Road surface evaluation device

Abstract

To promptly assess the impact of snowfall on road surfaces. [Solution] The road surface evaluation device 10 includes an information acquisition unit 111 that acquires position information indicating the driving position of each of several vehicles traveling on the road, vehicle speed information indicating the driving speed corresponding to the driving position, wheel speed information indicating the rotation speed of the wheels, and lane change information indicating whether or not a lane change has occurred; a calculation unit 112 that calculates the current and past slip ratios of the wheels in a predetermined section of the road based on the vehicle speed information and wheel speed information; a determination unit 113 that determines whether or not snowfall has occurred in the predetermined section based on the slip ratio and lane change information; and an output unit 114 that outputs snowfall information including the determination result of the determination unit 113. The determination unit 113 determines that there is snowfall in the predetermined section when the current slip ratio includes a value that deviates by a predetermined amount or more from the average value of past slip ratios, and when the lane change information indicates that a lane change has occurred.

Description

Technical Field

[0001] The present invention relates to a road surface evaluation device for evaluating the condition of a road surface.

Background Art

[0002] Conventionally, as this type of device, there is known a device that monitors the road surface condition of a target area based on information indicating whether or not slip has occurred in drive wheels, which is acquired from a plurality of vehicles traveling on roads within the target area (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, on a road with heavy traffic, it is difficult to accumulate snow on the road surface near the passing position of the wheels, and it is difficult to evaluate the influence of snowfall on the road surface at the initial stage of snowfall.

Means for Solving the Problems

[0005] A road surface evaluation device according to one aspect of the present invention includes: an information acquisition unit that acquires position information indicating the driving position of each of a plurality of vehicles traveling on a road, vehicle speed information indicating the driving speed corresponding to the driving position, wheel speed information indicating the rotation speed of the wheels, and lane change information indicating whether or not a lane change has occurred; a calculation unit that calculates the current and past slip ratios of the wheels in a predetermined section of the road based on the vehicle speed information and wheel speed information acquired by the information acquisition unit; a determination unit that determines whether or not snowfall has occurred in the predetermined section based on the slip ratio calculated by the calculation unit and the lane change information; and an output unit that outputs snowfall information including the determination result of the determination unit. The determination unit determines that there is snowfall in the predetermined section when the current slip ratio includes a value that deviates by a predetermined amount or more from the average value of past slip ratios, and when the lane change information indicates that a lane change has occurred. [Effects of the Invention]

[0006] According to this invention, the impact of snowfall on road surfaces can be evaluated at an early stage. [Brief explanation of the drawing]

[0007] [Figure 1] A diagram showing an example of the configuration of a road surface evaluation system equipped with a road surface evaluation device according to an embodiment of the present invention. [Figure 2] A block diagram showing the main components of an in-vehicle device. [Figure 3] A block diagram showing the main components of the driving information storage device. [Figure 4] A block diagram showing the main components of a road surface evaluation device according to an embodiment of the present invention. [Figure 5] A diagram showing an example of a map of roads on which vehicles travel. [Figure 6A] A figure showing an example of a histogram illustrating the distribution of slip rates. [Figure 6B] A figure showing another example of a histogram illustrating the distribution of slip rates. [Figure 7] A flowchart showing an example of the processing performed in the calculation unit of Figure 4. [Figure 8] A flowchart showing the details of the process in step S15 of Figure 7. [Modes for carrying out the invention]

[0008] Embodiments of the present invention will be described below with reference to Figures 1 to 8. The road surface evaluation device according to the embodiment of the present invention is a device for evaluating the condition of the road surface on which a vehicle travels. Figure 1 is a diagram showing an example of the configuration of a road surface evaluation system equipped with the road surface evaluation device according to this embodiment. As shown in Figure 1, the road surface evaluation system 1 comprises a road surface evaluation device 10, an in-vehicle terminal 30, and a driving information storage device (hereinafter simply referred to as storage device) 40. The road surface evaluation device 10 and the storage device 40 are configured, for example, by a server device. The in-vehicle terminal 30 is configured to communicate with the road surface evaluation device 10 and the storage device 40 via a communication network 2.

[0009] Communication network 2 includes not only public wireless communication networks such as the Internet and mobile phone networks, but also closed communication networks established in designated management areas, such as wireless LAN, Wi-Fi (registered trademark), Bluetooth (registered trademark), etc.

[0010] The in-vehicle terminal 30 is installed in the vehicle 20. The vehicle 20 includes multiple vehicles 20-1, 20-2, ..., 20-n. The vehicle 20 may be a manually driven vehicle or an autonomous vehicle. Furthermore, the vehicle 20 may include vehicles of different make and model.

[0011] Figure 2 is a block diagram showing the main components of the in-vehicle terminal 30 according to this embodiment. The in-vehicle terminal 30 includes an electronic control unit (ECU) 31, a positioning sensor 32, an acceleration sensor 33, a steering angle sensor 34, a vehicle speed sensor 35, a wheel speed sensor 36, and a Telematic Control Unit (TCU) 37.

[0012] The positioning sensor 32 is, for example, a GPS sensor, which receives positioning signals transmitted from GPS satellites and detects the absolute position (latitude, longitude, etc.) of the vehicle 20. Note that the positioning sensor 32 includes not only GPS sensors but also sensors that use radio waves transmitted from GNSS satellites, including quasi-zenith orbit satellites, to determine position.

[0013] The acceleration sensor 33 detects the lateral acceleration of the vehicle 20. The acceleration sensor 33 may also be configured to detect longitudinal and vertical acceleration in addition to the lateral acceleration of the vehicle 20. The steering angle sensor 34 detects the steering angle of the vehicle 20's steering wheel (not shown). The vehicle speed sensor 35 detects the vehicle speed of the vehicle 20. The wheel speed sensor 36 detects the rotational speed of the vehicle 20's wheels.

[0014] As shown in Figure 2, the ECU 31 is configured to include a computer having an arithmetic unit 310 such as a CPU, a storage unit 320 such as ROM and RAM, and other peripheral circuits not shown such as an I / O interface. The arithmetic unit 310 functions as a sensor value acquisition unit 311 and a communication control unit 312 by executing a program that has been previously stored in the storage unit 320.

[0015] The sensor value acquisition unit 311 acquires the detection values ​​of each sensor 33 to 36 and the absolute position of the vehicle 20 detected by the positioning sensor 32 at predetermined intervals. The communication control unit 312 transmits the information acquired by the sensor value acquisition unit 311 (hereinafter referred to as driving information) along with a vehicle ID that can identify the vehicle 20 to the communication network 2 via the TCU 37 at predetermined intervals.

[0016] FIG. 3 is a block diagram showing the main configuration of the storage device 40 according to the present embodiment. The storage device 40 includes a computer having an arithmetic unit 41 such as a CPU, a storage unit 42 such as a ROM and a RAM, a communication unit 43, and other peripheral circuits (not shown) such as an I / O interface. The arithmetic unit 41 functions as an information receiving unit 411 by executing a program stored in the storage unit 42. The communication unit 43 is a communication interface that connects the storage device 40 to the communication network 2.

[0017] The information receiving unit 411 receives the driving information transmitted from each in-vehicle terminal 30 of the vehicles 20 traveling on the road. The information receiving unit 411 stores the driving information received from a plurality of vehicles 20 (in-vehicle terminals 30) in the storage unit 42. Note that the vehicle 20 that is the transmission source of the driving information can be specified by the vehicle ID attached to the driving information.

[0018] The driving information includes position information indicating the position of the vehicle 20, driving time information indicating the time when the vehicle 20 travels at that position, and acceleration information indicating the acceleration of the vehicle 20. The acceleration information includes information on the lateral acceleration of the vehicle 20 detected by the acceleration sensor 33. Further, the driving information includes vehicle speed information indicating the driving speed of the vehicle 20. The vehicle speed information indicates the sensor value of the vehicle speed sensor 35, that is, the measured value of the driving speed of the vehicle 20. Furthermore, the driving information includes steering angle information indicating the steering angle of the steering wheel of the vehicle 20. The steering angle information indicates the sensor value of the steering angle sensor 34, that is, the measured value of the steering angle of the vehicle 20.

[0019] FIG. 4 is a block diagram showing the main configuration of the road surface evaluation device 10 according to the present embodiment. The road surface evaluation device 10 detects snowfall on the road surface based on the driving information of a plurality of vehicles 20 stored in the storage device 40, specifically, vehicle speed information, wheel speed information, etc. The road surface evaluation device 10 outputs information including the detection result (hereinafter referred to as snowfall information) to a terminal possessed by a road management company or the like. The road management company or the like evaluates the state of the road surface using the snowfall information as reference data and considers the necessity of snow removal work and the like.

[0020] The road surface evaluation device 10 is comprised of a computer having a processing unit 110 such as a CPU, a storage unit 120 such as ROM and RAM, a communication unit 13, and other peripheral circuits (not shown) such as an I / O interface. The storage unit 120 stores map information, including road maps, and various information processed by the processing unit 110. The communication unit 13 is a communication interface that connects the road surface evaluation device 10 to the communication network 2.

[0021] The arithmetic unit 110 functions as an information acquisition unit 111, a calculation unit 112, a determination unit 113, and an output unit 114 by executing a program stored in the storage unit 120.

[0022] The information acquisition unit 111 acquires driving information from the storage device 40 via the communication unit 13 for multiple vehicles 20 traveling on roads that are subject to road surface evaluation (hereinafter referred to as evaluation target roads). Evaluation target roads are specified by the output instruction for snowfall information, which will be described later. Figure 5 shows an example of a map of the roads on which the vehicles 20 are traveling. In Figure 5, the section designated as an evaluation target road (latitude Y to Z of National Highway X) is filled with diagonal lines. In Figure 5, the upward direction corresponds to the north direction, and the rightward direction corresponds to the east direction.

[0023] Furthermore, the information acquisition unit 111 acquires past driving information of multiple vehicles 20 corresponding to the road under evaluation, specifically driving information during periods without snowfall, such as sunny days (hereinafter referred to as the non-snowfall period), from the storage device 40 via the communication unit 13. In addition, the information acquisition unit 111 acquires map information, including information on the road under evaluation, from the storage unit 120. The storage device 40 is assumed to have driving information acquired during the non-snowfall period stored in advance.

[0024] The calculation unit 112 calculates the slip ratio of the vehicle 20's wheels on the road under evaluation based on the driving information acquired by the information acquisition unit 111. Specifically, the calculation unit 112 calculates the slip ratio at the driving position indicated by the position information included in the driving information using the following equations (i) and (ii), based on the vehicle speed information and wheel speed information included in the driving information. When the driving speed of the vehicle 20 indicated by the vehicle speed information is greater than the wheel speed of the vehicle 20 indicated by the wheel speed information, the calculation unit 112 calculates the slip ratio using equation (i). On the other hand, when the driving speed of the vehicle 20 indicated by the vehicle speed information is less than the wheel speed of the vehicle 20 indicated by the wheel speed information, the calculation unit 112 calculates the slip ratio using equation (ii). The calculation unit 112 calculates the slip ratio from the current driving information and the past driving information, respectively.

[0025] Slip ratio = (vehicle speed - wheel speed) / vehicle speed …(i) Slip ratio = (vehicle speed - wheel speed) / wheel speed …(ii)

[0026] The determination unit 113 determines whether or not snowfall is occurring based on the slip ratio calculated by the calculation unit 112. More specifically, the determination unit 113 detects the initial stage of snowfall, specifically the stage from the start of snowfall until the entire road surface is covered with snow, for each predetermined section along the direction of travel of the road under evaluation. Hereinafter, the initial stage of snowfall will be referred to as the initial snowfall stage. On roads with relatively heavy traffic, such as main roads and expressways, immediately after snowfall begins, the snow accumulated on the road surface melts due to the pressure and friction from the wheels of moving vehicles. Therefore, snow does not easily accumulate in the areas where the wheels of moving vehicles pass (in the direction of the lane width). Consequently, there is no significant change in the slip ratio between the initial snowfall stage and the non-snowfall period.

[0027] On the other hand, snow tends to accumulate easily near lane boundaries where the wheels of moving vehicles rarely pass, even in the early stages of snowfall. Therefore, even in the early stages of snowfall, when a moving vehicle changes lanes, its wheels may slip on the lane boundary. Accordingly, the determination unit 113 detects the early stages of snowfall based on the slip rate when the vehicle 20 changes lanes. The detection of the early stages of snowfall by the determination unit 113 (hereinafter referred to as snowfall detection) will be described later.

[0028] The determination unit 113 determines that there is snowfall in any of the predetermined sections of the road under evaluation if the initial stages of snowfall are detected in that predetermined section, and determines that there is no snowfall on the road under evaluation if the initial stages of snowfall are not detected in any of the predetermined sections.

[0029] When the output unit 114 receives an output instruction for snowfall information from a terminal of a road management company or the like via the communication network 2, it generates information that associates information indicating the determination result of whether or not there is snowfall by the determination unit 113 with road information acquired by the information acquisition unit 111. The output unit 114 outputs the generated information as snowfall information to the terminal that sent the output instruction or to a predetermined output destination (display device or terminal, etc.).

[0030] More specifically, when the output unit 114 receives an output instruction, the information acquisition unit 111 acquires current driving information of multiple vehicles 20 corresponding to the road to be evaluated specified in the output instruction from the storage device 40 via the communication unit 13. The information acquisition unit 111 also acquires past driving information of multiple vehicles 20 corresponding to the road to be evaluated from the storage device 40. The calculation unit 112 calculates the slip ratio of the vehicles 20 on the road to be evaluated based on the current and past driving information acquired by the information acquisition unit 111. The determination unit 113 determines whether or not there is snowfall on the road to be evaluated for each predetermined section based on the slip ratio calculated by the calculation unit 112. The output unit 114 outputs the snowfall information, including the determination result of the determination unit 113, to a destination terminal or the like.

[0031] The snowfall information output instruction includes target road information that allows for the identification of the road to be evaluated. This target road information includes information indicating the name of the road to be evaluated and the extent of its section, such as "Road: National Highway X, Section: Latitude Y~Z". Note that information other than latitude may be used to specify the road to be evaluated. For example, longitude may be used instead of latitude, or longitude may be used in addition to latitude. The distance from the starting point of the section may also be used.

[0032] The instruction to output snowfall information may be input to the road surface evaluation device 10 via an operating unit (not shown) of the road surface evaluation device 10. Snowfall information is information that can be displayed on a display device such as a display, and a user (for example, a road management company) can check the road surface condition (snow accumulation) by displaying the snowfall information on the display of the user's terminal. The output unit 114 may also output snowfall information to the storage unit 120. For example, the snowfall information may be output so as to be mapped to map information stored in the storage unit 120.

[0033] Here, we will explain snowfall detection in detail. Figures 6A and 6B are examples of histograms showing the distribution of slip ratios in a predetermined section of a road under evaluation (hereinafter also referred to as the evaluation section), which has multiple lanes in one direction. The slip ratio is calculated by the calculation unit 112 for each position that a vehicle 20 traveling in the evaluation section passes at predetermined time intervals or predetermined distance intervals.

[0034] Figures 6A and 6B show the distribution of slip ratios calculated based on driving information obtained from vehicle 20 while it was traveling through the evaluation section. Characteristic P11 shows the distribution of slip ratios calculated based on driving information obtained during non-snowfall periods. Characteristic P12 shows the distribution of slip ratios calculated based on driving information obtained at the beginning of snowfall.

[0035] As shown in Figures 6A and 6B, the histogram for characteristic P12 (early snowfall) has a wider tail on the right side compared to the histogram for characteristic P11 (non-snowfall period). Specifically, characteristic P12 shows almost the same data distribution as characteristic P11 in the range below slip rate d11, while the data is distributed in the range beyond slip rate d11.

[0036] As described above, in the initial stages of snowfall, snow accumulated within the lanes melts due to friction with the wheels of moving vehicles and the pressure exerted by the wheels. Therefore, the characteristics P12 in the initial stages of snowfall show almost the same data distribution as the characteristics P11 in the non-snowfall period. However, near the lane boundary lines, snow accumulation progresses even in the initial stages of snowfall, so when vehicle 20 performs actions that cross the lane boundary lines (such as changing lanes), the wheels slip due to the snow accumulated near the lane boundary lines. As a result, as shown in Figure 6B, the histogram of characteristics P12 in the initial stages of snowfall shows data (outliers) that deviate from those of characteristics P11 in the non-snowfall period.

[0037] Therefore, the calculation unit 112 calculates the current slip ratio of the vehicle 20 based on the vehicle 20's current driving information. The calculation unit 112 also calculates the average slip ratio during non-snowy seasons (hereinafter referred to as the average slip ratio) based on past driving information, which corresponds to the vehicle 20's current driving position and is driving information from non-snowy seasons.

[0038] The determination unit 113 detects lane changes by the vehicle 20 in the evaluation section based on steering angle information included in the vehicle 20's current driving information, and acquires information including the result of the detection (hereinafter referred to as lane change information). The determination unit 113 determines that it has started snowing at the vehicle 20's driving position if the current slip ratio includes a value (outlier) that deviates from the average slip ratio by a predetermined amount or more, and the lane change information indicates that a lane change has occurred.

[0039] In this way, the determination unit 113 detects the initial stage of snowfall. The determination unit 113 determines that the current slip rate deviates from the average slip rate by a predetermined amount or more when the current slip rate is greater than a determination threshold based on the average slip rate. The determination threshold is a value obtained by multiplying the average slip rate by a predetermined multiplier. The determination threshold may be a fixed value.

[0040] Figure 7 is a flowchart showing an example of processing performed by the calculation unit 110 (CPU) of the road surface evaluation device 10 according to a predetermined program. The processing shown in this flowchart is repeated at predetermined intervals while the road surface evaluation device 10 is running. First, in step S11, it is determined whether or not an instruction to output snowfall information has been input (received).

[0041] If the result in step S11 is negative, the process is terminated. If the result in step S11 is positive, in step S12, road information included in the map information stored in the storage unit 120 is obtained. More specifically, information on the road to be evaluated is obtained based on the target road information included in the snowfall information output instruction. In step S13, vehicle 20 driving information is obtained from the storage device 40 via the communication unit 13. More specifically, driving information of the vehicle 20 traveling on the road to be evaluated is obtained based on the target road information included in the snowfall information output instruction. At this time, if there are multiple vehicles 20 traveling on the road to be evaluated, driving information corresponding to each of the multiple vehicles 20 is obtained.

[0042] In step S14, past driving information of the vehicle 20 is obtained from the storage device 40 via the communication unit 13. More specifically, driving information corresponding to the road under evaluation, and corresponding to past non-snowfall periods, is obtained. At this time, if there are multiple vehicles 20 that have driven on the road under evaluation during the non-snowfall period, driving information corresponding to each of the multiple vehicles 20 is obtained.

[0043] In step S15, the snowfall determination process is executed. Here, the process in step S15 will be explained in detail using Figure 8. Figure 8 is a flowchart detailing the snowfall determination process (the process in step S15 of Figure 7). The processes in steps S21 to S27 are executed for each predetermined section, more specifically, for each section of a predetermined length along the direction of travel of the road to be evaluated.

[0044] In step S21, the slip ratio of the wheels of the vehicle 20 traveling in the predetermined section (current slip ratio) is calculated based on the driving information acquired in step S13, i.e., the current driving information. If there are multiple vehicles 20 traveling in the predetermined section, the current slip ratio corresponding to each of the multiple vehicles 20 is calculated.

[0045] In step S22, based on the driving information acquired in step S14, i.e., driving information corresponding to past non-snowy seasons, the average value (average slip rate) of the wheel slip rate (past slip rate) of the vehicles 20 that traveled a predetermined section during non-snowy seasons is calculated. If there are multiple vehicles 20 that traveled a predetermined section during non-snowy seasons, the average slip rate is calculated based on the past slip rates corresponding to each of the multiple vehicles 20. In step S23, based on the average slip rate calculated in step S22, it is determined whether or not the slip rate calculated in step S21 contains outliers.

[0046] If the result in step S23 is positive, in step S24, it is determined whether the vehicle 20 traveling in the predetermined section is changing lanes, based on the current driving information obtained in step S13. If the result in step S24 is positive, in step S25, it is determined that it has started snowing in the predetermined section and that there is snowfall. On the other hand, if the result in step S23 or step S24 is negative, in step S26, it is determined that there is no snowfall in the predetermined section.

[0047] In step S27, it is determined whether there are any sections of the road under evaluation where snowfall determination (processing in steps S21 to S26) has not been performed, that is, whether snowfall determination has been completed for the entire road under evaluation. If the result in step S27 is negative, the process returns to step S21. On the other hand, if the result in step S27 is positive, the process ends.

[0048] Returning to the explanation of Figure 7, in step S16, after step S15, snowfall information is generated by associating the result of the snowfall determination process in step S15 with the road information obtained in step S12. In step S17, the snowfall information generated in step S16 is output. This allows the snowfall information to be displayed on a display device such as a screen, enabling the user to recognize whether or not there is snowfall on the road being evaluated and to evaluate the impact of snowfall on the road surface at an early stage.

[0049] Furthermore, in step S17, snowfall information may be mapped and output to map information including the road to be evaluated, as shown in Figure 5, so that the user can visually recognize the snowfall. More specifically, snowfall information may be mapped and output to map information so that the road to be evaluated is displayed in predetermined sections along the direction of travel, using a color corresponding to the snowfall judgment result (for example, no snowfall: white, early snowfall: pink). Furthermore, predetermined sections where the current slip ratio calculated in step S21 shows the characteristics when snowfall has progressed to a certain extent, that is, when snow has accumulated over the entire road surface (hereinafter referred to as the snowfall progression phase), may be displayed in a color corresponding to the snowfall progression phase (for example, red).

[0050] According to embodiments of the present invention, the following effects can be achieved. (1) The road surface evaluation device 10 includes an information acquisition unit 111 that acquires position information indicating the driving position of each of the multiple vehicles 20 traveling on the road, vehicle speed information indicating the driving speed corresponding to the driving position, wheel speed information indicating the rotation speed of the wheels, and lane change information indicating whether or not a lane change has occurred; a calculation unit 112 that calculates the current and past slip ratios of the wheels in a predetermined section of the road based on the vehicle speed information and wheel speed information acquired by the information acquisition unit 111; a determination unit 113 that determines whether or not snowfall has occurred in the predetermined section based on the slip ratio calculated by the calculation unit 112 and the lane change information; and an output unit 114 that outputs snowfall information including the determination result of the determination unit 113. The determination unit 113 determines that there is snowfall in the predetermined section when the current slip ratio includes a value that deviates by a predetermined amount or more from the average value of past slip ratios, and the lane change information indicates that a lane change has occurred. This allows for the detection of the initial stages of snowfall, enabling early assessment of the impact of snowfall on road surfaces, specifically the possibility of snow accumulation. As a result, users can take early action, such as dispatching snowplows.

[0051] (2) The information acquisition unit 111 acquires steering angle information, which indicates the steering angle of the steering wheel of each of the multiple vehicles 20. The information acquisition unit 111 further detects a lane change by any of the multiple vehicles 20 in a predetermined section based on the steering angle information, and acquires the result of the detection as lane change information. In this way, the initial stage of snowfall can be detected using existing sensors provided by the vehicles, and the device configuration can be simplified.

[0052] (3) The information acquisition unit 111, acting as a receiving unit, receives an output instruction for snowfall information specifying a road to be evaluated for snowfall, i.e., a road to be evaluated. The output unit 114 transmits the snowfall information to the terminal that sent the output instruction. This allows the user to specify any road to be evaluated and to recognize the possibility of snow accumulation on that road at an early stage.

[0053] (4) Snowfall information is information that can be displayed on a display device, and the output unit 114 outputs snowfall information to a display device such as a display. This allows the user to visually recognize the snowfall information.

[0054] The above embodiment can be modified into various forms. Modifications will be described below. In the above embodiment, the information acquisition unit 111 detects a lane change by any of the multiple vehicles 20 in a predetermined section (evaluation target section) based on the steering angle information of each of the multiple vehicles 20 traveling on the road, and acquires the result of the detection as lane change information. However, the information acquisition unit may also detect a lane change by any of the multiple vehicles 20 in a predetermined section by comparing the position information of each of the multiple vehicles 20 with road map information. Alternatively, the information acquisition unit may acquire turn signal information indicating the operation of the turn signals of each of the multiple vehicles 20, and detect a lane change by any of the multiple vehicles 20 in a predetermined section based on this turn signal information.

[0055] Furthermore, in the above embodiment, the information acquisition unit 111 acquires information (sensor values) indicating the steering angle of the steering wheel, which is acquired by the steering angle sensors 34 of each of the multiple vehicles 20 traveling on the road, as steering angle information. However, the information acquisition unit may also acquire information (sensor values) indicating the steering angle of the wheels, which is acquired by the steering angle sensors (not shown) of each of the multiple vehicles 20, as steering angle information.

[0056] Furthermore, in the above embodiment, the storage device 40 stores driving information of multiple vehicles 20, and the information acquisition unit 111 acquires driving information of multiple vehicles 20 corresponding to the road to be evaluated from the storage device 40 via the communication unit 13. However, the driving information of multiple vehicles 20 may also be stored in the storage unit 120 of the road surface evaluation device 10. In that case, the information acquisition unit reads and acquires the driving information of multiple vehicles 20 corresponding to the road to be evaluated from the storage unit 120.

[0057] Furthermore, in the above embodiment, the calculation unit 112 calculates the current and past slip ratios of the wheels based on the current and past driving information of the vehicle 20 (specifically, vehicle speed information and wheel speed information) acquired by the information acquisition unit 111. However, the information acquisition unit may acquire driving information of the vehicle 20 corresponding to a first predetermined time point in the past and a second predetermined time point in the past. The calculation unit may calculate the slip ratios of the wheels at the first predetermined time point and the second predetermined time point. The determination unit may determine that there was snowfall at the first predetermined time point in a predetermined section if the slip ratio at the first predetermined time point includes a value that deviates by a predetermined amount or more from the average value of the slip ratio at the second predetermined time point, and the driving information at the first predetermined time point (specifically, lane change information) indicates that a lane change occurred at the first predetermined time point. Furthermore, the output instruction for snowfall information may include information that can identify at least the first predetermined time point. With this configuration, the user can evaluate the possibility of snow accumulation on the road surface at any point in the past.

[0058] Furthermore, in the above embodiment, the example was given of a road with multiple lanes in one direction (Figures 6A, 6B). However, vehicles traveling on a road with one lane in one direction may sometimes exhibit behavior that crosses the shoulder line or center line. For example, when a vehicle turns right or left to enter a facility such as a shop located on the side of the road, its wheels may slip due to snow accumulated near the shoulder line or center line. Therefore, the road to be evaluated is not limited to a road with multiple lanes in one direction, but may also be a road with one lane in one direction.

[0059] Furthermore, in the above embodiment, the information acquisition unit 111 acquires map information, including information about the roads on which the vehicle 20 travels, from the storage unit 120. However, the information acquisition unit may acquire map information, including information about the roads on which the vehicle 20 travels, from an external server device or the like.

[0060] The above description is merely an example, and the present invention is not limited by the embodiments and modifications described above, as long as the features of the present invention are not impaired. It is also possible to arbitrarily combine one or more of the above embodiments and modifications, and to combine modifications with each other. [Explanation of symbols]

[0061] 10 Road surface evaluation device, 20, 20-1 to 20-n Vehicle, 30 In-vehicle terminal, 40 Driving information storage device, 110 Calculation unit, 111 Information acquisition unit, 112 Calculation unit, 113 Judgment unit, 114 Output unit, 120 Storage unit

Claims

1. An information acquisition unit acquires location information indicating the driving position of each of several vehicles traveling on a road, vehicle speed information indicating the driving speed corresponding to the driving position, wheel speed information indicating the rotation speed of the wheels, and lane change information indicating whether or not a lane change has been made. A calculation unit calculates the current and past slip ratios of the wheels in a predetermined section of the road based on the vehicle speed information and wheel speed information acquired by the information acquisition unit, A determination unit determines whether or not snowfall occurs in the predetermined section based on the slip ratio calculated by the calculation unit and the lane change information, The system includes an output unit that outputs snowfall information including the determination result of the determination unit, The road surface evaluation device is characterized in that the determination unit determines that there is snowfall in the predetermined section when the current slip ratio includes a value that deviates by a predetermined amount or more from the average value of the past slip ratios, and when the lane change information indicates that a lane change has occurred.

2. In the road surface evaluation device according to claim 1, The aforementioned information acquisition unit, The steering angle information indicating the steering angle of the steering wheel of each of the aforementioned multiple vehicles is acquired, and further, A road surface evaluation device characterized by detecting a lane change in a predetermined section by any of the plurality of vehicles based on the steering angle information, and acquiring the result of the detection as lane change information.

3. In the road surface evaluation device according to claim 1, The aforementioned information acquisition unit further acquires road map information, The road surface evaluation device is characterized in that the information acquisition unit compares the location information with the road map information to detect a lane change in the predetermined section by any of the multiple vehicles, and acquires the result of the detection as lane change information.

4. In the road surface evaluation device according to claim 1, The aforementioned information acquisition unit, The system acquires turn signal information indicating the operation of the turn signals of each of the aforementioned multiple vehicles, and further, A road surface evaluation device characterized by detecting a lane change in a predetermined section by any of the multiple vehicles based on the turn signal information, and acquiring the result of the detection as lane change information.

5. In the road surface evaluation device according to any one of claims 1 to 4, The system further comprises a receiving unit that receives an output instruction for snowfall information, which specifies the road to be used for determining whether or not snowfall is occurring, The road surface evaluation device is characterized in that the output unit transmits the snowfall information to the terminal that sent the output instruction.

6. In the road surface evaluation device according to any one of claims 1 to 4, The aforementioned snowfall information is information that can be displayed on a display device. The road surface evaluation device is characterized in that the output unit outputs the snowfall information to the display device.

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