Patent Publication Number: US-2023150493-A1

Title: Preceding vehicle selection device, preceding vehicle selection method, and non-transitory recording medium

Description:
FIELD 
     The present invention relates to a preceding vehicle selection device, a preceding vehicle selection method, and a non-transitory recording medium. 
     BACKGROUND 
     To reduce the amount of fuel or electric power required for a vehicle to run, it is effective to reduce the air resistance at the time of running. In the past, as a technique for reducing the air resistance at the time of running, a follow-up travel making a vehicle follow a preceding vehicle has been known. In the follow-up travel, due to the effect of reduction of drag by the preceding vehicle, the air resistance acting on a vehicle running behind the preceding vehicle is reduced. 
     As one example of such follow-up travel, “platooning” where a plurality of vehicles run forming a group is known. In the platoon forming device described in PTL 1, the running plans of groups of vehicles forming platoons are acquired and the group of vehicles with a running plan similar to the host vehicle is selected as the group of vehicles which the host vehicle should merge with. By doing this, the duration of the follow-up travel becomes longer and the effect of the follow-up travel is enhanced. 
     CITATIONS LIST 
     Patent Literature 
     
         
         [PTL 1] Japanese Unexamined Patent Publication No. 2008-003675 
       
    
     SUMMARY 
     Technical Problem 
     However, detailed running plans such as the destinations and rest stops are information of high levels of privacy. Occupants of vehicles would not necessarily agree to provide their running plans. Further, entering running plans is a bothersome task for occupants of vehicles. Therefore, the opportunities for acquiring the running plans of surrounding vehicles are limited and a preceding vehicle suitable for being followed is liable to be unable to be selected from among the surrounding vehicles. 
     Therefore, in consideration of the above technical issues, an object of the present invention is to select a preceding vehicle suitable for being followed without relying on the detailed running plans of the surrounding vehicles. 
     Solution to Problem 
     The summary of the present disclosure is as follows. 
     (1) A preceding vehicle selection device for selecting a preceding vehicle suitable to be followed by a host vehicle, comprising a processor configured to: estimate a continuous running distance from a present time of a surrounding vehicle based on information relating to the surrounding vehicle for each of a plurality of surrounding vehicles at surroundings of the host vehicle; estimate a followable distance when the host vehicle follows the surrounding vehicle based on the continuous running distance from the present time of the surrounding vehicle for each of the plurality of surrounding vehicles; and select the preceding vehicle from among the plurality of surrounding vehicles based on the followable distance, wherein the information relating to the surrounding vehicle includes at least one of an SOC or an amount of remaining fuel of the surrounding vehicle, and a continuous running time or a continuous running distance up to the present time of the surrounding vehicle. 
     (2) The preceding vehicle selection device described in above (1), wherein the processor is configured to calculate a possible cruising distance from the present time of the surrounding vehicle based on the SOC or the amount of remaining fuel of the surrounding vehicle, as the continuous running distance from the present time of the surrounding vehicle. 
     (3) The preceding vehicle selection device described in above (1), wherein the processor is configured to calculate a possible driving distance from the present time of a driver of the surrounding vehicle based on the continuous running time or the continuous running distance up to the present time of the surrounding vehicle, as the continuous running distance from the present time of the surrounding vehicle. 
     (4) The preceding vehicle selection device described in above (1), wherein the processor is configured to calculate a possible cruising distance of the surrounding vehicle based on the SOC or the amount of remaining fuel of the surrounding vehicle, calculate a possible driving distance from the present time of a driver of the surrounding vehicle based on the continuous running time or the continuous running distance up to the present time of the surrounding vehicle, and set a shorter distance among the possible cruising distance and the possible driving distance to the continuous running distance from the present time of the surrounding vehicle. 
     (5) The preceding vehicle selection device described in any one of above (1) to (4), wherein the processor is configured to calculate an effect index representing an effect when the host vehicle follows the surrounding vehicle for a predetermined distance based on the information relating to the surrounding vehicle for each of the plurality of surrounding vehicles, and select the preceding vehicle from among the plurality of surrounding vehicles based on the followable distance and the effect index. 
     (6) The preceding vehicle selection device described in above (5), wherein the processor is configured to estimate a continuous running distance from the present time of the host vehicle based on the information relating to the host vehicle, and set a shorter distance among the continuous running distance from the present time of the surrounding vehicle and the continuous running distance from the present time of the host vehicle to the followable distance. 
     (7) The preceding vehicle selection device described in above (6), wherein the processor is configured to calculate a possible cruising distance of the host vehicle based on the SOC or the amount of remaining fuel of the host vehicle, as the continuous running distance from the present time of the host vehicle. 
     (8) The preceding vehicle selection device described in above (6), wherein the processor is configured to calculate a possible driving distance from the present time of a driver of the host vehicle based on the continuous running time or the continuous running distance up to the present time of the host vehicle, as the continuous running distance from the present time of the host vehicle. 
     (9) The preceding vehicle selection device described in above (6), wherein the processor is configured to calculate a possible cruising distance of the host vehicle based on an SOC or an amount of remaining fuel of the host vehicle, calculate a possible driving distance from the present time of a driver of the host vehicle based on a continuous running time or a continuous running distance up to the present time of the host vehicle from the present, and set a shorter distance among the possible cruising distance and the possible driving distance to the continuous running distance from the present time of the host vehicle. 
     (10) A preceding vehicle selecting method executed by a computer, including estimating a continuous running distance from a present time of a surrounding vehicle based on information relating to the surrounding vehicle for each of a plurality of surrounding vehicles at surroundings of the host vehicle, estimating a followable distance when a host vehicle follows a surrounding vehicle based on the continuous running distance from the present time of the surrounding vehicle for each of the plurality of surrounding vehicles, and selecting from among the plurality of surrounding vehicles a preceding vehicle suitable to be followed by the host vehicle based on the followable distance, wherein the information relating to the surrounding vehicle includes at least one of an SOC or an amount of remaining fuel of the surrounding vehicle, and a continuous running time or a continuous running distance up to the present time of the surrounding vehicle. 
     (11) A non-transitory recording medium having recorded thereon a computer program for selecting a preceding vehicle, the computer program causing a computer to: estimate a continuous running distance from a present time of a surrounding vehicle based on information relating to the surrounding vehicle for each of a plurality of surrounding vehicles at surroundings of the host vehicle; estimate a followable distance when a host vehicle follows a surrounding vehicle based on the continuous running distance from the present time of the surrounding vehicle for each of the plurality of surrounding vehicles; and select from among the plurality of surrounding vehicles a preceding vehicle suitable to be followed by the host vehicle based on the followable distance, wherein the information relating to the surrounding vehicle includes at least one of an SOC or an amount of remaining fuel of the surrounding vehicle, and a continuous running time or a continuous running distance up to the present time of the surrounding vehicle. 
     Advantageous Effects of Invention 
     According to the present invention, it is possible to select a preceding vehicle suitable for being followed without relying on the detailed running plans of the surrounding vehicles. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a schematic view of the configuration of a vehicle control system including a preceding vehicle selection device according to a first embodiment of the present invention. 
         FIG.  2    is a view showing one example of a situation where a plurality of vehicles are running on a motorway. 
         FIG.  3    is a functional block diagram of a processor of an ECU in the first embodiment. 
         FIG.  4    is a flow chart showing a control routine of preceding vehicle selection processing in the first embodiment. 
         FIG.  5    is a flow chart showing a control routine of followable distance estimation processing in the first embodiment. 
         FIG.  6    is a functional block diagram of a processor of an ECU in a second embodiment. 
         FIG.  7    is a flow chart showing a control routine of preceding vehicle selection processing in the second embodiment. 
         FIG.  8    is a flow chart showing a control routine of effect index calculation processing in the second embodiment. 
         FIG.  9    is a view showing one example of a table for determining an evaluation value for surrounding vehicles. 
         FIG.  10    is a functional block diagram of a processor of an ECU in a third embodiment. 
         FIG.  11    is a flow chart showing a control routine of followable distance estimation processing in the third embodiment. 
         FIG.  12    is a schematic view of the configuration of a client-server system including a preceding vehicle selection device according to a fourth embodiment of the present invention. 
         FIG.  13    is a view schematically showing the configuration of a server. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Below, embodiments of the present invention will be explained in detail with reference to the drawings. Note that, in the following explanation, similar component elements are assigned the same reference numerals. 
     First Embodiment 
     Below, referring to  FIG.  1    to  FIG.  5   , a first embodiment of the present invention will be explained. 
       FIG.  1    is a schematic view of the configuration of a vehicle control system  1  including a preceding vehicle selection device according to the first embodiment of the present invention. The vehicle control system  1  is mounted in a vehicle and performs various types of control of the vehicle. 
     As shown in  FIG.  1   , the vehicle control system  1  is provided with a surrounding information detection device  2 , a GNSS receiver  3 , a map database  4 , a navigation device  5 , a vehicle state detection device  6 , actuators  7 , a human machine interface (HMI)  8 , a communication device  9 , and an electronic control unit (ECU)  10 . The surrounding information detection device  2 , the GNSS receiver  3 , the map database  4 , the navigation device  5 , the vehicle state detection device  6 , the actuators  7 , the HMI  8 , and the communication device  9  are electrically connected to the ECU  10  through an internal network based on the CAN (Controller Area Network) or other standard etc. 
     The surrounding information detection device  2  acquires data on the surroundings of a vehicle (host vehicle) (images, point group data, etc.) and detects surrounding information of the vehicle (for example, surrounding vehicles, lanes, etc.) For example, the surrounding information detection device  2  is a milli wave radar, a camera (for example, stereo camera), a laser imaging detection and ranging device (LIDAR), or an ultrasonic wave sensor (sonar) or any combination of the same. The output of the surrounding information detection device  2 , that is, the surrounding information of vehicles detected by the surrounding information detection device  2 , is sent to the ECU  10 . 
     The GNSS receiver  3  detects the current position of the vehicle (for example, a latitude and longitude of the vehicle) based on position measurement information obtained from a plurality of (for example, three or more) positioning satellites. Specifically, the GNSS receiver  3  captures a plurality of positioning satellites and receives signals emitted from the positioning satellites. Further, the GNSS receiver  3  calculates the distances to the positioning satellites based on the difference between the times of emission and times of reception of the signals and detects the current position of the vehicle based on the distances to the positioning satellites and the positions of the positioning satellites (orbital information). The output of the GNSS receiver  3 , that is, the current position of the vehicle detected by the GNSS receiver  3 , is sent to the ECU  10 . 
     Note that, “GNSS” (Global Navigation Satellite System) is a general name of the GPS of the U.S., GLONASS of Russia, Galileo of Europe, QZSS of Japan, BeiDou of China, IRNSS of India, and other satellite positioning systems. That is, a GPS receiver is one example of the GNSS receiver  3 . 
     The map database  4  stores map information. The ECU  10  acquires map information from the map database  4 . Note that, the map database may be provided outside of the vehicle (for example, at the server etc.), and the ECU  10  may acquire map information from outside the vehicle. 
     The navigation device  5  sets the running route of the vehicle up to the destination based on the current position of the vehicle detected by the GNSS receiver  3 , the map information of the map database  4 , the input by an occupant of the vehicle (for example, the driver), etc. The running route set by the navigation device  5  is sent to the ECU  10 . 
     The vehicle state detection device  6  detects a state quantity of the vehicle. The vehicle state detection device  6  includes, for example, a vehicle speed sensor for detecting a speed of the vehicle, a yaw rate sensor for detecting a yaw rate of the vehicle, a battery sensor for detecting a state quantity of a battery of the vehicle (voltage, temperature, input/output current, etc.), etc. The output of the vehicle state detection device  6 , that is, the state quantity of the vehicle detected by the vehicle state detection device  6 , is sent to the ECU  10 . 
     The actuators  7  make the vehicle operate. For example, the actuators  7  include a drive device for acceleration of the vehicle (for example, at least one of an internal combustion engine and an electric motor), a brake actuator for braking (decelerating) the vehicle, and a steering motor for steering the vehicle. The ECU  10  controls the actuators  7  to control the behavior of the vehicle. 
     In the present embodiment, the vehicle control system  1  functions as an advanced driver assistance system (ADAS) and controls the actuators  7  to make predetermined driver assistance functions operate. The predetermined driver assistance functions, for example, include adaptive cruise control (ACC) for automatically controlling the speed of the vehicle according to whether a preceding vehicle is present, and lane keeping assist (LKA) or lane tracing assist (LTA) for automatically controlling the steering of the vehicle so that the vehicle is maintained in a lane, etc. 
     The HMI  8  transfers information between the vehicle and the occupants of the vehicle (for example, the driver). The HMI  8  has an output part for outputting information to occupants of the vehicle (for example, a display, speakers, vibration unit, etc.) and an input unit to which information is input by occupants of the vehicle (for example, a touch panel, operating buttons, operating switches, microphone, etc.) The output of the ECU  10  is notified to the occupants of the vehicle through the HMI  8 , while the input from the occupants of the vehicle is sent to the ECU  10  through the HMI  8 . The HMI  8  is one example of an input device, an output device, or an input/output device. Note that, a mobile terminal of an occupant of the vehicle (a smartphone, a tablet terminal, etc.) may be connected to the ECU  10  to be able to communicate with it through a cable or wirelessly and function as the HMI  8 . Further, the HMI  8  may be integral with the navigation device  5 . 
     The communication device  9  can communicate with the outside of the vehicle and enables communication between the vehicle and the outside of the vehicle. For example, the communication device  9  includes a wide area communicator enabling wide area communication between the vehicle and the outside of the vehicle through a communication network like a carrier network or the Internet (for example, a data communication module (DCM)), and an inter-vehicle communicator enabling inter-vehicle communication between the vehicle and a surrounding vehicle using a predetermined frequency band. 
     The ECU  10  performs various types of control of the vehicle. As shown in  FIG.  1   , the ECU  10  comprises a communication interface  11 , a memory  12 , and a processor  13 . The communication interface  11  and memory  12  are connected to the processor  13  through signal wires. Note that, in the present embodiment, a single ECU  10  is provided, but a plurality of ECUs may be provided for the individual functions. 
     The communication interface  11  has an interface circuit for connecting the ECU  10  to the internal vehicle network. The ECU  10  is connected to other vehicle-mounted equipment through the communication interface  11 . The communication interface  11  is one example of a communicating part of the ECU  10 . 
     The memory  12 , for example, has a volatile semiconductor memory and nonvolatile semiconductor memory. The memory  12  stores computer programs, data, etc. used when the processor  13  performs various types of processing. 
     The processor  13  has one or more central processing units (CPUs) and their peripheral circuits. Note that, the processor  13  may further have a processing circuit such as a logic unit or arithmetic unit. 
     In this regard, to reduce the amount of fuel or electric power required for the vehicle to run, it is effective to reduce the air resistance at the time of running. In the past, as a technique for reducing the air resistance at the time of running, a follow-up travel making a vehicle follow a preceding vehicle has been known. In such follow-up travel, the air resistance acting on a vehicle running behind the preceding vehicle is reduced due to the effect of the preceding vehicle in reducing drag. Note that, “platooning” where a plurality of vehicles run formed into groups is one example of the follow-up travel. 
       FIG.  2    is a view showing one example of a situation where a plurality of vehicles are running on a motorway. In the example of  FIG.  2   , five surrounding vehicles  30  are running in the surroundings of a host vehicle  20 . Under these circumstances, the plurality of vehicles (five surrounding vehicles  30 ) become preceding vehicle candidates of the host vehicle for follow-up travel. 
     If the host vehicle performs a follow-up travel, it is desirable that the preceding vehicle be selected so that the effect obtained by the follow-up travel becomes as large as possible. In the present embodiment, the ECU  10  mounted in the host vehicle functions as a preceding vehicle selection device for selecting the preceding vehicle suitable to be followed by the host vehicle. 
       FIG.  3    is a functional block diagram of the processor  13  of the ECU  10  in the first embodiment. In the present embodiment, the processor  13  has a first running distance estimating part  15 , a followable distance estimating part  16 , and a preceding vehicle selecting part  17 . The first running distance estimating part  15 , the followable distance estimating part  16 , and the preceding vehicle selecting part  17  are function modules realized by a computer program stored in the memory  12  of the ECU  10  being run by the processor  13  of the ECU  10 . Note that, these function modules may be realized by dedicated processing circuits provided at the processor  13 . 
     The first running distance estimating part  15  estimates the continuous running distance from the present time of a surrounding vehicle based on information relating to the surrounding vehicle for each of the plurality of surrounding vehicles around the host vehicle. For example, information relating to a surrounding vehicle includes at least one of a state of charge of a battery (SOC) or an amount of remaining fuel of the surrounding vehicle and a continuous running time or a continuous running distance up to the present time of the surrounding vehicle. That is, the first running distance estimating part  15  estimates the continuous running distance from the present time of a surrounding vehicle based on at least one of an SOC or an amount of remaining fuel of the surrounding vehicle and a continuous running time or continuous running distance up to the present time of the surrounding vehicle. By this, it is possible to estimate the continuous running distance from the present time of a surrounding vehicle without acquiring a detailed running plan including rest stops and the destination from the surrounding vehicle. Below, a specific example of a method of estimating a continuous running distance from the present time of a surrounding vehicle will be explained. 
     As one example of a situation where a vehicle running toward a destination will leave a running lane, mention may be made of recharging the vehicle due to insufficient electric power or refueling the vehicle due to insufficient fuel. That is, if the possible cruising distance of the vehicle becomes zero, continuous running of the vehicle will be interrupted and the vehicle will stop for recharging or refueling. Further, basically, the possible cruising distance of a vehicle becomes shorter the lower the SOC of the vehicle and becomes shorter the smaller the amount of remaining fuel of the vehicle. For this reason, the first running distance estimating part  15  calculates the possible cruising distance of a surrounding vehicle based on the SOC or the amount of remaining fuel of the surrounding vehicle so as to estimate the continuous running distance from the present time of the surrounding vehicle. Note that, the “possible cruising distance of a surrounding vehicle” means the distance over which the surrounding vehicle can run without requiring recharging and refueling. 
     Further, as another example of a situation where a vehicle running toward a destination will leave the running lane, mention may be made of a driver resting so as to recover from fatigue. That is, if a possible driving distance of the driver becomes zero, continuous running of the vehicle will be interrupted and the vehicle will stop for a rest. Further, basically, the possible driving distance of the driver of a vehicle becomes shorter the longer the continuous running time or the continuous running distance up to the present time of the vehicle. For this reason, the first running distance estimating part  15  calculates the possible driving distance from the present time of the driver of a surrounding vehicle based on the continuous running time or the continuous running distance up to the present time of the surrounding vehicle so as to estimate the continuous running distance from the present time of the surrounding vehicle. 
     Further, the first running distance estimating part  15  estimates the continuous running distance from the present time of a surrounding vehicle by comparing the possible cruising distance of the surrounding vehicle and the possible driving distance from the present time of the driver of the surrounding vehicle. Specifically, the first running distance estimating part  15  sets the shorter distance of the possible cruising distance and the possible driving distance to the continuous running distance from the present time of the surrounding vehicle. That is, if recharging or refueling is expected to be performed before a rest stop, the possible cruising distance is set to the continuous running distance, while if a rest stop is expected to be made before recharging or refueling, the possible driving distance is set to the continuous running distance. 
     The followable distance estimating part  16  estimates a followable distance when the host vehicle follows a surrounding vehicle based on the continuous running distance from the present time of the surrounding vehicle for each of the plurality of surrounding vehicles. In the present embodiment, the followable distance estimating part  16  sets the continuous running distance from the present time of the surrounding vehicle to the followable distance. 
     The preceding vehicle selecting part  17  selects a preceding vehicle from among the plurality of surrounding vehicles based on the followable distance. Specifically, the preceding vehicle selecting part  17  selects the surrounding vehicle with the longest followable distance as the preceding vehicle. By doing this, it is possible to lengthen the continuous time of a follow-up travel and in turn possible to enhance the effect obtained by the follow-up travel. Further, in the present embodiment, the followable distance for the case where the host vehicle follows a surrounding vehicle is calculated without acquiring detailed running plans including rest stops and the destinations from the surrounding vehicles. For this reason, it is possible to select a preceding vehicle suitable for being followed by the host vehicle without relying on detailed running plans of the surrounding vehicles. 
     Below, referring to  FIG.  4    and  FIG.  5   , a control routine of the above-mentioned processing will be explained in detail.  FIG.  4    is a flow chart showing a control routine of preceding vehicle selection processing in the first embodiment. The present control routine is repeatedly performed by the processor  13  of the ECU  10  at predetermined intervals. 
     First, at step S 101 , the preceding vehicle selecting part  17  judges whether a start condition of a follow-up travel is satisfied. The start condition of a follow-up travel is determined in advance. For example, it is satisfied when an occupant of the host vehicle requests actuation of ACC through the HMI  8 . Note that, the start condition of a follow-up travel may be the host vehicle running on a motorway at greater than or equal to a predetermined speed etc. If at step S 101  it is judged that the start condition of a follow-up travel is not satisfied, the present control routine ends. 
     On the other hand, if at step S 101  it is judged that the start condition of a follow-up travel is satisfied, the present control routine proceeds to step S 102 . At step S 102 , the preceding vehicle selecting part  17  identifies the number N of surrounding vehicles able to communicate with the host vehicle by inter-vehicle communication, that is, the number N of surrounding vehicles positioned in a range of communication of inter-vehicle communication, and assigns vehicle nos. ( 1  to N) to each of N number of surrounding vehicles. 
     Next, at step S 103 , the preceding vehicle selecting part  17  adds “1” to the vehicle no. “i” to update the vehicle no. “i”. Note that, the initial value of the vehicle no. “i” when the ignition switch of the host vehicle is turned on is zero. 
     Next, at step S 104 , the subroutine shown in  FIG.  5    is executed.  FIG.  5    is a flow chart showing a control routine of a followable distance estimation processing in the first embodiment. 
     First, at step S 201 , the first running distance estimating part  15  acquires information relating to the surrounding vehicle through inter-vehicle communication between the host vehicle and the surrounding vehicle. In the present embodiment, as information relating to the surrounding vehicle, the position and speed of the surrounding vehicle, the SOC or amount of remaining fuel, the continuous running time or continuous running distance up to the present time, the average electric power consumption or average fuel consumption in a predetermined time period, etc. are sent from the surrounding vehicle to the host vehicle. The start point of measurement of the continuous running time or continuous running distance is when the ignition switch is turned on or when the vehicle starts moving after stopping for greater than or equal to a predetermined time (for example 5 minutes to 20 minutes). 
     Next, at step S 202 , the first running distance estimating part  15  calculates the possible cruising distance of the surrounding vehicle. For example, when the surrounding vehicle is a vehicle powered by electricity (for example, a battery electric vehicle (BEV), plug-in hybrid electric vehicle (PHEV), etc.), the first running distance estimating part  15  calculates the possible cruising distance of the surrounding vehicle based on the SOC and the average electric power consumption in a predetermined time period of the surrounding vehicle. Specifically, the first running distance estimating part  15  calculates the possible cruising distance by multiplying the average electric power consumption with the amount of remaining electric power, which corresponds to the SOC. On the other hand, if the surrounding vehicle is a vehicle powered by fuel (for example, a gasoline engine vehicle, diesel engine vehicle, etc.), the first running distance estimating part  15  calculates the possible cruising distance of the surrounding vehicle based on the amount of remaining fuel and the average fuel consumption in a predetermined time period of the surrounding vehicle. Specifically, the first running distance estimating part  15  calculates the possible cruising distance by multiplying the average fuel consumption with the amount of remaining fuel. Note that, instead of the average electric power consumption or the average fuel consumption sent from the surrounding vehicle, a predetermined value may be used. 
     Next, at step S 203 , the first running distance estimating part  15  calculates the possible driving distance from the present time of the driver of the surrounding vehicle. For example, the first running distance estimating part  15  calculates the possible driving distance from the present time of the driver of the surrounding vehicle based on the continuous running time up to the present time of the surrounding vehicle and the speed of the surrounding vehicle. Specifically, the first running distance estimating part  15  calculates the possible driving distance from the present time by multiplying the vehicle speed with the value of a predetermined upper limit continuous running time (for example, 4 hours) minus the continuous running time up to the present time. Note that, in the latter half part of the upper limit continuous running time, the possibility of a rest stop rises, and therefore the latter half part may be weighted. In this case, for example, if the upper limit continuous running time is 4 (h), the weighting is 0.5, and the continuous running time up to the present time is 1 (h), the possible driving distance from the present time is calculated by multiplying the vehicle speed with 2 (h) (2 (h)+2 (h)×0.5−1 (h)). Further, if the set speed of the ACC in the surrounding vehicle is sent to the host vehicle through inter-vehicle communication, the set speed of the ACC at the surrounding vehicle may be used as the speed of the surrounding vehicle. 
     Further, the first running distance estimating part  15  may calculate the possible driving distance from the present time of the driver of the surrounding vehicle based on the continuous running distance up to the present time of the surrounding vehicle. In this case, the first running distance estimating part  15  calculates the possible driving distance from the present time by subtracting the continuous running distance up to the present time from a predetermined upper limit continuous running distance (for example 400 to 500 km). 
     Next, at step S 204 , the first running distance estimating part  15  estimates the continuous running distance from the present time of the surrounding vehicle based on the possible cruising distance of the surrounding vehicle and the possible driving distance from the present time of the driver of the surrounding vehicle. Specifically, the first running distance estimating part  15  sets the shorter distance of the possible cruising distance and the possible driving distance to the continuous running distance from the present time. 
     Next, at step S 205 , the followable distance estimating part  16  estimates the followable distance when the host vehicle follows the surrounding vehicle based on the continuous running distance from the present time of the surrounding vehicle. Specifically, the followable distance estimating part  16  sets the continuous running distance from the present time of the surrounding vehicle to the followable distance. 
     After step S 205 , the subroutine of  FIG.  5    ends and the present control routine proceeds to step S 105  of  FIG.  4   . At step S 105 , the preceding vehicle selecting part  17  judges whether the vehicle no. “i” is greater than or equal to N. If it is judged that the vehicle no. “i” is less than N, the present control routine returns to step S 103 , and then step S 104  is again executed to calculate the followable distance for another surrounding vehicle. 
     On the other hand, if at step S 105  it is judged that the vehicle no. “i” is greater than or equal to N, the present control routine proceeds to step S 106 . At step S 106 , the preceding vehicle selecting part  17  selects a preceding vehicle from among the N number of surrounding vehicles based on the followable distance. Specifically, the preceding vehicle selecting part  17  selects the surrounding vehicle with the longest followable distance among the N number of surrounding vehicles as the preceding vehicle. 
     Next, at step S 107 , the preceding vehicle selecting part  17  notifies the preceding vehicle to the occupant of the host vehicle (for example, the driver) through the HMI  8 . For example, if surrounding vehicles  30  of the host vehicle  20  are shown on a display of the HMI  8  as shown in  FIG.  2   , the preceding vehicle selecting part  17  displays the surrounding vehicle  30  selected as the preceding vehicle by a display mode different from the other surrounding vehicles  30  (for example, in transparency, brightness, color (hue), color lightness, color saturation, etc.) 
     Note that, in addition to visual notification or instead of visual notification, the preceding vehicle selecting part  17  may notify the occupant of the host vehicle of the timing of change of lane for moving behind the surrounding vehicle selected as the preceding vehicle by at least one of sound and vibration. For example, if a lane change to a right side lane is prompted by vibration, the preceding vehicle selecting part  17  uses a vibration unit of the HMI  8  to make a right half of a steering wheel of the host vehicle vibrate at the timing of the lane change. 
     Further, if the host vehicle is an automated vehicle in which all of the acceleration, steering, and deceleration (braking) of the vehicle are performed automatically, the preceding vehicle selecting part  17  may control the actuators  7  of the host vehicle so that the host vehicle follows the surrounding vehicle selected as the preceding vehicle. That is, the preceding vehicle selecting part  17  may automatically start a follow-up travel to the preceding vehicle. 
     Next, at step S 108 , the preceding vehicle selecting part  17  resets the vehicle no. “i” to zero. After step S 108 , the present control routine ends. 
     Note that, step S 203  of  FIG.  5    may be omitted and the first running distance estimating part  15  may calculate the possible cruising distance of the surrounding vehicle as the continuous running distance from the present time of the surrounding vehicle based on the SOC or the amount of remaining fuel of the surrounding vehicle. Further, step S 202  of  FIG.  5    may be omitted, and the first running distance estimating part  15  may calculate the possible driving distance from the present time of the driver of the surrounding vehicle as the continuous running distance from the present time of the surrounding vehicle based on the continuous running time or the continuous running distance up to the present time of the surrounding vehicle. 
     Second Embodiment 
     The configuration and control of the vehicle control system according to a second embodiment are basically similar to the configuration and control of the first embodiment except for the points explained below. Therefore, the second embodiment of the present invention will be explained focusing on parts different from the first embodiment. 
     As explained above, to enhance the effect of a follow-up travel, it is preferable to select a surrounding vehicle with a long followable distance as the preceding vehicle. However, a surrounding vehicle with a longest followable distance is not always optimal as the preceding vehicle. Therefore, in the second embodiment, an effect index representing the effect when the host vehicle follows a surrounding vehicle for a predetermined distance is calculated and the preceding vehicle is selected from among the plurality of surrounding vehicles based on the followable distance and the effect index. Due to this, it is possible to select the preceding vehicle more suited as the vehicle to be followed by the host vehicle. 
       FIG.  6    is a functional block diagram of the processor  13  of the ECU  10  in the second embodiment. In the second embodiment, the processor  13  has an effect index calculating part  18  in addition to the first running distance estimating part  15 , the followable distance estimating part  16 , and the preceding vehicle selecting part  17 . The first running distance estimating part  15 , the followable distance estimating part  16 , the preceding vehicle selecting part  17 , and the effect index calculating part  18  are function modules realized by a computer program stored in the memory  12  of the ECU  10  being run by the processor  13  of the ECU  10 . Note that, these function modules may be realized by dedicated processing circuits respectively provided at the processor  13 . 
     The effect index calculating part  18  calculates an effect index representing the effect when the host vehicle follows a surrounding vehicle for a predetermined distance based on the information relating to the surrounding vehicle for each of the plurality of surrounding vehicles. Further, in the second embodiment, the preceding vehicle selecting part  17  selects the preceding vehicle from among the plurality of surrounding vehicles based on the followable distances estimated by the followable distance estimating part  16  and the effect indexes calculated by the effect index calculating part  18 . 
     For example, the larger the degree of reduction of the air resistance by the follow-up travel, the greater the effect of improvement of the fuel consumption or electric power consumption by the follow-up travel. Further, if the relative speed of the host vehicle and a surrounding vehicle is small, following the surrounding vehicle becomes easier compared with if the relative speed is large. Further, the higher the stability of speed of a surrounding vehicle, the more it is possible to reduce the waste of electric power or fuel by acceleration and deceleration of the host vehicle at the time of the follow-up travel. For this reason, in the present embodiment, the effect index calculating part  18  calculates the effect index based on the degree of reduction of the air resistance by a follow-up travel to a surrounding vehicle, the relative speed of the host vehicle and the surrounding vehicle, and the stability of speed of the surrounding vehicle. 
       FIG.  7    is a flow chart showing a control routine of preceding vehicle selection processing in the second embodiment. The present control routine is repeatedly performed by the processor  13  of the ECU  10  at predetermined intervals. 
     Steps S 301  to S 304  are performed in the same way as steps S 101  to S 104  of  FIG.  4   . After step S 304 , at step S 305 , the subroutine shown in  FIG.  8    is performed.  FIG.  8    is a flow chart showing a control routine of effect index calculation processing in the second embodiment. 
     First, at step S 401 , the effect index calculating part  18  acquires information relating to the surrounding vehicle through inter-vehicle communication of the host vehicle and the surrounding vehicle. In the present embodiment, as information relating to the surrounding vehicle, the position, speed, width, and length of the surrounding vehicle, the operating state (on or off) of the ACC at the surrounding vehicle, etc. are acquired. 
     Next, at step S 402 , the effect index calculating part  18  calculates the relative speed of the host vehicle and the surrounding vehicle based on the information relating to the surrounding vehicle. Specifically, the effect index calculating part  18  calculates the relative speed between the host vehicle and the surrounding vehicle as the difference in the speed of the host vehicle and the speed of the surrounding vehicle detected by the speed sensors of the vehicle state detection devices  6  (relative speed=|speed of host vehicle−speed of surrounding vehicle|). Note that, as the speed of the host vehicle, the set speed of the ACC set by an occupant of the host vehicle (for example, the driver) may be used. Further, if the set speed of the ACC at the surrounding vehicle is sent to the host vehicle through inter-vehicle communication, the set speed of the ACC at the surrounding vehicle may be used as the speed of the surrounding vehicle. 
     Next, at step S 403 , the effect index calculating part  18  calculates the degree of reduction of the air resistance due to a follow-up travel to the surrounding vehicle based on the information relating to the surrounding vehicle. For example, the effect index calculating part  18  calculates an estimated value of the front projected area of the surrounding vehicle based on the width and length of the surrounding vehicle, and calculates the degree of reduction of the air resistance based on this estimated value and the speed of the surrounding vehicle. In this case, the larger the estimated value of the front projected area, the larger the degree of reduction of the air resistance is made. Note that, information on the type of application of the surrounding vehicle (for example, a motor vehicle for a passenger transport business, a motor vehicle for a freight transport business, etc.) and information on the type of size (for example, a large sized motor vehicle, medium size motor vehicle, ordinary motor vehicle, etc.) may be sent to the host vehicle through inter-vehicle communication, and the effect index calculating part  18  may calculate the degree of reduction of the air resistance based on the information on the type of application and information on the type of size. 
     Next, at step S 404 , the effect index calculating part  18  calculates the degree of speed stability of the surrounding vehicle based on information relating to the surrounding vehicle. For example, the effect index calculating part  18  calculates the degree of speed stability of the surrounding vehicle based on the operating state of the ACC in the surrounding vehicle. In this case, if the operating state of the ACC is ON, the degree of speed stability of the surrounding vehicle is made higher compared with if the operating state of the ACC is OFF. Note that, the effect index calculating part  18  may calculate the degree of speed stability of the surrounding vehicle based on the history of the speed of the surrounding vehicle (for example, the amount of change of the speed in a predetermined time period) etc. 
     Next, at step S 405 , the effect index calculating part  18  uses a map or calculation formula to calculate the effect index for an i-th surrounding vehicle based on the relative speed, the degree of reduction of the air resistance, and the degree of stability of the vehicle speed. At this time, the smaller the relative speed, the higher the effect index is made, the larger the degree of reduction of the air resistance, the higher the effect index is made, and the higher the degree of stability of the vehicle speed, the higher the effect index is made. For example, the effect index is classified as ranks A to E. If the rank is A, the effect index becomes the highest, while if the rank is E, the effect index becomes the lowest. 
     Note that, the effect index calculating part  18  may correct the effect index based on information on the preference of the occupant of the host vehicle relating to the selection of the preceding vehicle. In this case, the preference information is registered in advance by the occupant of the host vehicle and stored in the memory  12  etc. of the ECU  10 . For example, as preference information, the occupant of the host vehicle inputs to the HMI  8  whether or not he or she permits following a large sized vehicle such as a bus or truck, whether he or she permits a lane change of the host vehicle for a follow-up travel, etc. In this case, if following a large sized vehicle is not permitted, the effect index is corrected so that the effect index becomes lower for a surrounding vehicle which is a large sized vehicle (for example, the effect index is made zero). Further, if a lane change of the host vehicle for a follow-up travel is not permitted, the effect index is corrected so that the effect index becomes lower for a surrounding vehicle running in a lane different from the host vehicle (for example, the effect index is made zero). 
     After step S 405 , the subroutine of  FIG.  8    is ended and the present control routine proceeds to S 306  of  FIG.  7   . At step S 306 , the preceding vehicle selecting part  17  judges whether the vehicle no. “i” is greater than or equal to N. If it is judged that the vehicle no. “i” is less than N, the present control routine returns to step S 303  and steps S 304  and S 305  are again performed for calculating the followable distance and the effect index for another surrounding vehicle. 
     On the other hand, if at step S 306  it is judged that the vehicle no. “i” is greater than or equal to N, the present control routine proceeds to step S 307 . At step S 307 , the preceding vehicle selecting part  17  selects the preceding vehicle from among the N number of surrounding vehicles based on the followable distances and the effect indexes. For example, the preceding vehicle selecting part  17  determines an evaluation value based on the followable distance and the effect index for each of the N number of surrounding vehicles and selects as the preceding vehicle the surrounding vehicle with the highest evaluation value among the N number of surrounding vehicles. 
     The evaluation value is, for example, determined using a table such as shown in  FIG.  9   .  FIG.  9    is a view showing one example of the table for determining the evaluation value for surrounding vehicles. In the example of  FIG.  9   , the values of the followable distances are laid out on the vertical while the ranks of the effect index are laid out on the horizontal. As shown in  FIG.  9   , the evaluation value is made higher the longer the followable distance and is made higher the higher the effect index. Note that, the effect index may be calculated as a numerical value and the evaluation value may be determined based on the followable distance and the effect index using a map or calculation formula. 
     Next, in the same way as steps S 107  and S 108  of  FIG.  4   , at step S 308 , the preceding vehicle selecting part  17  notifies the preceding vehicle to the occupant of the host vehicle, and at step S 309 , the preceding vehicle selecting part  17  resets the vehicle no. “i” to zero. After step S 309 , the present control routine ends. 
     Third Embodiment 
     The configuration and control of the according to a third embodiment are basically similar to the configuration and control of the vehicle control system according to the second embodiment except for the points explained below. Therefore, the third embodiment of the present invention will be explained focusing on parts different from the second embodiment. 
     In the first embodiment and the second embodiment, to estimate the followable distance when the host vehicle follows a surrounding vehicle, the continuous running distance from the present time of the surrounding vehicle is estimated. However, there is a possibility of the host vehicle stopping before the surrounding vehicle for recharging, refueling, rest, etc. In this case, the followable distance is limited by the continuous running distance from the present time of the host vehicle. Therefore, in the third embodiment, the followable distance is estimated based on the continuous running distance from the present time of the surrounding vehicle and the continuous running distance from the present time of the host vehicle. By doing this, it is possible to more precisely estimate the followable distance and in turn possible to select a more suitable preceding vehicle to be followed by the host vehicle. 
       FIG.  10    is a functional block diagram of the processor  13  of the ECU  10  in the third embodiment. In the third embodiment, the processor  13  has a second running distance estimating part  19  in addition to the first running distance estimating part  15 , the followable distance estimating part  16 , the preceding vehicle selecting part  17 , and the effect index calculating part  18 . The first running distance estimating part  15 , the followable distance estimating part  16 , the preceding vehicle selecting part  17 , the effect index calculating part  18 , and the second running distance estimating part  19  are function modules realized by a computer program stored in the memory  12  of the ECU  10  being run by the processor  13  of the ECU  10 . Note that, these function modules may respectively be realized by dedicated processing circuits provided in the processor  13 . 
     The second running distance estimating part  19  estimates the continuous running distance from the present time of the host vehicle based on information relating to the host vehicle. For example, the information relating to the host vehicle includes at least one of the SOC or the amount of remaining fuel of the host vehicle and the continuous running time or the continuous running distance up to the present time of the host vehicle. That is, the second running distance estimating part  19  estimates the continuous running distance from the present time of the host vehicle based on at least one of the SOC or the amount of remaining fuel of the host vehicle and the continuous running time or the continuous running distance up to the present time of the host vehicle. By doing this, it is possible to estimate the continuous running distance from the present time of the host vehicle without forcing upon the occupant of the host vehicle the input of detailed driving plans including the rest stop and the destination. 
     The continuous running distance from the present time of the host vehicle is estimated as follows in the same way as the continuous running distance from the present time of a surrounding vehicle. That is, to estimate the continuous running distance from the present time of the host vehicle, the second running distance estimating part  19  calculates the possible cruising distance of the host vehicle based on the SOC or the amount of remaining fuel of the host vehicle and calculates the possible driving distance from the present time of the driver of the host vehicle based on the continuous running time or the continuous running distance up to the present time of the host vehicle. Further, the second running distance estimating part  19  estimates the continuous running distance from the present time of the host vehicle by comparing the possible cruising distance of the host vehicle and the possible driving distance from the present time of the driver of the host vehicle. Specifically, the second running distance estimating part  19  sets the shorter distance among the possible cruising distance and the possible driving distance to the continuous running distance from the present time of the host vehicle. 
     Further, in the third embodiment, the followable distance estimating part  16  estimates the followable distance when the host vehicle follows a surrounding vehicle based on the continuous running distance from the present time of the surrounding vehicle and the continuous running distance from the present time of the host vehicle for each of a plurality of surrounding vehicles. Specifically, the followable distance estimating part  16  sets the shorter distance among the continuous running distance from the present time of the surrounding vehicle and the continuous running distance from the present time of the host vehicle as the followable distance. 
     In the third embodiment, the control routine of  FIG.  7    is performed in the same way as the second embodiment. At step S 304 , instead of the subroutine shown in  FIG.  5   , the subroutine shown in  FIG.  11    is performed.  FIG.  11    is a flow chart showing a control routine of followable distance estimation processing in the third embodiment. 
     First, at step S 501 , the second running distance estimating part  19  calculates the possible cruising distance of the host vehicle. For example, if the host vehicle is a vehicle powered by electricity (for example, a battery electric vehicle (BEV), plug-in hybrid electric vehicle (PHEV), etc.), the second running distance estimating part  19  calculates the possible cruising distance of the host vehicle based on the SOC and the average electric power consumption in a predetermined time period of the host vehicle. Specifically, the second running distance estimating part  19  multiplies the average electric power consumption with the amount of remaining electric power, which corresponds to the SOC, to thereby calculate the possible cruising distance. The SOC of the host vehicle is, for example, calculated based on the voltage and temperature of the battery or the input/output current of the battery detected by the battery sensor of the vehicle state detection device  6 . On the other hand, if the host vehicle is a vehicle powered by fuel (for example, a gasoline engine vehicle, diesel engine vehicle, etc.), the second running distance estimating part  19  calculates the possible cruising distance of the host vehicle based on the amount of remaining fuel of the host vehicle and the average fuel consumption in a predetermined time period. Specifically, the second running distance estimating part  19  multiplies the average fuel consumption with the amount of remaining fuel to thereby calculate the possible cruising distance. 
     Next, at step S 502 , the second running distance estimating part  19  calculates the possible driving distance from the present time of the driver of the host vehicle. For example, the second running distance estimating part  19  calculates the possible driving distance from the present time of the driver of the host vehicle based on the continuous running time from the present time of the host vehicle and the vehicle speed of the host vehicle. Specifically, the second running distance estimating part  19  multiples the value of the predetermined upper limit continuous running time (for example, 4 hours) minus the continuous running time up to the present time with the vehicle speed to thereby calculate the possible driving distance from the present time. Note that, since in the second half part of the upper limit continuous running time, the possibility of a rest stop rises, the second half part may be weighted. Further, as the speed of the host vehicle, the set speed of the ACC may be used. 
     Further, the second running distance estimating part  19  may calculate the possible driving distance from the present time of the driver of the host vehicle based on the continuous running distance up to the present time of the host vehicle. In this case, the second running distance estimating part  19  calculates the possible driving distance from the present time by subtracting the continuous running distance up to the present time from a predetermined upper limit continuous running distance (for example 400 to 500 km). 
     Next, at step S 503 , the second running distance estimating part  19  estimates the continuous running distance from the present time of the host vehicle based on the possible cruising distance of the host vehicle and the possible driving distance from the present time of the driver of the host vehicle. Specifically, the second running distance estimating part  19  sets the shorter distance among the possible cruising distance and the possible driving distance to the continuous running distance from the present time. 
     Next, steps S 504  to S 507  are performed in the same way as steps S 201  to S 204  of  FIG.  5   . After step S 507 , at step S 508 , the followable distance estimating part  16  estimates the followable distance when the host vehicle follows a surrounding vehicle based on the continuous running distance from the present time of the surrounding vehicle and the continuous running distance from the present time of the host vehicle. Specifically, the followable distance estimating part  16  sets the shorter distance among the continuous running distance from the present time of the surrounding vehicle and the continuous running distance from the present time of the host vehicle to the followable distance. After step S 508 , the subroutine of  FIG.  11    ends and, as explained above relating to the second embodiment, steps S 306  to S 309  of  FIG.  7    are performed. 
     Fourth Embodiment 
     The configuration and control of the vehicle control system according to a fourth embodiment are basically similar to the configuration and control of the vehicle control system according to the first embodiment except for the points explained below. Therefore, the fourth embodiment of the present invention will be explained focusing on parts different from the first embodiment. 
       FIG.  12    is a schematic view of the configuration of a client-server system  100  including a preceding vehicle selection device according to the fourth embodiment of the present invention. The client-server system  100  is provided with a server  40  and a plurality of vehicles  50 . The server  40  can communicate with each of the plurality of vehicles  50  through a communication network  60  like a carrier network or an Internet network and a wireless base station  70 . That is, the server  40  can communicate with each of the plurality of vehicles  50  through wide area communication. 
       FIG.  13    is a view schematically showing the configuration of the server  40 . The server  40  is provided with a communication interface  41 , a storage device  42 , a memory  43 , and a processor  44 . The communication interface  41 , the storage device  42 , and the memory  43  are connected with the processor  44  through signal wires. Note that, the server  40  may further be provided with an input device such as a keyboard and mouse, an output device such as a display, etc. Further, the server  40  may be configured from a plurality of computers. 
     The communication interface  41  has an interface circuit for connecting the server  40  to the communication network  60 . The server  40  communicates with the outside of the server  40  (for example, the plurality of vehicles  50 ) through the communication network  60 . The communication interface  41  is one example of a communicating part of the server  40 . 
     The storage device  42 , for example, has a hard disk drive (HDD), a solid state drive (SDD), or an optical recording medium and its access device. The storage device  42  stores various types of data, for example, stores map information, information of a plurality of vehicles  50  (identification information, positional information, etc.), a computer program for the processor  44  to perform various types of processing, etc. The storage device  42  is one example of a storage part of the server  40 . 
     The memory  43  has a volatile semiconductor memory (for example, RAM). The memory  43 , for example, temporarily stores the various types of data etc. used when various types of processing are performed by the processor  44 . The memory  43  is another example of a storage part of the server  40 . 
     The processor  44  has one or more CPUs and their peripheral circuits. Note that, the processor  44  may further have a logic unit, an arithmetic unit, or a graphic unit or other such processing circuit. 
     In the fourth embodiment, the server  40  functions as the preceding vehicle selection device instead of the ECU  10 . The processor  44  of the server  40  has a first running distance estimating part  15 , a followable distance estimating part  16 , and a preceding vehicle selecting part  17 . In this case, the first running distance estimating part  15 , the followable distance estimating part  16 , and the preceding vehicle selecting part  17  are function modules realized by a computer program stored in the storage device  42  of the server  40  being run by the processor  44  of the server  40 . 
     Therefore, in the fourth embodiment, the control routine of the preceding vehicle selection processing of  FIG.  4    is performed by the processor  44  of the server  40 . First, at step S 101 , the preceding vehicle selecting part  17  judges whether a start condition of a follow-up travel is satisfied in any of the vehicles  50  in the plurality of vehicles  50 . If this judgment is affirmative, in the following processing step, the vehicle  50  which satisfies the start condition of a follow-up travel is recognized as a host vehicle. 
     At step S 102 , the preceding vehicle selecting part  17  identifies the number N of surrounding vehicles positioned around the host vehicle (for example, in predetermined ranges in front of and in back of the host vehicle) based on the position information of the plurality of vehicles  50  including the host vehicle and assigns vehicle nos. ( 1  to N) to the respective N number of surrounding vehicles. 
     Next, at step S 103 , the preceding vehicle selecting part  17  adds “1” to the vehicle no. “i”. Note that, the initial value of the vehicle no. “i” is zero. 
     Next, at step S 304 , the subroutine shown in  FIG.  5    is performed. 
     First, at step S 201 , the first running distance estimating part  15  acquires information relating to each surrounding vehicle through wide area communication between the server  40  and the surrounding vehicles. In the present embodiment, as information relating to the surrounding vehicle, the position, speed, a SOC, or an amount of remaining fuel of the surrounding vehicle, the continuous running time or the continuous running distance up to the present time, the average electric power consumption or the average fuel consumption in a predetermined time period etc. are sent from the surrounding vehicle to the server  40 . After step S 201 , steps S 202  to S 205  are performed in the same way as the first embodiment. 
     After step S 205 , the subroutine of  FIG.  5    ends and the present control routine proceeds to step S 105  of  FIG.  4   . Steps S 105  and S 106  are performed in the same way as the first embodiment. After step S 106 , at step S 107 , the preceding vehicle selecting part  17  notifies the preceding vehicle to the occupant of the host vehicle. Specifically, the preceding vehicle selecting part  17  sends information relating to the preceding vehicle (for example, the positional information of the preceding vehicle etc.) to the host vehicle. As a result, the ECU  10  of the host vehicle notifies the preceding vehicle to the occupant of the host vehicle through the HMI  8 . That is, the preceding vehicle selecting part  17  notifies the preceding vehicle to the occupant of the host vehicle through the ECU  10  of the host vehicle. 
     Next, at step S 108 , the preceding vehicle selecting part  17  resets the vehicle no. “i” to zero. After step S 108 , the present control routine ends. 
     Above, preferred embodiments according to the present invention were explained, but the present invention is not limited to these embodiments and can be corrected and changed in various ways within the language of the claims. For example, the vehicle at which the vehicle control system  1  is provided may be a manually driven vehicle not having driver assistance functions. 
     Further, the computer program for making the functions of the different parts of the processor  13  of the ECU  10  or the processor  44  of the server  40  be realized by a computer may be provided in a form stored in a computer readable recording medium. The computer readable recording medium is, for example, a magnetic recording medium, an optical recording medium, or a semiconductor memory. 
     Further, the above-mentioned embodiments can be worked combined in any way. In the case where the second embodiment or the third embodiment and the fourth embodiment are combined, the processing performed by the ECU  10  in the second embodiment or the third embodiment is performed by the server  40 . 
     REFERENCE SIGNS LIST 
     
         
         
           
               10  electronic control unit (ECU) 
               13  processor 
               15  first running distance estimating part 
               16  followable distance estimating part 
               17  preceding vehicle selecting part 
               20  host vehicle 
               30  surrounding vehicle 
               40  server 
               44  processor