Driving support device

Abstract

To provide a driving support device capable of displaying a road image around a vehicle with a reduction scale corresponding a present vehicle situation.SOLUTION: A driving support device is configured so as to display a plurality of equidistant circles obtained by connecting points overlapped on a road image and having equal distance from a vehicle together with the road image showing a road shape around a present position of the vehicle by changing the distance from the vehicle, on the other hand, acquire road information of a road at which the vehicle is currently located, and change the scale of the road image such that an equidistant circle selected on the basis of the road information of the road at which the vehicle is currently located among the plurality of equidistant circles becomes the largest equidistant circle placed within a display screen.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a driving assistance device that assists a vehicle in merging. [Background technology]

[0002] Conventionally, various means have been used as information providing means for providing vehicle occupants with various information for driving support, such as route guidance and obstacle warnings. For example, such means include display on a liquid crystal display (LCD) installed in the vehicle, audio output from a speaker, etc. Here, it is important for occupants to understand the road shape around the vehicle, and displaying a map image including the road shape around the current position of the vehicle on a display has conventionally been performed as one of the navigation functions.

[0003] Furthermore, in order to more accurately identify the situation around the vehicle, it has been proposed to display equidistance circles connecting points equidistant from the vehicle in addition to the map image (see, for example, Japanese Patent Application Laid-Open No. 2000-305452). Displaying equidistance circles makes it easier for occupants to grasp the sense of distance compared to when simply displaying a map image, and is an effective technique, particularly when merging into a main lane at an interchange or junction. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2000-305452 A (paragraphs 0020-0027, Figure 2) Summary of the Invention [Problem to be solved by the invention]

[0005] Here, when the map image displayed on the display is at a large scale, it is possible to obtain more detailed information, although the range is narrower, while when the scale is small, it is possible to obtain more coarse information, but a wider range of information. Since the type of information desired by the occupant differs depending on the vehicle situation, it is desirable to switch the scale appropriately depending on the vehicle situation. However, with the technology of Patent Document 1, although it is possible for the occupant to manually change the scale of the map image, it does not change the scale according to the vehicle situation.

[0006] The present invention has been made to solve the above-mentioned problems in the conventional art, and aims to provide a driving assistance device that makes it possible to display an image of the surrounding road at an appropriate scale according to the current vehicle situation by changing the scale of the road image so that an equidistant circle selected based on road information for the road on which the vehicle is currently located becomes the largest equidistant circle that can fit within the display screen. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the driving assistance device of the present invention comprises a road image display means for displaying on a display screen a road image showing the road shape around the current position of the vehicle, an equidistance circle display means for superimposing on the road image a plurality of equidistance circles connecting points at equal distances from the vehicle, with the distance from the vehicle being varied, a road information acquisition means for acquiring road information of the road on which the vehicle is currently located, and a scale change means for changing the scale of the road image so that an equidistance circle selected from the plurality of equidistance circles displayed by the equidistance circle display means based on the road information of the road on which the vehicle is currently located becomes the largest equidistance circle that can fit within the display screen. The "road image showing the road shape" may be an image showing only the road, or an image including facilities and nature (rivers, seas, etc.) in addition to the road. [Effects of the Invention]

[0008] According to the driving assistance device of the present invention having the above-described configuration, the scale of the road image is changed so that the equidistant circle selected based on the road information of the road on which the vehicle is currently located becomes the largest equidistant circle that can fit within the display screen, making it possible to display an image of the surrounding roads at an appropriate scale according to the current vehicle situation. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a block diagram showing a navigation device according to an embodiment of the present invention; [Figure 2] FIG. 1 is a diagram illustrating a probe car system for generating congestion information. [Figure 3] 4 is a flowchart of a merging support processing program according to the present embodiment. [Figure 4] FIG. 2 is a diagram showing an example of a road image displayed on a liquid crystal display. [Figure 5] FIG. 10 is a diagram illustrating an example in which a planned driving route includes a merging point where a vehicle travels on a merging lane that merges into a main lane and merges from the merging lane into the main lane. [Figure 6] FIG. 10 is a diagram illustrating an example in which a planned driving route includes a merging point where a vehicle travels on a merging lane that merges into a main lane and merges from the merging lane into the main lane. [Figure 7] FIG. 1 is a diagram illustrating a speed limit section and an acceleration lane at a merging point. [Figure 8] 10A and 10B are diagrams showing an example in which the scale of a road image displayed on a liquid crystal display is enlarged. [Figure 9] 10A and 10B are diagrams showing an example in which the scale of a road image displayed on a liquid crystal display is reduced. [Figure 10] 10 is a flowchart of a sub-processing program of a junction icon image display process. [Figure 11] FIG. 10 is a diagram illustrating a merging icon. [Figure 12] FIG. 10 is a diagram illustrating a merging icon. [Figure 13]10A and 10B are diagrams illustrating an example of how a merging icon is displayed on a liquid crystal display. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment in which a driving assistance device according to the present invention is embodied in a navigation device 1 will be described in detail below with reference to the drawings. First, the schematic configuration of the navigation device 1 according to this embodiment will be described using FIG. 1. FIG. 1 is a block diagram showing the navigation device 1 according to this embodiment. Note that, in the following embodiment, an example in which a navigation device functions as a driving assistance device will be described, but an in-vehicle device other than a navigation device or an information terminal connected to a vehicle may also function as a driving assistance device, and further, multiple in-vehicle devices or a combination of an in-vehicle device and an external server may also function as a driving assistance device.

[0011] As shown in FIG. 1 , the navigation device 1 according to this embodiment includes a current position detection unit 11 that detects the current position of the vehicle in which the navigation device 1 is installed, a data recording unit 12 that records various data, a navigation ECU 13 that performs various calculations based on input information, an operation unit 14 that accepts user operations, a liquid crystal display 15 that displays road images showing the road shapes around the vehicle, a speaker 16 that outputs audio guidance related to route guidance, a DVD drive 17 that reads DVDs as storage media, and a communication module 18 that communicates with information centers such as a probe center and a VICS (Vehicle Information and Communication System) center. The navigation device 1 is also connected to an external camera 19 and various sensors installed in the vehicle in which the navigation device 1 is installed via an in-vehicle network such as a CAN. The navigation device 1 is also connected to a vehicle control ECU 20 that performs various controls for the vehicle in which the navigation device 1 is installed, allowing bidirectional communication. Various operation buttons 21 installed in the vehicle, such as an automatic driving start button, are also connected.

[0012] Here, a vehicle equipped with the navigation device 1 is a vehicle capable of manual driving, in which the vehicle travels based on the user's driving operations, as well as assisted driving using automatic driving assistance, in which the vehicle travels automatically along a pre-set route or road without the user's driving operations.

[0013] Furthermore, autonomous driving assistance may be provided for all road sections, or may be configured to be provided only while the vehicle is traveling on a specific road section (for example, a highway with a gate (manned or unmanned, toll or free) at the boundary). In the following explanation, the autonomous driving section in which autonomous driving assistance is provided is assumed to be a general road or highway excluding narrow streets. However, autonomous driving assistance is not always provided when the vehicle is traveling on an autonomous driving section, but is only provided when the user selects to provide autonomous driving assistance (for example, by turning on the autonomous driving start button) and it is determined that autonomous driving assistance is possible. Furthermore, while driving with autonomous driving assistance is being performed, the driver can also switch to manual driving at their discretion.

[0014] In vehicle control in automated driving assistance, for example, the current position of the vehicle, the lane the vehicle is traveling on, and the positions of surrounding obstacles are detected as needed, and vehicle control of the steering, drive source, brakes, etc. is automatically performed so that the vehicle travels at a speed according to a speed plan generated along the travel trajectory or planned travel route (guidance route) generated by the navigation device 1. Note that in assisted travel using automated driving assistance in this embodiment, lane changes, merging operations, and right / left turn operations are also performed automatically by the automated driving assistance, but travel that requires special operations such as lane changes, merging operations, and right / left turns may be performed by manual driving without automated driving assistance.

[0015] Each of the components of the navigation device 1 will be explained below in order. The current position detection unit 11 is composed of a GPS 22, a vehicle speed sensor 23, a steering sensor 24, a gyro sensor 25, etc., and is capable of detecting the current vehicle position, direction, vehicle traveling speed, current time, etc. Here, the vehicle speed sensor 23 in particular is a sensor for detecting the vehicle's travel distance and speed, and generates pulses in response to the rotation of the vehicle's drive wheels and outputs the pulse signals to the navigation ECU 13. The navigation ECU 13 then calculates the rotation speed of the drive wheels and travel distance by counting the generated pulses. Note that the navigation device 1 does not need to be equipped with all four types of sensors described above, and the navigation device 1 may be configured to be equipped with only one or more of these types of sensors.

[0016] The data recording unit 12 also includes a hard disk (not shown) as an external storage device and recording medium, and a recording head (not shown) which is a driver for reading the map information DB 31 and predetermined programs recorded on the hard disk and for writing predetermined data to the hard disk. Note that the data recording unit 12 may be configured with a memory card or an optical disk such as a CD or DVD instead of a hard disk. The map information DB 31 may also be stored in an external server and acquired by the navigation device 1 through communication.

[0017] Here, the map information DB 31 is a storage means that stores, for example, link data 33 relating to roads (links), node data 34 relating to node points, branch point data 35 relating to branch points, road image data 36 for displaying road images described below, search data used for processing related to route search and change, facility data relating to facilities, intersection data relating to each intersection, search data for searching for locations, etc.

[0018] The link data 33 also includes data representing the width, gradient, cant, bank, road surface condition, merging section, road structure, speed limit set for the road, number of lanes on the road, points where the number of lanes decreases, points where the road width narrows, and railroad crossings for each link that makes up the road; data representing the radius of curvature, intersections, T-junctions, corner entrances and exits for corners; data representing downhill roads, uphill roads, and the like for road attributes; and data representing general roads such as national highways, prefectural roads, and narrow streets, as well as toll roads such as national expressways, urban expressways, motorways, general toll roads, and toll bridges for road types. In particular, in this embodiment, the information necessary for assisted driving using autonomous driving assistance is stored, and in addition to the number of lanes on the road, information identifying the traffic divisions in the direction of travel for each lane and the connections between roads (specifically, the correspondence between the lanes on the road before passing through the intersection and the lanes on the road after passing through the intersection), the speed limit set on the road, and information regarding dividing lines painted on the road (center lines, lane boundaries, outer lines of the road, guide lines, guidance strips, etc.) is also stored.

[0019] The node data 34 also includes data such as the coordinates (positions) of actual road branching points (including intersections, T-junctions, etc.) and node points set at predetermined distances on each road depending on the radius of curvature, node attributes indicating whether the node corresponds to an intersection, a connecting link number list which is a list of link numbers of links connecting to the node, an adjacent node number list which is a list of node numbers of nodes adjacent to the node via links, and the height (altitude) of each node point.

[0020] The branch point data 35 stores the intersection name of the branch point, corresponding node information identifying the node that forms the branch point, connecting link information identifying the link connected to the branch point, the destination name corresponding to the link connected to the branch point, information identifying the shape of the branch point, etc. In this embodiment, the branch points include "points where other roads merge (enter) a main road (hereinafter referred to as "merging points")" and "branch points where other roads branch off (exit) a main road (hereinafter referred to as "branch points")" that exist at interchanges, junctions, etc. The branch points also include merging points and branch points that exist not only on expressways but also on trunk roads such as national highways. Furthermore, for the merging points, the length (distance) of the lane that merges with the main lane at the merging point (hereinafter referred to as "merging lane") is also stored. Particularly at merging points on expressways, the merging lane also corresponds to a ramp or acceleration lane, and the length of the acceleration lane, for example, is stored.

[0021] The road image data 36 stored in the navigation system 100 is a road image showing the road shapes of roads nationwide that vehicles can travel on. The road image does not include images of facilities that are displayed in conventional map images, and is essentially an image of only the road portion. However, compared to conventional map images, the road image specifies more detailed information about the road, such as the number of lanes, the type of dividing lines, and the specific road shape. In the navigation device 1 of this embodiment, the above road image around the current location of the vehicle is displayed on the LCD display 15 while the vehicle is traveling, instead of a conventional map image.

[0022] Meanwhile, the navigation ECU (Electronic Control Unit) 13 is an electronic control unit that controls the entire navigation device 1. It includes a CPU 41 as a calculation device and control device, a RAM 42 that is used as a working memory when the CPU 41 performs various calculation processes and stores route data and the like when a route is searched, a ROM 43 that stores control programs as well as a merging assistance processing program (see FIG. 3 ) described below, and a flash memory 44 that stores programs read from the ROM 43. The navigation ECU 13 also includes various means as processing algorithms. For example, the road image display means displays a road image showing the road shape around the current vehicle position on a display screen. The equidistance circle display means displays multiple equidistance circles connecting points at equal distances from the vehicle, superimposed on the road image, at varying distances from the vehicle. The road information acquisition means acquires road information about the road on which the vehicle is currently located. The scale changing means changes the scale of the road image so that an equidistant circle selected based on road information of the road on which the vehicle is currently located among the plurality of equidistant circles displayed by the equidistant circle display means becomes the largest equidistant circle that fits within the display screen.

[0023] The operation unit 14 is operated when inputting a departure point as a starting point of a trip and a destination point as a destination of a trip, and has a plurality of operation switches (not shown) such as various keys and buttons. The navigation ECU 13 controls the execution of various corresponding operations based on switch signals output by pressing each switch. The operation unit 14 may have a touch panel provided on the front surface of the liquid crystal display 15. It may also have a microphone and a voice recognition device.

[0024] The liquid crystal display 15 also displays traffic information, operation guidance, operation menus, key guidance, guidance information along the guided route (planned driving route), news, weather forecasts, time, emails, television programs, etc. Note that a HUD or HMD may be used instead of the liquid crystal display 15. In particular, in this embodiment, a road image showing the road shape around the current position of the vehicle while the vehicle is traveling (regardless of whether it is automatic driving or manual driving) is displayed on the liquid crystal display 15. Furthermore, when the vehicle approaches a merging point, an icon image showing the situation of the merging point in a simplified form that is easy for the user to visually recognize is also displayed as necessary. Details of the road image and icon image will be described later.

[0025] Furthermore, the speaker 16 outputs audio guidance for guiding the vehicle along a guide route (planned travel route) based on instructions from the navigation ECU 13, and traffic information guidance.

[0026] The DVD drive 17 is a drive that can read data recorded on a recording medium such as a DVD or CD. Based on the read data, music and video are played, and the map information DB 31 is updated. Instead of the DVD drive 17, a card slot for reading and writing data to a memory card may be provided.

[0027] The communication module 18 is a communication device for receiving traffic information, probe information, weather information, etc. transmitted from a traffic information center, such as a VICS center or a probe center, and corresponds to, for example, a mobile phone or DCM. It also includes a vehicle-to-vehicle communication device for communicating between vehicles and a road-to-vehicle communication device for communicating with roadside devices.

[0028] Furthermore, the navigation device 1 according to this embodiment is capable of acquiring, via a communication module 18, congestion information indicating the congestion status for each lane, which is generated in an external server device 51 provided in a probe center 50, as shown in particular in FIG. 2. The server device 51, together with a plurality of vehicles 52 communicably connected to the server device 51, constitutes a so-called probe car system 53. Here, the probe car system 53 is a system that collects information using the vehicles 52 as sensors. Specifically, the vehicle 52 transmits speed data and the operating status of each system, such as steering operation and shift position, together with GPS position information, to the probe center 50 via a communication device previously installed in the vehicle 52, and the collected data is reused at the center side as various information.

[0029] The server device 51 provided in the probe center 50 is an information management server that appropriately collects and stores probe information (material information) including the current time and driving information from each vehicle 52 traveling throughout the country, generates various types of support information related to roads (for example, road closure information, accident information, traffic congestion information, travel time, etc.) from the stored probe information, distributes the generated support information to the navigation device 1, and performs various processes using the support information. In particular, in this embodiment, the server device 51 collects from each vehicle 52 the current position coordinates and vehicle speed of the vehicle 52, and images of the surrounding area captured by the external camera 19 provided in the vehicle 52, and generates data indicating the traffic congestion status for each lane by statistically or analytically analyzing the collected information, and can distribute the data to the vehicle 52.

[0030] However, the traffic congestion information acquired by the navigation device 1 does not necessarily have to be traffic congestion information generated by the above-mentioned probe car system 53, and may be traffic congestion information generated by other means as long as the information can identify the traffic congestion situation for each lane.

[0031] The exterior camera 19 is composed of a camera using a solid-state image sensor such as a CCD, and is attached above the vehicle's front bumper or behind the rearview mirror, with its optical axis oriented downward at a predetermined angle from the horizontal. The exterior camera 19 captures an image of the area ahead of the vehicle when the vehicle is traveling in an autonomous driving zone. The vehicle control ECU 20 processes the captured image to detect lane markings on the road the vehicle is traveling on and other vehicles in the vicinity, and controls the autonomous driving of the vehicle based on the detection results. The exterior camera 19 is also used to detect traffic congestion conditions by the server device 51. The exterior camera 19 may be configured to be located behind or to the side of the vehicle, in addition to the front. Instead of a camera, a sensor such as a millimeter-wave radar, vehicle-to-vehicle communication, or road-to-vehicle communication may be used to detect other vehicles.

[0032] The vehicle control ECU 20 is an electronic control unit that controls the vehicle equipped with the navigation device 1. The vehicle control ECU 20 is also connected to each drive unit of the vehicle, such as the steering, brakes, and accelerator, and in this embodiment, after automatic driving assistance has started in the vehicle, the vehicle control ECU 20 controls each drive unit to implement automatic driving assistance for the vehicle. If an override is performed by the user during automatic driving assistance, the ECU 20 detects that an override has been performed.

[0033] Here, the navigation ECU 13 transmits various types of assistance information related to autonomous driving assistance generated by the navigation device 1 to the vehicle control ECU 20 via the CAN when the planned driving route (guidance route) of the vehicle is determined or after the vehicle starts driving. The vehicle control ECU 20 then uses the received various types of assistance information to provide autonomous driving assistance after the vehicle starts driving. Examples of assistance information include a recommended driving path for the vehicle, a speed plan indicating the vehicle speed during driving, etc. Note that it is also possible to transmit information specifying the planned driving route (guidance route) that specifies the route the vehicle will travel, without transmitting the specific driving path.

[0034] Next, a merging support processing program executed by the navigation ECU 13 in the navigation device 1 having the above configuration will be described with reference to Fig. 3. Fig. 3 is a flowchart of the merging support processing program according to this embodiment. The merging support processing program is executed after the ACC (accessory power supply) of the vehicle is turned on, and supports vehicle driving, particularly at merging points, by displaying a road image showing the shape of the road around the vehicle on the LCD display 15. The programs shown in the flowcharts in Figs. 3 and 10 below are stored in the RAM 42 and ROM 43 provided in the navigation device 1, and are executed by the CPU 41. In the following description, it is assumed that the vehicle is being driven manually at the start of driving immediately after the ACC power supply is turned on; however, it is also possible to drive with automatic driving assistance from the start of driving.

[0035] First, in step (hereinafter abbreviated as S) 1, the CPU 41 identifies the current position of the vehicle based on the detection result of the current position detection unit 11 and map information. When identifying the current position of the vehicle, a map matching process is also performed to match the current position of the vehicle with the map information.

[0036] Next, in S2, the CPU 41 acquires road image data 36 of the area around the current vehicle position from the map information DB 31. Here, as described above, the road image data 36 is data in which road images showing the road shape of the road are stored, and is an image that specifies more detailed information about the road, such as the number of lanes, the type of dividing lines, and the specific road shape, compared to conventional map images.

[0037] Next, in S3, the CPU 41 displays a road image showing the road shape around the current vehicle position on the LCD display 15 based on the road image data 36 acquired in S2. FIG. 4 shows an example of a road image 61 displayed on the LCD display 15. As shown in FIG. 4, the road image 61 is a bird's-eye view image of the area around the vehicle, viewed diagonally downward from above behind the vehicle. The road image 61 displays only roads, and does not generally display facilities other than roads. However, some facilities (e.g., destination, home, toll booth, ETC gate, etc.) may be included in the display. The road image 61 also clearly displays the number of lanes and the type of markings on the road, and reflects detailed road shapes such as the curvature of curves, resulting in an image showing a more realistic road shape. Furthermore, a vehicle icon 62 indicating the current position of the vehicle and a planned driving trajectory 63 indicating the planned driving route of the vehicle are also displayed. If the location of another vehicle around the vehicle can be identified, a vehicle icon 64 indicating the current location of the other vehicle is also displayed. The current positions of other vehicles can be obtained from the vehicle exterior camera 19 or from the server device 51 that collects position information of each vehicle.

[0038] In addition, equidistant circles connecting points equidistant from the vehicle are superimposed on the road image 61. In particular, in this embodiment, three equidistant circles are displayed: a first equidistant circle 65 connecting points 25 m from the vehicle, a second equidistant circle 66 connecting points 50 m from the vehicle, and a third equidistant circle 67 connecting points 100 m from the vehicle. However, the number of equidistant circles may be two or more, and the distance from the vehicle can also be changed as appropriate. As will be described later, the scale of the road image 61 is changed as appropriate depending on the vehicle situation. In the initial state, as shown in FIG. 4, the scale is set so that the third equidistant circle 67 is the largest equidistant circle that can fit within the display screen. In addition, the current time, gear position, current vehicle speed, remaining battery power (only for hybrid vehicles and electric vehicles), etc. are also displayed at the top of the screen. In addition, the road image 61 is basically displayed continuously on the LCD display 15 until the vehicle has finished traveling. If the current position of the vehicle changes, the content of the road image 61 displayed is updated accordingly.

[0039] Furthermore, the same road image 61 is displayed on the LCD display 15 whether the vehicle is traveling with automated driving assistance or manual driving assistance. However, the background color of the road image 61 is changed, for example, to enable identification of whether the vehicle is currently traveling with automated driving assistance or manual driving assistance. For example, the background is displayed in gray when the vehicle is traveling manually immediately after starting driving. Thereafter, if the user selects to perform automated driving assistance (for example, by pressing the automatic driving start button) in a situation where it is determined that automated driving assistance is possible, driving with automated driving assistance begins (S4: YES), and the background color of the road image 61 is displayed in blue to indicate that the vehicle is traveling with automated driving assistance (S5). In addition to the background color, the display colors of the icons and equidistant circles included in the road image 61 may also be changed. Note that a situation where it is determined that automated driving assistance is possible is, for example, when the vehicle is traveling on a general road or expressway that is an automated driving section, and information necessary for automated driving assistance, such as lane markings and lane information, is available.

[0040] On the other hand, if the vehicle continues to be driven manually without being driven with automatic driving assistance (S4: NO), the background is displayed in gray (S6). Also, if the occupant overrides the control and switches back to manual driving from driving with automatic driving assistance, the background color of the road image 61 also returns to gray.

[0041] Next, in S7, the CPU 41 acquires a route along which the vehicle is scheduled to travel (hereinafter referred to as the planned travel route). The planned travel route of the vehicle is, for example, a recommended route to a destination set by the user and searched by the navigation device 1 or an external server device connected for communication. If a destination is not set, the planned travel route may be a route along which the vehicle travels from the current position of the vehicle.

[0042] Next, in S8, the CPU 41 acquires road information within a predetermined distance (e.g., 3 km) ahead in the direction of travel of the vehicle along the planned travel route acquired in S7 from the map information DB 31. Specifically, the CPU 41 acquires information on the type of road to travel, whether or not there is a branch point, and, if there is a branch point, what shape the branch point has.

[0043] Then, in S9, the CPU 41 determines, based on the road information acquired in S8, whether the planned driving route within a predetermined distance (e.g., 3 km) ahead in the vehicle's direction of travel is a planned driving route in which the vehicle travels on a merging lane that merges into a main lane and merges from the merging lane into the main lane at a merging point. Such a planned driving route corresponds to, for example, a planned driving route when traveling through an interchange where a general road other than an expressway merges into the main lane of an expressway, or a junction where an expressway merges into the main lane of another expressway. In particular, at a merging point on an expressway, the merging lane also corresponds to a ramp or acceleration lane. Meanwhile, planned driving routes that merge from another general road into the main lane of a highway, such as a national highway, are also included in the target of S9, not limited to expressways.

[0044] Therefore, for example, if the planned driving route of the vehicle is a planned driving route that enters an expressway from an ordinary road at an interchange as shown in Figure 5, the vehicle will travel on merging lane 70 and merge from merging lane 70 into main lane 71 at the merging point, so S9: YES is determined. On the other hand, if the planned driving route of the vehicle is a planned driving route that enters a different expressway at a junction as shown in Figure 6, the vehicle will travel on merging lane 70 and merge from merging lane 70 into main lane 71 at the merging point, so S9: YES is also determined.

[0045] If it is determined that the planned driving route within a predetermined distance ahead in the vehicle's direction of travel is one in which the vehicle travels on a merging lane that merges into a main lane and merges from the merging lane into the main lane at the merging point (S9: YES), the process proceeds to S10. On the other hand, if it is determined that the planned driving route is not one in which the vehicle travels on a merging lane that merges into a main lane at the merging point (S9: NO), the process proceeds to S20.

[0046] In S10, the CPU 41 determines whether the vehicle has entered a 40 km / h speed limit zone. A 40 km / h speed limit zone is typically located on the near side of an acceleration lane on a highway ramp. Specifically, as shown in FIG. 7, a 40 km / h speed limit zone is established on a one-way road section that branches off from another highway or that leads from a general road via a toll gate, and typically has a speed limit of 40 km / h. As shown in FIG. 7, a road sign 73 indicating the start of the speed limit is installed at the start of the speed limit zone. By recognizing the road sign 73 with the exterior camera 19, it is possible to determine whether the vehicle has entered a 40 km / h speed limit zone. However, by including information identifying the speed limit zone in advance in the map information, it is also possible to determine whether the vehicle has entered a speed limit zone based on the vehicle's current position. The determination process in S10 is omitted when the vehicle is traveling at a merging point onto a general road.

[0047] If it is determined that the vehicle has entered a 40 km / h speed limit zone (S10: YES), the process proceeds to S11. On the other hand, if it is determined that the vehicle has not entered a 40 km / h speed limit zone (S10: NO), the process waits until the vehicle enters the zone.

[0048] In S11, the CPU 41 changes the scale of the road image 61 displayed on the liquid crystal display 15. Specifically, as shown in FIG. 8, a second equidistant circle 66 connecting points 50 m from the vehicle is selected, and the scale is changed so that the selected second equidistant circle 66 becomes the largest equidistant circle that can fit within the display screen. Until the vehicle entered the speed limit zone, the third equidistant circle 67 connecting points 100 m from the vehicle was selected as the largest equidistant circle that could fit within the display screen. In other words, if the speed limit set for the road section where the vehicle is currently located changes to a slower speed (e.g., from 80 km / h to 40 km / h), the selected equidistant circle is changed to one closer to the vehicle, and the scale of the road image is enlarged. As a result, the user can grasp the situation around the vehicle in more detail from the road image 61. Note that when the vehicle is traveling at a low speed, information about distant areas is not very important, and it is important to be able to grasp the area around the vehicle in more detail. In addition, in the example shown in FIG. 8, the scale is changed so that the second isodistant circle 66 becomes the largest isodistant circle that can fit within the display screen, but the scale may also be changed so that the first isodistant circle 65 becomes the largest isodistant circle that can fit within the display screen.

[0049] Thereafter, in S12, the CPU 41 performs a merging icon image display process (FIG. 10) to be described later. The merging icon image display process is a process for additionally displaying an icon image showing the status of the merging point in a simplified form that is easy for the user to visually recognize, as necessary.

[0050] Next, in S13, the CPU 41 determines whether the vehicle has exited a 40 km / h speed limit zone. At the end of the speed limit zone (which also corresponds to the start of the acceleration lane), a road sign 74 indicating that the speed limit has been lifted is installed, as shown in FIG. 7, and it is possible to determine whether the vehicle has exited the 40 km / h speed limit zone by recognizing the road sign 74 with the outside camera 19. However, if the map information contains information specifying the speed limit zone in advance, it is also possible to determine whether the vehicle has exited the speed limit zone based on the current position of the vehicle. Note that the determination process of S13 is omitted when the vehicle is traveling at a merging point onto an ordinary road.

[0051] If it is determined that the vehicle has exited the 40 km / h speed limit zone (S13: YES), the process proceeds to S14. On the other hand, if it is determined that the vehicle has not exited the 40 km / h speed limit zone (S13: NO), the process waits until the vehicle has exited.

[0052] In S14, the CPU 41 changes the scale of the road image 61 displayed on the liquid crystal display 15. Specifically, as shown in FIG. 9, a third equidistant circle 67 connecting points 100 m from the vehicle is selected, and the scale is changed so that the selected third equidistant circle 67 becomes the largest equidistant circle that can fit within the display screen. Until the vehicle exited the speed limited section, the second equidistant circle 66 connecting points 50 m from the vehicle was selected as the largest equidistant circle that could fit within the display screen. In other words, if the speed limit set for the road section in which the vehicle is currently located increases (for example, from 40 km / h to 80 km / h), the selected circle is changed to an equidistant circle that is farther away from the vehicle, and the scale of the road image is reduced. As a result, the user can grasp the situation around the vehicle in a wider range from the road image 61. In addition, the road image 61 also displays other vehicle icons 64 indicating the current location of other vehicles, so by reducing the road image 61 (widening the display range), it notifies the driver that he or she has entered the acceleration lane (preparing to merge), and also has the advantage of making it easier to grasp the location of other vehicles located in the main lane.

[0053] Thereafter, in S15, the CPU 41 hides the icon image that was displayed in S12 when the host vehicle enters the acceleration lane, i.e., when the host vehicle starts preparing to merge. However, the icon image may be displayed not until the host vehicle enters the acceleration lane, but until the host vehicle has completed merging.

[0054] Next, in S16, the CPU 41 determines whether the vehicle speed of the vehicle has dropped below a threshold based on the detection result of the vehicle speed sensor 23. The threshold is set for each road type, e.g., 40 km / h for expressways and 10 km / h for general roads. A situation in which the vehicle speed drops below the threshold even though the road section is not a speed limit section indicates that the road section on which the vehicle is currently located has changed from an unoccupied state to a congested or crowded state. However, in S16, a change in the degree of congestion on the road section on which the vehicle is currently located may be detected based on the congestion information acquired via the communication module 18 and the vehicle's current position.

[0055] If it is determined that the vehicle speed of the vehicle has decreased below the threshold (S16: YES), that is, if the road section where the vehicle is currently located has changed from an open state to a congested or jammed road, the process proceeds to S17. On the other hand, if it is determined that the vehicle speed of the vehicle has not decreased below the threshold (S16: NO), the process proceeds to S20.

[0056] In S17, the CPU 41 changes the scale of the road image 61 displayed on the LCD display 15. Specifically, as in S11, the second equidistant circle 66 connecting points 50 m from the vehicle is selected, and the scale is changed so that the selected second equidistant circle 66 becomes the largest equidistant circle that can fit within the display screen. Before the vehicle speed decreased, the third equidistant circle 67 connecting points 100 m from the vehicle was selected as the largest equidistant circle that could fit within the display screen. In other words, if the degree of congestion in the road section where the vehicle is currently located changes to an increasing level, the selected equidistant circle is changed to one that is closer to the vehicle, and the scale of the road image is enlarged. As a result, the user can grasp the situation around the vehicle in more detail from the road image 61. Note that when the vehicle is traveling at a low speed, information about distant areas is not very important, and it is important to be able to grasp the area around the vehicle in more detail.

[0057] Next, in S18, the CPU 41 determines whether the vehicle speed of the host vehicle has recovered to above a threshold value based on the detection result of the vehicle speed sensor 23. The threshold value is set for each road type, for example, 40 km / h for expressways and 10 km / h for ordinary roads. Here, a situation in which the vehicle speed of the host vehicle has recovered from a state below the threshold value to above the threshold value indicates that the road section on which the vehicle is currently located has changed from a congested or crowded state to an open state. However, in S18, a change in the degree of congestion on the road section on which the vehicle is currently located may also be detected based on the congestion information acquired via the communication module 18 and the current position of the vehicle.

[0058] If it is determined that the vehicle speed of the vehicle has recovered to above the threshold (S18: YES), that is, if the road section where the vehicle is currently located has changed from a congested or crowded state to an open state, the process proceeds to S19. On the other hand, if it is determined that the vehicle speed of the vehicle has not recovered to above the threshold (S18: NO), the process waits until the speed recovers.

[0059] In S19, the CPU 41 changes the scale of the road image 61 displayed on the liquid crystal display 15. Specifically, as in S14, the third equidistant circle 67 connecting points 100 m from the vehicle is selected, and the scale is changed so that the selected third equidistant circle 67 becomes the largest equidistant circle that can fit within the display screen. Before the vehicle speed recovered, the second equidistant circle 66 connecting points 50 m from the vehicle was selected as the largest equidistant circle that can fit within the display screen. In other words, if the congestion level in the road section where the vehicle is currently located changes to a lower level, the selected circle is changed to an equidistant circle that is farther away from the vehicle, and the scale of the road image is reduced. As a result, the user can grasp the situation around the vehicle in a wider range from the road image 61.

[0060] Thereafter, in S20, the CPU 41 determines whether the vehicle has finished traveling. For example, the CPU 41 determines that the vehicle has finished traveling when the vehicle has arrived at a set destination or when the ACC power supply (accessory power supply) is turned off.

[0061] If it is determined that the vehicle has finished traveling (S20: YES), the road image 61 displayed on the liquid crystal display 15 is hidden and the merging support processing program is terminated. On the other hand, if it is determined that the vehicle has not finished traveling (S20: NO), the process returns to S1 and the road image 61 continues to be displayed.

[0062] Next, the sub-processing of the merging icon image display processing executed in S12 will be described with reference to Fig. 10. Fig. 10 is a flowchart of a sub-processing program of the merging icon image display processing.

[0063] First, in S21, the CPU 41 acquires, as merging point information regarding the merging point, the length of the merging lane through which the vehicle will be traveling and the congestion status of the main lane into which the vehicle will be merging.

[0064] The length of the merging lane is the length of the driving section where preparations for merging into the main lane (for example, acceleration) and merging are possible, and for expressways, the length of the acceleration lane between the exit of the speed limit section and the merging point shown in Figure 7 is acquired as the length of the merging lane. Note that the length of the acceleration lane is not fixed nationwide, but varies for each merging point, and is stored in advance in the map information DB 31. Because the vehicle is traveling in a speed limit section at the time the merging icon image display process is executed, in S21 the length of the acceleration lane ahead of the speed limit section in which the vehicle is currently traveling is acquired from the map information DB 31.

[0065] Meanwhile, the congestion status of the main lane is acquired from an external server device 51, and in particular, the information is used to identify whether the main lane is empty, congested, or congested. The congestion status is identified by the server device 51, for example, based on the average vehicle speed of traveling vehicles, with empty indicating the least crowded road condition and congested indicating the most congested road condition. As mentioned above, the server device 51 can provide detailed congestion information for each lane by collecting probe information from each traveling vehicle (FIG. 2). However, if the congestion status of the main lane can be identified using the exterior camera 19 equipped on the vehicle, the congestion status of the main lane may be identified on the vehicle side without going through the server device 51.

[0066] Next, in S22, the CPU 41 determines whether the vehicle is currently traveling with automatic driving assistance or manually.

[0067] If it is determined that the vehicle is currently traveling with automatic driving assistance (S22: YES), the process proceeds to S23. On the other hand, if it is determined that the vehicle is currently traveling with manual driving (S22: NO), the process proceeds to S26.

[0068] In S23, the CPU 41 determines whether the congestion state of the main lane into which the vehicle is about to merge is "congested" or "uncongested" based on the congestion state of the main lane acquired in S21.

[0069] If the congestion situation of the main lane into which the vehicle is about to merge is determined to be "congested" or "uncongested" (S23: YES), the process proceeds to S25. On the other hand, if the congestion situation of the main lane into which the vehicle is about to merge is determined to be "congested" (S23: NO), the process proceeds to S24.

[0070] In S24, the CPU 41 generates an icon image (hereinafter referred to as a merging icon) that shows the situation of the merging point in a simplified form that is easy for the user to visually recognize, and additionally displays it on the liquid crystal display 15.

[0071] FIG. 11 is a diagram showing an example of a merging icon 81 generated and displayed in S24. As shown in FIG. 11, the merging icon 81 shows a simplified road shape near the merging point. Note that the merging icon 81 does not show the detailed road shape at the merging point, and therefore basically displays the same road shape image at any merging point (except for the portion corresponding to the length of the merging lane, which will be described later). The merging icon 81 also displays an image indicating the congestion status of the main lane in a location corresponding to the main lane. Specifically, other vehicle icons 82 indicating other vehicles are displayed in a location corresponding to the main lane, and the congestion status is indicated by the number of other vehicle icons 82 displayed. As shown in FIG. 11, if the main lane is quiet, the other vehicle icons 82 are not displayed, thereby visually indicating that the main lane is empty. If the main lane is congested, the other vehicle icons 82 are displayed in a small number (e.g., three vehicles) to visually indicate that the main lane is somewhat congested. Furthermore, if the main lane is congested, a large number of other vehicle icons 82 (for example, 10) are displayed to visually indicate that the main lane is congested. Note that, because the other vehicle icons 82 are intended to indicate the congestion status of the main lane, the number and display positions of the other vehicle icons 82 displayed in the merging icon 81 are unrelated to the number and positions of other vehicles actually on the main lane. In other words, if the main lane is congested, the number and display positions of the other vehicle icons 82 are always displayed in the manner shown in the middle diagram of FIG. 11, regardless of the positions of other vehicles. Similarly, if the main lane is congested, the number and display positions of the other vehicle icons 82 are always displayed in the manner shown in the bottom diagram of FIG. 11, regardless of the positions of other vehicles.

[0072] Furthermore, an image indicating the length of the merging lane is also displayed in the portion of the merging icon 81 that corresponds to the merging lane. Specifically, as shown in FIG. 12, the length of the road portion that corresponds to the merging lane in the merging icon 81 is changed to indicate the length of the merging lane to the merging point. As shown in FIG. 12, if the length of the merging lane is less than a threshold (for example, less than 300 m), an image 83 of the road that corresponds to the merging lane is displayed short, which visually indicates that the merging lane is short, i.e., the section where preparations for merging can be made or the section where merging is possible is short. Furthermore, if the length of the merging lane is equal to or greater than the threshold (for example, 300 m or more), an image 83 of the road that corresponds to the merging lane is displayed long, which visually indicates that the merging lane is long, i.e., the section where preparations for merging can be made or the section where merging is possible is short.

[0073] FIG. 13 is a diagram showing an example of the merging icon 81 displayed on the liquid crystal display 15. As shown in FIG. 13, the merging icon 81 is displayed in the lower right corner of the road image 61 so as not to obstruct the display of the road image 61 as much as possible. By visually checking the merging icon 81, a user traveling in a speed limited section can visually and easily grasp the length of the merging lane (acceleration lane) through which the vehicle will be traveling and the congestion situation of the main lane into which the vehicle will be merging. Note that the merging icon 81 displayed on the liquid crystal display 15 is hidden when the host vehicle enters the acceleration lane, i.e., when the host vehicle begins preparations for merging (S15). However, the merging icon 81 may be displayed until the merging is completed, rather than until the host vehicle enters the acceleration lane.

[0074] On the other hand, in S25, the CPU 41 ends the merging icon image display process without displaying the merging icon 81 (S25).

[0075] As described above, when the vehicle is traveling by autonomous driving (S22: YES), the merging icon 81 is displayed, particularly when the main lane is congested. Here, when the main lane is congested, merging with autonomous driving assistance is more difficult than when the main lane is deserted or congested. Therefore, since it may be necessary to stop traveling with autonomous driving assistance and switch to manual driving, the merging icon 81 is displayed to allow the user to understand the situation at the merging point in advance. On the other hand, when the main lane is deserted or congested, merging with autonomous driving assistance is relatively easy, and assuming that traveling with autonomous driving assistance will continue in the future, it is determined that there is no need to make the user understand the situation at the merging point in advance, and the merging icon 81 is not displayed.

[0076] In S26, the CPU 41 acquires the vehicle's travel history. The vehicle's travel history is, for example, information specifying routes that the vehicle has traveled in the past, and is stored in the data recording unit 12, for example.

[0077] Thereafter, in S27, the CPU 41 determines, based on the vehicle's travel history acquired in S26, whether the vehicle has previously merged at the same merging point where the vehicle is about to merge multiple times (e.g., three or more times). Note that the number of times that constitutes the multiple times condition may be changed as appropriate, and may be at least one time instead of multiple times.

[0078] If it is determined that the vehicle has merged at the same merging point multiple times in the past (e.g., three or more times) (S27: YES), the process proceeds to S28. On the other hand, if it is determined that the vehicle has not merged at the same merging point multiple times in the past (e.g., three or more times) (S27: NO), the process proceeds to S29.

[0079] In S28, the CPU 41 determines whether the congestion state of the main lane into which the vehicle is about to merge is "low congestion" based on the congestion state of the main lane acquired in S21.

[0080] If it is determined that the congestion situation in the main lane into which the vehicle is about to merge is "clear" (S28: YES), the process proceeds to S25. That is, the merging icon image display process is terminated without displaying the merging icon 81. On the other hand, if it is determined that the congestion situation in the main lane into which the vehicle is about to merge is "congested" or "jammed" (S28: NO), the process proceeds to S24. That is, the merging icon 81 is additionally displayed on the liquid crystal display 15.

[0081] As described above, when the vehicle is being driven manually and has a history of having traveled through the same merging point in the past (S27: YES), the merging icon 81 is displayed especially when the main lane is congested or crowded, and is not displayed when the main lane is not crowded. Here, if the user has previously merged at the same merging point, it is considered that the merging operation is relatively easy for the user, so in a situation where the main lane where merging is considered easy is particularly quiet, it is determined that there is no need to inform the user of the situation at the merging point in advance, and the merging icon 81 is not displayed. On the other hand, when the main lane is congested or crowded, although this is not so necessary, the merging icon 81 is displayed to allow the occupants to confirm in advance so that the user can understand the situation at the merging point in advance.

[0082] On the other hand, in S29, the CPU 41 determines whether the length of the merging lane on which the vehicle is traveling is equal to or greater than a threshold value (e.g., 300 m) and the congestion state of the merging main lane is “clear” based on the length of the merging lane and the congestion state of the main lane obtained in S21.

[0083] If the length of the merging lane on which the vehicle is traveling is equal to or greater than a threshold value (e.g., 300 m) and the congestion status of the merging main lane is determined to be "clear" (S29: YES), the process proceeds to S25. That is, the merging icon image display process is terminated without displaying the merging icon 81. On the other hand, if the length of the merging lane on which the vehicle is traveling is less than the threshold value (e.g., 300 m), or is equal to or greater than the threshold value but the congestion status of the merging main lane is determined to be "congested" or "congested" (S29: NO), the process proceeds to S24. That is, the merging icon 81 is additionally displayed on the liquid crystal display 15.

[0084] As described above, when the vehicle is being driven manually and there is no history of having traveled through the same merging point in the past (S27: NO), the merging icon 81 is not displayed only when the merging lane (acceleration lane) is long and the main lane is deserted, and is displayed in other cases. Here, when merging at a merging point that the user has never experienced before (or has little experience with), the merging operation is likely to be relatively difficult for the user, so the merging icon 81 is not displayed only in situations where merging is likely to be particularly easy, such as when the section where merging preparations (acceleration, etc.) can be made or the section where merging is possible is sufficiently long and the main lane is deserted. On the other hand, in other situations, the merging icon 81 is displayed to allow the user to understand the situation at the merging point in advance.

[0085] As explained in detail above, the navigation device 1 and the computer program executed by the navigation device 1 according to this embodiment display a road image showing the shape of the roads around the current position of the vehicle, as well as multiple equidistant circles connecting points that are equidistant from the vehicle, superimposed on the road image and varying the distance from the vehicle (S3), while obtaining road information for the road on which the vehicle is currently located (S8), and changing the scale of the road image so that the equidistant circle selected from the multiple equidistant circles based on the road information for the road on which the vehicle is currently located becomes the largest equidistant circle that can fit within the display screen (S11, S14, S17, S19), thereby making it possible to display an image of the surrounding roads at an appropriate scale according to the current situation of the vehicle. In addition, the road information includes at least one of the speed limit information set for the road section where the vehicle is currently located and the congestion status of the road section where the vehicle is currently located, and the equidistant circle is selected based on the speed information set for the road section where the vehicle is currently located or the congestion status of the road section where the vehicle is currently located, making it possible to display an image of the surrounding road at an appropriate scale according to the vehicle's expected traveling speed. Furthermore, if the speed limit set for the road section on which the vehicle is currently located decreases as the vehicle travels, the scale of the road image is enlarged by changing the selection object to an equidistant circle that is closer to the vehicle (S11), and if the speed limit set for the road section on which the vehicle is currently located increases as the vehicle travels, the selection object is changed to an equidistant circle that is farther from the vehicle, and the scale of the road image is reduced (S14).Therefore, it is possible to enlarge the scale of the road image in situations where detailed information about the surrounding area is required, and to reduce the scale of the road information in situations where broader information rather than detailed information is required. Furthermore, if the degree of congestion on the road section where the vehicle is currently located changes to an increasing degree as the vehicle travels, the scale of the road image is enlarged by changing the selection object to an equidistant circle that is closer to the vehicle (S17), and if the degree of congestion on the road section where the vehicle is currently located changes to a decreasing degree as the vehicle travels, the selection object is changed to an equidistant circle that is farther from the vehicle, and the scale of the road image is reduced (S19).Therefore, it is possible to enlarge the scale of the road image in situations where detailed information about the surrounding area is required, and to reduce the scale of the road information in situations where broader information rather than detailed information is required.

[0086] The present invention is not limited to the above-described embodiment, and it goes without saying that various improvements and modifications are possible within the scope of the present invention. For example, although the merging icon 81 in this embodiment indicates the length of the merging lane and the congestion status of the main lane, it may also indicate only one of these. Alternatively, information other than the length of the merging lane and the congestion status of the main lane (for example, the number of lanes in the main lane, the shape of the road, etc.) may also be indicated. However, because detailed information about the merging point can be grasped from the road image 61, it is desirable to limit the amount of information provided by the merging icon 81 as much as possible to make it easier to grasp the status of the merging point.

[0087] In this embodiment, the road image 61 (FIG. 4) to be displayed on the liquid crystal display 15 excludes images of facilities that were displayed in conventional map images, and is basically an image of only the road portion, but a map image including the same facilities as in the conventional case may be displayed instead of the road image 61. Since the map image also includes the road shapes, the purpose can still be achieved in this case.

[0088] In this embodiment, the process from S10 onwards is executed when the planned driving route involves the vehicle merging from the merging lane to the main lane at a merging point (S9: YES), but if these conditions are not met, for example, even when the vehicle is traveling on a straight road, the process from S10 onwards may be executed (however, S12 is excluded). As a result, it becomes possible to enlarge and display the road image 61 when, for example, the vehicle is traveling in a speed limit section or a congested section even when the vehicle is traveling other than at a merging point.

[0089] In addition, in this embodiment, the road image 61 and the merging icon 81 are displayed on the liquid crystal display 15 of the navigation device 1, but the display that displays this information may be a display other than the liquid crystal display 15 as long as it is located inside the vehicle.

[0090] In this embodiment, the automatic driving control for automatically driving the vehicle without the user's driving operation has been described as the vehicle control ECU 20 controlling all of the accelerator operation, brake operation, and steering operation, which are operations related to the vehicle's behavior, among the vehicle operations. However, the automatic driving control may also be defined as the vehicle control ECU 20 controlling at least one of the accelerator operation, brake operation, and steering operation, which are operations related to the vehicle's behavior, among the vehicle operations. On the other hand, manual driving by the user's driving operation will be described as the user performing all of the accelerator operation, brake operation, and steering operation, which are operations related to the vehicle's behavior, among the vehicle operations.

[0091] In addition, in this embodiment, the processing of the merging assistance processing program (FIG. 3) is configured to be executed by the navigation ECU 13 of the navigation device 1, but the executing entity can be changed as appropriate. For example, the processing may be executed by the control unit of the liquid crystal display 15, the vehicle control ECU, or other in-vehicle device. [Explanation of symbols]

[0092] 1...navigation device (driving assistance device), 15...liquid crystal display, 31...map information DB, 36...road image data, 41...CPU, 42...RAM, 43...ROM, 61...road image, 62...own vehicle icon, 64...other vehicle icon, 65...first equidistant circle, 66...second equidistant circle, 67...third equidistant circle

Claims

1. road image display means for displaying on a display screen a road image showing the shape of roads around the current position of the vehicle; an equidistance circle display means for displaying a plurality of equidistance circles connecting points at equal distances from the vehicle by superimposing the equidistance circles on the road image, the equidistance circles being different distances from the vehicle; road information acquisition means for acquiring road information of the road on which the vehicle is currently located; a scale changing means for changing the scale of the road image so that, of the plurality of equidistance circles displayed by the equidistance circle display means, an equidistance circle selected based on road information of the road on which the vehicle is currently located becomes the largest equidistance circle that can fit within the display screen.

2. the road information includes at least one of speed limit information set for the road section where the vehicle is currently located and a congestion status of the road section where the vehicle is currently located; 2. The driving assistance device according to claim 1, wherein the scale changing means selects the equidistant circle based on speed limit information set for the road section where the vehicle is currently located or on a traffic congestion situation in the road section where the vehicle is currently located.

3. The scale changing means If the speed limit set for the road section where the vehicle is currently located changes to a slower speed as the vehicle travels, the scale of the road image is enlarged by changing the selected object to an equidistant circle that is closer to the vehicle; 3. The driving assistance device according to claim 2, wherein, when the speed limit set for the road section in which the vehicle is currently located increases as the vehicle travels, the scale of the road image is reduced by changing the selection target to an equidistant circle located farther from the vehicle.

4. The scale changing means If the degree of congestion in the road section where the vehicle is currently located changes in an increasing direction as the vehicle travels, the scale of the road image is enlarged by changing the selection target to an equidistant circle that is closer to the vehicle, 3. The driving assistance device according to claim 2, wherein, when the degree of congestion in the road section where the vehicle is currently located decreases as the vehicle travels, the scale of the road image is reduced by changing the selection target to an equidistant circle located farther from the vehicle.

Images