Driving support device and driving support method

Abstract

To provide a driving support device that, when another vehicle exhibiting a suspicious behavior is detected, can appropriately perform notification to a driver of a subject vehicle according to the relationship with the another vehicle.SOLUTION: A driving support device 1 comprises: a storage control unit 13 that causes a storage unit 19 to store vehicle to be passed information 191 indicating a vehicle to be passed that a subject vehicle has passed; a behavior detection unit 14 that detects the behavior of a rear vehicle traveling behind the subject vehicle; and a notification control unit 15 that, when the behavior of the rear vehicle is determined to be a suspicious behavior, performs notification to a driver of the subject vehicle. When the vehicle indicated by the vehicle to be passed information 191 and the rear vehicle determined to be exhibiting the suspicious behavior match each other, the notification control unit 15 performs notification in a notification mode different from that when the vehicles do not match each other.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a driving assistance device and a driving assistance method. [Background technology]

[0002] In recent years, tailgating has become a social problem. In addition, a technology is known in which, when a vehicle is tailgated, another vehicle that has tailgated the vehicle is recorded by a drive recorder or the like. As a related technology, Patent Document 1 discloses an information recording device that determines whether the vehicle is tailgated by another vehicle based on an image acquired by an image acquisition unit, and when it is determined that the vehicle is tailgated, causes an image acquisition unit to capture an image of the surroundings of the vehicle. For example, the information recording device analyzes a rear image captured behind the vehicle, and determines that the vehicle is tailgated when the rear vehicle is quite close to the vehicle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-123419 A Summary of the Invention [Problem to be solved by the invention]

[0004] When the vehicle is tailgated by the vehicle behind, the driver of the vehicle must take measures such as moving the vehicle away from the vehicle behind safely and asking the passenger to report the vehicle to the police. Therefore, when the vehicle behind is exhibiting suspicious behavior such as a sudden approach, it is desirable to promptly notify the driver and the passenger. In particular, when the vehicle behind exhibiting suspicious behavior is a vehicle that the vehicle behind has overtaken or passed in advance, the driver of the vehicle behind may be dissatisfied or malicious about the act of the vehicle behind overtaking. In such a case, the possibility of being tailgated by the vehicle behind increases, so it is desirable to notify the driver and the passenger at an earlier timing. The technology disclosed in Patent Document 1 does not mention such a problem.

[0005] In consideration of the above-mentioned problems, an object of the present disclosure is to provide a driving assistance device and a driving assistance method that, when a vehicle exhibiting suspicious behavior is detected, can appropriately alert occupants of the vehicle in accordance with the relationship with the other vehicle. [Means for solving the problem]

[0006] The driving assistance device according to the present disclosure comprises: a storage control unit that stores in a storage unit overtaken vehicle information indicating a vehicle that the host vehicle has overtaken or been overtaken by; a behavior detection unit that detects the behavior of a rear vehicle traveling behind the host vehicle; a notification control unit that notifies an occupant of the host vehicle when the behavior of the rear vehicle is determined to be suspicious; Equipped with When the vehicle indicated by the overtaken vehicle information matches the rear vehicle whose suspicious behavior has been determined, the notification control unit issues the notification in a manner different from that when there is no match.

[0007] The driving assistance method according to the present disclosure includes: The computer a storage control step of storing, in a storage unit, overtaken vehicle information indicating a overtaken vehicle that the host vehicle has overtaken or been overtaken by; a behavior detection step of detecting a behavior of a rear vehicle traveling behind the host vehicle; a notification control step of notifying an occupant of the host vehicle when the behavior of the rear vehicle is determined to be suspicious; Run In the notification control step, when the vehicle indicated by the overtaken vehicle information matches the rear vehicle whose suspicious behavior has been determined, the notification is made in a different manner than when there is no match. Effect of the Invention

[0008] The driving assistance device and driving assistance method disclosed herein make it possible, when another vehicle exhibiting suspicious behavior is detected, to appropriately notify occupants of the vehicle in accordance with the vehicle's relationship with the other vehicle. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a top view of the host vehicle according to the first embodiment. [Diagram 2] 1 is a block diagram showing a functional configuration of a driving assistance system according to a first embodiment. [Diagram 3] 5 is a flowchart showing a process performed by the driving assistance device according to the first embodiment until the vehicle to be overtaken is stored. [Figure 4] 5 is a flowchart showing a process performed by the driving assistance device according to the first embodiment until the device issues a notification. [Diagram 5] FIG. 11 is a block diagram showing a functional configuration of a driving assistance system according to a second embodiment. [Figure 6] 10 is a flowchart showing a process performed by a driving assistance device according to a second embodiment until the device stores a vehicle to be overtaken. [Figure 7] 10 is a flowchart showing a process performed by a driving assistance device according to a second embodiment until the device issues a notification. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In each drawing, the same or corresponding elements are denoted by the same reference numerals. For clarity of explanation, duplicate explanations will be omitted as necessary.

[0011] <Embodiment 1> An overview of a driving assistance system 10 according to this embodiment will be described with reference to Fig. 1. Fig. 1 is a top view of the vehicle 2 according to this embodiment. The vehicle 2 is equipped with the driving assistance system 10 including a driving assistance device 1. The driving assistance system 10 mainly comprises the driving assistance device 1, a display unit 31, an audio output unit 32, a front camera C1, and a rear camera C2. The driving assistance device 1 is installed at an arbitrary position of the vehicle 2, and appropriately controls each component of the driving assistance system 10. The display unit 31 and the audio output unit 32 function as a notification unit 3 described later.

[0012] The driving assistance system 10 is a system that, when a suspicious behavior is determined in a rear vehicle traveling behind the vehicle 2, can issue a notification in a different notification manner depending on whether the rear vehicle is a vehicle that the vehicle 2 has overtaken or has not overtaken. The notification manner includes a determination condition for whether or not to issue a notification. The notification manner may also include the content of the notification.

[0013] Here, "suspicious behavior" refers to behavior that may cause danger to the vehicle 2. Suspicious behavior includes driving methods that are a sign of so-called tailgating, and behavior that is difficult to judge as tailgating. Tailgating, also called obstructive driving, refers to dangerous driving that intimidates and provokes surrounding vehicles, causing fear and intimidation. Tailgating may refer to suspicious behavior that is judged to be relatively malicious. Examples of suspicious behavior include continuing to drive in an abnormally close state to the vehicle 2, approaching the vehicle 2 suddenly, meandering, or blinking headlights or brake lights. Not limited to these, suspicious behavior may include various driving methods that may obstruct the driving of the vehicle 2. Suspicious behavior may be a combination of multiple driving methods among these. Suspicious behavior is not limited to behavior during driving, but may also include behavior of occupants of other vehicles while stopped or parked. For example, suspicious behavior may include behavior such as an occupant of the rear vehicle getting out of the vehicle and approaching the host vehicle 2 when the host vehicle 2 and the rear vehicle are stopped at a red light or the like.

[0014] Moreover, "overtaking" indicates that the host vehicle 2, which is a vehicle following the vehicle in front, changes lanes from the host vehicle's own lane to an adjacent lane, gets ahead of the vehicle in front on the adjacent lane, and then changes lanes back to the original lane. Moreover, "overtaking" indicates that the host vehicle 2 gets ahead of the vehicle in front without changing lanes. In this disclosure, a vehicle that the host vehicle 2 has overtaken or been overtaken by may be referred to as a "vehicle being overtaken." Furthermore, in this disclosure, a vehicle that the host vehicle 2 has neither overtaken nor been overtaken by may be referred to as a "normal vehicle."

[0015] In addition, in the present disclosure, vehicles other than the host vehicle 2 may be referred to as "other vehicles." The other vehicles are vehicles that exist around the host vehicle 2. The host vehicle 2 and the other vehicles may be various vehicles such as automobiles, motorcycles, mopeds, and bicycles. The host vehicle 2 and the other vehicles may be commercial vehicles such as buses, trucks, or taxis, or may be privately owned automobiles. There may be multiple other vehicles around the host vehicle 2.

[0016] The driver of the overtaken vehicle may be dissatisfied or malicious about being overtaken or passed by the vehicle 2. Therefore, when the vehicle behind the vehicle 2 is the overtaken vehicle, the risk of the vehicle 2 being tailgated is higher than when the vehicle behind is a normal vehicle. The risk indicates the likelihood that the vehicle 2 will be tailgated by another vehicle. Therefore, when the vehicle behind exhibits suspicious behavior, such as closing the distance between the vehicles, the driving assistance system 10 issues a notification in a different manner depending on whether the vehicle behind the vehicle is the overtaken vehicle or a normal vehicle.

[0017] Specifically, the driving assistance system 10 captures images of the surroundings of the vehicle 2 using a front camera C1 and a rear camera C2, and outputs the captured images to the driving assistance device 1. The driving assistance device 1 detects other vehicles included in the captured images. When the vehicle 2 overtakes or is overtaken by another vehicle, the driving assistance device 1 stores overtaken vehicle information indicating the overtaken vehicle in a storage unit based on the captured images. The overtaken vehicle information is information indicating the characteristics of the overtaken vehicle. The overtaken vehicle information may include, for example, information such as the vehicle number, shape, or color of the overtaken vehicle. The overtaken vehicle information may include other information related to the overtaken vehicle. The driving assistance device 1 accumulates the overtaken vehicle information every time the driving assistance device 1 overtakes or is overtaken by another vehicle.

[0018] Furthermore, the driving assistance device 1 determines suspicious behavior of a rear vehicle traveling behind the vehicle 2 based on the captured image. When suspicious behavior of the rear vehicle is determined, the driving assistance device 1 notifies the occupants of the vehicle 2 using the display unit 31 and the audio output unit 32. The occupants are, for example, the driver of the vehicle 2. The occupants may include fellow passengers. Note that, when the driving assistance device 1 is connected to a communication network (not shown), the driving assistance device 1 may notify people other than the occupants via the communication network.

[0019] When the vehicle indicated by the overtaken vehicle information stored in the storage unit matches the rear vehicle determined to be behaving suspiciously, the driving support device 1 issues a notification in a different manner from when the vehicle does not match. In other words, the driving support device 1 issues a different notification depending on whether the rear vehicle is an overtaken vehicle or a normal vehicle.

[0020] Specifically, when the rear vehicle is an overtaken vehicle, the driving support device 1 issues a notification earlier than when the rear vehicle is a normal vehicle. For example, when issuing a notification when the inter-vehicle distance falls below a predetermined threshold, the driving support device 1 uses different thresholds for the overtaken vehicle and the normal vehicle. This allows the driving support device 1 to issue a notification when the inter-vehicle distance is longer for the overtaken vehicle than for the normal vehicle, in other words, when the rear vehicle has not yet closed the inter-vehicle distance to the vehicle 2 very much.

[0021] In this way, the driving support device 1 can increase the sensitivity of the notification regarding tailgating by controlling the timing of the notification according to the risk of tailgating. This allows the occupants of the vehicle 2 to quickly respond to the rear vehicle exhibiting suspicious behavior.

[0022] (Driver Assistance System 10) Next, the configuration of the driving assistance system 10 will be described in detail with reference to Fig. 2. Fig. 2 is a block diagram showing the functional configuration of the driving assistance system 10. The driving assistance system 10 includes a driving assistance device 1, a front camera C1, a rear camera C2, and a notification unit 3.

[0023] (Front camera C1 and rear camera C2) The front camera C1 and the rear camera C2 are imaging devices that take images in a predetermined direction. The front camera C1 and the rear camera C2 take images of other vehicles traveling around the host vehicle 2. The front camera C1 is provided in a position where it can take images of the area in front of the host vehicle 2, and takes images of the area in front of the host vehicle 2. The front camera C1 takes images of the vehicle in front when the host vehicle 2 is overtaking or passing the vehicle in front. The rear camera C2 is provided in a position where it can take images of the area behind the host vehicle 2, and takes images of the area behind the host vehicle 2. The rear camera C2 takes images of the vehicle behind the host vehicle 2.

[0024] The front camera C1 and the rear camera C2 output the captured images to the driving support device 1. The captured images captured by the front camera C1 and the rear camera C2 may be still images or moving images. In this disclosure, the term "image" includes cases where it means image data that is the data of the image. In other words, the captured images captured by the front camera C1 and the rear camera C2 include cases where it means "image data of the captured image."

[0025] The front camera C1 and the rear camera C2 may take images at a predetermined time interval and output the captured images to the driving assistance device 1. The front camera C1 and the rear camera C2 may be, for example, a panoramic camera capable of capturing images of the surroundings of the vehicle 2 with a 360-degree angle of view. Note that, although the front camera C1 and the rear camera C2 are used for the description here, the number of cameras is not limited to two. For example, the driving assistance system 10 may further include a left camera that captures the left side of the vehicle 2 and a right camera that captures the right side of the vehicle 2. The number of cameras may be one. For example, the driving assistance system 10 may include one camera that can capture images of the front and rear of the vehicle 2.

[0026] Further, the driving assistance system 10 may include a distance measurement sensor capable of scanning the surrounding space three-dimensionally instead of the front camera C1 and the rear camera C2, or together with these cameras. The distance measurement sensor is a sensor that measures the distance to an object present around the vehicle 2. The distance measurement sensor may be, for example, a LiDAR (Light Detection and Ranging, Laser Imaging Detection and Ranging). The distance measurement sensor scans the LiDAR in all directions and acquires three-dimensional point cloud data of objects around the vehicle. The distance measurement sensor outputs the acquired three-dimensional point cloud data to the driving assistance device 1.

[0027] In addition to LiDAR, the driving assistance system 10 may include various sensors capable of measuring the distance to an object as a distance measurement sensor, such as a stereo camera, a ToF (Time of Flight) camera, a millimeter wave radar, etc. The distance measurement sensor may also have the functions of the front camera C1 and the rear camera C2 described above. By using the front camera C1, the rear camera C2, and the distance measurement sensor in combination, the recognition accuracy of surrounding vehicles can be improved.

[0028] The vehicle 2 may include a microphone (not shown). The microphone acquires audio information around the vehicle 2 and outputs the audio information to the driving support device 1. This allows the driving support device 1 to acquire the audio information together with images captured by the front camera C1 and the rear camera C2.

[0029] (Notification Unit 3) The notification unit 3 issues a notification to the occupants of the vehicle 2 under the control of the notification control unit 15. The notification unit 3 includes a display unit 31 and an audio output unit 32. The display unit 31 is a display device that outputs display information for notifying the occupants. The display unit 31 is, for example, a display or a lamp. The display unit 31 is provided in a position visible to the occupants. The display unit 31 is configured to be able to present information to the driver by being provided, for example, on a dashboard. The display unit 31 may be a display with a touch panel that allows input operations to be performed by touching it with a finger or the like.

[0030] The audio output unit 32 is an audio output device that outputs audio information for notifying the occupant, and is, for example, a speaker or a buzzer.

[0031] (Driving assistance device 1) The driving assistance device 1 includes an acquisition unit 11, an image processing unit 12, a memory control unit 13, a behavior detection unit 14, a notification control unit 15, and a memory unit 19. The driving assistance device 1 may be configured, for example, as a PC (Personal Computer), a mobile device, or an in-vehicle device.

[0032] The driving assistance device 1 includes a processor and a memory (such as a semiconductor memory) as components not shown. A computer program in which the processing according to this embodiment is implemented is stored in a storage unit 19 configured with a storage device such as a semiconductor memory. The processor can load the computer program from the storage unit 19 into the memory and execute the computer program. In this way, the processor realizes various functions of the acquisition unit 11, the image processing unit 12, the storage control unit 13, the behavior detection unit 14, and the notification control unit 15.

[0033] Alternatively, the acquisition unit 11, the image processing unit 12, the memory control unit 13, the behavior detection unit 14, and the notification control unit 15 may each be realized by dedicated hardware. In addition, a part or all of each component may be realized by a general-purpose or dedicated circuit, processor, etc., or a combination of these. These may be configured by a single chip, or may be configured by multiple chips connected via a bus. A part or all of each component may be realized by a combination of the above-mentioned circuits, etc., and a program. In addition, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an FPGA (field-programmable gate array), a quantum processor (quantum computer control chip), etc. can be used as the processor.

[0034] Furthermore, when some or all of the components of the driving assistance device 1 are realized by a plurality of information processing devices, circuits, etc., the plurality of information processing devices, circuits, etc. may be centrally arranged or distributed. For example, the information processing devices, circuits, etc. may be realized in a form in which each is connected via a communication network, such as a client-server system or a cloud computing system. Furthermore, the functions of the driving assistance device 1 may be provided in a SaaS (Software as a Service) format.

[0035] The acquisition unit 11 acquires information about vehicles around the host vehicle 2. The information about vehicles around the host vehicle 2 is, for example, sensor information acquired by a sensor provided on the host vehicle 2. The sensor information is, for example, captured images acquired by a camera. The sensor information may be distance measurement data acquired by a stereo camera or the like. Here, the acquisition unit 11 acquires captured images from the front camera C1 and the rear camera C2 as information about the situation around the host vehicle 2.

[0036] The acquisition unit 11 may also acquire information regarding the vehicle 2. For example, the acquisition unit 11 acquires the position information of the vehicle 2 using a position sensor (not shown). The position sensor is configured to perform positioning using a technology such as a Global Navigation Satellite System (GNSS) including a Global Positioning System (GPS).

[0037] The image processing unit 12 judges whether the host vehicle 2 has overtaken or been overtaken by another vehicle. The image processing unit 12 makes this judgment using a known image recognition technique, such as pattern matching, based on the captured image. The image processing unit 12 also extracts overtaken vehicle information indicating characteristics of the overtaken vehicle that the host vehicle 2 has overtaken or been overtaken by, based on the captured image. The image processing unit 12 outputs the extracted overtaken vehicle information to the storage control unit 13. The overtaken vehicle information may be the captured image itself. The overtaken vehicle information is stored in the storage unit 19 as overtaken vehicle information 191.

[0038] The overtaken vehicle information 191 includes, for example, information obtained from the appearance of the overtaken vehicle. The overtaken vehicle information 191 is, for example, information such as the vehicle number, shape, or color of the overtaken vehicle. The overtaken vehicle information 191 may include information on the vehicle type and vehicle manufacturer of the overtaken vehicle. The vehicle type of the overtaken vehicle may be indicated by the vehicle name (model), or may be indicated by the vehicle model name or vehicle type (sedan, wagon, minivan, sports type, truck, etc.).

[0039] The above-mentioned example is merely an example, and the overtaken vehicle information 191 may include other information. The overtaken vehicle information 191 may include facial features of the driver and passengers of the overtaken vehicle. The overtaken vehicle information 191 may also include the number of passengers, the gender and estimated age of the driver, which are the results of face recognition of the driver and passengers of the overtaken vehicle. The overtaken vehicle information 191 may also include a photographed image of the overtaken vehicle.

[0040] The image processing unit 12 extracts the overtaken vehicle information 191 from the captured image, for example, using a known image recognition technique. The image processing unit 12 may specify the overtaken vehicle based on the time difference between a vehicle captured in an image captured by the front camera C1 and a vehicle captured in an image captured by the rear camera C2, and extract the overtaken vehicle information 191 indicating the characteristics of the specified vehicle. The image processing unit 12 may also specify the overtaken vehicle based on the continuity of the relative positions of the rear vehicle as viewed from the host vehicle 2, and extract the overtaken vehicle information 191 indicating the characteristics of the specified vehicle.

[0041] Furthermore, when the behavior of the rear vehicle is detected by the behavior detection unit 14 described later, the image processing unit 12 extracts the characteristics of the rear vehicle based on the captured image. The characteristics of the rear vehicle are information such as the vehicle number, shape, color, etc., similar to the characteristics of the overtaken vehicle.

[0042] The memory control unit 13 receives the overtaken vehicle information 191 indicating the overtaken vehicle from the image processing unit 12, and stores the overtaken vehicle information 191 in the memory unit 19. The memory control unit 13 may store the overtaken vehicle information 191 in association with date and time information indicating the timing at which the host vehicle 2 overtook or was overtaken. In this manner, the memory control unit 13 can accumulate the overtaken vehicle information 191 as time-series data in association with the timing of overtaking or being overtaken.

[0043] Furthermore, the memory control unit 13 may further store in the memory unit 19 suspicious behavior information 192 regarding suspicious behavior of the rear vehicle determined by the notification control unit 15 described later in association with the overtaken vehicle information 191. The suspicious behavior information 192 includes, for example, captured images showing the suspicious behavior of the rear vehicle. For example, the memory control unit 13 stores, in association with the overtaken vehicle information 191, captured images of a suspicious behavior period indicating a period from the time when the suspicious behavior was determined to the time when the suspicious behavior was no longer determined.

[0044] The memory control unit 13 may retain images captured during a suspicious behavior period for a period different from images captured during periods other than the suspicious behavior period. For example, the memory control unit 13 deletes images captured during periods other than the suspicious behavior period after a predetermined time has elapsed. In contrast, the memory control unit 13 retains images captured during a suspicious behavior period without deleting them even after a predetermined time has elapsed. This allows the memory control unit 13 to retain images captured during a suspicious behavior period for a longer period than images captured during periods other than the suspicious behavior period. In this way, the memory control unit 13 can efficiently use the storage capacity of the memory unit 19.

[0045] In this way, the memory control unit 13 stores the suspicious behavior information 192 and the overtaken vehicle information 191 in association with each other, and further controls so that these pieces of information are not deleted. As a result, the memory control unit 13 can hold in the memory unit 19 not only the captured image at the timing when the rear vehicle behaved suspiciously, but also the captured image before the rear vehicle behaved suspiciously, that is, the captured image at the timing when the host vehicle 2 overtook the rear vehicle, etc. In this way, the driver, etc. of the host vehicle 2 can provide the police, etc. with the captured images from the period before the rear vehicle behaved suspiciously to the period after it behaved suspiciously.

[0046] The behavior detection unit 14 detects the behavior of a rear vehicle traveling behind the host vehicle 2 based on the captured images acquired by the acquisition unit 11. Here, the behavior detection unit 14 detects the behavior of the rear vehicle using a known image recognition technique based on the captured images of the front camera C1 and the rear camera C2. For example, the behavior detection unit 14 detects the distance between the host vehicle 2 and the rear vehicle.

[0047] For example, the behavior detection unit 14 calculates the inter-vehicle distance between the host vehicle 2 and the rear vehicle based on the image size of the license plate of the rear vehicle in the captured image. The behavior detection unit 14 may calculate the inter-vehicle distance by referring to data that associates the image size of the license plate of the rear vehicle in the captured image with the distance to the rear vehicle. The method is not limited to this, and the behavior detection unit 14 may calculate the inter-vehicle distance using other methods. In addition, when the driving assistance system 10 includes a distance measurement sensor such as a stereo camera, the behavior detection unit 14 may calculate the inter-vehicle distance using distance measurement data.

[0048] The behavior detection unit 14 may further determine that the behavior of the rear vehicle is suspicious based on the distance between the host vehicle 2 and the rear vehicle. For example, the behavior detection unit 14 determines the suspicious behavior of the rear vehicle based on the distance between the vehicles using the methods shown in the following two examples. Note that the process of determining the suspicious behavior of the rear vehicle may be executed by the notification control unit 15 as described later.

[0049] (1) A method for measuring the duration of a state in which the host vehicle 2 and a rear vehicle are in close proximity to each other The behavior detection unit 14 judges whether the state in which the host vehicle 2 and the rear vehicle are abnormally close to each other continues for a predetermined time, and judges the suspicious behavior of the rear vehicle according to the judgment result. Specifically, the behavior detection unit 14 first detects the distance between the host vehicle 2 and the rear vehicle based on the captured image. Next, the behavior detection unit 14 judges whether the distance between the vehicles is equal to or less than the distance threshold. If it is judged that the distance between the vehicles is equal to or less than the distance threshold, the behavior detection unit 14 measures the duration of the state in which the distance between the vehicles is equal to or less than the distance threshold using a timer (not shown). Next, the behavior detection unit 14 judges whether the state in which the distance between the vehicles is equal to or less than the distance threshold continues for a time threshold or more. If the state continues for a time threshold or more, the behavior detection unit 14 judges that the rear vehicle has abnormally approached the host vehicle 2 and is behaving suspiciously. The distance threshold and the time threshold are set by the notification control unit 15 described later.

[0050] (2) A method for determining whether a rear vehicle has suddenly approached the host vehicle 2 The behavior detection unit 14 determines whether a rear vehicle has suddenly approached the host vehicle 2, and determines suspicious behavior of the rear vehicle according to the determination result. Specifically, the behavior detection unit 14 first calculates the relative speed between the host vehicle 2 and the rear vehicle based on the captured image. Next, the behavior detection unit 14 determines whether the calculated relative speed is equal to or greater than a speed threshold. If it is determined that the relative speed is equal to or greater than the speed threshold, the behavior detection unit 14 determines that the rear vehicle has suddenly approached the host vehicle 2 and is behaving suspiciously. The speed threshold is set by the notification control unit 15, which will be described later.

[0051] In the method (2), the behavior detection unit 14 may make the determination by taking into consideration whether the inter-vehicle distance between the host vehicle 2 and the rear vehicle is less than the distance threshold. That is, when the behavior detection unit 14 determines that the inter-vehicle distance is less than the distance threshold and the relative speed is equal to or greater than the speed threshold, the behavior detection unit 14 determines that the rear vehicle is behaving suspiciously. The behavior detection unit 14 may also make the determination by taking into consideration the duration of the state in which the host vehicle 2 and the rear vehicle are in close proximity to each other. For example, the behavior detection unit 14 determines that the rear vehicle is behaving suspiciously when the rear vehicle approaches within 5 m behind the host vehicle 2 at a relative speed equal to or greater than the speed threshold and the close state continues for 3 seconds or more.

[0052] In the above-mentioned methods (1) and (2), the vehicle distance is used, but this is not limited thereto. The behavior detection unit 14 may determine the suspicious behavior of the rear vehicle using information other than the vehicle distance. For example, the behavior detection unit 14 determines the suspicious behavior based on information other than the vehicle distance, as shown in the following two examples.

[0053] (3) Method for determining whether the rear vehicle is swerving The behavior detection unit 14 judges whether the rear vehicle is meandering, and judges the suspicious behavior of the rear vehicle according to the judgment result. Specifically, the behavior detection unit 14 first detects the lateral sway of the rear vehicle using a known image recognition technology based on the captured image. The lateral direction indicates the vehicle width direction of the host vehicle 2. Next, the behavior detection unit 14 judges whether the magnitude of the lateral sway of the rear vehicle is equal to or greater than a sway threshold. If it is judged that the magnitude of the lateral sway of the rear vehicle is equal to or greater than the sway threshold, the behavior detection unit 14 judges that the rear vehicle is meandering. In this case, the behavior detection unit 14 judges that the rear vehicle is behaving suspiciously. The sway threshold is set by the notification control unit 15, which will be described later.

[0054] (4) A method for determining whether an occupant of a rear vehicle has behaved suspiciously The behavior detection unit 14 judges whether or not the occupant of the rear vehicle has behaved suspiciously, and judges the suspicious behavior of the rear vehicle according to the judgment result. Specifically, the behavior detection unit 14 first detects the behavior of the occupant of the rear vehicle based on the captured image. For example, when stopped at a red light or the like, the behavior detection unit 14 detects the movement of the occupant of the rear vehicle getting off and approaching the host vehicle 2. In such a case, the behavior detection unit 14 judges that the occupant of the rear vehicle has behaved suspiciously. The behavior detection unit 14 also judges that the rear vehicle is behaving suspiciously. Note that the behavior detection unit 14 may detect the behavior of the occupant of the rear vehicle not only when stopped but also when traveling.

[0055] The above examples (1) to (4) are merely examples of suspicious behavior, and the behavior detection unit 14 may determine whether the behavior is suspicious by using other behavior of the rear vehicle or the occupants of the rear vehicle.

[0056] The notification control unit 15 determines the suspicious behavior of the rear vehicle based on the behavior of the rear vehicle detected by the behavior detection unit 14. For example, the notification control unit 15 determines the suspicious behavior of the rear vehicle based on any one of the following distance from the rear vehicle, the meandering driving of the rear vehicle, and the suspicious behavior of the occupant of the rear vehicle, using the method shown in the four examples shown in the behavior detection unit 14 described above. When the suspicious behavior of the rear vehicle is determined, the notification control unit 15 issues a notification to the occupant of the host vehicle 2. When the vehicle indicated by the overtaken vehicle information 191 and the rear vehicle whose suspicious behavior is determined match, the notification control unit 15 issues a notification in a different manner from when they do not match.

[0057] Specifically, the notification control unit 15 acquires the characteristics of the rear vehicle whose suspicious behavior has been determined via the image processing unit 12. The notification control unit 15 refers to the overtaken vehicle information 191 and determines whether or not the overtaken vehicle information 191 contains characteristics that match the characteristics of the rear vehicle whose suspicious behavior has been determined. If there are matching characteristics, the notification control unit 15 determines that the rear vehicle is an overtaken vehicle. If there are no matching characteristics, the notification control unit 15 determines that the rear vehicle is a normal vehicle. The notification control unit 15 issues a notification in a different manner depending on whether the rear vehicle is an overtaken vehicle or a normal vehicle.

[0058] For example, the notification control unit 15 determines whether the inter-vehicle distance between the host vehicle 2 and the rear vehicle is less than a predetermined distance threshold, and issues a notification when it is determined that the inter-vehicle distance is less than the distance threshold. The distance threshold is a value related to the inter-vehicle distance between the host vehicle 2 and the rear vehicle. When the vehicle indicated by the overtaken vehicle information 191 and the rear vehicle whose suspicious behavior is determined match, the notification control unit 15 sets a larger distance threshold than when they do not match. When the vehicle indicated by the overtaken vehicle information 191 and the rear vehicle whose suspicious behavior is determined match, the notification control unit 15 may set a shorter time threshold than when they do not match, and when the vehicle indicated by the overtaken vehicle information 191 and the rear vehicle whose suspicious behavior is determined match, the notification control unit 15 may set a slower speed threshold or a smaller sway threshold than when they do not match. This allows the notification control unit 15 to increase the sensitivity of the determination as to whether or not to issue a notification. When the rear vehicle behaving suspiciously is a vehicle being overtaken, the notification control unit 15 can notify the occupants of the vehicle 2 at an earlier timing than when the rear vehicle behaving suspiciously is a normal vehicle.

[0059] A specific example will be used for explanation. For example, when the rear vehicle continues to be abnormally close to the vehicle 2 or when the rear vehicle suddenly approaches the vehicle 2, the behavior detection unit 14 judges the suspicious behavior of the rear vehicle as described above. The notification control unit 15 acquires the characteristics of the rear vehicle from the image processing unit 12 based on the captured image of the rear vehicle. For example, the notification control unit 15 acquires the vehicle number of the rear vehicle. The notification control unit 15 refers to the overtaken vehicle information 191 and judges whether or not the overtaken vehicle information 191 contains a number that matches the vehicle number of the acquired rear vehicle.

[0060] It is assumed that the notification control unit 15 determines that the overtaken vehicle information 191 contains a number that matches the acquired vehicle number of the rear vehicle. In this case, the rear vehicle is a vehicle that the host vehicle 2 has previously overtaken or been overtaken by. In addition, it is assumed that the notification control unit 15 determines that the overtaken vehicle information 191 does not contain a number that matches the acquired vehicle number of the rear vehicle. In this case, the rear vehicle is a normal vehicle that the host vehicle 2 has not previously overtaken or been overtaken by.

[0061] The notification control unit 15 sets a different distance threshold depending on whether the rear vehicle is an overtaken vehicle or a normal vehicle, and uses the set distance threshold to determine whether or not to issue a notification. For example, the notification control unit 15 determines to issue a notification when the inter-vehicle distance between the vehicle 2 and the rear vehicle is less than the distance threshold, and determines not to issue a notification when the inter-vehicle distance is equal to or greater than the distance threshold. The notification control unit 15 may set a time threshold, a speed threshold, and a shaking threshold in a similar manner.

[0062] For example, the notification control unit 15 sets the distance threshold to 50 m when the rear vehicle is a normal vehicle, and sets the distance threshold to 70 m when the rear vehicle is an overtaken vehicle. Here, assume that the distance between the vehicle 2 and the rear vehicle is 60 m. When the rear vehicle is a normal vehicle, the distance between the vehicles is greater than the distance threshold of 50 m. Therefore, in this case, the notification control unit 15 determines not to issue a notification. On the other hand, when the rear vehicle is an overtaken vehicle, the vehicle distance is less than the distance threshold of 70 m. Therefore, in this case, the notification control unit 15 determines to issue a notification. In this way, when the rear vehicle is an overtaken vehicle, the notification control unit 15 can issue a notification at an earlier timing than when the rear vehicle is a normal vehicle, and the sensitivity of the notification of tailgating can be increased.

[0063] Here, the notification control unit 15 judges whether the rear vehicle is an overtaken vehicle using the vehicle number, but this is not limited to the above. The notification control unit 15 may also make the judgment by taking into account the shape and color of the body of the rear vehicle. The notification control unit 15 may judge that the rear vehicle is an overtaken vehicle not only when the vehicle number, shape, etc. of the rear vehicle completely match the information included in the overtaken vehicle information 191, but also when they are similar by a predetermined value or more.

[0064] When it is determined that a notification should be made, the notification control unit 15 generates notification information for making the notification. The notification information may include, for example, text information or audio information. For example, the notification control unit 15 generates notification information for displaying a warning such as "the overtaken vehicle is rapidly approaching". The notification control unit 15 outputs the generated notification information to the notification unit 3. The notification control unit 15 causes the notification unit 3 to output the notification information using the display information or audio information. The notification control unit 15 may control the notification mode, such as the volume of the audio output for notification, the number of times the audio output is performed, the form of the characters or images displayed on the display unit 31, and the brightness and blinking speed of the lamp. For example, when the vehicle indicated by the overtaken vehicle information 191 matches the rear vehicle whose suspicious behavior has been determined, the notification control unit 15 increases the volume of the audio output for notification and increases the blinking speed of the lamp for notification, compared to when they do not match, thereby making it easier for the occupants of the vehicle 2 to sense the notification regarding tailgating.

[0065] The notification control unit 15 may also control the notification mode depending on the level of risk of the host vehicle 2 being subjected to tailgating. For example, the notification control unit 15 controls the notification mode based on the time that has elapsed since the host vehicle 2 overtook or passed the vehicle being overtaken. If the time that has elapsed since the overtaking or passing has been short, there is a high possibility that the driver of the vehicle behind, which is the vehicle being overtaken, is dissatisfied or malicious toward the host vehicle 2. Therefore, in this case, the notification control unit 15 determines that the host vehicle 2 is at high risk of being subjected to tailgating, and controls the notification mode depending on the level of risk.

[0066] Specifically, the notification control unit 15 first refers to the overtaken vehicle information 191 and identifies the timing at which the host vehicle 2 overtook or passed the rear vehicle determined to be behaving suspiciously. The notification control unit 15 calculates the elapsed time from that timing, and determines whether the calculated elapsed time is less than a predetermined time threshold. If it is less than the time threshold, the notification control unit 15 determines that the risk is high. The notification control unit 15 may calculate multiple levels of risk, such as "high," "medium," and "low," depending on the elapsed time.

[0067] For example, the notification control unit 15 controls the notification mode by generating different notification information according to the level of danger. For example, when the level of danger is low, the notification control unit 15 generates the notification information using only text information, and when the level of danger is high, the notification information uses voice information in addition to the text information. The notification control unit 15 may generate the notification information so that the volume of the voice output for notification, the number of times the voice output is performed, the mode of the characters and images displayed on the display unit 31, and the brightness and blinking speed of the lamp are changed according to the level of danger, to set the notification mode to indicate a high level of danger to the occupants of the vehicle 2.

[0068] The storage unit 19 stores the above-mentioned overtaken vehicle information 191 and suspicious behavior information 192. The storage unit 19 may also store a computer program in which the processing of the driving assistance method according to the present embodiment is implemented. The storage unit 19 is configured with, for example, a semiconductor memory. At least a part of the storage unit 19 is configured with a non-volatile memory so that data is retained even when the driving assistance device 1 is turned off.

[0069] The configuration of the driving assistance system 10 has been described above. Note that the above-mentioned configuration of the driving assistance system 10 is merely an example and may be changed as appropriate. For example, in the above description, an example in which the driving assistance device 1 is provided in the vehicle 2 has been shown, but this is not limiting. The driving assistance device 1 may be provided in an external server. For example, the vehicle 2 and the external server are connected by a communication network (not shown), and the vehicle 2 transmits sensor information such as captured images to the external server via a communication unit (not shown). As a result, the external server may perform processing related to the driving assistance device 1 and transmit notification information to the vehicle 2.

[0070] (Processing of driving support device 1) Next, the process performed by the driving support device 1 will be described with reference to Fig. 3 and Fig. 4. Fig. 3 is a flowchart showing the process performed by the driving support device 1 until the driving support device 1 stores the overtaken vehicle. Fig. 4 is a flowchart showing the process performed by the driving support device 1 until the driving support device 1 issues a notification.

[0071] First, referring to Fig. 3, the process up to when the driving support device 1 stores the overtaken vehicle will be described. The acquisition unit 11 acquires a captured image from the front camera C1 (S11). The image processing unit 12 judges whether the host vehicle 2 has overtaken or been overtaken by another vehicle (S12). The image processing unit 12 makes this judgment using a known image recognition technique or the like. If it is determined that the host vehicle 2 has not overtaken or been overtaken (NO in S12), the driving support device 1 returns to step S11 and repeats the process.

[0072] When it is determined that overtaking or being overtaken has occurred (YES in S12), the acquisition unit 11 acquires a captured image from the rear camera C2 (S13). The image processing unit 12 extracts overtaken vehicle information 191 indicating characteristics of the overtaken vehicle that the host vehicle 2 has overtaken or been overtaken based on the captured image (S14). The overtaken vehicle information 191 is information indicating, for example, the vehicle number, shape, or color of the overtaken vehicle. The memory control unit 13 stores the overtaken vehicle information 191 in the memory unit 19 (S15).

[0073] Next, the process up to when the driving support device 1 issues a notification will be described with reference to Fig. 4. It is assumed that the acquisition unit 11 acquires images captured by the rear camera C2 at all times. It is also assumed here that an initial value of the distance threshold for determining whether or not to issue a notification is set. The initial value is a distance threshold used when the rear vehicle determined to be behaving suspiciously is a normal vehicle that the host vehicle 2 has not overtaken or is not passing.

[0074] The notification control unit 15 judges suspicious behavior of a rear vehicle traveling behind the vehicle 2 based on the captured image (S21). For example, the notification control unit 15 judges suspicious behavior of the rear vehicle based on the vehicle-to-vehicle distance between the vehicle 2 and the rear vehicle detected by the behavior detection unit 14. The notification control unit 15 judges whether the state in which the vehicle 2 and the rear vehicle are abnormally close to each other continues for a predetermined time, and judges the behavior as suspicious according to the judgment result. The notification control unit 15 may also judge whether the rear vehicle has suddenly approached the vehicle 2, and judge the behavior of the rear vehicle as suspicious according to the judgment result. Furthermore, the notification control unit 15 may judge whether the rear vehicle is meandering, and judge the behavior of the rear vehicle as suspicious according to the judgment result. Without being limited to these, the notification control unit 15 may, for example, judge whether an occupant of the rear vehicle has behaved suspiciously, and judge the behavior of the rear vehicle as suspicious according to the judgment result.

[0075] If the behavior of the rear vehicle is not determined to be suspicious (NO in S21), the driving support device 1 returns to step S21 and repeats the process. If the behavior of the rear vehicle is determined to be suspicious (YES in S21), the notification control unit 15 determines whether the rear vehicle is an overtaken vehicle (S22). Specifically, the notification control unit 15 refers to the overtaken vehicle information 191 and determines whether the characteristics of the vehicle indicated by the overtaken vehicle information 191 match the characteristics of the rear vehicle determined to be behaving suspiciously.

[0076] If the notification control unit 15 determines that the rear vehicle is not an overtaken vehicle, that is, that the rear vehicle is a normal vehicle (NO in S22), the notification control unit 15 proceeds to step S24. If the notification control unit 15 determines that the rear vehicle is an overtaken vehicle (YES in S22), the notification control unit 15 changes the distance threshold from the initial value (S23). Specifically, the notification control unit 15 sets the distance threshold to a value greater than the initial value.

[0077] The notification control unit 15 determines whether the distance between the host vehicle 2 and the rear vehicle is less than the distance threshold (S24). If it is determined that the distance between the vehicles is equal to or greater than the distance threshold (NO in S24), the driving support device 1 ends the process. Note that the driving support device 1 may repeat the process of step S24 until the rear vehicle is no longer captured in the captured image, for example.

[0078] When it is determined that the inter-vehicle distance is less than the distance threshold value (YES in S24), the notification control unit 15 determines to issue a notification and controls the manner of notification to notify the occupants of the host vehicle 2 that the overtaken vehicle is approaching the host vehicle 2 from behind (S25). Specifically, the notification control unit 15 generates notification information for issuing a notification and outputs it to the notification unit 3. As a result, the notification control unit 15 causes the notification unit 3 to output the notification information by display information or audio information.

[0079] The memory control unit 13 stores the suspicious behavior information 192 related to the suspicious behavior of the rear vehicle in the memory unit 19 in association with the overtaken vehicle information 191 (S26). This allows the memory control unit 13 to hold in the memory unit 19 not only the image captured at the time when the rear vehicle behaved suspiciously, but also the image captured at the time before the rear vehicle behaved suspiciously.

[0080] As described above, in the driving assistance system 10 according to the present embodiment, when the host vehicle 2 overtakes or is overtaken by another vehicle, the driving assistance device 1 stores the overtaken vehicle information 191 indicating the overtaken vehicle in the storage unit 19. The driving assistance device 1 determines suspicious behavior of the rear vehicle, for example, based on the inter-vehicle distance between the host vehicle 2 and the rear vehicle. When the driving assistance device 1 determines suspicious behavior of the rear vehicle traveling behind the host vehicle 2, it notifies the occupants of the host vehicle 2 based on the overtaken vehicle information 191. When the vehicle indicated by the overtaken vehicle information 191 matches the rear vehicle determined to be behaving suspiciously, the driving assistance device 1 notifies in a manner different from when they do not match.

[0081] For example, the driving assistance device 1 determines whether the distance between the vehicle and the rear vehicle is less than the distance threshold, and notifies the occupants of the vehicle 2 when it is determined that the distance between the vehicle and the rear vehicle is less than the distance threshold. When the vehicle indicated by the overtaken vehicle information 191 matches the rear vehicle determined to be behaving suspiciously, the driving assistance device 1 uses a larger distance threshold to make the determination than when they do not match. This allows the driving assistance device 1 to notify the occupants of the vehicle 2 at an earlier timing when the rear vehicle is an overtaken vehicle than when the rear vehicle is a normal vehicle. In this way, when a vehicle is determined to be behaving suspiciously, the driving assistance system 10 can appropriately notify the occupants of the vehicle 2 according to the relationship with the other vehicle.

[0082] The driving support device 1 can also control the notification mode based on the time that has elapsed since the host vehicle 2 overtook or passed the overtaken vehicle. This allows the driving support device 1 to notify the overtaken vehicle that the host vehicle 2 has just overtaken in a different notification mode from that for the overtaken vehicle that has not been overtaken. This allows the driver of the host vehicle 2 to pay attention to the overtaken vehicle that has just overtaken or passed at an early stage.

[0083] Furthermore, when the driving support device 1 determines that the rear vehicle is behaving suspiciously, the driving support device 1 further stores the suspicious behavior information 192 in the memory unit 19 in association with the overtaken vehicle information 191. This allows the driving support device 1 to hold not only the image captured at the time when the rear vehicle behaved suspiciously, but also the image captured before the suspicious behavior. In this way, the driver of the vehicle 2 or the like can provide the held captured image to the police or the like.

[0084] Also, for example, when a vehicle that the host vehicle 2 has once overtaken passes the host vehicle 2 and attempts to overtake the host vehicle 2 and get in front of the host vehicle 2 to engage in tailgating, the driving support device 1 can determine suspicious behavior such as sudden acceleration of the other vehicle and issue a warning to the host vehicle 2. As a result, the driving support device 1 can issue a warning not only about tailgating from behind the host vehicle 2, but also about tailgating from the front of the host vehicle 2.

[0085] <Embodiment 2> Next, a second embodiment will be described. In the driving assistance system 10 according to the first embodiment, when a suspicious behavior of a rear vehicle is determined, the notification control unit 15 determines whether the rear vehicle is a vehicle to be overtaken, and controls notification according to the determination result. In addition to determining whether the rear vehicle is a vehicle to be overtaken, the driving assistance system 10a according to the present embodiment determines whether the vehicle to be overtaken has indicated an intention to change lanes when the host vehicle 2 overtakes or passes another vehicle. Note that "when the host vehicle 2 overtakes or passes another vehicle" refers to the timing when the host vehicle 2 performs an operation to overtake or pass a vehicle ahead. The timing includes at least a part of the timing from the start to the end of the operation to overtake or pass another vehicle.

[0086] For example, assume that a vehicle ahead of the vehicle 2 intends to change lanes. If the vehicle 2 blocks the lane change of the vehicle ahead and overtakes or passes the vehicle ahead, the driver of the vehicle ahead is likely to be dissatisfied or malicious about the behavior of the vehicle 2. Therefore, when the vehicle behind that is determined to be behaving suspiciously is an overtaken vehicle intending to change lanes, the driving assistance system 10a issues a notification in a different manner from when the vehicle behind is a normal vehicle.

[0087] In the following, differences from the driving assistance system 10 of the first embodiment will be mainly described, and overlapping points will be omitted as appropriate. The overall configuration of the driving assistance system 10a is generally the same as the overall configuration of the driving assistance system 10 shown in Fig. 1. The driving assistance system 10a can be described by replacing the driving assistance system 10 shown in Fig. 1 with the driving assistance system 10a. Therefore, the illustration of the overall configuration of the driving assistance system 10a will be omitted.

[0088] (Driver assistance system 10a) Fig. 5 is a block diagram showing the functional configuration of a driving assistance system 10a according to this embodiment. The driving assistance system 10a includes a driving assistance device 1a, a front camera C1, a rear camera C2, and a notification unit 3. The front camera C1, the rear camera C2, and the notification unit 3 are the same as those described with reference to Fig. 2, and therefore will not be described here.

[0089] The driving assistance device 1a includes an acquisition unit 11, an image processing unit 12a, a memory control unit 13a, a behavior detection unit 14, a notification control unit 15a, and a memory unit 19a. The image processing unit 12a, the memory control unit 13a, the notification control unit 15a, and the memory unit 19a have functions different from those of the image processing unit 12, the memory control unit 13, the notification control unit 15, and the memory unit 19 of the driving assistance system 10, respectively.

[0090] The image processor 12a detects state information indicating the state of the overtaken vehicle when the host vehicle 2 overtakes or is overtaken. At the time when the host vehicle 2 overtakes or is overtaken, the other vehicle has not been specified as the overtaken vehicle. However, for the sake of explanation below, a vehicle that the host vehicle 2 will later overtake or be overtaken may be referred to as the "overtaken vehicle."

[0091] The state information includes information as to whether or not the overtaken vehicle intended to change lanes when the host vehicle 2 overtakes or is overtaken. The image processing unit 12a, for example, uses a known image recognition technique to determine whether or not the overtaken vehicle intended to change lanes, and detects the state information based on the determination result. For example, the image processing unit 12a determines whether or not the overtaken vehicle flashed a turn signal in the lane direction in which the host vehicle 2 is traveling, based on the captured image, when the host vehicle 2 overtakes or is overtaken. If the turn signal was flashing, the image processing unit 12a determines that the overtaken vehicle intended to change lanes.

[0092] The image processing unit 12a may determine whether the vehicle to be overtaken intended to change lanes by using information other than the blinking of the turn signal. For example, the image processing unit 12a may determine whether the vehicle to be overtaken moved in the left-right direction (vehicle width direction), whether the vehicle to be overtaken was trying to cross the center line, and the like. The image processing unit 12a may also determine whether the vehicle to be overtaken was in a state in which it was expected to change lanes. For example, if there is an obstacle or a vehicle parked on the road ahead of the vehicle to be overtaken, the vehicle to be overtaken needs to change lanes to avoid these. Therefore, when an object or the like is extracted ahead of the vehicle to be overtaken, the image processing unit 12a may determine that the vehicle to be overtaken intended to change lanes.

[0093] The status information may include a captured image showing a blinking indicator or the like in addition to information on whether the overtaken vehicle intended to change lanes. The image processing unit 12a outputs the detected status information to the storage control unit 13a. The status information is stored as status information 193 in the storage unit 19a.

[0094] The storage control unit 13a stores in the storage unit 19a, in association with the overtaken vehicle information 191 indicating the overtaken vehicle that the vehicle 2 has overtaken or been overtaken by, and the status information 193 indicating the status of the overtaken vehicle when the vehicle 2 overtakes or is overtaken. The storage control unit 13a may control the overtaken vehicle information 191, the suspicious behavior information 192, and the status information 193 so as not to delete them even after a predetermined period has elapsed, as in the first embodiment. In this way, the driver of the vehicle 2, etc. can provide the police, etc. with the status information 193 including the presence or absence of an intention to change lanes, in addition to the images captured during the period from before the suspicious behavior was exhibited to after the suspicious behavior was exhibited.

[0095] When the suspicious behavior of the rear vehicle is determined, the notification control unit 15a notifies the occupants of the vehicle 2. The notification control unit 15a notifies in different notification modes depending on whether or not a predetermined condition is satisfied. Here, the predetermined condition is that the vehicle indicated by the overtaken vehicle information 191 matches the rear vehicle whose suspicious behavior is determined, and the state information 193 includes the intention of the overtaken vehicle to change lanes. When the above-mentioned predetermined condition is satisfied, the notification control unit 15a notifies in a different notification mode from when the predetermined condition is not satisfied.

[0096] For example, when the above-mentioned predetermined condition is satisfied, the notification control unit 15a issues a notification at an earlier timing than when the condition is not satisfied. The notification control unit 15a may issue a notification using a predetermined distance threshold, as in the first embodiment. The notification control unit 15a judges whether the inter-vehicle distance between the host vehicle 2 and the rear vehicle is less than the predetermined distance threshold, and issues a notification to the occupant of the host vehicle 2 when it is judged that the inter-vehicle distance is less than the distance threshold. When the vehicle indicated by the overtaken vehicle information 191 matches the rear vehicle whose suspicious behavior is judged, and the state information 193 includes the intention of the overtaken vehicle to change lanes, the notification control unit 15a makes a judgment using a distance threshold that is larger than when the state information 193 does not include the intention of the overtaken vehicle to change lanes.

[0097] This allows the notification control unit 15a to increase the sensitivity of the determination as to whether or not to issue a notification. When the rear vehicle behaving suspiciously is a vehicle to be overtaken and the rear vehicle intends to change lanes when overtaking or being overtaken, the notification control unit 15a can issue a notification to the occupants of the host vehicle 2 at an earlier timing than when the rear vehicle did not intend to change lanes.

[0098] The storage unit 19a further stores state information 193 in addition to the overtaken vehicle information 191 and the suspicious behavior information 192 described in the first embodiment.

[0099] (Processing of driving support device 1a) Next, the processing performed by the driving support device 1a will be described with reference to Fig. 6 and Fig. 7. Fig. 6 is a flowchart showing the processing until the driving support device 1a stores the overtaken vehicle. Fig. 7 is a flowchart showing the processing until the driving support device 1a issues a notification. Figs. 6 and 7 correspond to Figs. 3 and 4, respectively. Processing different from that of the first embodiment will be described below.

[0100] The flowchart shown in FIG. 6 differs from the flowchart shown in FIG. 3 in that step S101 is executed between steps S11 and S12, and in that step S102 is executed instead of step S15.

[0101] After step S11, the image processor 12a detects state information 193 (S101). The state information 193 is information indicating the state of the vehicle being overtaken when the host vehicle 2 is overtaking or being overtaken. The state information 193 includes information on whether the vehicle being overtaken intended to change lanes when the host vehicle 2 was overtaking or being overtaken.

[0102] The image processing unit 12a, for example, uses a known image recognition technique to determine whether or not the overtaken vehicle intended to change lanes, and detects the state information 193 based on the determination result. For example, the image processing unit 12a determines whether or not the overtaken vehicle was blinking a turn signal or whether or not the overtaken vehicle was moving in the left or right direction based on the captured image. The image processing unit 12a determines whether or not the overtaken vehicle intended to change lanes based on the determination result.

[0103] After step S14, the storage control unit 13a stores the overtaken vehicle information 191 in association with the status information 193 (S102).

[0104] The flowchart shown in Fig. 7 differs from the flowchart shown in Fig. 4 in that step S111 is executed instead of step S22. After step S21, the notification control unit 15a judges whether or not the rear vehicle is a vehicle to be overtaken and has an intention to change lanes (S111). Specifically, the notification control unit 15a refers to the overtaken vehicle information 191 and judges whether or not the vehicle indicated by the overtaken vehicle information 191 matches the rear vehicle whose suspicious behavior has been determined. In addition, the notification control unit 15a refers to the state information 193 and further judges whether or not the rear vehicle has an intention to change lanes when the host vehicle 2 overtakes or passes another vehicle.

[0105] When the notification control unit 15a determines that the rear vehicle is a vehicle to be overtaken and has an intention to change lanes (YES in S111), the notification control unit 15a advances the process to step S23. When the notification control unit 15a determines that at least one of the following conditions is not met: the rear vehicle is a vehicle to be overtaken and the rear vehicle has an intention to change lanes (NO in S111), the notification control unit 15a advances the process to step S24. The processes other than those described above are the same as those in the first embodiment, and therefore will not be described.

[0106] As described above, in the driving assistance system 10a according to this embodiment, the driving assistance device 1a stores in the storage unit 19, in association with the overtaken vehicle information 191 indicating the overtaken vehicle that the host vehicle 2 has overtaken or been overtaken, and the state information 193 indicating the state of the overtaken vehicle when the host vehicle 2 overtakes or is overtaken. Furthermore, when the vehicle indicated by the overtaken vehicle information 191 matches the rear vehicle whose suspicious behavior has been determined and the state information 193 includes the overtaken vehicle's intention to change lanes, the driving assistance device 1a issues a notification in a different manner from when the state information 193 does not include the overtaken vehicle's intention to change lanes.

[0107] In this manner, the driving assistance system 10a can detect the state information 193 including the intention of the overtaken vehicle to change lanes and control the notification using the state information 193, thereby enabling the notification control to more appropriately reflect the relationship with other vehicles.

[0108] Each functional component of the driving assistance system 10 and 10a described above may be realized by hardware that realizes each functional component (e.g., a hardwired electronic circuit, etc.), or may be realized by a combination of hardware and software (e.g., a combination of an electronic circuit and a program that controls it, etc.). For example, any process in the present disclosure may be realized by having a CPU execute a computer program.

[0109] The program includes instructions (or software code) that, when loaded into a computer, cause the computer to perform one or more functions described in the embodiments. The program may be stored on various types of non-transitory computer readable medium or tangible storage medium. By way of example and not limitation, non-transitory computer readable medium or tangible storage medium includes random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD) or other memory technology, CD-ROM, digital versatile disc (DVD), Blu-ray® disk or other optical disk storage, magnetic cassette, magnetic tape, magnetic disk storage or other magnetic storage device. The program may also be transmitted on various types of transitory computer readable medium or communication medium. By way of example and not limitation, transitory computer readable medium or communication medium includes electrical, optical, acoustic, or other form of propagated signal.

[0110] The present disclosure is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit and scope of the present disclosure. Also, the above-described first and second embodiments can be combined in any manner.

[0111] This disclosure includes matters that contribute to the realization of the SDGs' goal of "Ensure good health and well-being for all" and contribute to reducing traffic accidents. [Explanation of symbols]

[0112] 1, 1a Driving support device 2 Vehicle 3. Notification Department 10, 10a Driving assistance systems 11 Acquisition Department 12, 12a Image processing unit 13, 13a Memory control unit 14 Behavior detection unit 15, 15a Notification control section 19, 19a Storage section 31 Display section 32 Audio output section 191 Information on overtaken vehicles 192 Suspicious Behavior Information 193 Status Information C1 Front Camera C2 Rear Camera

Claims

1. a storage control unit that stores in a storage unit overtaken vehicle information indicating a vehicle that the host vehicle has overtaken or been overtaken by; a behavior detection unit that detects the behavior of a rear vehicle traveling behind the host vehicle; a notification control unit that notifies an occupant of the host vehicle when the behavior of the rear vehicle is determined to be suspicious; Equipped with The notification control unit performs the notification in a different manner from a case where the vehicle indicated by the overtaken vehicle information and the rear vehicle whose suspicious behavior is determined match each other. Driving assistance device.

2. The notification control unit controls a notification mode based on an elapsed time since the host vehicle overtakes or is overtaken by the overtaken vehicle. The driving assistance device according to claim 1 .

3. The notification control unit is determining whether or not a vehicle-to-vehicle distance between the host vehicle and the rear vehicle is less than a distance threshold, and performing the notification when it is determined that the vehicle-to-vehicle distance is less than the distance threshold; When the vehicle indicated by the overtaken vehicle information and the rear vehicle whose suspicious behavior is determined match, a larger distance threshold is set than when they do not match. A driving assistance device according to claim 1 or 2.

4. The storage control unit further stores suspicious behavior information regarding the determined suspicious behavior in the storage unit in association with the overtaken vehicle information. A driving assistance device according to claim 1 or 2.

5. The computer a storage control step of storing, in a storage unit, overtaken vehicle information indicating a overtaken vehicle that the host vehicle has overtaken or been overtaken by; a behavior detection step of detecting a behavior of a rear vehicle traveling behind the host vehicle; a notification control step of notifying an occupant of the host vehicle when the behavior of the rear vehicle is determined to be suspicious; Run In the notification control step, when the vehicle indicated by the overtaken vehicle information matches the rear vehicle whose suspicious behavior has been determined, the notification is performed in a different notification mode from when they do not match. Driving assistance methods.

Images