View source for Traffic congestion

{{Short description|Transport condition characterized by slower speed and high density}}
{{Redirect|Traffic jam}}
{{Use mdy dates|date=October 2023}}
{{Use American English|date=June 2022}} 
[[File:6th Avenue from 49th.jpg|thumb|300px|Congested [[Sixth Avenue]] in [[Midtown Manhattan|Midtown]] [[Manhattan]], [[New York City]], which leads the world in urban automobile traffic congestion,<ref name=NYCCongestion>{{cite web|url=https://www.economist.com/united-states/2024/11/21/congestion-pricing-in-new-york-gets-the-go-ahead-after-all-maybe|title=Congestion pricing in New York gets the go-ahead after all. Maybe|publisher=The Economist|date=November 21, 2024|access-date=November 21, 2024|quote=But traffic is bad most days, with more than 900,000 cars entering Manhattan’s central business district. INRIX, a traffic-data firm, found that New York City leads the world in urban traffic congestion among the cities scored, with the average driver stationary for 101 hours a year.}}</ref> but which has implemented [[Congestion pricing in New York City|congestion pricing]] in January 2025 to address the gridlock]]

'''Traffic congestion''' is a condition in transport that is characterized by slower speeds, longer trip times, and increased vehicular [[Queuing theory|queueing]]. Traffic congestion on urban road networks has increased substantially since the 1950s, resulting in many of the roads becoming obsolete.<ref>{{Cite book|title=Encyclopedia of the City|last=Caves|first=R. W.|publisher=Routledge|year=2004|pages=141}}</ref> When traffic demand is great enough that the interaction between vehicles slows the traffic stream, this results in congestion. While congestion is a possibility for any [[mode of transportation]], this article will focus on automobile congestion on public roads. Mathematically, traffic is modeled as a flow through a fixed point on the route, analogously to [[fluid dynamics]].

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 known as a '''traffic jam''',<ref>{{Cite book|url=https://books.google.com/books?id=sWiUjVAGTVgC&q=traffic+jam|title=Traffic Flow Dynamics: Data, Models and Simulation|last1=Treiber|first1=Martin|last2=Kesting|first2=Arne|date=October 11, 2012|publisher=Springer Science & Business Media|isbn=978-3-642-32459-8|language=en|access-date=October 29, 2020|archive-date=March 30, 2021|archive-url=https://web.archive.org/web/20210330012623/https://books.google.com/books?id=sWiUjVAGTVgC&q=traffic+jam|url-status=live}}</ref><ref>{{Cite book|url=https://books.google.com/books?id=XikpAQAAMAAJ&q=Traffic+jam%22|title=Traffic Flow Fundamentals|last=May|first=Adolf Darlington|date=1990|publisher=Prentice Hall|isbn=9780139260728|language=en|access-date=October 29, 2020|archive-date=March 30, 2021|archive-url=https://web.archive.org/web/20210330012608/https://books.google.com/books?id=XikpAQAAMAAJ&q=Traffic+jam%22|url-status=live}}</ref> a '''traffic snarl-up''' (informally)<ref>{{Cite book|url=https://books.google.com/books?id=WVssAQAAMAAJ&q=Journal+article:+%22Traffic+snarl-up%22|title=Hotelier & Caterer: Official Magazine of FEDHASA.|date=July 1993|publisher=Ramsay Son & Parker|language=en|access-date=October 29, 2020|archive-date=March 30, 2021|archive-url=https://web.archive.org/web/20210330012550/https://books.google.com/books?id=WVssAQAAMAAJ&q=Journal+article%3A+%22Traffic+snarl-up%22|url-status=live}}</ref><ref>{{Cite book|url=https://books.google.com/books?id=4o23AAAAIAAJ&q=Journal+article:+%22Traffic+snarl-up%22|title=Eve: The Essence of Africa's New Woman|date=2004|publisher=Oakland Media Services Limited|language=en|access-date=October 29, 2020|archive-date=March 30, 2021|archive-url=https://web.archive.org/web/20210330012550/https://books.google.com/books?id=4o23AAAAIAAJ&q=Journal+article%3A+%22Traffic+snarl-up%22|url-status=live}}</ref> or a '''tailback'''.<ref>{{cite web |title=TAILBACK |url=https://dictionary.cambridge.org/dictionary/english/tailback |publisher=[[Cambridge Dictionary]]}}</ref> Drivers can become frustrated and engage in [[road rage]]. Drivers and driver-focused road planning departments commonly propose to alleviate congestion by adding another lane to the road. This is ineffective: increasing road capacity [[Induced demand|induces more demand]] for driving.

==Causes==
{{Pie chart
| caption= Causes of traffic congestion:<ref>{{Cite web |date=October 2005 |title=An Initial Assessment of Freight Bottlenecks on Highways |url=https://www.fhwa.dot.gov/policy/otps/bottlenecks/bottlenecks.pdf |url-status=live |archive-url=https://web.archive.org/web/20230601123756/https://www.fhwa.dot.gov/policy/otps/bottlenecks/bottlenecks.pdf |archive-date=June 1, 2023 |access-date=June 9, 2023 |website=Federal Highway Administration |publisher=Cambridge Systematics, Inc.}}</ref>
| label1 = [[Traffic bottleneck|Bottlenecks]]
| value1 = 40
| label2 = [[Traffic collision|Traffic incidents]]
| value2 = 25
| label3 = [[Roadworks|Work zones]]
| value3 = 10
| label4 = Bad weather
| value4 = 15
| label5 = Poor signal timing
| value5 = 5
| label6 = Special events / other
| value6 = 5
}}[[File:Traffic Jam in Egypt.jpg|thumb|Traffic jam - traffic on the Cairo-Assiut highway is blocked due to fog.]]
[[File:Traffic jam Marginal Pinheiros 6122 SAO 07 2009.jpg|thumb|Traffic congestion on Marginal Pinheiros, near downtown [[São Paulo]]. According to ''[[Time (magazine)|Time]]'' magazine, São Paulo has the world's worst traffic jams.<ref name=Times_SP/> Drivers are informed through [[variable message sign]]s that display the prevailing [[Queueing theory|queue length]].]]
[[File:Ayalon trafic congestion time lapse.webm|thumb|[[Time-lapse photography|Time lapse]] video of traffic congestion near HaShalom interchange in [[Highway 20 (Israel)|Highway 20]], Israel]]
Traffic congestion occurs when a volume of traffic generates demand for space greater than the available street capacity; this point is commonly termed [[Degree of saturation (traffic)|saturation]]. Several specific circumstances can 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 volume of traffic; most of the rest is attributed to traffic incidents, road work and weather events.<ref>{{cite web|title=Congestion: A National Issue|date=August 29, 2008|url=http://www.ops.fhwa.dot.gov/aboutus/opstory.htm|access-date=September 25, 2008|archive-date=July 25, 2008|archive-url=https://web.archive.org/web/20080725055811/http://www.ops.fhwa.dot.gov/aboutus/opstory.htm|url-status=dead}}</ref><ref>{{Citation|last1=Essien|first1=Aniekan|title=The Impact of Rainfall and Temperature on Peak and Off-Peak Urban Traffic|date=2018|pages=399–407|publisher=Springer International Publishing|isbn=9783319988115|last2=Petrounias|first2=Ilias|last3=Sampaio|first3=Pedro|last4=Sampaio|first4=Sandra|series=Lecture Notes in Computer Science |volume=11030 |doi=10.1007/978-3-319-98812-2_36|s2cid=52046271 |url=https://www.research.manchester.ac.uk/portal/en/publications/the-impact-of-rainfall-and-temperature-on-peak-and-offpeak-urban-traffic(dc8d3092-8b88-4ef3-97f0-f8583165308c).html|access-date=December 1, 2019|archive-date=January 26, 2020|archive-url=https://web.archive.org/web/20200126151224/https://www.research.manchester.ac.uk/portal/en/publications/the-impact-of-rainfall-and-temperature-on-peak-and-offpeak-urban-traffic(dc8d3092-8b88-4ef3-97f0-f8583165308c).html|url-status=live|url-access=subscription}}</ref> In terms of traffic operation, rainfall reduces traffic capacity and operating speeds, thereby resulting in greater congestion and road network productivity loss.

Individual incidents such as crashes or even a single car braking heavily in a previously smooth flow may cause ripple effects, a [[cascading failure]] also known as [[traffic wave]]s, which then spread out and create a sustained traffic jam when, otherwise, the normal flow might have continued for some time longer.<ref>{{cite web|url=http://www.amasci.com/amateur/traffic/traffic1.html|title=Science Hobbyist: Traffic Waves|access-date=September 29, 2003|archive-date=October 8, 2003|archive-url=https://web.archive.org/web/20031008092827/http://www.amasci.com/amateur/traffic/traffic1.html|url-status=live}}</ref>

===Separation of work and residential areas===
People often work and live in different parts of the city. Many [[workplace]]s are located in a [[central business district]] away from [[residential area]]s, resulting in workers [[commuting]]. According to a 2011 report published by the [[United States Census Bureau]], a total of 132.3 million people in the United States commuted between their work and residential areas daily.<ref>{{cite web|url=https://www.census.gov/library/publications/2011/compendia/statab/131ed/transportation.html|title=Transportation Report By USCB|access-date=May 6, 2018|archive-date=October 20, 2017|archive-url=https://web.archive.org/web/20171020182900/https://www.census.gov/library/publications/2011/compendia/statab/131ed/transportation.html|url-status=live}}</ref>

===Movement to obtain or provide goods and services===
[[File:Istanbul Otoyol 2 Richtung FSM 2.jpg|thumb|A traffic jam in [[Istanbul]], and an opportunity for two [[simit]] vendors to sell food to drivers]]
People may need to move about within the city to obtain goods and services, for instance to purchase goods or attend classes in a different part of the city. [[Brussels]], a [[Belgium|Belgian]] city with a strong service economy, has one of the worst traffic congestion in the world, wasting 74 hours in traffic in 2014.

===Economic theories===
[[File:Trafficjamdelhi.jpg|thumb|India's [[economic development in India|economic growth]] has resulted in a massive increase in the number of private vehicles on its roads overwhelming the transport infrastructure. Shown here is a traffic jam in [[Delhi]].]]

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]]. [[Private highway|Privatization of highways]] and [[road pricing]] have both been proposed as measures that may reduce congestion through economic incentives and disincentives {{Citation needed|date=June 2022}}. Congestion can also happen due to non-recurring highway incidents, such as a [[car accident|crash]] or [[road works|roadworks]], which may reduce the road's capacity below normal levels.
[[File:Traffic jam in Haikou, Hainan, China 01.jpg|thumb|right|upright=0.9|[[Economic history of China (1949–present)|Rapid economic growth]] in China has resulted in a massive increase in the number of private vehicles in its major cities. Shown here is a traffic jam in downtown [[Haikou]], [[Hainan Province]], China.]]
Economist [[Anthony Downs]] argues that [[rush hour]] traffic congestion is inevitable because of the benefits of having a relatively [[Business hours|standard work day]] {{Citation needed|date=April 2016}}. In a [[capitalism|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 system]]s, Downs advocates greater use of [[road pricing]] to reduce congestion (a demand-side solution, effectively rationing demand), in turn putting the revenues generated therefrom into [[public transportation]] projects.

A 2011 study in ''[[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.<ref>{{cite web|url=http://journalistsresource.org/studies/environment/transportation/fundamental-law-road-congestion-evidence-u-s-cities/|title=Fundamental Law of Road Congestion: Evidence from U.S. Cities|publisher=journalistsresource.org|date=November 17, 2014|access-date=March 6, 2012|archive-date=February 21, 2012|archive-url=https://web.archive.org/web/20120221083322/http://journalistsresource.org/studies/environment/transportation/fundamental-law-road-congestion-evidence-u-s-cities/|url-status=live}}</ref><ref>{{cite journal | last1 = Duranton | first1 = Gilles | last2 = Turner | first2 = Matthew A. | year = 2011 | title = The Fundamental Law of Road Congestion: Evidence from U.S. Cities | url = http://www.nber.org/papers/w15376.pdf | journal = American Economic Review | volume = 101 | issue = 6 | pages = 2616–52 | doi = 10.1257/aer.101.6.2616 | access-date = September 23, 2019 | archive-date = October 13, 2019 | archive-url = https://web.archive.org/web/20191013030946/https://www.nber.org/papers/w15376.pdf | url-status = live }}</ref>

==Classification and modeling==
Qualitative classification of traffic is often done in the form of a six-letter A–F [[Level of service (transportation)|level of service]] (LOS) scale defined in the [[Highway Capacity Manual]], a US document used (or used as a basis for national guidelines) worldwide. 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.<ref>''Traffic Engineering'', Third Edition.  Roger P. Roess, Elana S. Prassas, and William R. McShane.  {{ISBN|0-13-142471-8}}</ref>

Another classification schema of traffic congestion is associated with some [[Traffic congestion: Reconstruction with Kerner's three-phase theory|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{{what|date=February 2025}} 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 [[Boris Kerner]]'s [[three-phase traffic theory]]. The common features of traffic congestion can be reconstructed in space and time with the use of the [[Traffic congestion: Reconstruction with Kerner's three-phase theory|ASDA and FOTO]] models.

[[File:Speed-flow horseshoe diagram traffic congestion.svg|thumb|300px|right|Speed-flow diagram for a highway, scales omitted. When the volume of vehicles per hour reaches 75%-100% of the road capacity, traffic flow shifts from free-flowing (green) to congested (gray) and both volume and speeds are reduced. The red ellipse represents rush-hour traffic.<ref>{{citation|author=Asaf Hazut |date=April 2019 |contribution=Speed-volume curve for the [[Tel Aviv Savidor Central railway station|Arlozorov]]-[[Tel Aviv HaShalom railway station|Hashalom]] section of the [[Highway 20 (Israel)|Ayalon Highway]] on weekdays, May 2017 |title=Annual convention of the Israeli Society for Transportation Research |publisher=[[Hebrew University of Jerusalem]]}}</ref><ref>{{citation |url=https://cityobservatory.org/what-covid-19-teaches-us-about-how-to-fix-freeways/ |title= What Covid-19 teaches us about how to fix freeways |author=Joe Cortright |date=April 22, 2020 |website=City Observatory}}</ref><ref>{{citation |url=https://www.nzta.govt.nz/roads-and-rail/ramp-signals/sh1-northbound-at-green-lane-what-happens-here/ |title=SH1 Northbound at Green Lane – What happens here? |publisher=Waka Kotahi NZ Transport Agency |year=2016}}</ref>]]

[[File:Motorcycles on Civic Boulevard 20080918.jpg|thumb|Congestion on a street in [[Taipei]] consisting primarily of [[motorcycles]]]]
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 effect]]s"), such as an abrupt steering maneuver by a single motorist. Traffic scientists liken such a situation to the sudden freezing of [[supercooling|supercooled fluid]].<ref name="ball">''Critical Mass'' – [[Philip Ball|Ball, Philip]], {{ISBN|0-09-945786-5}}</ref>

Because of the poor correlation of theoretical models to actual observed traffic flows, transportation planners and highway engineers attempt to [[traffic flow|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 randomizing 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.<ref>{{cite web|url=https://www.sciencedaily.com/releases/2009/06/090608151550.htm|title=Mathematicians Take Aim At 'Phantom' Traffic Jams|work=ScienceDaily|access-date=October 5, 2014|archive-date=July 23, 2018|archive-url=https://web.archive.org/web/20180723163613/https://www.sciencedaily.com/releases/2009/06/090608151550.htm|url-status=live}}</ref>

==Negative impacts==
{{Original research|section|date=January 2017}}
[[File:Traffic jam on bole rode Addis Abeba.jpg|thumb|A traffic jam on Bole Road in [[Addis Ababa]]]]
Traffic congestion has a number of negative effects:
* Wasting time of motorists and passengers ("[[opportunity cost]]"). 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]] and [[greenhouse gas|carbon dioxide emissions]] 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]] 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]] from congested main arteries to secondary roads and side streets as alternative routes are attempted ('[[rat running]]'), which may affect neighborhood [[amenity]] and [[real estate]] prices.
* Higher chance of collisions due to tight spacing and constant stopping-and-going.

===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]].[[File:Female Street Sellers Accra 12.jpg|thumb|An example of the traffic situation in Accra, Ghana, increasing carbon emission in the air|257x257px]]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.<ref>{{cite web|url=http://www.phrases.org.uk/meanings/303700.html|title="Road rage" meaning and origin, Phrases.org.uk|access-date=October 5, 2014|archive-date=June 21, 2009|archive-url=https://web.archive.org/web/20090621083855/http://www.phrases.org.uk/meanings/303700.html|url-status=dead}}</ref>

=== Economic loss ===
[[File:Costs of Congestion and Parking Search.png|thumb|300px|Costs of congestion and parking search]]{{Expand section|date=December 2019}}
{| class="wikitable"
|+
!Area
!Loss in billions
!Note
|-
|[[United States|US]]
|$305 <ref>{{Cite news|url=https://www.smartcitiesdive.com/news/gridlock-woes-traffic-congestion-by-the-numbers/519959/|title=Gridlock woes: Traffic congestion by the numbers|work=Smart Cities Dive|access-date=March 28, 2018|language=en-US|archive-date=March 28, 2018|archive-url=https://web.archive.org/web/20180328170147/https://www.smartcitiesdive.com/news/gridlock-woes-traffic-congestion-by-the-numbers/519959/|url-status=live}}</ref>
|<ref>{{cite news |last=Rahim |first=Zamira |title=Here's How Much Sitting In Traffic Is Costing You |language=en |website=Money.com |url=https://money.com/traffic-los-angeles-driving/ |url-status=live |access-date=March 28, 2018 |archive-url=https://web.archive.org/web/20200824191107/https://money.com/traffic-los-angeles-driving/ |archive-date=August 24, 2020}}</ref>
|-
|[[United Kingdom|UK]]
|$52.01 
|<ref>{{cite web|url=http://newburghgazette.com/2018/02/06/congestion-costs-united-kingdom-almost-40bn-a-year-report/|title=Home|website=newburghgazette.com|language=en|access-date=March 28, 2018|archive-date=March 28, 2018|archive-url=https://web.archive.org/web/20180328231050/http://newburghgazette.com/2018/02/06/congestion-costs-united-kingdom-almost-40bn-a-year-report/|url-status=live}}</ref>
|-
|[[New York City|NYC]]
|$33.7
|
|-
|[[Los Angeles|LA]]
|$19.2
|<ref>{{Cite news|url=http://mentalfloss.com/article/530705/heres-how-much-traffic-congestion-costs-worlds-biggest-cities|title=Here's How Much Traffic Congestion Costs the World's Biggest Cities|date=February 11, 2018|access-date=March 28, 2018|language=en|archive-date=March 28, 2018|archive-url=https://web.archive.org/web/20180328164742/http://mentalfloss.com/article/530705/heres-how-much-traffic-congestion-costs-worlds-biggest-cities|url-status=live}}</ref>
|-
|[[Metro Manila|Manila]]
|$18.615 
|<ref>{{Cite news|url=https://www.imoney.ph/articles/the-cost-of-traffic-in-metro-manila/|title=Find Out What's The Cost of Traffic In Metro Manila |last=Isla|first=Rouselle|date=May 26, 2016|work=iMoney.ph|access-date=March 28, 2018 |language=en-US|archive-date=March 28, 2018|archive-url=https://web.archive.org/web/20180328164843/https://www.imoney.ph/articles/the-cost-of-traffic-in-metro-manila/|url-status=live}}</ref>
|-
|[[Bangladesh]]
|$11.4
|<ref>{{Cite news|url=https://www.thedailystar.net/opinion/society/traffic-jam-the-ugly-side-dhakas-development-1575355?amp|title=Traffic jam: The ugly side of Dhaka's development|date=May 13, 2018|work=The Daily Star|access-date=May 14, 2018|language=en|archive-date=May 15, 2018|archive-url=https://web.archive.org/web/20180515183626/https://www.thedailystar.net/opinion/society/traffic-jam-the-ugly-side-dhakas-development-1575355?amp|url-status=live}}</ref>
|-
|[[San Francisco|SF]]
|$10.6
|
|-
|[[Atlanta]]
|$7.1 
|
|-
|[[Jakarta]]
|$5
|<ref>{{Cite news|url=http://www.thejakartapost.com/news/2017/10/06/jakarta-foots-us5b-annual-bill-for-traffic-jams-minister.html|title=Jakarta foots US$5b annual bill for traffic jams: Minister|work=The Jakarta Post|access-date=March 28, 2018|language=en|archive-date=March 28, 2018|archive-url=https://web.archive.org/web/20180328165501/http://www.thejakartapost.com/news/2017/10/06/jakarta-foots-us5b-annual-bill-for-traffic-jams-minister.html|url-status=live}}</ref>
|-
|[[Dhaka]]
|$4.463
|<ref>{{Cite news|url=http://www.thedailystar.net/frontpage/colossal-loss-1553002|title=Colossal loss|date=March 25, 2018|work=The Daily Star|access-date=March 28, 2018|language=en|archive-date=March 27, 2018|archive-url=https://web.archive.org/web/20180327140846/http://www.thedailystar.net/frontpage/colossal-loss-1553002|url-status=live}}</ref>
|-
|[[Greater Toronto and Hamilton Area|GTHA]]
|$3.3
|<ref>{{cite web|url=http://www.metrolinx.com/en/regionalplanning/costsofcongestion/costs_congestion.aspx|title=Costs of Congestion|website=www.metrolinx.com|language=en|access-date=March 28, 2018|archive-date=March 28, 2018|archive-url=https://web.archive.org/web/20180328231027/http://www.metrolinx.com/en/regionalplanning/costsofcongestion/costs_congestion.aspx|url-status=live}}</ref>
|}

==Positive effects==
[[File:Silverdale Rd. - geograph.org.uk - 1047019.jpg|thumb|Houses in this street in [[Royal Tunbridge Wells]] were built when cars were few. With no provision for garages or off-street parking, on-street parking has formed a choke point likely to cause traffic congestion.]]
[[File:Tráfico en Madrid. Noviembre de 2017.jpg|thumb|A traffic jam in [[Madrid]]]]
Congestion has the benefit of encouraging motorists to retime their trips so that expensive road space is in full use for more hours per day. It may also encourage travellers to pick alternate modes with a lower environmental impact, such as public transport or bicycles.<ref>{{cite web|url=http://www.aptnsw.org.au/blunden83.html|title=Congestion - Friend or Foe? - W R Blunden 1983|access-date=October 5, 2014|archive-date=March 9, 2015|archive-url=https://web.archive.org/web/20150309160401/http://aptnsw.org.au/blunden83.html|url-status=live}}</ref>

It has been argued that traffic congestion, by reducing road speeds in cities, could reduce the frequency and severity of road crashes.<ref>{{cite web |url=http://www.ipart.nsw.gov.au/files/13687885-53fa-40c8-b33d-a246010695c4/Draft_Report__Maximum_fares_for_metropolitan_and_outer_metropolitan_buses_from_January_2014.pdf |title=Maximum fares for metropolitan and outer metropolitan buses from January 2014 - Draft Report, p. 37, citing work by LECG "Value of Sydney bus externalities and optimal Government subsidy - Final report", September 2009, p. 17 |access-date=July 12, 2018 |archive-date=May 25, 2017 |archive-url=https://web.archive.org/web/20170525171209/https://www.ipart.nsw.gov.au/files/13687885-53fa-40c8-b33d-a246010695c4/Draft_Report__Maximum_fares_for_metropolitan_and_outer_metropolitan_buses_from_January_2014.pdf |url-status=live }}</ref> More recent research suggests that a U-shaped curve exists between the number of accidents and the flow of traffic, implying that more accidents happen not only at high congestion levels, but also when there are very few vehicles on the road.<ref name="Kumar">{{cite journal  | last1 = Kumar  | first1 = Nishant  | last2 = Raubal | first2 = Martin | title = Applications of deep learning in congestion detection, prediction and alleviation: A survey  | journal = Transportation Research Part C: Emerging Technologies  | volume = 133  | pages = 103432  | year = 2021 | doi = 10.1016/j.trc.2021.103432  | hdl = 10230/42143  | s2cid = 240420107 | doi-access = free  | arxiv = 2102.09759 | bibcode = 2021TRPC..13303432K | hdl-access = free  }}</ref>

==Countermeasures==
{{Further|Mobility transition}}

===Improving road infrastructure===
[[File:Grnfld Ramp.jpg|thumb|Metered ramp on [[Interstate 894|I-894]] in [[Milwaukee, Wisconsin]], U.S. The queue of cars waiting at the red light can be seen on the upper portion of the picture.]]
[[File:A38(M) Aston Expressway.jpg|thumb|The [[A38(M) motorway|A38M Aston Expressway]] in [[Aston]], towards central [[Birmingham]] - the lanes are controlled via the overhead gantries, which reverse the flow of one lane (making 4 in one direction, 2 in the other and a central buffer lane) during peak times accordingly.]]
[[File:404HOV lane.png|thumb|upright|The HOV lanes in [[Highway 404]] in [[Southern Ontario]] are separated by a stripped buffer zone that breaks occasionally to allow vehicles to enter and exit the HOV lane.]]

* Increasing road capacity is standard response to congestion, perhaps by widening an existing road or adding a new road, bridge or tunnel. However, this has been shown to result in attracting more traffic, otherwise known as [[induced demand]]. The result can be greater congestion on the expanded artery itself or on auxiliary roads.<ref name="Schneider 2018">{{cite web |last1=Schneider |first1=Benjamin |title=CityLab University: Induced Demand |website=[[Bloomberg News]] |url=https://www.bloomberg.com/news/articles/2018-09-06/traffic-jam-blame-induced-demand |access-date=January 18, 2022 |date=September 6, 2018}}</ref> In a similar vein, [[Braess's paradox]] shows that adding road capacity might make congestion worse, even if demand does not increase. In his paper, "The Law of Peak Hour Express Way Congestion", published in 1962, Anthony Downs formulated this phenomenon as a "law": "on urban commuter expressways, peak-hour traffic congestion rises to meet maximum capacity."{{sfn |Downs |1962 |p=393}}
* [[Junction (road)|Junction]] improvements
** [[Grade separation]], using bridges (or, less often, tunnels) freeing movements from having to stop for other crossing movements
** [[Ramp meter|Ramp signaling]], 'drip-feeding' merging traffic via [[traffic signal]]s onto a congested motorway-type roadway
** Reducing junctions
*** [[Local-express lanes]], providing through lanes that bypass junction on-ramp and off-ramp zones
*** [[Limited-access road]], roads that limit the type and amounts of [[driveway]]s along their lengths
* [[Reversible lane]]s, where certain sections of highway operate in the opposite direction on different times of the day(s) of the week, to match asymmetric demand. These pose a potential for collisions, if drivers do not notice the change in direction indicators. This may be controlled by [[variable-message sign]]s 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 [[Bus rapid transit|busway system]]
** [[High-occupancy toll lane|Express toll lanes]]
** [[High-occupancy vehicle lane|HOV lanes]], for vehicles with at least three (sometimes at least two) riders, intended to encourage [[carpool]]ing
*** [[Slugging]], impromptu carpooling at HOV access points, on a [[hitchhiking]] or payment basis
*** [[Market economy|Market-based]] carpooling with pre-negotiated financial incentives for the driver

===Urban planning and design===
[[Urban planning|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.
* [[Grid plan]]s including [[Fused Grid|fused grid]] road network geometry, rather than tree-like [[network topology]] which branches into [[cul-de-sac]]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]]s and allows more trips to be made without a car.
* Zoning laws that encourage [[mixed-use development]], which reduces distances between residential, commercial, retail, and recreational destinations and encourage cycling and walking. Cycling [[modal share]] is strongly associated with the availability of local [[cycling infrastructure]].<ref name="Mueller">{{cite journal  | last = Mueller  | first = N  | title = Health impact assessment of cycling network expansions in European cities.  | journal = Preventive Medicine  | volume = 109  | pages = 62–70  | year = 2018  | pmid = 29330030  | doi = 10.1016/j.ypmed.2017.12.011  | url = http://repositori.upf.edu/bitstream/10230/42143/1/Mueller_pm_heal.pdf  | hdl = 10230/42143  | s2cid = 3774985 | archive-date = March 30, 2021  | archive-url = https://web.archive.org/web/20210330012535/http://repositori.upf.edu/bitstream/handle/10230/42143/Mueller_pm_heal.pdf;jsessionid=D3FA607F020DED5CD545603856BC37E5?sequence=1  | url-status = live  | hdl-access = free  }}</ref>
* [[Carfree city|Carfree cities]], car-light cities, and eco-cities designed to eliminate the need to travel by car for most inhabitants.<ref>{{Cite web |url=https://www.theguardian.com/business/2005/nov/06/china.theobserver |title=British to help China build 'eco-cities' |archive-url=https://web.archive.org/web/20160414042203/http://www.theguardian.com/business/2005/nov/06/china.theobserver |archive-date=April 14, 2016  |work=[[The Observer]] |date=November 6, 2005}}</ref><ref>{{cite magazine|url=https://www.wired.com/wired/archive/15.05/feat_popup.html|title=''Wired'', Pop-Up Cities: China Builds a Bright Green Metropolis, 04.24.07|magazine=Wired|access-date=October 5, 2014|date=April 24, 2007|last1=McGray|first1=Douglas|archive-date=March 25, 2010|archive-url=https://web.archive.org/web/20100325182000/http://www.wired.com/wired/archive/15.05/feat_popup.html|url-status=live}}</ref>
* [[Transit-oriented development]] are residential and commercial areas designed to maximize access to public transport by providing a transit station or stop ([[train station]], [[metro station]], [[tram stop]], or [[bus stop]]).

===Supply and demand===
{{See also|Transportation demand management}}
[[File:Autoroute M25.jpg|thumb|Widening works under way on the [[M25 motorway]] surrounding [[London, England]] to increase the number of lanes]]
[[File:Noratrun.jpg|thumb|right|During [[rush hour]], right turns onto the side street shown here are prohibited in order to prevent [[rat running]].]]
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 [[induced demand|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.<ref>{{Cite web |url=http://www.janeholtzkay.com/Articles/cleancar.html |title=Dreaming of a Clean Car? |archive-url=https://web.archive.org/web/20080518004530/http://www.janeholtzkay.com/Articles/cleancar.html |archive-date=May 18, 2008 |author-link=Jane Holtz Kay|last=Kay |first=Jane Holtz}}</ref><ref>{{Cite web |url=http://naioptb.org/news/2005mayors.asp |title=2005 Mayors Luncheon |archive-url=https://web.archive.org/web/20070927223155/http://naioptb.org/news/2005mayors.asp |archive-date=September 27, 2007 |work=the NAIOP website, [[Tampa Bay]], United States}}</ref> 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.{{citation needed|date=October 2017}}

Increased supply can include:
* Adding more capacity at bottlenecks (such as by adding more lanes at the expense of [[hard shoulder]]s 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|Parking 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.<ref>{{Cite journal | author = Hermann Knoflacher | year = 2006 | title = A new way to organize parking: the key to a successful sustainable transport system for the future | journal = Environment and Urbanization | volume = 18 | issue = 2 | pages = 387–400 | doi = 10.1177/0956247806069621 | bibcode = 2006EnUrb..18..387K | s2cid = 153752634 | author-link = Hermann Knoflacher| doi-access = free }}
</ref> Most transport planning experts agree that [[free parking]] distorts the market in favor of car travel, exacerbating congestion.<ref>
{{Cite book |last= Shoup |first= Donald C. |author-link = Donald Shoup|title= The High Cost of Free Parking |year=2005|publisher=American Planning Association |isbn=978-1-884829-98-7}}
</ref><ref>{{Cite book| last= Knoflacher| first= Hermann| author-link= Hermann Knoflacher| title= Stehzeuge. Der Stau ist kein Verkehrsproblem.| orig-year= 2001| publisher= Böhlau| location= Vienna| language= de| isbn= 978-3-205-98988-2| date=January 2001}}</ref>
* [[Park and ride]] facilities allowing parking at a distance and allowing continuation by [[public transport]] or [[car pool|ride sharing]]. Park-and-ride [[car park]]s are commonly found at [[metro station]]s, freeway entrances in suburban areas, and at the edge of smaller cities.
* Reduction of road capacity to force traffic onto other [[modal share|travel modes]]. Methods include [[traffic calming]] and the [[shared space]] concept.
* [[Road pricing]], 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.<ref>
{{Cite journal
 | last = Goddard
 | first = Haynes
 |date=July 1997
 | title =  Using Tradeable Permits to Achieve Sustainability in the World's Large Cities
 | journal = Environmental and Resource Economics
 | volume = 10
 | issue = 1
 | pages = 63–99
 | doi = 10.1023/A:1026444113237
 | s2cid = 154186781
 }}
</ref> A limited quota of car licenses are issued each year and traded in a [[free market]] fashion. This guarantees that the number of cars does not exceed road capacity while avoiding the negative effects of [[economic shortage|shortages]] 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]] scheme.<ref name="toh">{{Cite web |url=http://www.findarticles.com/p/articles/mi_m1038/is_n2_v37/ai_15419789 |title=The high cost of motoring in Singapore |last=Toh |first=Rex S. |work=Business Horizons |date=March–April 1994 |access-date=October 2, 2017 |archive-date=October 17, 2015 |archive-url=https://web.archive.org/web/20151017130544/http://www.findarticles.com/p/articles/mi_m1038/is_n2_v37/ai_15419789 |url-status=dead }}</ref>
** [[Congestion pricing]], including:
*** Congestion zone charges, in which entry via car to a certain area, such as the inner part of a city, requires payment. Enforcement may be a physical boundary (e.g., toll stations) or it may be virtual, via spot checks or cameras. Major examples include [[congestion pricing in New York City]]; [[Singapore]]'s [[electronic road pricing]]; the [[London congestion charge]]; and the [[Stockholm congestion tax]].
*** Fixed (the same at all times of day), variable (higher at peak times), or dynamic (higher during actual congestion) [[toll road]]s, [[toll bridge]]s, [[toll tunnel]]s, and toll lanes
* [[Managed lane]]s
** [[High-occupancy toll lane]]s
** [[Reversible lane]]s
** [[High-occupancy vehicle lane]]s
** [[Bus lane]]s
** [[Truck lane restriction]]s and [[climbing lane]]s, to allow faster vehicles to move unimpeded
** Allowing driving on highway shoulders at peak times
* [[Road space rationing]], where regulatory restrictions prevent certain types of vehicles from driving under certain circumstances or in certain areas.
** [[Vehicle registration plate|Number plate]] restrictions based on days of the week, as practiced in several large cities in the world, such as [[Athens]],<ref>
{{cite web|url=http://www.leda.ils.nrw.de/database/measures/meas0205.htm|title=LEDA Measure: License plate based traffic restrictions, Athens, Greece|publisher=LEDA database|access-date=April 9, 2008|url-status=dead|archive-url=https://web.archive.org/web/20080227030125/http://www.leda.ils.nrw.de/database/measures/meas0205.htm|archive-date=February 27, 2008}}
</ref> [[Mexico City]], [[Manila]], and São Paulo.<ref name=konsult>{{cite web |url         = http://www.elseviersocialsciences.com/transport/konsult/private/level2/instruments/instrument009/l2_009a.htm |title       = Regulatory restrictions |work        = KonSULT, the Knowledgebase on Sustainable Urban Land use and Transport |publisher   = Institute for Transport Studies, University of Leeds |url-status     = dead |archive-url  = https://web.archive.org/web/20040825080318/http://www.elseviersocialsciences.com/transport/konsult/private/level2/instruments/instrument009/l2_009a.htm |archive-date = August 25, 2004
}}
</ref> 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]], 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.{{Citation needed|date=September 2007}}
** [[License|Permits]], 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.<ref name=konsult/> For example, [[Bertrand Delanoë]], 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.<ref>{{Cite news | first = Jon | last = Henley | title = Paris drive to cut traffic in centre by 75% | url = https://www.theguardian.com/world/2005/mar/15/france.jonhenley | work = [[The Guardian]] | location = London | date = March 15, 2005 | archive-date = September 18, 2014 | archive-url = https://web.archive.org/web/20140918025826/http://www.theguardian.com/world/2005/mar/15/france.jonhenley | url-status = live }}</ref>
[[File:TrafficJamBikeLane.jpg|thumb|Bike lane constructed in areas of low space to encourage use of human-sized transportation]]
* [[Policy]] 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]], increasing modal shares. This can be achieved through infrastructure investment, subsidies, transport [[Intermodal passenger transport|integration]], pricing strategies that decrease the [[marginal cost]]/[[fixed cost]] ratios,<ref name=simon>
{{Cite journal  | first = Hermann  | last = Simon |author2=Robert J Dolan  | title = Price Customization  | publisher = American Marketing Association  | journal = Marketing Management  | volume = 7  | issue = 3}}</ref><ref name=link>{{Cite journal  | first = Heike  | last = Link  | title =  PEP-A Yield-Management Scheme for Rail Passenger Fares in Germany  | journal = Japan Railway & Transport Review  | volume = 38  |date=March 2004  | page = 54}}</ref> improved [[Public transport timetable|timetabling]] and greater priority for buses to reduce journey time e.g. [[bus lanes]] or [[bus rapid transit]] .<ref>{{Cite journal| last = Andersen | first = Bjørn |date=January 1993 | title = A survey of the Swiss public transport system and policy | journal = Transport Reviews | volume = 13 | issue = 1 | pages = 61–81 | doi = 10.1080/01441649308716835 }}
</ref><ref>{{cite web|url= http://eprints.whiterose.ac.uk/2058/|title= The philosophy and practice of Taktfahrplan: a case-study of the East Coast Main Line| first= Adrian | last=May|date= March 16, 2007|format= Working Paper|work= Working Paper 579|publisher= Institute of Transport Studies, University of Leeds, Leeds, UK|archive-date= December 10, 2007|archive-url= https://web.archive.org/web/20071210001239/http://eprints.whiterose.ac.uk/2058/|url-status= live}}</ref>
** [[Utility cycling|Cycling]] promotion through legislation, cycle facilities, subsidies, and awareness campaigns.<ref>{{Cite journal | last1 = Ogilvie | first1 = David | first2=Matt | last2=Egan |author3=Val Hamilton |author4=Mark Petticrew  | date = September 22, 2004 | title = Promoting walking and cycling as an alternative to using cars: systematic review | journal = [[British Medical Journal]] | volume = 329 | issue = 7469 | page = 763 | doi = 10.1136/bmj.38216.714560.55 | pmid = 15385407 | pmc = 520994 }}
</ref> [[Cycling in the Netherlands|The Netherlands has been pursuing cycle friendly policies]] for decades, and around a quarter of their commuting is done by bicycle.<ref>{{Cite journal | last1 = Rietveld | first1 = Piet | first2=Vanessa | last2=Daniel  |date=August 2004 | title = Determinants of bicycle use: do municipal policies matter? | journal = Transportation Research Part A: Policy and Practice | volume = 38| issue = 7 | pages = 531–550 | doi = 10.1016/j.tra.2004.05.003 | author-link = Piet Rietveld | doi-access = free | bibcode = 2004TRPA...38..531R }}</ref><ref>{{cite web |url=http://www.fietsberaad.nl/library/repository/bestanden/Cycling%20in%20the%20Netherlands%20VenW.pdf |title= Cycling in the Netherlands |publisher    = [[Rijkswaterstaat]] (Dutch Ministry of Transport, Public Works and Water Management) |archive-url=https://web.archive.org/web/20080528100652/http://www.fietsberaad.nl/library/repository/bestanden/Cycling%20in%20the%20Netherlands%20VenW.pdf |archive-date = May 28, 2008 |url-status     = dead}}</ref>
** Promotion of more flexible work place practices. For example, a flexible workplaces pilot was undertaken in Brisbane, Australia during 2009 to test the applicability of a voluntary travel behavior change program to achieve transport system outcomes, particularly as they related to managing congestion, either through mode shift or peak spreading. During the one-month Pilot, amongst almost 900 Brisbane CBD workers across 20 private and public sector organizations, shifts of more than 30% out of the morning and afternoon peak travel was recorded.<ref>Marinelli, P. A. Cleary, N. Worthington Eyre, H. and Doonan, K. 2010. Flexible Workplaces: Achieving the worker's paradise and transport planner's dream in Brisbane, Proceedings of the 33rd Australasian Transport Research Forum, September 29-October 1, 2010, Canberra.</ref>
** [[Remote work]] encouraged through legislation and subsidies.<ref>{{cite web |url=http://www.discovery.org/scripts/viewDB/index.php?command=view&program=DI%20Main%20Page%20-%20News&id=4235 |title=Slow But Steady "Telework Revolution" Eyed |author=Matt Rosenberg|publisher=Cascadia Prospectus|date=September 26, 2007|access-date=October 7, 2007|archive-date=October 27, 2007|archive-url=https://web.archive.org/web/20071027153140/http://www.discovery.org/scripts/viewDB/index.php?command=view&program=DI%20Main%20Page%20-%20News&id=4235|url-status=live}}</ref>
** [[Online shopping]] promotion,<ref name=rac2050>
{{cite web
 | title = Motoring Towards 2050 – Roads and Reality
 | url = http://www.racfoundation.org/index.php?option=com_content&task=view&id=535&Itemid=31
 | publisher = [[RAC foundation]]
 | url-status = dead
 | archive-url = https://web.archive.org/web/20090120175029/http://www.racfoundation.org/index.php?option=com_content&task=view&id=535&Itemid=31
 | archive-date = January 20, 2009
 }}
</ref><ref name=dft>{{cite web
 | title = Smarter Choices – Changing the way we travel
 | date = June 24, 2005
 | url = http://www.dft.gov.uk/pgr/sustainable/smarterchoices/ctwwt/
 | publisher = [[Department for Transport]]
 | access-date = April 21, 2008
 | archive-date = April 8, 2008
 | archive-url = https://web.archive.org/web/20080408055546/http://www.dft.gov.uk/pgr/sustainable/smarterchoices/ctwwt/
 | url-status = live
 }}</ref> potentially with [[Packstation|automated delivery booths]] helping to solve the [[Last mile (transportation)|last mile problem]] and reduce shopping trips made by car.{{citation needed|date=April 2021}}

===Traffic management===
[[File:SES Staumelder A5.JPG|thumb|Traffic congestion detector in Germany]]
Use of so-called [[intelligent transportation system]]s, which guide traffic:
* [[Traffic reporting]], via radio, [[Global Positioning System|GPS]] and [[Car App|mobile apps]], to advise road users
* [[Variable message sign]]s installed along the roadway, to advise road users<ref>{{cite web|url=http://sior.ub.edu/jspui/cris/socialimpact/socialimpact00438|title=Reducing delay due to traffic congestion|website=Social Impact Open Repository|access-date=September 5, 2017|archive-date=September 5, 2017|archive-url=https://web.archive.org/web/20170905144020/http://sior.ub.edu/jspui/cris/socialimpact/socialimpact00438|url-status=live}}</ref>
* [[Automotive navigation system|Navigation systems]], possibly linked up to automatic traffic reporting
* [[Traffic counter]]s permanently installed, to provide real-time traffic counts
* [[Automated highway system]]s, 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{{Citation needed|date=September 2007}}
* [[Parking guidance and information]] systems providing dynamic advice to motorists about free parking
* [[Active traffic management]]<ref name="ha6months">{{cite web|url=http://www.dft.gov.uk/pgr/roads/tpm/m42activetrafficmanagement/ATM6MonthSummaryResultsforP1.pdf  |archive-url=http://webarchive.nationalarchives.gov.uk/20080306113842/http://www.dft.gov.uk/pgr/roads/tpm/m42activetrafficmanagement/ATM6MonthSummaryResultsforP1.pdf  |url-status=dead  |archive-date=March 6, 2008  |publisher=Department for Transport |author=Highways Agency |title=M42 Active Traffic Management Results – First Six Months |date=October 25, 2007|access-date=December 31, 2007}}</ref> 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===
[[File:Road Space Requirements.png|thumb|Different modes of transport require different amounts of road space.]]
* [[School]] opening times arranged to avoid rush hour traffic (in some countries, private car school pickup and drop-off traffic are substantial percentages of peak hour traffic).{{Citation needed|date=April 2008}}
* Considerate driving behavior promotion and enforcement. Driving practices such as [[tailgating]], frequent lane changes, and impeding the flow of traffic 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 barriers to prevent drivers from slowing down out of curiosity (often called "[[rubbernecking]]" in the United States). This often includes crashes, 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]] reductions, as practiced on the [[M25 motorway]] 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 (time)|interval]] between cars is reduced, not the distance itself. Low intervals are generally only safe at low speeds.
* [[Lane splitting|Lane splitting/filtering]], in which some jurisdictions allow [[motorcycle]]s, [[scooter (motorcycle)|scooters]] and bicycles to travel in the space between cars, buses, and trucks.<ref>{{Cite journal | title=Glossary | url=http://www.nhtsa.dot.gov/people/injury/pedbimot/motorcycle/00-NHT-212-motorcycle/glossary71-72.html | journal=National Agenda for Motorcycle Safety | publisher=[[US Department of Transportation]] [[National Highway Traffic Safety Administration]]/[[Motorcycle Safety Foundation]] | access-date=September 18, 2010 | archive-date=April 6, 2010 | archive-url=https://web.archive.org/web/20100406110515/http://www.nhtsa.dot.gov/PEOPLE/injury/pedbimot/motorcycle/00-NHT-212-motorcycle/glossary71-72.html | url-status=live }}</ref><ref name="NHSTA">{{cite web |publisher=Motorcycle Glossary.com |title=Define:Lane Splitting |url=http://motorcycle-glossary.com/lane-splitting/150 |access-date=January 6, 2009 |url-status=usurped |archive-url=https://web.archive.org/web/20090106054119/http://motorcycle-glossary.com/lane-splitting/150 |archive-date=January 6, 2009 }}</ref>
* Reduction of road freight avoiding problems such as double parking with innovative solutions including cargo bicycles and Gothenburg's Stadsleveransens.<ref>{{cite web|title=Gridlock and Traffic Congestion in Cities – Is This the Solution?|work=Go Supply Chain |date=April 19, 2017 |url=https://www.gosupplychain.com/blog/gridlock-and-traffic-congestion-in-cities.html|access-date=April 26, 2017|archive-date=April 27, 2017|archive-url=https://web.archive.org/web/20170427003737/https://www.gosupplychain.com/blog/gridlock-and-traffic-congestion-in-cities.html|url-status=live}}</ref>
* Reducing the quantity of cars that are on the road,<ref>{{Cite web |url=https://www.theguardian.com/environment/bike-blog/2019/jul/03/ten-common-myths-about-bike-lanes-and-why-theyre-wrong |title=Ten common myths about bike lanes – and why they're wrong |website=[[TheGuardian.com]] |date=July 3, 2019 |access-date=September 5, 2020 |archive-date=August 8, 2020 |archive-url=https://web.archive.org/web/20200808131140/https://www.theguardian.com/environment/bike-blog/2019/jul/03/ten-common-myths-about-bike-lanes-and-why-theyre-wrong |url-status=live }}</ref> i.e. through [[proof-of-parking]] requirements, [[circulation plan]]s, [[corporate car sharing]], [[Parallel parking#Legality|bans on on-street parking]] or by increasing the costs of [[car ownership]]

==By country==

===Australia===
{{externalvideo|video1=[https://www.youtube.com/watch?v=AnGdc-q5lX4 Traffic Jam Problem In Australia (1965)]}}
[[File:Warringah Freeway2.jpg|thumb|Traffic jam on the [[Warringah Freeway]] in [[Sydney]]]]
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.{{citation needed|date=October 2015}} Based on a survey in 2024, Brisbane is the most congested cities in Australia and 10th in the world, with drivers averagely losing 84 hours throughout the year.<ref>{{Cite web |last= |first= |date=2025-01-07 |title=2024 Traffic Rankings: The World's Most Congested Cities Revealed |url=https://ftnnews.com/travel-news/road-travel/2024-traffic-rankings-the-worlds-most-congested-cities-revealed/ |access-date=2025-01-10 |website=ftnnews |language=}}</ref>

===Bangladesh===
[[File:Kazi Nazrul Islam Ave Road, Dhaka. .jpg|thumb|Traffic jam in [[Dhaka]]]]
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;<ref>{{Cite web |url=http://www.ti-bangladesh.org/research/ES_Rajuk_Eng.pdf |title=Corruption in Plan Permission Process in RAJUK: A Study of Violations and Proposals |archive-url=https://web.archive.org/web/20120416155839/http://www.ti-bangladesh.org/research/ES_Rajuk_Eng.pdf |archive-date=April 16, 2012 |date=August 2007}}</ref> poorly maintained road surfaces, with potholes rapidly eroded further by frequent flooding and poor or non-existent drainage;<ref>{{cite web |url=http://www.thefinancialexpress-bd.com/more.php?date=2012-07-24&news_id=137724 |title=The Financial Express &#124; Financial Online Newspaper |publisher=Thefinancialexpress-bd.com |access-date=July 12, 2018 |archive-date=July 26, 2012 |archive-url=https://web.archive.org/web/20120726153114/http://www.thefinancialexpress-bd.com/more.php?news_id=137724&date=2012-07-24 |url-status=live }}</ref> haphazard stopping and parking;<ref>{{cite web|url=http://www.demotix.com/news/1354344/haphazard-parking-causes-more-traffic-jams-dhaka|title=Haphazard parking causes more traffic jams in Dhaka|work=Demotix|access-date=October 5, 2014|url-status=dead|archive-url=https://web.archive.org/web/20141006104324/http://www.demotix.com/news/1354344/haphazard-parking-causes-more-traffic-jams-dhaka|archive-date=October 6, 2014}}</ref> poor driving standards;<ref>{{Cite web |url=http://print.thefinancialexpress-bd.com/old/more.php?news_id=137914&date=2012-07-26 |title=Two important behaviour changes for road safety: Tolerance and patience |archive-url=https://web.archive.org/web/20170525171211/http://print.thefinancialexpress-bd.com/old/more.php?news_id=137914&date=2012-07-26 |archive-date=May 25, 2017 |first=Ridwan |last=Quaium |work=[[The Financial Express (Bangladesh)|The Financial Express]] |volume=20 |issue=207 REGD NO DA 1589 | date=July 26, 2012}}</ref> total lack of alternative routes, with several narrow and (nominally) one-way roads.<ref>{{cite web|title=Traffic Jam at Dhaka|url=https://teletalkbd.com/traffic-jam-paragraph|work=Teletalk Bangladesh|access-date=December 25, 2020|archive-date=January 29, 2021|archive-url=https://web.archive.org/web/20210129222351/https://teletalkbd.com/traffic-jam-paragraph/|url-status=live}}</ref><ref name="The Daily Star">{{Cite news|url=http://www.thedailystar.net/newDesign/news-details.php?nid=198466|title=Traffic jam|work=The Daily Star|date=August 14, 2011|access-date=May 5, 2012|author=Md. Mirazul Islam|archive-date=March 30, 2021|archive-url=https://web.archive.org/web/20210330012647/https://www.thedailystar.net/news-detail-198466|url-status=live}}</ref>

===Brazil===
[[File:Traffic jam Sao Paulo 09 2006 30.JPG|thumb|Typical traffic jam in [[São Paulo]] downtown, despite [[road space rationing]] by plate number. ''Rua da Consolação'', São Paulo, Brazil]]
According to ''[[Time (magazine)|Time]]'' magazine, [[São Paulo]] has the world's worst daily traffic jams.<ref name=Times_SP>{{Cite magazine|url=http://www.time.com/time/world/article/0,8599,1733872,00.html|title=The World's Worst Traffic Jams|magazine=Time|date=April 21, 2008|access-date=June 20, 2008|author=Andrew Downie|archive-date=August 26, 2013|archive-url=https://web.archive.org/web/20130826060457/http://www.time.com/time/world/article/0,8599,1733872,00.html|url-status=dead}}</ref> 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 {{Convert|344|km}} of cumulative queues around the city during the evening rush hour.<ref name=BRArecord2014>{{cite news|url=http://economia.uol.com.br/noticias/efe/2014/05/23/sao-paulo-sofre-engarrafamento-recorde-de-344-quilometros.htm|title=São Paulo sofre engarrafamento recorde de 344 quilômetros|language=pt|trans-title=São Paulo suffers record traffic jam of 344 kilometers|author=EFE|publisher=UOL Economia|date=May 23, 2014|access-date=May 25, 2014|archive-date=May 26, 2014|archive-url=https://web.archive.org/web/20140526011853/http://economia.uol.com.br/noticias/efe/2014/05/23/sao-paulo-sofre-engarrafamento-recorde-de-344-quilometros.htm|url-status=live}}</ref> The previous record occurred on November 14, 2013, with {{Convert|309|km}} of cumulative queues.<ref name=BRArecord2014/>

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.<ref>{{cite web |last1=Shankowsky |first1=Josh |title=Largest Traffic Jams in History |url=https://www.communitycouch.net/auto/what-have-been-the-biggest-traffic-jams-in-history/ |website=Community Couch |publisher=Snap SEO |access-date=February 15, 2021 |archive-date=March 30, 2021 |archive-url=https://web.archive.org/web/20210330012558/https://www.communitycouch.net/auto/what-have-been-the-biggest-traffic-jams-in-history/ |url-status=live }}</ref> The subway has only {{convert|61|km|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.<ref>{{Cite news|url=http://www1.folha.uol.com.br/folha/cotidiano/ult95u387928.shtml|title=Kassab restringe carga e descarga em SP e inclui caminhões no rodízio|date=April 1, 2008|publisher=Folha de S.Paulo Online|language=pt|access-date=June 20, 2008|archive-date=April 6, 2008|archive-url=https://web.archive.org/web/20080406063031/http://www1.folha.uol.com.br/folha/cotidiano/ult95u387928.shtml|url-status=live}}</ref><ref>{{Cite news|url=http://www.intelog.net/site/default.asp?TroncoID=907492&SecaoID=508074&SubsecaoID=948063&Template=../artigosnoticias/user_exibir.asp&ID=252171&Titulo=Kassab%20cria%20rod%EDzio%20para%20caminh%E3o%20no%20centro|title=Kassab cria rodízio para caminhão no centro|author=Folha de S.Paulo|date=June 18, 2008|publisher=INTELOG|language=pt|access-date=June 20, 2008|archive-date=December 7, 2008|archive-url=https://web.archive.org/web/20081207141159/http://www.intelog.net/site/default.asp?TroncoID=907492&SecaoID=508074&SubsecaoID=948063&Template=..%2Fartigosnoticias%2Fuser_exibir.asp&ID=252171&Titulo=Kassab%20cria%20rod%EDzio%20para%20caminh%E3o%20no%20centro|url-status=live}}</ref>

===Canada===
[[File:401 Gridlock.jpg|thumb|[[Ontario Highway 401|Highway 401]] in Ontario, which passes through Toronto, suffers chronic traffic congestion despite its width of up to 18 lanes.<ref>{{cite news|last=Kalinowski|first=Tess|title=GTA commuter crawl gets slower|url=https://www.thestar.com/news/gta/transportation/article/747348--gta-commuter-crawl-gets-slower|access-date=December 23, 2010|newspaper=Toronto Star|date=January 7, 2010|archive-date=January 10, 2010|archive-url=https://web.archive.org/web/20100110225015/http://www.thestar.com/news/gta/transportation/article/747348--gta-commuter-crawl-gets-slower|url-status=live}}</ref><ref>{{cite news|last=Kennedy|first=Brendan|title=GTA's worst routes: Highway 401|url=https://www.thestar.com/news/gta/transportation/article/747327--gta-s-worst-routes-highway-401|access-date=December 23, 2010|newspaper=Toronto Star|date=January 7, 2010|archive-date=February 6, 2012|archive-url=https://web.archive.org/web/20120206080940/http://www.thestar.com/news/gta/transportation/article/747327--gta-s-worst-routes-highway-401|url-status=live}}</ref>]]

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.<ref>{{cite news|title=Toronto commuting times worst of 19 major cities, study says|url=https://www.thestar.com/news/gta/transportation/article/787400--toronto-commuting-times-worst-of-19-major-cities-study-says|access-date=December 23, 2010|newspaper=Toronto Star|date=March 30, 2010|author=John Spears|author2=Tess Kalinowski|archive-date=May 2, 2010|archive-url=https://web.archive.org/web/20100502012034/http://www.thestar.com/news/gta/transportation/article/787400--toronto-commuting-times-worst-of-19-major-cities-study-says|url-status=live}}</ref>

===China===
[[File:Chang'an avenue in Beijing.jpg|thumb|Traffic jam in Beijing]]
The [[People's Republic of China|Chinese]] city of [[Beijing]] started a [[Road space rationing in Beijing|license plate rationing]] since the [[2008 Summer Olympics]] whereby each car is banned from the urban core one workday per week, depending on the last digit of its license plate. As of 2016, 11 major Chinese cities have implemented similar policies.<ref>{{cite news|url=https://www.economist.com/news/china/21700676-chinese-love-their-cars-do-not-want-pay-more-driving-them-great-crawl|title=The great crawl|newspaper=The Economist|access-date=January 7, 2018|archive-date=January 7, 2018|archive-url=https://web.archive.org/web/20180107232955/https://www.economist.com/news/china/21700676-chinese-love-their-cars-do-not-want-pay-more-driving-them-great-crawl|url-status=live}}</ref> Towards the end of 2010, Beijing announced a series of drastic measures to tackle the city's chronic traffic congestion, such as limiting the number of new plates issued to passenger cars to 20,000 a month, barring vehicles with non-Beijing plates from entering areas within the Fifth Ring Road during rush hours and expanding its [[Beijing Subway|subway system]].<ref>{{cite news|url=http://chinaautoweb.com/2010/12/to-tackle-traffic-jam-beijing-sets-new-car-plate-quota-limits-out-of-towners/|title=To Tackle Traffic Jam, Beijing Sets New Car Plate Quota, Limits Out-of-Towners|publisher=ChinaAutoWeb.com|access-date=January 13, 2011|archive-date=December 28, 2010|archive-url=https://web.archive.org/web/20101228031411/http://chinaautoweb.com/2010/12/to-tackle-traffic-jam-beijing-sets-new-car-plate-quota-limits-out-of-towners/|url-status=live}}</ref> The government aims to cap the number of locally registered cars in Beijing to below 6.3 million by the end of 2020.<ref>{{cite web|url=http://www.china.org.cn/china/2018-06/16/content_52358707.htm|title=Beijing takes aim at congestion, pollution with new car limits- China.org.cn|last=相镔|website=www.china.org.cn|access-date=June 22, 2018|archive-date=June 16, 2018|archive-url=https://web.archive.org/web/20180616063144/http://www.china.org.cn/china/2018-06/16/content_52358707.htm|url-status=live}}</ref> In addition, more than nine major Chinese cities including [[Shanghai]], [[Guangzhou]] and [[Hangzhou]] started limiting the number of new plates issued to passenger cars in an attempt to curb the growth of car ownership.<ref>{{Cite news|url=https://www.reuters.com/article/us-china-autos-regulations/chinas-nanjing-city-researches-license-plate-restriction-policy-idUSKCN1060FI|title=China's Nanjing city considers limiting issuance of car plates|date=July 26, 2016|work=Reuters|access-date=January 7, 2018|archive-date=January 8, 2018|archive-url=https://web.archive.org/web/20180108062439/https://www.reuters.com/article/us-china-autos-regulations/chinas-nanjing-city-researches-license-plate-restriction-policy-idUSKCN1060FI|url-status=live}}</ref><ref>{{cite web|url=http://www.wri.org/blog/2015/04/4-lessons-beijing-and-shanghai-show-how-china%E2%80%99s-cities-can-curb-car-congestion|title=4 Lessons from Beijing and Shanghai Show How China's Cities Can Curb Car Congestion {{!}} World Resources Institute|website=www.wri.org|language=en|access-date=January 20, 2018|date=April 10, 2015|archive-date=January 20, 2018|archive-url=https://web.archive.org/web/20180120235951/http://www.wri.org/blog/2015/04/4-lessons-beijing-and-shanghai-show-how-china%E2%80%99s-cities-can-curb-car-congestion|url-status=live}}</ref> In response to the increased demand to public transit caused by these policies, aggressive programs to [[Urban rail transit in China|rapidly expand]] public transport systems in many Chinese cities are currently underway.<ref>{{Cite news|url=https://www.thetransportpolitic.com/2018/01/17/in-response-to-growth-chinese-cities-choose-metros/|title=In response to growth, Chinese cities choose metros|date=January 17, 2018|work=The Transport Politic|access-date=January 20, 2018|language=en-US|archive-date=September 7, 2018|archive-url=https://web.archive.org/web/20180907234018/https://www.thetransportpolitic.com/2018/01/17/in-response-to-growth-chinese-cities-choose-metros/|url-status=live}}</ref>

A unique Chinese phenomenon of severe traffic congestion occurs during [[Chunyun|Chunyun Period]] or Spring Festival travel season.<ref>{{Cite news|url=http://www.cnn.com/travel/article/travel-china-chunyun/index.html|title=When all of China goes on vacation at once|date=January 13, 2017|work=CNN Travel|access-date=January 7, 2018|language=en|archive-date=January 8, 2018|archive-url=https://web.archive.org/web/20180108063735/http://www.cnn.com/travel/article/travel-china-chunyun/index.html|url-status=live}}</ref> It is a long-held tradition for most Chinese people to reunite with their families during [[Chinese New Year]]. People return to their hometown to have a [[reunion dinner]] with their families on [[Chinese New Year]]. It has been described as the largest annual human migration in the world.<ref>{{Cite news|url=http://news.bbc.co.uk/2/hi/asia-pacific/7813267.stm|title=China's holiday rush begins early|date=2009|access-date=January 7, 2018|language=en-GB|archive-date=January 19, 2018|archive-url=https://web.archive.org/web/20180119014400/http://news.bbc.co.uk/2/hi/asia-pacific/7813267.stm|url-status=live}}</ref><ref>{{Cite news|url=http://www.cnn.com/travel/article/china-spring-migration-chunyun/index.html|title=Earth's biggest human migration on a map|date=February 18, 2015|work=CNN Travel|access-date=January 7, 2018|language=en|archive-date=January 8, 2018|archive-url=https://web.archive.org/web/20180108120423/http://www.cnn.com/travel/article/china-spring-migration-chunyun/index.html|url-status=live}}</ref> Since the [[Economic reform in the People's Republic of China|economic boom]] and [[Urbanization in China|rapid urbanization]] of China since the late 1970s, many people work and study a considerable distance from their hometowns. Traffic flow is typically directional, with large amounts of the population working in more developed coastal provinces needing travel to their hometowns in the less developed interior. The process reverses near the end of Chunyun. With almost 3 billion trips<ref>{{cite web|url=http://www.ndrc.gov.cn/gzdt/201702/t20170222_838752.html|title=2017年春运发送旅客近30亿人次|access-date=January 7, 2018|archive-date=March 16, 2017|archive-url=https://web.archive.org/web/20170316025310/http://www.ndrc.gov.cn/gzdt/201702/t20170222_838752.html|url-status=live}}</ref> made in 40 days of the 2016 Chunyun Period, the Chinese intercity transportation network is extremely strained during this period.

The August 2010 [[China National Highway 110 traffic jam]] in [[Hebei]] province caught media attention for its severity, stretching more than {{convert|100|km}} from August 14 to 26, including at least 11 days of total [[gridlock]].<ref>{{Cite news|url=https://www.theguardian.com/technology/2010/aug/23/worlds-worst-traffic-jam|title=Welcome to the world's worst traffic jam|work=The Guardian|author=Leo Hickman|date=August 23, 2010|access-date=September 20, 2010|archive-date=October 17, 2015|archive-url=https://web.archive.org/web/20151017130545/http://www.theguardian.com/technology/2010/aug/23/worlds-worst-traffic-jam|url-status=live}}</ref><ref>{{Cite news|url=http://www.economist.com/node/16909167?story_id=16909167|title=The great crawl of China|publisher=The Economist|date=August 26, 2010|access-date=September 20, 2010|archive-date=October 22, 2010|archive-url=https://web.archive.org/web/20101022071755/http://www.economist.com/node/16909167?story_id=16909167|url-status=live}}</ref><ref name=NYT0810>{{Cite news|url=https://www.nytimes.com/2010/08/28/world/asia/28china.html|title=China's Growth Leads to Problems Down the Road|work=[[The New York Times]]|author=Michael Wines|date=August 27, 2010|access-date=September 20, 2010|archive-date=January 21, 2012|archive-url=https://web.archive.org/web/20120121175719/http://www.nytimes.com/2010/08/28/world/asia/28china.html?_r=1&scp=2&sq=straddling%20bus&st=cse|url-status=live}}</ref> 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."<ref name=NYT0810/><ref>{{Cite news|url=https://www.theguardian.com/world/2010/aug/24/china-60-mile-motorway-tailback|title=Gridlock is a way of life for Chinese|work=The Guardian|author=Jonathan Watts|date=August 24, 2010|access-date=September 20, 2010|archive-date=September 15, 2013|archive-url=https://web.archive.org/web/20130915193304/http://www.theguardian.com/world/2010/aug/24/china-60-mile-motorway-tailback|url-status=live}}</ref> The congestion is regarded as the worst in history by duration, and is one of the longest in length after the {{convert|175|km}} long Lyon-Paris traffic jam in France on February 16, 1980.

Recently, in Hangzhou [[City Brain]] has become active, reducing traffic congestion somewhat.<ref>{{Cite web |url=https://edition.cnn.com/2019/01/15/tech/alibaba-city-brain-hangzhou/index.html |title=Alibaba's 'City Brain' is slashing congestion in its hometown |date=January 15, 2019 |access-date=June 4, 2020 |archive-date=June 4, 2020 |archive-url=https://web.archive.org/web/20200604103927/https://edition.cnn.com/2019/01/15/tech/alibaba-city-brain-hangzhou/index.html |url-status=live }}</ref>

A 2021 study of subway constructions in China found that in the first year of a new subway line, road congestion declined.<ref>{{Cite journal|last1=Gu|first1=Yizhen|last2=Jiang|first2=Chang|last3=Zhang|first3=Junfu|last4=Zou|first4=Ben|date=2021|title=Subways and Road Congestion|url=https://www.aeaweb.org/articles?id=10.1257/app.20190024|journal=American Economic Journal: Applied Economics|language=en|volume=13|issue=2|pages=83–115|doi=10.1257/app.20190024|s2cid=233521120|issn=1945-7782|access-date=March 30, 2021|archive-date=March 30, 2021|archive-url=https://web.archive.org/web/20210330012559/https://www.aeaweb.org/articles?id=10.1257%2Fapp.20190024|url-status=live|url-access=subscription}}</ref>

===Greece===
[[File:OpenStreetMap Δακτύλιος 88432808.png|300px|thumb|Athens inner Daktylios limits]]
Since the 70s, the traffic on the streets of Athens has increased dramatically, with the existing road network unable to serve the ever-increasing demand. In addition, it has also caused an environmental burden, such as the [[Photochemical Smog|photochemical smog]]. To deal with it, the [[Daktylios]] has been enforced.

===India===
{{unreferenced section|date=June 2023}}
[[File:Ratan Lal Market, Kaseru Walan, Paharganj, New Delhi, Delhi, India - panoramio (1).jpg|thumb|Traffic jam in [[New Delhi]]]]
The number of vehicles in India is quickly increasing as a growing middle class can now afford to buy cars. India's road conditions have not kept up with the exponential growth in number of vehicles.

Various causes for this include:
* Private encroachments
* Non cooperation among drivers
* Unscientific road design
* Lack of free ways/exit ways where local roads and main roads intersect
* Lack of demarcated footpaths
* Lack of bus bays
* Lack of cycle tracks
* Lack of coordination among various government departments (e.g. digging of roads by telecom/water department and leaving it open)

===Indonesia===
[[File:BNN Temporary Transjakarta Stop at Rush Hour, 2023.jpg|thumb|Traffic congestion in [[Jakarta]], [[West Java]]]]
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]].<ref>{{cite news |last=Pantazi |first=Chloe |date=February 2, 2015 |title=The Worst Traffic In The World Is In... |url=https://www.thrillist.com/travel/nation/city-with-worst-traffic-jakarta-indonesia-tops-castrol-s-ranking-of-cities-with-most-stop-starts |newspaper=Thrillist |access-date=June 12, 2016 |archive-date=August 16, 2016 |archive-url=https://web.archive.org/web/20160816111355/https://www.thrillist.com/travel/nation/city-with-worst-traffic-jakarta-indonesia-tops-castrol-s-ranking-of-cities-with-most-stop-starts |url-status=live }}</ref>

Daily congestion in Jakarta is not a recent problem. The expansion of commercial area without [[road expansion]] shows worsening daily congestion even in main roads such as [[Jalan Jenderal Sudirman]], [[Jalan M.H. Thamrin]], and [[Jalan Gajah Mada and Jalan Hayam Wuruk|Jalan Gajah Mada]] in the mid-1970s.<ref>{{cite book |last=Merrillees |first=Scott |date=2015 |title=Jakarta: Portraits of a Capital 1950-1980 |url=https://books.google.com/books?id=akLWjgEACAAJ&q=JAKARTA:+Portraits+of+a+Capital+1950-1980 |location=Jakarta |publisher=Equinox Publishing |isbn=9786028397308 |pages=116–7 |access-date=October 29, 2020 |archive-date=March 30, 2021 |archive-url=https://web.archive.org/web/20210330012722/https://books.google.com/books?id=akLWjgEACAAJ&q=JAKARTA%3A+Portraits+of+a+Capital+1950-1980 |url-status=live }}</ref>

In 2016, 22 people died as a result of traffic congestion in Java. They were among those stuck in a three-day traffic jam at a [[Toll road|toll]] exit in [[Brebes Regency|Brebes]], [[Central Java]] called [[Brebes Exit]] or 'Brexit'. The traffic block stretched for 21&nbsp;km here and thousands of cars clogged the highway. Many people died because of carbon monoxide poisoning, fatigue or heat.<ref>{{cite news|title=Twelve people die in traffic jam in Indonesia at junction called 'Brexit'|url=https://www.theguardian.com/world/2016/jul/08/indonesia-traffic-jam-deaths-java-brebes-brexit-junction|agency=[[Agence France-Presse]]|date=July 8, 2016|newspaper=[[The Guardian (newspaper)|The Guardian]]|access-date=July 9, 2016|archive-date=July 9, 2016|archive-url=https://web.archive.org/web/20160709002700/https://www.theguardian.com/world/2016/jul/08/indonesia-traffic-jam-deaths-java-brebes-brexit-junction|url-status=live }}</ref>

===New Zealand===
[[File:Auckland traffic - copyright-free photo released to public domain.jpg|thumb|Busy traffic in [[Auckland]], 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 labeled worse than New York for traffic congestion with commuters sitting in traffic congestion for 95 hours per year),<ref name="GRIFF">{{Cite journal |url=http://www.griffith.edu.au/centre/urp/urp_publications/Issues_Papers/URP_IP5_MeesDodsonAucklandTransport_April2006.pdf |title=Backtracking Auckland: Bureaucratic rationality and public preferences in transport planning |archive-url=https://web.archive.org/web/20080413213710/http://www.griffith.edu.au/centre/urp/urp_publications/Issues_Papers/URP_IP5_MeesDodsonAucklandTransport_April2006.pdf |archive-date=April 13, 2008 |last1=Mees |first1=Paul |last2=Dodson |first2=Jago |journal=Urban Research Program Issues Paper 5 |publisher=[[Griffith University]] |date=April 2006}}</ref> and currently has one of the highest car-ownership rates per capita in the world, after the United States.<ref>{{Cite encyclopedia |url=http://www.teara.govt.nz/NewZealandInBrief/Society/8/en |title=Modern Society |archive-url=https://web.archive.org/web/20080324141426/http://www.teara.govt.nz/NewZealandInBrief/Society/8/en |archive-date=March 24, 2008 |encyclopedia=[[Te Ara: The Encyclopedia of New Zealand]] |access-date=April 25, 2008}}</ref> Traffic congestion in New Zealand is increasing with drivers on New Zealand's motorways reported to be struggling to exceed 20&nbsp;km/h on an average commute, sometimes crawling along at 8&nbsp;km/h for more than half an hour.

===Philippines===
[[File:Traffic along Commonwealth Avenue in Quezon City on July 5, 2022 (55339).jpg|thumb|Traffic along [[Commonwealth Avenue, Quezon City|Commonwealth Avenue]] in [[Quezon City]] on July 5, 2022]]
[[File:Heavy traffic sa EDSA-Tramo (Pasay)(2017-08-04).jpg|thumb|right|upright=0.9|Traffic jam at EDSA-Tramo in [[Pasay]], Metro Manila]]
{{Further|Traffic in Metro Manila}}
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]].<ref>{{cite news|last1=Tan|first1=Lara|title=Metro Manila has 'worst traffic on earth', longest commute - Waze|url=http://cnnphilippines.com/metro/2015/10/01/Metro-Manila-Philippines-worst-traffic-longest-commute-Waze-survey.html|access-date=January 17, 2016|agency=[[CNN Philippines]]|date=October 2, 2015|archive-date=January 23, 2016|archive-url=https://web.archive.org/web/20160123045043/http://cnnphilippines.com/metro/2015/10/01/Metro-Manila-Philippines-worst-traffic-longest-commute-Waze-survey.html|url-status=dead}}</ref> It is worsened by [[Traffic violation|violations of traffic laws]], like [[Parking violation|illegal parking]], loading and unloading, [[Red light running|beating the red light]], and [[wrong-way driving]].<ref>{{cite news|last1=Liquicia|first1=Chi|title=Manila traffic: the agony, without the ecstasy|url=http://www.latitudenews.com/story/manila-traffic-the-agony-without-the-ecstasy/|access-date=January 17, 2016|agency=Latitude News|archive-url=https://web.archive.org/web/20160208025450/http://www.latitudenews.com/story/manila-traffic-the-agony-without-the-ecstasy/|archive-date=February 8, 2016|url-status=dead}}</ref> Traffic congestion in Metro Manila is caused by the large number of registered vehicles, lack of roads, and [[Human overpopulation|overpopulation]], especially in the cities of [[Manila]] and [[Caloocan]], as well as the municipality of [[Pateros]].<ref name=faqph>{{cite web|title=10 Alarming Facts about Traffic in Metro Manila that You Should Know|url=http://faq.ph/facts-about-traffic-in-metro-manila-that-you-should-know/|website=FAQ.ph|access-date=January 17, 2016|archive-date=January 18, 2016|archive-url=https://web.archive.org/web/20160118122423/http://faq.ph/facts-about-traffic-in-metro-manila-that-you-should-know/|url-status=live}}</ref>

Traffic caused losses of ₱137,500,000,000 on the economy in 2011, and unbuilt roads and railway projects also causes worsening congestion.<ref>{{cite news|last1=Visconti|first1=Katherine|title=Traffic and infrastructure delays cost the Philippines|url=http://www.rappler.com/business/13137-traffic-and-infrastructure-delays-cost-the-philippines|access-date=January 17, 2016|agency=[[Rappler]]|date=September 26, 2012|archive-date=December 29, 2015|archive-url=https://web.archive.org/web/20151229154044/http://www.rappler.com/business/13137-traffic-and-infrastructure-delays-cost-the-philippines|url-status=live}}</ref> 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.<ref>{{cite news|last1=Dela Cruz|first1=Chrisee|title=DPWH chief Villar: Metro traffic jam 'can be solved in 2-3 years|url=http://www.rappler.com/business/211-governance/141731-mark-villar-metro-manila-traffic|access-date=August 7, 2016|agency=[[Rappler]]|date=August 2, 2016|archive-date=August 6, 2016|archive-url=https://web.archive.org/web/20160806071817/http://www.rappler.com/business/211-governance/141731-mark-villar-metro-manila-traffic|url-status=live}}</ref>

===Turkey===
[[File:Istanbul Otoyol 2 Richtung FSM 1.jpg|thumb|Traffic congestion in [[Istanbul]]]]
In recent years, the [[Istanbul Metropolitan Municipality]] has made huge investments on [[intelligent transportation system]]s and [[public transportation]]. Despite that, traffic is a significant problem in [[Istanbul]].
[[Istanbul]] has chosen the second most congested<ref>{{Cite web |url=http://www.tomtom.com/lib/doc/trafficindex/2013-1101%20TomTomTrafficIndex2013Q2EUR-km.pdf |title=TomTom European Traffic Index |access-date=February 5, 2014 |archive-url=https://web.archive.org/web/20131207030038/http://www.tomtom.com/lib/doc/trafficindex/2013-1101%20TomTomTrafficIndex2013Q2EUR-km.pdf |archive-date=December 7, 2013 |url-status=dead }}</ref> and the most sudden-stopping traffic in the world.<ref>{{cite web|url=http://www.sabah.com.tr/Gundem/2013/10/02/durkalkta-dunya-lideri-istanbul|title='Dur-kalk'ta dünya lideri İstanbul|date=October 2, 2013|work=sabah.com.tr|access-date=October 5, 2014|archive-date=October 6, 2014|archive-url=https://web.archive.org/web/20141006095135/http://www.sabah.com.tr/Gundem/2013/10/02/durkalkta-dunya-lideri-istanbul|url-status=live}}</ref> Travel times in Turkey's largest city take on average 55 percent longer than they should, even in relatively less busy hours.<ref>{{cite web|url=http://www.hurriyetdailynews.com/istanbul-drowning-in-traffic-chaos-report-announces.aspx?PageID=238&NID=44312&NewsCatID=341|title=Istanbul drowning in traffic chaos, report announces - LOCAL|date=April 5, 2013 |access-date=October 5, 2014|archive-date=October 6, 2014|archive-url=https://web.archive.org/web/20141006095436/http://www.hurriyetdailynews.com/istanbul-drowning-in-traffic-chaos-report-announces.aspx?PageID=238&NID=44312&NewsCatID=341|url-status=live}}</ref>

===United Kingdom===
[[File:Traffic Jam - geograph.org.uk - 391642.jpg|thumb|Congestion on [[A64 road]] heading towards to [[York]]]]
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:
<blockquote>
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.<ref name=tit>
{{Cite book| title = Traffic in Towns | date = 1963–1964 | publisher = [[Penguin Books]] in association with [[HMSO]] | at = Para 30 }}</ref>
</blockquote>
[[File:Railway bridge near Moira - geograph.org.uk - 307866.jpg|thumb|A solution to traffic congestion using [[Northern Ireland Railways]] from [[Moira railway station|Moira]] to [[Belfast Great Victoria Street railway station|Belfast Great Victoria Street]]]]

The Department for Transport sees growing congestion as one of the most serious transport problems facing the UK.<ref>
{{cite web
| title = Tackling congestion on our roads
| url = http://www.dft.gov.uk/pgr/roads/roadcongestion/
| publisher = Department for Transport
| url-status = dead
| archive-url = https://web.archive.org/web/20080423050200/http://www.dft.gov.uk/pgr/roads/roadcongestion/
| archive-date = April 23, 2008
}}</ref> On December 1, 2006, [[Rod Eddington]] published a UK government-sponsored [[Eddington Transport Study|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.<ref>
{{cite web
| title = Delivering choice and reliability
| url = http://www.dft.gov.uk/press/speechesstatements/speeches/congestion
| publisher = Department for Transport
| url-status = dead
| archive-url = https://web.archive.org/web/20081122094312/http://www.dft.gov.uk/press/speechesstatements/speeches/congestion
| archive-date = November 22, 2008
}}</ref> 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 totaling £28 bn a year.<ref>
{{cite web
 |title=The Eddington Transport Study 
 |author=Rod Eddington 
 |date=December 2006 
 |url=http://www.dft.gov.uk/about/strategy/transportstrategy/eddingtonstudy/ 
 |publisher=UK Treasury 
 |url-status=dead 
 |archive-url=https://web.archive.org/web/20080324002356/http://www.dft.gov.uk/about/strategy/transportstrategy/eddingtonstudy/ 
 |archive-date=March 24, 2008 
}}</ref>

A [[London congestion charge|congestion charge]] for driving in central London was introduced in 2003. In 2013, ten years later, [[Transport for London]] reported that the scheme resulted in a 10% reduction in traffic volumes from baseline conditions, and an overall reduction of 11% in vehicle kilometers in London. Despite these gains, traffic speeds in central London became progressively slower.

===United States===
[[File:Traffic Jam,1953.jpg|thumb|upright=1.1|Traffic jam in Los Angeles, 1953]]
[[File:Trafficjamoninterstate5atpyramidlake.jpg|thumb|On Fridays in [[California]], [[Interstate 5]] is often congested as Los Angeles residents travel north for the [[Workweek|weekend]].]]
[[File:Miami traffic jam, I-95 North rush hour.jpg|thumb|Rush hour traffic in Interstate 95 in [[Miami]]]]
[[File:Traffic congestion - US 11E - Morristown, TN.jpg|thumb|Congestion during [[lunch hour]] on [[U.S. Route 11E]] in [[Morristown, Tennessee]]]]
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 [[Gross domestic product|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.<ref>{{Cite web |url=http://shoup.bol.ucla.edu/CruisingForParkingAccess.pdf |title=Cruising for Parking |access-date=August 11, 2016 |archive-date=March 15, 2016 |archive-url=https://web.archive.org/web/20160315094950/http://shoup.bol.ucla.edu/CruisingForParkingAccess.pdf |url-status=live }}</ref>

According to traffic analysis firm [[INRIX]] in 2019,<ref>{{Cite web|last=Levin|first=Tim|title=The 31 US cities that had the worst traffic in 2019 according to a study|url=https://www.businessinsider.com/us-cities-most-traffic-2019-2020-3|access-date=November 25, 2021|website=Business Insider|language=en-US}}</ref> the top 31 worst US traffic congested cities (measured in average hours wasted per vehicle for the year) were:
{| class="wikitable"
|+
!
!City
!Hours wasted per vehicle
!Cost of congestion per driver
|-
!1
|Boston, Massachusetts
|149 hours
|$2,205
|-
!2
|Chicago, Illinois
|145 hours
|$2,146
|-
!3
|Philadelphia, Pennsylvania
|142 hours
|$2,102
|-
!4
|New York City, New York
|140 hours
|$2,072
|-
!5
|Washington, D.C.
|124 hours
|$1,835
|-
!6
|Los Angeles, California
|103 hours
|$1,524
|-
!7
|San Francisco, California
|97 hours
|$1,436
|-
!8
|Portland, Oregon
|89 hours
|$1,317
|-
!9
|Baltimore, Maryland
|84 hours
|$1,243
|-
!10
|Atlanta, Georgia
|82 hours
|$1,214
|-
!11
|Houston, Texas
|81 hours
|$1,199
|-
!12
|Miami, Florida
|81 hours
|$1,199
|-
!13
|New Orleans, Louisiana
|79 hours
|$1,169
|-
!14
|Seattle, Washington
|74 hours
|$1,095
|-
!15
|Stamford, Connecticut
|74 hours
|$1,095
|-
!16
|Providence, Rhode Island
|70 hours
|$1,036
|-
!17
|San Diego, California
|70 hours
|$1,036
|-
!18
|Austin, Texas
|69 hours
|$1,021
|-
!19
|Sacramento, California
|64 hours
|$947
|-
!20
|Dallas, Texas
|63 hours
|$932
|-
!21
|Denver, Colorado
|63 hours
|$932
|-
!22
|Hartford, Connecticut
|61 hours
|$903
|-
!23
|Minneapolis, Minnesota
|52 hours
|$770
|-
!24
|Charlotte, North Carolina
|49 hours
|$725
|-
!25
|San Juan, Puerto Rico
|46 hours
|$681
|-
!26
|Cleveland, Ohio
|44 hours
|$651
|-
!27
|Columbus, Ohio
|43 hours
|$636
|-
!28
|Milwaukee, Wisconsin
|41 hours
|$607
|-
!29
|Detroit, Michigan
|39 hours
|$577
|-
!30
|San Antonio, Texas
|39 hours
|$577
|-
!31
|Boulder, Colorado
|37 hours
|$548
|}
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 (Illinois)|Interstate 290]] at the [[Circle Interchange]]. The average truck speed was just {{convert|29|mi/h|abbr=on}}.<ref>{{cite web | title = Table 3-9. Top 25 Freight Highway Locations by Freight Congestion Index Rating: 2010 | publisher = [[U.S. Department of Transportation]] | year = 2011 | url = http://www.ops.fhwa.dot.gov/freight/freight_analysis/nat_freight_stats/docs/11factsfigures/table3_9.htm | access-date = July 26, 2013 | archive-date = June 6, 2013 | archive-url = https://web.archive.org/web/20130606100926/http://www.ops.fhwa.dot.gov/freight/freight_analysis/nat_freight_stats/docs/11factsfigures/table3_9.htm | url-status = dead }}</ref>

==See also==
{{Portal|Roads|Transport}}
* [[Connected car]]
* [[IBUS (device)]]
* ''[[Journal of Transport and Land Use]]''
* [[Peak car]]
* [[Smeed's law]]
* [[Transims]]
* [[Transportation forecasting]]
* [[Car rental#Tourist rental cars|Tourist rental cars]]
* [[Traffic Message Channel]] (TMC)
* [[Donald Shoup]]
* [[Traffic obstruction]]
* [[Urban planning]]

==References==
{{reflist}}
Bianchi Alves, B., & Darido, G. (February 7, 2016). Sustainable cities, two related challenges: high quality mobility on foot and efficient urban logistics (Part II). Retrieved November 2, 2019, from https://blogs.worldbank.org/transport/sustainable-cities-two-related-challenges-high-quality-mobility-foot-and-efficient-urban-logistics-1.
2019 Top 100 Truck Bottlenecks. (February 14, 2019). Retrieved November 3, 2019, from https://truckingresearch.org/2019/02/06/atri-2019-truck-bottlenecks/.
Haag, M., & Hu, W. (October 27, 2019). 1.5 Million Packages a Day: The Internet Brings Chaos to N.Y. Streets. Retrieved November 1, 2019, from https://www.nytimes.com/2019/10/27/nyregion/nyc-amazon-delivery.html?searchResultPosition=1.
Popovich, N., & Lu, D. (October 10, 2019). The Most Detailed Map of Auto Emissions in America. Retrieved November 1, 2019, from https://www.nytimes.com/interactive/2019/10/10/climate/driving-emissions-map.html?module=inline.
Reed, S. (September 21, 2018). In London, Electric Trucks Are Helping UPS Make 'Eco-Friendly' Deliveries. Retrieved November 3, 2019, from https://www.nytimes.com/2018/09/21/business/energy-environment/electric-ups-trucks-in-london.html?module=inline.
Rooney, K. (April 3, 2019). Online shopping overtakes a major part of retail for the first time ever. Retrieved November 2, 2019, from https://www.cnbc.com/2019/04/02/online-shopping-officially-overtakes-brick-and-mortar-retail-for-the-first-time-ever.html.

==Further reading==
*{{cite journal |last1=Downs |first1=Anthony |title=The Law of Peak Hour Expressway Congestion |journal=Traffic Quarterly |date=July 1962 |volume=16 |issue=3 |pages=393–409 |url=https://trid.trb.org/view.aspx?id=694596 |access-date=January 19, 2022 |issn=0041-0713}}
* [https://www.springer.com/engineering/mechanical+eng/book/978-3-642-02604-1 B.S. Kerner, ''Introduction to Modern Traffic Flow Theory and Control: The Long Road to Three-Phase Traffic Theory'', Springer, Berlin, New York 2009]
* [https://www.springer.com/physics/complexity/book/978-3-540-20716-0 B.S. Kerner, ''The Physics of Traffic'', Springer, Berlin, New York 2004]
* Koslowsky, Meni; Avraham N. Kluger; and Mordechai Reich. Commuting Stress, New York: Plenum, 1995.
* {{cite journal | last1 = Koslowksky | first1 = Meni | last2 = Krausz | first2 = Moshe | title = On the Relationship Between Commuting, Stress Symptoms, and Attitudinal Measures | journal = Journal of Applied Behavioral Science | volume = 1993 | pages = 485–92 }}
* {{cite journal | last1 = Nagel | first1 = K. | last2 = Schreckenberg | first2 = M. | year = 1992 | title = A Cellular Automaton Model for Freeway Traffic | url = https://hal.archives-ouvertes.fr/jpa-00246697/document| journal = Journal de Physique I | volume = 2 | issue = 12| pages = 2221–2229 | doi=10.1051/jp1:1992277| bibcode = 1992JPhy1...2.2221N | s2cid = 37135830 }}
* [[Victoria Transport Policy Institute]] (March 2013), [http://www.vtpi.org/cong_relief.pdf Smart Congestion Relief – Comprehensive Analysis Of Traffic Congestion Costs and Congestion Reduction Benefits]
* R. Wiedemann, Simulation des Straßenverkehrsflusses. ''Schriftenreihe des IfV'', 8, 1974. Institut für Verkehrswesen. Universität Karlsruhe (in German).

==External links==
{{Commons|Traffic jam}}
* [https://www.ite.org/ Institute of Transportation Engineers]
* [https://auto.howstuffworks.com/car-driving-safety/accidents-hazardous-conditions/traffic.htm How Traffic Works from HowStuffWorks.com]

{{Authority control}}

{{DEFAULTSORT:Traffic Congestion}}
[[Category:Road transport]]
[[Category:Road traffic management]]
[[Category:Transport reliability]]