Patent Publication Number: US-2022230545-A1

Title: Traffic communication system, roadside device, server, and traffic communication method

Description:
RELATED APPLICATIONS 
     The present application is a continuation based on PCT Application No. PCT/JP2020/037954, filed on Oct. 7, 2020, which claims the benefit of Japanese Patent Application No. 2019-187774, filed on Oct. 11, 2019. The content of which is incorporated by reference herein in their entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a traffic communication system, a roadside device, a server, and a traffic communication method. 
     BACKGROUND ART 
     In recent years, Intelligent Transport Systems (ITSs) have attracted attention as technology for enabling avoidance of insecurity of traffic accidents. 
     As one such system, Non-Patent Literature 1 describes a system including a roadside device corresponding to a base station installed on a roadside, and an in-vehicle device corresponding to a mobile station installed in a vehicle, the roadside device and the in-vehicle device performing wireless communication. This wireless communication may be referred to as a roadside-to-vehicle communication. 
     CITATION LIST 
     Non-Patent Literature 
     
         
         Non-Patent Literature 1: ARIB STD-T109 1.3 version “700 MHz Band Intelligent Transport System” 
       
    
     SUMMARY OF INVENTION 
     A traffic communication system according to a first aspect includes a roadside sensor configured to detect an obstacle on a road, a roadside device configured to perform wireless communication with a vehicle on the road, and a server configured to communicate with the vehicle and the roadside device via a communication network. The roadside device is configured to transmit, to the server, detection information indicating a detection result from the roadside sensor. The server is configured to transmit the detection information received from the roadside device to the vehicle via the communication network in a case that the vehicle moving on the road toward the roadside device reaches a notification start point and that the vehicle is in a first geographic range. The roadside device is configured to transmit the detection information to the vehicle by the wireless communication in a case that the vehicle moves from the first geographic range to a second geographic range located closer to the roadside device than the first geographic range. 
     A roadside device according to a second aspect is a roadside device used in a traffic communication system, the roadside device including a first communicator configured to perform wireless communication with a vehicle on a road, a second communicator configured to transmit detection information indicating a detection result from a roadside sensor for detecting an obstacle on the road, via a communication network, to a server communicating with the vehicle and the roadside device, and a controller. The controller is configured to not transmit the detection information to the vehicle by the wireless communication in a case that the vehicle moving on the road toward the roadside device reaches a notification start point and that the vehicle is in a first geographic range, and transmit the detection information to the vehicle by the wireless communication in a case that the vehicle moves from the first geographic range to a second geographic range located closer to the roadside device than the first geographic range. 
     A roadside device according to a third aspect is configured to not transmit, to a vehicle by wireless communication with the vehicle, detection information indicating a detection result from a roadside sensor for detecting an obstacle on a road in a case that a distance between the roadside device and the vehicle is a first distance, and transmit the detection information to the vehicle by the wireless communication in a case that the distance between the roadside device and the vehicle is a second distance shorter than the first distance. 
     A server according to a fourth aspect is a server used in a traffic communication system, the server including a communicator configured to communicate with a vehicle and a roadside device via a communication network, the communicator being configured to receive, from the roadside device, detection information indicating a detection result from a roadside sensor for detecting an obstacle on a road, and a controller configured to transmit the detection information received from the roadside device to the vehicle via the communication network in a case that the vehicle moving on the road toward the roadside device reaches a notification start point and that the vehicle is in a first geographic range. 
     A traffic communication method according to a fifth aspect includes detecting, by a roadside sensor, an obstacle on a road, transmitting, by a roadside device configured to perform wireless communication with a vehicle on the road, detection information indicating a detection result from the roadside sensor, via a communication network, to a server communicating with the vehicle and the roadside device, transmitting, by the server, the detection information received from the roadside device to the vehicle via the communication network in a case that the vehicle moving on the road toward the roadside device reaches a notification start point and that the vehicle is in a first geographic range, and transmitting, by the roadside device, the detection information to the vehicle by the wireless communication in a case that the vehicle moves from the first geographic range to a second geographic range located closer to the roadside device than the first geographic range. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram illustrating a configuration of a traffic communication system according to an embodiment. 
         FIG. 2  is a diagram illustrating a configuration of a roadside device according to an embodiment. 
         FIG. 3  is a diagram illustrating a configuration of a vehicle according to an embodiment. 
         FIG. 4  is a diagram illustrating a configuration of a server according to an embodiment. 
         FIG. 5  is a diagram illustrating an example of an operational environment of the traffic communication system according to an embodiment. 
         FIG. 6  is a diagram illustrating Operation Example 1 of the traffic communication system according to an embodiment. 
         FIG. 7  is a diagram illustrating Operation Example 2 of the traffic communication system according to an embodiment. 
         FIG. 8  is a diagram illustrating Operation Example 3 of the traffic communication system according to an embodiment. 
         FIG. 9  is a diagram illustrating Operation Example 4 of the traffic communication system according to an embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     On a road, an obstacle may be present that prevents passage of vehicles. A technology is available in which such an obstacle is detected by a vehicle-side sensor. However, disadvantageously, depending on road environments, the obstacle cannot be detected by the vehicle-side sensor alone, and thus occurrence of traffic accidents cannot be sufficiently suppressed. 
     Thus, the present disclosure enables occurrence of traffic accidents to be suppressed. 
     A traffic communication system according to an embodiment will be described with reference to the drawings. Note that in the following description of the drawings, the same or similar components will be denoted by the same or similar reference signs. 
     Configuration of Traffic Communication System 
     First, a configuration of a traffic communication system according to an embodiment will be described.  FIG. 1  is a diagram illustrating a configuration of a traffic communication system  1  according to an embodiment. 
     As illustrated in  FIG. 1 , the traffic communication system  1  includes vehicles  100  passing through a road  600 , and roadside devices  200  corresponding to base stations installed on the roadside of the road  600 . 
       FIG. 1  illustrates vehicles  100 A and  100 B as the vehicles  100 , and illustrates roadside devices  200 A and  200 B as the roadside devices  200 . Note that as the vehicles  100 , automobiles such as ordinary motor vehicles or light motor vehicles are illustrated but that the vehicles  100  may be any vehicles passing through the road  600  and may be, for example, motorcycles or the like. The vehicle  100  may be a self-driving vehicle. 
     Each vehicle  100  is equipped with an in-vehicle device  150  corresponding to a mobile station for performing wireless communication. The in-vehicle device  150  performs roadside-to-vehicle communication with the roadside device  200 . In  FIG. 1 , an example is illustrated in which an in-vehicle device  150 A and the roadside device  200 A perform roadside-to-vehicle communication, and an in-vehicle device  150 B and the roadside device  200 B perform roadside-to-vehicle communication. 
     Each of the roadside devices  200  may perform inter-roadside communication with the other roadside devices  200 . In  FIG. 1 , an example is illustrated in which roadside device  200 A and roadside device  200 B perform inter-roadside communication via wireless communication, but the inter-roadside communication may be wired communication. 
     In the example illustrated in  FIG. 1 , the roadside device  200 A is installed on a traffic light (traffic signal light)  300  or a support of the traffic light  300  and operates in conjunction with the traffic light  300 . For example, the roadside device  200 A transmits, to the vehicle  100  (in-vehicle device  150 ), a radio signal including signal information related to the traffic light  300 . For such roadside-to-vehicle communication, broadcast wireless communication for a large number of unspecified destinations may be used. Alternatively, for the roadside-to-vehicle communication, multicast wireless communication for a large number of specified destinations may be used, or unicast wireless communication for a single specified destination may be used. 
     Each roadside device  200  is connected to a server  400  via a communication line. The communication line may be a wired line or a wireless line. An example will be mainly described below in which the communication line between each of the roadside devices  200  and the server  400  is a wireless line, for example, a cellular communication line. The server  400  manages various types of traffic information. 
     Configuration of Roadside Device 
     Now, a configuration of the roadside device  200  according to an embodiment will be described.  FIG. 2  is a diagram illustrating the configuration of the roadside device  200  according to an embodiment. 
     As illustrated in  FIG. 2 , the roadside device  200  according to an embodiment includes a roadside-to-vehicle communicator  21 , a network communicator  22 , a controller  23 , and an interface  24 . 
     The roadside-to-vehicle communicator  21  performs wireless communication (that is, roadside-to-vehicle communication) with an in-vehicle device  150 . In other words, the roadside-to-vehicle communicator  21  corresponds to a first communicator that performs wireless communication with the vehicle  100 . 
     Specifically, the roadside-to-vehicle communicator  21  includes an antenna  21   a , and performs roadside-to-vehicle communication via the antenna  21   a . The antenna  21   a  may be a non-directional antenna, or may be a directional antenna having directivity. The roadside-to-vehicle communicator  21  converts a radio signal received by the antenna  21   a  into receive data and outputs the receive data to the controller  23 . Additionally, the roadside-to-vehicle communicator  21  converts transmit data output by the controller  23  into a radio signal and transmits the radio signal from the antenna  21   a.    
     The wireless communication scheme of the roadside-to-vehicle communicator  21  may be a scheme compliant with the T109 standard of Association of Radio Industries and Businesses (ARIB), a scheme compliant with the Vehicle-to-everything (V2X) standard of Third Generation Partnership Project (3GPP), and/or a scheme compliant with the wireless Local Area Network (LAN) standard such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 series. The roadside-to-vehicle communicator  21  may be configured to be capable of conforming to all of these communication standards. 
     The network communicator  22  communicates with a communication network  700  (not illustrated in  FIG. 2 . See  FIG. 5 ) (i.e., performs network communications). In other words, the network communicator  22  corresponds to a second communicator configured to perform network communications. An example will be described below in which the network communicator  22  performs cellular communication with a base station  701  of the communication network  700 , but the network communicator  22  may perform wired communication with the communication network  700 . 
     The network communicator  22  includes an antenna  22   a , and performs cellular communication via the antenna  22   a . The network communicator  22  converts a radio signal received by the antenna  22   a  into receive data and outputs the receive data to the controller  23 . Additionally, the network communicator  22  converts transmit data output by the controller  23  into a radio signal and transmits the radio signal from the antenna  22   a.    
     The wireless communication scheme of the network communicator  22  may be a scheme compliant with the 3GPP standard, for example, a scheme compliant with Long Term Evolution (LTE), corresponding to a fourth generation cellular communication standard, and/or a scheme compliant with New Radio (NR), corresponding to a fifth generation cellular communication standard. In a case that the wireless communication scheme of the roadside-to-vehicle communicator  21  is a scheme compliant with the V2X standard of the 3GPP, the roadside-to-vehicle communicator  21  and the network communicator  22  may be integrally configured. 
     The controller  23  controls various functions of the roadside device  200 . The controller  23  includes at least one memory  23   b  and at least one processor  23   a  electrically connected to the memory  23   b . The memory  23   b  includes a volatile memory and a non-volatile memory and stores information used for processing in the processor  23   a  and programs executed by the processor  23   a . The memory  23   b  corresponds to a storage. The processor  23   a  executes programs stored in the memory  23   b  to perform various processing. 
     The interface  24  is connected to a roadside sensor  500  via a wired line and/or a wireless line. The roadside sensor  500  may be any sensor capable of detecting an obstacle on the road  600 , but may be further connected to an image sensor (camera), millimeter wave sensor, ultrasonic sensor, and infrared sensor. The interface  24  outputs a detection result of the roadside sensor  500  to the controller  23 . The roadside sensor  500  may be integrated with the roadside device  200 . 
     Note that the interface  24  may be connected to the server  400  in a wired or wireless manner. The interface  24  may be connected to the traffic light  300  in a wired or wireless manner. 
     Configuration of Vehicle 
     Now, a configuration of the vehicle  100  according to an embodiment will be described.  FIG. 3  is a diagram illustrating a configuration of the vehicle  100  according to an embodiment. 
     As illustrated in  FIG. 3 , the vehicle  100  according to an embodiment includes a roadside-to-vehicle communicator  11 , a network communicator  12 , a GNSS receiver  13 , a notifier  14 , a drive controller  15 , an in-vehicle sensor  16 , and a controller  17 . Note that, the vehicle  100  need not include the in-vehicle sensor  16 . The roadside-to-vehicle communicator  11 , the network communicator  12 , the GNSS receiver  13 , and the controller  17  constitute the in-vehicle device  150 . 
     The roadside-to-vehicle communicator  11  performs roadside-to-vehicle communication with the roadside device  200 . In other words, the roadside-to-vehicle communicator  11  corresponds to a first communicator that performs wireless communication with the roadside device  200 . 
     Specifically, the roadside-to-vehicle communicator  11  includes an antenna  11   a , and performs roadside-to-vehicle communication via the antenna  11   a . The roadside-to-vehicle communicator  11  converts a radio signal received by the antenna  11   a  into receive data and outputs the receive data to the controller  17 . The roadside-to-vehicle communicator  11  converts the transmit data output by the controller  17  into a radio signal and transmits the radio signal from the antenna  11   a.    
     The wireless communication scheme of the roadside-to-vehicle communicator  11  may be a scheme compliant with the T109 standard of ARIB, a scheme compliant with the V2X standard of the 3GPP, and/or a scheme compliant with the wireless LAN standard such as the IEEE 802.11 series. The roadside-to-vehicle communicator  11  may be configured to be capable of conforming to all of these communication standards. 
     The network communicator  12  communicates with the communication network  700 . In an embodiment, the network communicator  12  performs cellular communication with the base station  701  of the communication network  700 . The network communicator  12  includes an antenna  12   a , and performs cellular communication via the antenna  12   a . The network communicator  12  converts a radio signal received by the antenna  12   a  into receive data and outputs the receive data to the controller  17 . Additionally, the network communicator  12  converts the transmit data output by the controller  17  into a radio signal and transmits the radio signal from the antenna  12   a.    
     The wireless communication scheme of the network communicator  12  may be a scheme compliant with the 3GPP standard, for example, a scheme compliant with LTE, corresponding to a fourth generation cellular communication standard, and/or a scheme compliant with NR, corresponding to a fifth generation cellular communication standard. In a case that the wireless communication scheme of the roadside-to-vehicle communicator  11  is a scheme compliant with the V2X standard of the 3GPP, the roadside-to-vehicle communicator  11  and the network communicator  12  may be integrally configured. 
     The GNSS receiver  13  receives a GNSS signal from a Global Navigation Satellite System (GNSS) satellite, and outputs positional information indicating the current position. The positional information includes latitude and longitude. The GNSS receiver  13  may include at least one GNSS receiver included in a GPS receiver, a Global Navigation Satellite System (GLONASS) receiver, an Indian Regional Navigational Satellite System (IRNSS) receiver, a COMPASS receiver, a Galileo receiver, and a Quasi-Zenith Satellite System (QZSS) receiver, for example. 
     Under the control of the controller  17 , the notifier  14  notifies information to a driver of the vehicle  100 . The notifier  14  includes a display  14   a  that displays information, and a speaker  14   b  that audibly outputs information. 
     The drive controller  15  controls an engine or a motor as a source of power, a power transmission mechanism, brakes, and the like. In a case where the vehicle  100  is a self-driving vehicle, the drive controller  15  may perform self-driving control of the vehicle  100  in cooperation with the controller  17 . 
     The in-vehicle sensor  16  may be any sensor capable of detecting an obstacle on the road  600  ahead in a travel direction of the vehicle  100 , but includes at least one of an image sensor (camera), a millimeter wave sensor, an ultrasonic sensor, and an infrared sensor, for example. A detection result of the in-vehicle sensor  16  may be used for self-driving control of the vehicle  100 . 
     The controller  17  controls various functions of the vehicle  100  (in-vehicle device  150 ). The controller  17  includes at least one memory  17   b  and at least one processor  17   a  electrically connected to the memory  17   b . The memory  17   b  includes a volatile memory and a non-volatile memory and stores information used for processing in the processor  17   a  and programs executed by the processor  17   a . The processor  17   a  executes programs stored in the memory  17   b  to perform various processing. 
     Configuration of Server 
     Now, a configuration of the server  400  according to an embodiment will be described.  FIG. 4  illustrates the configuration of the server  400  according to an embodiment. 
     As illustrated in  FIG. 4 , the server  400  according to an embodiment includes a network communicator  41  and a controller  42 . 
     The network communicator  41  communicates via the communication network  700 . In an embodiment, the network communicator  41  communicates with the vehicle  100  and the roadside device  200  via the communication network  700 . 
     The controller  42  controls various functions of the server  400 . The controller  42  includes at least one memory  42   b  and at least one processor  42   a  electrically connected to the memory  42   b . The memory  42   b  includes a volatile memory and a non-volatile memory and stores information used for processing in the processor  42   a  and programs executed by the processor  42   a . The memory  42   b  corresponds to a storage. The processor  42   a  executes programs stored in the memory  42   b  to perform various processing. 
     Operations of Traffic Communication System 
     Now, operations of the traffic communication system  1  according to an embodiment will be described.  FIG. 5  is a diagram illustrating an example of operational environments of the traffic communication system  1  according to an embodiment. 
     As illustrated in  FIG. 5 , the vehicle  100  travels on the road  600 . In the example illustrated in  FIG. 5 , the vehicle  100  is a self-driving vehicle, specifically a self-driving bus. The vehicle  100  performs self-driving (autonomous traveling) using the in-vehicle sensor  16  of the subject vehicle. The road  600  may be an exclusive bus road used by self-driving buses. 
     Also, the vehicle  100  utilizes information from traffic infrastructures for self-driving. In the example illustrated in  FIG. 5 , the road  600  includes a left-hand curve as viewed from the vehicle  100 . It is difficult for the in-vehicle sensor  16  of the vehicle  100  to detect the condition beyond such a curve. 
     An obstacle  601  may be present on the road  600  beyond the curve. The obstacle  601  refers to an object that prevents passage of a vehicle, and the type of obstacle  601  is, for example, a pedestrian, a fallen object, a disabled vehicle, a road damage (for example, a hole), or the like. 
     In response to detecting the obstacle  601  on the road  600  ahead in the travel direction, the vehicle  100  decelerates to avoid a collision with the obstacle  601  and stops in front of the obstacle  601 . For such an operation, in a case that the vehicle  100  is driven, for example, at a speed of 60 km/h, the obstacle  601  located 100 m ahead needs to be detected. However, it is difficult for the vehicle  100  to detect the condition beyond the curve by using the in-vehicle sensor  16 . 
     In an embodiment, to notify vehicle  100  of the condition beyond the curve, the roadside device  200  connected to the roadside sensor  500  is installed short of the curve. The roadside device  200  transmits, to the vehicle  100  by roadside-to-vehicle communication, detection information indicating a detection result from the roadside sensor  500 . Thus, the vehicle  100  can detect the obstacle  601 , that is difficult to detect by the in-vehicle sensor  16 , with the assistance of the roadside device  200 . 
     The detection information may include any information indicating the detection result from roadside sensor  500 , but includes at least one of information indicating the presence or absence of obstacle  601 , information indicating the position of the obstacle  601 , information indicating the movement speed of the obstacle  601 , information indicating the movement direction of the obstacle  601 , and information indicating the type of the obstacle  601 , for example. 
     The roadside-to-vehicle communication involves only a short delay from the detection of the obstacle  601  by the roadside device  200  until the reception of detection information by the vehicle  100 , but has the disadvantage of providing only a narrow communicable range. Thus, it is difficult to transmit the detection information to the vehicle  100  located far from the roadside device  200 . 
     For compensation for such a disadvantage, the detection information is enabled to be transmitted from the server  400  to the vehicle  100  via the communication network  700 . By utilizing such network communication, the detection information can be transmitted to the vehicle  100  located far from the roadside device  200 . However, compared to roadside-to-vehicle communication, network communication involves a longer delay from the detection of the obstacle  601  by the roadside device  200  until the reception of the detection information by the vehicle  100 . 
     An operation of notifying the vehicle  100  of the detection information by network communication and an operation of notifying the vehicle  100  of the detection information via roadside-to-vehicle communication may be constantly performed, but the constant performance of the operations poses a problem in terms of effective use of the processing resources and the radio resources. 
     Thus, in an embodiment, depending on the distance between the vehicle  100  and the roadside device  200 , switching is performed between the operation of notifying the vehicle  100  of the detection information via network communication and the operation of notifying the vehicle  100  of the detection information by the roadside-to-vehicle communication. In other words, the network communication and the roadside-to-vehicle communication are selectively used to notify the vehicle  100  of the detection information. 
     Specifically, the traffic communication system  1  according to an embodiment includes the roadside sensor  500  for detecting the obstacle  601  on the road  600 , the roadside device  200  that performs wireless communication with the vehicle  100  on the road  600 , and the server  400  that communicates with the vehicle  100  and the roadside device  200  via the communication network  700 . The roadside device  200  transmits, to server  400 , the detection information indicating the detection result from roadside sensor  500 . In a case that the distance between the vehicle  100  and the roadside device  200  is a first distance, the server  400  transmits the detection information received from the roadside device  200  to the vehicle  100  via the communication network  700 . In a case that the distance between the vehicle  100  and the roadside device  200  is a second distance that is shorter than the first distance, the roadside device  200  transmits the detection information to the vehicle  100  by wireless communication (roadside-to-vehicle communication). 
     In this regard, the first distance may be a distance that disables wireless communication with the roadside device  200 , and the second distance may be a distance that enables wireless communication with the roadside device  200  (e.g., the reach of radio waves from the roadside device  200 ). Hereinafter, for convenience of description, the first distance is referred to as the “long distance”, and the second distance is referred to as “short distance”. 
     According to an embodiment, by switching between the operation of notifying the vehicle  100  of the detection information by the network communication and the operation of notifying the vehicle  100  of the detection information by the roadside-to-vehicle communication, the occurrence of traffic accidents can be suppressed with the processing resources and the radio resources effectively utilized. 
     Note that when the vehicle  100  arrives at a notification start point on the road  600 , the server  400  initiates the operation of notifying the vehicle  100  of the detection information by the network communication. The server  400  may determine the movement speed of the vehicle  100  and adjust the position of the notification start point based on the movement speed determined. For example, in a case that the movement speed of the vehicle  100  is higher than a reference speed, the server  400  configures the notification start point located short of the reference point (i.e., a side farther from the roadside device  200 ). On the other hand, in a case that the movement speed of the vehicle  100  is lower than the reference speed, the server  400  configures the notification start point located beyond the reference point (i.e., a side closer to roadside device  200 ). 
     Thus, in the traffic communication system  1  according to an embodiment, in a case that the vehicle  100  moving on the road  600  toward the roadside device  200  reaches the notification start point, and that the vehicle  100  is in a first geographic range (a notification target range of the server  400 ), the server  400  transmits the detection information received from the roadside device  200  to the vehicle  100  via the communication network  700 . 
     On the other hand, in a case that the vehicle  100  moves from the first geographic range to a second geographic range (a notification target range of the roadside device  200 ) located further on the roadside device  200  side than the first geographic range, the roadside device  200  transmits the detection information to the vehicle  100  by the wireless communication. In this regard, the second geographic range may be a communicable range enabling wireless communication with the roadside device. 
     Note that when the vehicle  100  is in the second geographic range (the notification target range of the roadside device  200 ), the server  400  does not transmit the detection information from the server  400  to the vehicle  100 . Additionally, when the vehicle  100  is in the first geographic range (the notification target range of the server  400 ), the roadside device  200  does not transmit the detection information from the roadside device  200  to the vehicle  100 . This allows the detection information to be notified to the roadside device  200  while saving the radio resources. 
     Note that the server  400  may be an edge server in edge computing. The edge server is deployed, for example, in association with an area corresponding to each of pre-defined zones, and configured to manage the geographic range described above. One or a plurality of geographic ranges may be present within the area. 
     Hereinafter, the first distance (long distance) described above may be interpreted as the first geographic range (the notification target range of the server  400 ). The second distance (short distance) described above may be interpreted as the second geographic range (the notification target range of the roadside device  200 ). 
     As an example, when the roadside device  200 A detects the obstacle  601 , the roadside device  200 A transmits the detection information of the roadside device  200 A to the vehicle  100  present in the first geographic range corresponding to roadside device  200 A (here, referred to as the first geographic range A). Additionally, when the roadside device  200 B detects the obstacle  601 , the roadside device  200 B transmits the detection information of the roadside device  200 B to the vehicle  100  present in the first geographic range corresponding to roadside device  200 B (here, referred to as first geographic range B). The first geographic range A and the first geographic range B may be managed by a single server  400 . 
     As another example, when roadside device  200 A detects the obstacle  601 , the roadside device  200 A transmits the detection information of the roadside device  200 A to the vehicle  100  present in the first geographic range corresponding to roadside device  200 A (here, referred to as the first geographic range C). Additionally, when the roadside device  200 B detects the obstacle  601 , the roadside device  200 B transmits the detection information of the roadside device  200 B to the vehicle  100  present in the first geographic range corresponding to roadside device  200 B (here, referred to as the same first geographic range C). The first geographic range C may be managed by the server  400 . 
     (1) Operation Example 1 
     Now, Operation Example 1 of the traffic communication system  1  according to an embodiment will be described. In Operation Example 1, it is assumed that the vehicle  100  periodically notifies the server  400  of the positional information from the network communicator  12  and that the vehicle  100  periodically transmits (e.g., broadcasts) vehicle related information from the roadside-to-vehicle communicator  11 . 
       FIG. 6  is a diagram illustrating Operation Example 1 of the traffic communication system  1  according to an embodiment. 
     As illustrated in  FIG. 6 , in step S 101 , the controller  23  of the roadside device  200  detects the obstacle  601  based on the detection result from the roadside sensor  500 . The controller  23  of the roadside device  200  may generate the detection information only during the period in which the obstacle  601  is detected, or may generate the detection information regardless of whether the obstacle  601  is detected. 
     In step S 102 , the controller  23  of the roadside device  200  controls the network communicator  22  to transmit the detection information to the server  400 . The controller  23  of the roadside device  200  may periodically notify the server  400  of the detection information. The network communicator  41  of the server  400  receives the detection information from the roadside device  200 . 
     In step S 103 , the controller  17  of the vehicle  100  generates positional information by using the GNSS receiver  13 , and controls the network communicator  12  to transmit the positional information to the server  400 . The controller  17  of the vehicle  100  may periodically notify the server  400  of the latest positional information. The network communicator  41  of the server  400  receives the positional information from the vehicle  100 . 
     In step S 104 , the controller  42  of the server  400  determines the distance between the vehicle  100  and the roadside device  200  based on the positional information from the vehicle  100 . The controller  42  of the server  400  stores the installation position of the roadside device  200  in advance, and can calculate the distance from the current position of the vehicle  100  and the installation position of the roadside device  200 . The detection information received in step S 102  may include the installation position of roadside device  200 , and the controller  42  of server  400  may use the installation position to calculate the distance from the current position of vehicle  100  and the installation position of roadside device  200 . Then, the controller  42  of the server  400  determines whether the vehicle  100  is in the notification target range (long distance) of the server  400  based on the determined distance. 
     The distance may be calculated from the current position of the vehicle  100  and the installation position of the roadside sensor  500 , or may be calculated from the current position of the vehicle  100  and the position of the obstacle  601 . 
     The network communicator  41  of the server  400  may receive the detection information including the detection result from the roadside sensor  500  and the installation position of the roadside sensor  500 , by using any means (for example, input from a traffic center) including but not limited to the roadside device  200 . The controller  42  of the server  400  may calculate the distance from the current position of the vehicle  100  and the installation position of the roadside sensor  500 . 
     In step S 105 , in a case that the controller  42  of the server  400  determines that the vehicle  100  is in the notification target range (long distance) of the server  400 , the controller  42  controls the network communicator  41  to transmit the detection information received from the roadside device  200  to the vehicle  100  via the communication network  700 . 
     The network communicator  12  of the vehicle  100  receives the detection information from the server  400 . The controller  17  of the vehicle  100  may perform self-driving control by using the detection information from the server  400  instead of the detection result from the in-vehicle sensor  16 . The controller  17  of the vehicle  100  may use the detection information from the server  400  in combination with the detection result from the in-vehicle sensor  16  to perform self-driving control. 
     Subsequently, in step S 106 , the controller  17  of the vehicle  100  controls the roadside-to-vehicle communicator  11  to transmit vehicle related information. 
     The vehicle related information may be any information as long as the information is related to the vehicle  100 , but includes at least one of information indicating the position of the vehicle  100 , information indicating the movement speed of the vehicle  100 , information indicating the movement direction of the vehicle  100 , and information indicating the type of the vehicle  100 , for example. 
     The roadside-to-vehicle communicator  21  of the roadside device  200  receives vehicle related information from the vehicle  100 . In a case that the roadside-to-vehicle communicator  21  receives vehicle related information from the vehicle  100 , the controller  23  of the roadside device  200  determines that the vehicle  100  is in the notification target range (short distance) of the roadside device  200  (step S 107 ). 
     In step S 108 , in a case that it is determined that the vehicle  100  is in the notification target range (short distance) of the roadside device  200 , the controller  23  of the roadside device  200  controls the roadside-to-vehicle communicator  11  to transmit the detection information to the vehicle  100 . This transmission is performed by broadcast, multicast, or unicast. 
     The roadside-to-vehicle communicator  11  of the vehicle  100  receives the detection information from the roadside device  200 . The controller  17  of the vehicle  100  may perform self-driving control using the detection information from the roadside device  200  in place of the detection result from the in-vehicle sensor  16 . The controller  17  of the vehicle  100  may use the detection information from the roadside device  200  in combination with the detection result from the in-vehicle sensor  16  to perform self-driving control. 
     (2) Operation Example 2 
     Now, Operation Example 2 of the traffic communication system  1  according to an embodiment will be described focusing on differences from Operation Example 1. In Operation Example 2, as is the case with Operation Example 1, it is assumed that the vehicle  100  periodically notifies the server  400  of the positional information from the network communicator  12 . Note that, in Operation Example 2, the vehicle  100  need not periodically transmit the vehicle related information from the roadside-to-vehicle communicator  11 . 
       FIG. 7  is a diagram illustrating Operation Example 2 of the traffic communication system  1  according to an embodiment. 
     As illustrated in  FIG. 7 , operations in steps S 201  to S 205  are similar to the operations in steps S 101  to S 105 . 
     In step S 206 , the controller  17  of the vehicle  100  generates positional information by using the GNSS receiver  13 , and controls the network communicator  12  to transmit the positional information to the server  400 . The network communicator  41  of the server  400  receives the positional information from the vehicle  100 . 
     In step S 207 , the controller  42  of the server  400  determines the distance between the vehicle  100  and the roadside device  200  based on the positional information from the vehicle  100 . Then, the controller  42  of the server  400  determines whether the vehicle  100  is in the notification target range (long distance) of the server  400  or is in the notification target range (short distance) of the roadside device  200  based on the determined distance. 
     In step S 208 , in response to determining that the vehicle  100  is in the notification target range (short distance) of the roadside device  200 , the controller  42  of the server  400  controls the network communicator  41  to transmit the corresponding notification to the roadside device  200  via the communication network  700 . This notification can be considered as a request for transmission of the detection information. The network communicator  22  of the roadside device  200  receives the notification from the server  400 . 
     In step S 209 , in response to receiving the notification from the server  400 , the controller  23  of the roadside device  200  controls the roadside-to-vehicle communicator  11  to transmit the detection information to the vehicle  100 . This transmission is performed by broadcast, multicast, or unicast. 
     The roadside-to-vehicle communicator  11  of the vehicle  100  receives the detection information from the roadside device  200 . The controller  17  of the vehicle  100  may perform self-driving control using the detection information from the roadside device  200  in place of the detection result from the in-vehicle sensor  16 . The controller  17  of the vehicle  100  may use the detection information from the roadside device  200  in combination with the detection result from the in-vehicle sensor  16  to perform self-driving control. 
     (3) Operation Example 3 
     Now, Operation Example 3 of the traffic communication system  1  according to an embodiment will be described focusing on differences from Operation Examples 1 and 2. In Operation Example 3, as is the case with Operation Example 1, it is assumed that the vehicle  100  periodically notifies the server  400  of the positional information from the network communicator  12 , and that the vehicle  100  periodically transmits (e.g., broadcasts) the vehicle related information from the roadside-to-vehicle communicator  11 . 
       FIG. 8  is a diagram illustrating Operation Example 3 of the traffic communication system  1  according to an embodiment. 
     As illustrated in  FIG. 8 , in step S 301 , the controller  23  of the roadside device  200  detects the obstacle  601  based on the detection result from the roadside sensor  500 . The controller  23  of the roadside device  200  may generate the detection information only during the period in which the obstacle  601  is detected, or may generate the detection information regardless of whether the obstacle  601  is detected. 
     In step S 302 , the controller  17  of the vehicle  100  generates positional information by using the GNSS receiver  13 , and controls the network communicator  12  to transmit the positional information to the server  400 . The controller  17  of the vehicle  100  may periodically notify the server  400  of the latest positional information. The network communicator  41  of the server  400  receives the positional information from the vehicle  100 . 
     In step S 303 , the controller  42  of the server  400  controls the network communicator  41  to transfer the positional information from the vehicle  100  to the roadside device  200 . The network communicator  22  of the roadside device  200  receives the positional information from the server  400 . 
     In step S 304 , the controller  23  of the roadside device  200  determines the distance between the vehicle  100  and the roadside device  200  based on the positional information from the server  400 . The controller  23  of the roadside device  200  stores the installation position of the roadside device  200  in advance, and can calculate the distance from the current position of the vehicle  100  and the installation position of the roadside device  200 . Then, based on the determined distance, the controller  23  of the roadside device  200  determines whether the vehicle  100  is in the notification target range (long distance) of the server  400  or is in the notification target range (short distance) of the roadside device  200 . 
     In step S 305 , in response to determining that the vehicle  100  is in the notification target range (long distance) of the server  400 , the controller  23  of the roadside device  200  controls the network communicator  22  to transmit the detection information to the server  400 . The network communicator  41  of the server  400  receives the detection information. 
     In step S 306 , the controller  42  of the server  400  controls the network communicator  41  to transfer the detection information from the roadside device  200  to the vehicle  100 . The network communicator  12  of the vehicle  100  receives the detection information from the server  400 . The controller  17  of the vehicle  100  may perform self-driving control by using the detection information from the server  400  instead of the detection result from the in-vehicle sensor  16 . The controller  17  of the vehicle  100  may use the detection information from the server  400  in combination with the detection result from the in-vehicle sensor  16  to perform self-driving control. 
     Operations in steps S 307  to S 309  are similar to the operations in steps S 106  to S 108  of Operation Example 1. 
     (4) Operation Example 4 
     Now, Operation Example 4 of the traffic communication system  1  according to an embodiment will be described focusing on differences from Operation Examples 1 to 3. In Operation Example 4, as is the case with Operation Example 2, it is assumed that the vehicle  100  periodically notifies the server  400  of the positional information from the network communicator  12  but that the vehicle  100  need not periodically transmit the vehicle related information from the roadside-to-vehicle communicator  11 . 
       FIG. 9  is a diagram illustrating Operation Example 4 of the traffic communication system  1  according to an embodiment. 
     As illustrated in  FIG. 9 , operations in steps S 401  to S 406  are similar to the operations in steps S 301  to S 306  of Operation Example 3. 
     In step S 407 , the controller  17  of the vehicle  100  generates positional information by using the GNSS receiver  13 , and controls the network communicator  12  to transmit the positional information to the server  400 . The controller  17  of the vehicle  100  may periodically notify the server  400  of the latest positional information. The network communicator  41  of the server  400  receives the positional information from the vehicle  100 . 
     In step S 408 , the controller  42  of the server  400  controls the network communicator  41  to transfer the positional information from the vehicle  100  to the roadside device  200 . The network communicator  22  of the roadside device  200  receives the positional information from the server  400 . 
     In step S 409 , the controller  23  of the roadside device  200  determines the distance between the vehicle  100  and the roadside device  200  based on the positional information from the server  400 . Then, based on the determined distance, the controller  23  of the roadside device  200  determines whether the vehicle  100  is in the notification target range (long distance) of the server  400  or is in the notification target range (short distance) of the roadside device  200 . 
     In step S 410 , in a case that the controller  23  of the roadside device  200  determines that the vehicle  100  is in the notification target range (short distance) of the roadside device  200 , the controller  23  of the roadside device  200  controls the roadside-to-vehicle communicator  11  to transmit the detection information to the vehicle  100 . This transmission is performed by broadcast, multicast, or unicast. 
     The roadside-to-vehicle communicator  11  of the vehicle  100  receives the detection information from the roadside device  200 . The controller  17  of the vehicle  100  may perform self-driving control using the detection information from the roadside device  200  in place of the detection result from the in-vehicle sensor  16 . The controller  17  of the vehicle  100  may use the detection information from the roadside device  200  in combination with the detection result from the in-vehicle sensor  16  to perform self-driving control. 
     OTHER EMBODIMENTS 
     A program may be provided that causes a computer to execute each of the processing operations performed by the in-vehicle device  150 , the roadside device  200 , or the server  400 . The program may be recorded in a computer readable medium. Use of a computer readable medium enables the program to be installed on a computer. Here, the computer readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM, a DVD-ROM, or the like. 
     Additionally, circuits for executing processing operations performed by the in-vehicle device  150 , the roadside device  200 , or the server  400  may be integrated to configure at least a portion of the in-vehicle device  150 , the roadside device  200 , or the server  400  as a semiconductor integrated circuit (chip set, SoC). 
     Embodiments have been described above in detail with reference to the drawings, but specific configurations are not limited to those described above, and various design modifications can be made without departing from the gist of the present disclosure.