过饱和状态交通信号控制方法综述_英文_李岩.docx

《过饱和状态交通信号控制方法综述_英文_李岩.docx》由会员分享，可在线阅读，更多相关《过饱和状态交通信号控制方法综述_英文_李岩.docx（11页珍藏版）》请在淘文阁 - 分享文档赚钱的网站上搜索。

1、 第 13 卷第4期 2013年 8 月 交 通 运 输 工 程 学 报 Journal of Traffic and Transportation Engineering VoL 13 NQ 4 Aug. 2013 文章编号 ： 1671-1637(2013)04-0116-11 过饱和状态交通信号控制方法综述 李岩、赵志宏 2,李鹏飞 3 4,黄身森、陈宽民 1 (1.长安火学公路学院 .陕西西安 71006.1; 2.长安火学信息工稈学院 .陕西西安 71006.1; 3.东南火学交通学院 . 江苏南京 210096; .1.阿尔伯塔火学智能交通中心 .阿尔伯塔埃德蒙顿丁 6 G2 R3

2、) 摘要：为向拥堵状态城市路网的交通控制优化提供依据，综述并评价了过饱和状态的交通信号控 制策略；分析了过饱和状态交通流的特征，提出了过饱和状态交通信号控制的对应优化原理；从单 点交叉口、协同控制交叉口及路网 3 个层次对过饱和状态交通控制方法进行了总结与评价，应用 VISSIM仿真环境评价了己有控制策略的适用性；总结了具备处理过饱和状态能力的自适应交通 信号控制系统的控制策略。仿真结果表明：过饱和状态的交通信号控制应优先优化道路空间的分 配矛盾；排队管理 策略对过饱和交通流具有较好的优化效果；建议在进行过饱和交通信号控制优化 时，结合实时交通信息，采用排队管理、关键路径通行能力最大等控制策略

3、，在交叉口群或路网层而 对交通信号控制方案进行优化。 关键词：交通信号控制；过饱和状态；控制策略；排队管理；交通仿真 中图分类号： U491. 51 文献标志码： A Review of traffic signal control methods under ove 卜 saturated conditions LI Yan1， ZHAO Zhi-hong ， LI Peng-fei.1.1， HUANG Shen-sen1 , CHEN Kuan-min1 (1. School of Highway， Changan University, Xian 710064， Shaanxi， Ch

4、ina; 2. School of Information Engineering， Changan University， Xian 710064， Shaanxi， China; 3. School of Transportation, Southeast University, Nanjing 210096, Jiangsu, China； 4. Centre for Smart Transportation, University of Alberta, Edmonton T6G2R3, Alberta, Canada) Abstract ： To provide references

5、 for traffic control optimization at congested urban road network, various traffic signal control strategies under oveisaturated conditions were reviewed and evaluated. Based on the analysis of the characteristics of over saturated traffic flow， the corresponding optimization principles of traffic s

6、ignal control under oveisaturated conditions were proposed. The traffic control strategies for isolated intersection, coordinated intersections and road network were summarized and evaluated by using VISSIM simulation environment. The control measures of adaptive traffic signal control system with t

7、he capability to deal with oveisaturated conditions were summarized. Simulation result indicates that traffic signal control strategies under oveisaturated conditions should optimize the allocation of road space in the first place. The queue management strategy has better performance on optimizing t

8、raffic signal under oversaturated conditions. It is suggested that the strategies like queue ratio maintenance and throughput maximization for critical route should be utilized with real-time traffic information for the optimization at the intersection group or road network level. 4 tabs, 7 figs, 56

9、 refs. Receipt Date： 2013-04-12 Research Projects： National Natural Science Foundation of China(51208054) ； Special Fund for Basic Scientific Research of Central Colleges (2013G1211005, CHD2011JC056) Author Resume： LI Yan(1983-) , Male, Hengshui, Hebei, Lecturer of Changan University, PhD, Research

10、on Traffic Signal Control, + 86-29-82334636 lyanchd. edu. cn. No. 4 LI Yan, et al. Review of traffic signal control methods under oveisaturated conditions 117 Key words： traffic signal control； oveisaturated condition； control strategy； queue management； traffic simulation 0 Introduction Traffic sig

11、nal control plays an evidently important role in urban transportation system management. However, the commonly used traffic control method, such as TRRL ( transport and road research laboratory) method1， HCM ( highway capacity manual ) method2 or adaptive traffic control software like SCATS (Sydney

12、coordinated adaptive traffic system )3 and SCOOT (split cycle offset optimizing technique )4 , can not work efficiently enough when the traffic demand approaches or exceeds the capacity5. The major reason that these mature traffic control strategies have low efficiency under oveisaturated conditions

13、 is that they can not respond to the primary restrictions of oveisaturated traffic system, which changes from the allocation of passing time to the spatial space limitation along road section6. Thus ， specific signal control strategies are needed for ovei saturated traffic system7. During the past 5

14、0 years, many traffic control strategies were designed for ovei saturated traffic system. The purpose of this paper is to summary and evaluate the existing traffic control strategies for oversaturated conditions, and provides a reference way to optimize traffic signal control for congested urban roa

15、d network. Traffic control strategies under oveisaturated conditions are firstly implemented for isolated intersections. Specific coordinated traffic signal control strategies for the arterial and road network are then developed for the purpose of dealing with congestion status. Beginning with disti

16、nguishing the conceptions of approaching saturation, saturation and oveisaturation, the oveisaturated traffic control strategies for various scales are summarized and evaluated. As a part of the advanced traffic management system (ATMS)8， adaptive traffic signal control systems with the capabilities

17、 of handling oveisaturated flow are also discussed. 1 Definition and characteristics of oveisaturation Traffic status is generally determined by traffic intensity, i. e. V/C(volume/capacity) ratio. For a road section, approaching saturation usually refers to the situation of V / C ratio larger than

18、0. 99 , and oveisaturation is the traffic status with V / C ratio greater than 1. 0, the saturation status has a V / C ratio exactly equals 1. 0. The conceptions of traffic conditions at intersection are similar to the conceptions at road section. If the traffic demand of one approach of the interse

19、ction exceeds its capacity, this intersection is under oveisaturated status. As shown in Fig. 1, because it is difficult to measure the actual traffic demand and capacity when the traffic system is congested, the oversaturation at signalized intersection can be defined as the condition of having an

20、approach with residual queue6. The queue information can be directly estimated by loop detectors10 , mobile sensors11 or video12 data by using shockwave theory. Fig. 1 Residual queues at intersections Traffic flow will become unstable under oversaturation or approaching saturation conditions. A smal

21、l fluctuation from any vehicle in a platoon may cause adverse consequences and reduce the efficiency of traffic system sharply. The low stability of saturated traffic flow puts forward more stringent requirements to the traffic control system. Generally, oveisaturated condition will firstly appear a

22、t one or several isolated intersections with relatively high saturation degrees. As shown in 118 Journal of Traffic and Transportation Engineering 2013 Fig. 2， when intersection B cant discharge the queue, it turns into oveisaturated status. The queue will continually grow until it exceeds the road

23、section between intersections A and B. At the moment the residual queue reach intersection A, both intersections are under the oveisaturated conditions. No effective traffic control strategy exists at this moment, but to prevent any vehicle from entering oveisaturated road section. This detrimental

24、effect is named spillback, which should be avoided in the first place. Intersections along the route with larger traffic volumes may spread the congestion much faster than other routes. Finally, the whole road network will be congested, even under a lock-out status13. It is important to implement tr

25、affic signal control strategies to prevent oveisaturated conditions in the first place, rather than to react to the issues after the fact. Once the traffic demand goes back to the normal level, the frequently used traffic control strategy will make the practitioners manage the traffic flow easily. T

26、he cause of oveisaturated status indicates that the decline of capacity caused by detrimental effects is a critical interfering factor. Therefore, the essence of traffic control strategies under ovei saturated status is to eliminate the detrimental effects by adjusting green time, cycle length and o

27、ffset. 2 Ove 广 saturated control strategies for isolated intersection 2.1 Existing traffic signal control strategy 2. 1. 1 Optimization of fixed timing Since Webster connected the average delay with the signal timing parameters and the observed variables by using cumulative diagram, these parameters

28、 can be optimized by minimizing the delay of signalized intersection (knowing as TRRL method )1. Similar to TRRL method, many optimization objectives are also applied in signal timing optimization process, such as minimizing cycle failures14 , minimizing stops15 and minimizing average saturation deg

29、ree2. However, because of the principle of algorithm, they can hardly be utilized under oveisaturated conditions. Although the coordinate transformation model16_17 and the deterministic model18 were established to estimate the delay or queue in the signalized intersection with relatively high satura

30、tion degree, the traffic signal control can do nothing but to allocate more green time to reduce the delay. 2. 1. 2 Switching of green When the green time becomes flexible, switching of green is the first and simplest traffic control strategy for the oveisaturated intersections. This strategy can al

31、locate the unused green time from un-congested phase to oveisaturated phase to ensure the elimination of residual queue. By applying this control philosophy, the total delays can be minimized by maximizing intersection productivity, while keeping the queues development within acceptable levels at th

32、e same time. A maximum green time is given to the movement with the higher saturation flow until the queue is dissipated, while other movements receive the minimum green time19. Widely used technologies of this strategy include semi/full actuated control, NEMAs ( national electrical manufactures ass

33、ociation) ring-barrier phase model in North America, and phase stage model20_23 in Europe. In the actuated control system, controller can extend or terminate the current phase to allocate the unused green to congested phase. NEMAs ring-barrier phase model extends the idea of actuated control. As ill

34、ustrated in Fig. 3, the dual ring control unit can give more priority (i. e. more green time) to traffic flow of specific intersection approach by adjusting the barriers between phases 1, 5 (3， 7) and 2， 6 (4， 8). Phase stage model can group all the un-conflicted movements and order them by No. 4 LI

35、 Yan, et al. Review of traffic signal control methods under oveisaturated conditions 119 priorities. The phase associated with critical movement group can get more green time. Fig. 3 Typical dual ring control unit of NEMA The switching of green strategy does improve the efficiency of traffic signal

36、system, especially for the situation of intersection with only one or two movements being congested. However, when the volumes of all movements exceed their capacity, these algorithms will extend all phases to maximum green time. At that time, traffic control system has no differences with fixed tim

37、e control. In general, minimizing delay via split switching is not an orrline highly responsive policy, but an optimization policy based on advanced mathematics and the detailed knowledge of demand24. 2. 1. 3 Maintaining queue ratio The nature of green adjustment police is to re-allocate the tempora

38、l resources for the purpose of improving their efficiencies. However, when the road space becomes the restriction of the system, maintaining queue ratio should be selected as the optimization object25. Under this strategy, the green time should be adjusted to balance the queues at intersections appr

39、oaches. The objective is to minimize the number of blocked intersections by managing queues of critical intersection26. This strategy involves the use of sampled loop data at each intersection0,27 or mobile sensors data11. Recent studies indicated that the signalized intersection wont maximize its c

40、apacity and minimize its delay at the same time under approaching saturated or oveisaturated conditions28. In this way, signal optimization objectives should be switched to the measures of reducing the queue length at the bottleneck and minimizing the detrimental effects under oversaturated status.

41、These optimization objectives involve the throughput maximization or the queue minimization of critical route. 2. 2 Simulation based evaluation 2. 2. 1 Simulation environment In order to evaluate the performance of traffic control strategies for oveisaturated isolated intersection, fixed timing meth

42、od (TRRL method )， Synchro method ( HCM method )， actuated control method, NEMAs dual ring control unit, phase stage model and queue ratio maintenance method are evaluated in the prevailing microscopic traffic simulation environment based on VISSIM simulation system. The advantages of VISSIM over ot

43、her simulation packages include some aspects as follows. (1) VISSIM provides the largest flexibility for users to calibrate driving behaviors and traffic conditions. (2) VISSIM is developed under .NET framework, which brings flexibility for add-on program development. (3) VISSIM provides the best to

44、ols for the development of signal control strategies, such as NEMA controller emulator, vehicle actuated programming ( VAP) language, signal control application programming interfaces ( SC APIs ), etc. VISSIM SCAPI method is used to develop signal control emulator in this research. SCAPIs are writte

45、n in C+/CLR language and the original version of SCAPIs controller requires signal control algorithms be embedded into a single dynamic link library (DLL) file. To facilitate the development, a middleware is developed, which can synchronously collect all the real-time detectors/phases states from th

46、e VISSIM network to the controller emulator then return the new desired phase states back to the VISSIM network29. At each time step, controller runs the algorithm, makes decisions according to the current state, then returns the new desired phase states to the VISSIM network. The concept of this si

47、mulation environment is illustrated as in Fig. 4. 120 Journal of Traffic and Transportation Engineering 2013 Fig. 4 Simulation environment of VISSIM 2. 2. 2 Experimental design A simple four way intersection is selected to evaluate the selected algorithms. The geometric characteristics of the inters

48、ection are shown in Fig. 5. The experimental configurations are listed in Tab. 1. All the needed data can be directly obtained from the VISSIM software. All the input parameters are optimized in advance, and then are input to the VISSIM environment. The VISSIM software has a built-in fixed time cont

49、roller to achieve TRRL method and HCM method. The Crossing software and VisVAP module in VISSIM are applied to program the actuated control method, phase stage model and queue ratio maintenance method. The VISSIM standard NEMA editor is utilized to evaluate the dual ring control unit. 4.5 4.5 T - N J _ 乂 r t 乂 卞 4.5 4.5 Fig. 5 Intersection geometry Tab. 1 Experimental traffic volumes pcu h_1 Movement Eastboun