Editing Gridlock

{{Short description|Form of traffic congestion; used as an analogy for processes that fail to progress}}
{{Other uses}}

[[Image:GridlockCorrected.png|right|thumb|Gridlock on a network of two-way streets. The red cars are those causing the gridlock by stopping in the middle of the intersection.]]
'''Gridlock''' is a form of [[traffic congestion]] where continuous queues of vehicles block an entire network of intersecting streets, bringing traffic in all directions to a complete standstill. <ref>{{cite dictionary|url=http://www.oed.com/viewdictionaryentry/Entry/249126|url-access=subscription|title=Gridlock|publisher=Oxford University Press|access-date=2011-05-03|dictionary=Oxford English Dictionary}}</ref>  The term originates from a situation possible in a [[grid plan]] where intersections are blocked, preventing vehicles from either moving forwards through the intersection or backing up to an upstream intersection.

The term ''gridlock'' is also used incorrectly to describe high [[traffic congestion]] with minimal flow (which is simply a traffic jam), where a blocked grid system is not involved. By extension, the term has been applied to situations in other fields where flow is stalled by excess demand, or in which competing interests prevent progress.

==Cause==
[[File:Gridlock (Wiesbaden, Germany).jpg|thumb|Gridlock on Kaiser-Friedrich-Ring, Wiesbaden, Germany. Vehicles on three lanes blocking each other's way.]]
[[File:7th Street gridlock afternoon.jpg|thumb|Traffic gridlock in [[Miami]], [[Florida]]. Lights are green but backups fill all the space.]]
Traditional gridlock is caused by cars entering an intersection on a green light without enough room on the other side of the intersection ''at the time of entering'' to go all the way through.  This can lead to the car being trapped in the intersection when the light turns green in the other direction.  If the same situation occurs simultaneously in multiple intersections, these cars can be trapped in the intersections indefinitely.

In many jurisdictions, drivers are therefore prohibited from entering an intersection at a green light if there is no room for them to clear the intersection. If all drivers follow this rule, gridlock is impossible.<ref>Stringer, Scott M. ''[http://www.mbpo.org/uploads/policy_reports/mbp/DONT%20BLOCK%20THE%20BOX.pdf Thinking outside the box: an analysis of Manhattan gridlock and spillback enforcement]'', Office of Manhattan Borough President, July 2006. {{Dead link|date=January 2020}}</ref>

Another type of gridlock can occur during traffic surges between highway on-ramps and off-ramps located within a quarter mile of each other. Traffic exiting the highway may back up and block the entering vehicles.  Those entering vehicles in turn back up and block the exiting vehicles.

Gridlock is sometimes cited as an example of the [[prisoner's dilemma]] (from [[game theory]]).<ref>Heath, Joseph (1999). ''[http://www.utm.utoronto.ca/~w3phl296/text/table.html Normative economics] {{Webarchive|url=https://web.archive.org/web/20071118023857/http://www.utm.utoronto.ca/~w3phl296/text/table.html |date=2007-11-18 }}'', Chapter 2, Section 3. Retrieved 2007-03-19.</ref> Mutual cooperation among drivers would give the maximum benefit (prevention of gridlock), but this may not happen because of the desire to maximize one's own benefit (shortest travel time) given the uncertainty about the other drivers' commitment to equal cooperation.

==Enforcement==

===New York City===
[[File:NYCDOT SR-1258.svg|thumb|left|100px|Don't block the box sign]]
[[Image:New York City Gridlock.jpg|thumb|Vehicles "blocking the box" in New York City]]
In [[New York City]], drivers who "[[Box junction|block the box]]" are subject to a moving violation that comes with a US$90.00 penalty. Mayor [[Michael Bloomberg]], noting that the ten-minute ticketing process actually contributes to overall [[traffic congestion]], has asked the [[New York State Legislature]] to remove "blocking the box" from the moving violation category. This reclassification would give more traffic agents authority to write tickets and change the current ticketing procedure, which requires that the issuing officer physically stop the violating car in traffic.<ref>{{Cite web |url=http://ny.metro.us/metro/local/article/Bloomberg_crackdown_on_gridlock_/8745.html |title=metro<!-- Bot generated title --> |access-date=2007-10-26 |archive-date=2008-12-14 |archive-url=https://web.archive.org/web/20081214190950/http://ny.metro.us/metro/local/article/Bloomberg_crackdown_on_gridlock_/8745.html |url-status=live }}</ref>

===Virginia Beach, Virginia===
In [[Virginia Beach, Virginia]], roads around the oceanfront feature signs at every intersection stating "Don't Block the Box", and threatening a $200 fine.

===Texas===
In [[Austin, Texas]], a "Don't Block the Box" initiative began in 2015.<ref>{{cite web | url=http://kxan.com/2015/04/24/some-drivers-feel-trapped-by-dont-block-the-box-enforcement/ | title=Some drivers feel trapped by 'Don't Block the Box' enforcement | date=25 April 2015 | publisher=KXAN | access-date=2015-06-30 | archive-date=2015-07-03 | archive-url=https://web.archive.org/web/20150703140602/http://kxan.com/2015/04/24/some-drivers-feel-trapped-by-dont-block-the-box-enforcement/ | url-status=live }}</ref><ref>{{cite web | url=http://kxan.com/2015/04/21/more-than-800-tickets-issued-for-blocking-the-box/ | title=More than 800 tickets issued for 'blocking the box' | date=21 April 2015 | publisher=KXAN | access-date=2015-06-30 | archive-date=2015-07-03 | archive-url=https://web.archive.org/web/20150703140920/http://kxan.com/2015/04/21/more-than-800-tickets-issued-for-blocking-the-box/ | url-status=live }}</ref>  A similar program was piloted in [[San Antonio]] in 2017.<ref>{{cite web | url=https://www.sanantonio.gov/Commpa/News/ArtMID/1970/ArticleID/10516/Enforcement-Begins-Today-for-Don%E2%80%99t-Block-the-Box-Pilot-Program | title=Enforcement Begins Today for Don't Block the Box Pilot Program | publisher=City of San Antonio | access-date=2017-05-04 | archive-date=2017-08-10 | archive-url=https://web.archive.org/web/20170810041913/http://www.sanantonio.gov/Commpa/News/ArtMID/1970/ArticleID/10516/Enforcement-Begins-Today-for-Don%e2%80%99t-Block-the-Box-Pilot-Program | url-status=live }}</ref>

==Effects==
The obvious effects are driver frustration and trip delay. Another effect in cities is exacerbated by the presence of [[urban canyon|urban street canyons]], which effectively trap [[air pollution]] and increase air pollution exposures of motorists as well as the general urban population.  Noise pollution can be aggravated by excessive starting and stopping noise of gridlocked facilities.<ref>''[http://www.worldcatlibraries.org/wcpa/top3mset/2930880 C. Michael Hogan and Gary L. Latshaw, The relationship between highway planning and urban noise] {{Webarchive|url=https://web.archive.org/web/20070518225130/http://www.worldcatlibraries.org/wcpa/top3mset/2930880 |date=2007-05-18 }}'', :Proceedings of the ASCE, Urban Transportation Division specialty conference, May 21–23, 1973, Chicago, Illinois. by American Society of Civil Engineers. Urban Transportation Division</ref>

==Alleviating gridlock==
To make a traffic system less susceptible to gridlock, a traffic metering system can be introduced. These systems determine the optimal number of vehicles allowed in a traffic system, and prevent any extra vehicles from entering. This can be done with traffic control devices, such as [[traffic lights]] or warning signs, or a better public transportation system. This type of system is used in [[Zurich, Switzerland]].<ref>{{cite journal | last1 = Daganzo | first1 = Carlos F. | year = 2007 | title = Urban gridlock: Macroscopic modeling and mitigation approaches | journal = Transportation Research Part B: Methodological | volume = 41 | issue = 1| pages = 49–62 | doi = 10.1016/j.trb.2006.03.001 | bibcode = 2007TRPB...41...49D }}</ref>

==Etymology==
According to ''[[The New York Times]]'', the word ''gridlock'' was coined in [[New York City]] in the early 1970s.<ref>{{Cite news|url=https://www.nytimes.com/1988/05/08/magazine/national-gridlock.html|title=National Gridlock|author=James Gleick|work=[[New York Times]]|date=1988-05-08|access-date=2010-09-26|archive-date=2015-05-25|archive-url=https://web.archive.org/web/20150525083512/http://www.nytimes.com/1988/05/08/magazine/national-gridlock.html|url-status=live}}</ref>  The word appeared in an IEEE publication in 1971 in a different context.<ref>{{Cite web|url=https://books.google.com/books?id=HHMYAQAAIAAJ&q=%22gridlock%22|title=Engineering in the Ocean Environment: A Method for Reducing Gridlock Errors|last=Letton|first=Winsor|date=1971|website=Google Books|access-date=2020-09-14|archive-date=2022-04-07|archive-url=https://web.archive.org/web/20220407061926/https://books.google.com/books?id=HHMYAQAAIAAJ&q=%22gridlock%22|url-status=live}}</ref> The first appearances of ''gridlock'' in newspapers occurred during the [[1980 New York City transit strike]]. The word is attributed to [[Sam Schwartz]], who was then the chief traffic engineer for the [[New York City Department of Transportation]] at the time of the strike.<ref>Schwartz, Sam. ''[http://www.gridlocksam.com/about.html About Gridlock Sam] {{Webarchive|url=https://web.archive.org/web/20050824212100/http://www.gridlocksam.com/about.html |date=2005-08-24 }}'', GridlockSam.com. Retrieved 2007-03-19.</ref> Schwartz said the word ''gridlock'' was used internally in his department during the 1970s, perhaps as early as 1971.<ref>Popik, Barry (July 21, 2004). ''[http://www.barrypopik.com/index.php/new_york_city/entry/gridlock/ Gridlock] {{Webarchive|url=https://web.archive.org/web/20061028080918/http://www.barrypopik.com/index.php/new_york_city/entry/gridlock/ |date=2006-10-28 }}''. Retrieved 2007-03-19.</ref> Writing up a memo of emergency recommendations for senior officials, he recalled the words of a colleague several years earlier who had been analyzing a proposal to close Broadway to vehicular traffic. His colleague gave the plan the thumbs-down, worrying that it would simply "lock up the grid". Schwartz was always struck by that image and titled his 1980 memo "Gridlock Prevention Plan".<ref>Kluger, Jeffrey: "Simplexity: Why Simple Things Become Complex (And How Complex Things Can Be Made Simple)", Hyperion, 2008,  {{ISBN|978-1-4013-0301-3}}, pp.65-66.</ref> In another interview Mr. Schwartz said that he coined the term in the mid 1970s with fellow traffic engineer, Roy Cottam, who "was a little paranoid and thought he would be blamed for gridlock and so he gave me all the credit".<ref>{{Cite web|url=http://simcity.ea.com/about/inside_scoop/gridlocksam.php|title=Gridlock Sam Interview|publisher=SimCity 4|access-date=2010-09-26|archive-url=https://web.archive.org/web/20110318043405/http://simcity.ea.com/about/inside_scoop/gridlocksam.php|archive-date=2011-03-18|url-status=dead}}</ref>

==See also==
* [[Box junction]]
* [[Deadlock (computer science)|Deadlock]] - computer software analogy
*''[[Journal of Transport and Land Use]]''
* [[Roadway air dispersion modeling]]
* [[Rush Hour (puzzle)]]

==References==
{{Reflist|35em}}

[[Category:Road transport]]