DRIVING ASSISTANCE DEVICE AND DRIVING ASSISTANCE SYSTEM

Abstract

Driving assistance system (100) comprising: a support unit (51) designed to perform lane keeping assistance as a driving assistance for a vehicle; a retrieval unit (52) designed to obtain position information about a lane increase / decrease area in a road extension direction on a road on which the vehicle is traveling, and lane information about the lane increase / decrease area in a road width direction on the road on which the vehicle is traveling, based on a position of the vehicle and map information, wherein the lane increase / decrease area is an area in which the number of lanes increases or decreases;a notification unit (55) designed to provide a notification to the driver of the vehicle regarding the presence of the lane increase / decrease area, based on the vehicle's position in the direction of travel and the position information about the lane increase / decrease area, when the distance between the vehicle and the lane increase / decrease area located ahead of the vehicle in the direction of travel is equal to or less than a threshold value; a lane detection unit (53) designed to detect an occupied lane in which the vehicle is traveling on the road;and a determination unit (54) designed to determine, based on the lane information obtained from the acquisition unit and the lane being traveled as detected by the lane detection unit, whether the lane being traveled contains the lane increase / decrease area, characterized in that the notification unit is designed to reduce the intensity level of the notification compared to a case in which the determination unit determines that the lane being traveled contains the lane increase / decrease area, when the determination unit determines that the lane being traveled does not contain the lane increase / decrease area.

Description

BACKGROUND OF THE INVENTION 1. Field of the invention The invention relates to a driving assistance device and a driving assistance system. 2. Description of the state of the art As described, for example, in JP 2004-102536 A, there is a driving assistance device that helps a vehicle stay within its lane. Such a device may stop providing driving assistance or have difficulty providing it if the number of lanes increases or decreases, for example, if there is a point where the number of lanes on a road narrows. The driving assistance device described in JP 2004-102536 A provides a notification regarding the cessation of driving assistance when the vehicle enters an area where driving assistance is stopped. WO 2012 / 047 743 A2 discloses a driving assistance device according to the preamble of independent claims. SUMMARY OF THE INVENTION When the vehicle enters (or approaches) an area where the driving assistance stops, the driving assistance device, as described in JP 2004-102536 A, provides a uniform notification of the driving assistance stopping. That is, the same notification is provided regardless of whether a lane increase / decrease zone, created due to an increase or decrease in the number of lanes, is present in a lane the vehicle is traveling in or in a lane other than the one the vehicle is traveling in. As a result, the driver of the vehicle cannot determine whether the lane increase / decrease zone is present in the lane the vehicle is traveling in.In this respect, there is a need in this technical field for a driving assistance device that is capable of providing suitable notification regarding a lane increase / decrease area based on a lane on which the lane increase / decrease area is present. A first aspect of the invention relates to a driving assistance system comprising: a support unit designed to perform lane keeping assistance as driving assistance for a vehicle; a retrieval unit designed to obtain position information about a lane increase / decrease area in a road extension direction on a road on which the vehicle is traveling, and lane information about the lane increase / decrease area in a road width direction on the road on which the vehicle is traveling, based on a position of the vehicle and map information, wherein the lane increase / decrease area is an area in which the number of lanes increases or decreases;a notification unit designed to provide a notification to the driver of the vehicle regarding the presence of the lane increase / decrease area, based on the vehicle's position in the direction of travel and position information about the lane increase / decrease area, when the distance between the vehicle and the lane increase / decrease area, which is located ahead of the vehicle in the direction of travel, is equal to or less than a threshold value; a lane detection unit designed to detect an occupied lane in which the vehicle is traveling on the road;and a determination unit designed to determine, based on the lane information obtained from the acquisition unit and the lane being traveled as detected by the lane detection unit, whether the lane being traveled contains the lane increase / decrease area, wherein the notification unit is designed to reduce the intensity level of the notification when the determination unit determines that the lane being traveled does not contain the lane increase / decrease area, compared to when the determination unit determines that the lane being traveled does contain the lane increase / decrease area. Based on the above, the driver can determine whether the lane being driven on contains a lane increase / decrease zone by observing changes in the intensity level of the notification provided by the notification unit. In other words, the driver can recognize that lane keeping assist will be deactivated or that providing lane keeping assist will be difficult because the lane being driven on contains a lane increase / decrease zone.Furthermore, it is possible to prevent a high-intensity alert from being issued despite the fact that the lane increase / decrease zone is located in a different lane than the one the vehicle is traveling in, and the presence of the lane increase / decrease zone does not directly affect the vehicle's current journey. In this way, the driving assistance device can provide an appropriate alert based on the lane where the lane increase / decrease zone is located. According to the above aspect, the determination unit can be designed to determine, based on the lane information obtained from the acquisition unit and the lane being traveled, which is detected by the lane detection unit, whether the lane being traveled, which is determined to not contain the lane increase / decrease area, connects to a lane that does contain the lane increase / decrease area, if it is determined that the lane being traveled does not contain the lane increase / decrease area;and the notification unit may be designed to lower the intensity level of the notification when the determining unit determines that the lane being traveled, which is determined not to contain the lane increase / decrease zone, connects to the lane that does contain the lane increase / decrease zone, compared to a case where the determining unit determines that the lane being traveled, which is determined not to contain the lane increase / decrease zone, connects to the lane that does contain the lane increase / decrease zone. According to the above aspect, even if the lane being traveled does not contain the lane increase / decrease zone, the driver of the vehicle can still determine whether the lane being traveled connects to the lane that does contain the lane increase / decrease zone. A second aspect of the invention relates to a driving assistance device comprising: a storage unit mounted in a vehicle, wherein the storage unit is configured to store a lane increase / decrease area position, which is a position where a lane increase / decrease area is present, and a lane containing the lane increase / decrease area, which is a lane where the lane increase / decrease area is present, wherein the lane increase / decrease area is an area where the number of lanes increases or decreases; a human-machine interface mounted in the vehicle, wherein the human-machine interface is configured to output information;and an electronic control unit containing a processor, wherein the electronic control unit is configured to obtain a current vehicle position, which is a position where the vehicle is present; to calculate a positional relationship between the lane increase / decrease area and the vehicle based on the lane increase / decrease area position and the current vehicle position; to cause the human-machine interface to output information about the lane increase / decrease area when it is determined that the positional relationship satisfies a predetermined condition; to obtain information about a lane in which the vehicle is traveling; and to cause the human-machine interface to change a manner of outputting the information based on whether the lane containing the lane increase / decrease area and the lane in which the vehicle is traveling are the same. In the above aspect, the electronic control unit may be designed to output the information with greater emphasis when the lane containing the lane increase / decrease area and the lane being traveled are the same, compared to a case where the lane containing the lane increase / decrease area and the lane being traveled are different. In the above aspect, the electronic control unit may be designed to output the information with greater emphasis when the lane containing the lane increase / decrease area and the lane in use are different from each other and the lane in use connects to the lane containing the lane increase / decrease area, compared to a case where the lane containing the lane increase / decrease area and the lane in use are different from each other and the lane in use does not connect to the lane containing the lane increase / decrease area. In the above aspect, the electronic control unit may be designed to change the saturation or brightness of the displayed information over the lane increase / decrease range. In the above aspect, the electronic control unit may be designed to change the volume of a tone to provide a notification regarding information about the lane increase / decrease area. In the above aspect, the electronic control unit may be designed to calculate a distance between the lane increase / decrease area and the vehicle; and to determine that the predetermined condition is met when the distance is equal to or less than a threshold value. In the above aspect, the electronic control unit may be designed to set a target range based on the lane rise / fall range position; and the electronic control unit may be designed to determine that the predetermined condition is met when the current vehicle position is within the target range. In the above aspect, the electronic control unit may be designed to provide lane keeping assistance to support the vehicle's movement in such a way that the vehicle travels along the lane being traveled, and the control accuracy of the lane keeping assistance may be lower when the distance is equal to or less than the threshold, compared to a case where the distance is greater than the threshold. BRIEF DESCRIPTION OF THE DRAWINGS Features, advantages, and the technical and industrial significance of exemplary embodiments of the invention are described below with reference to the accompanying drawings, in which the same reference numerals denote the same elements. The drawings show: Fig. 1 a block diagram illustrating the configuration of a driving assistance device according to one embodiment; Fig. 2A a planar view illustrating a case in which, on a road where the number of lanes decreases, a lane increase / decrease zone is present in one lane in which a vehicle is traveling; Fig. 2B a view illustrating an example of an image displayed on a display unit in the case shown in Fig. 2A; Fig.Figure 3A is a planar view showing a case where, on a road with a decreasing number of lanes, there is a lane increase / decrease zone on a lane adjacent to a lane in which the vehicle is traveling; Figure 3B is a view showing an example of an image displayed on the display unit in the case shown in Figure 3A; Figure 4A is a planar view showing a case where, on a road with a decreasing number of lanes, there is a lane increase / decrease zone on a second lane ahead of a lane in which the vehicle is traveling (that is, there is a lane between the lane in which the lane increase / decrease zone is present and the lane in which the vehicle is traveling); Figure 4B is a view showing an example of an image displayed on the display unit in the case shown in Figure 3A.4A is shown; Fig. 5A is a planar view showing a case where, on a road where the number of lanes increases, there is a lane increase / decrease area on one of the lanes in which the vehicle is traveling; Fig. 5B is a planar view showing a case where, on a road where the number of lanes increases, there is a lane increase / decrease area on one of the lanes in which the vehicle is traveling; Fig. 5C is a view showing a case of an image displayed on the display unit in the cases shown in Figs. 5A and 5B; Fig. 6A is a planar view showing a case where, on a road where the number of lanes increases, there is a lane increase / decrease area on one of the lanes adjacent to a lane in which the vehicle is traveling; Fig.6B is a planar view showing a case where, on a road with an increasing number of lanes, there is a lane increase / decrease zone on a lane adjacent to the lane in which the vehicle is traveling; Fig. 6C is a view showing an example of an image displayed on the display unit in the cases shown in Fig. 6A and Fig. 6B; Fig. 7A is a planar view showing a case where, on a road with a branching lane, there is a lane increase / decrease zone on a lane in which the vehicle is traveling; Fig. 7B is a view showing an example of an image displayed on the display unit in the case shown in Fig. 7A; Fig.Figure 8A is a planar view depicting a case where, on a road where a lane branches off, a lane increase / decrease zone exists in a lane adjacent to a lane in which the vehicle is traveling; Figure 8B is a view showing an example of an image displayed on the display unit in the case shown in Figure 8A; and Figure 9 is a flowchart depicting the procedure of a process for providing a notification regarding the presence of a lane increase / decrease zone. DETAILED DESCRIPTION OF THE EXECUTION FORMS Exemplary embodiments of the invention are described below with reference to the accompanying drawings. Note that the same elements are designated with the same reference numerals in the description of the drawings, and their descriptions are not repeated. A driving assistance device 100, shown in Fig. 1, is mounted in a vehicle M, such as a motor vehicle, to assist a driver in driving the vehicle M. The driving assistance device 100 performs driving assistance, for example lane keeping assistance (LKA), to support the driving of the vehicle M in such a way that the vehicle M drives along a lane. The lane keeping assist system according to the present embodiment is a driving aid for controlling the vehicle M such that the lateral position of the vehicle M is set to a target lateral position on the lane being traveled, and, when the driver performs a steering operation, reflects the steering operation while the vehicle M is traveling. The lane being traveled refers to the lane on which the vehicle M is traveling. The lateral position of the vehicle M refers to its position in the width direction of the lane being traveled. The lateral position of the vehicle M is determined, for example, using the vehicle M's midpoint in a top view as a reference. The target lateral position refers to the target control position of the vehicle M when the lane keeping assist system is active. The target lateral position is set, for example, to the midpoint in the width direction of the lane being traveled.Alternatively, the lateral target position can be set to a position that is offset in the width direction from the center position of the traveled lane. The driving assistance device 100 detects two white lines defining a lane, for example, using a camera mounted in the vehicle M. Based on these two detected white lines, the driving assistance device 100 then defines a position equidistant from the two white lines in the lane width direction as the center position of the lane and sets this position as the lateral target position for the lane keeping assistance. Furthermore, the driving assistance device 100 detects the lateral position of the vehicle M based, for example, on the positions of two white lines in an image captured by the camera.The driving assistance device 100 assists the vehicle M in driving along the lane by exerting a steering torque on the vehicle M such that the lateral position of the vehicle M is adjusted to the desired lateral position. The driving assistance device 100 exerts a steering torque on a steering device of the vehicle M, for example by controlling a steering actuator of the vehicle M. The following describes the configuration of the driving assistance device 100. The driving assistance device 100 includes a camera 1, a receiver unit 2 of a global positioning system (GPS receiver unit), a navigation system 3, a communication unit 4, an electronic driving assistance control unit (ECU) 5, a steering actuator 6 and a human-machine interface (HMI) 7. Camera 1 is an image capture device that records an image of the road in front of vehicle M. Camera 1 is, for example, located on the side of the vehicle cabin in relation to the windshield of vehicle M. Camera 1 transmits the recorded image information to the driver assistance ECU 5. Camera 1 can be a monocular camera or a stereo camera. The GPS receiver 2 receives signals from three or more satellites of a global positioning system (GPS satellites) to measure the position of the vehicle M (for example, the latitude and longitude of the vehicle M). The GPS receiver 2 transmits the information about the measured position of the vehicle M to the driver assistance ECU 5. Note that any device can be used to identify the latitude and longitude of the vehicle M instead of the GPS receiver 2. The navigation system 3 is a device that provides the driver of vehicle M with route guidance to a destination set by the driver of vehicle M. The navigation system 3 includes a map storage unit 31 that stores map information. The navigation system 3 calculates a route along which the vehicle M travels based on information about the position of vehicle M, measured by the GPS receiver unit 2, and the map information stored in the map storage unit 31. For example, the navigation system 3 calculates a destination route from the position of vehicle M to the destination and then communicates the destination route to the driver, for example, by displaying the destination route on a display unit or by announcing the destination route verbally from an audio output unit.When a notification regarding the destination route is provided, the navigation system 3 can use a display unit 71 and an audio output unit 72 of the HMI 7 (described later), or it can use a display unit and an audio output unit located within the navigation system 3. Note that the navigation system 3 can be located in a computer in a facility such as an information processing center that is capable of communicating with the vehicle M. The map information stored in the map storage unit 31 includes, in addition to information about roads or similar features for providing route guidance to a destination, position information about a lane increase / decrease zone and information about a lane on which a lane increase / decrease zone exists. Specifically, a lane increase / decrease zone refers to an area where the number of lanes decreases, increases, or a lane branches off. If a lane decreases, increases, or branches off zone exists on a lane in which the vehicle M is traveling, the driving assistance device 100 may not be able to determine a lane in which the vehicle M should travel after passing the lane increase / decrease zone.As a result, the driving assistance device 100 stops the lane keeping assist in the lane increase / decrease range or has difficulty providing the lane keeping assist. Note that "driving assistance device 100 has difficulty providing the lane keeping assist" means, for example, that the control accuracy of the lane keeping assist is reduced. The positional information for a lane increase / decrease zone contains information (such as latitude and longitude) to identify the location of an area where the number of lanes decreases, increases, or a lane branches off. If a road has multiple lanes, the lane information for a lane increase / decrease zone identifies a lane where the lane increase / decrease zone is present in the road's width direction. First, an example of a lane increase-decrease region is described, which is generated due to a reduction in the number of lanes. "The number of lanes decreases" means that on a road containing multiple lanes, the number of lanes decreases at a given point on the road. In other words, "the number of lanes decreases" means that at least one of the lanes ends at a given point on the road. For example, if vehicle M is traveling in a lane that will end due to a reduction in the number of lanes, the driving assistance device 100 will stop providing lane keeping assistance or will have difficulty providing lane keeping assistance because of the lane ending. Thus, a region containing a point where the lane ends is defined as a lane increase-decrease region. As shown, for example, in Fig.As shown in Figure 2A, there is a road R1 where the number of lanes decreases from three lanes (one lane L1, one lane L2, and one lane L3) to two lanes (one lane L2 and one lane L3). In this case, an area containing a point where lane L1 ends (the endpoint of lane L1) is defined as a lane increase / decrease area P, which is generated due to the reduction in the number of lanes. That is, the lane increase / decrease area P is present on lane L1. The lane information about the lane increase / decrease area P contains information about lane L1 on which the lane increase / decrease area P is located.Note that the lane increase / decrease range P can be set to a range having a predetermined size, such that the lane increase / decrease range P includes the point where lane L1 ends. Fig. 2A depicts a state in which vehicle M is traveling from the left side to the right side of the drawing. That is, the lane increase / decrease zone P is located in front of vehicle M in its direction of travel, and vehicle M is traveling in the direction of the lane increase / decrease zone P. Figs. 3A, 4A, 5A, 5B, 6A, 6B, 7A, and 8A, as well as Fig. 2A, each depict a state in which vehicle M is traveling from the left side towards the right side of the drawing. The following describes an example of a lane increase-decrease area created due to an increase in the number of lanes. "The number of lanes increases" means that the number of lanes increases at a given point on a road. Examples of the case where the number of lanes increases include a case where one lane widens to two lanes at a given point on a road. As shown, for example, on road R2 in Fig. 5A, the number of lanes increases from one lane, that is, lane L1, to two lanes, that is, lane L1a and lane L1b. Examples of the case where the number of lanes increases also include a case where a new lane is provided at a position on the side of a given lane. As shown, for example, on road R3 in Fig.As shown in Figure 5B, a new lane L3 is provided on the left side of a lane L1 at a given point on the road R3. For example, if vehicle M is traveling in a lane where the number of lanes increases at a given point on the road, as shown in the example in Fig. 5A, the driving assistance device 100 has difficulty determining which of the lanes L1a and L1b the vehicle M should travel in from the point where the number of lanes increases. Similarly, as shown in the example in Fig. 5B, the driving assistance device 100 has difficulty determining which of the lanes L1 and the newly provided lane L3 the vehicle M should travel in. Therefore, the driving assistance device 100 stops the lane keeping assistance or has difficulty providing the lane keeping assistance when the number of lanes increases.As described above, an area containing a point where the number of lanes increases is defined as a lane increase / decrease area. As shown, for example, in Fig. 5A, on road R2, where the number of lanes increases—that is, where lane L1 widens into lane L1a and lane L1b—the area containing the point at which lane L1 widens into lane L1a and lane L1b is defined as the lane increase-reduction area P. That is, the lane increase-reduction area P is present on lane L1. The lane information about the lane increase-reduction area P contains information about lane L1, that is, the lane on which the lane increase-reduction area P is present. Note that the lane increase-reduction area P can be an area with a predetermined size, set such that the lane increase-reduction area P contains the point at which the number of lanes increases. As shown, for example, in Fig. 5B, similarly on road R3, where lane L3 is newly provided to the left of lane L1, the area containing a point on lane L1 corresponding to the starting point of lane L3 (the point where lane L3 begins) in the lane width direction is defined as the lane increase / decrease area P. That is, the lane increase / decrease area P is present on lane L1. The lane information about the lane increase / decrease area P contains information about lane L1, that is, the lane on which the lane increase / decrease area P is present.Note that the lane increase / decrease area P can be an area having a predetermined size, set such that the lane increase / decrease area P contains the point on lane L1 that corresponds to the starting point of lane L3 in the lane width direction. The following describes an example of a lane increase-decrease area created by a lane branching off. "A lane branches off" means that a branching lane connects to the side of a given lane. A lane branching off can be considered a kind of increase in the number of lanes, as the branching lane is newly provided. As shown, for example, on road R4 in Fig. 7A, lane L3, which serves as a branching lane, connects to the left side of lane L1. That is, lane L1 branches into lane L1 and lane L3.For example, if the vehicle M is traveling in a lane that will branch, as shown in the example in Fig. 7A, the driving assistance device 100 has difficulty determining which of the lanes L1 and L3 the vehicle M should travel in from the point where lane L1 branches into lane L1 and lane L3. In this respect, the driving assistance device 100 stops the lane keeping assistance or has difficulty providing the lane keeping assistance when the lane branches. As described above, a region containing a point where a lane branches is defined as a lane increase-decrease region. As shown, for example, in Fig.As shown in Figure 7A, on a road R4 where lane L3, serving as the branch lane, connects to the left side of lane L1, the area containing the point on lane L1 corresponding to the starting point of lane L3 (the end segment of lane L3 connected to lane L1) in the lane width direction is defined as the lane increase / decrease area P. That is, the lane increase / decrease area P is present on lane L1. The lane information about the lane increase / decrease area P contains information about lane L1, that is, the lane on which the lane increase / decrease area P is present. Note that the lane increase / decrease area P can be an area with a predetermined size, set such that the lane increase / decrease area P includes the point where the lane branches. The map information stored in map storage unit 31 can also include the number of white lines present on a road and the types of white lines. Furthermore, the map information stored in map storage unit 31 can include the number of lanes present on a road. Communication Unit 4 obtains the map information, which includes position and lane information about a lane increase / decrease area, by communicating with a computer in a facility such as an information processing center outside of vehicle M. Examples of information processing centers include one that collects position and lane information about an area where lane keeping assistance is stopped or where providing lane keeping assistance becomes difficult if vehicle M, or any vehicle other than vehicle M, is actually driving in that area.Thus, the driving assistance device 100 can use the map information stored in a computer in a facility such as an information processing center, in addition to the map information stored in the map storage unit 31 of the navigation system 3. The steering actuator 6 controls the drive of an auxiliary motor, which in turn controls a steering torque (actuator output) in an electric power steering system, based on a command control value provided by the driving assistance ECU 5. In this way, the steering actuator 6 controls the steering torque to be applied to the vehicle M. The HMI 7 is an interface that receives information from an occupant (for example, a driver) of the vehicle M and outputs the information to the driving assistance device 100, or receives information from the driving assistance device 100 and outputs the information to the occupant. The HMI 7 includes, for example, a display unit 71, such as a display that shows visual information to the occupant, an audio output unit 72, such as a speaker that outputs information via speech, and an actuation button, touch surface, or similar device with which the occupant performs an input operation. When an input operation to start or stop the lane keeping assist is performed by the occupant, the HMI 7 outputs a signal to the driving assistance ECU 5 to start or stop the lane keeping assist. The driver assistance ECU 5, for example, controls the movement of vehicle M. The driver assistance ECU 5 is an electronic control unit that includes, for example, a central processing unit (CPU), read-only memory (ROM), and random access memory (RAM). Within the driver assistance ECU 5, programs stored in the ROM are loaded into the RAM, and the CPU executes these programs, thus performing various types of control functions. The driver assistance ECU 5 can be comprised of multiple electronic control units. The driver assistance ECU 5 contains a support unit 51, an acquisition unit 52, a lane detection unit 53, a determination unit 54, and a notification unit 55. The support unit 51 provides lane keeping assistance to support the vehicle M in driving along an occupied lane. Specifically, the support unit 51 initiates the lane keeping assistance in response to, for example, the activation of a switch by the driver. The support unit 51 detects a white line of the lane in which the vehicle M is traveling by means of image analysis based on, for example, an image of a road in front of the vehicle M, captured by camera 1. The support unit 51 detects the lateral position of the vehicle M on the occupied lane based on, for example, the positions of the detected white lines in the image.The support unit 51 then controls the vehicle M by applying a steering torque to the vehicle such that the detected lateral position of vehicle M is adjusted to the desired lateral position. The support unit 51 transmits a control signal to the steering actuator 6 to apply the steering torque to vehicle M. In this case, the desired lateral position can, for example, be set to the center position of the lane in its width direction or to a position offset from the center position of the lane in its width direction. Based on the position of vehicle M and the map information, the acquisition unit 52 obtains position information about the lane rise / fall area in the road's extension direction (for example, the direction indicated by arrow X in Fig. 2A) on the road on which vehicle M is traveling, and lane information about the lane rise / fall area in the road's width direction (for example, the direction indicated by arrow Y in Fig. 2A). The acquisition unit 52 can obtain the position of vehicle M based on the location result provided by the GPS receiver unit 2. The acquisition unit 52 obtains the map information from the map storage unit 31 of the navigation system 3.Alternatively, the acquisition unit 52 can obtain the map information from a computer in a facility such as an information processing center using the communication unit 4. The acquisition unit 52 obtains the position information and lane information about the lane increase / decrease zone present on the road ahead of vehicle M in its direction of travel. The acquisition unit 52 can obtain the position information and lane information about the lane increase / decrease zone present within a predetermined distance of vehicle M's current position ahead of it in its direction of travel. The lane detection unit 53 detects the lane in which vehicle M is traveling on the road on which vehicle M is traveling. That is, the lane detection unit 53 detects the lane in which vehicle M is traveling on a road containing multiple lanes. The lane detection unit 53 detects the lane being traveled using a known method based, for example, on an image of the road in front of vehicle M, which is captured by camera 1. In particular, the lane detection unit 53 detects, for example, the white lines of the road in front of vehicle M by means of image analysis based, for example, on an image of the road in front of vehicle M, which is captured by camera 1. The lane detection unit 53 can detect the lane in which vehicle M is traveling based, for example, on the number of white lines detected on the road and the positional relationship between the white lines and vehicle M.In some cases, information about the number of white lines present on a road, the types of white lines, and the number of lanes is included in the map information stored in the map storage unit 31 of the navigation system 3. In such a case, the lane detection unit 53 can detect the lane in which the vehicle M is traveling, based on the information about the number of white lines, the types of white lines, and the number of lanes, in addition to the image captured by camera 1. The determination unit 54 determines whether the lane in which the vehicle M is traveling contains a lane increase / decrease zone, based on the lane information obtained by the acquisition unit 52 and the lane being traveled, which is detected by the lane detection unit 53. Specifically, the determination unit 54 determines whether the lane in which the vehicle is traveling is a destination lane containing a lane increase / decrease zone, or whether the lane being traveled is a non-destination lane not containing a lane increase / decrease zone, based on the lane information about a lane increase / decrease zone obtained by the acquisition unit 52 and the lane being traveled, which is detected by the lane detection unit 53.For the lane in front of vehicle M, within a predetermined distance of vehicle M's current position, the determination unit 54 can determine whether the lane contains a lane increase / decrease zone. If the lane in which vehicle M is traveling contains a lane increase / decrease zone, that is, if a lane increase / decrease zone is present on the lane in which it is traveling, the determination unit 54 determines that the lane in which vehicle M is traveling is a destination lane. If the lane in which vehicle M is traveling does not contain a lane increase / decrease zone, that is, if no lane increase / decrease zone is present on the lane in which it is traveling, the determination unit 54 determines that the lane in which vehicle M is traveling is a non-destination lane. In the example shown in Fig. 2A, the lane increase / decrease zone P is present on lane L1, that is, the lane in which vehicle M is traveling. Thus, the determination unit 54 determines that the lane in which vehicle M is traveling (lane L1) is a destination lane. In the example shown in Fig. 3A, the lane increase / decrease zone P is not present on lane L2, that is, the lane in which vehicle M is traveling. Thus, the determination unit 54 determines that the lane in which the vehicle is traveling (lane L2) is a non-destination lane. In the example shown in Fig. 4A, the lane increase / decrease zone P is not present on lane L3, that is, the lane in which vehicle M is traveling. Thus, the determination unit 54 determines that the lane on which vehicle M is driving (lane L3) is a non-destination lane. In the examples shown in Figs. 5A, 5B, and 7A, the lane increase / decrease zone P is present on lane L1, that is, the lane in which vehicle M is traveling. Thus, the determination unit 54 determines that the lane in which vehicle M is traveling (lane L1) is a destination lane. In the examples shown in Figs. 6A, 6B, and 8A, the lane increase / decrease zone P is not present on lane L2, that is, the lane in which vehicle M is traveling. Thus, the determination unit 54 determines that the lane in which vehicle M is traveling (lane L2) is a non-destination lane. If the determination unit 54 determines that the lane being traveled on is a non-destination lane, the determination unit 54 determines whether the lane being traveled on, which has been determined to be a non-destination lane, connects to the lane containing the lane increase / decrease zone P. In the examples shown in Fig. 3A and Fig. 4A, the lane increase / decrease zone P is present, for example, on lane L1. Thus, if vehicle M is traveling on lane L3, as shown in Fig. 3A, the determination unit 54 determines that the lane being traveled on, in which vehicle M is traveling, connects to the lane containing the lane increase / decrease zone P (lane L1). If vehicle M is traveling on lane L3, as shown in Fig.As shown in 4A, the determination unit 54 determines that the lane being driven on, on which the vehicle M is driving, does not connect to the lane which contains the lane increase / decrease area P (lane L1). In the examples shown in Fig. 6A, Fig. 6B and Fig. 8A, the lane increase / decrease zone P is present, for example, on lane L1. Thus, when vehicle M travels on lane L2, as shown in Fig. 6A, Fig. 6B and Fig. 8A, the determining unit 54 determines that the lane on which vehicle M travels connects to the lane containing the lane increase / decrease zone P (lane L1). The notification unit 55 determines, based on the position of vehicle M in the direction of travel and the position information about the lane increase / decrease zone, whether the distance between vehicle M and the lane increase / decrease zone located in front of vehicle M is equal to or less than a threshold value. The distance between vehicle M and the lane increase / decrease zone is the distance between vehicle M and the lane increase / decrease zone along the direction of travel. This distance can be the distance from vehicle M to the point where it enters the lane increase / decrease zone.Alternatively, the distance between vehicle M and the lane increase / decrease area can be the distance from vehicle M to the end of the lane, the distance from vehicle M to the point where the number of lanes increases, or the distance from vehicle M to the point where the lane forks. The notification unit 55 can calculate the distance between vehicle M and the lane increase / decrease area along the road based, for example, on map data stored in the map storage unit 31. The notification unit 55 can obtain the position of vehicle M based on the location result provided by the GPS receiver unit. If the distance between vehicle M and the lane increase / decrease zone is equal to or less than the threshold, the notification unit 55 notifies the driver of vehicle M of the presence of the lane increase / decrease zone on the road. The notification unit 55 provides a notification of the presence of the lane increase / decrease zone using at least one of the display unit 71 and the sound output unit 72. When providing a notification, the notification unit 55 reduces the intensity level of the notification when the determination unit 54 determines that the lane being traveled does not contain the lane increase / decrease zone, compared to a case where the determination unit 54 determines that the lane being traveled does contain the lane increase / decrease zone.In particular, when providing a notification, the notification unit 55 reduces the intensity level of the notification when the determination unit 54 determines that the lane being traveled is a non-destination lane, compared to a case where the determination unit 54 determines that the lane being traveled is a destination lane. Note that a notification with a high intensity level may be designed in such a way that a driver can more easily notice its delivery than a notification with a low intensity level. Alternatively, a notification with a high intensity level may be designed in such a way that a driver can more easily recognize its content than the content of a notification with a low intensity level. The notification unit 55 reduces the intensity level of a notification when the lane being traveled, which is determined by the determination unit 54 to be a lane that does not contain the lane increase / decrease area, does not connect to the lane that does contain the lane increase / decrease area, compared to a case in which the determination unit 54 determines that the lane being traveled, which does not contain the lane increase / decrease area, is a lane that connects to the lane that does contain the lane increase / decrease area.In particular, the notification unit 55 can vary the intensity level of a notification provided when it is determined that the lane being traveled is a non-destination lane, depending on whether the lane being traveled, in which the vehicle M is traveling, connects to the lane containing the lane increase / decrease zone P. More precisely, the notification unit 55 can reduce the intensity level of a notification when the determination unit 54 determines that the lane being traveled, which is a non-destination lane, does not connect to the lane containing the lane increase / decrease zone P, compared to a case in which the determination unit 54 determines that the lane being traveled, which is a non-destination lane, does connect to the lane containing the lane increase / decrease zone P. In other words, if the lane in which vehicle M is traveling is the destination lane (lane L1), as shown in Fig. 2A, the notification unit 55 provides a notification with a high intensity level. If, as shown in Fig. 3A, the lane in which vehicle M is traveling is a non-destination lane and adjoins the lane containing the lane increase / decrease zone P (lane L1), the notification unit 55 provides a notification with a medium intensity level. As shown in Fig. 4A, the notification unit 55 provides a notification with a low intensity level if the lane in which vehicle M is traveling is a non-destination lane and does not adjoin the lane containing the lane increase / decrease zone P (lane L1).Note that a notification with a high intensity level has a higher intensity than a notification with a medium intensity level. A notification with a medium intensity level has a higher intensity than a notification with a low intensity level. Thus, the driver of vehicle M can determine, based on the intensity level of a notification, whether the lane being traveled in is a destination lane. Even if the lane being traveled in is a non-destination lane, the driver of vehicle M can determine, based on the intensity level of a notification, whether the lane being traveled connects to the lane containing the lane increase / decrease zone P. In particular, when a notification is provided using display unit 71, notification unit 55 increases the saturation of a pictogram displayed on display unit 71 when, for example, a notification with a high intensity level is provided, compared to a notification with a medium or low intensity level. Notification unit 55 increases the saturation of a pictogram displayed on display unit 71, for example, when a notification with a medium intensity level is provided, compared to a notification with a low intensity level.The pictogram refers to a marking to notify the driver that a lane increase / decrease area is present on the road and that the distance between the vehicle M and the lane increase / decrease area is equal to or less than a threshold value. The driver can determine whether the lane being traveled on is a destination lane or a non-destination lane based on the saturation of the pictogram displayed on display unit 71. Even if the lane in which vehicle M is traveling is a non-destination lane, the driver can determine, based on the saturation of the pictogram displayed on display unit 71, whether the lane being traveled connects to the lane containing the lane increase / decrease zone P. The higher the intensity level of a notification, the higher the saturation of the pictogram displayed on display unit 71. A higher notification intensity level makes the pictogram even easier for the driver to recognize, meaning the driver can more easily identify the notification. When a notification is provided using the sound output unit 72, the notification unit 55 increases the volume of the sound output from the sound output unit 72, for example, when a notification with a high intensity level is provided, compared to a case where a notification with a medium or low intensity level is provided. The notification unit 55 increases the volume of the sound output from the sound output unit 72, for example, when a notification with a medium intensity level is provided, compared to a case where a notification with a low intensity level is provided.The tone output from tone output unit 72 is a sound used to notify the driver that a lane increase / decrease zone is present on the road and that the distance between the vehicle M and the lane increase / decrease zone is equal to or less than a threshold value. The tone output from tone output unit 72 can be speech, a beeping sound, or a combination of speech and a beeping sound. The driver can determine whether the lane being traveled in is a destination lane or a non-destination lane based on the volume of an audio output from audio output unit 72. Even if the lane in which the vehicle M is traveling is a non-destination lane, the driver can determine, based on the volume of an audio output from audio output unit 72, whether the lane being traveled connects to the lane containing the lane increase / decrease zone P. The higher the intensity level of a notification, the greater the volume of the audio output from audio output unit 72. With a higher notification intensity level, the driver can more easily recognize the audio, meaning the driver can more readily identify the notification being provided. The following describes a specific example of a display screen in a case where a notification is provided using the display unit 71. First, a notification provided when the lane in which vehicle M is traveling is the destination lane (lane L1) is described with reference to Fig. 2A. In this case, the notification unit 55, as shown in Fig. 2B, displays a highly saturated pictogram A as a high-intensity notification on the display unit 71. Pictogram A is an example of a pictogram indicating that the number of lanes will decrease. Note that in Fig. 2B, a front end section of vehicle M and the white lines on both sides of vehicle M are shown in addition to pictogram A. The same applies to the other examples of images displayed on the display unit 71. A notification provided when the lane in which vehicle M is traveling is a non-destination lane and the lane connected to the lane containing the lane increase / decrease zone P (lane L1), as shown in Fig. 3A, is described. In this case, the notification unit 55, as shown in Fig. 3B, displays a pictogram A with lower saturation than pictogram A shown in Fig. 2B, indicating a notification with a medium intensity level on the display unit 71. A notification provided when the lane in which vehicle M is traveling is a non-destination lane and the lane does not connected to the lane containing the lane increase / decrease zone P (lane L1), as shown in Fig. 4A, is also described. In this case, the notification unit 55 shows, as shown in Fig.4B shows a pictogram A with lower saturation than the pictogram A shown in Fig. 3B, indicating a notification with a low intensity level on the display unit 71. A notification provided when the lane in which vehicle M is traveling is the destination lane (lane L1), as shown in Figures 5A and 5B, is described. In this case, the notification unit 55, as shown in Figure 5C, displays a highly saturated pictogram B on the display unit 71 as a high-intensity notification. Pictogram B is an example of a pictogram indicating that the number of lanes will increase. A notification provided when the lane in which vehicle M is traveling is a non-destination lane and the lane connected to the lane containing the lane increase / decrease area P, as shown in Figures 6A and 6B, is described. In this case, the notification unit 55, as shown in Figure 5C, displays a highly saturated pictogram B on the display unit 71. Pictogram B is an example of a pictogram indicating that the number of lanes will increase.Figure 6C shows a pictogram B with lower saturation than pictogram B shown in Figure 5C, indicating a notification with a medium intensity level on the display unit 71. The case in which the lane being traveled on, in which vehicle M is traveling, is a destination lane (lane L1), as shown in Fig. 7A, is described. In this case, the notification unit 55, as shown in Fig. 7B, displays a highly saturated pictogram C as a notification with a high intensity level on the display unit 71. Pictogram C is an example of a pictogram indicating that a lane is about to branch. A notification that is provided when the lane being traveled on, in which vehicle M is traveling, is a non-destination lane and the lane being traveled connects to the lane containing the lane increase / decrease area P, as shown in Fig. 8A, is described. In this case, the notification unit 55, as shown in Fig. 8B, displays a pictogram C with lower saturation than the pictogram C shown in Fig.7B is shown as a notification with a medium intensity level on display unit 71. Notification unit 55 provides the notification described above when the distance between vehicle M and the lane increase / decrease zone P is equal to or less than the threshold. Notification unit 55 stops providing the notification when vehicle M has passed the lane increase / decrease zone P on the road. Whether vehicle M has passed the lane increase / decrease zone P can be determined, for example, based on the position of vehicle M, the position information about the lane increase / decrease zone P, and the map data stored in the map storage unit 31. The following describes the procedure of a process for providing a notification regarding the presence of a lane increase / decrease zone. The process in the flowchart shown in Fig. 9 is executed by the driving assistance ECU 5 when lane keeping assistance for vehicle M is initiated by the assistance unit 51. When the process in the flowchart reaches its end, the driving assistance ECU 5 repeats the process from the start. Alternatively, the driving assistance ECU 5 can repeatedly execute the process from the start at predetermined time intervals. In the case where the process is repeatedly executed at predetermined time intervals, when the process is restarted from the start (even if the process is already running), the driving assistance ECU 5 terminates the previous process, even if the previous process did not reach its end.When lane keeping assistance for vehicle M ends, the driving assistance ECU terminates the process in the flowchart, even if the process is still in progress. Similarly, when vehicle M passes through the lane increase / decrease zone P on a road, notification unit 55 terminates the process in the flowchart, even if the process is still in progress. As shown in Fig. 9, when lane keeping assistance is initiated by the assistance unit 51, the acquisition unit 52 obtains position information about the lane increase / decrease zone on the road where vehicle M is traveling, based on the position of vehicle M and the map information (S101). The notification unit 55 determines whether the distance between vehicle M and the lane increase / decrease zone is equal to or less than the threshold (S102). If the distance between vehicle M and the lane increase / decrease zone is greater than the threshold (S102: No), the driving assistance ECU 5 terminates the current process and restarts the process from the beginning.Note that if the position information about the lane increase / decrease area in S101 is not obtained, the distance between vehicle M and the lane increase / decrease area cannot be calculated, and therefore the notification unit 55 performs a negative determination in the process in S102. The driving assistance ECU 5 can then terminate the current process and restart it from the beginning. If the distance between vehicle M and the lane increase / decrease area is equal to or less than the threshold (S102: Yes), the lane detection unit 53 detects the lane in which vehicle M is traveling on the road (S103). The determination unit 54 determines whether the lane in which vehicle M is traveling is a target lane containing the lane increase / decrease zone P, or whether it is a non-target lane not containing the lane increase / decrease zone P (S104). If the lane in which vehicle M is traveling is the target lane (S105: Yes), the notification unit 55 provides a high-intensity notification (S106). After providing the high-intensity notification, the driving assistance ECU 5 terminates the current process and restarts the process from the beginning. If the lane in which vehicle M is traveling is a non-destination lane instead of the destination lane (S105: No), the determination unit 54 determines whether the lane in which vehicle M is traveling, which has been determined to be a non-destination lane, connects to the lane containing the lane increase / decrease zone P (S107). If the lane in which vehicle M is traveling, which has been determined to be a non-destination lane, connects to the lane containing the lane increase / decrease zone P (S107: Yes), the notification unit 55 provides a notification with a medium intensity level (S108). After providing the notification with a medium intensity level, the driving assistance ECU 5 terminates the current process and restarts the process from the beginning. If the lane in which vehicle M is traveling, which has been designated as a non-destination lane, does not connect to the lane containing the lane increase / decrease zone P (S107: No), the notification unit 55 provides a low-intensity notification (S109). After providing the low-intensity notification, the driving assistance ECU 5 terminates the current process and restarts the process from the beginning. The present embodiment is implemented as described above. When the determination unit 54 determines that the lane being traveled is a non-destination lane, the notification unit 55 of the driving assistance device 100 makes the intensity level of a notification lower than when the determination unit 54 determines that the lane being traveled is a destination lane. Thus, the driver of vehicle M can determine, based on the change in the intensity level of a notification provided by the notification unit 55, whether the lane being traveled contains the lane increase / decrease zone P.This means that, based on the change in the intensity level of a notification provided by notification unit 55, the driver of vehicle M can determine whether lane keeping assistance will be stopped or whether providing lane keeping assistance will become difficult because the lane being traveled contains the lane increase / decrease zone. Furthermore, it is possible to prevent the provision of a notification with a high intensity level despite the fact that the lane increase / decrease zone P is present in a different lane than the lane in which vehicle M is traveling, and the presence of the lane increase / decrease zone P does not directly affect the current journey of vehicle M.In this way, the driving assistance device 100 can provide a suitable notification based on the lane on which the lane increase / decrease area P is present. If the lane being traveled, which has been designated as a non-destination lane by the determination unit 54, does not connect to the lane containing the lane increase / decrease zone P, the notification unit 55 makes the intensity level of a notification lower than it would be if the lane being traveled, which has been designated as a non-destination lane by the determination unit 54, did connect to the lane containing the lane increase / decrease zone P. That is, if the lane being traveled in which vehicle M is traveling is a non-destination lane and connects to the lane containing the lane increase / decrease zone P, the notification unit 55 provides a notification with a medium intensity level.If the lane in which vehicle M is traveling is a non-destination lane and does not connect to the lane containing the lane increase / decrease zone P, the notification unit 55 provides a notification with a low intensity level. In this case, even if the lane in which vehicle M is traveling is a non-destination lane, the driver of vehicle M can determine, based on the intensity level of the notification, whether the lane in question connects to the lane containing the lane increase / decrease zone P. The embodiment of the invention has been described above; however, the embodiments of the invention are not limited to the embodiment described above. For example, the notification unit 55 provides a notification when the distance between the vehicle M and the lane increase / decrease zone is equal to or less than the threshold; however, the notification can also be provided when the vehicle M enters a target zone. In particular, the notification unit 55 sets the target zone to a position between the lane increase / decrease zone and a point separated from the lane increase / decrease zone by a predetermined distance in one direction towards the vehicle M, based on the position information about the lane increase / decrease zone in front of the vehicle M, which is obtained by the acquisition unit 52.The notification unit 55 can set the destination area along the road on which the vehicle M is traveling. When the destination area is set along the road, the notification unit 55 can set the destination area based, for example, on the map data stored in the map storage unit 31. Based on the position of the vehicle M on the road and the set destination area, the notification unit 55 provides a notification when the vehicle M enters the destination area. As in the embodiment described above, when providing a notification, the notification unit 55 changes the intensity level of the notification based on whether the lane on which the vehicle M is traveling is a destination lane or a non-destination lane.As in the embodiment described above, when providing a notification, the notification unit 55 can change the intensity level of the notification based on whether the lane in which the vehicle M is traveling connects to the lane containing the lane increase / decrease zone, if the lane in which the vehicle M is traveling is a non-destination lane. The notification unit 55 stops providing the notification when the position of the vehicle M leaves the destination zone.Note that providing a notification when vehicle M enters the destination area is equivalent to providing a notification when the distance between vehicle M and the lane increase / decrease area P is equal to or less than the threshold as in the embodiment described above, except that the determination of whether vehicle M enters the destination area is used, or the distance between vehicle M and the lane increase / decrease area is used for the determination. Note that if the lane in which vehicle M is traveling is a non-destination lane, it is not necessary for the determination unit 54 to determine whether the lane in which vehicle M is traveling adjoins the lane containing the lane increase / decrease zone P. Furthermore, if the lane in which vehicle M is traveling is a non-destination lane, it is not necessary to change the intensity level of a notification depending on whether the lane in which vehicle M is traveling adjoins the lane containing the lane increase / decrease zone. When a notification is provided using the display unit 71, the notification unit 55 changes the saturation of a pictogram to change the intensity level of the notification; however, something other than the saturation, such as the brightness, can be changed to change the intensity level of the notification.

Claims

Driving assistance system (100) comprising: a support unit (51) designed to perform lane keeping assistance as a driving assistance for a vehicle; a retrieval unit (52) designed to obtain position information about a lane increase / decrease area in a road extension direction on a road on which the vehicle is traveling, and lane information about the lane increase / decrease area in a road width direction on the road on which the vehicle is traveling, based on a position of the vehicle and map information, wherein the lane increase / decrease area is an area in which the number of lanes increases or decreases;a notification unit (55) designed to provide a notification to the driver of the vehicle regarding the presence of the lane increase / decrease area, based on the vehicle's position in the direction of travel and the position information about the lane increase / decrease area, when the distance between the vehicle and the lane increase / decrease area located ahead of the vehicle in the direction of travel is equal to or less than a threshold value; a lane detection unit (53) designed to detect an occupied lane in which the vehicle is traveling on the road;and a determination unit (54) designed to determine, on the basis of the lane information obtained from the acquisition unit and the lane being traveled as detected by the lane detection unit, whether the lane being traveled contains the lane increase / decrease area, characterized in that the notification unit is designed to reduce the intensity level of the notification compared to a case in which the determination unit determines that the lane being traveled contains the lane increase / decrease area, when the determination unit determines that the lane being traveled does not contain the lane increase / decrease area. Driving assistance system according to claim 1, wherein the determination unit is designed to determine, on the basis of the lane information obtained from the acquisition unit and the lane identified as being driven on by the lane recognition unit, whether the driven lane, which has been determined to not contain the lane increase / decrease area, is directly adjacent to a lane which contains the lane increase / decrease area, if it is determined that the driven lane does not contain the lane increase / decrease area;and the notification unit is designed to make the intensity level of the notification lower compared to a case in which the determining unit determines that the lane in use that does not contain the lane increase / decrease area is directly adjacent to the lane that does contain the lane increase / decrease area, when the determining unit determines that the lane in use that does not contain the lane increase / decrease area is not directly adjacent to the lane that does contain the lane increase / decrease area.; Driving assistance device (100) comprising: a memory unit (31) mounted in a vehicle, wherein the memory unit is configured to store a lane increase / decrease area position, which is a position where a lane increase / decrease area is present, and a lane containing the lane increase / decrease area, and which is a lane on which the lane increase / decrease area is present, wherein the lane increase / decrease area is an area in which the number of lanes increases or decreases; a human-machine interface (7) mounted in the vehicle, wherein the human-machine interface is configured to output information; and an electronic control unit (5) comprising a processor, wherein the electronic control unit is configured to obtain a current vehicle position, which is a position where the vehicle is present;to calculate a positional relationship between the lane increase / decrease area and the vehicle based on the lane increase / decrease area position and the current vehicle position; to cause the human-machine interface to output information about the lane increase / decrease area when it is determined that the positional relationship satisfies a predetermined condition; to obtain information about a lane in which the vehicle is traveling; and characterized in that the electronic control unit is further designed to cause the human-machine interface to change the mode of output of the information based on whether the lane containing the lane increase / decrease area is the lane in use. Driving assistance device according to claim 3, wherein the electronic control unit is designed to output the information with greater emphasis when the lane containing the lane increase / decrease area and the lane being driven on are the same, compared to a case in which the lane containing the lane increase / decrease area and the lane being driven on are different. Driving assistance device according to claim 4, wherein the electronic control unit is designed to output the information with greater emphasis compared to a case in which the lane containing the lane increase / decrease area and the lane being driven on are different from each other and the lane being driven on is not directly adjacent to the lane containing the lane increase / decrease area, when the lane containing the lane increase / decrease area and the lane being driven on are different from each other and the lane being driven on is directly adjacent to the lane containing the lane increase / decrease area. Driving assistance device according to claim 3, wherein the electronic control unit is designed to change a saturation or a brightness of the displayed information over the lane increase / decrease range. Driving assistance device according to claim 3, wherein the electronic control unit is designed to change the volume of a tone to provide a notification regarding information about the lane increase / decrease area. Driving assistance device according to claim 3, wherein the electronic control unit is designed to calculate a distance between the lane elevation / reduction area and the vehicle; and to determine that the predetermined condition is met when the distance is equal to or less than a threshold value. Driving assistance device according to claim 3, wherein the electronic control unit is designed to set a target range based on the lane rise / fall range position; and the electronic control unit is designed to determine that the predetermined condition is met when the current vehicle position is within the target range. Driving assistance device according to claim 8, wherein the electronic control unit is designed to provide lane keeping assistance to support the vehicle's movement in such a way that the vehicle travels along the lane being driven on; and the control accuracy of the lane keeping assistance is lower when the distance is equal to or less than the threshold, compared to a case where the distance is greater than the threshold.

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