An efficient dynamic traffic light scheduling algorithm considering emergency vehicles for intelligent transportation systems

Traffic lights have been installed throughout road networks to control competing traffic flows at road intersections. These traffic lights are primarily intended to enhance vehicle safety while crossing road intersections, by scheduling conflicting traffic flows. However, traffic lights decrease vehicles’ efficiency over road networks. This reduction occurs because vehicles must wait for the green phase of the traffic light to pass through the intersection. The reduction in traffic efficiency becomes more severe in the presence of emergency vehicles. Emergency vehicles always take priority over all other vehicles when proceeding through any signalized road intersection, even during the red phase of the traffic light. Inexperienced or careless drivers may cause an accident if they take inappropriate action during these scenarios. In this paper, we aim to design a dynamic and efficient traffic light scheduling algorithm that adjusts the best green phase time of each traffic flow, based on the real-time traffic distribution around the signalized road intersection. This proposed algorithm has also considered the presence of emergency vehicles, allowing them to pass through the signalized intersection as soon as possible. The phases of each traffic light are set to allow any emergency vehicle approaching the signalized intersection to pass smoothly. Furthermore, scenarios in which multiple emergency vehicles approach the signalized intersection have been investigated to select the most efficient and suitable schedule. Finally, an extensive set of experiments have been utilized to evaluate the performance of the proposed algorithm.     

基于单片机的交通灯系统设计仿真

随着私家车的不断增加,传统的交通控制系统已经不能满足路口交通的需要,因此,交通控制系统正朝着智能化、低成本化方向不断发展。文章完成了以STC89C51单片机为控制核心的十字路口交通控制系统,该系统相比于传统交通系统,除了包括车辆信号灯指示模块、人行道通行指示灯模块、计时模块以外,还包括了紧急按键模块、通行时间加减模块、红外遥控模块、行人闯红灯报警模块。除了能简洁、直观地显示十字路口的通行规则,提高车辆和行人的通行效率外,系统还具有一定的可扩展性,将进一步提高十字路口的交通安全和通行效率。     

Study on Road Network Traffic Coordination Control Technique With Bus Priority

On the basis of distributed traffic control framework, fuzzy theory, and artificial neural networks technique, the road network traffic intelligent coordination control technique with bus priority was proposed. The whole road network was regarded as a large-scale system, and the subsystems were the intersections. Multiphase intelligent signal controller that controlled its own traffic and cooperated with its neighbors was installed at each intersection. By exchanging information collected from its social vehicle detectors and the bus detection and location devices, and cooperating with adjacent signal controllers, social vehicle coordination and bus priority in the whole road network were realized. Bus priority module, green observation module, and phase switch module comprised the hard core of the controller. In each module, the fuzzy rule base system was designed in detail. To improve the control system's robusticity, the fuzzy relations of the three modules were implemented by one neural network. The target of this proposed method was to maximize the possibility for vehicles to depart from the upstream intersection, and the traveling bus nearby the local intersection to pass the local intersection without stoppage while the utility efficiency of the green signal time was at a relatively high level. The actual application shows that the proposed method can decrease the average vehicle delay and average travel time effectively.     

An efficient adaptive intelligent routing system for multi‐intersections

With the rapid development of wireless technologies and the growing emphasis on vehicle safety, many vehicular ad hoc network applications have been extensively used. This study attempts to use vehicular ad hoc network technologies for autonomous driving to improve and reduce traffic congestion and vehicle waiting time. Therefore, this study proposes an adaptively intelligent routing system, which uses V2V communications to increase vehicle speed, allows vehicles to communicate with traffic control systems, arranges appropriate vehicle routes based on queuing theory, and uses traffic signals for information exchange. The timing of traffic signals is decided according to road traffic density. To decrease vehicle waiting time at intersections, every vehicle's speed is adjusted based on the distance between the vehicle and the traffic signals. In the simulation, automated vehicles and a more realistic car‐following model are taken into consideration and vehicle speeds are regulated based on speed limits and safe following distance on most roads. The simulation result reveals that our proposed adaptively intelligent routing system outperforms periodic system in average vehicle speed and average waiting time at both single and double cross intersections. Copyright © 2016 John Wiley & Sons, Ltd.     

An Arterial Green-Wave Synchronous Coordination Model for Bus and Non-bus Lanes Based on Platoon Dispersion Theory

This paper presents an arterial green-wave synchronous coordination model for bus and non-bus lanes based on platoon dispersion theory. As the traffic light at an upstream intersection change from red to green, the dispersive characteristics of these vehicles moving from upstream to the downstream were analyzed by assuming velocities of two platoon following a normal distribution pattern. The model aims at analyzing relationship between traffic flow, distance between adjacent intersections, and signaling time in order to achieve arterial green-wave synchronous coordination in both the bus and non-bus lanes. To facilitate coordination in a traffic signal control system, the number of vehicles forced to stop at the head of the platoon as well as the number of vehicles trapped at the tail of the platoon were determined and presented in a tabular form for use in the proposed traffic light coordination model. Finally, a numeric computation for the coordination of successive signals is presented to illustrate the validity of the proposed model.     

A study on traffic signal control at signalized intersections in vehicular ad hoc networks

The Seoul metropolitan government has been operating a traffic signal control system with the name of COSMOS (Cycle, Offset, Split MOdel for Seoul) since 2001. COSMOS analyzes the degrees of saturation and congestion which are calculated by installing loop detectors. At present, subterranean inductive loop detectors are generally used for detecting vehicles but their maintenance is inconvenient and costly. In addition, the estimated queue length might be influenced by errors in measuring speed, because the detectors only consider the speed of passing vehicles. Instead, we proposed a traffic signal control algorithm which enables smooth traffic flow at intersections. The proposed algorithm assigns vehicles to the group of each lane and calculates traffic volume and congestion degree using the traffic information of each group through inter-vehicle communication in Vehicular Ad-hoc Networks (VANETs). This does not require the installation of additional devices such as cameras, sensors or image processing units. In this paper, the algorithm we suggest is verified for AJWT (Average Junction Waiting Time) and TQL (Total Queue Length) under a single intersection model based on the GLD (Green Light District) simulator. The results are better than random control method and best-first control method. For a generalization of the real-time control method with VANETs, this research suggests that the technology of traffic control in signalized intersections using wireless communication will be highly useful.     

Distributed and cooperative fuzzy controllers for trafficintersections group

This paper presents a fuzzy traffic controller for a set of intersections and its simulation results. The controller of an intersection controls its own traffic and cooperates with its neighbors. It gets information from its traffic detectors and its neighbors. Using this information, the fuzzy rule base system gives optimal signals. It manages phase sequences and phase lengths adaptively to its neighbors' as well as its own traffic conditions. To carry out the performance evaluation of the controller, a simulator for intersection groups has been developed. The proposed method is compared with the vehicle actuated method which is one of the typical conventional methods. The average delay time of a vehicle is used as a performance index. The simulation results show good performance in the case of time-varying traffic patterns and heavy traffic conditions     

基于二元饱和度的信号交叉口延误分析

为提高信号交叉口通行能力,利用二元饱和度方法,对交叉口单相位的车辆做延误分析,推导了适用于任意交通情况的路口延误模型,并对该模型进行算例分析。通过基于传统饱和度与二元饱和度控制约束条件下仿真对比验证,本延误模型计算简单易实现、在较高饱和度下路口车辆排队长度比传统饱和度控制方式短,另外时延也得到一定改善。     

Traffic balancing‐based path recommendation mechanisms in vehicular networks

In this paper, we propose both reactive and proactive balancing traffic path recommendation mechanisms, which we refer to as Bal‐Traf and Abs‐Bal, respectively. Bal‐Traf is initiated when a certain output road segment located at any road intersection is detected in an overloaded situation. In the event that the existing traffic density of any output road exceeds its optimal capacity, Bal‐Traf recommends that those vehicles that plan to pass over this road segment as next hop choose another, less congested output road segment. On the other hand, Abs‐Bal is a proactive balancing traffic mechanism. Its main purpose is to distribute input traffic completely even among all output road segments at intersections. Moreover, Abs‐Bal considers the best travel time of vehicles in addition to the goal of balancing traffic. From the experimental results, we can see that Bal‐Traf eliminates the number of overwhelmed road segments over the road network in scenarios with only partial network congestion. It also decreases the number of congested road segments in scenarios with complete network congestion. However, it increases the density drastically over the remaining congested road segments in these scenarios. Abs‐Bal performs well in decreasing the percentage of congested road segments and balancing traffic among road segments located throughout the road network, in the event of complete network congestion.     

An analysis of vehicle-to-infrastructure communications for non-signalised intersection control under mixed driving behaviour

Intersection control has an important role in the management of urban traffic to ensure safety, high traffic flow and to prevent congestion. Recently, a growing body of literature has been reported on the theme of non-signalised intersection control in which traffic lights are replaced with intelligent road side units. Data from several studies suggest that non-signalised control could reduce vehicle delays and fuel consumption significantly whilst ensuring safety. However, there is little published data on the impact of the mixed driving behaviour with human-driven vehicles and autonomous vehicles. This paper investigates the emerging role of connectivity and vehicle autonomy in the context of traffic control under the mixed driving behaviour scenario. The concepts of vehicle-to-infrastructure (V2I) communications and multi-agent systems are central to achieving a robust and reliable traffic-light-free intersection control. Comprehensive computer simulation results on a four-way intersection indicate over 96% reduced average vehicle delay and 37% less fuel consumption with the non-signalised control solution compared to the traffic light control. The outcome of this study offers some important insights into enabling cooperation between vehicles and traffic infrastructure via V2I communications, in order to make more efficient real-time decisions about traffic conditions, whilst ensuring a higher degree of safety.     

Estimation of left-turning travel time at traffic intersection

Traffic guidance is a promise approach of traffic congestion alleviation, and the travel time is one of the most important basic data for the reasonable and effective route planning which is the core of traffic guidance. The traffic intersection is one of the chief components of the whole traffic road networks, so the estimation of travel time of the intersection plays an important role in traffic guidance. This paper pays more attention to the estimation of travel time for left-turning lane connected to an intersection, introduces the features for travel time estimation, and designs an estimator based on the learning vector quantity (LVQ) neural network. A suite of reasonable test shows that the method can effectively estimate the travel time of vehicles at left-turning lane with lower error to the real data.     

基于VisVAP的过饱和交叉口群自适应控制评价

为了提高交叉口群的运行效率,以改进的TACOS模型为基础,提出了适应过饱和状态下交通流动态变化的自适应控制策略。该方法以交叉口的关键路径通过最大车辆和平均排队长度最小为目标,实时优化相位放行方案,并根据最大排队长度的车流方向放行绿灯进行实时控制。利用Vissim中VisVAP模块对过饱和交叉口群自适应控制策略进行多项指标评价分析,并与定时控制相比较。结果表明,该控制方法可有效降低车辆平均等待时间和车均延误,提高通行能力。     

A novel method for tracking and counting pedestrians in real-timeusing a single camera

This paper presents a real-time system for pedestrian tracking in sequences of grayscale images acquired by a stationary camera. The objective is to integrate this system with a traffic control application such as a pedestrian control scheme at intersections. The proposed approach can also be used to detect and track humans in front of vehicles. Furthermore, the proposed schemes can be employed for the detection of several diverse traffic objects of interest (vehicles, bicycles, etc.) The system outputs the spatio-temporal coordinates of each pedestrian during the period the pedestrian is in the scene. Processing is done at three levels: raw images, blobs, and pedestrians. Blob tracking is modeled as a graph optimization problem. Pedestrians are modeled as rectangular patches with a certain dynamic behavior. Kalman filtering is used to estimate pedestrian parameters. The system was implemented on a Datacube MaxVideo 20 equipped with a Datacube Max860 and was able to achieve a peak performance of over 30 frames per second. Experimental results based on indoor and outdoor scenes demonstrated the system s robustness under many difficult situations such as partial or full occlusions of pedestrians     

基于车流量感知的交叉口车速控制策略

通过车联网(VANETs)协同控制车速和交通灯是智能交通系统的核心技术一。提出基于VANETs交通灯的车速控制优化(VSCO)方案,通过VANETs对交通信号灯进行时间优化,并对行驶经过交通信号灯的车辆进行规划,进而降低交叉口黄灯困境(YLD)相关的事故,减少CO2排放以及车辆的等待时间。实验数据表明,相比于传统的固定时间交通灯机制,VSCO方案减少了车辆等待时间和燃油排放。     

Sparsely‐deployed relay node assisted routing algorithm for vehicular ad hoc networks

In this paper, we study the issue of routing in a vehicular ad hoc network with the assistance of sparsely deployed auxiliary relay nodes at some road intersections in a city. In such a network, vehicles keep moving, and relay nodes are static. The purpose of introducing auxiliary relay nodes is to reduce the end‐to‐end packet delivery delay. We propose a sparsely deployed relay node assisted routing (SRR) algorithm, which differs from existing routing protocols on how routing decisions are made at road intersections where static relay nodes are available such that relay nodes can temporarily buffer a data packet if the packet is expected to meet a vehicle leading to a better route with high probability in certain time than the current vehicles. We further calculate the joint probability for such a case to happen on the basis of the local vehicle traffic distribution and also the turning probability at an intersection. The detailed procedure of the protocol is presented. The SRR protocol is easy to implement and requires little extra routing information. Simulation results show that SRR can achieve high performance in terms of end‐to‐end packet delivery latency and delivery ratio when compared with existing protocols. Copyright © 2013 John Wiley & Sons, Ltd.     

Bayonet-corpus: a trajectory prediction method based on bayonet context and bidirectional GRU

Predicting travel trajectory of vehicles can not only provide personalized services to users, but also have a certain effect on traffic guidance and traffic control. In this paper, we build a Bayonet-Corpus based on the context of traffic intersections, and use it to model a traffic network. Besides, Bidirectional Gated Recurrent Unit (Bi-GRU) is used to predict the sequence of traffic intersections in one single trajectory. Firstly, considering that real traffic networks are usually complex and disorder and cannot reflect the higher dimensional relationship among traffic intersections, this paper proposes a new traffic network modeling algorithm based on the context of traffic intersections: inspired by the probabilistic language model, a Bayonet-Corpus is constructed from traffic intersections in real trajectory sequence, so the high-dimensional similarity between corpus nodes can be used to measure the semantic relation of real traffic intersections. This algorithm maps vehicle trajectory nodes into a high-dimensional space vector, blocking complex structure of real traffic network and reconstructing the traffic network space. Then, the bayonets sequence in real traffic network is mapped into a matrix. Considering the trajectories sequence is bidirectional, and Bi-GRU can handle information from forward and backward simultaneously, we use Bi-GRU to bidirectionally model the trajectory matrix for the purpose of prediction.     

基于多智能体技术的城市智能交通控制系统

本文中提出一种城市交通智能控制系统,针对城市交通网络中相邻交叉口的交通流可能相互冲突,即局部交通流的优化可能引起其他区域交通状况的恶化的问题,采用多智能体协调控制方法来协调相邻交叉口处的控制信号消除网络中的交通拥塞.提出以一个智能体的方式实现一个信号灯交叉口控制,对多个信号灯交叉口形成的交通网络采用多智能体协调控制的方式实现网络流量优化来消除拥塞.文中提出由递归建模和改进的贝叶斯学习相结合的多智能体系统来使智能体可以确定其他智能体的准确模型并实时更新信息,并基于上述方法在简单的交通网络模型上建立了多智能体交通控制系统,仿真结果表明了方法的有效性,对实现智能交通系统有重要意义.     

单点自适应控制的配时方法研究

针对交通饱和期间车辆滞留的问题,提出了一种信号机单点自适应控制的配时方法。考虑到道路车辆密度、流量检测方法等因素对交通流量的影响,改进了交通流量检测方法,并对实时检测的交通流量进行补偿修正,同时结合F-B配时方法,对周期时长和绿信时间进行优化,从而加快滞留车辆的消散速度,有效地缓解车辆滞留情况。     

Intersection-Based Routing Protocol for VANETs

Vehicular ad hoc network (VANET) is an emerging wireless communications technology that is capable of enhancing driving safety and velocity by exchanging real-time transportation information. In VANETs, the carry-and-forward strategy has been adopted to overcome uneven distribution of vehicles. If the next vehicle located is in transmission range, then the vehicle forwards the packets; if not, then it carries the packets until meeting. The carry mostly occurs on sparsely populated road segments, with long carry distances having long end-to-end packet delays. Similarly, the dense condition could have long delays, due to queuing delays. The proposed intersection-based routing protocol finds a minimum delay routing path in various vehicle densities. Moreover, vehicles reroute each packet according to real-time road conditions in each intersection, and the packet routing at the intersections is dependent on the moving direction of the next vehicle. Finally, the simulation results show that the proposed Intersection-Based Routing (IBR) protocol has less end-to-end delay compared to vehicle-assisted data delivery (VADD) and greedy traffic aware routing protocol (GyTAR) protcols.     

DIR: diagonal-intersection-based routing protocol for vehicular ad hoc networks

In this paper, we present a diagonal-intersection-based routing (DIR) protocol for vehicular ad hoc networks. The DIR protocol constructs a series of diagonal intersections between the source and destination vehicles. The DIR protocol is a geographic routing protocol. Based on the geographic routing protocol, source vehicle geographically forwards data packet toward the first diagonal intersection, second diagonal intersection, and so on, until the last diagonal intersection, and finally geographically reach to the destination vehicle. For given a pair of neighboring diagonal intersections, two or more disjoint sub-paths exist between them. The novel property of DIR protocol is the auto-adjustability, while the auto-adjustability is achieved that one sub-path with low data packet delay, between two neighboring diagonal intersections, is dynamically selected to forward data packets. To reduce the data packet delay, the route is automatically re-routed by the selected sub-path with lowest delay. The proposed DIR protocol allows the mobile source and destination vehicles in the urban VANETs. Experimental results show that the DIR protocol outperforms existing solutions in terms of packet delivery ratio, data packet delay, and throughput.