Traffic congestion is a condition on transport 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 between vehicles slows the speed of the traffic stream, this results in some congestion.
Contents
- Causes
- Mathematical theories
- Economic theories
- Classification
- Negative impacts
- Road rage
- Positives of traffic congestion
- Countermeasures
- Road infrastructure
- Urban planning and design
- Supply and demand
- Traffic management
- Other associated
- Australia
- Bangladesh
- Brazil
- Canada
- China
- India
- Indonesia
- New Zealand
- Philippines
- Turkey
- United Kingdom
- United States of America
- References
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. Traffic congestion can lead to drivers becoming frustrated and engaging in road rage.
Mathematically, congestion is usually looked at as the number of vehicles that pass through a point in a window of time, or a flow. Congestion flow lends itself to principles of fluid dynamics.
Causes
Traffic congestion occurs when a volume of traffic or modal split generates demand for space greater than the available street capacity; this point is commonly termed saturation. 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) 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 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 effects"), such as an abrupt steering maneuver by a single motorist. Traffic scientists liken such a situation to the sudden freezing of supercooled fluid.
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's three-phase traffic theory (see also spatiotemporal reconstruction of traffic congestion).
Because of the poor correlation of theoretical models to actual observed traffic flows, transportation planners and highway engineers attempt to forecast traffic flow using empirical models. Their working traffic models typically use a combination of macro-, micro- and mesoscopic features, and may add matrix entropy 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.
A team of MIT mathematicians has developed a model that describes the formation of "phantom jams," in which small disturbances (a driver hitting the brake too hard, or getting too close to another car) in heavy traffic can become amplified into a full-blown, self-sustaining traffic jam. Key to the 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. 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. Privatization of highways and road pricing 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 or roadworks, which may reduce the road's capacity below normal levels.
Economist Anthony Downs argues that rush hour traffic congestion is inevitable because of the benefits of having a relatively standard work day. In a capitalist economy, goods can be allocated either by pricing (ability to pay) or by queueing (first-come first-served); 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 to reduce congestion (a demand-side solution, effectively rationing demand), in turn plowing the revenues generated therefrom into public transportation projects.
A 2011 study in the The American Economic Review indicates that there may be a "fundamental law of road congestion."The researchers, from the University of Toronto and the London School of Economics, analyzed data from the U.S. Highway Performance and Monitoring System for 1983, 1993 and 2003, as well as information on population, employment, geography, transit, and political factors. They determined that the number of vehicle-kilometers traveled (VKT) increases in direct proportion to the available lane-kilometers of roadways. The implication is that building new roads and widening existing ones only results in additional traffic that continues to rise until peak congestion returns to the previous level.
Classification
Qualitative classification of traffic is often done in the form of a six letter A-F level of service (LOS) scale defined in the Highway Capacity Manual, a US document used (or used as a basis for national guidelines) worldwide. These levels are used by transportation engineers as a shorthand 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 found in measured traffic data. Common spatiotemporal empirical features of traffic congestion are those features, which are qualitatively the same for different highways in different countries measured during years of traffic observations. Common features of traffic congestion are independent on weather, 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’s 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 models.
Negative impacts
Traffic congestion has a number of negative effects:
Road rage
Road rage is 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 which result in injuries and even deaths. It can be thought of as an extreme case of aggressive driving.
The term originated in the United States in 1987–1988 (specifically, from Newscasters at KTLA, a local television station), when a rash of freeway shootings occurred on the 405, 110 and 10 freeways in Los Angeles, California. These shooting sprees even spawned a response from the AAA Motor Club to its members on how to respond to drivers with road rage or aggressive maneuvers and gestures.
Positives of traffic congestion
Congestion has the benefit of encouraging motorists to re-time their trips so that expensive road space is in full use for a greater number of hours per day.
The standard response to congestion is to expand road space somehow, perhaps by widening an existing road or else by adding a new road, bridge or tunnel. However, this could well result in increased traffic flow, otherwise known as induced demand, causing congestion to appear somewhere else. Moreover, Braess' paradox shows that adding road capacity might make congestion worse even if demand does not increase.
It has been argued that traffic congestion, by reducing road speeds in cities, could reduce the frequency and severity of road accidents.
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.
Road infrastructure
Urban planning and design
City planning and urban design practices can have a huge impact on levels of future traffic congestion, though they are of limited relevance for short-term change.
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 otherwise it may be used more strongly than anticipated. Critics of the approach of adding capacity have compared it to "fighting obesity by letting out your belt" (inducing demand that did not exist before). For example, when new lanes are created, households with a second car that used to be parked most of the time may begin to use this second car for commuting. Reducing road capacity has in turn been attacked as removing free choice as well as increasing travel costs and times, placing an especially high burden on the low income residents who must commute to work.
Increased supply can include:
Reduction of demand can include:
Traffic management
Use of so-called Intelligent transportation system, which guide traffic:
Other associated
Australia
Traffic during peak hours in major Australian cities, such as Sydney, Melbourne, 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.
Bangladesh
Traffic jams have become intolerable in Dhaka. Some other major reasons are the total absence of a rapid transit system; the lack of an integrated urban planning scheme for over 30 years; poorly maintained road surfaces, with potholes rapidly eroded further by frequent flooding and poor or non-existent drainage; haphazard stopping and parking; poor driving standards; total lack of alternative routes, with several narrow and (nominally) one-way roads.
Brazil
According to Time magazine, São Paulo has the world's worst daily traffic jams. Based on reports from the Companhia de Engenharia de Tráfego, the city's traffic management agency, the historical congestion record was set on May 23, 2014, with 344 kilometres (214 mi) of cumulative queues around the city during the evening rush hour. The previous record occurred on November 14, 2013, with 309 kilometres (192 mi) of cumulative queues.
Despite implementation since 1997 of road space rationing by the last digit of the plate number during rush hours every weekday, traffic in this 20-million-strong city still experiences severe congestion. According to experts, this is due to the accelerated rate of motorization occurring since 2003 and the limited capacity of public transport. In São Paulo, traffic is growing at a rate of 7.5% per year, with almost 1,000 new cars bought in the city every day. The subway has only 61 kilometres (38 mi) of lines, though 35 further kilometers 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.
Canada
According to the Toronto Board of Trade, in 2010, Toronto 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 in Hebei province, China, is considered the world's worst traffic jam ever, as traffic congestion stretched more than 100 kilometres (62 mi) from August 14 to the 26, including at least 11 days of total gridlock. The event was caused by a combination of road works and thousands of coal trucks from Inner Mongolia’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.
India
The number of vehicles in India is quickly increasing as a growing middle class can now afford to buy cars. As a result, India has launched various rapid transit efforts, such as the Kolkata Metro, in Kolkata, and the Rapid Metro, in Gurgaon.
India's road conditions are not expanding / improving in proportion with the increase in vehicle numbers. For example, lets take the case of Kerala, a small southern state having the above characteristics. The state has less than average (around 30m)width of major highways in the nation (45 m), though the roads are better surfaced and maintained in Kerala. This causes considerable difficulty to the road users and causes frequent mishaps, though road discipline and adherence to traffic rules (and enforcement) is considered as better in Kerala.
Various causes for this include:
Indonesia
According to a 2015 study by motor oil company Castrol, Jakarta is found to be the worst city in the world for traffic congestion. Relying on information from TomTom navigation devices in 78 countries, the index found that drivers are stopping and starting their cars 33,240 times per year on the road. After Jakarta, the worst cities for traffic are Istanbul, Mexico City, Surabaya, and St. Petersburg.
Daily congestion in Jakarta is not a recent problem. The expansion of commercial area shows worsening daily congestion in Jalan Jendral Sudirman, Jalan Thamrin, and Jalan Gajah Mada in mid 1970s.
In 2016, 12 people died as a result of traffic congestion in Java. They were among those stuck in a three-day traffic jam at an intersection in Java called 'Brexit'. The traffic block stretched for 21 km here and thousands of cars clogged the highway. Many people died because of carbon monoxide poisoning, fatigue or heat.
New Zealand
New Zealand has followed strongly car-oriented transport policies since after World War II (especially in Auckland, where one third of the country's population lives, is New Zealand's most traffic congested city, and has been labelled worse than New York for traffic congestion with commuters sitting in traffic congestion for 95 hours per year), and currently has one of the highest car-ownership rates per capita in the world, after the United States. Traffic congestion in New Zealand is increasing with drivers on New Zealand's motorways reported to be struggling to exceed 20 kph on an average commute, sometimes crawling along at 8 kph for more than half an hour.
Philippines
According to a survey by Waze, traffic congestion in Metro Manila is called the "worst" in the world, after Rio de Janeiro, São Paulo, and Jakarta. It is worsened by violations of traffic laws, like illegal parking, loading and unloading, beating the red light, and wrong-way driving. Traffic congestion in Metro Manila is caused by the large number of registered vehicles, lack of roads, and overpopulation, especially on Manila, Pateros and Caloocan. Traffic caused losses of ₱137,500,000,000 on the economy in 2011, and unbuilt roads and railway projects also causes worsening congestion. The Japan International Cooperation Agency (JICA) feared that daily economic losses will reach Php 6,000,000,000 by 2030 if traffic congestion cannot be controlled.
Turkey
In recent years, the Istanbul Metropolitan Municipality has made huge investments on intelligent transportation systems and public transportation. Despite that, traffic is a significant problem in İstanbul. İstanbul has chosen the second most congested and the most sudden-stopping traffic in the world. Travel times in Turkey’s largest city take on average 55 percent longer that they should, even in relatively less busy hours.
United Kingdom
In the United Kingdom the inevitability of congestion in some urban road networks has been officially recognized since the Department for Transport set down policies based on the report Traffic in Towns 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 published a UK government-sponsored report into the future of Britain's transport infrastructure. 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 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 of America
The Texas Transportation Institute 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. 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.
30% of traffic is cars looking for parking.
According to traffic analysis firm INRIX in 2013, the top 65 worst US traffic congested cities (measured in average hours wasted per vehicle for the year) were:
- Los Angeles, California: 64.4 hours;
- Honolulu, Hawaii: 59.5 hours;
- San Francisco, California: 56.1 hours;
- New York, New York: 52.9 hours;
- Bridgeport, Connecticut: 42.1 hours;
- Austin, Texas: 41.2 hours;
- Houston, Texas: 40.6 hours;
- Washington, D.C.: 40.3 hours;
- Boston, Massachusetts: 37.9 hours;
- Seattle, Washington: 37.1 hours;
- San Jose, California: 34.7 hours;
- Chicago, Illinois: 34.2 hours;
- Dallas, Texas: 33.5 hours;
- El Paso, Texas: 32.6 hours;
- Denver, Colorado: 31.7 hours;
- New Haven, Connecticut: 31.2 hours;
- Fort Worth, Texas: 30.6 hours;
- Albuquerque, New Mexico: 29.3 hours;
- Detroit, Michigan: 28.5 hours;
- Colorado Springs, Colorado: 26.8 hours;
- St. Louis, Missouri: 25.6 hours;
- Indianapolis, Indiana: 24.9 hours;
- Baltimore, Maryland: 23.4 hours;
- Las Vegas, Nevada: 22.1 hours;
- Salt Lake City, Utah: 21.9 hours;
- Lubbock, Texas: 21.5 hours;
- Provo, Utah: 21.2 hours;
- Aurora, Colorado: 20.7 hours;
- New Orleans, Louisiana: 20.2 hours;
- Arlington, Texas: 19.8 hours;
- Hartford, Connecticut: 19.6 hours;
- Miami, Florida: 19.5 hours;
- Tampa, Florida: 19.4 hours;
- Daytona Beach, Florida: 19.2 hours;
- Boise, Idaho: 18.7 hours;
- Rio Rancho, New Mexico: 18.4 hours;
- Wichita, Kansas: 18.1 hours;
- Mobile, Alabama: 17.6 hours;
- Fort Collins, Colorado: 16.9 hours;
- Kansas City, Missouri: 16.7 hours;
- Columbia, Missouri: 16.3 hours;
- Abilene, Texas: 16.1 hours;
- Sacramento, California: 15.8 hours;
- Midland, Texas: 15.4 hours;
- Westminster, Colorado: 14.7 hours;
- Plano, Texas: 14.5 hours;
- Temple, Texas: 14.2 hours;
- Loveland, Colorado: 13.8 hours;
- Amarillo, Texas: 13.2 hours;
- Odessa, Texas: 12.8 hours;
- San Antonio, Texas: 12.7 hours;
- Galveston, Texas: 12.6 hours;
- Golden, Colorado: 12.3 hours;
- Greeley, Colorado: 11.8 hours;
- Santa Barbara, California: 11.6 hours;
- Anchorage, Alaska: 10.9 hours;
- Olympia, Washington: 10.7 hours;
- Harrisburg, Pennsylvania: 10.6 hours;
- Columbus, Ohio: 10.4 hours;
- Portland, Oregon: 10.2 hours;
- Redding, California: 9.8 hours;
- Frederick, Maryland: 9.7 hours;
- Castle Rock, Colorado: 9.6 hours;
- Frisco, Texas: 9.4 hours;
- Trenton, New Jersey: 9.3 hours;
The most congested highway in the United States, according to a 2010 study of freight congestion (truck speed and travel time), is Chicago's Interstate 290 at the Circle Interchange. The average truck speed was just 29 mph (47 km/h).