Safe Intelligent Driver Assistance System in V2X Communication Environments based on IoT

In the modern world, power and speed of cars have increased steadily, as traffic continued to increase. At the same time highway-related fatalities and injuries due to road incidents are constantly growing and safety problems come first. Therefore, the development of Driver Assistance Systems (DAS) has become a major issue. Numerous innovations, systems and technologies have been developed in order to improve road transportation and safety. Modern computer vision algorithms enable cars to understand the road environment with low miss rates. A number of Intelligent Transportation Systems (ITSs), Vehicle Ad-Hoc Networks (VANETs) have been applied in the different cities over the world. Recently, a new global paradigm, known as the Internet of Things (IoT) brings new idea to update the existing solutions. Vehicle-to-Infrastructure communication based on IoT technologies would be a next step in intelligent transportation for the future Internet-of-Vehicles (IoV). The overall purpose of this research was to come up with a scalable IoT solution for driver assistance, which allows to combine safety relevant information for a driver from different types of in-vehicle sensors, in-vehicle DAS, vehicle networks and driver`s gadgets. This study brushed up on the evolution and state-of-the-art of Vehicle Systems. Existing ITSs, VANETs and DASs were evaluated in the research. The study proposed a design approach for the future development of transport systems applying IoT paradigm to the transport safety applications in order to enable driver assistance become part of Internet of Vehicles (IoV). The research proposed the architecture of the Safe Intelligent DAS (SiDAS) based on IoT V2X communications in order to combine different types of data from different available devices and vehicle systems. The research proposed IoT ARM structure for SiDAS, data flow diagrams, protocols. The study proposes several IoT system structures for the vehicle-pedestrian and vehicle-vehicle collision prediction as case studies for the flexible SiDAS framework architecture. The research has demonstrated the significant increase in driver situation awareness by using IoT SiDAS, especially in NLOS conditions. Moreover, the time analysis, taking into account IoT, Cloud, LTE and DSRS latency, has been provided for different collision scenarios, in order to evaluate the overall system latency and ensure applicability for real-time driver emergency notification. Experimental results demonstrate that the proposed SiDAS improves traffic safety

ZigBee-assisted ad-hoc networking of multi-interface mobile devices

Wireless ad hoc network is decentralized wireless network, which does not rely on a preexisting infrastructure, such as routers in wired networks or access points in managed (infrastructure) wireless networks. Instead, each node participates in routing by forwarding data for other nodes. The determination of which nodes forward data is made dynamically based on the network connectivity. Node density has a great impact on the performance and efficiency of wireless ad hoc networks by influencing some factors such as capacity, network contention, routing efficiency, delay, and connectivity. On one hand, maintaining stable connectivity is a big challenge for sparsely deployed and highly dynamic ad hoc wireless network. Vehicle ad hoc network (VANET) which consists of highly mobile vehicles with wireless interfaces is one type of such network, especially in rural areas where vehicles traffic are very sparse. One of the most important applications built on top of VANET is the safety application. In VANET safety applications, source vehicles that observe accidents or some other unsafe conditions of the roads generate warning messages about the conditions, and propagate the warning messages to the following vehicles. In this way, the following drivers have the opportunity to do some necessary action before they reach the potential danger zone to avoid accident. The safety application requires timely and accurate warning message detection and delivery. However, recent researches have shown that sparse and highly dynamic vehicle traffic leads network fragmentation, which poses a crucial research challenge for VANET safety application. On the other hand, reducing contention and thus maximizing the network throughput is also a big challenge for densely deployed ad hoc wireless network, especially when many devices are located in a small area and each device has heavy duty message to transmit. The WiFi interface perhaps is the most common interface found in mobile devices for data transfer as it provides good combination of throughout, range and power efficiency. However, the WiFi interface may have to consume a large amount of bandwidth and energy for contention and combating collision, especially when mobile devices located in a small area all have heavy traffic to transmit. Meanwhile, ZigBee is an emerging wireless communication technology which supports low-cost, low-power and short-range wireless communication. Nowadays, it has been common for a mobile device, such as smart phone, PDA and laptop, to have both WiFi and Bluetooth interfaces. As the ZigBee technology becomes more and more mature, it will not be surprising to see the ZigBee interface commonly embedded in mobile devices together with WiFi and Bluetooth interfaces in the near future. The co-existence of the ZigBee and the WiFi interfaces in the same mobile device inspires us to develop new techniques to address the above two issues. Specifically, this thesis presents two systems built based on ZigBee-assisted ad-hoc networking of multi-interface mobile devices. In order to achieve stable connectivity in a sparse and dynamic VANET, the first system integrates a network of static roadside sensors and highly mobile vehicles to improve driving safety. In order to reduce contention in a densely deployed ad hoc wireless network, the second system assists WiFi transmission with ZigBee interface for multi-interface mobile devices. Extensive implementations and experiments have been conducted to demonstrate the effectiveness of our proposed systems

Inter-vehicular communication for collision avoidance using Wi-Fi Direct

Inter vehicular collision avoidance systems warn vehicle drivers of potential collisions. The U.S Department of Transportation (USDOT) National Highway Traffic Safety Administration, in February 2014 has decided to enable vehicular communication among lightweight vehicles to exchange warning messages to prevent accidents. Dedicated Short Range Communications (DSRC) is a communication standard that allows short-range communication between vehicles and infrastructure, exchanging critical safety information to avoid collision. DSRC safety applications include forward collision warning, sudden brake warning and blind spot warning among many other warnings. It is also important to exchange location information between vehicles and pedestrians to avoid accidents. To exchange safety messages using DSRC, dedicated equipment is required. Pedestrians may not benefit from DSRC, as they may not carry dedicated DSRC safety equipment with them. Wi-Fi Direct technology can be used as an alternate to DSRC to exchange safety messages. Wi-Fi Direct enabled smartphones can exchange important safety information without the need of additional equipment. Peer-to-Peer (P2P) connections are formed between Wi-Fi Direct devices to exchange safety information. The Group Owner acts as the access point through which all clients communicate. This work examines how Wi-Fi Direct can be used in vehicular environment to exchange basic safety information between smartphones of vehicle drivers. Wi-Fi Direct and DSRC transmission delays are calculated are calculated. The results show, with more devices in a Wi-Fi Direct group the congestion in the network increases due to unnecessary retransmissions through the group owner. As mitigation, a broadcast method is proposed to reduce the delay. The results illustrate that the P2P group can now accommodate more vehicles and the delay is lesser. The calculations are extended to compute the transmission delay when P2P groups of same size exchange safety messages. The results help analyse the limitations of the system

Utilizing ZigBee Technology for More Resource-efficient Wireless Networking

Wireless networks have been an essential part of communication in our daily life. Targeted at different applications, a variety of wireless networks have emerged. Due to constrained resources for wireless communications, challenges arise but are not fully addressed. Featured by low cost and low power, ZigBee technology has been developed for years. As the ZigBee technology becomes more and more mature, low-cost embedded ZigBee interfaces have been available off the shelf and their sizes are becoming smaller and smaller. It will not be surprising to see the ZigBee interface commonly embedded in mobile devices in the near future. Motivated by this trend, we propose to leverage the ZigBee technology to improve existing wireless networks. In this dissertation, we classify wireless networks into three categories (i.e., infrastructure-based, infrastructure-less and hybrid networks), and investigate each with a representative network. Practical schemes are designed with the major objective of improving resource efficiency for wireless networking through utilizing ZigBee technology. Extensive simulation and experiment results have demonstrated that network performance can be improved significantly in terms of energy efficiency, throughput, packet delivery delay, etc., by adopting our proposed schemes

Controlo de acesso ao meio em comunicações veiculares de tempo-real

Despite several preventive measures, the number of roadway accidents is still very high, being considered even a problem of public health by some entities. This thesis has as global purpose of contributing to the reduction of that number of accidents, and consequent fatalities, by using safety-related applications that use communication among vehicles. In particular, the primary goal is guaranteeing that communication between users in vehicular environments is done with appropriate time bounds to transfer safety-critical information. In detail, it is studied how to manage the scheduling of message’s transmissions (medium access control - MAC), in order to define precisely who will communicate and when is the appropriate instant. The preferable situation where a communication infrastructure is present with full coverage (RSUs) is also studied, from which medium access control is defined precisely, and vehicles (OBUs) become aware of medium utilization. Also, sporadic situations (e.g., absence of RSUs) are studied in which the communication network is “ad hoc” and solely formed by the current vehicles. It is used the recently WAVE / IEEE 802.11p standard, specific for vehicular communications, and it is proposed a TDMA based solution, with appropriate coordination between RSUs in order to effectively disseminate a critical safety event. It is taken into account two different ways of choosing the instant for the initial broadcast, and both cases are compared. In case there is no infrastructure available, methods are derived to minimize communication medium access collisions, and to maximize the available bandwidth. The results reflect the total end-to-end delay, and show that adequate times are attained, and meet with the requisites for the type of applications being considered. Also, enhancements are obtained when using the alternate choice for the initial broadcast instant.Apesar de diversas medidas preventivas, o número de acidentes rodoviários continua a ser muito elevado, sendo mesmo considerado uma questão de saúde pública por algumas entidades. Esta tese tem como objetivo geral contribuir para a redução desse número de acidentes, e consequentes fatalidades, através da utilização de aplicações de segurança que envolvem comunicação entre veículos. Em particular, o objetivo principal é garantir que a comunicação entre utentes, em ambientes veiculares, seja efetuada com limites temporais apropriados à transferência de informações críticas. De forma mais detalhada, é estudada a gestão do escalonamento das transmissões (controlo de acesso ao meio – MAC) que irá definir quem vai comunicar e quando o pode fazer. São estudadas situações (desejadas) onde há uma infra-estrutura de comunicações com cobertura integral (RSUs), a partir da qual se faz a coordenação do acesso ao meio pelos veículos (OBUs), e situações (esporádicas, por ausência de RSU) em que a rede de comunicação é “ad hoc” e apenas constituída pelos veículos presentes. Utiliza-se a recente norma WAVE / IEEE 802.11p, específica para comunicações veiculares, e propõe-se uma solução baseada em TDMA, com coordenação apropriada entre RSUs para disseminação efetiva de um evento crítico de segurança. A escolha do instante para o broadcast inicial do evento de segurança também é tida em conta, e são comparados dois casos distintos. No caso da ausência de infraestrutura, derivam-se métodos para minimizar colisões no acesso ao meio de comunicação, e maximizar a largura de banda disponível. Os resultados refletem o atraso total end-to-end, mostrando tempos apropriados para os requisitos das aplicações em causa, e evidenciando melhorias aquando da escolha alternativa para o instante do broadcast inicial.Programa Doutoral em Engenharia Eletrotécnic

ITS-technieken om verkeersveiligheid te verhogen op kruispunten met verkeerslichten (VRI’s): Onderzoek naar de mogelijkheden van dynamisch snelheidsadvies op VRI’s

This report proceeds on the report “ITS and traffic safety, Intelligent Transport Systems” (RA-MOW-2008-007) and expands on the possibilities of ITS systems for the enhancement of traffic safety around intersections equipped with traffic lights. It seems quite obvious that there is a higher risk for traffic accidents at junctions then on other road segments, since road users cross at junctions. Based on accident statistics, this report proves that enhancing safety around intersections indeed has a strong positive impact on the global traffic safety. It also introduces the use of Intelligent Transport Systems (ITS) as a mean to enhance safety around crossroads equipped with traffic lights. A detailed technical description is given of the communication techniques supporting such systems, and an extensive overview is given of the state-of-the-art in the most relevant related research projects. Accident statistics prove that an important portion of both fatal and non-fatal accidents occur at intersections. In the EU-13 this represents 5.476 casualties or 21.3% of all traffic casualties. In Belgium 19.3% of all traffic casualties are the consequence of incidents at intersections. When the absolute figures are divided per million inhabitants, Belgium has the fifth highest number of deaths at intersections in Europe (after Italy, Hungary, Estonia and Poland). This Belgian number, 20 lethal accidents per million inhabitants, is higher then the average EU-13 (18.1) and EU-16 (19) numbers. In the Intersafe project (performed within the PReVENT project) several accident scenarios where studied, and among others the percentage of intersection fatalities within the total of traffic casualties were determined for France, Great-Brittan and Germany. Junctions are responsible for 30 to 60% of the incidents with wounded, and 16 to 36% of the fatal incidents. When examining the analyses of red light negation, it can be concluded that the critical situation can be avoided if the driver is informed and warned earlier. However, it has to be guaranteed that this information and warnings do not lead to an even more dangerous risky behaviour where they are interpreted as “if I drive faster I will be able to just catch the green light”. This would create an even higher risk of serious accidents, therefore enough attention should be given to this issue. The above numbers and analyses prove that enhancing safety around intersections should be a priority in traffic policy. Extra attention should be given to preventing red light negation, since this is a major part of the dangerous traffic violations. Research focusing on accidents on intersections proved that there is a connection between the type of intersection and the degree of traffic safety on that junction. A study was found that provides a quantitative evaluation of traffic safety around different types of intersections, expressed as the number of registered incidents with wounded per million passing vehicles. This number is the highest for intersections with traffic lights (0.11), followed by junctions on a main road (0.09), junctions with right of way (0.09), roundabouts (0.07) and junctions without right of way (0.06). The average number of wounded per accident decrease in the following order: traffic lights, main road, right of way, no right of way (respectively 1.22, 1.18, 1.11, 1.09). The seriousness of accidents, expressed as the number of hospitalizations rather increases in that order (respectively 17,16,18,18). This means that rearranging intersections can be beneficial. An American study investigated what the effect would be if the junctions in North Virginia were rearranged. It was concluded that delays would be lowered with 62 to 74 % (according to junction type), meaning a reduction of 300.000 lost hours per year. The annual saving in fuel consumption would be 200.000 gallons (757.000 litres). Traffic safety would increase drastically: reforming junctions into roundabouts would result in 62 less accidents and 42 less wounded (comparison between 1993 en 2003 with five crossroads for which accident statistics were available). Therefore a logical measure to enhance traffic safety is to rearrange intersections equipped with traffic lights or to transform them into roundabouts. Other possible measures can be related to traffic lights regulation, road layout (canalization, slopes, facilities for vulnerable road users, etc), improvement of visibility, driving education, speed management around intersections, enforcement (camera’s), road surface, etc. These measures are already applied in Flanders today. But a technique that is almost entirely neglected is the employment of Intelligent Transport Systems to increase traffic safety around intersections. This approach is further elaborated in this report. When traffic control infrastructure at crossroads is extended with intelligent software and possibly sensors and means to communicate with neighbouring vehicles, applications can be developed with a positive impact on different domains. The three most important ones are traffic safety, traffic circulation and the environment. Many studies focusing on intelligent intersections aim to enhance traffic circulation. Self-organizing traffic lights divide traffic into platoons by counting (e.g. using counter loops in the road surface) the number of vehicles waiting at the traffic lights, and adjusting the switching times accordingly. This technique was applied in a traffic simulator to the Wetstraat in Brussels, where it would lower the total travel times approximately 25%. In other research a system was developed where every vehicle can vote for switching of the lights. For this it communicates it’s identity, direction, position and place in the queue to the traffic light. Using this information of all the neighbouring vehicles, the light can calculate which light switch will result into the greatest total profit for all vehicles. Results showed an enhancement in average waiting times from 30 to 50%. In the domain of positive effects on traffic safety, developments are taking place in a number of European research projects such as PReVENT, Safespot and VII. Frequent scenarios that are being tackled are avoiding of or warning for red light negation, avoiding accidents with vulnerable road users and coordination of turning left with oncoming traffic. Also, applications that aim for an enhancement in traffic circulation imply an enhancement in traffic safety. Less research can be found aiming at environmental benefits, but again applications focusing on enhancement of traffic circulation imply positive effects on the environment. A common aspect of many of these applications is the fact that they rely on communication technology. This can be divided into three major groups: local short-range communication, cellular data networks and digital broadcast technologies. When they are studied in the scope of intelligent intersection control, then both broadcast- and cellular technologies do not qualify as a possible supporting technology. This because of the one-way communication character of broadcasting, and the higher delays and end user cost of cellular data networks. This limits the choice to local communication media, more specific CEN DSRC, IEEE 802.11p, CALM-M5, CALM-IR and IEEE 802.15.4. When taking a closer look at their parameters, they indeed seem to be very suitable: they are interactive, free to use, can offer a high bandwidth and are not dependent of network operator coverage. An extensive technical description of these communication technologies is given in this report. CEN DSRC is typically used for Electronic Toll Collect (such as Télépéage in France). However it is not suitable for the implementation of intelligent traffic lights because it only supports one-way communication. IEEE 802.11p is an amendment to the well-known IEEE 802.11 Wireless LAN technology (also known under the Wi-Fi hallmark) for use in vehicular environments. This technology is also not suitable for intelligent traffic lights in Flanders since it operates on the ITS frequency bands of the US. CALM-M5 however is the European derivate of IEEE 802.11p, and this technology indeed is greatly suitable. But just like IEEE 802.11p it will suffer van scalability issues, meaning that more research regarding scalable routing protocols has to be conducted before it can be used in a real rollout. In the field of directional communication both European standards CALM-IR and CALM-MM qualify as an implementation candidate. CALM-IR is a communication standard based on infrared light, en is very good in sharply defining communication zones. CALM-MM operates on frequencies similar to radar, and can provide very high bandwidths. On short to medium term CALM-IR has the advantage that it is already much further developed then CALM-MM. IEEE 802.15.4 is a communication technology used in wireless sensor networks. Its main characteristics are energy efficiency and scalability. This technology is most suited for application in mobile devices, thus for including vulnerable road users in the intelligent intersection. However this requires that the (typically SANET) routing protocols on top of this technology support mobility. This demands further research. To conclude, on short to medium term three communication technologies qualify for the implementation of intelligent traffic lights: CALM-M5, CALM-IR and IEEE 802.15.4. CALM-M5 is suitable for omnidirectional communication with vehicles, CALM-IR for directional communication with vehicles and IEEE 802.15.4 for omnidirectional communication with vulnerable road users. Further research is needed regarding suitable routing protocols before CALM-M5 and IEEE 802.15.4 can be successfully applied in intelligent intersections. Based on these technological developments, several research projects already investigate intelligent intersections. INTERSAFE is a subproject of the PReVENT project. Goal is to inform and/or warn the driver about traffic lights; this information/warning contains information regarding the time and the proper speed to safely cross or exit the intersection. The idea is to avoid conflicts at junctions with these information/warnings. These conflicts can be caused by absent-mindedness (not noticing the traffic light or the state of the lights), by maladjusted driving behaviour in function of the expected red- or green cycle, or by an inadequate insight in the traffic lights installation. Finally, it is expected that this information/warning will stimulate the driver to adjust his driving behaviour, reducing the risk for conflicts. This adjustment of the driving behaviour mainly is related to a decrease in speed, this can be performed gradually, but can bend to severe braking if the information/warning is not taken into account on time. Two demonstration vehicles were designed for testing this technique. A visual and auditive warning was used to give speed advice. Complying with this speed implies that the intersection can be safely crossed. Demonstrations at Versailles proved that this systems works well on the test roads from a technical point of view. However, the nature of the provided information and the voluntary character of the system imply that the safety on these intelligent intersections is highly dependent of they way the driver translates the information/warning into adjusted driving behaviour. From this research project, it appears that if some specific technical enhancements are conducted, supporting driving behaviour at intersections can improve traffic safety. IRIS is a sub-project of the Safespot project. IRIS uses vehicle-infrastructure communication to analyze the movements of all individual vehicles, and laser scanners to identify vulnerable road users. Based on these inputs, the system can assess dangerous situations on time and take necessary measures to avoid accidents (such as adjusting switching times of the lights or sending warning messages to human-machine interfaces in the vehicles using wireless communication). The IRIS system focuses on three scenarios responsible for a major part of the accidents at intersections: red light negation, turning left (conflict with oncoming traffic) and turning right (conflict with vulnerable road users). In the project experiments are performed in a driving simulator. Simulation makes it possible to perform a more systematic and extensive analysis of the applications and their possible variations. Early during development simulation can be useful to study the timing of the applications, derive optimal parameter settings and assess the potential impact of the applications if validation in the real world is not possible. In parallel with the simulation work, a real IRIS system is built and tested in the project. In May 2009 a first public demonstration of this system will be given Helmond, The Netherlands. Aiming to improve traffic circulation and to reduce consumption and emissions, the project Tovergroen was set up in The Netherlands. Tovergroen is a system to detect trucks and give them priority if possible by prolonging their green phase. However, the detection system performed inadequate, not recognizing trucks or recognizing the wrong vehicles as trucks (campers, cars with trailers, etc). Despites these problems Tovergroen increases the chance that trucks do not have to stop with 5 to 10%. Tovergroen decreases red light negation of heavy traffic with approximately 30%. It is expected that the positive effect will be even greater using a more reliable detection system. In cooperation with the Technical University of Munich, Inglostadt en GEVAS software, Audi has developed Travolution. Aim is to inform drivers regarding the appropriate speed to maintain to cross the intersection without stopping. Using wireless communication, the intelligent traffic light sends the duration of the red light to the in-vehicle system. The in-vehicle system then calculates the appropriate speed to catch the green light and informs the driver. In Inglostadt 46 intersections were equipped with this system, and two test vehicles were used. In the next phase, this experiment will be extended with 20 cars and an additional 50 intersections. Goal is to investigate how the optimization of traffic light controllers in urban areas can decrease pollution and travel times. At the ITS World congress in New York, several other applications were demonstrated where information is communicated from traffic lights to vehicles. Although there is almost no information available regarding these demonstrated applications, a short description is included in this report

FRIEND: A Cyber-Physical System for Traffic Flow Related Information Aggregation and Dissemination

The major contribution of this thesis is to lay the theoretical foundations of FRIEND — A cyber-physical system for traffic Flow-Related Information aggrEgatioN and Dissemination. By integrating resources and capabilities at the nexus between the cyber and physical worlds, FRIEND will contribute to aggregating traffic flow data collected by the huge fleet of vehicles on our roads into a comprehensive, near real-time synopsis of traffic flow conditions. We anticipate providing drivers with a meaningful, color-coded, at-a-glance view of flow conditions ahead, alerting them to congested traffic. FRIEND can be used to provide accurate information about traffic flow and can be used to propagate this information. The workhorse of FRIEND is the ubiquitous lane delimiters (a.k.a. cat\u27s eyes) on our roadways that, at the moment, are used simply as dumb reflectors. Our main vision is that by endowing cat\u27s eyes with a modest power source, detection and communication capabilities they will play an important role in collecting, aggregating and disseminating traffic flow conditions to the driving public. We envision the cat\u27s eyes system to be supplemented by road-side units (RSU) deployed at regular intervals (e.g. every kilometer or so). The RSUs placed on opposite sides of the roadway constitute a logical unit and are connected by optical fiber under the median. Unlike inductive loop detectors, adjacent RSUs along the roadway are not connected with each other, thus avoiding the huge cost of optical fiber. Each RSU contains a GPS device (for time synchronization), an active Radio Frequency Identification (RFID) tag for communication with passing cars, a radio transceiver for RSU to RSU communication and a laptop-class computing device. The physical components of FRIEND collect traffic flow-related data from passing vehicles. The collected data is used by FRIEND\u27s inference engine to build beliefs about the state of the traffic, to detect traffic trends, and to disseminate relevant traffic flow-related information along the roadway. The second contribution of this thesis is the development of an incident classification and detection algorithm that can be used to classify different types of traffic incident Then, it can notify the necessary target of the incident. We also compare our incident detection technique with other VANET techniques. Our third contribution is a novel strategy for information dissemination on highways. First, we aim to prevent secondary accidents. Second, we notify drivers far away from the accident of an expected delay that gives them the option to continue or exit before reaching the incident location. A new mechanism tracks the source of the incident while notifying drivers away from the accident. The more time the incident stays, the further the information needs to be propagated. Furthermore, the denser the traffic, the faster it will backup. In high density highways, an incident may form a backup of vehicles faster than low density highways. In order to satisfy this point, we need to propagate information as a function of density and time

Advancing Intersection Management by Utilizing Cost Effective Intelligent Vehicle Concepts and Vehicle-to-Infrastructure Communication Techniques

Intelligent Transport Systems (ITS) is a growing field of research which focuses on the alleviation of traffic congestion and road accidents caused by miscommunication or confusion of human drivers. Intelligent Intersection Management is a subdivision of ITS which focuses on the seamless management of vehicles arriving at, traversing and exiting intersections to prevent congestion and collision within or around the intersection. This research sought to develop a cost effective method of implementing wireless Vehicle-to-Infrastructure (V2I) communication based Intelligent Intersection Management, by employing the use of 1:4.5 scale version autonomous vehicle prototypes, on a similarly scaled four-way intersection. This was accomplished by employing Robot Operating System (ROS) on a single board computer platform which communicated comma-separated integers via Zigbee XBee radio transceivers to prioritize navigation of vehicles arriving at the intersection based on arrival time and the vehicles’ projected paths