Patent Publication Number: US-2021170942-A1

Title: Autonomous driving vehicle information presentation apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an autonomous driving vehicle information presentation apparatus that presents suitable information from an autonomous driving vehicle to a traffic participant present around the vehicle. 
     2. Description of the Related Art 
     Recently, autonomous driving techniques have been vigorously proposed to achieve safe and comfortable driving of a vehicle while reducing the burden on the driver. 
     The applicant of the present application has disclosed an invention of a vehicle control system as an example of the autonomous driving technique that includes a detection unit that detects the state of surroundings of a vehicle; an autonomous driving control unit that executes autonomous driving which autonomously controls as least one of the speed and steering of the vehicle based on the state of the surroundings of the vehicle detected by the detection unit; a recognition unit that recognizes the direction of a person from the vehicle based on the state of the surroundings of the vehicle detected by the detection unit; and an output unit that outputs information being recognizable by the person recognized by the recognition unit and having directivity in the direction of the person recognized by recognition unit (see Patent Literature 1). 
     In the invention of the vehicle control system according to Patent Literature 1, information is outputted which is recognizable by a person recognized by the recognition unit and has directivity in the direction of the recognized person. This can reduce a sense of unease that the host vehicle may give to a person present around it. 
     Patent Literature 2 discloses an invention of a traffic signal display apparatus that displays the traffic signal display state of a traffic light present ahead of the host vehicle to a vehicle traveling behind the host vehicle. 
     In the invention of the traffic signal display apparatus according to Patent Literature 2, the traffic signal display state of a traffic light present ahead of the host vehicle is displayed to the vehicle traveling behind. This can reliably notify the occupant in the vehicle traveling behind (hereinafter also referred to as “trailing vehicle”) of the traffic signal display state of the traffic light and reduce a sense of unease that may be felt by the occupant in the vehicle traveling behind. 
     PRIORITY DOCUMENT(S) 
     Patent Literature(s) 
     Patent Literature 1: JP 2017-199317 A 
     Patent Literature 2: JP 03-235200 A 
     SUMMARY OF THE INVENTION 
     However, even with the inventions according to Patent Literatures 1 and 2, there is still a possibility that the autonomous driving vehicle may fail to appropriately present the information to the trailing vehicle depending, for example, on the magnitude of the vehicle-to-vehicle distance between the autonomous driving vehicle and the trailing vehicle and thus give a sense of unease to traffic participants present around the vehicle. 
     The present invention has been made in view of the above circumstances and makes it an object thereof to provide an autonomous driving vehicle information presentation apparatus that enables an autonomous driving vehicle to further reduce a sense of unease which the vehicle may give to a traffic participant present around it. 
     In order to solve the above-described problem, an autonomous driving vehicle information presentation apparatus according to a present invention (1) is an autonomous driving vehicle information presentation apparatus that is used in an autonomous driving vehicle which obtains outside information on an outside including a leading vehicle present ahead of a host vehicle in a direction of advance and autonomously controls at least one of speed and steering of the host vehicle based on the obtained outside information, and that presents information to a traffic participant present around the host vehicle. A main characteristic feature of the autonomous driving vehicle information presentation apparatus is that it comprises: an outside information obtaining unit that obtains the outside information on the outside including a trailing vehicle present behind the host vehicle in the direction of advance; a determination unit that determines presence of the trailing vehicle following the host vehicle, based on the outside information; a calculation unit that calculates a host vehicle-trailing vehicle distance being a distance between the host vehicle and the trailing vehicle, when the determination unit determines that the trailing vehicle is present; and an information presentation unit that presents information addressed to the trailing vehicle by using an exterior display apparatus provided at a position in a rear portion of a cabin of the host vehicle at which the exterior display apparatus is visible to an occupant in the trailing vehicle, in which the information presentation unit sets a presented state of the information addressed to the trailing vehicle according to a magnitude of the host vehicle-trailing vehicle distance calculated by the calculation unit. 
     According to the present invention, an autonomous driving vehicle can further reduce a sense of unease which the vehicle may give to a traffic participant present around it. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an entire configuration diagram of an autonomous driving vehicle including an information presentation apparatus according to an embodiment of the present invention. 
         FIG. 2  is a functional block configuration diagram illustrating a vehicle control apparatus including an autonomous driving vehicle information presentation apparatus and its peripheral components according to an embodiment of the present invention. 
         FIG. 3  is a schematic configuration diagram of a human machine interface (HMI) included in the autonomous driving vehicle information presentation apparatus. 
         FIG. 4  is a diagram illustrating a front structure of the cabin of the autonomous driving vehicle. 
         FIG. 5A  is an exterior diagram illustrating a front structure of the autonomous driving vehicle. 
         FIG. 5B  is an exterior diagram illustrating a rear structure of the autonomous driving vehicle. 
         FIG. 5C  is a front view illustrating a schematic configuration of a right front light unit included in the autonomous driving vehicle. 
         FIG. 6  is a block configuration diagram conceptually illustrating functions of the autonomous driving vehicle information presentation apparatus. 
         FIG. 7  is a flowchart to be used to describe the operation of the autonomous driving vehicle information presentation apparatus. 
         FIG. 8A  is a diagram illustrating a traveling scene of the autonomous driving vehicle equipped with the autonomous driving vehicle information presentation apparatus according to a first example. 
         FIG. 8B  is a diagram illustrating an information presenting state of the autonomous driving vehicle information presentation apparatus according to the first example. 
         FIG. 9A  is a diagram illustrating a traveling scene of the autonomous driving vehicle equipped with the autonomous driving vehicle information presentation apparatus according to a second example. 
         FIG. 9B  is a diagram illustrating an information presenting state of the autonomous driving vehicle information presentation apparatus according to the second example. 
         FIG. 9C  is a diagram illustrating a modification of the information presenting state of the autonomous driving vehicle information presentation apparatus according to the second example. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Autonomous driving vehicle information presentation apparatuses according to embodiments of the present invention will be hereinafter described in detail with reference to the drawings. 
     Note that, in the drawings be presented below, members having the same function are denoted by the same reference sign. Moreover, the sizes and shapes of members may be changed or exaggerated and schematically illustrated for convenience of explanation. 
     When the terms “left” and “right” are used in relation to a host vehicle M in the description of the vehicle control apparatuses according to the embodiments of the present invention, the front side of the host vehicle M in the direction of advance is the reference direction. Specifically, in a case where the host vehicle M is, for example, right-hand drive, the driver&#39;s seat side will be referred to as the right side, and the passenger&#39;s seat side will be referred to as the left side. 
     [Configuration of Host Vehicle M] 
     First of all, a configuration of an autonomous driving vehicle (hereinafter also referred to as “host vehicle”) M including a vehicle control apparatus  100  according to an embodiment of present invention will be described with reference to  FIG. 1 . 
       FIG. 1  is an entire configuration diagram of the autonomous driving vehicle M including the vehicle control apparatus  100  according to the embodiment of the present invention. 
     As illustrated in  FIG. 1 , the host vehicle M equipped with the vehicle control apparatus  100  according to the embodiment of the present invention is an automobile, such as a two-wheeled, three-wheeled, or four-wheeled automobile, for example. 
     The host vehicle M includes an automobile with an internal combustion engine such as a diesel engine or a gasoline engine as a power source, an electric automobile with an electric motor as a power source, a hybrid automobile with both an internal combustion engine and an electric motor, and the like. Of these, the electric automobile is driven using electric power discharged from a cell such as a secondary cell, a hydrogen fuel cell, a metal fuel cell, or an alcohol fuel cell, for example. 
     As illustrated in  FIG. 1 , the host vehicle M is equipped with: an external sensor  10  having a function of detecting outside information on targets including objects and signs present around the host vehicle M; a navigation apparatus  20  having a function of mapping the current position of the host vehicle M onto a map, guiding the host vehicle M to a destination through a route, and so on; and the vehicle control apparatus  100  having a function of controlling self-driving of the host vehicle M including the steering and the acceleration and deceleration of the host vehicle M and so on. 
     These apparatuses and instruments are configured such that they are connected so as to be capable of communicating data to each other through a communication medium such as a controller area network (CAN), for example. 
     Note that the “vehicle control apparatus” may include other components (such as the external sensor  10  and an HMI  35 ) in addition to the components of the “vehicle control apparatus  100 ” according to this embodiment. 
     [External Sensor  10 ] 
     The external sensor  10  is configured of cameras  11 , radars  13 , and lidars  15 . 
     The cameras  11  have an optical axis orientated toward the front side of the host vehicle and tilted obliquely downward, and has a function of capturing an image in the direction of advance of the host vehicle M. In an example, complementary metal oxide semiconductor (CMOS) cameras, charge coupled device (CCD) cameras, or the like can be used as the cameras  11  as appropriate. The cameras  11  are provided near the rearview mirror (not illustrated) inside the cabin of the host vehicle M and on a front portion of a right door and a front portion of a left door outside the cabin of the host vehicle M, or the like. 
     The cameras  11  repetitively capture images of, for example, a front side in the direction of advance, a right rear side, and a left rear side relative to the host vehicle M on a periodic basis. In this embodiment, the camera  11  provided near the rearview mirror is a pair of monocular cameras arranged side by side. The camera  11  may be a stereo camera. 
     The pieces of image information on the front side in the direction of advance, the right rear side, and the left rear side relative to the host vehicle M captured by the cameras  11  are transmitted to the vehicle control apparatus  100  through the communication medium. 
     The radars  13  have a function of obtaining distribution information on targets including a leading vehicle being a following target traveling ahead of the host vehicle M by emitting radar waves to the targets and receiving the radar waves reflected by the targets, the distribution information including the distances to the targets and the orientations of the targets. Laser beams, microwaves, millimeter waves, ultrasonic waves, or the like can be used as the radar waves as appropriate. 
     In this embodiment, five radars  13  are provided, three on the front side and two on the rear side, as illustrated in  FIG. 1 . The target distribution information obtained by the radars  13  is transmitted to the vehicle control apparatus  100  through the communication medium. 
     The lidars  15  (Light Detection and Ranging) have a function of detecting the presence of a target and the distance to a target by, for example, measuring the time taken to detect scattered light of emitted light. In this embodiment, five lidars  15  are provided, two on the front side and three on the rear side, as illustrated in  FIG. 1 . The target distribution information obtained by the lidars  15  is transmitted to the vehicle control apparatus  100  through the communication medium. 
     [Navigation Apparatus  20 ] 
     The navigation apparatus  20  is configured of a global navigation satellite system (GNSS) receiver, map information (navigation map), a touchscreen-type interior display apparatus  61  functioning as a human machine interface, speakers  63  (see  FIG. 3  for these two), a microphone, and so on. The navigation apparatus  20  serves to locate the current position of the host vehicle M with the GNSS receiver and also to derive a route from the current position to a destination designated by the user. 
     The route derived by the navigation apparatus  20  is provided to a target lane determination unit  110  (described later) of the vehicle control apparatus  100 . The current position of the host vehicle M may be identified or complemented by an inertial navigation system (INS) utilizing the outputs of a vehicle sensor  30  (see  FIG. 2 ). Also, while the vehicle control apparatus  100  is executing a manual driving mode, the navigation apparatus  20  navigates through a route to a destination by using sound and voice or by displaying a map. 
     Note that the function of locating the current position of the host vehicle M may be provided independently of the navigation apparatus  20 . Also, the navigation apparatus  20  may be implemented by a function of a terminal apparatus such as a smartphone or tablet carried by the user, for example. In this case, information is transmitted and received between the terminal apparatus and the vehicle control apparatus  100  via wireless or wired communication. 
     [Vehicle Control Apparatus  100  and its Peripheral Components] 
     Next, the vehicle control apparatus  100  and its peripheral components mounted on the host vehicle M according to an embodiment of the present invention will be described with reference to  FIG. 2 . 
       FIG. 2  is a functional block configuration diagram illustrating the vehicle control apparatus  100  and its peripheral components according to the embodiment of the present invention. 
     As illustrated in  FIG. 2 , the host vehicle M is equipped with a communication apparatus  25 , the vehicle sensor  30 , the HMI  35 , a travel drive force output apparatus  200 , a steering apparatus  210 , and a brake apparatus  220 , as well as the above-described external sensor  10 , navigation apparatus  20 , and vehicle control apparatus  100 . 
     The communication apparatus  25 , the vehicle sensor  30 , the HMI  35 , the travel drive force output apparatus  200 , the steering apparatus  210 , and the brake apparatus  220  are configured such that they are connected to the vehicle control apparatus  100  so as to be capable of communicating data to and from the vehicle control apparatus  100  through the communication medium. 
     [Communication Apparatus  25 ] 
     The communication apparatus  25  has a function of performing communication through a wireless communication medium such as a cellular network, a Wi-Fi network, Bluetooth (registered trademark), or a dedicated short range communication (DSRC), for example. 
     The communication apparatus  25  wirelessly communicates with, for example, an information providing server of a system that monitors the traffic situations of roads, such as the Vehicle Information and Communication System (VICS) (registered trademark), and obtains traffic information indicating the traffic situation of the road which the host vehicle M is currently traveling or a road which the host vehicle M will be traveling. The traffic information contains pieces of information such as information on congestion ahead, information on the times required to pass through congested areas, information on accidents, failed vehicles, and construction, information on speed restrictions and lane closures, information on the locations of parking lots, and information on the availability of parking lots and rest areas. 
     The communication apparatus  25  may obtain the traffic information by, for example, communicating with a radio beacon provided on a side margin of the road or the like or performing vehicle-to-vehicle communication with another vehicle traveling around the host vehicle M. 
     The communication apparatus  25  also wirelessly communicates with, for example, an information providing server of the Traffic Signal Prediction Systems (TSPS) and obtains traffic signal information on traffic lights provided on the road which the host vehicle M is currently traveling or a road which the host vehicle M will be traveling. The TSPS serves to assist driving to smoothly cross intersections with traffic lights by using the traffic signal information on the traffic lights. 
     The communication apparatus  25  may obtain the traffic signal information by, for example, communicating with an optical beacon provided on a side margin of the road or the like or performing vehicle-to-vehicle communication with another vehicle traveling around the host vehicle M. 
     [Vehicle Sensor  30 ] 
     The vehicle sensor  30  has a function of detecting various pieces of information on the host vehicle M. The vehicle sensor  30  includes: a vehicle speed sensor that detects the vehicle speed of the host vehicle M; an acceleration sensor that detects the acceleration of the host vehicle M; a yaw rate sensor that detects the angular speed of the host vehicle M about a vertical axis; an orientation sensor that detects the orientation of the host vehicle M; a tilt angle sensor that detects the tilt angle of the host vehicle M; an illuminance sensor that detects the illuminance of the area where the host vehicle M is present; a raindrop sensor that detects the amount of raindrops at the area where the host vehicle M is present; and so on. 
     [Configuration of HMI  35 ] 
     Next, the HMI  35  will be described with reference to  FIGS. 3, 4, 5A, and 5B . 
       FIG. 3  is a schematic configuration diagram of the HMI  35  connected to the vehicle control apparatus  100  according to an embodiment of the present invention.  FIG. 4  is a diagram illustrating a front structure of the cabin of the vehicle M including the vehicle control apparatus  100 .  FIGS. 5A and 5B  are exterior diagrams illustrating a front structure and a rear structure of the vehicle M including the vehicle control apparatus  100 , respectively. 
     As illustrated in  FIG. 3 , the HMI  35  includes constituent members of a driving operation system and constituent members of a non-driving operation system. There is no clear boundary between them, and a configuration in which constituent members of the driving operation system includes functions of the non-driving operation system (or vice versa) may be employed. 
     As illustrated in  FIG. 3 , the HMI  35  includes, as the constituent members of the driving operation system; an accelerator pedal  41 , an accelerator position sensor  43 , and an accelerator pedal counter force output apparatus  45 ; a brake pedal  47  and a brake depression amount sensor  49 ; a shift lever  51  and a shift position sensor  53 ; a steering wheel  55 , a steering angle sensor  57  and a steering torque sensor  58 ; and other driving operation devices  59 . 
     The accelerator pedal  41  is an acceleration operator that receives an acceleration instruction (or a deceleration instruction with a returning operation) by the driver. The accelerator position sensor  43  detects the amount of depression of the accelerator pedal  41  and outputs an accelerator position signal indicating the amount of the depression to the vehicle control apparatus  100 . 
     Note that a configuration may be employed which, instead of outputting the accelerator position signal to the vehicle control apparatus  100 , outputs the accelerator position signal directly to the travel drive force output apparatus  200 , the steering apparatus  210 , or the brake apparatus  220 . This applies also to the other components of the driving operation system to be described below. The accelerator pedal counterforce output apparatus  45  outputs a force (operation counterforce) to the accelerator pedal  41  in the opposite direction from the direction in which the accelerator pedal  41  is operated, for example, in accordance with an instruction from the vehicle control apparatus  100 . 
     The brake pedal  47  is a deceleration operator that receives a deceleration instruction by the driver. The brake depression amount sensor  49  detects the amount of depression of (or the force of depression on) the brake pedal  47 , and outputs a brake signal indicating the result of the detection to the vehicle control apparatus  100 . 
     The shift lever  51  is a gearshift operator that receives a shift stage change instruction by the driver. The shift position sensor  53  detects a shift stage designated by the driver and outputs a shift position signal indicating the result of the detection to the vehicle control apparatus  100 . 
     The steering wheel  55  is a steering operator that receives a turn instruction by the driver. The steering angle sensor  57  detects the steering angle of the steering wheel  55 , and outputs a steering angle signal indicating the result of the detection to the vehicle control apparatus  100 . The steering torque sensor  58  detects torque applied to the steering wheel  55 , and outputs a steering torque signal indicating the result of the detection to the vehicle control apparatus  100 . 
     The steering wheel  55  corresponds to a “driving operator” in the present invention. 
     The other driving operation devices  59  are, for example, a joystick, buttons, a rotary switch, a graphical user interface (GUI) switch, and so on. The other driving operation devices  59  receive an acceleration instruction, a deceleration instruction, a turn instruction, and so on and output them to the vehicle control apparatus  100 . 
     As illustrated in  FIG. 3 , the HMI  35  includes, as the constituent members of the non-driving operation system: the interior display apparatus  61 ; the speakers  63 ; a contacting operation detection apparatus  65  and a content playback apparatus  67 ; various operation switches  69 ; seats  73  and a seat drive apparatus  75 ; glass windows  77  and a window drive apparatus  79 ; an in-cabin camera  81 ; and an exterior display apparatus  83 , for example. 
     The interior display apparatus  61  is a display apparatus preferably of a touchscreen type having a function of displaying various pieces of information to the occupants in the cabin. As illustrated in  FIG. 4 , the interior display apparatus  61  includes, in an instrument panel  60 : a meter panel  85  provided at a position directly opposite the driver&#39;s seat; a multi-information panel  87  horizontally elongated in the vehicle width direction (the Y-axis direction in  FIG. 4 ) and provided so as to face the driver&#39;s seat and the passenger&#39;s seat; a right panel  89   a  provided on the driver&#39;s seat side in the vehicle width direction; and a left panel  89   b  provided on the passenger&#39;s seat side in the vehicle width direction. Note that the interior display apparatus  61  may be provided additionally at such a position as to face the rear seats (the back side of the front seats). 
     The meter panel  85  displays, for example, a speedometer, a tachometer, an odometer, shift position information, on/off information on lights, and so on. 
     The multi-information panel  87  displays, for example: map information on the area around the host vehicle M; information on the current position of the host vehicle M on the map; traffic information (including traffic signal information) on the road which the host vehicle M is currently traveling or a route which the host vehicle M will be traveling; traffic participant information on traffic participants (including pedestrians, bicycles, motorcycles, other vehicles, and so on) present around the host vehicle M; various pieces of information such as messages to be presented to the traffic participants; and so on. 
     The right panel  89   a  displays image information on a right rear side and a right lower side relative to the host vehicle M captured by the camera  11  provided on the right side of the host vehicle M. 
     The left panel  89   b  displays image information on a left rear side and a left lower side relative to the host vehicle M captured by the camera  11  provided on the left side of the host vehicle M. 
     The interior display apparatus  61  is not particularly limited. For example, it is formed of liquid crystal displays (LCDs), organic electroluminescence (EL) displays, or the like. The interior display apparatus  61  may be formed of head-up displays (HUDs) that project necessary images on the glass windows  77 . 
     The speakers  63  have a function of outputting voice and sound. An appropriate number of speakers  63  are provided at appropriate positions inside the cabin such as in the instrument panel  60 , the door panels, and the rear parcel shelf (none of which is illustrated), for example. 
     When the interior display apparatus  61  is of a touchscreen type, the contacting operation detection apparatus  65  has a function of detecting a touched position on any of the display screens of the interior display apparatus  61  and outputting information on the detected touched position to the vehicle control apparatus  100 . The contacting operation detection apparatus  65  can omit this function when the interior display apparatus  61  is not of a touchscreen type. 
     The content playback apparatus  67  includes, for example, a digital versatile disc (DVD) playback apparatus, a compact disc (CD) playback apparatus, a television receiver, a playback apparatus for various guide images, and so on. Some or all of the interior display apparatus  61 , the speakers  63 , the contacting operation detection apparatus  65 , and the content playback apparatus  67  may be components also used by the navigation apparatus  20 . 
     The various operation switches  69  are arranged at appropriate positions inside the cabin. The various operation switches  69  include an autonomous driving ON/OFF switch  71  that issues an instruction to immediately start autonomous driving (or to start autonomous driving in the future) or to stop autonomous driving. The autonomous driving ON/OFF switch  71  may be a GUI switch or a mechanical switch. The various operation switches  69  may also include switches for driving the seat drive apparatus  75  and the window drive apparatus  79 . 
     The seats  73  are seats for the occupants in the host vehicle M to sit on. The seat drive apparatus  75  freely drives the reclining angles, front-rear positions, yaw angles, and the like of the seats  73 . The glass windows  77  are provided to all doors, for example. The window drive apparatus  79  drive the glass windows  77  so as to open or close them. 
     The in-cabin camera  81  is a digital camera utilizing a solid-state imaging element, such as a CCD or a CMOS. The in-cabin camera  81  is provided at such a position as to be capable of capturing an image of at least the head of the driver sitting on the driver&#39;s seat, such as in the rearview mirror, the steering boss (neither of which is illustrated), or the instrument panel  60 . In an example, the in-cabin camera  81  repetitively captures an image of the inside of the cabin including the driver on a periodic basis, for example. 
     The exterior display apparatus  83  has a function of displaying various pieces of information to traffic participants present around the host vehicle M (including pedestrians, bicycles, motorcycles, other vehicles, and so on). As illustrated in  FIG. 5A , the exterior display apparatus  83  includes, in a front grill  90  of the host vehicle M, a right front light unit  91 A and a left front light unit  91 B provided separated from each other in the vehicle width direction, and a front display unit  93  provided between the left and right front light units  91 A and  91 B. 
     As illustrated in  FIG. 5B , the exterior display apparatus  83  also includes, in a rear grill  94  of the host vehicle M, a right rear light unit  95 A and a left rear light unit  95 B provided separated from each other in the vehicle width direction, and a rear display unit  97  provided at a position inside the cabin of the host vehicle M at which the rear display unit  97  is visible from outside through a center lower portion of a rear window  96 . The rear display unit  97  is provided, for example, at the lower end of an opening for the rear window  96  (not illustrated) or the like. 
     Here, the configurations of the left and right front light units  91 A and  91 B of the exterior display apparatus  83  will now be described with reference to  FIG. 5C .  FIG. 5C  is a front view illustrating a schematic configuration of the right front light unit  91 A included in the host vehicle M. Note that the left and right front light units  91 A and  91 B have the same configuration. Thus, the schematic configuration of the right front light unit  91 A will be described as a description of the configurations of the left and right front light units  91 A and  91 B. 
     The right front light unit  91 A is formed in a circular shape in a front view. The right front light unit  91 A is configured such that a turn signal  91 Ab, a light display part  91 Ac, and a position lamp  91 Ad each formed in an annular shape are arranged concentrically in this order toward the radially outer side and centered around a headlamp  91 Aa formed in a circular shape in a front view having a smaller diameter than the outer diameter of the right front light unit  91 A. 
     The headlamp  91 Aa serves to assist the occupant to view ahead while the host vehicle M is traveling through a dark area by illuminating the front side in the direction of advance with light. The turn signal  91 Ab serves to notify traffic participants present around the host vehicle M of an intention to turn left or right when the host vehicle M does so. The light display part  91 Ac serves to notify traffic participants present around the host vehicle M of traveling intention of the host vehicle M including stopping (this will be described later in detail) along with a content displayed on the front display unit  93 . The position lamp  91 Ad serves to notify traffic participants present around the host vehicle M of its vehicle width while the host vehicle M is traveling through a dark area. 
     [Configuration of Vehicle Control Apparatus  100 ] 
     Next, referring back to  FIG. 2 , a configuration of the vehicle control apparatus  100  will be described. 
     The vehicle control apparatus  100  is implemented by, for example, at least one processor or hardware having an equivalent function. The vehicle control apparatus  100  may be configured of a combination of electronic control units (ECUs), micro-processing units (MPUs), or the like in each of which a processor such as a central processing unit (CPU), a storage apparatus, and a communication interface are connected by an internal bus. 
     The vehicle control apparatus  100  includes the target lane determination unit  110 , a driving assist control unit  120 , a travel control unit  160 , an HMI control unit  170 , and a storage unit  180 . 
     The functions of the target lane determination unit  110  and the driving assist control unit  120  and part or entirety of the function of the travel control unit  160  are implemented by the processor executing programs (software). Also, some or all of these functions may be implemented by hardware such as a large scale integration (LSI) circuit or an application specific integrated circuit (ASIC) or be implemented by a combination of software and hardware. 
     In the following description, when a subject is mentioned like “˜ unit does . . . ”, the driving assist control unit  120  reads out the corresponding program from a read only memory (ROM) or an electrically erasable programmable read-only memory (EEPROM) as necessary, loads it into a random access memory (RAM), and executes the corresponding function (described later). The program may be prestored in the storage unit  180 , or taken into the vehicle control apparatus  100  from another storage medium or through a communication medium, as necessary. 
     [Target Lane Determination Unit  110 ] 
     The target lane determination unit  110  is implemented by a micro processing unit (MPU), for example. The target lane determination unit  110  divides a route provided from the navigation apparatus  20  into a plurality of blocks (for example, divides the route at 100 [m]-intervals in the direction of advance of the vehicle), and determines a target lane in each block by referring to accurate map information  181 . For example, the target lane determination unit  110  determines which lane from the left to travel. When, for example, a branching point, a merging point, or the like is present on the route, the target lane determination unit  110  determines the target lane such that the host vehicle M will be able to travel a rational traveling route for advancing to the target branched path. The target lane determined by the target lane determination unit  110  is stored in the storage unit  180  as target lane information  182 . 
     [Driving Assist Control Unit  120 ] 
     The driving assist control unit  120  includes a driving assist mode control unit  130 , a recognition unit  140 , and a switching control unit  150 . 
     &lt;Driving Assist Mode Control Unit  130 &gt; 
     The driving assist mode control unit  130  determines an autonomous driving mode (autonomous driving assisting state) to be executed by the driving assist control unit  120  based on an operation of the HMI  35  by the driver, an event determined by an action plan generation unit  144 , how the host vehicle M should travel determined by a path generation unit  147 , and so on. The HMI control unit  170  is notified of the autonomous driving mode. 
     Each autonomous driving mode can be switched (overridden) to a lower-level autonomous driving mode by an operation of a constituent element of the driving operation system in the HMI  35 . 
     The override is initiated, for example, when a constituent element of the driving operation system in the HMI  35  by the driver of the host vehicle M continues to be operated for longer than a predetermined time, when a predetermined amount of change in operation (e.g., the accelerator position of the accelerator pedal  41 , the brake depression amount of the brake pedal  47 , or the steering angle of the steering wheel  55 ) is exceeded, when a constituent element of the driving operation system is operated more than a predetermined number of times, or the like. 
     &lt;Recognition Unit  140 &gt; 
     The recognition unit  140  includes a host vehicle position recognition unit  141 , an outside recognition unit  142 , an area identification unit  143 , the action plan generation unit  144 , and the path generation unit  147 . 
     &lt;Host Vehicle Position Recognition Unit  141 &gt; 
     The host vehicle position recognition unit  141  recognizes the traveling lane which the host vehicle M is currently traveling and the position of the host vehicle M relative to the traveling lane, based on the accurate map information  181  stored in the storage unit  180  and information inputted from the cameras  11 , the radars  13 , the lidars  15 , the navigation apparatus  20 , or the vehicle sensor  30 . 
     The host vehicle position recognition unit  141  recognizes the traveling lane by comparing the pattern of road section lines recognized from the accurate map information  181  (e.g., the arrangement of continuous lines and broken lines) and the pattern of the road section lines around the host vehicle M recognized from images captured by the cameras  11 . In this recognition, the current position of the host vehicle M obtained from the navigation apparatus  20  and the result of processing by the INS may be considered. 
     &lt;Outside Recognition Unit  142 &gt; 
     As illustrated in  FIG. 2 , the outside recognition unit  142  recognizes an outside situation including, for example, the positions, vehicle speeds, and accelerations of nearby vehicles based on the information on the outside inputted from the external sensor  10  including the cameras  11 , the radars  13 , and the lidars  15 . The nearby vehicles refer to, for example, other vehicles traveling around the host vehicle M in the same direction as the host vehicle M (a leading vehicle and a trailing vehicle; details will be described later). 
     The positions of the nearby vehicles may be represented as the centers of gravity of these other vehicles or representative points such as corners, or represented as areas expressed by the contours of the other vehicles. The states of the nearby vehicles may include the speeds and accelerations of the nearby vehicles and whether the nearby vehicles are changing lanes (or whether they are about to change lanes) which are figured out based on information from the above-mentioned various instruments. Alternatively, the outside recognition unit  142  may employ a configuration that recognizes the positions of targets including guard rails, utility poles, parked vehicles, pedestrians, and traffic signs, as well as the nearby vehicles including the leading vehicle and the trailing vehicle. 
     In embodiments of the present invention, of the nearby vehicles, the vehicle that is traveling immediately ahead of the host vehicle M in the same traveling lane as that of the host vehicle M and is a following target in following travel control will be referred to as “leading vehicle”. Also, of the nearby vehicles, the vehicle that is traveling immediately behind the host vehicle M in the same traveling lane as that of the host vehicle M will be referred to as “trailing vehicle”. 
     &lt;Area Identification Unit  143 &gt; 
     The area identification unit  143  obtains information on specific areas present around the host vehicle M (interchanges: ICs, junctions: JCTs, and points where the number of lanes increases or decreases) based on map information. In this way, the area identification unit  143  can obtain information on specific areas that assist the host vehicle M to travel smoothly even if the host vehicle M is hidden behind vehicles ahead including the leading vehicle and cannot capture an image in the direction of advance with the external sensor  10 . 
     Instead of obtaining the information on specific areas based on the map information, the area identification unit  143  may obtain the information on the specific areas by identifying targets with image processing based on an image in the direction of advance captured with the external sensor  10  or by recognizing targets based on the contours in an image in the direction of advance with internal processing by the outside recognition unit  142 . 
     Also, a configuration may be employed which, as will be described later, uses the VICS information obtained by the communication apparatus  25  to enhance the accuracy of the information on the specific areas obtained by the area identification unit  143 . 
     &lt;Action Plan Generation Unit  144 &gt; 
     The action plan generation unit  144  sets the start point of autonomous driving and/or the destination point of the autonomous driving. The start point of the autonomous driving may be the current position of the host vehicle M or a geographical point at which an operation is performed as an instruction to perform the autonomous driving. The action plan generation unit  144  generates an action plan in the zone from this start point to the destination point of the autonomous driving. Mote that the action plan is not limited to the above, and the action plan generation unit  144  may generate action plans for any zones. 
     The action plan is formed of a plurality of events to be executed in turn, for example. Examples of the plurality of events include: a deceleration event in which the host vehicle M is caused to decelerate; an acceleration event in which the host vehicle M is caused to accelerate; a lane keep event in which the host vehicle M is caused to travel so as not to depart from its traveling lane; a lane change event in which the host vehicle M is caused to change its traveling lane; a passing event in which the host vehicle M is caused to pass the leading vehicle; a branching event in which the host vehicle M is caused to change to the desired lane at a branching point or to travel so as not to depart from the current traveling lane; a merge event in which the host vehicle M is in a merging lane for merging into a main lane and is caused to accelerate or decelerate and change its traveling lane; a handover event in which the host vehicle M is caused to transition from the manual driving mode to an autonomous driving mode (autonomous driving assisting state) at the start point of the autonomous driving or transition from the autonomous driving mode to the manual driving mode at the scheduled end point of the autonomous driving; and so on. 
     The action plan generation unit  144  sets a lane change event, a branching event, or a merge event at each point where the target lane determined by the target lane determination unit  110  changes. Information indicating the action plan generated by the action plan generation unit  144  is stored in the storage unit  180  as action plan information  183 . 
     The action plan generation unit  144  includes a mode changing unit  145  and a notification control unit  146 . 
     &lt;Mode Changing Unit  145 &gt; 
     Based, for example, on the result of recognition of the targets present in the direction of advance of the host vehicle M by the outside recognition unit  142 , the mode changing unit  145  selects a driving mode suitable for the recognition result from among driving modes including a plurality of preset levels of autonomous driving modes and the manual driving mode, and causes the host vehicle M to perform autonomous driving using the selected driving mode. 
     &lt;Notification Control Unit  146 &gt; 
     When the mode changing unit  145  changes the driving mode of the host vehicle M, the notification control unit  146  issues a notice indicating the driving mode of the host vehicle M has been changed. The notification control unit  146 , for example, causes the speakers  63  to output audio information prestored in the storage unit  180  to issue a notice indicating that the driving mode of the host vehicle M has been changed. 
     Note that the notice is not limited to an audio notice. The notice may be issued in the form of a display, emitted light, a vibration, or a combination of these as long as it can notify the driver of the change in the driving mode of the host vehicle M. 
     &lt;Path Generation Unit  147 &gt; 
     The path generation unit  147  generates a path which the host vehicle M should travel, based on the action plan generated by the action plan generation unit  144 . 
     &lt;Switching Control Unit  150 &gt; 
     As illustrated in  FIG. 2 , the switching control unit  150  switches the driving mode, between an autonomous driving mode and the manual driving mode based on a signal inputted from the autonomous driving ON/OFF switch  71  (see  FIG. 3 ) and so on. Also, based on an operation of a constituent element of the driving operation system in the HMI  35  performed as an accelerating, decelerating, or steering instruction, the switching control unit  150  switches the current autonomous driving mode to a lower-level driving mode. For example, if a state where an operation amount indicated by a signal inputted from a constituent element of the driving operation system in the HMI  35  is above a threshold value continues for a reference time or longer, the switching control unit  150  switches (overrides) the current autonomous driving mode to a lower-level driving mode. 
     Also, the switching control unit  150  may perform switching control that brings the driving mode back to the original autonomous driving mode if detecting no operation on any constituent elements of the driving operation system in the HMI  35  for a predetermined time after the switching to the lower-level driving mode by the override. 
     &lt;Travel Control Unit  160 &gt; 
     The travel control unit  160  controls travel of the host vehicle M by controlling the travel drive force output apparatus  200 , the steering apparatus  210 , and the brake apparatus  220  such that the host vehicle M will pass through the path generated by the path generation unit  147 , which the host vehicle M should travel, on the scheduled time. 
     &lt;HMI Control Unit  170 &gt; 
     When notified of setting information on the autonomous driving mode of the host vehicle M by the driving assist control unit  120 , the HMI control unit  170  refers to mode-by-mode operation permission information  184  and controls the HMI  35  according to contents set for the autonomous driving mode. 
     As illustrated in  FIG. 2 , based on the information on the driving mode of the host vehicle M obtained from the driving assist control unit  120  and by referring to the mode-by-mode operation permission information  184 , the HMI control unit  170  determines the apparatuses permitted to be used (the navigation apparatus  20  and part or entirety of the HMI  35 ) and the apparatuses not permitted to be used. Also, based on the result of the above determination, the HMI control unit  170  controls whether to accept the driver&#39;s operations of the driving operation system in the HMI  35  and the navigation apparatus  20 . 
     For example, when the driving mode executed by the vehicle control apparatus  100  is the manual driving mode, the HMI control unit  170  accepts the driver&#39;s operations of the driving operation system in the HMI  35  (e.g., the accelerator pedal  41 , the brake pedal  47 , the shift lever  51 , the steering wheel  55 , and so on; see  FIG. 3 ). 
     The HMI control unit  170  includes a display control unit  171 . 
     &lt;Display Control Unit  171 &gt; 
     The display control unit  171  controls displays on the interior display apparatus  61  and the exterior display apparatus  83 . Specifically, for example, when the driving mode executed by the vehicle control apparatus  100  is an autonomous driving mode with a high degree of autonomy, the display control unit  171  performs control that causes the interior display apparatus  61  and/or the exterior display apparatus  83  to display information such as a reminder, warning, or driving assistance to traffic participants present around the host vehicle M. This will be described later in detail. 
     &lt;Storage Unit  180 &gt; 
     The storage unit  180  stores pieces of information such as the accurate map information  181 , the target lane information  182 , the action plan information  183 , and the mode-by-mode operation permission information  184 , for example. The storage unit  180  is implemented with a ROM, a RAM, a hard disk drive (HDD), a flash memory, or the like. The programs to be executed by the processor may be prestored in the storage unit  180  or downloaded from an external apparatus via in-vehicle Internet equipment or the like. Alternatively, the programs may be installed into the storage unit  180  by connecting a mobile storage medium storing the programs to a drive apparatus not illustrated. 
     The accurate map information  181  is map information that is more accurate than the normal map information included in the navigation apparatus  20 . The accurate map information  181  contains, for example, information on the centers of lanes, information on the boundaries of the lanes, and so on. The boundaries of the lanes include the types, colors, and lengths of lane marks, the widths of roads, the widths of shoulders, the widths of main lanes, the widths of lanes, the positions of boundaries, the types of boundaries (guard rail, plant, and curb), hatched zones, and so on, and these boundaries are contained in an accurate map. 
     The accurate map information  181  may also contain road information, traffic regulation information, address information (addresses and postal codes), facility information, telephone number information, and so on. The road information contains information indicating the types of roads such as expressways, tollways, national highways, and prefectural roads, and information on the number of lanes in each road, the width of each lane, the gradient of the road, the position of the road (three-dimensional coordinates including the longitude, latitude, and height), the curvature of the lane, the positions of merging or branching points on the lane, the signs provided on the road, and so on. The traffic regulation information contains information such as the occurrence of lane closures due to construction, traffic accident, congestion, or the like. 
     [Travel Drive Force Output Apparatus  200 , Steering Apparatus  210 , and Brake Apparatus  220 ] 
     As illustrated in  FIG. 2 , the vehicle control apparatus  100  controls the drive of the travel drive force output apparatus  200 , the steering apparatus  210 , and the brake apparatus  220  in accordance with a travel control instruction from the travel control unit  260 . 
     &lt;Travel Drive Force Output Apparatus  200 &gt; 
     The travel drive force output apparatus  200  outputs drive force (torque) for causing the host vehicle M to travel to its drive wheels. When the host vehicle M is an automobile with an internal combustion engine as a power source, the travel drive force output apparatus  200  includes, for example, the internal combustion engine, a transmission, and an engine electronic control unit (ECU) that controls the internal combustion engine (none of which is illustrated). 
     Alternatively, when the host vehicle M is an electric automobile with an electric motor as a power source, the travel drive force output apparatus  200  includes a motor for traveling and a motor ECU that controls the motor for traveling (neither of which is illustrated). 
     Still alternatively, when the host vehicle M is a hybrid automobile, the travel drive force output apparatus  200  includes an internal combustion engine, a transmission, an engine ECU, a motor for traveling, and a motor ECU (none of which is illustrated). 
     When the travel drive force output apparatus  200  includes only an internal combustion engine, the engine ECU adjusts the throttle opening degree of the internal combustion engine, the shift stage, and so on in accordance with later-described information inputted from the travel control unit  160 . 
     When the travel drive force output apparatus  200  includes only a motor for traveling, the motor ECU adjusts the duty ratio of a PWM signal to be applied to the motor for traveling in accordance with information inputted from the travel control unit  160 . 
     When the travel drive force output apparatus  200  includes an internal combustion engine and a motor for traveling, the engine ECU and the motor ECU cooperate with each other to control the travel drive force in accordance with information inputted from the travel control unit  160 . 
     &lt;Steering Apparatus  210 &gt; 
     The steering apparatus  210  includes, for example, a steering ECU and an electric motor (neither of which is illustrated). The electric motor changes the direction of the turning wheels by exerting force on a rack-and-pinion mechanism, for example. The steering ECU drives the electric motor in accordance with information inputted from the vehicle control apparatus  100  or steering angle or steering torque information inputted, to thereby change the direction of the turning wheels. 
     &lt;Brake Apparatus  220 &gt; 
     The brake apparatus  220  is, for example, an electric servo brake apparatus including a brake caliper, a cylinder that transfers hydraulic pressure to the brake caliper, an electric motor that generates the hydraulic pressure in the cylinder, and a braking control unit (none of which is illustrated). The braking control unit of the electric servo brake apparatus controls the electric motor in accordance with information inputted from the travel control unit  160  to output a brake torque corresponding to a braking operation to each wheel. The electric servo brake apparatus may include a mechanism, as a backup, that transfers hydraulic pressure generated by operating the brake pedal  47  to the cylinder through a master cylinder. 
     Note that the brake apparatus  220  is not limited to the above-described electric servo brake apparatus, and may be an electronically controlled hydraulic brake apparatus. The electronically controlled hydraulic brake apparatus controls an actuator in accordance with information inputted from the travel control unit  160  to transfer hydraulic pressure in a master cylinder to a cylinder. Also, the brake apparatus  220  may include a regenerative brake using a motor for traveling that can be included in the travel drive force output apparatus  200 . 
     [Block Configuration of Autonomous Driving Vehicle Information Presentation Apparatus  300 ] 
     Next, a block configuration of an autonomous driving vehicle information presentation apparatus  300  according to an embodiment of the present invention included in the above-described vehicle control apparatus  100  will be described with reference to  FIG. 6 . 
       FIG. 6  is a block configuration diagram conceptually illustrating functions of the autonomous driving vehicle information presentation apparatus  300  according to the embodiment of the present invention. 
     As illustrated in  FIG. 6 , the autonomous driving vehicle information presentation apparatus  300  according to the embodiment of the present invention is configured of an outside information obtaining unit  311 , a congestion information obtaining unit  313 , a traffic signal information obtaining unit  315 , a determination unit  323 , a calculation unit  325 , the action plan generation unit  144  (see  FIG. 2 ), and an information presentation unit  331 . 
     &lt;Outside Information Obtaining Unit  311 &gt; 
     As illustrated in  FIG. 6 , the outside information obtaining unit  311  has a function of obtaining outside information containing the traveling state of leading vehicle  5   a  detected by the external sensor  10  and present ahead of the host vehicle M in the direction of advance (see  FIG. 8A , for example) and the traveling state of a trailing vehicle  7   a  detected by the external sensor  10  and present behind the host vehicle M in the direction of advance (see  FIG. 8A , for example). The outside information obtaining unit  311  is a functional member corresponding to the recognition unit  140  of the vehicle control apparatus  100  illustrated in  FIG. 2 . 
     Note that the channel for the outside information obtaining unit  311  to obtain the outside information is not limited to the external sensor  10 . For example, the navigation apparatus  20  and the communication apparatus  25  may be employed. 
     &lt;Congestion Information Obtaining Unit  313 &gt; 
     As illustrated in  FIG. 6 , the congestion information obtaining unit  313  has a function of obtaining congestion information on congestion ahead of the host vehicle M in the direction of advance. The congestion information obtaining unit  313  is a functional member corresponding to the recognition unit  140  of the vehicle control apparatus  100  illustrated in  FIG. 2 . 
     Note that the channel for the congestion information obtaining unit  313  to obtain the congestion information is not particularly limited. For example, the congestion information obtaining unit  313  may employ a configuration that obtains the congestion information based on VICS traffic information obtained via the communication apparatus  25  or traffic information obtained via road-to-vehicle communication or vehicle-to-vehicle communication using the communication apparatus  25 . 
     &lt;Traffic Signal Information Obtaining Unit  315 &gt; 
     As illustrated in  FIG. 6 , the traffic signal information obtaining unit  315  has a function of obtaining traffic signal information on traffic lights (not illustrated) present ahead of the host vehicle M in the direction of advance. The traffic signal information obtaining unit  315  is a functional member corresponding to the recognition unit  140  of the vehicle control apparatus  100  illustrated in  FIG. 2 . 
     Note that the channel for the traffic signal information obtaining unit  315  to obtain the traffic signal information is not particularly limited. For example, the traffic signal information obtaining unit  315  may employ a configuration that obtains the traffic signal information based on TSPS traffic signal information obtained via the communication apparatus  25  or traffic signal information obtained via road-to-vehicle communication or vehicle-to-vehicle communication using the communication apparatus  25 . 
     &lt;Determination Unit  323 &gt; 
     As illustrated in  FIG. 6 , the determination unit  323  has a function of determining the presence of the trailing vehicle  7   a  following the host vehicle M (see  FIG. 8A , for example) based on the outside information obtained by the outside information obtaining unit  311 . The determination unit  323  is a functional member corresponding to the recognition unit  140  of the vehicle control apparatus  100  illustrated in  FIG. 2 . 
     &lt;Calculation Unit  325 &gt; 
     As illustrated in  FIG. 6 , the calculation unit  325  has a function of calculating a host vehicle-trailing vehicle distance DS being the distance between the host vehicle M and the trailing vehicle  7   a  when the determination unit  323  determines that the trailing vehicle  7   a  following the host vehicle M is present. The calculation unit  325  is a functional member corresponding to the recognition unit  140  of the vehicle control apparatus  100  illustrated in  FIG. 2 . 
     &lt;Information Presentation Unit  331 &gt; 
     As illustrated in  FIG. 6 , the information presentation unit  331  is configured of the rear display unit  97  (see  FIGS. 8A and 8B , for example) and emergency flashing lights  333 . The rear display unit  97  is provided at a position in a rear portion of the cabin of the host vehicle M where the rear display unit  97  is visible to the occupant in the trailing vehicle  7   a  (see  FIG. 8A , for example) and, preferably, easily visible to the driver. The emergency flashing lights  333  are lights that are caused to flash when the host vehicle M is stopped or parked on a road in a dark area or the like, and are also called hazard lamps. The rear display unit  97  and the emergency flashing lights  333  correspond to the “exterior display apparatus  83 ” in the present invention. 
     The information presentation unit  331  has a function of presenting information including the action plan for the host vehicle M and the like by using the rear display unit  97  and the emergency flashing lights  333 . The information presentation unit  331  is a functional member corresponding to the HMI control unit  170  of the vehicle control apparatus  100  illustrated in  FIG. 2 . The function of the information presentation unit  331  will be described later in detail. 
     [Operation of Autonomous Driving Vehicle Information Presentation Apparatus  300 ] 
     Next, the operation of the autonomous driving vehicle information presentation apparatus  300  according to an embodiment of the present invention will be described with reference to  FIG. 7 . 
       FIG. 7  is a flowchart to be used to describe the operation of the autonomous driving vehicle information presentation apparatus  300 . 
     It is assumed that the autonomous driving vehicle (host vehicle) M equipped with the autonomous driving vehicle information presentation apparatus  300  is traveling in a preset level of autonomous driving mode. 
     In step S 11  illustrated  FIG. 7 , the outside information obtaining unit  311  obtains outside information containing the traveling state of the leading vehicle  5   a  detected by the external sensor  10  and present ahead of the host vehicle M in the direction of advance (see  FIG. 8A , for example) and the traveling state of the trailing vehicle  7   a  detected by the external sensor  10  and present behind the host vehicle M in the direction of advance (see  FIG. 8A , for example). The congestion information obtaining unit  313  obtains congestion information on congestion ahead of the host vehicle M in the direction of advance. The traffic signal information obtaining unit  315  obtains traffic signal information on the traffic lights present ahead of the host vehicle M in the direction of advance. 
     In step S 12 , the action plan generation unit  144  generates an action plan for the host vehicle M based on the outside information, the congestion information, and the traffic signal information obtained in step S 11 . 
     In step S 13 , the travel control unit  160  (see  FIG. 2 ) executes an autonomous driving operation in accordance with the action plan for the host vehicle M generated by the action plan generation unit  144 . 
     In step S 14 , the determination unit  323  determines the presence of the trailing vehicle  7   a  based on the outside information obtained in step S 11 , which contains the traveling state of the trailing vehicle  7   a.    
     In step S 15 , if the result of the determination made in step S 14  indicates that the trailing vehicle  7   a  is present, the determination unit  323  causes the process flow to advance to the next step S 16 . 
     If, on the other hand, the result of the determination made in step S 14  indicates that the trailing vehicle  7   a  is absent, the determination unit  323  causes the process flow to jump to step  319 . 
     In step S 16 , the calculation unit  325  calculates the host vehicle-trailing vehicle distance DS being the distance between the host vehicle M and the trailing vehicle  7   a.  The host vehicle-trailing vehicle distance DS calculated by the calculation unit  325  is transmitted to the HMI control unit  170  (see  FIG. 2 ). 
     In step S 17 , the information presentation unit  331  sets a presented state of information addressed to the trailing vehicle  7   a  for the case where the trailing vehicle  7   a  is determined to be present, according to the magnitude of the host vehicle-trailing vehicle distance DS. This will be described later in detail. 
     In step S 18 , the information presentation unit  331  controls the display of the information by using the presented state of the information set in step S 17 . 
     In step S 19 , the information presentation unit  331  sets no presentation of information as the presented state of information for the case where the trailing vehicle  7   a  is determined to be absent. This is because if information addressed to the trailing vehicle  7   a  is presented even when the trailing vehicle  7   a  is determined to be absent in steps S 14  and S 15 , a traffic participant (other than the trailing vehicle  7   a ) that is present around the host vehicle M may be misled by seeing the information. 
     Note that the information presentation unit  331  does not present information addressed to the trailing vehicle  7   a  in step S 18  when the information presentation unit  331  sets no presentation of information as the presented state of information for the case where the trailing vehicle  7   a  is determined to be absent. 
     [Operation of Autonomous Driving Vehicle Information Presentation Apparatus  300  According to First Example] 
     Next, the operation of the autonomous driving vehicle information presentation apparatus  300  according to the first example will be described with reference to  FIGS. 8A and 8B . 
       FIG. 8A  is a diagram illustrating the traveling scene of the autonomous driving vehicle M equipped with the autonomous driving vehicle information presentation apparatus  300  according to the first example.  FIG. 8B  is a diagram illustrating an information presenting state of the autonomous driving vehicle information presentation apparatus  300  according to the first example. 
     As illustrated in  FIG. 8A , the autonomous driving vehicle information presentation apparatus  300  according to the first example is assumed to be in a traveling scene in which congestion involving the leading vehicle  5   a  has occurred ahead of the host vehicle M traveling in the direction of advance indicated by the arrow in the diagram, and the trailing vehicle  7   a  is present behind the host vehicle M in the direction of advance. The host vehicle M is crawling or has stopped immediately behind the leading vehicle  5   a.    
     Here, in the traveling scene according to the first example, the trailing vehicle  7   a  is located away from the position of the host vehicle M (the host vehicle-trailing vehicle distance DS&gt;a predetermined distance threshold value DSth). 
     Note that the predetermined distance threshold value DSth is set at an appropriate value by taking into consideration a vehicle-to-vehicle distance from which it is assumed to get difficult for the occupant in the trailing vehicle  7   a  to figure out the traffic situation ahead of the host vehicle M in the direction of advance. 
     In such a traveling scene for the autonomous driving vehicle information presentation apparatus  300  according to the first example, the occupant in the trailing vehicle  7   a  located away from the position of the host vehicle M does not know why the host vehicle M is crawling or has stopped. The occupant in the trailing vehicle  7   a  behind the host vehicle M may thus feel a sense of unease. 
     Thus, in the autonomous driving vehicle information presentation apparatus  300  according to the first example, the outside information obtaining unit  311  obtains the outside information on the outside including the trailing vehicle  7   a  present behind the host vehicle M in the direction of advance. The determination unit  323  determines the presence of the trailing vehicle  7   a  following the host vehicle M based on the outside information. The calculation unit  325  calculates the host vehicle-trailing vehicle distance DS being the distance between the host vehicle M and the trailing vehicle  7   a  when the determination unit  323  determines that the trailing vehicle  7   a  following the host vehicle M is present. The information presentation unit  331  presents information addressed to the trailing vehicle  7   a  by using the rear display unit  97  (the exterior display apparatus  83 ; the same applies below) provided at a position in the rear portion of the cabin of the host vehicle M at which the rear display unit  97  is visible to the occupant in the trailing vehicle  7   a.    
     Here, the information presentation unit  331  sets the presented state of the information addressed to the trailing vehicle  7   a  to a state that varies according to the magnitude of the host vehicle-trailing vehicle distance DS calculated by the calculation unit  325  (corresponding to an autonomous driving vehicle information presentation apparatus  300  based on an aspect (1)). 
     Specifically, when, for example, the host vehicle-trailing vehicle distance DS is greater than a first threshold value DSth01 (the host vehicle-trailing vehicle distance DS&gt;the first threshold value DSth01), the information presentation unit  331  presents the information addressed to the trailing vehicle  7   a  via defocused displaying using the rear display unit  97  (corresponding to an autonomous driving vehicle information presentation apparatus  300  based on an aspect (6)). 
     Note that the defocused displaying means displaying the information to be presented in an out-of-focus state. Also, the first threshold value DSth01 is a value falling within the range of the above-mentioned predetermined distance threshold value DSth. Specifically, a value based on the predetermined distance threshold value DSth is used as the first threshold value DSth01. 
     With this configuration, in a traveling scene in which the host vehicle-trailing vehicle distance DS is so large that it is difficult for the occupant in the trailing vehicle  7   a  to figure out the traffic situation ahead of the host vehicle M in the direction of advance, information addressed to the trailing vehicle  7   a  is presented in an out-of-focus state with the rear display unit  97  included in the host vehicle M. In this way, the occupant in the trailing vehicle  7   a  will concentrate on figuring out the information presented in the out-of-focus state and intently stare at the information. 
     Thus, the host vehicle M can communicate with a traffic participant present around the host vehicle M (trailing vehicle  7   a ) by attracting the attention of the occupant in the trailing vehicle  7   a.  This makes it possible to create a smooth traffic environment even when unpredicted traffic congestion occurs. 
     In another specific example of setting the presented state of information addressed to the trailing vehicle  7   a  according to the magnitude of the hoot vehicle-trailing vehicle distance DS calculated by the calculation unit  325 , a configuration may be employed which, when the host vehicle-trailing vehicle distance DS is, for example, greater than a second threshold value DSth02 (the host vehicle-trailing vehicle distance DS&gt;the second threshold value DSth02), presents the information addressed to the trailing vehicle  7   a  by using a design (representing this information) (see  FIG. 8B ) (corresponding to part of an autonomous driving vehicle information presentation apparatus  300  based on an aspect (7)). 
     Note that the second threshold value DSth02 is a value falling within the range of the above-mentioned predetermined distance threshold value DSth, like the first threshold value DSth01. Specifically, a value based on the predetermined distance threshold value DSth is employed as the second threshold value DSth02. Here, the first threshold value DSth01 and the second threshold value DSth02 may be different values or the same value. 
     The autonomous driving vehicle information presentation apparatus  300  according to the first example presents information addressed to the trailing vehicle  7   a  by using a design (representing this information) with which it is relatively easy for the occupant in the trailing vehicle  7   a  to figure the information out even by looking at it from a distance, in a traveling scene in which the host vehicle-trailing vehicle distance DS is so large (far) that it is difficult for the occupant to figure out the traffic situation ahead of the host vehicle M in the direction of advance. This enables the occupant in the trailing vehicle  7   a  to easily figure out the information addressed to the trailing vehicle  7   a  even when the host vehicle-trailing vehicle distance DS is large. 
     Thus, the host, vehicle M can communicate with a traffic participant present around the host vehicle M (trailing vehicle  7   a ) by facilitating the occupant in the trailing vehicle  7   a  to figure out the information. This makes it possible to create a smooth traffic environment even when unpredicted traffic congestion occurs. 
     [Operation of Autonomous Driving Vehicle Information Presentation Apparatus  300  According to Second Example] 
     Next, the operation of the autonomous driving vehicle information presentation apparatus  300  according to the second example will be described with reference to  FIGS. 9A to 9C . 
       FIG. 9A  is a diagram illustrating the traveling scene of the autonomous driving vehicle M equipped with the autonomous driving vehicle information presentation apparatus  300  according to the second example.  FIG. 9B  is a diagram illustrating a modification of the information presenting state of the autonomous driving vehicle information presentation apparatus  300  according to the second example.  FIG. 9C  is a diagram illustrating a modification of the information presenting state of the autonomous driving vehicle information presentation apparatus  300  according to the second example. 
     As illustrated in  FIG. 9A , the autonomous driving vehicle information presentation apparatus  300  according to the second example is the same as the autonomous driving vehicle information presentation apparatus  300  according to the first example In that it is assumed to be in a traveling scene in which congestion involving the leading vehicle  5   a  has occurred ahead of the host vehicle M traveling in the direction of advance indicated by the arrow in the diagram, and the trailing vehicle  7   a  is present behind the host vehicle M in the direction of advance, and in that the host vehicle M is crawling or has stopped immediately behind the leading vehicle  5   a.    
     However, in the traveling scene according to the second example, the trailing vehicle  7   a  is located close to the position of the host vehicle M (the host vehicle-trailing vehicle distance DS&lt;the above-mentioned predetermined distance threshold value DSth). 
     In such a traveling scene for the autonomous driving vehicle information presentation apparatus  300  according to the second example, the occupant in the trailing vehicle  7   a  located close to the position of the host vehicle M roughly knows why the host vehicle M is crawling or has stopped. However, in a case where the host vehicle M is a large vehicle, the occupant will not be able to figure out the situation ahead of the host vehicle M in the direction of advance. The occupant in the trailing vehicle  7   a  behind the host vehicle M may thus feel a sense of unease in the case where the host vehicle M is a large vehicle. 
     Thus, in a specific example of setting the presented state of information addressed to the trailing vehicle  7   a  according to the magnitude of the host vehicle-trailing vehicle distance DS calculated by the calculation unit  325  based on the autonomous driving vehicle information presentation apparatus  300  according to the first example, the autonomous driving vehicle information presentation apparatus  300  according to the second example presents the information addressed to the trailing vehicle  7   a  by using characters (indicating this information) when the host vehicle-trailing vehicle distance DS is smaller than the above-mentioned second threshold value DSth02 (the host vehicle-trailing vehicle distance DS&lt;the second threshold value DSth02) (corresponding to part of an autonomous driving vehicle information presentation apparatus  300  based on an aspect (7)). 
     The autonomous driving vehicle information presentation apparatus  300  according to the second example presents the information addressed to the trailing vehicle  7   a  by using characters (indicating this information) in a traveling scene in which the host vehicle-trailing vehicle distance DS is so small (close) that the occupant in the trailing vehicle  7   a  can figure out the traffic situation ahead of the host vehicle M in the direction of advance. This enables the occupant in the trailing vehicle  7   a  to easily figure out the information addressed to the trailing vehicle  7   a  even in the case where the host vehicle-trailing vehicle distance DS is small, but the host vehicle M is a large vehicle. 
     Thus, the host vehicle M can communicate with a traffic participant present around the host vehicle M (trailing vehicle  7   a ) by facilitating the occupant in the trailing vehicle  7   a  to figure out the information. This makes it possible to create a smooth traffic environment even when unpredicted traffic congestion occurs. 
     Also, in the autonomous driving vehicle information presentation apparatus  300  according to the second example, the information presentation unit  331  may employ a configuration that, as illustrated in  FIG. 9C , presents the information addressed to the trailing vehicle  7   a  (e.g., congestion information or the like) by using one of a plurality of languages including the first language (English) (English and Japanese in the example illustrated in  FIG. 9C ) while switching between the languages in turn at predetermined time intervals. In the example illustrated in  FIG. 9C , the display on the rear display unit  91  is switched between character strings indicating congestion such as “Mae ga tsumatte imasu” and “Traffic jam ahead” in turn at the predetermined time intervals. 
     With such a configuration, even if the occupant in the trailing vehicle  7   a  behind the host vehicle M is a foreigner, the host vehicle M can communicate with the traffic participant present around the host vehicle M (trailing vehicle  7   a ). This makes it possible to create a smooth traffic environment even when unpredicted traffic congestion occurs. 
     [Operation and Advantageous Effects of Autonomous Driving Vehicle Information Presentation Apparatuses  300  According to Embodiments of Present Invention] 
     Next, operation and advantageous effects of the autonomous driving vehicle information presentation apparatuses  300  according to the embodiments of the present invention will be described. 
     It is assumed that the autonomous driving vehicle information presentation apparatus  300  based on the aspect (1) is an autonomous driving vehicle information presentation apparatus  300  that is used in an autonomous driving vehicle which obtains outside information on an outside including a leading vehicle  5   a  present ahead of a host vehicle M in a direction of advance and autonomously controls at least one of speed and steering of the host vehicle M based on the obtained outside information, and that presents information to a traffic participant present around the host vehicle M. 
     The autonomous driving vehicle information presentation apparatus  300  based on the aspect (1) includes: an outside information obtaining unit  311  that obtains the outside information on the outside including a trailing vehicle  7   a  present behind the host vehicle M in the direction of advance; a determination unit  323  that determines presence of the trailing vehicle  7   a  following the host vehicle M, based on the outside information; a calculation unit  325  that calculates a host vehicle-trailing vehicle distance DS being a distance between the host vehicle M and the trailing vehicle  7   a,  when the determination unit  323  determines that the trailing vehicle  7   a  is present; and an information presentation unit  331  that presents information addressed to the trailing vehicle  7   a  by using a rear display unit  97  provided at a position in a rear portion of a cabin of the host vehicle M at which the rear display unit  97  is visible to an occupant in the trailing vehicle  7   a.    
     The information presentation unit  331  employs a configuration which sets a presented state of the information addressed to the trailing vehicle  7   a  according to a magnitude of the host vehicle-trailing vehicle distance DS calculated by the calculation unit  325 . 
     In the autonomous driving vehicle information presentation apparatus  300  based on the aspect (1), the outside information obtaining unit  311  obtains the outside information on the outside including the trailing vehicle  7   a  present behind the host vehicle M in the direction of advance. The determination unit  323  determines the presence of the trailing vehicle  7   a  following the host vehicle M, based on the outside information. The calculation unit  325  calculates the host vehicle-trailing vehicle distance DS being the distance between the host vehicle M and the trailing vehicle  7   a  when the determination unit  323  determines that the trailing vehicle  7   a  following the host vehicle M is present. The information presentation unit  331  presents information addressed to the trailing vehicle  7   a  by using the rear display unit  97  (exterior display apparatus  83 ) provided at a position in the rear portion of the cabin of the host vehicle M at which the rear display unit  97  is visible to the occupant in the trailing vehicle  7   a.    
     In particular, the information presentation unit  331  sets the presented state of the information addressed to the trailing vehicle  7   a  according to the magnitude of the host vehicle-trailing vehicle distance DS calculated by the calculation unit  325 . As described below, the presented state of the information is thus set mainly in consideration of convenience for the occupant in the trailing vehicle  7   a  to figure out the information. 
     According to the autonomous driving vehicle information presentation apparatus  300  based on the aspect (1), the information presentation unit  331  sets the presented state of the information addressed to the trailing vehicle  7   a  according to the magnitude of the host vehicle-trailing vehicle distance DS calculated by the calculation unit  325 . Thus, the host vehicle M can communicate with a traffic participant present around the host vehicle M (trailing vehicle  7   a ) by facilitating the occupant in the trailing vehicle  7   a  to figure out the information. The autonomous driving vehicle can therefore be expected to achieve an advantageous effect of further reducing a sense of unease that may be felt by the traffic participant present around the host vehicle M. 
     An autonomous driving vehicle information presentation apparatus  300  based on an aspect (2) is the autonomous driving vehicle information presentation apparatus  300  based on the aspect (1) employing a configuration which further includes an action plan generation unit  144  that obtains a traveling state of the leading vehicle  5   a  based on the outside information and generates an action plan for the host vehicle M based on the obtained traveling state of the leading vehicle  5   a,  and in which the information presentation unit  331  presents the information addressed to the trailing vehicle  7   a  and containing the action plan for the host vehicle M by using the rear display unit  97 . 
     In the autonomous driving vehicle information presentation apparatus  300  based on the aspect (2), the action plan generation unit  144  obtains the traveling state of the leading vehicle  5   a  based on the outside information, and generates an action plan for the host vehicle M based on the obtained traveling state of the leading vehicle  5   a.  The information presentation unit  331  presents the information addressed to the trailing vehicle  7   a  and containing the action plan for the host vehicle M by using the rear display unit  97 . 
     According to the autonomous driving vehicle information presentation apparatus  300  based on the aspect (2), the host vehicle M can communicate with a traffic participant present around the host vehicle M (trailing vehicle  7   a ) by presenting the information addressed to the trailing vehicle  7   a  and containing the action plan for the host vehicle V to the occupant in the trailing vehicle  7   a.  This makes it possible to create a smooth traffic environment even when unpredicted traffic congestion occurs. 
     An autonomous driving vehicle information presentation apparatus  300  based on an aspect (3) is the autonomous driving vehicle information presentation apparatus  300  based on the aspect (1) or (2) which further includes a traffic signal information obtaining unit  315  that obtains traffic signal information on a traffic light present ahead of the host vehicle M in the direction of advance, and in which the information presentation unit  331  presents the information addressed to the trailing vehicle  7   a  and containing the traffic signal information on the traffic light by using the rear display unit  97 . 
     In the autonomous driving vehicle information presentation apparatus  300  based on the aspect (3), the traffic signal information obtaining unit  315  obtains the traffic signal information on the traffic light present ahead of the host vehicle M in the direction of advance. The information presentation unit  331  presents the information addressed to the trailing vehicle  7   a  and containing the traffic signal information on the traffic light by using the rear display unit  97 . 
     According to the autonomous driving vehicle information presentation apparatus  300  based on the aspect (3), the host vehicle M can communicate with a traffic participant present around the host vehicle M (trailing vehicle  7   a ) by presenting the information addressed to the trailing vehicle  7   a  and containing the traffic signal information on the traffic light to the occupant in the trailing vehicle  7   a.  This makes it possible to create a smooth traffic environment even when unpredicted traffic congestion occurs. 
     An autonomous driving vehicle information presentation apparatus  300  based on an aspect (4) is the autonomous driving vehicle information presentation apparatus  300  based on any one of the aspects (1) to (3) which further includes a congestion information obtaining unit  313  that obtains congestion information on congestion ahead of the host vehicle M in the direction of advance, and in which the information presentation unit  331  presents the information addressed to the trailing vehicle  7   a  and containing the congestion information by using the rear display unit  97 . 
     In the autonomous driving vehicle information presentation apparatus  300  based on the aspect (4), the congestion information obtaining unit  313  obtains the congestion information on congestion ahead of the host vehicle M in the direction of advance The information presentation unit  331  presents the information addressed to the trailing vehicle  7   a  and containing the congestion information by using the rear display unit  97 . 
     According to the autonomous driving vehicle information presentation apparatus  300  based on the aspect (4), the host vehicle M can communicate with a traffic participant present around the host vehicle M (trailing vehicle  7   a ) by presenting the information addressed to the trailing vehicle  7   a  and containing the congestion information to the occupant in the trailing vehicle  7   a.  This makes it possible to create a smooth traffic environment even when unpredicted traffic congestion occurs. 
     An autonomous driving vehicle information presentation apparatus  300  based on an aspect (5) is the autonomous driving vehicle information presentation apparatus  300  based on any one of the aspects (1) to (4) employing a configuration in which the information presentation unit  331  does not present the information addressed to the trailing vehicle  7   a  when the determination unit  323  determines that the trailing vehicle  7   a  is absent. 
     In the autonomous driving vehicle information presentation apparatus  300  based on the aspect (5), the information presentation unit  331  does not present the information addressed to the trailing vehicle  7   a  when the determination unit  323  determines that the trailing vehicle  7   a  is absent. Here, that “the trailing vehicle  7   a  is absent” is intended to mean that even when the trailing vehicle  7   a  is present behind the host vehicle M, this trailing vehicle  7   a  is assumed to be not present (absent) if the host vehicle-trailing vehicle distance DS is so large (far) that the presence of the trailing vehicle  7   a  can be ignored. 
     According to the autonomous driving vehicle information presentation apparatus  300  based on the aspect (5), the information presentation unit  331  does not present the information addressed to the trailing vehicle  7   a  when the determination unit  323  determines that the trailing vehicle  7   a  is absent. This can prevent a situation where a traffic participant (other than the trailing vehicle  7   a ) present around the host vehicle M is misled by seeing the information addressed to the trailing vehicle  7   a.    
     The autonomous driving vehicle information presentation apparatus  300  based on the aspect (6) is the autonomous driving vehicle information presentation apparatus  300  based on any one of the aspects (1) to (4) in which the information presentation unit  331  presents the information addressed to the trailing vehicle  7   a  via defocused displaying using the rear display unit  97  when the determination unit  323  determines that the trailing vehicle  7   a  is present and the host vehicle-trailing vehicle distance DS calculated by the calculation unit  325  is greater than a predetermined first threshold value DSth01. 
     The autonomous driving vehicle information presentation apparatus  300  based on the aspect (6) is assumed to be in a traveling scene in which the host vehicle-trailing vehicle distance DS is so large that it is difficult for the occupant in the trailing vehicle  7   a  to figure out the traffic situation ahead of the host vehicle M in the direction of advance. Specifically, the information presentation unit  331  presents the information addressed to the trailing vehicle  7   a  via defocused displaying using the rear display unit  97  when the determination unit  323  determines that, the trailing vehicle  7   a  is present and the host vehicle-trailing vehicle distance DS calculated by the calculation unit  325  is greater than the predetermined first threshold value DSth01. 
     Here, the defocused displaying means displaying the information to be presented in an out-of-focus state. 
     In sum, according to the autonomous driving vehicle information presentation apparatus  300  based on the aspect (6), in a traveling scene in which the host vehicle-trailing vehicle distance DS is so large (far) that it is difficult for the occupant in the trailing vehicle  7   a  to figure out the traffic situation ahead of the host vehicle M in the direction of advance, the information addressed to the trailing vehicle  7   a  is presented in an out-of-focus state with the rear display unit  97  included in the host vehicle M. In this way, the occupant in the trailing vehicle  7   a  will concentrate on figuring out the information presented in the out-of-focus state and intently stare at the information. 
     According to the autonomous driving vehicle information presentation apparatus  300  based on the aspect (6), the host vehicle M can communicate with a traffic participant present around the host vehicle M (trailing vehicle  7   a ) by attracting the attention of the occupant in the trailing vehicle  7   a.  This makes it possible to create a smooth traffic environment even when unpredicted traffic congestion occurs. 
     The autonomous driving vehicle information presentation apparatus  300  based on the aspect (7) is the autonomous driving vehicle information presentation apparatus  300  based on any one of the aspects (1) to (4) in which the information presentation unit  331  presents the information addressed to the trailing vehicle  7   a  by using a design when the determination unit  323  determines that the trailing vehicle  7   a  is present and the host vehicle-trailing vehicle distance DS is greater than a predetermined second threshold value DSth02, and presents the information addressed to the trailing vehicle  7   a  by using a character when the host vehicle-trailing vehicle distance DS is smaller than the predetermined second threshold value DSth02. 
     In the autonomous driving vehicle information presentation apparatus  300  based on the aspect (7), the information presentation unit  331  presents the information addressed to the trailing vehicle  7   a  by using a design when the host vehicle-trailing vehicle distance DS is greater than the second threshold value DSth02. On the other hand, the information presentation unit  331  presents the information addressed to the trailing vehicle  7   a  by using a character when the host vehicle-trailing vehicle distance DS is smaller than the second threshold value DSth02. The presented state of the information is thus set in consideration of convenience for the occupant in the trailing vehicle  7   a  to figure out the information. 
     According to the autonomous driving vehicle information presentation apparatus  300  based on the aspect (7), the presented state of the information addressed to the trailing vehicle  7   a  is set in consideration of convenience for the occupant in the trailing vehicle  7   a  to figure out the information. This enables the occupant in the trailing vehicle  7   a  to easily figure out the information addressed to the trailing vehicle  7   a.    
     Thus, the host vehicle M can communicate with a traffic participant present around the host vehicle M (trailing vehicle  7   a ) by facilitating the occupant in the trailing vehicle  7   a  to figure out the information. This makes it possible to create a smooth traffic environment even when unpredicted traffic congestion occurs. 
     An autonomous driving vehicle information presentation apparatus  300  based on an aspect (8) is the autonomous driving vehicle information presentation apparatus  300  based on the aspect (4) employing a configuration in which the information presentation unit  331  presents information addressed to the trailing vehicle  7   a  and containing the congestion information by using one of a plurality of languages including a first language while switching between the languages in turn at predetermined time intervals. 
     In the autonomous driving vehicle information presentation apparatus  300  based on the aspect (8), the information presentation unit  331  presents information addressed to the trailing vehicle  7   a  and containing the congestion information by using one of a plurality of languages including the first language while switching between the languages in turn at predetermined time intervals. 
     According to the autonomous driving vehicle information presentation apparatus  300  based on the aspect (8), even if the occupant in the trailing vehicle  7   a  is a foreigner and unpredicted traffic congestion occurs, the host vehicle M can communicate with the traffic participant present around the host vehicle M by presenting information addressed to the trailing vehicle  7   a  and containing the congestion information by using one of a plurality of languages including the first language while switching between the languages in turn at predetermined time intervals. This makes it possible to create a smooth traffic environment. 
     [Other Embodiments] 
     The plurality of embodiments described above represent examples of embodying the present invention. Therefore, the technical scope of the present invention shall not be interpreted in a limited manner by these embodiments. This is because the present invention can be implemented in various ways without departing from its gist or its main characteristic features. 
     For example, in the description of the autonomous driving vehicle information presentation apparatuses  300  according to the embodiments of the present invention, “leading vehicle” is defined to mean a vehicle that is traveling immediately ahead of the host vehicle M in the same traveling lane as that of the host vehicle M among nearby vehicles and is a following target in the following travel control. However, the present invention is not limited to this example. 
     “Leading vehicle” may be defined to mean vehicles in general traveling ahead of the host vehicle M among the nearby vehicles. “Leading vehicle” in this case also includes a vehicle traveling in a traveling lane different from that of the host vehicle M (the direction of travel is the same as that of the host vehicle M), as well as a vehicle traveling in the same traveling lane as that of the host vehicle M. 
     Also, in the description of the autonomous driving vehicle information presentation apparatuses  300  according to the embodiments of the present invention, “trailing vehicle” is defined to mean a vehicle that is traveling immediately behind the host vehicle M among the nearby vehicles. However, the present invention is not limited to this example. 
     “Trailing vehicle” may be defined to mean vehicles in general traveling behind the host vehicle M among the nearby vehicles. “Trailing vehicle” in this case also includes a vehicle traveling in a traveling lane different from that of the host vehicle M (the direction of travel is the same as that of the host vehicle M), as well as a vehicle traveling in the same traveling lane as that of the host vehicle M. 
     Also, the autonomous driving vehicle information presentation apparatuses  300  according to the embodiments of the present Invention have been described by exemplarily showing the first threshold value DSth01 and the second threshold value DSth02 as values falling within the range of the predetermined distance threshold value DSth. However, the present invention is not limited to this example. A necessary number of threshold values may be set as appropriate as values falling within the range of the predetermined distance threshold value DSth. 
     Also, the autonomous driving vehicle information presentation apparatus  300  based on the aspect (7) has been described by exemplarily showing the configuration that presents the information addressed to the trailing vehicle  7   a  by using a design (representing this information) when the host vehicle-trailing vehicle distance DS is greater than the second threshold value DSth02 (the host vehicle-trailing vehicle distance DS&gt;the second threshold value DSth02). However, the present invention is not limited to this example. 
     As a modification for setting the presented state of the information addressed to the trailing vehicle  7   a  according to the magnitude of the host vehicle-trailing vehicle distance DS calculated by the calculation unit  325 , a configuration may be employed which, for example, increases the size of the presented design as the host vehicle-trailing vehicle distance DS becomes larger (farther). 
     Also, the autonomous driving vehicle information presentation apparatus  300  based on the aspect (7) has been described by exemplarily showing the configuration that presents the information addressed to the trailing vehicle  7   a  by using a character (representing this information) when the host vehicle-trailing vehicle distance DS is smaller than the second threshold value DSth02 (the host vehicle-trailing vehicle distance DS&lt;the second threshold value DSth02). However, the present invention is not limited to this example. 
     As a modification for setting the presented state of the information addressed to the trailing vehicle  7   a  according to the magnitude of the host vehicle-trailing vehicle distance DS calculated by the calculation unit  325 , a configuration may be employed which, for example, increases the size of the presented character as the host vehicle-trailing vehicle distance DS becomes larger (farther). 
     Lastly, some or ail of the above-described configurations, functions, processing units, and so on can be implemented with hardware, for example, by designing them with an integrated circuit. Alternatively, the above-described configurations, functions, and so on may be implemented with software to be used by a processor to interpret and execute programs for implementing the respective functions. The information of the programs for implementing the functions, tables, files, and the like can be held in a recording apparatus such as a memory, a HDD, or a solid state drive (SSD) or a recording medium such as an integrated circuit (IC) card, a secure digital (SD) card, or an optical disk.