Patent Publication Number: US-8538627-B2

Title: Vehicular communication system, vehicular information collecting system, and vehicular communication program

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority of Japanese Application No. 2008-313034, filed Dec. 9, 2008, the entire specification, claims and drawings of which are incorporated herewith by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a vehicular communication system mounted in a vehicle and the like. 
     2. Description of the Related Art 
     There has been disclosed an art configured to collect information related to a designated area from a vehicle. There has also been disclosed an art which makes a vehicle recognize an area where the vehicle is located and transmits to the vehicle the information related to the area at a predefined frequency (refer to Japanese Patent Laid-open No. H10-124797). 
     Further, there has been disclosed an art which determines a vehicle scheduled to pass through an information collecting area and transmits an information collecting command to the vehicle (refer to Japanese Patent Laid-open No. 2006-221537). 
     Furthermore, there has been disclosed an art which specifies a vehicle in an information collecting zone and collects a probe information from the vehicle (refer to Japanese Patent Laid-open No. 2005-266926). 
     However, none of the above-mentioned arts can collect information related to a designated area from an appropriate vehicle when the information is immediately needed. 
     SUMMARY OF THE INVENTION 
     The present invention has been accomplished in view of the aforementioned problems, and it is therefore an object of the present invention to provide a vehicular communication system and the like capable of collecting information related to a designated area from an appropriate vehicle in real time. 
     To accomplish an object described above, there is provided in the present invention a vehicular communication system mounted in a vehicle comprising: a vehicular receiving element configured to receive a multicast tagged with information of a designated area; a communication controlling element configured to collect information denoting a state of the vehicle as a probe information from an output signal of a sensor mounted in the vehicle; a vehicular transmitting element configured to transmit the probe information collected by the communication controlling element to a server; and a position determining element configured to determine a present position of the vehicle, wherein the communication controlling element is configured to transmit the probe information to the vehicular transmitting element on condition that the present position of the vehicle determined by the position determining element is located in the designated area. 
     According to the vehicular communication system of the present invention, the probe information is sent to the server from a vehicle among an arbitrary number of vehicles whose present position is located in the designated area whose information is included in a multicast received by the vehicle. According thereto, the information related to the designated area can be collected in real time from an appropriate vehicle as the probe information. 
     It is acceptable that the communication controlling element is configured to collect information denoting a part of or the entire part of a link where the vehicle traveled and a movement cost thereof, an activity log of an environment accommodation device operated in compliance with an ambient weather or temperature of the vehicle, and an activity log of a steering device or a braking device mounted in the vehicle as the probe information. 
     According to the vehicular communication system of the mentioned configuration, the information denoting the travel log or the like of the vehicle in the designated area can be collected in real time from an appropriate vehicle as the probe information. The movement cost denotes time, energy (consumed fuel amount or the like) or fees (road toll or the like) needed by the vehicle to travel or move through a link. The ambient weather (whether it is raining or snowing) or temperature of the vehicle can be deduced from the activity log of the environment accommodation device. On the basis of the activity log of the steering device or the braking device, a black spot where attention is needed to be paid on driving can be estimated. 
     It is acceptable that the vehicular receiving element is configured to receive the multicast tagged with information of a designated cycle or a designated distance, and the communication controlling element is configured to transmit the probe information to the vehicular transmitting element every designated cycle or every designated distance traveled by the vehicle. 
     According to the vehicular communication system of the mentioned configuration, the information related to the travel log or the like of the vehicle in the designated area can be collected in real time from an appropriate vehicle as the probe information and at an appropriate frequency denoted by the designated cycle or the designated distance. 
     It is acceptable that the vehicular receiving element is configured to receive the multicast tagged with information of an area of a predefined shape having a boundary defined by latitude and longitude or a link identifier for identifying a link as the information of the designated area. 
     According to the vehicular communication system of the mentioned configuration, the information related to an area of a predefined shape served as the designated area or a link identified by a link identifier can be collected in real time from an appropriate vehicle as the probe information. 
     It is acceptable that the communication controlling element is configured to transmit the probe information to the vehicular transmitting element on condition that the present position of the vehicle at the present time is in the designated area and a past position thereof in the past designated time was in the designated area as well. 
     According to the vehicular communication system of the mentioned configuration, the probe information can be collected in real time from not only a vehicle whose present position is in the designated area at the present time but also a vehicle whose past position was present in the designated area in the past in consideration of the high capability that it holds useful information in estimating the present state thereof in the designated area. 
     It is acceptable that the communication controlling element is configured to store the multicast in a storing element on condition that a present position of the vehicle, a past position of the vehicle given by a travel log or a future position of the vehicle given by a travel schedule is in the designated area. 
     According to the vehicular communication system of the mentioned configuration, since a multicast will not be stored in a storing element of a vehicle if the vehicle is irrelevant to the designated area included in the multicast in consideration of the present position thereof or the like, therefore, the storage capacity of the storing element can be utilized efficiently. 
     To accomplish an object described above, there is provided in the present invention a vehicular information collecting system composed of the vehicular communication system and the server, wherein the server is provided with a multicast generating element configured to generate the multicast; a server transmitting element configured to transmit the multicast to the vehicle served as a subject; a server receiving element configured to receive the probe information transmitted from the vehicle; and an analyzing element configured to analyze the probe information received by the server receiving element. 
     According to the vehicular information collecting system of the present invention, the probe information is sent to the server from a vehicle out of an arbitrary number of vehicles whose present position is located in the designated area whose information is included in a multicast received by the vehicle. According thereto, the information related to the designated area can be collected in real time from an appropriate vehicle as the probe information by the server. Thereby, a movement cost, weather or temperature, an outbreak spot of an accident or a black spot where attention is needed to be paid on driving for the designated area and the like can be estimated on the basis of analysis on the probe information. 
     It is acceptable that the multicast generating element is configured to generate the multicast tagged with a vehicular identifier for identifying each of the vehicles; the communication controlling element is configured to transmit the probe information to the vehicular transmitting element further on condition that the vehicular identifier inherent in the vehicle is matched with the vehicular identifier tagged in the multicast; and the multicast generating element is configured to adjust a part of the vehicular identifiers so as to adjust the number of the vehicles served as the subject for collecting the probe information. 
     According to the vehicular information collecting system of the mentioned configuration, the number of the vehicles served as the subject for collecting the probe information can be adjusted through adjusting a part of the vehicular identifiers contained in the multicast. Thus, for example, when the collected probe information is insufficient, the probe information can be collected sufficiently by increasing the range of the subject for collecting the probe information, namely, the number of vehicles. On the other hand, however, when the probe information has been collected excessively, by decreasing the number of vehicles served as the subject for collecting the probe information, the probe information can be collected appropriately. 
     It is acceptable that the multicast generating element is configured to adjust the size or shape of the designated area so as to adjust the number of the vehicles served as the subject for collecting the probe information. 
     According to the vehicular information collecting system of the mentioned configuration, the number of the vehicles served as the subject for collecting the probe information as a result of adjusting the size or the shape of the designated area contained in the multicast. For example, when the collected probe information is insufficient, the range of the subject vehicles for collecting the probe information is increased through generating and broadcasting a new multicast containing a designated area broader than the prior one, and as a result thereof, the probe information can be collected sufficiently. On the other hand, however, when the probe information has been collected excessively, the range of the subject vehicles for collecting the probe information is decreased through generating and broadcasting a new multicast containing a designated area narrower than the prior one, and as a result thereof, the probe information can be collected appropriately. 
     It is acceptable that the server receiving element is configured to receive a request for the probe information of the designated area from a first vehicle; the multicast generating element is configured to generate the multicast for collecting the probe information according to the request received by the server receiving element; and the server transmitting element is configured to transmit the multicast to a second vehicle served as the vehicle mounted with the vehicular communication system, and to transmit the probe information received from the second vehicle by the server receiving element or an analysis result obtained by the analyzing element on the basis of the probe information to the first vehicle. 
     According to the vehicular information collecting system of the mentioned configuration, the probe information related to the designated area, which is needed by the first vehicle, can be collected from the second vehicle appropriately in real time. The probe information collected from the second vehicle or the analysis result based on the collected probe information can be provided to the first vehicle in real time. 
     To accomplish an object described above, there is provided in the present invention a vehicular communication program which is configured to make a vehicular computer provided with a wireless communication device function as the vehicular communication system aforementioned. 
     According to the vehicular communication program of the present invention, the vehicular computer can be functioned as the system which makes the server to collect the information related to a designated area from an appropriate vehicle in real time as the probe information. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram illustrating a vehicular information collecting system of the present invention. 
         FIG. 2  is a flow chart illustrating functions of the vehicular information collecting system. 
         FIG. 3(   a ) and  FIG. 3(   b ) are explanatory diagrams illustrating conditions of satisfaction for transmitting probe information, respectively. 
         FIGS. 4(   a ) to  4 ( c ) are schematic diagrams illustrating data formats for multicast, respectively. 
         FIG. 5  is a schematic diagram illustrating functions of the vehicular information collecting system. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, an embodiment of a vehicular information collecting system and the like according to the present invention will be described with reference to the drawings. 
     As illustrated in  FIG. 1 , the vehicular information collecting system is composed of a vehicular communication system  10  and a server  20 . The vehicular communication system  10  is mounted in each of plural vehicles (four-wheeled automobiles) Q. 
     The vehicular communication system  10  is composed of an ECU (Electronic Control Unit provided with a CPU, a ROM, a RAM, an I/O circuit, an A/D circuit and buses or the like joining the mentioned components). The ECU may be a vehicular computer mounted in the vehicle Q. A vehicular communication program is stored in a memory or a storing device included in the ECU as software. The vehicular communication program is retrieved and executed by the CPU appropriately so as to make the vehicular communication system  10  perform its functions. 
     The vehicular communication system  10  is provided with a vehicular receiving element  11 , a vehicular transmitting element  12 , a position determining element  13 , and a communication controlling element  14 . 
     The vehicular receiving element  11  is configured to receive a multicast tagged with information of a designated area, which is broadcast from the server  20  through the intermediary of a satellite  200 . 
     The vehicular transmitting element  12  is configured to transmit a probe information in the form of packet data to the server  20  through the intermediary of a network. 
     The position determining element  13  is composed of a GPS receiver and if necessary a sensor, such as an acceleration sensor or the like, for determining a posture or travel state of the vehicle Q. The position determining element  13  is configured to determine sequentially positions of the vehicle Q on the basis of GPS signals received from a GPS satellite (it may be the same as or different from the satellite  200 ) by the GPS receiver and if necessary output signals from the sensor. The positions of the vehicle Q determined by the position determining element  13  are stored sequentially in the storing device with the determination time thereof. 
     The communication controlling element  14  is configured to collect information denoting a state of the vehicle Q as the probe information from output signals from a sensor set  15  mounted in the vehicle Q, and to transmit the probe information to the vehicular transmitting element  12  on condition that the present position of the vehicle Q determined by the position determining element  13  is located in a designated area contained in the multicast. 
     In addition to the vehicular communication system  10 , the vehicle Q is also mounted with a navigation apparatus  100 . The navigation apparatus  100  is composed of an ECU (it may be the same as or different from the ECU included in the vehicular communication system  10 ), and is provided with an interface configured to allow a user to input or the like a desired position and a departure position, and a display configured to show a navigation route leading the vehicle Q from the present position or the departure position to the desired position on a map. 
     The server  20  is composed of a computer (composed of a CPU, a ROM, a RAM, an I/O circuit and the like) capable of communicating with every vehicular communication system  10  via the network. The server  20  is provided with a server receiving element  21 , a server transmitting element  22 , a multicast generating element  23 , and an analyzing element  24 . 
     The server receiving element  21  is configured to receive a request for the probe information from the vehicle Q served as a first vehicle via the network, and to receive the probe information from the vehicle Q served as a second vehicle via the network. 
     The server transmitting element  22  is configured to broadcast or transmit the multicast to an unspecific subject, namely a plurality of vehicles Q, via the satellite  200 . 
     The multicast generating element  23  is configured to generate the multicast tagged with information of the designated area. 
     The analyzing element  24  is configured to analyze the probe information received by the server receiving element  21 . 
     Hereinafter, descriptions will be carried out on functions of the vehicular information collecting system with the aforementioned configuration. According to different situations, the vehicle Q may have the role of the first vehicle Q 1  as well as the second vehicle Q 2  where appropriate. 
     For the first vehicle Q 1 , the present position P 1  of the first vehicle Q 1  is sequentially determined by the position determining element  13  (FIG.  2 /STEP  112 ). 
     The present position P 1  of the first vehicle Q 1  and the desired position P 2  input to the navigation apparatus  100  by the user are recognized by the communication controlling element  14  (FIG.  2 /STEP  114  (refer to  FIG. 3 )). As a substitute for the present position P 1  of the first vehicle Q 1 , a departure position thereof input to the navigation apparatus  100  by the user may also be recognized. 
     Thereafter, a request for the probe information is generated by the communication controlling element  14  on the basis of either one or both of the present position P 1  and the desired position P 2  (FIG.  2 /STEP  116 ). 
     For example, the communication controlling element  14  generates a request containing either one or both of the present position P 1  and the desired position P 2 , a navigation route r joining the present position P 1  and the desired position P 2  searched by the navigation apparatus  100  on the basis of a navigation map stored in the storing device, or a link identifier for identifying a link Li (i=1, 2, . . . n) constituting the navigation route r. The generated request is transmitted from the first vehicle Q 1  to the server  20  by the vehicular transmitting element  12  (refer to the arrowed solid line  1  in  FIG. 5 ). 
     In the server  20 , whether or not the request has been received by the server receiving element  21  is determined (FIG.  2 /STEP  202 ). If it is determined that the request is present (FIG.  2 /STEP  202  . . . YES), a designated area is set by the multicast generating element  23  according to the request (FIG.  2 /STEP  204 ). 
     As illustrated in  FIG. 3(   a ), when the present position P 1  of the first vehicle Q 1  is included in the request, a rectangular area S (P 1 ) containing or centered at the present position P 1 , or a link contained therein can be set as a designated area. As illustrated in  FIG. 3(   a ), when the desired position P 2  of the first vehicle Q 1  is included in the request, a rectangular area S (P 2 ) containing or centered at the desired position P 2 , or a link contained therein can be set as a designated area. 
     In addition to the rectangular area, an area having an arbitrary shape, such as a triangular shape, a circular shape, an elliptical shape or the like, may be set as the designated area. As illustrated in  FIG. 3(   a ), when the present position P 1  and the desired position P 2  of the first vehicle Q 1  are included in the request, a support route R joining the present position P 1  and the desired position P 2  is searched; apart of or the entire part of the areas S 1 (R) to S 7 (R) containing a part of the support route R or the links contained in a part of or the entire part of the areas S 1 (R) to S 7 (R) can be set by the server  20  as the designated area. The support route R may be searched on the basis of the up-to-date map information stored in a map data base, the up-to-date road traffic information stored in a road traffic information data base, the up-to-date weather information stored in a weather information data base and the like. 
     As illustrated in  FIG. 3(   a ), when the navigation route r searched by the navigation apparatus  100  mounted in the first vehicle Q 1  is included in the request, a part of or the entire part of the areas S 1 ( r ) to S 5 ( r ) containing a part of the navigation route r or links contained in a part of or the entire part of the areas S 1 ( r ) to S 5 ( r ) can be set as the designated area. 
     Further, as illustrated in  FIG. 3(   b ), when apart of or the entire part of a link Δri (i=1 to n) constituting the navigation route r is included in the request, the link Δri, an area containing the link Δri, or a link contained in the area can be set as the designated area. Furthermore, as illustrated in  FIG. 3(   b ), a part of or the entire part of a link ΔRj (j=1 to m) constituting the support route R, an area containing the link ΔRj, or a link contained in the area can be set as the designated area. 
     Subsequently, the multicast is generated by the multicast generating element  23  (FIG.  2 /STEP  206 ). 
     Specifically, as illustrated in  FIG. 4(   a ), a multicast of a data format including respectively fields for the type of transmitting condition, the designated area (with the latitude and the longitude denoting the bottom left corner and the top right corner of the rectangular area, respectively), the transmitting end time (X minutes after the present time or the transmitting initial time) and the transmitting frequency (Y times per minute or per meter) is generated. 
     Moreover, as illustrated in  FIG. 4(   b ), a multicast of a data format including respectively fields for the type of transmitting condition, the designated area (designated number of links or link ID (identifier)), the transmitting end time and the transmitting frequency is generated. 
     Furthermore, as illustrated in  FIG. 4(   c ), a multicast of a data format including respectively fields for the type of transmitting condition, the designated area (with the latitude and the longitude denoting the bottom left corner and the top right corner of the rectangular area, respectively), VIN (the nth digit of VIN is “6”, for example), the transmitting end time and the transmitting frequency is generated. The generated multicast is broadcast to an arbitrary second vehicle Q 2  from the server transmitting element  22  through the intermediary of the satellite  200  (refer to FIG.  5 /dotted arrow line  2 ). 
     For the second vehicle Q 2 , the present position of the second vehicle Q 2  is sequentially determined by the position determining element  13  (FIG.  2 /STEP  122 ). 
     Then, the information denoting the state of the second vehicle Q 2 , which is obtained from the output signals of the sensor set  15 , is collected as the probe information by the communication controlling element  14  (FIG.  2 /STEP  124 ). 
     Specifically, the information denoting a part of or the entire part of a link where the second vehicle Q 2  traveled and a movement cost thereof, an activity log of an environment accommodation device (a wiper, an air conditioner or the like) operated in compliance with an ambient weather or temperature of the second vehicle Q 2 , and an activity log of a steering device or a braking device mounted in the second vehicle Q 2  (a location where the wheel is rapidly turned or a location where the brake is paddled hard) is collected or recognized as the probe information. 
     Thereafter, whether or not the multicast has been received by the vehicular receiving element  11  is determined (FIG.  2 /STEP  126 ). If it is determined that the multicast is present (FIG.  2 /STEP  126  . . . YES), whether or not the transmitting condition for transmitting the probe information has been satisfied is determined by the communication controlling element  14  (FIG.  2 /STEP  128 ). 
     Specifically, the present position P 1  of the second vehicle Q 2  or a past position thereof before a designated duration is included in the designated area (the rectangular area of a boundary defined by the latitude and the longitude in the multicast illustrated in  FIG. 4(   a ) and  FIG. 4(   c ), or the link identified by the link ID in the multicast illustrated in  FIG. 4(   b )) is used as the transmitting condition. Thereby, as illustrated in  FIG. 5 , at the time where the multicast is broadcast, in addition to a second vehicle Q 2  whose present position is in the designated area (the shaded portion), another second vehicle Q 2  which has been out of the designated area in a way illustrated by the bold arrow line also satisfies the transmitting condition as the past position thereof before a designated duration was in the designated area. 
     In the multicast illustrated in  FIG. 4(   c ), it is used as a further transmitting condition when a designated digit number of the VIN of the second vehicle Q 2  is a specific symbol such as “6”. When it is determined that the transmitting condition has been satisfied (FIG.  2 /STEP  128  . . . YES), the probe information is sent from the second vehicle Q 2  to the server  20  at a designated frequency, in detail, every designated cycle or every designated distance traveled by the vehicle Q 2  (refer to FIG.  5 /the dotted and dashed arrow line  3 ). 
     The collected probe information is analyzed by the analyzing element  24  in the server  20  (FIG.  2 /STEP  208 ). 
     Specifically, a link cost (predicted travel time or the like) for each link included in the designated area is calculated on the basis of each link where the second vehicle Q 2  traveled and the movement cost thereof included in the probe information. In the calculation of the link cost, a predicted travel time for the first vehicle Q 1  to reach a link from the present position P 1  thereof which maybe calculated according to the distance for the vehicle Q 1  to travel from the present position P 1  to the link, or a predicted timing at which the first vehicle Q 1  reaches the link may be used. 
     On the basis of the activity log of the environment accommodation device (a wiper, an air conditioner or the like) of the second vehicle Q 2  which is included in the probe information, whether it is raining or snowing in the designated area, what the atmospheric temperature is or whether the road is frozen or not in the designated can be estimated. On the basis of the activity log of the steering device or the braking device mounted in the second vehicle Q 2  which is included in the probe information, the location where the wheel is rapidly turned or the location where the brake is paddled hard, and consequently a black spot where attention is needed to be paid on driving can be estimated. Note that it is acceptable to search an appropriate support route R from the viewpoint of moving the first vehicle Q 1  smoothly to the desired position P 2  by using the analysis result of the link cost or the like. The probe information or the analysis result performed by the analyzing element  24  on the basis of the probe information is transmitted by the server transmitting element  22  from the server  20  to the first vehicle Q 1  (refer to FIG.  5 /the dashed arrow line  4 ). 
     Thereafter, a piece of information based on the probe information is output by the navigation apparatus  100  in the first vehicle Q 1  (FIG.  2 /STEP  118 ). 
     Specifically, on the basis of the link cost or the like contained in the probe information, the navigation route r joining the present position P 1  and the desired position P 2  is searched and displayed on the display by the navigation apparatus  100 . Further, a mark or an icon denoting the analysis result of the probe information, namely the weather conditions such as whether it is raining or snowing or what the atmospheric temperature is, can be placed on a map in accordance with the designated area and the map can be shown on the display. 
     Further more, a mark or an icon denoting the analysis result of the probe information, such as a black spot where attention is needed to be paid on driving or an outbreak spot of an accident can be placed on the map in accordance with the designated area and the map can be shown on the display. Moreover, the support route R searched by the server  20 , or the navigation route r calculated or searched by the server  20  so as to contain a component link of the support route R can be shown on the display. 
     According to the vehicular communication system  10  with the aforementioned functions, the probe information can be sent to the server  20  from a second vehicle Q 2  out of an arbitrary number of the second vehicles Q 2 , whose present position is located in the designated area whose information is included in a multicast received by the second vehicles Q 2 , namely, the present position thereof is in a designated area with high necessity to move smoothly the first vehicle Q 1  to the desired position P 2  or the like (refer to FIG.  5 /the arrow line  3 ). 
     Further, the probe information can be collected in real time from a second vehicle Q 2  whose past position was in the designated area even though the present position thereof is beyond the designated area in consideration of the high capability that the second vehicle Q 2  holds useful information in estimating the present state thereof in the designated area (refer to FIG.  5 /the arrow line  3 ). 
     According thereto, the information related to the designated area can be collected as the probe information in real time from an appropriate vehicle Q at an appropriate frequency denoted by the designated cycle or distance. Then, according to the analysis on the probe information, the movement cost, the weather or the temperature, the outbreak spot of accident or the black spot where attention should be paid on driving, or the like of the designated area can be estimated and provided to the user of the first vehicle Q 1  via the navigation apparatus  100 . Moreover, the probe information is collected by the server  20  only from the second vehicles Q 2  with the designated VIN (vehicle identifier), thus, the communicated information amount can be controlled appropriately from the viewpoint of saving communication cost, regulating communication traffic or the like. 
     It is acceptable for the communication controlling element  14  to store the multicast in the storing device on condition that the present position P 1 , the past position given by the travel log or the future position given by the travel schedule of the vehicle is included in the designated area. Since a multicast will not be stored in the storing device of the vehicle if the vehicle is irrelevant to the designated area included in the multicast in consideration of the present position thereof or the like, therefore, the storage capacity of the storing device can be utilized efficiently. 
     In the aforementioned embodiment, the designated area is set according to a request from the first vehicle Q 1  (refer to FIG.  2 /STEP  204 ). However, as another embodiment, it is acceptable for the multicast generating element  23  to search a location where an event is being held from a data base and set an area including the location where the event is being held as the designated area. Then, a multicast containing the designated area is generated and is broadcast to an arbitrary number of vehicles Q at an appropriate time, such as before, in, or after the duration where the event is held. Accordingly, among plural vehicles Q received with the multicast, the probe information can be collected from a vehicle Q close to the event location by the server  20 . 
     It is acceptable to configure the multicast generating element  23  to adjust a part of VIN (vehicular identifier) so as to adjust the number of vehicles Q served as the subject for collecting the probe information. According thereto, the number of vehicles Q served as the subject for collecting the probe information can be adjusted via adjusting apart of VIN contained in the multicast. 
     For example, when the collected probe information is insufficient at the time when the multicast containing a VIN whose last digit is “6” (refer to  FIG. 4(   c )) is broadcast, the range of the subject for collecting the probe information can be increased by generating and broadcasting another new multicast containing a VIN whose last digit is “3”, and consequently, the probe information can be collected sufficiently. 
     On the other hand, however, when the probe information has been collected excessively at the time when the multicast containing the VIN whose last digit is “6” (refer to  FIG. 4(   c )) is broadcast, the range of the subject for collecting the probe information can be decreased by generating and broadcasting a fresh multicast containing the VIN whose digit prior to the last one is limited to “4”, “8” or “9”, and consequently, the probe information can be collected appropriately. 
     It is acceptable that the multicast generating element  23  is configured to adjust the size or shape of the designated area so as to adjust the number of the vehicles Q served as the subject for collecting the probe information. According to the mentioned configuration, the size or the shape of the designated area contained in the multicast can be adjusted, and consequently, the number of vehicles Q served as the subject for collecting the probe information can be adjusted. 
     For example, when the collected probe information is insufficient, the range of the subject vehicles for collecting the probe information is increased through generating and broadcasting a new multicast containing a designated area broader than the prior one, and as a result thereof, the probe information can be collected sufficiently. 
     On the other hand, however, when the probe information has been collected excessively, the range of the subject vehicles for collecting the probe information is decreased through generating and broadcasting a new multicast containing a designated area narrower than the prior one, and as a result thereof, the probe information can be collected appropriately.