A Review of Research on Traffic Conflicts Based on Intelligent Vehicles <s> B. RESEARCH ON TRAFFIC CONFLICT BASED ON V2I/V2P COMMUNICATION <s> This paper presents a decentralized merging assistant for mixed traffic situations aiming to increase traffic flow stability around the merging area by minimizing the conflict and limiting the changes in speed. The algorithm encourages early and smooth deceleration of the mainline vehicles upstream of the merging area in order to create gap for ramp vehicle. Simulation results show that the effectiveness of the merging assistant can be different depending on traffic conditions and compositions. A negative side effect that reduces the effectiveness of the proposed algorithm is found and some ideas to solve this problem are discussed. <s> BIB001 </s> A Review of Research on Traffic Conflicts Based on Intelligent Vehicles <s> B. RESEARCH ON TRAFFIC CONFLICT BASED ON V2I/V2P COMMUNICATION <s> Information from connected vehicles, such as the position and speed of individual vehicles, can be used to optimize traffic operations at an intersection. This paper proposes such an algorithm for two one-way-streets assuming that only a certain percentage of cars are equipped with this technology. The algorithm enumerates different sequences of cars discharging from the intersection to minimize the objective function. Benefits of platooning (multiple cars consecutively discharging from a queue) and signal flexibility (adaptability to demand) are also considered. The goal is to gain insights about the value (in terms of delay savings) of using connected vehicle technology for intersection control. Simulations are conducted for different total demand values and demand ratios to understand the effects of changing the minimum green time at the signal and the penetration rate of connected cars. Using autonomous vehicle control systems, the signal could rapidly change the direction of priority without relying on the reaction of drivers. However, without this technology a minimum green time is necessary. The results of the simulations show that a minimum green time increases the delay only for the low and balanced demand scenarios. Therefore, the value of using cars with autonomous vehicle control can only be seen at intersections with this kind of demand patterns, and could result in up to 7% decrease in delay. On the other hand, using information from connected vehicles to better adapt the traffic signal has proven to be indeed very valuable. Increases in the penetration rate from 0% up to 60% can significantly reduce the average delay (in low demand scenarios a decrease in delay of up to 60% can be observed). That being said, after a penetration rate of 60%, while the delays continue to decrease, the rate of reduction decreases and the marginal value of information from communication technologies diminishes. Overall, it is observed that connected vehicle technology could significantly improve the operation of traffic at signalized intersections, at least under the proposed algorithm. <s> BIB002 </s> A Review of Research on Traffic Conflicts Based on Intelligent Vehicles <s> B. RESEARCH ON TRAFFIC CONFLICT BASED ON V2I/V2P COMMUNICATION <s> Recently, researchers have proposed various autonomous intersection management techniques that enable autonomous vehicles to cross the intersection without traffic lights or stop signs. In particular, a priority-based coordination system with provable collision-free and deadlock-free features has been presented. In this paper, we extend the priority-based approach to support legacy vehicles without compromising above-mentioned features. We make the hypothesis that legacy vehicles are able to keep a safe distance from their leading vehicles. Then we explore some special configurations of system that ensures the safe crossing of legacy vehicles. We implement the extended system in a realistic traffic simulator SUMO. Simulations are performed to demonstrate the safety of the system. <s> BIB003 </s> A Review of Research on Traffic Conflicts Based on Intelligent Vehicles <s> B. RESEARCH ON TRAFFIC CONFLICT BASED ON V2I/V2P COMMUNICATION <s> Abstract Co-operative Intelligent Transportation Systems (C-ITS) are attracting a lot of attention, and many resources are devoted to the development of new platforms integrating vehicle-to-vehicle (V2 V) and vehicle-to-infrastructure (V2I) communications. The main goal of these systems is to improve safety level on the road networks through a new intelligent services available on-board supporting smarter driving. Due to the rapid growth of smartphone technology and smartphone worldwide sales, C-ITS may have a great contribution from its applications in vehicles data collection. Worldwide sales of smartphones totaled 968 million units in 2013, according to Gartner Inc., exceeding annual sales of feature phones for the first time. This study presents a new co-operative systems based on a client/server platform in which client units are GPS-enabled smartphones capable to acquire individual vehicle's kinematics to be shared on a web server for road operators and users analysis. The cooperative system allows drivers to watch detailed information about their individual driving style and global statistics on their trips. On the other hand, road operators can analyze the whole database to highlight critical points on the network (where unsafe behaviors occur more frequently) and to reward users with safer driving style. This study underscores the usefulness of the smartphone technology for improving C-ITS and assessing potential safety problems. <s> BIB004 </s> A Review of Research on Traffic Conflicts Based on Intelligent Vehicles <s> B. RESEARCH ON TRAFFIC CONFLICT BASED ON V2I/V2P COMMUNICATION <s> Abstract Traffic signals, even though crucial for safe operations of busy intersections, are one of the leading causes of travel delays in urban settings, as well as the reason why billions of gallons of fuel are burned, and tons of toxic pollutants released to the atmosphere each year by idling engines. Recent advances in cellular networks and dedicated short-range communications make Vehicle-to-Infrastructure (V2I) communications a reality, as individual cars and traffic signals can now be equipped with communication and computing devices. In this paper, we first presented an integrated simulator with V2I, a car-following model and an emission model to simulate the behavior of vehicles at signalized intersections and calculate travel delays in queues, vehicle emissions, and fuel consumption. We then present a hierarchical green driving strategy based on feedback control to smooth stop-and-go traffic in signalized networks, where signals can disseminate traffic signal information and loop detector data to connected vehicles through V2I communications. In this strategy, the control variable is an individual advisory speed limit for each equipped vehicle, which is calculated from its location, signal settings, and traffic conditions. Finally, we quantify the mobility and environment improvements of the green driving strategy with respect to market penetration rates of equipped vehicles, traffic conditions, communication characteristics, location accuracy, and the car-following model itself, both in isolated and non-isolated intersections. In particular, we demonstrate savings of around 15% in travel delays and around 8% in fuel consumption and greenhouse gas emissions. Different from many existing ecodriving strategies in signalized road networks, where vehicles’ speed profiles are totally controlled, our strategy is hierarchical, since only the speed limit is provided, and vehicles still have to follow their leaders. Such a strategy is crucial for maintaining safety with mixed vehicles. <s> BIB005 </s> A Review of Research on Traffic Conflicts Based on Intelligent Vehicles <s> B. RESEARCH ON TRAFFIC CONFLICT BASED ON V2I/V2P COMMUNICATION <s> The vision of intelligent vehicles traveling in road networks has prompted numerous concepts to control future traffic flow, one of which is the in-vehicle actuation of traffic control commands. The key of this concept is using intelligent vehicles as actuators for traffic control systems. Under this concept, we design and test a control system that connects a traffic controller with in-vehicle controllers via vehicle-to-infrastructure communication. The link-level traffic controller regulates traffic speeds through variable speed limits (VSL) gantries to resolve stop-and-go waves, while intelligent vehicles control accelerations through vehicle propulsion and brake systems to optimize their local situations. It is assumed that each intelligent vehicle receives VSL commands from the traffic controller and uses them as variable parameters for the local vehicle controller. Feasibility and effectiveness of the connected control paradigm are tested with simulation on a two-lane freeway stretch with intelligent vehicles randomly distributed among human-driven vehicles. Simulation shows that the connected VSL and vehicle control system improves traffic efficiency and sustainability; that is, total time spent in the network and average fuel consumption rate are reduced compared to (uncontrolled and controlled) scenarios with 100% human drivers and to uncontrolled scenarios with the same intelligent vehicle penetration rates. <s> BIB006 </s> A Review of Research on Traffic Conflicts Based on Intelligent Vehicles <s> B. RESEARCH ON TRAFFIC CONFLICT BASED ON V2I/V2P COMMUNICATION <s> The dedicated short-range communication/wireless access for vehicular environment together with the fourth generation-long-term evolution technologies has been widely accepted as the most promising approaches to enhance the transportation safety. As pedestrians are still protected based on the traditional honking approach, the communication-based safety alert is questionable in the practical usage. In this article, a dedicated short-range communication/long-term evolution/WiFi-based vehicular system is developed to support the vehicle-to-vehicle and vehicle-to-pedestrian communication for the safety of vehicles and pedestrians. The implementation of the heterogeneous vehicle-to-vehicle/vehicle-to-pedestrian communication module is based on an IEEE 802.11a compliant communication module, integrated with the long-term evolution module and WiFi wireless interface. A collision estimation and safety alert module on smartphone is further designed and implemented to protect pedestrians. Various performance evalu... <s> BIB007 </s> A Review of Research on Traffic Conflicts Based on Intelligent Vehicles <s> B. RESEARCH ON TRAFFIC CONFLICT BASED ON V2I/V2P COMMUNICATION <s> Cooperative localization of the connected vehicles is significant for many advanced intelligent transportation system (ITS) applications. Vehicle-to-vehicle communication using dedicated short-range communication (DSRC) has great potential to enhance global navigation satellite systems (GNSSs) for the capability of cooperative localization. In the integration of DSRC and GNSS, the tolerance against the unknown and time-varying observation conditions is a key factor to fulfill the requirements of several specific ITS applications. Under a GNSS/DSRC integrated architecture for cooperative localization, a novel robust cubature Kalman filter (CKF) is proposed in this paper to improve the performance of the data fusion under uncertain sensor observation environments. In the proposed solution, the structure of the standard CKF is enhanced using the Huber M-estimation technique, in which the original measurement update in the CKF is modified considering the probable anomalies in state estimation. Furthermore, based on the investigation of the adjustment effect from the constraint factor, an adaptive strategy for this parameter is introduced to optimize the performance comprehensively. The proposed method is validated using a specific simulation system. Results of experiment and simulations demonstrate the capability of improving the robustness and adaptive performance over the original filters under the unknown operation conditions. <s> BIB008 </s> A Review of Research on Traffic Conflicts Based on Intelligent Vehicles <s> B. RESEARCH ON TRAFFIC CONFLICT BASED ON V2I/V2P COMMUNICATION <s> Abstract This paper presents a longitudinal freeway merging control algorithm for maximizing the average travel speed of fully automated connected vehicles. Communication with a roadside unit allows the computation and transmission of optimized trajectories to the equipped vehicles. These vehicles then carry out the trajectories and resume normal operation once they cease communication with the roadside controller. A tool was developed to simulate and carry out the merging algorithm, while interfacing with the optimization software LINGO. A hypothetical merging segment was simulated to evaluate the effectiveness of the merging algorithm, and its performance is compared to conventional vehicle operation. During uncongested conditions the algorithm is able to reduce travel time, increase average travel speed and improve throughput. The capacity of the merge segment is directly related to the safe time gap selected to run the algorithm. Once capacity is reached, queuing forms on both the ramp and mainline segments upstream of the merge area. The algorithm provides safe merging operations during this congested traffic state. <s> BIB009 </s> A Review of Research on Traffic Conflicts Based on Intelligent Vehicles <s> B. RESEARCH ON TRAFFIC CONFLICT BASED ON V2I/V2P COMMUNICATION <s> A generalized framework consisting of a stochastic model, a responsive control method, and typical scenarios using vehicle-to-pedestrian (V2P) communication is proposed to improve pedestrian safety. The proposed stochastic model formulates various effects of uncertainties in a V2P communication system. The responsive control method is used to improve pedestrian safety under V2P communication conditions. Results show that adopting only Bluetooth or Wi-Fi (wireless local area network) technology, which has a high establishment time, is not sufficient for V2P communication, whereas dedicated short-range communication (DSRC) featuring low latencies meets requirements. A case study in the field was conducted to evaluate the feasibility of responsive control; it was concluded that with the use of the proposed model and the responsive control method, Bluetooth technology combined with DSRC could be workable for active pedestrian protection. <s> BIB010 </s> A Review of Research on Traffic Conflicts Based on Intelligent Vehicles <s> B. RESEARCH ON TRAFFIC CONFLICT BASED ON V2I/V2P COMMUNICATION <s> The Connected Vehicle (CV) technologies together with other Driving Assistance (DA) technologies are believed to have great effects on traffic operation and safety, and they are expected to impact the future of our cities. However, few research has estimated the exact safety benefits when all vehicles are equipped with these technologies. This paper seeks to fill the gap by using a general crash avoidance effectiveness framework for major CV&DA technologies to make a comprehensive crash reduction estimation. Twenty technologies that were tested in recent studies are summarized and sensitivity analysis is used for estimating their total crash avoidance effectiveness. The results show that crash avoidance effectiveness of CV&DA technology is significantly affected by the vehicle type and the safety estimation methodology. A 70% crash avoidance rate seems to be the highest effectiveness for the CV&DA technologies operating in the real-world environment. Based on the 2005-2008 U.S. GES Crash Records, this research found that the CV&DA technologies could lead to the reduction of light vehicles' crashes and heavy trucks' crashes by at least 32.99% and 40.88%, respectively. The rear-end crashes for both light vehicles and heavy trucks have the most expected crash benefits from the technologies. The paper also studies the effectiveness of Forward Collision Warning technology (FCW) under fog conditions, and the results show that FCW could reduce 35% of the near-crash events under fog conditions. <s> BIB011 </s> A Review of Research on Traffic Conflicts Based on Intelligent Vehicles <s> B. RESEARCH ON TRAFFIC CONFLICT BASED ON V2I/V2P COMMUNICATION <s> Abstract The future of road transportation is going to be shaped by connectivity and autonomous driving. Connected and autonomous vehicles are expected to increase safety and reduce traffic congestion. Once all the vehicles are connected and geo-localized there might still be a need to integrate a different level of autonomous vehicles on the road: from the human driven vehicle to the fully autonomous vehicle. While surrogate safety measures have been extensively considered to estimate the risk of accidents due to improper driving, there has been no attempt to use them to help drivers achieve a better driving style. This paper presents an experimentation on the idea to warn drivers when they are driving in such a way (owing to their interactions with other vehicles) that could potentially lead to an accident. In the proposed system the driver is warned of the risk of collision by the combined use of localization (GPS) gathered information and the application of road safety indicators such as Deceleration Rate to Avoid a Crash, Time To Collision and others. The experimentation involving car-following vehicles showed the feasibility, with existing technologies, of using surrogate measures of safety to assist the driver in keeping a better driving trajectory. Once connected vehicles are introduced on the market, the presented results can be a base to develop commercial smartphone applications that will allow users of "not connected" old vehicles to also take advantage of real time driving assistance for a safer use of the road. <s> BIB012 </s> A Review of Research on Traffic Conflicts Based on Intelligent Vehicles <s> B. RESEARCH ON TRAFFIC CONFLICT BASED ON V2I/V2P COMMUNICATION <s> Abstract Mobile systems applied to traffic management and control and traffic safety have the potential to shape the future of road transportation. The following innovations, that will be deployed on a large scale, could reshape road traffic management practices: ::: – the implementation of connected vehicles with global navigation satellite (GNSS) system receivers; – the autonomous car revolution; – the spreading of smartphone-based systems and the development of Mobile Cooperative Web 2.0 which is laying the base for future development of systems that will also incorporate connected and autonomous vehicles; – an increasing need for sustainability of transportation in terms of energy efficiency, traffic safety and environmental issues. This paper intends to provide a state of the art on current systems and an anticipation of how mobile systems applied to traffic management and safety could lead to a completely new transportation system in which safety and congestion issues are finally properly addressed. <s> BIB013 </s> A Review of Research on Traffic Conflicts Based on Intelligent Vehicles <s> B. RESEARCH ON TRAFFIC CONFLICT BASED ON V2I/V2P COMMUNICATION <s> Abstract Vehicle ad hoc networks (VANETs) have attracted great interests from both industry and academia, but a number of issues, particularly security, have not been readily addressed. Intrusion Detection System (IDS) as one of the most important approaches to protect network security has been studied adequately in previous literatures. However, the performance of IDSs still needs to be improved to adapt the scenario of VANETs which are very fast moving and highly dynamic. In this paper, we propose a novel IDS that is able to be appropriately used in the wireless and dynamic networks, like VANETs. It mainly contains a novel feature extraction algorithm and a classifier based on an improved growing hierarchical self-organizing map (I-GHSOM) for IDS in VANETs. The proposed feature extraction algorithm is used to quickly extract distinct features from vehicle messages for IDS’s training and test. In the proposed algorithm, two key features including the differences of traffic flow and of position are extracted. The former feature is calculated according to the range of the distance between vehicles, while both a voting filter mechanism and a semi-cooperative mechanism are designed to get the latter feature. Furthermore, in the I-GHSOM-based classifier, for quickly attaining precise classification results, two novel mechanisms (relabeling and recalculating mechanisms) are proposed to relabel the units of GHSOM and check whether the balance of GHSOM structure is broken or not. Simulation results show that the proposed IDS is better than others in the measurement of accuracy, stability, processing efficiency and message scales. <s> BIB014
With the rapid development of mobile network and Dedicated Short Range Communication (DSRC) technology in the field of intelligent vehicles, V2X-based vehicles can not only communicate with other intelligent vehicles, but also make vehicle-to-infrastructure (V2I) communication a reality. The V2I greatly reduce the congestion and improve the safety of the urban intersections [72] , BIB014 . The structure of V2I collaborative system is shown in Fig. 9 . Some researches, such as Ran and Tsao  , show that the technology of automatic driving cooperates with special lanes to reduce driving reaction time and workshop spacing, thereby improving road capacity. Pueboobpaphan et al. BIB001 shows that the system travel time can be effectively reduced by optimizing the control of vehicle speed through vehicle communication between vehicle and road facilities. Guler et al. BIB002 used V2I communication to provide a network for intersections, road signs and construction signs, in order to transmit infrastructural information such as road change, speed limit, traffic light information to intelligent vehicles. Liu et al. BIB008 used Kalman filter to couple GNSS and DSRC signals to locate the connected vehicle. Ubiergo and Jin BIB005 studied the proposed speed limit (ASL) control strategy based on vehicle-to-infrastructure communication, using V2I communication capabilities to reduce parking and delays on urban roads. In recent years, the traffic management strategy based on V2I technology for intersections not only reflects the feasibility of reality, but also is efficient. Lots of research efforts have been devoted to this field. Yue et al. BIB011 utilized dynamic message signs (DMS) to show the real-time collision risk of downstream intersections and the optimal speed of upstream, in order to reduce traffic conflicts and improve traffic capacity. Qi  established the traffic organization model of unsignalized intersection based on the location sharing of vehicle network. According to the detection and analysis of traffic conflicts, the vehicle right-of-way judgment model was established. The multi-vehicle interaction and cooperative traffic strategy of unsignalized intersection, as well as the safe traffic strategy of non-motor vehicles and pedestrians, were proposed to manage the safe traffic of intersection. Qian et al. BIB003 employed the roadside units act as intersection controllers that send messages to incoming vehicles, assign priority to them according to their current status, require trajectory information, and coordinate vehicles approaching intersections. Wang et al. BIB006 constructed a network-connected variable speed limit control system based on vehicle-road communication technology, and proposed a dynamic vehicle speed control strategy for eliminating motion waves. The results show that the control system can effectively improve road capacity. Based on the vehicle-road communication technology, Letter et al. BIB009 proposed a longitudinal synergistic merge import algorithm for expressway vehicles. Real-time vehicle communication is realized by roadside detection equipment. The results show that this method can reduce travel time, improve average travel speed and traffic volume under non-congestion conditions. At present, the smart phones have been utilized in researches with the widespread usage of smart phones. For example, Astarita and Festa BIB012 , BIB013 use smart phones to detect vehicle coordinates and speeds, evaluate the interaction between vehicles, and identify potential traffic conflicts based on smart phone-based automobile remote information technology. Astarita et al. BIB004 designed a client-side security management system for smartphones with GPS, which can obtain the instantaneous speed and acceleration data of a single vehicle to assess potential security problems. He et al. BIB010 applied stochastic model, response control method and V2P communication technology to analyze human-vehicle conflict. Based on vehicle-vehicle and human-vehicle communication, Liu et al. BIB007 designed a collision assessment and safety alarm system based on the smartphones. As one of the channels for intelligent vehicles to obtain environmental information, V2X technology provides prior information for automatic driving, improves the efficiency and accuracy of environmental recognition, and eliminates the potential safety hazards of blind spots in visual field. Some problems have been successfully solved, such as compensating for the dead angle of radar sensor and reducing the perceptual blind area. According to the current research situation, most of the studies mainly involve improving vehicle safety and guiding traffic flow. More applications focus on early warning and avoiding collisions, and alerting the drivers or intervening in active braking. However, there are few studies on the effective strategy for resolving conflicts, which is also a major direction of future research.