View source for Engineering:Scalable Urban Traffic Control

'''Scalable Urban Traffic Control''' ('''SURTRAC''')<ref name="pat2014"/><ref>Stephen F. Smith, Gregory J. Barlow, Xiao-Feng Xie. [https://patents.google.com/patent/US9159229B2/en Smart and scalable urban signal networks: methods and systems for adaptive traffic signal control]. U.S. Patent No. 9,830,813, 2017. (Continuation-in-part (CIP) to 9,159,229).</ref> is an adaptive traffic control system developed by researchers at the [[Organization:Robotics Institute|Robotics Institute]], [[Organization:Carnegie Mellon University|Carnegie Mellon University]]. SURTAC dynamically optimizes the control of traffic signals to improve [[Traffic flow|traffic flow]] for both urban grids and corridors; optimization goals include less waiting, reduced traffic congestion, shorter trips, and less pollution. The core control engine combines schedule-driven intersection control<ref name="surtrac2012a"/> with decentralized coordination mechanisms.<ref name="surtrac2012b"/><ref>Hu, H-C and S.F. Smith, “Softpressure: A Schedule-Driven Backpressure Algorithm for Coping with Network Congestion”, ''Proceedings 27thInternational Joint Conference on Artificial Intelligence'', Melbourne, Australia, August 2017</ref> Since June 2012, a pilot implementation of the SURTRAC system<ref name="surtrac2013"/> has been deployed on nine intersections in the East Liberty neighborhood of Pittsburgh, Pennsylvania.<ref name="trb2013"/> SURTRAC reduced travel times by more than 25% on average, and wait times were reduced by an average of 40%.<ref name="surtrac2013"/><ref name="cmu 2012-10-16"/> A second phase of the pilot program for the Bakery Square district has been running since October 2013.<ref>Barlow, G.J., S.F. Smith, X-F Xie and Z.B. Rubinstein, “Real-Time Traffic Control for Urban Environments: Expanding the Surtrac Testbed Network”, ''2014 World Congress on Intelligent Transportation Systems'', Detroit, MI, September 2014.</ref> In 2015, Rapid Flow Technologies<ref name=":0">{{Cite web|url=http://www.rapidflowtech.com|title=Rapid Flow Technologies|website=www.rapidflowtech.com|language=en-US|access-date=2018-06-02}}</ref> was formed to commercialize the SURTRAC technology.<ref name="statement_xie">{{Cite web|url=http://www.wiomax.com/team/xie/statement-on-the-scalable-urban-traffic-control-surtrac-technology/|title=Statement on the Scalable Urban Traffic Control Technology|author=Xiao-Feng Xie|language=en-US|access-date=2018-07-03|date=2018-07-03}}</ref> The lead inventor of this technology, Dr. Xiao-Feng Xie, states that he has no association with and does not provide technical support for this company.<ref name="statement_xie"/>
==Design==
The SURTRAC system design has three characteristics.<ref name="surtrac2013"/> First, decision-making in SURTRAC proceeds in a [[Decentralised system|decentralized]] manner. The decentralized control of individual [[Engineering:Intersection (road)|intersections]] enables greater responsiveness to local real-time traffic conditions. Decentralization facilitates [[Scalability|scalability]] by allowing the incremental addition of controlled intersections over time with little change to the existing adaptive network. It also reduces the possibility of a centralized computational [[Software:Bottleneck|bottleneck]] and avoids a [[Single point of failure|single point of failure]] in the system.

A second characteristic of the SURTRAC design is an emphasis on [[Real-time computing|real-time responsiveness]] to changing traffic conditions. SURTRAC adopts the real-time perspective of prior model-based intersection control methods<ref name="tcsrev2003"/> which attempt to compute intersection control plans that optimize actual traffic inflows. By reformulating the [[Optimization problem|optimization problem]] as a [[Finance:Single-machine scheduling|single machine scheduling]] problem, the core [[Mathematical optimization|optimization algorithm]] termed a schedule-driven intersection control algorithm,<ref name="surtrac2012a"/> is able to compute optimized intersection control plans over an extended horizon on a second-by-second basis.

A third characteristic of the SURTRAC design is to manage urban (grid-like) road networks, where multiple competing dominant flows shift dynamically through the day, and where specific dominant flows cannot be predetermined (as in arterial or major [[Engineering:Intersection (road)|crossroad]] applications). Urban networks also often have closely spaced intersections requiring tight coordination of the intersection controllers. The combination of competing for dominant flows and densely spaced intersections presents a challenge for all adaptive traffic control systems. SURTRAC determines dominant flows dynamically by continually communicating projected outflows to downstream neighbors.<ref name="surtrac2012b"/> This information gives each intersection controller a more informed basis for locally balancing competing inflows while simultaneously promoting the establishment of larger "[[Green wave|green corridors]]" when traffic flow circumstances warrant.

==Criticism==
The SURTRAC system employs [[Closed-circuit television|closed-circuit television]] (CCTV) cameras to monitor traffic conditions.<ref>{{cite web |last=Walters |first=Ken |date=2012-10-16 |title=Smart Signals: Pilot Study on Traffic Lights Reduces Pollution, Traffic Clogs |url=http://www.cmu.edu/piper/stories/2012/october/smart-signals.html |accessdate=2013-01-28 |publisher=CMU Piper}}</ref> This use of CCTV networks in public spaces has sparked debate, with some critics arguing that such surveillance can contribute to an erosion of [[Privacy|privacy]] and potentially facilitate more [[Social:Authoritarianism|authoritarian]] forms of governance by reducing the anonymity of individuals in public areas.<ref>{{Cite journal |last=Watt |first=Eliza |date=2017-05-23 |title='The right to privacy and the future of mass surveillance' |url=http://dx.doi.org/10.1080/13642987.2017.1298091 |journal=The International Journal of Human Rights |volume=21 |issue=7 |pages=773–799 |doi=10.1080/13642987.2017.1298091 |issn=1364-2987 |s2cid=148928418}}</ref> Moreover, CCTV footage can be processed with technologies like [[Automatic number-plate recognition|automatic number plate recognition]] software, enabling the tracking of vehicles based on their license plates. Facial recognition software can also analyze these images to identify individuals by their facial features. However, it is noted that the resolution of the cameras utilized in the SURTRAC system is reportedly not high enough to enable the detection of license plates or the recognition of individual faces.<ref name=":0" />

There has also been discussion regarding the overall efficacy and impact of [[Engineering:Traffic optimization|traffic optimization]] systems. Critics have suggested that the benefits of such systems have not been conclusively proven through scientific study. Additionally, concerns have been raised that these systems might inherently favor motorized traffic, potentially leading to disadvantages for pedestrians, bicyclists, and public transit users, and could inadvertently encourage increased use of automobiles.<ref>{{Cite web |title=Article: Traffic Signal Synchronization |url=http://www.imaja.com/as/environment/mvarticles/TrafficSigSynch1.html |access-date=2023-01-28 |website=www.imaja.com}}</ref><ref>{{cite web |last=Meyer |first=Robinson |date=2012-08-16 |title=Sorry, Los Angeles: Synchronizing Traffic Lights May Not Reduce Emissions |url=https://www.theatlantic.com/technology/archive/2012/08/sorry-los-angeles-synchronizing-traffic-lights-may-not-reduce-emissions/261231/ |accessdate=28 January 2013 |publisher=Theatlantic.com}}</ref>

==See also==
*[[Engineering:Traffic optimization|Traffic optimization]]
*Adaptive traffic control
*[[Engineering:Smart traffic light|Smart traffic signals]]
*Traffic light control and coordination
*[[Engineering:Intelligent transportation system|Intelligent transportation system]]
*[[Finance:Transportation demand management|Transportation demand management]]
*[[Automated planning and scheduling]]

==Other adaptive traffic control systems==
*[[Engineering:Sydney Coordinated Adaptive Traffic System|Sydney Coordinated Adaptive Traffic System]]

==References==
{{reflist|
refs=
<ref name="pat2014">Xiao-Feng Xie, S. Smith, G. Barlow. [https://patents.google.com/patent/US9159229B2/en Smart and Scalable Urban Signal Networks: Methods and Systems for Adaptive Traffic Signal Control]. U.S. Patent No. 9,159,229, 2015.</ref>
<ref name="cmu 2012-10-16">{{cite web|url=http://www.cmu.edu/piper/stories/2012/october/smart-signals.html|title=Pilot Study on Traffic Lights Reduces Pollution, Traffic Clogs|publisher=[[Organization:Carnegie Mellon University|Carnegie Mellon University]]|work=CMU website|date=October 16, 2012|accessdate=January 31, 2013|author=Walters, Ken}}</ref>
<ref name="surtrac2012b">Xiao-Feng Xie, Stephen F. Smith, Gregory J. Barlow. [http://www.aaai.org/ocs/index.php/ICAPS/ICAPS12/paper/view/4701 Schedule-driven coordination for real-time traffic network control]. International Conference on Automated Planning and Scheduling (ICAPS), Sao Paulo, Brazil, 2012: 323-331.</ref>
<ref name="surtrac2012a">Xiao-Feng Xie, Stephen F. Smith, Liang Lu, Gregory J. Barlow. [https://dx.doi.org/10.1016/j.trc.2012.03.004 Schedule-driven intersection control]. Transportation Research Part C: Emerging Technologies, 2012, 24: 168-189.</ref>
<ref name="surtrac2013">Stephen F. Smith, Gregory J. Barlow, Xiao-Feng Xie, Zachary B. Rubinstein. [http://www.aaai.org/ocs/index.php/ICAPS/ICAPS13/paper/view/6054 Smart urban signal networks: Initial application of the SURTRAC adaptive traffic signal control system]. International Conference on Automated Planning and Scheduling (ICAPS). Rome, Italy, 2013.</ref>
<ref name="tcsrev2003">M. Papageorgiou, C. Diakaki, V. Dinopoulou, A. Kotsialos, and Y. Wang.  Review of road traffic control
strategies. Proceedings of the IEEE, 2003, 91(12):2043–2067.</ref>
<ref name="trb2013">Stephen F. Smith, Gregory Barlow, Xiao-Feng Xie, and Zack
Rubinstein. [http://www.ri.cmu.edu/publication_view.html?pub_id=7408 SURTRAC: Scalable Urban Traffic Control]. Transportation Research Board 92nd Annual Meeting Compendium of Papers, 2013.</ref>
}}

==External links==
*[https://www.rapidflowtech.com/surtrac SURTRAC adaptive traffic signal control]
*[http://www.wiomax.com/team/xie/surtrac/ Information about core algorithms and further developments]

[[Category:Intelligent transportation systems]]

{{Sourceattribution|Scalable Urban Traffic Control}}