A Review of Research on Traffic Conflicts Based on Intelligent Vehicles <s> A. RESEARCH ON TRAFFIC CONFLICT BASED ON V2V COMMUNICATION <s> This paper looks into recent developments and research trends in collision avoidance/warning systems and automation of vehicle longitudinal/lateral control tasks. It is an attempt to provide a bigger picture of the very diverse, detailed and highly multidisciplinary research in this area. Based on diversely selected research, this paper explains the initiatives for automation in different levels of transportation system with a specific emphasis on the vehicle-level automation. Human factor studies and legal issues are analyzed as well as control algorithms. Drivers' comfort and well being, increased safety, and increased highway capacity are among the most important initiatives counted for automation. However, sometimes these are contradictory requirements. Relying on an analytical survey of the published research, we will try to provide a more clear understanding of the impact of automation/warning systems on each of the above-mentioned factors. The discussion of sensory issues requires a dedicated paper due to its broad range and is not addressed in this paper. <s> BIB001 </s> A Review of Research on Traffic Conflicts Based on Intelligent Vehicles <s> A. RESEARCH ON TRAFFIC CONFLICT BASED ON V2V COMMUNICATION <s> Among Advanced Driver Assistance Systems (ADAS) pedestrian detection is a common issue due to the vulnerability of pedestrians in the event of accidents. In the present work, a novel approach for pedestrian detection based on data fusion is presented. Data fusion helps to overcome the limitations inherent to each detection system (computer vision and laser scanner) and provides accurate and trustable tracking of any pedestrian movement. The application is complemented by an efficient communication protocol, able to alert vehicles in the surroundings by a fast and reliable communication. The combination of a powerful location, based on a GPS with inertial measurement, and accurate obstacle localization based on data fusion has allowed locating the detected pedestrians with high accuracy. Tests proved the viability of the detection system and the efficiency of the communication, even at long distances. By the use of the alert communication, dangerous situations such as occlusions or misdetections can be avoided. <s> BIB002 </s> A Review of Research on Traffic Conflicts Based on Intelligent Vehicles <s> A. RESEARCH ON TRAFFIC CONFLICT BASED ON V2V COMMUNICATION <s> This paper proposes a multi-agent type-2 fuzzy logic control (FLC) method optimized by differential evolution (DE) for multi-intersection traffic signal control. Type-2 fuzzy sets can deal with models' uncertainties efficiently because of its three-dimensional membership functions, but selecting suitable parameters of membership functions and rule base is not easy. DE is adopted to decide the parameters in the type-2 fuzzy system, as it is easy to understand, simple to implement and possesses low space complexity. In order to avoid the computational complexity, the expert rule base and the parameters of membership functions (MF) are optimized by turns. An eleven-intersection traffic network is studied in which each intersection is governed by the proposed controller. A secondary layer controller is set in every intersection to select the proper phase sequence. Furthermore, the communication among the adjacent intersections is implemented using multi-agent system. Simulation experiments are designed to compare communicative type-2 FLC optimized by DE with type-1 FLC, fixed-time signal control, etc. Experimental results indicate that our proposed method can enhance the vehicular throughput rate and reduce delay, queue length and parking rate efficiently. <s> BIB003 </s> A Review of Research on Traffic Conflicts Based on Intelligent Vehicles <s> A. RESEARCH ON TRAFFIC CONFLICT BASED ON V2V COMMUNICATION <s> Vehicle to vehicle (V2V) communications allow to sharing real-time information among the vehicles that circulate on the nearby road areas. These communications systems are today in an early stage of development and the effort are focused into two directions, on one hand, the development of the communications infrastructure to support the information exchange. On the other hand, the development of Advanced Driver Assistance Systems (ADAS) as well as safety systems that takes advantages of these communications. Additionally, the V2V communications systems are mainly focused to cars and trucks, showing less concern for Vulnerable Road Users, pedestrians, motorcyclists and cyclists. In this paper a novel ADAS is presented, focused to avoid accidents that involve motorcyclist and cyclists using V2V communications, incorporating them to the vehicular networking taking into account the intrinsic features of each collective and adapting to increase their safety. <s> BIB004 </s> A Review of Research on Traffic Conflicts Based on Intelligent Vehicles <s> A. RESEARCH ON TRAFFIC CONFLICT BASED ON V2V COMMUNICATION <s> Abstract Automated driving is gaining increasing amounts of attention from both industry and academic communities because it is regarded as the most promising technology for improving road safety in the future. The ability to make an automated lane change is one of the most important parts of automated driving. However, there has been little research into automated lane change maneuvers, and current research has not identified a way to avoid potential collisions during lane changes, which result from the state variations of the other vehicles. One important reason is that the lane change vehicle cannot acquire accurate information regarding the other vehicles, especially the vehicles in the adjacent lane. However, vehicle-to-vehicle communication has the advantage of providing more information, and this information is more accurate than that obtained from other sensors, such as radars and lasers. Therefore, we propose a dynamic automated lane change maneuver based on vehicle-to-vehicle communication to accomplish an automated lane change and eliminate potential collisions during the lane change process. The key technologies for this maneuver are trajectory planning and trajectory tracking. Trajectory planning calculates a reference trajectory satisfying the demands of safety, comfort and traffic efficiency and updates it to avoid potential collisions until the lane change is complete. The trajectory planning method converts the planning problem into a constrained optimization problem using the lane change time and distance. This method is capable of planning a reference trajectory for a normal lane change, an emergency lane change and a change back to the original lane. A trajectory-tracking controller based on sliding mode control calculates the control inputs to make the host vehicle travel along the reference trajectory. Finally, simulations and experiments using a driving simulator are conducted. They demonstrate that the proposed dynamic automated lane change maneuver can avoid potential collisions during the lane change process effectively. <s> BIB005 </s> A Review of Research on Traffic Conflicts Based on Intelligent Vehicles <s> A. RESEARCH ON TRAFFIC CONFLICT BASED ON V2V COMMUNICATION <s> Connected Vehicle Technology (CVT) requires wireless data transmission between vehicles (V2V), and vehicle-to-infrastructure (V2I). Evaluating the performance of different network options for V2V and V2I communication that ensure optimal utilization of resources is a prerequisite when designing and developing robust wireless networks for CVT applications. Though dedicated short range communication (DSRC) has been considered as the primary communication option for CVT safety applications, the use of other wireless technologies (e.g., Wi-Fi, LTE, WiMAX) allow longer range communications and throughput requirements that could not be supported by DSRC alone. Further, the use of other wireless technology potentially reduces the need for costly DSRC infrastructure. In this research, the authors evaluated the performance of Het-Net consisting of Wi-Fi, DSRC and LTE technologies for V2V and V2I communications. An application layer handoff method was developed to enable Het-Net communication for two CVT applications: traffic data collection, and forward collision warning. The handoff method ensures the optimal utilization of available communication options (i.e., eliminate the need of using multiple communication options at the same time) and corresponding backhaul communication infrastructure depending on the connected vehicle application requirements. Field studies conducted in this research demonstrated that the use of Het-Net broadened the range and coverage of V2V and V2I communications. The use of the application layer handoff technique to maintain seamless connectivity for CVT applications was also successfully demonstrated and can be adopted in future Het-Net supported connected vehicle applications. A long handoff time was observed when the application switches from LTE to Wi-Fi. The delay is largely due to the time required to activate the 802.11 link and the time required for the vehicle to associate with the RSU (i.e., access point). Modifying the application to implement a soft handoff where a new network is seamlessly connected before breaking from the existing network can greatly reduce (or eliminate) the interruption of network service observed by the application. However, the use of a Het-Net did not compromise the performance of the traffic data collection application as this application does not require very low latency, unlike connected vehicle safety applications. Field tests revealed that the handoff between networks in Het-Net required several seconds (i.e., higher than 200 ms required for safety applications). Thus, Het-Net could not be used to support safety applications that require communication latency less than 200 ms. However, Het-Net could provide additional/supplementary connectivity for safety applications to warn vehicles upstream to take proactive actions to avoid problem locations. To validate and establish the findings from field tests that included a limited number of connected vehicles, ns-3 simulation experiments with a larger number of connected vehicles were conducted involving a DSRC and LTE Het-Net scenario. The latency and packet delivery error trend obtained from ns-3 simulation were found to be similar to the field experiment results. <s> BIB006 </s> A Review of Research on Traffic Conflicts Based on Intelligent Vehicles <s> A. RESEARCH ON TRAFFIC CONFLICT BASED ON V2V COMMUNICATION <s> ABSTRACT Connected vehicle communication technology is rapidly developing in recent years, and host vehicle (HV) can send or receive the basic safety message (BSM) from the remote vehicles (RVs). However, there are few applications using this information to improve the driving safety. In this paper, we propose a collision warning predicted framework that provides connected automated vehicle and alert driver when time to collision (TTC) is within specified thresholds. After pre-processor RV BSM data, this paper transforms the RV position and calculates the relative position, distance and speed. Then, the RV trajectory is estimated by using Kalman filter algorithm, and the error statistics of the prediction of latitude and longitude are analysed. The prediction results show that it works on straight, corner and the curve road, but the latitude error is higher than the longitude error. At last this paper constructs the relative position radar map for the HV, in which it can show the relative position, speed and TTC information. Vehicle collision can be detected in real time and the vehicle can prevent the potential conflict accordingly by using these information. <s> BIB007 </s> A Review of Research on Traffic Conflicts Based on Intelligent Vehicles <s> A. RESEARCH ON TRAFFIC CONFLICT BASED ON V2V COMMUNICATION <s> Abstract Variable speed limit systems are used to improve the traffic conditions on specific road stretches. This is done by adjusting the speed limits according to current traffic situations. A variable speed limit system usually consist of stationary detectors to estimate the traffic state and variable message signs at predefined locations for the application of new speed limits. Advances in vehicle technology have made it possible to use connected vehicles to improve existing variable speed limit systems. Connected vehicles can continuously transmit information about speed and location. This can be used to get more detailed information about the traffic state. By including information from connected vehicles in a variable speed limit system there is a potential to identify bottlenecks also in between stationary detectors. Further, it is possible to use direct control of the connected vehicles to adjust vehicle speeds towards the new traffic situation. In this study, we propose such a variable speed limit system based on connected vehicles. The aim is to allow for application of variable speed limits in connection with non-recurrent bottlenecks. The proposed system is evaluated with respect to traffic efficiency using microscopic traffic simulation. An incident is simulated as an example of a non-recurrent bottleneck. The traffic performance when the proposed VSL system is applied is compared to the performance without the system. The results indicate that the VSL system manage to improve traffic efficiency in a majority of the simulated cases. <s> BIB008 </s> A Review of Research on Traffic Conflicts Based on Intelligent Vehicles <s> A. RESEARCH ON TRAFFIC CONFLICT BASED ON V2V COMMUNICATION <s> In this paper, we propose a car-following model to explore the influences of V2V communication on the driving behavior at un-signalized intersections with two crossing streams and to explore how the speed guidance strategy affects the operation efficiency. The numerical results illustrate that the benefits of the guidance strategy could be enhanced by lengthening the guiding space range and increasing the maximum speed limitation, and that the guidance strategy is more suitable under low to medium traffic density and small safety interval condition. <s> BIB009
In December 2016, the US Department of Transportation issued regulations requiring automakers to install and use V2V technology on all new light vehicles. The regulation states that the industry will work together to develop standardized messaging technologies that will enhance the deployment of networked technologies across the United States. Once fully deployed, it can prevent thousands of vehicles from the threat of car accidents  . According to the 2020 framework, the European Commission plans to use V2X communication as a mandatory device for new vehicles in the short term BIB004 . The introduction of car-to-vehicle communication can exchange their own driving and road information, and achieve safer and more efficient automatic driving through mutual cooperation. In addition, the transmission of information including accidents, emergencies, and traffic jams is an important advantage of vehicle-to-vehicle communication BIB001 ,  . Traffic conflict prediction based on vehicle-vehicle communication takes advantages of the sharing information provided by the network interconnection technology. The vehicle internet and vehicle cloud network fully considers the selfdriving status and the movement trends of other vehicles to carry out conflict risk prediction. Many researchers utilize the vehicle-vehicle communication technology to carry out vehicle-vehicle conflict prediction research BIB007 -  . V2V communication technology can also provide reasonable solutions to traffic safety problems at road intersections, in which vehicle-vehicle collision avoidance warning is a typical application. Liu  proposed a V2V-based vehiclevehicle collision avoidance early warning algorithm for road intersections, which mainly includes three parts: the improved algorithm of collision detection at road intersections, the calculation of vehicle-vehicle collision detection, and the strategy of issuing warning information for collision avoidance. Active collision avoidance control of a single vehicle is always limited by the collected data. Wang  uses vehicle communication technology to enable the vehicle status information to be shared among vehicles, so that vehicles can get more information to optimize their own planning trajectory and achieve dynamic collision avoidance. V2V communication allows the vehicles to share data with other vehicles. It has the advantage of providing more road information, which is more accurate than information obtained from the on-board sensors (such as radar and laser). Luo et al. BIB005 proposed a dynamic automatic lanechanging strategy based on vehicle-to-vehicle communication to eliminate potential collisions during lane-changing and realize automatic lane-changing. Garcia et al. BIB002 proposed distributed pedestrian detection, which synthesize the detection result of all the surrounding vehicles. Bi et al. BIB003 applies V2V information to intersection management. Dey et al. BIB006 proposed the approaches of sharing vehicle status, location, and driving strategies among multiple vehicles. Grumer and Tapani BIB008 proposed a speed-varying and speed-limiting system based on V2V. The connected vehicles can exchange speed and position information. Zhao and Li BIB009 used V2V communication model to study the effect of speed guidance on vehicle following behavior at the non-signalized intersections with two kinds of conflict flows. The vehicles can find suitable clearance in the intersection, which enables to pass through intersections more effectively and smoothly by accelerating or decelerating in advance. Vehicle communication technology makes use of the wireless communication method to share the position and speed information for interacting with each other within the region. It can improve the perception ability of traditional vehicle sensors, so as to realize risk prediction and eliminate conflicts in time to avoid collisions. However, considering that the actual vehicle network is limited by transmission distance, packet loss and transmission delay, there are still some uncertainties. The main short-range wireless communication technologies used in the field of intelligent vehicles are compared in Table 2 .