traffic signal control
De Schutter, B., & De Moor, B. Specifically, Feng et al. Aside from movable parts, electrical relays are also used. For example, VISSIM [8, 29, 41, 57, 71], NETSIM [31, 60, 70], AIMSUN [46, 65, 75], and several other traffic simulation tools have been used to evaluate the performance of traffic models. Passenger cars are considered normal vehicles that are not given any priority. Dell'Olmo, P., & Mirchandani, P. (1995). Adopting the fixed-timed strategy assumes that traffic demand remains similar at all times to calculate the optimal signal plans based on historical traffic information. Procedia - Social and Behavioral Sciences, 54, 1270–1277. Oversaturated signal systems with queue length constraints—I: Single intersection. The adaptive strategy has been implemented using various other prediction algorithms, and several adaptive signal control systems have been developed accordingly. Although various formulations and solution approaches have been applied to solve ITSCPs over the decades, there are still many opportunities for future work. It is a computer that processes information received from the detector loops and pedestrian push buttons and changes … Controlled optimization of phases at an intersection. The cell transmission model: A dynamic representation of highway traffic consistent with the hydrodynamic theory. Most early researchers employed a rule-based method to solve the ITSCP [14, 18, 22, 24, 33]. Traffic signal control is an important tool in traffic flow management as it is considered as one of the most effective ways to reduce traffic congestion at intersections . http://hdl.voced.edu.au/10707/412253. Furthermore, a traffic flow group is defined as one or more compatible movements of road users, and each phase has a set of timings for each traffic flow group. Lin, W. H., & Wang, C. (2004). Terms and Conditions, This information is processed in accordance with the model formulation. Bing, B., & Carter, A. There are, however, various solution approaches that have been applied to ITSCPs regardless of problem size or conditions, including those employing a rule-based method, genetic algorithm (GA), simulation-based approach, dynamic programming (DP), multi-agent system (MAS), game theory approach, neural network (NN), or reinforcement learning (RL), which are reviewed in this section. 2, the phases in both rings must be simultaneously turned to red at the barrier. (1969). Reinforcement learning has been widely used as a practical computational tool to obtain an optimal control policy [30]. Additionally, determining the appropriate size of a network to enable practical utilization appears to be a crucial research topic. In this diagram, a ring is a sequence of phases that are incompatible and thus must be served in a particular order, and a barrier is a reference point in the cycle at which a phase in each ring has reached its point of termination. INTRODUCTION On many of the traffic control systems, the signal scheduling for traffic regulation works on a fixed-time basis, where a series of signal timing plans are employed based on At an intersection, the movements of various users such as vehicles and pedestrians follow the rules indicated by traffic signals. Lights are timed in such a way that motorists can drive through without stopping if their speed is lower than a given limit, mostly 50 km/h (30 mph) in urban areas. Go Retro for advanced traffic management 1300 197 683 info@retrotraffic.com.au Vehicle stops, which occur due to a red light or accumulated queue, are directly related to driver satisfaction. Actions can then be taken to switch the phase sequence or extend the green phase duration. Dashed lines represent the network extent for each problem. Reinforcement learning-based multi-agent system for network traffic signal control. Transportation Research Part C: Emerging Technologies, 14(1), 18–38. In this review, unless otherwise specified, drivers are on the right-hand side of the road and right-turn movements are not explicitly controlled by traffic signals. Critically, the size and shapes of networks as well as the categories of road users have diversified over time, and as communications technology and computational methods have been developed, strategies dealing with real-time traffic data have become popular in the ITSCP field. The traffic signal controller performs traffic flows control at intersections. 3, ITSCP network types can be classified as isolated intersections, arterial networks, and general networks. IEEE Transactions on Intelligent Transportation Systems, 16(4), 2247–2256. Because adaptive strategies require highly accurate prediction algorithms as well as good signal plan optimization, developing algorithms based on an adaptive strategy could be more difficult than when doing so based on an actuated strategy. In addition, some intersection networks contain specifically designed lanes that allow unusual vehicle movements, such as contra-flow bus lanes and U-turn lanes. Journal of Transportation Technologies, 9(4), 489. [7] The TS-1 standard was introduced in 1976 for the first generation of solid-state controllers.[9]. Urban traffic signal control with connected and automated vehicles: A survey. Some studies conducted within an assumed connected vehicle environment have also used the total travel time of vehicles as a performance index [67]. As automated and connected vehicle technologies have recently become more popular, further research on the ITSCP continues to be necessary. [69] proposed separate vehicle and bicycle models for the ITSCP to reflect the ability of bicycles to be accommodated in smaller spaces as well as the simpler description of the dynamic behavior of bicycles. Improta and Cantarella [28] first expanded the type of road users considered to include pedestrians in addition to a single type of passenger car. Washington, DC: Transportation Research Board. In addition to intersection network types, real-world problem features including road user types, physical properties of the road, and traffic flows should be considered in order to generalize solutions to the ITSCP. Bluetooth in intelligent transportation systems: A survey. Fuzzy Sets and Systems, 116(1), 11–22. Transportation Research Record, 1365, 108–115. These systems include ACS-Lite [81], SCATS [82], SCOOT [83], OPAC [84], MOTION [85], UTOPIA [86], and RHODES [6]. [58] formulated a mathematical model based on the CTM and developed a heuristic approach based on a GA to reduce the extensive computation time required to solve the mathematical model for large networks. Multi-modal traffic signal control with priority, signal actuation and coordination. As such, optimizing traffic signals for networks comprised of various road users is necessary for real-world implementation. SCATS® and SCATS® Compliant traffic signal controllers communicate with each other such that SCATS® "sees" where the demands are coming from and with the controller are given green time, but if there are no demands say from pedestrians or turning vehicles for diamond turns then SCATS® and the Traffic Signal Controllers "skip" the unneeded time and allocate it to those movements where it is … To balance each traffic signal phase and each direction in an intersection, the concept of queue length, defined as the total number of vehicles waiting on the roads at each intersection, has been used. [57] proposed the minimization of the average queue length as an additional objective of an ITSCP. For a network with outdated signal control, FTOD and TAC can be considered for updating traffic control. Transportation Research Record, 2259(1), 223–232. VISSIM: A microscopic simulation tool to evaluate actuated signal control including bus priority. Transportation Research Record, 1856(1), 175–184. Some researchers have claimed that the control system should use a fixed signal phase sequence so as not to confuse drivers, while others have argued against a fixed phase sequence for the sake of performance improvement. B., & Lee, Y. J. (2004). Field implementation feasibility study of cumulative travel-time responsive (CTR) traffic signal control algorithm. Transportation Research, 6(3), 245–255. In this review, we assumed that the traffic on the roads consists of passenger cars, pedestrians, transit vehicles and their passengers, emergency vehicles, motorcycles, HGVs, LGVs, and bicycles for the ITSCP. Choy et al. Transportation Research Part C: Emerging Technologies, 85, 732–752. [75] employed a microscopic emissions/fuel consumption model to minimize both exhaust products such as carbon dioxide and fuel consumption to improve sustainability. A computer control scheme for critical-intersection control in an urban network. Note that the number of arrows pointing into a node may not match the number of cited papers because references that were not cited by other reviewed papers were omitted from the figure. McKinsey & Company predicted that up to 15% of new cars sold in 2030 could be fully autonomous [102]. Development of dynamic transit signal priority strategy. Part of Research and experiments show that traffic accidents are reduced by 72% on turbo roundabouts compared to multi-lane roundabouts, which have 12 points of conflict. The selection of the minimum and maximum green phase durations is dependent on the traffic characteristics of the study area and the space available for vehicles to queue [76]. SIV-DSS: Smart in-vehicle decision support system for driving at signalized intersections with V2I communication. In general, electro-mechanical signal controllers use dial timers that have fixed, signalized intersection time plans. Due to the highly stochastic nature of the ITSCP, problem complexity is a crucial consideration. Bicycles in particular have recently emerged as an alternative transportation mode, and studies have accordingly been conducted to investigate the interactions between bicycles and passenger cars, minimize the delay of cyclists, or explicitly consider two-stage bicycle left turns [69, 107]. Introduction. Furthermore, new vehicle detection technologies can provide various data that were unattainable in the past to serve as input data for traffic signal control algorithms. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. volume 12, Article number: 50 (2020) All intersections are four-legged intersections. Some authors compared the aggregated average speed of vehicles [9] and the number of vehicles in bottleneck links [59]. Article [12] In some countries (e.g. Additionally, as new solution methods are developed, they are typically first validated using a small network. Christofa, E., Ampountolas, K., & Skabardonis, A. Advanced cars with vehicle-to-infrastructure (V2I) and vehicle-to-vehicle (V2V) connectivity have also recently been developed. As communication technology continues to rapidly develop, more research into solving the ITSCP with priority consideration is expected. Control Engineering Practice, 14(10), 1213–1229. Res. 4, the most important papers in the ITSCP field can readily be identified, and node information such as author(s) and publication year can be extracted. When setting the minimum green time to accommodate a pedestrian crossing, the minimum duration depends on the width of the crossing and the assumed walking speed of the pedestrians [35]. REALBAND: An approach for real-time coordination of traffic flows on networks. Proceedings of the IEEE, 91(12), 2043–2067. Transportation Research Part C: Emerging Technologies, 14(4), 263–282. Based on these theoretical foundations, various algorithms have since been proposed considering the rapid development of traffic infrastructure such as vehicular actuated systems and induction loop detectors [6]; this review focuses on these algorithms. Green light extension prolongs the green phase based on traffic flow rate. To balance queue length for all roads in the subject network, Sen and Head [37] and De Schutter [62] minimized the maximum queue length. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. Yin, Y. For example, Lee et al. For example, the maximum delay that any individual vehicle may experience can be limited to ensure equity in a connected vehicle environment. Shock waves on the highway. Such standards could also contribute to the standardization of ITSCP terminology, aiding research, communication, and development of traffic control methods. Although traffic signal lights are relatively simple and Signal timing manual. 1995). The cycle is the total time required to complete one signalization sequence for all movements at an intersection, the phase is the controller timing unit associated with one or more movements, and the duration is the amount of time the signal spends in each phase, during which the signal indications do not change [11]. A review across the entire body of knowledge throughout the history of the ITSCP is therefore provided. In this section, we present the trends of several aspects of ITSCP research including problem features, solution approach, and infrastructure development. Koonce, P., & Rodegerdts, L. (2008). One electrical output from the traffic signal controller is called a "signal group" - similar to the UK and USA concept of "phase". The GA is a remarkable heuristic method that has been widely used in signal timing design for decades since Foy et al. According to Table 5, most studies constrained the phase sequence of the traffic signal to a fixed sequence or a set of predefined sequences. Cycle lengths of signalized intersections are determined by small gears that are located within dial timers. Rev. Dynamic network traffic control. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. IEEE Transactions on Vehicular Technology, 62(4), 1459–1471. Studies considering transit vehicles as road users are typically related to priority consideration, and studies accounting for pedestrians typically limit the minimum value of the green phase durations to ensure adequate crossing time. Synchronized signals all change at the same time and are only used in special instances or in older systems. With increasing attempts to control traffic networks in a distributed way, the MAS has been investigated as an important solution approach [78]. In another approach to modeling the dynamics of traffic network systems, Portilla et al. Cycle gears, as they are commonly known, range from 35 seconds to 120 seconds. Furthermore, reaction time can be ignored when selecting the cycle time for autonomous vehicles, though safety will continue to be a critical performance index to prevent vehicle collisions. Note that these reference numbers are different from the node IDs presented in Table 1. In other words, the phenomenon that vehicles may change their routes if they experience long delays must be considered in future work. In this paper, we reviewed the available literature to provide a comprehensive overview of the various methods that have been applied to solve the problem of traffic signal control at intersections. Speed is self-regulated in coordinated signal systems; drivers traveling too fast will arrive on a red indication and end up stopping, drivers traveling too slowly will not arrive at the next signal in time to utilize the green indication. Many researchers have solved optimization problems and evaluated their models using these simulation tools. Gartner, N. H. (1983). Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Finally, Section 6 summarizes the current state of research and suggests directions for future research. 12, 50 (2020). Transportation research part C: emerging technologies, 19(1), 130–144. Learn how and when to remove this template message, Meadowlands Adaptive Signal System for Traffic Reduction, Sydney Coordinated Adaptive Traffic System, "Josef Kates Found Ways to Unsnarl Traffic and Solve Business Problems With Computers", https://www.gov.uk/government/publications/traffic-advisory-leaflets-1989-to-2009, http://www.traffic-signal-design.com/terminology_main.htm, Choreographing the Dance of Traffic Lights, New York Times, September 17, 1998, "Senate Bill 84 XX Battery Backup Program for Light Emitting Diode (LED) Traffic Signals", "Adelaide Coordinated Traffic Signal (ACTS) System", Real-time traffic control for sustainable urban living, "Hands on control: New South Wales Transport Management Centre", "Meadowlands Adaptive Signal System for Traffic Reduction", "During Pulaski Skyway Closure, Traffic Lights to Be Adjusted on Local Roads", "High-tech signal system helps speed Meadowlands traffic", "New York's award-winning traffic control system", "Removal Of Signal Flashing Mode During Late-Night / Early-Morning Operation", Comparison of MUTCD-influenced traffic signs, Comparison of traffic signs in English-speaking countries, https://en.wikipedia.org/w/index.php?title=Traffic_light_control_and_coordination&oldid=1015469952, Articles needing additional references from March 2009, All articles needing additional references, Articles with unsourced statements from January 2020, Articles containing potentially dated statements from 2013, All articles containing potentially dated statements, Creative Commons Attribution-ShareAlike License, Increasing the traffic handling capacity of roads, Reducing collisions and waiting time for both vehicles and pedestrians, Encouraging travel within the speed limit to meet green lights, Reducing unnecessary stopping and starting of traffic - this in turn reduces fuel consumption, air and, This page was last edited on 1 April 2021, at 17:25. Xie, X. F., & Wang, Z. J. For instance, most researchers have minimized the delay per vehicle in the timing and control of traffic signals, but their definitions of delay may differ. Some studies have combined RL with fuzzy relations or neural networks (NN). The ITSCP is further complicated by not only the randomness of vehicular arrivals at an intersection, but also by the various configurations and numbers of intersections, types of vehicles in the network, and the different priorities of real-time traffic management strategies. Transportation Science, 10(1), 1–19. From a practical perspective, the slope and speed limit of roads, which are related to acceleration and deceleration rates, and the road capacity, which is used to calculate the volume of traffic flow that an intersection network can handle, are crucial issues. Model-based predictive control for bicycling in urban intersections. The traffic signal control problem for intersections: a review. Distributed and cooperative fuzzy controllers for traffic intersections group. By combining the concepts of cycle, phase, and duration, a signal phase sequence can be defined that represents a sequence of vehicle movements regulated by the signal controller. In the areas that are prone to power interruptions, adding battery backups to the traffic controller systems can enhance the safety of the motorists and pedestrians. As stated by Han et al. There may be additional phases for other movements such as pedestrians, cyclists, bus lanes or tramways. SCOOT: The world's foremost adaptive TRAFFIC control system. Another new type of vehicle detector, the Bluetooth sensor, can estimate the travel times and velocities of vehicles and detect the turning movement of each vehicle at low installation and maintenance costs [105]. Table 6 summarizes the ITSCP literature based on the solution methods reviewed in Section 5 and the problem features, in which the columns indicate the major methods used to solve the ITSCP and the rows represent the target intersection network type and real-time strategy employed. But the recent introduction of the flashing yellow arrow (see Traffic-light signalling and operation) makes the lead-lag signal, an aid to progression, available with protected/permissive turns.[12][13]. 'TMC Signal Control' provides the capability for traffic managers to monitor and manage the traffic flow at signalized intersections. The first automated system for controlling traffic signals was developed by inventors Leonard Casciato and Josef Kates and was used in Toronto in 1954.[1][2][3]. The largest traffic network evaluated with RL was a general network containing 29 traffic lights studied by Balaji et al. Enhanced genetic algorithm for signal-timing optimization of oversaturated intersections. The recent application of RL and MAS to large intersections and complex traffic situations has enhanced the ability of researchers to study the ITSCP at larger scales. Transportation Research Part B: Methodological, 42(10), 911–924. A stage is a group of non-conflicting phases which move at the same time.[6]. Lowrie, P. R. (1982). [23] represented an intersection as a non-cooperative game in which each player (signal) tries to minimize its queue and then found the Nash equilibrium as the solution of the ITSCP. [7], In the United States, controllers are standardized by the NEMA, which sets standards for connectors, operating limits, and intervals. The signal phase sequence represents a kind of rule between vehicle drivers and traffic signals. Traffic lights must be instructed when to change stage and they are usually coordinated so that the stage changes occur in some relationship to other nearby signals or to the press of a pedestrian button or to the action of a timer or a number of other inputs. Transportation Research Record, 718, 1–5. We described the ITSCP and classified the related literature in terms of the various aspects of the problem. Traffic signal control at intersections plays a significant role in mobility, traffic safety, and the city environment. Transportation Research Part C: Emerging Technologies, 46, 121–131. Autonomous Agents and Multi-Agent Systems, 18(3), 342. Many US cities set the green wave on two-way streets to operate in the direction more heavily traveled, rather than trying to progress traffic in both directions. B., Lee, J., Lee, H., & Son, S. H. (2016). Housed in a grey metal box on a corner of the intersection, the controller is the 'brain' of the system. For example, Dunne and Potts [14] solved the ITSCP for an isolated intersection with a maximum of two lanes on each leg. Transportation Research Part C: Emerging Technologies, 72, 182–201. Solid state controllers are required to have an independent conflict monitor unit (CMU), which ensures fail-safe operation. [41] gave priority not only to transit vehicles, but also to emergency vehicles. The intersection traffic signal control problem (ITSCP) has become even more important as traffic congestion has been more intractable. [8] proposed a multi-resolution strategy for updating the elements of the signal plans that included a cycle-by-cycle signal phase sequence and adjusted the current second-by-second green signal timing. MathSciNet PubMed Google Scholar. Xie, X. F., Smith, S. F., Lu, L., & Barlow, G. J. Because constructing a Q-learning model in ITSCP requires a considerable number of states and actions, Prashanth and Bhatnagar [36] modified the model to include function approximation and solved the problem for multiple networks including a 3 × 3 grid of intersections and a 1 × 8 arterial network. Research on the ITSCP has grown much more important with increasing traffic congestion. As new connected and autonomous vehicle technologies are still being developed, improvements in algorithm robustness with respect to system malfunctions including noisy and delayed state measurements, communication dropouts, or other incidents are necessary to handle the exceptional cases and address potential safety concerns [87]. Vehicle connectivity can now be classified into these two different types according to the communications target: V2I gathers the data generated by vehicles at infrastructure points to share traffic information from infrastructure to vehicles; V2V involves communications among vehicles regarding their speed, position, and traffic situation. Traffic Signal Timing Manual(no. IET Intelligent Transport Systems, 4(3), 177–188. A multi-band approach to arterial traffic signal optimization. Similarly, further study on ITSCPs in a connected vehicle environment is required. Furthermore, traffic signal control should be investigated under a scenario in which both connected or autonomous vehicles share the road network with conventional vehicles as it will take time for all vehicles on the road to be fully updated with such new intelligent vehicle technologies. Urban traffic control problem: A game theory approach. Abdulhai et al. [71] also considered the connected vehicle environment. Motivated by its generality, some researchers have used DP to develop a flexible control algorithm applicable to a variety of performance measures and traffic conditions [6, 27, 37, 44]. In addition to GA-based simulation programs, general simulation-based approaches have been proposed by many researchers to account for traffic flow interactions [38]. Portilla et al. Analytic methods such as the branch and bound (B&B) algorithms have been used to solve iteratively small and simple ITSCPs. Powerful traffic signal control to improve traffic flow and operations ; Intuitive user interface and menu structure; Reduce maintenance costs and boost interoperability; Overview. Traffic signal control is one of the most efficient methods for urban traffic management, providing a smoother and more secure traffic flow at every intersection. The framework Q-learning with deep neural network makes use of the agent to control traffic signal to minimise waiting time for a 4-way intersection with 1 incoming lane and 3 outgoing lanes. Gazis, D. C. (1964). MATH Citation network for the literature reviewed in this paper and defined in Table 1. Since the computational demand of the recursive calculations in DP dramatically increases as the network size increases, Cai et al. The CMU is programmed with the allowable combinations of lights, and will detect if the controller gives conflicting directions a green signal, for instance. [32] simplified traffic flow as a set of vehicle movements at an isolated intersection and determined when to switch the green–red signal for each vehicle movement. Then the signals will have flashing red lights for another two hours. In addition to the approaches discussed above, the Petri net has also been used to model ITSCP states. Sophisticated traffic signal control software suite. IEEE Transactions on Automatic Control, 55(11), 2612–2617. (2019). Finally, ‘-‘ means that no information for the given column is provided in the subject paper. Zhu, F., & Ukkusuri, S. V. (2015). Reinforcement learning with function approximation for traffic signal control. IEEE Transactions on Intelligent Transportation Systems, 5(4), 238–245. The advantages of using predefined signal groups include a high degree of flexibility when specifying signal plans and the ability to deal with a wide range of traffic patterns in a systematic way [8]. BK has also drafted and edited the manuscript. Zhang, L., Yin, Y., & Chen, S. (2013). Balaji, P. G., German, X., & Srinivasan, D. (2010). IEEE Geoscience and Remote Sensing Letters, 12(9), 1938–1942. More details of such objective criteria are described in Section 4.4. [74] used a hybrid Petri net (HPN) model to express the problem of coordinating traffic lights with the goal of improving the performance of transit and emergency vehicles, and then developed control algorithms based on the HPN model. Fellendorf, M. (1994). NRF-2019R1F1A1058165), by Electronics and Telecommunications Research Institute (ETRI), grant funded by the Korean government (20ZD1100, Regional Industry IT Convergence Technology Development and Support Project), and by the Brain Korea 21 Plus Project for the POSTECH Educational Program for Industrial Engineers. The fixed-time strategy establishes optimal signal plans for fixed signal phase sequences with a fixed time duration for each phase. Wallace, C. E., Courage, K. G., Hadi, M. A., & Gan, A. C. (1988). Gap out terminates a phase when the time interval between consecutive activations of a vehicle detector exceeds an established threshold. Li, L., Huang, W., & Lo, H. K. (2018). Development and evaluation of a cooperative vehicle intersection control algorithm under the connected vehicles environment. The normal function of traffic lights requires more than sight control and coordination to ensure that traffic and pedestrians move as smoothly, and safely as possible. (2002). Luyanda, F., Gettman, D., Head, L., Shelby, S., Bullock, D., & Mirchandani, P. (2003). Gallivan, S., & Heydecker, B. In the UK, Slough in Berkshire had part of the A4 experimented on with this. ME collected and analyzed the data, and prepared the draft. statement and Another important concept when evaluating traffic signal systems is the throughput of the network. Transportation Research Part C: Emerging Technologies, 24, 168–189. Wong, S. C., & Yang, C. (1999). [57] verified that the minimization of queue length can lower the variance of vehicle delay in each phase. Transportation Research Procedia, 10, 207–216. Oversaturated signal systems with queue length constraints—II: Systems of intersections. Then, using Table 1, it can be determined that the paper written by Gazis in 1964 (Node 2) and the paper written by Mirchandani and Head in 2001 (Node 23) are the most important among those evaluated in this review. Transportation Research Part C: Emerging Technologies, 88, 31–51. (2001). In modern coordinated signal systems, it is possible for drivers to travel long distances without encountering a red light. Article On kinematic waves II. He, Q., Head, K. L., & Ding, J. Niittymäki, J., & Pursula, M. (2000).