. This guarantees that the number of cars does not exceed road capacity while avoiding the negative effects of shortages
Economic shortage
Economic shortage is a term describing a disparity between the amount demanded for a product or service and the amount supplied in a market. Specifically, a shortage occurs when there is excess demand; therefore, it is the opposite of a surplus....

normally associated with quotas. However since demand for cars tends to be inelastic, the result are exorbitant purchase prices for the licenses, pricing out the lower levels of society, as seen Singapore's Certificate of Entitlement
Certificate of Entitlement
The Certificate of Entitlement , instituted by the government of Singapore since May 1990, is a program designed to limit car ownership and hence the number of vehicles on the country's roads...

scheme.
• Congestion pricing
Congestion pricing
Congestion pricing or congestion charges is a system of surcharging users of a transport network in periods of peak demand to reduce traffic congestion. Examples include some toll-like road pricing fees, and higher peak charges for utilities, public transport and slots in canals and airports...

, where a certain area, such as the inner part of a congested city, is surrounded with a cordon
Cordon
A cordon is also a line of people, military posts, or ships surrounding an area to close or guard it.Cordon may also refer to:* Cordon and search, a military operation...

into which entry with a car requires payment. The cordon may be a physical boundary (i.e., surrounded by toll stations) or it may be virtual, with enforcement being via spot checks or cameras on the entry routes. Major examples are Singapore
Singapore
Singapore , officially the Republic of Singapore, is a Southeast Asian city-state off the southern tip of the Malay Peninsula, north of the equator. An island country made up of 63 islands, it is separated from Malaysia by the Straits of Johor to its north and from Indonesia's Riau Islands by the...

The Electronic Road Pricing scheme is an electronic toll collection scheme adopted in Singapore to manage traffic by road pricing, and as a usage-based taxation mechanism to complement the purchase-based Certificate of Entitlement system...

, the London congestion charge
London congestion charge
The London congestion charge is a fee charged for some categories of motor vehicle to travel at certain times within the Congestion Charge Zone , a traffic area in London. The charge aims to reduce congestion, and raise investment funds for London's transport system...

system, Stockholm congestion tax
Stockholm congestion tax
The Stockholm congestion tax , also found referred to as the Stockholm congestion charge, is a congestion pricing system implemented as a tax levied on most vehicles entering and exiting central Stockholm, Sweden...

and the use of HOT lanes predominately in North America.
Road space rationing is a travel demand management strategy aimed to reduce the negative externalities generated by peak urban travel demand in excess of available supply or road capacity, through artificially restricting demand by rationing the scarce common good road capacity, especially...

, where regulatory restrictions prevent certain types of vehicles from driving under certain circumstances or in certain areas.
• Number plate
Number plate
A number plate may be:* a vehicle registration plate* a plate attached to a locomotive indicating their number, particularly in the UK and Australia, which are often collected as memorabilia....

restrictions based on days of the week, as practiced in several large cities in the world, such as Athens
Athens
Athens , is the capital and largest city of Greece. Athens dominates the Attica region and is one of the world's oldest cities, as its recorded history spans around 3,400 years. Classical Athens was a powerful city-state...

, 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...

and São Paulo. In effect, such cities are banning a different part of the automobile fleet from roads each day of the week. Mainly introduced to combat smog
Smog
Smog is a type of air pollution; the word "smog" is a portmanteau of smoke and fog. Modern smog is a type of air pollution derived from vehicular emission from internal combustion engines and industrial fumes that react in the atmosphere with sunlight to form secondary pollutants that also combine...

, these measures also reduce congestion. A weakness of this method is that richer drivers can purchase a second or third car to circumvent the ban.
• Permit
Permit
Permit may refer to:*Permit *Various legal licenses:*License*Work permit*Learner's permit*Permit to travel*Construction permit*Home Return Permit*One-way Permit*Permit is the common name for the Trachinotus falcatus, a type of Pompano....

s, where only certain types of vehicles (such as residents) are permitted to enter a certain area, and other types (such as through-traffic) are banned. For example, Bertrand Delanoë
Bertrand Delanoë
Bertrand Delanoë is a French politician, and has been the mayor of Paris since 2001. He is member of the Socialist Party . Delanoë was born in Tunis, Tunisia to a French-Tunisian father and a French mother...

, the mayor of Paris, has proposed to impose a complete ban on motor vehicles in the city's inner districts, with exemptions only for residents, businesses, and the disabled.
• Policy
Policy
A policy is typically described as a principle or rule to guide decisions and achieve rational outcome. The term is not normally used to denote what is actually done, this is normally referred to as either procedure or protocol...

approaches, which usually attempt to provide either strategic alternatives or which encourage greater usage of existing alternatives through promotion, subsidies or restrictions.
• Incentives to use public transport
Public transport
Public transport is a shared passenger transportation service which is available for use by the general public, as distinct from modes such as taxicab, car pooling or hired buses which are not shared by strangers without private arrangement.Public transport modes include buses, trolleybuses, trams...

, increasing modal shares. This can be achieved through infrastructure investment, subsidies, transport integration
Intermodal passenger transport
Intermodal passenger transport involves more than one mode of transport of passengers. Some modes of transportation have always been intermodal; for example, most major airports have extensive facilities for automobile parking and have good rail or bus connections to the cities nearby. Urban bus...

, pricing strategies that decrease the marginal cost
Marginal cost
In economics and finance, marginal cost is the change in total cost that arises when the quantity produced changes by one unit. That is, it is the cost of producing one more unit of a good...

/fixed cost
Fixed cost
In economics, fixed costs are business expenses that are not dependent on the level of goods or services produced by the business. They tend to be time-related, such as salaries or rents being paid per month, and are often referred to as overhead costs...

ratios, improved timetabling
Public transport timetable
A public transport timetable is a representation of public transport information to assist a passenger with planning a trip using public transport. A timetable details when vehicle will arrive and depart specified locations and may be organised for by route or for a particular stop...

and greater priority for buses to reduce journey time e.g. [Bus Lanes], [BTR] .
• Cycling
Utility cycling
Utility cycling encompasses any cycling not done primarily for fitness, recreation such as cycle touring, or sport such as cycle racing, but simply as a means of transport...

promotion through legislation, cycle facilities, subsidies, and awareness campaigns. The Netherlands has been pursuing cycle friendly policies
Cycling in the Netherlands
Cycling in the Netherlands is a common and popular method of both transport and also recreation. The country is well equipped with cycle-paths and other segregated cycle facilities. The network reaches all parts of the nation and into the bordering nations of Belgium and Germany...

for decades, and around a quarter of their commuting is done by bicycle.
• Telecommuting
Telecommuting
Telecommuting or telework is a work arrangement in which employees enjoy flexibility in working location and hours. In other words, the daily commute to a central place of work is replaced by telecommunication links...

encouraged through legislation and subsidies.
• Online shopping promotion, potentially with automated delivery booths
Packstation
Packstation is a service run by DHL Parcel Germany, a business unit of Deutsche Post's Mail division, in Germany. It provides automated booths for self-service collection of parcels and oversize letters as well as self-service dispatch of parcels 24 hours a day, seven days a week. Packstation...

helping to solve the last mile problem
Last mile (transportation)
Last mile is a term used in supply chain management and transportation planning to describe the movement of people and goods from a transport hub to a final destination.-Usage in distribution networks:...

and reduce shopping trips made by car.

### Traffic management

Use of so-called 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...

, which guide traffic:
• Traffic reporting
Traffic reporting
Traffic reporting is the distribution of information about road conditions such as traffic congestion, detours, and traffic accidents, generally as part of a radio or television broadcast program. The reports help commuters anticipate and avoid traffic problems. Many reports mention alternate...

Global Positioning System
The Global Positioning System is a space-based global navigation satellite system that provides location and time information in all weather, anywhere on or near the Earth, where there is an unobstructed line of sight to four or more GPS satellites...

or possibly mobile phone
Mobile phone
A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...

• Variable message sign
Variable message sign
A variable- message sign, often abbreviated VMS, CMS, or DMS, and in the UK known as a matrix sign,...

An automotive navigation system is a satellite navigation system designed for use in automobiles. It typically uses a GPS navigation device to acquire position data to locate the user on a road in the unit's map database. Using the road database, the unit can give directions to other locations...

s, possibly linked up to automatic traffic reporting
• Traffic counters permanently installed, to provide real-time traffic counts
• Convergence indexing road traffic monitoring, to provide information on the use of highway on-ramps
• Automated highway systems, a future idea which could reduce the safe interval between cars (required for braking in emergencies) and increase highway capacity by as much as 100% while increasing travel speeds
• Parking guidance and information
Parking guidance and information
Parking guidance and information systems, or car park guidance systems, present drivers with dynamic information on parking within controlled areas. The systems combine traffic monitoring, communication, processing and variable message sign technologies to provide the service...

• Active Traffic Management
Active Traffic Management
Active traffic management , also known as managed lanes or smart lanes, is a scheme for improving traffic flow and reducing congestion on motorways. It has been implemented in several countries, including Germany, the United Kingdom, and the United States...

system opens up UK motorway hard shoulder as an extra traffic lane, it uses CCTV and VMS to control and monitor the traffic's use of the extra lane

### Other associated

• School opening times
School
A school is an institution designed for the teaching of students under the direction of teachers. Most countries have systems of formal education, which is commonly compulsory. In these systems, students progress through a series of schools...

arranged to avoid 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...

traffic (in some countries, private car school pickup and drop-off traffic are substantial percentages of peak hour traffic).
• Considerate driving
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...

behaviour promotion and enforcement. Driving practices such as tailgating
Tailgating
Tailgating is the practice of driving on a road too close to the vehicle in front, at a distance which does not guarantee that stopping to avoid collision is possible...

and frequent lane changes can reduce a road's capacity and exacerbate jams. In some countries signs are placed on highways to raise awareness, while others have introduced legislation against inconsiderate driving.
• Visual barrier
Barrier
A barrier or barricade is a physical structure which blocks or impedes something.Barrier may also refer to:-Physical barriers:* Automatic full barriers, which serve to block roads at railway crossings...

s to prevent drivers from slowing down out of curiosity (often called "rubbernecking" in the United States). This often includes accidents, with traffic slowing down even on roadsides physically separated from the crash location. This also tends to occur at construction sites, which is why some countries have introduced rules that motorway construction has to occur behind visual barrier
• 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...

reductions, as practiced on the M25 motorway
M25 motorway
The M25 motorway, or London Orbital, is a orbital motorway that almost encircles Greater London, England, in the United Kingdom. The motorway was first mooted early in the 20th century. A few sections, based on the now abandoned London Ringways plan, were constructed in the early 1970s and it ...

in London. With lower speeds allowing cars to drive closer together, this increases the capacity of a road. Note that this measure is only effective if the interval between cars is reduced, not the distance itself. Low intervals are generally only safe at low speeds.
• Lane splitting/filtering
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....

, where space-efficient vehicles, usually motorcycle
Motorcycle
A motorcycle is a single-track, two-wheeled motor vehicle. Motorcycles vary considerably depending on the task for which they are designed, such as long distance travel, navigating congested urban traffic, cruising, sport and racing, or off-road conditions.Motorcycles are one of the most...

s, scooters, and ultra-narrow cars
Commuter Cars Tango
The Tango is an ultra-narrow electric sports car initially designed and built by Commuter Cars, an American company based in Spokane, Washington, that sells this car worldwide for \$108,000....

ride or drive in the space between cars, buses, and trucks. This is however illegal in many countries as it is perceived as a safety risk.

### Australia

Traffic during peak hours in major Australian cities, such as Melbourne, Sydney, Brisbane and Perth, is usually very congested and can cause considerable delay for motorists. Australians rely mainly on radio and television to obtain current traffic information. GPS, webcams, and online resources are increasingly being used to monitor and relay traffic conditions to motorists. Measures put in place by the federal and state government to combat traffic congestion include construction of new road infrastructure and increased investment in public transport.
In Brisbane, ongoing road works projects on many major roads have caused ongoing congestion throughout the city and increased commutes considerably.

### Brazil

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...

the recent records of traffic jams over the major big cities are recognized by public authorities as one of the main challenges for São Paulo, Rio de Janeiro
Rio de Janeiro
Rio de Janeiro , commonly referred to simply as Rio, is the capital city of the State of Rio de Janeiro, the second largest city of Brazil, and the third largest metropolitan area and agglomeration in South America, boasting approximately 6.3 million people within the city proper, making it the 6th...

, Belo Horizonte
Belo Horizonte
Belo Horizonte is the capital of and largest city in the state of Minas Gerais, located in the southeastern region of Brazil. It is the third largest metropolitan area in the country...

, Brasilia
Brasília
Brasília is the capital city of Brazil. The name is commonly spelled Brasilia in English. The city and its District are located in the Central-West region of the country, along a plateau known as Planalto Central. It has a population of about 2,557,000 as of the 2008 IBGE estimate, making it the...

, Curitiba
Curitiba
Curitiba is the capital of the Brazilian state of Paraná. It is the largest city with the biggest economy of both Paraná and southern Brazil. The population of Curitiba numbers approximately 1.75 million people and the latest GDP figures for the city surpass US\$61 billion according to...

and Porto Alegre
Porto Alegre
Porto Alegre is the tenth most populous municipality in Brazil, with 1,409,939 inhabitants, and the centre of Brazil's fourth largest metropolitan area . It is also the capital city of the southernmost Brazilian state of Rio Grande do Sul. The city is the southernmost capital city of a Brazilian...

, where due to the country's economic bonanza, the automobile fleets have almost doubled in several of these cities from 2000 to 2008.

According to Time
Time (magazine)
Time is an American news magazine. A European edition is published from London. Time Europe covers the Middle East, Africa and, since 2003, Latin America. An Asian edition is based in Hong Kong...

magazine, São Paulo has the world's worst daily traffic jams. On June 10, 2009, the historical record was set with more than 293 kilometres (182 mi) of accumulated queues out of 835 km (522 mi) being monitored. Despite implementation since 1997 of road space rationing
Road space rationing is a travel demand management strategy aimed to reduce the negative externalities generated by peak urban travel demand in excess of available supply or road capacity, through artificially restricting demand by rationing the scarce common good road capacity, especially...

by the last digit of the plate number during rush hours every weekday, traffic in this 20 million city still experiences severe congestion. According to experts, this is due to the accelerated rate of motorization occurring since 2003, in São Paulo the fleet is growing at a rate of 7.5% per year, with almost 1,000 new cars bought in the city every day, and the limited capacity of public transport
Public transport
Public transport is a shared passenger transportation service which is available for use by the general public, as distinct from modes such as taxicab, car pooling or hired buses which are not shared by strangers without private arrangement.Public transport modes include buses, trolleybuses, trams...

. The subway has only 61 kilometres (37.9 mi) of lines, though 35 further kilometres are under construction or planned by 2010. Every day, many citizens spend between three up to four hours behind the wheel. In order to mitigate the aggravating congestion problem, since June 30, 2008 the road space rationing program was expanded to include and restrict trucks and light commercial vehicles.

According to the Toronto Board of Trade, in 2010, Toronto
Toronto
Toronto is the provincial capital of Ontario and the largest city in Canada. It is located in Southern Ontario on the northwestern shore of Lake Ontario. A relatively modern city, Toronto's history dates back to the late-18th century, when its land was first purchased by the British monarchy from...

is ranked as the most congested city of 19 surveyed cities, with an average commute time of 80 minutes.

### China

The August 2010 China National Highway 110 traffic jam
China National Highway 110 traffic jam
The China National Highway 110 traffic jam was a recurring massive traffic jam that began to form on August 14, 2010, mostly on China National Highway 110 and Beijing–Tibet expressway , in Beijing, Hebei and Inner Mongolia. The traffic jam slowed down thousands of vehicles for more than and has...

in Hebei
Hebei
' is a province of the People's Republic of China in the North China region. Its one-character abbreviation is "" , named after Ji Province, a Han Dynasty province that included what is now southern Hebei...

province, China
People's Republic of China
China , officially the People's Republic of China , is the most populous country in the world, with over 1.3 billion citizens. Located in East Asia, the country covers approximately 9.6 million square kilometres...

, is considered the world's worst traffic jam ever, as traffic congestion stretched more than 100 kilometres (62.1 mi) from August 14 to the 26, including at least 11 days of total 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...

. The event was caused by a combination of road works and thousands of coal trucks from Inner Mongolia
Inner Mongolia
Inner Mongolia is an autonomous region of the People's Republic of China, located in the northern region of the country. Inner Mongolia shares an international border with the countries of Mongolia and the Russian Federation...

’s coalfields that travel daily to Beijing. The New York Times has called this event the "Great Chinese Gridlock of 2010."

Towards the end of 2010, Beijing announced a series of drastic measures to tackle the city's traffic jam, including limiting the number of new plates issued to passenger cars to 20,000 a month and barring cars of non-Beijing plates from entering areas within the Fifth Ring Road during rush hours.

### Colombia

In Bogotá
Bogotá
Bogotá, Distrito Capital , from 1991 to 2000 called Santa Fé de Bogotá, is the capital, and largest city, of Colombia. It is also designated by the national constitution as the capital of the department of Cundinamarca, even though the city of Bogotá now comprises an independent Capital district...

the excessive traffic jams cause high levels of stress in people, and are the main cause of air pollution. The problem has been mitigated partially since 2000 through the implementation of the TransMilenio
TransMilenio
TransMilenio is a bus rapid transit system that serves Bogotá, the capital of Colombia. The system opened to the public in December 2000, covering Av. Caracas and Calle 80...

, a bus rapid transit
Bus rapid transit
Bus rapid transit is a term applied to a variety of public transportation systems using buses to provide faster, more efficient service than an ordinary bus line. Often this is achieved by making improvements to existing infrastructure, vehicles and scheduling...

system that has been improving mobility throughout the city. The city also restricts use of vehicles
Road space rationing is a travel demand management strategy aimed to reduce the negative externalities generated by peak urban travel demand in excess of available supply or road capacity, through artificially restricting demand by rationing the scarce common good road capacity, especially...

several days each week depending on the last digits of license plates. However, this system, called 'Pico y placa
Pico y placa
Pico y placa is traffic congestion mitigation policy that was initially set in place in the year 2000 in Bogotá, Colombia by then mayor Enrique Peñalosa to help regulate traffic during rush hours. The system restricts vehicles with license plate numbers ending in certain digits from travelling...

' tends to promote the purchase of second cars by the wealthy.

### Hong Kong

Hong Kong aborted a congestion pricing system
The Hong Kong Electronic Road Pricing is an electronic toll collection scheme first proposed in Hong Kong as early as in the 1980s to manage traffic by congestion pricing...

in the 1980s due to public pressure and has since relied on a vehicle high purchase tax to discourage overall car purchasing but has developed no localised congestion management techniques, However the Transport Department in Hong Kong has set up websites with maps showing congestion for the Cross Harbour Tunnel, it has also set up signs on both sides of the harbour telling drivers which is the quickest way to get to the other side of Victoria Harbour.

### Iran

Because of inadequate public transportation and high population density traffic congestion is a common problem in different cities like Mash'had, Isfahan, Shiraz and especially Tehran (capital city of Iran). Recently developing Metro and BRT systems in Tehran and strategies for limiting gas uses has been applied to reduce car using, but unfortunately the problem is still crucial.

### Netherlands

The road network in the Netherlands is usually congested in the morning and afternoon rush hour on working days. However, the rush hour periods seem to have become longer and longer and one may occasionally run into congestion any time of the day or night. Commuter traffic to and from major cities such as Amsterdam, Rotterdam, The Hague, Utrecht, Eindhoven, Zwolle, Enschede and Groningen may cause congestion. Congestion is difficult to resolve because the Netherlands is a relatively densely populated country where there is little room for expansion. Proposals for a "pay per distance travelled" is thought to discourage car driving but has not been implemented yet due to car owner resistance.

### New Zealand

New Zealand has followed strongly car-oriented transport policies since after World War II (especially in Auckland
Auckland
The Auckland metropolitan area , in the North Island of New Zealand, is the largest and most populous urban area in the country with residents, percent of the country's population. Auckland also has the largest Polynesian population of any city in the world...

, where one third of the country's population lives), and currently has one of the highest car-ownership rates per capita in the world, after the United States. Because of the negative results, congestion in the big centres is a major problem. Current measures include both the construction of new road infrastructure as well as increased investment in public transport, which had strongly declined in all cities of the country except Wellington
Wellington
Wellington is the capital city and third most populous urban area of New Zealand, although it is likely to have surpassed Christchurch due to the exodus following the Canterbury Earthquake. It is at the southwestern tip of the North Island, between Cook Strait and the Rimutaka Range...

.

### United Kingdom

In the United Kingdom the inevitability of congestion in some urban road networks has been officially recognised since the Department for Transport
Department for Transport
In the United Kingdom, the Department for Transport is the government department responsible for the English transport network and a limited number of transport matters in Scotland, Wales and Northern Ireland which are not devolved...

set down policies based on the report Traffic in Towns
Traffic in Towns
Traffic in Towns was an influential report and popular book on urban and transport planning policy produced in 1963 for the UK Ministry of Transport by a team headed by the architect, civil engineer and planner Professor Sir Colin Buchanan....

in 1963:

Even when everything that it is possibly to do by way of building new roads and expanding public transport has been done, there would still be, in the absence of deliberate limitation, more cars trying to move into, or within our cities than could possibly be accommodated..

The Department for Transport sees growing congestion as one of the most serious transport problems facing the UK. On 1 December 2006, Rod Eddington
Rod Eddington
Sir Roderick Ian Eddington is an Australian businessman. He is currently chair of the government body Infrastructure Australia, a director of News Corporation, continuing his long association with that company, and has served in other senior positions including as former CEO of British...

published a UK government-sponsored report into the future of Britain's transport infrastructure
Eddington Transport Study
The Eddington Transport Study is an examination, by Sir Rod Eddington, of the impact of transport decisions on the economy and the environment of the United Kingdom, with recommendations on how the transport network should be modernised...

. The Eddington Transport Study set out the case for action to improve road and rail networks, as a "crucial enabler of sustained productivity and competitiveness". Eddington has estimated that congestion may cost the economy of England £22 bn a year in lost time by 2025. He warned that roads were in serious danger of becoming so congested that the economy would suffer. At the launch of the report Eddington told journalists and transport industry representatives introducing road pricing
Road pricing is an economic concept regarding the various direct charges applied for the use of roads. The road charges includes fuel taxes, licence fees, parking taxes, tolls, and congestion charges, including those which may vary by time of day, by the specific road, or by the specific vehicle...

to encourage drivers to drive less was an "economic no-brainer". There was, he said "no attractive alternative". It would allegedly cut congestion by half by 2025, and bring benefits to the British economy totalling £28 bn a year.

### United States

The Texas Transportation Institute
Texas Transportation Institute
The Texas Transportation Institute in College Station, Texas is the largest transportation research agency in the United States. Created in 1950, primarily in response to the needs of the Texas Highway Department , TTI has since broadened its focus to address all modes of transportation–highway,...

estimated that, in 2000, the 75 largest metropolitan areas experienced 3.6 billion vehicle-hours of delay, resulting in 5.7 billion U.S. gallons (21.6 billion liters) in wasted fuel and \$67.5 billion in lost productivity, or about 0.7% of the nation's GDP
Gross domestic product
Gross domestic product refers to the market value of all final goods and services produced within a country in a given period. GDP per capita is often considered an indicator of a country's standard of living....

. It also estimated that the annual cost of congestion for each driver was approximately \$1,000 in very large cities and \$200 in small cities. Traffic congestion is increasing in major cities and delays are becoming more frequent in smaller cities and rural areas.

By late 2010 the five cities in the United States with the worst rush hour traffic congestion were New York City
New York City
New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...

, Washington, D.C.
Washington, D.C.
Washington, D.C., formally the District of Columbia and commonly referred to as Washington, "the District", or simply D.C., is the capital of the United States. On July 16, 1790, the United States Congress approved the creation of a permanent national capital as permitted by the U.S. Constitution....

, San Francisco, Seattle
Seattle, Washington
Seattle is the county seat of King County, Washington. With 608,660 residents as of the 2010 Census, Seattle is the largest city in the Northwestern United States. The Seattle metropolitan area of about 3.4 million inhabitants is the 15th largest metropolitan area in the country...

and Los Angeles
Los Ángeles
Los Ángeles is the capital of the province of Biobío, in the commune of the same name, in Region VIII , in the center-south of Chile. It is located between the Laja and Biobío rivers. The population is 123,445 inhabitants...

.

• 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...

, total standstill of traffic
• 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...

• Peak car
Peak car
Peak car or peak car use or peak travel is the theory that car usage rates, or overall travel rates, are dropping in at least eight major developed countries including the UK, Australia, America and Japan. Similar to peak oil, peak car theory holds that travel usage per capita reaches a peak and...

• Smeed's law
Smeed's law
Smeed's Law, named after R. J. Smeed, who first proposed the relationship in 1949, is an empirical rule relating traffic fatalities to traffic congestion as measured by the proxy of motor vehicle registrations and country population. Thus, increasing traffic volume leads to an increase in...

• 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...

, the mathematical study of traffic flows
• Transims
Transims
TRANSIMS , is an integrated set of tools developed to conduct regional transportation system analyses...

• Transportation demand management
Transportation Demand Management
Transportation demand management, traffic demand management or travel demand management is the application of strategies and policies to reduce travel demand , or to redistribute this demand in space or in time.In transport as in any network, managing demand can be a cost-effective alternative to...

, operational solutions
• 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...

• Traffic Message Channel
Traffic Message Channel
Traffic Message Channel is a technology for delivering traffic and travel information to drivers. It is typically digitally coded using the FM-RDS system on conventional FM radio broadcasts...

(TMC)
• Three-phase traffic theory
• 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...