roadside machine

Abstract

To extend the life of the sensor part of roadside units. [Solution] The roadside system is configured by installing a plurality of roadside units 3 along a road, each equipped with a sensor unit 31 and a communication unit 330. The roadside unit 3 is equipped with an activation control unit 353 that switches the sensor unit 31 to an activated state when a vehicle approach notification is received from a roadside unit 3 on an upstream side of the road, an approach notification control unit 355 that transmits a vehicle approach notification to a roadside unit 3 on a downstream side of the road when the sensor unit 31 detects a vehicle within a detection target area, and a sleep control unit 357 that switches the sensor unit 31 to a sleep state when it is determined that the vehicle has left the detection target area based on the detection result of the sensor unit 31.

Description

[Technical Field]

[0001] The present invention relates to a roadside unit. [Background technology]

[0002] Conventionally, there has been known a technology in which roadside units are installed along roads to monitor vehicles traveling in the vicinity, pedestrians, obstacles, etc. For example, Patent Document 1 discloses a technology in which a roadside unit is equipped with a sensor such as a LiDAR (Light Detection and Ranging) or a camera to detect objects within a detection area. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2024-158562 Summary of the Invention [Problem to be solved by the invention]

[0004] To ensure the safety of pedestrians, it is necessary to constantly monitor vehicles within the detection area. However, constant monitoring shortens the lifespan of the sensor and increases the cost of maintenance. This problem can arise especially when using relatively expensive sensors such as LiDAR.

[0005] The problem to be solved by the present invention is to provide a technology that can extend the life of a sensor unit in a roadside unit. [Means for solving the problem]

[0006] The first invention to solve the above problem is: A roadside unit of a roadside system in which a plurality of roadside units, each having a sensor unit and a communication unit, are installed along a road, an activation control means (for example, the activation control unit 353 in FIG. 6) that activates the sensor unit when a vehicle approach notification is received from a roadside device on the upstream side of the road; a first sleep control means (for example, a sleep control unit 357 in FIG. 6) that puts the sensor unit into a sleep state when it is determined that the vehicle has left the detection target area based on the detection result of the sensor unit; It is a roadside unit equipped with

[0007] According to the first aspect of the present invention, the sensor unit can be activated in response to a vehicle approach notification from an upstream roadside unit, and can be put into a sleep state when the vehicle leaves the detection target area. This makes it possible to monitor vehicles within the detection target area while shortening the operating time of the sensor unit and achieving a longer lifespan for the sensor unit.

[0008] The second invention is the above invention, an approach notification control means for transmitting the vehicle approach notification to a roadside device on a downstream side of the road when the sensor unit detects a vehicle within the detection target area; The roadside unit further comprises:

[0009] According to the second aspect of the present invention, in response to detection of a vehicle within a detection target area, a vehicle approach notification can be transmitted to a downstream roadside device.

[0010] The third invention is the above invention, The roadside unit is installed near an intersection, the approach notification control means transmits the vehicle approach notification to a roadside device downstream of the route from which the vehicle is to enter based on the detection result of the sensor unit. It is a roadside unit.

[0011] According to the third aspect of the present invention, a vehicle approach notification can be transmitted to a roadside device downstream of the installed roadside device based on the route of the vehicle exiting the vicinity of the intersection where the vehicle is installed.

[0012] A fourth invention is the above invention, a second sleep control means for putting the sensor unit into a sleep state when receiving an approach notification from a roadside device on a downstream side of the road; an entry notification control means for transmitting an entry notification to the upstream roadside device when the sensor unit detects that a vehicle has entered the detection target area; The roadside unit further comprises:

[0013] According to the fourth aspect of the present invention, when the sensor unit detects a vehicle entering a detection target area, it can transmit an entry notification to an upstream roadside device, and when it receives an entry notification from a downstream roadside device, it can put the sensor unit into a sleep state.

[0014] The fifth invention is A roadside unit of a roadside system in which a plurality of roadside units, each having a sensor unit and a communication unit, are installed along a road, an activation control means for activating the sensor unit when a vehicle approach notification is received from a roadside device on the upstream side of the road; a sleep control means for putting the sensor unit into a sleep state when receiving an approach notification from a roadside device on a downstream side of the road; It is a roadside unit equipped with

[0015] According to the fifth aspect of the present invention, the sensor unit can be activated in response to a vehicle approach notification from an upstream roadside device, and can be put into a sleep state in response to an entry notification from a downstream roadside device. This makes it possible to monitor vehicles within the detection area while shortening the operating time of the sensor unit and achieving a longer lifespan for the sensor unit.

[0016] The sixth invention is the above invention, an entry notification control means for transmitting the entry notification to the upstream roadside device when the sensor unit detects that a vehicle has entered the detection target area; The roadside unit further comprises:

[0017] According to the sixth aspect of the present invention, in response to detection of a vehicle entering a detection target area, an entry notification can be transmitted to an upstream roadside unit.

[0018] A seventh aspect of the present invention is the above-mentioned invention, a start-up control disabling unit (e.g., the start-up control disabling unit 359 in FIG. 6) that disables the start-up control unit and keeps the sensor unit in a constantly activated state when the roadside unit is a base end roadside unit installed at the most upstream of the road among the plurality of roadside units; The roadside unit further comprises:

[0019] According to the seventh aspect of the present invention, the sensor unit of the base end roadside unit installed at the most upstream of the road can be kept in a constantly activated state. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a roadside system. [Figure 2] FIG. 2 is a diagram for explaining a base end roadside unit. [Figure 3] FIG. 2 is a diagram for explaining switching control between an active state and a sleep state in a roadside device. [Figure 4] FIG. 10 is another diagram for explaining the control of switching between the wake-up state and the sleep state in the roadside device. [Figure 5] FIG. 10 is another diagram for explaining the control of switching between the wake-up state and the sleep state in the roadside device. [Figure 6] FIG. 2 is a block diagram showing an example of the functional configuration of a roadside unit. [Figure 7] FIG. 10 is a diagram showing an example of the data configuration of an adjacent roadside unit table; [Figure 8] 10 is a flowchart showing the flow of processing performed by a roadside device. [Figure 9] 10A and 10B are diagrams for explaining a modified example of switching control between an active state and a sleep state in a roadside device. [Figure 10] 10 is another diagram for explaining a modified example of the control of switching between the wake-up state and the sleep state in the roadside device. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments described below, and the forms to which the present invention can be applied are not limited to the following embodiments. In addition, in the description of the drawings, the same parts are given the same reference numerals.

[0022] Fig. 1 is a diagram showing an example of a roadside system 1 to which a roadside unit 3 according to this embodiment is applied, in a bird's-eye view. Fig. 1 shows an example of the system configuration of the roadside system 1, which includes a plurality of roadside units 3 installed along roads and a center device 5, and in which the roadside units 3 and the center device 5 are connected via a network N. In this embodiment, a roadside unit 3 is installed near each intersection.

[0023] The network N refers to a communication path that allows data communication. That is, the network N includes a dedicated line (dedicated cable) for direct connection, a LAN (Local Area Network) using Ethernet (registered trademark), etc., as well as a communication network such as a telephone communication network, a cable network, or the Internet, and the communication method can be either wired or wireless.

[0024] The roadside device 3 performs road-to-vehicle communication with the vehicle 10 equipped with an on-board communication device, and provides traffic information and the like related to the target intersection where the roadside device 3 is installed (hereinafter also referred to as "target intersection") I. For example, under the instruction of the center device 5, the roadside device 3 provides, as needed, to the vehicle 10 that is planning to enter the target intersection, information on the traffic lights at the target intersection as well as information on the positions of vehicles and people in the vicinity (hereinafter referred to as "information for passing vehicles").

[0025] In this embodiment, the roadside device 3 includes a sensor unit 31 including a laser sensor such as LiDAR, and detects objects such as vehicles, people, and bicycles that exist in a detection target area that includes a target intersection.

[0026] The sensor unit 31 acquires point cloud data by receiving reflected waves of laser irradiation from a predetermined installed position. For example, the sensor unit 31 measures the reflection position based on the distance calculated from the time until the reflected wave is received (ToF: Time of Flight) and the irradiation direction, and acquires the point cloud data as three-dimensional coordinates. The acquisition of point cloud data is repeated at a predetermined acquisition cycle.

[0027] The roadside device 3 analyzes the point cloud data acquired by the sensor unit 31, detects and identifies vehicles and people present in the detection target area (target intersection), and acquires their positions. The positions of vehicles and people within the detection target area obtained as a result of the analysis are transmitted to the center device 5 as needed.

[0028] [detail] In a configuration in which the sensor unit 31 is always activated, point cloud data is repeatedly acquired at a predetermined acquisition cycle regardless of the presence or absence of vehicles or people in the detection target area, which shortens the life of the sensor unit 31. Therefore, the roadside unit 3 controls the sensor unit 31 to switch between an activated state and a sleep state.

[0029] More specifically, the roadside units 3 include a base roadside unit in which the sensor unit 31 is always activated, and in roadside units 3 other than the base roadside unit, the sensor unit 31 can be switched between an activated state and a sleep state. Among the roadside units 3, the roadside unit 3 installed at the most upstream of a road is considered to be the base roadside unit. FIG. 2 is a diagram for explaining the base roadside units, showing an example of installation of roadside units 3 installed at intersections of a grid-like road. Note that FIG. 2 does not illustrate the sensor unit 31 equipped in each roadside unit 3. In this embodiment, a route to be used as the base roadside unit is determined in advance, and the roadside units 3 installed at intersections of that route are considered to be the base roadside units. In FIG. 2, when routes R11, R12, R13, and R14 indicated by thick lines are determined to be routes for base roadside units, the hatched roadside units 3 are considered to be the base roadside units. For example, in the road portion of route R2 shown in Fig. 2 surrounded by a dashed line, if one focuses on the lane running from west to east, the road-side unit 3a installed at the most upstream position is the base road-side unit and is always activated. If one focuses on the lane running from east to west on the road portion of route R2, the road-side unit 3d installed at the most upstream position is the base road-side unit and is always activated. There are no particular restrictions on which route is set as the base road-side unit, but it can be set to a route with heavy traffic, such as a national highway or a prefectural road.

[0030] 3 to 5 are diagrams for explaining the switching control between the wake-up state and the sleep state in the roadside unit 3, and each diagram shows the road portion of route R2 surrounded by the dashed line in Fig. 2. In the switching control, when the roadside unit 3 detects a vehicle in the detection target area as a result of analyzing the point cloud data from the sensor unit 31, it determines the exit route of the vehicle at the target intersection.

[0031] As described above, the base roadside units are always activated. Therefore, if a vehicle is present in the detection area of ​​the sensor unit 31, the position of the vehicle is detected at each acquisition cycle. The exit route can be determined from the direction of movement of the vehicle within the detection area. In the example of FIG. 3, the roadside units 3a and 3d are base roadside units. For example, if the roadside unit 3a detects the vehicle 10a based on the point cloud data from its sensor unit 31, it determines the exit route of the vehicle. If the vehicle 10a is moving in the direction indicated by arrow A21 in FIG. 3, it determines the exit route as heading east on route R2 at the target intersection Ia. Similarly, if the roadside unit 3d detects the vehicle 10b based on the point cloud data from its sensor unit 31, it determines the exit route as heading south on route R14 at the target intersection.

[0032] Once the exit route has been determined, the roadside unit 3 transmits a vehicle approaching notification to the roadside unit 3 downstream of the exit route. In the example of Figure 3, if the roadside unit 3a detects the vehicle 10a and determines that the route R2 heading east is the exit route, the roadside unit 3a transmits a vehicle approaching notification to the roadside unit 3b downstream of the exit route. In this case, the roadside unit 3b receives the vehicle approaching notification from the roadside unit 3a upstream of the road.

[0033] Here, the roadside unit 3a is a base roadside unit and is always in an activated state, so it continues to analyze the point cloud data from the sensor unit 31 at each acquisition cycle to detect vehicles and people within the detection area. When a new vehicle is detected, it determines the exit route in the same manner as above and transmits a vehicle approach notification to the downstream roadside unit 3.

[0034] On the other hand, when the roadside device 3b receives a vehicle approach notification from the roadside device 3a, it switches the sensor unit 31 to an active state if it is in a sleep state. In this embodiment, the sleep state refers to a state in which the power to the sensor unit 31 is cut off (OFF). Therefore, here, if the power to the sensor unit 31 is OFF, it is turned on (ON). Note that the sleep state may also be a pause state in which the operation of the sensor unit 31 is temporarily stopped while the power remains ON. In this case, the roadside device 3 (here, roadside device 3b) cancels the pause state and transitions the sensor unit 31 from the sleep state to the active state.

[0035] As a result, the roadside device 3b starts detecting vehicles and people based on the detection results of the sensor unit 31. That is, the roadside device 3b analyzes the point cloud data from the sensor unit 31 to detect vehicles and people within the detection target area. When the roadside device 3b detects the vehicle 10a, it determines the exit route in the same manner as above. When the vehicle 10a is moving in the direction indicated by the arrow A25 in FIG. 4, it determines that the exit route is the route heading east on route R2 at the target intersection Ib, and transmits a vehicle approach notification to the roadside device 3c downstream of the exit route.

[0036] Here, the roadside unit 3b is not a base roadside unit. Therefore, after transmitting the vehicle approach notification, the roadside unit 3b monitors the departure of the vehicle 10a from the detection target area based on the detection result of the sensor unit 31. The roadside unit 3b determines that the vehicle has left the detection target area when the vehicle 10a is no longer present in the detection target area. In this case, the roadside unit 3b controls the sensor unit 31 to transition from the active state to the sleep state, as shown in FIG. 5. In this embodiment, the power supply of the sensor unit 31 is turned off. This causes the sensor unit 31 to enter the sleep state.

[0037] After that, although not shown, when the roadside device 3c receives a vehicle approach notification from the roadside device 3b, it switches the sensor unit 31, if it is in a sleep state, to an active state. In this embodiment, the power supply for the sensor unit 31 is turned on. Then, when the roadside device 3c detects the vehicle 10a based on the detection result of the sensor unit 31, it determines the vehicle's exit route and transmits a vehicle approach notification to the roadside device 3 downstream of the exit route. For example, if the vehicle 10a continues to travel straight on route R2, the roadside device 3c transmits a vehicle approach notification to the roadside device 10d. Furthermore, when the vehicle 10a leaves the detection target area, the roadside device 3c controls the sensor unit 31 to transition from the active state to the sleep state. In this embodiment, the power supply for the sensor unit 31 is turned off. The sensor units 31 are switched to the active state in the order of the roadside devices 3b and 3c, as if they are being turned on / off in a chain reaction in advance of the movement of the vehicle 10a, and the sensor unit 31 is switched to the sleep state when the vehicle 10a leaves the detection target area being monitored.

[0038] [Function Configuration] Fig. 6 is a block diagram showing an example of the functional configuration of the roadside unit 3. As shown in Fig. 6, the roadside unit 3 includes a sensor unit 31, an operation unit 310, a display unit 320, a communication unit 330, a processing unit 350, and a storage unit 370, and is configured as a type of computer system.

[0039] The operation unit 310 is realized by an input device such as a button switch or a touch panel, and outputs an operation signal according to the operation input to the processing unit 350. The display unit 320 is realized by a display device such as an LCD (Liquid Crystal Display) or a touch panel, and performs various displays according to the display signal from the processing unit 350. The communication unit 330 is realized by a wired or wireless communication device, and communicates with predetermined external devices (for example, the center device 5 or other roadside devices 3).

[0040] The processing unit 350 is realized by, for example, an arithmetic circuit such as a CPU (Central Processing Unit) or a control board including the arithmetic circuit, and controls the operation of the roadside unit 3 by performing various arithmetic processes based on programs, data, etc. stored in the storage unit 370. In this embodiment, the processing unit 350 includes an analysis unit 351, a startup control unit 353, an approach notification control unit 355, a sleep control unit 357, and a startup control disabling unit 359. Each of these functional units may be an arithmetic processing block realized as software by executing a program, or may be a circuit block realized by a signal processing circuit. In this embodiment, the processing unit 350 will be described as an arithmetic processing block realized as software by executing a predetermined program.

[0041] The analysis unit 351 analyzes the detection results (point cloud data of the detection target area obtained at an acquisition period) of the sensor unit 31 and acquires the positions of vehicles, people, bicycles, etc. present in the detection target area. The analysis unit 351 also acquires traffic light information of the target intersection from the center device 5 via the communication unit 330. Then, based on the acquired various pieces of information, it generates information for passing vehicles and transmits it to vehicles that are present in the detection target area and are capable of communicating with the roadside unit 3.

[0042] The activation control unit 353 performs control to activate the sensor unit 31 when a vehicle approach notification is received from a roadside unit 3 on the upstream side of the road.

[0043] When the analysis unit 351 detects a vehicle in the detection target area based on the detection result of the sensor unit 31, the approaching notification control unit 355 transmits a vehicle approaching notification to a roadside unit 3 on the downstream side of the road. In this embodiment, a roadside unit 3 is installed at each intersection. Therefore, the approaching notification control unit 355 determines the exit route of the vehicle at the target intersection from the position of the vehicle detected at any time by the analysis unit 351. Then, the approaching notification control unit 355 transmits the vehicle approaching notification to a roadside unit 3 on the downstream side of the determined exit route. The destination roadside unit 3 is identified by referring to the adjacent roadside unit table 373.

[0044] The adjacent roadside device table 373 is set for the own device (the roadside device 3 in which the adjacent roadside device table 373 is stored). Fig. 7 is a diagram showing an example of the data configuration of the adjacent roadside device table 373. As shown in Fig. 7, the adjacent roadside device table 373 stores, for each direction of the target intersection of the own device, the device ID of the roadside device (adjacent roadside device) 3 installed at an intersection adjacent to the target intersection on that direction of the road.

[0045] The sleep control unit 357 monitors the vehicle's departure from the detection target area based on the vehicle's position detected by the analysis unit 351 at any time, and controls the sensor unit 31 to enter a sleep state when it determines that the vehicle has left the detection target area.

[0046] If the own device is a base end roadside device, the activation control disabling unit 359 disables the activation control unit 353 and controls the sensor unit 31 to be always activated. In this embodiment, a roadside device 3 installed on a predetermined route is considered to be a base end roadside device. Whether the own device is a base end roadside device or not is determined in advance in the base end roadside device information 371, with "ON" if the own device is a base end roadside device and "OFF" if the own device is not a base end roadside device.

[0047] The storage unit 370 is realized by a storage medium such as an IC memory or a hard disk. The storage unit 370 stores in advance or temporarily stores each time processing is performed programs for operating the roadside unit 3 and realizing various functions of the roadside unit 3, and data used during execution of the programs. In this embodiment, the storage unit 370 stores base end roadside unit information 371 and an adjacent roadside unit table 373 (see FIG. 7).

[0048] [Processing flow] 8 is a flowchart showing the flow of processing in the roadside device 3. In this processing, when a vehicle approach notification is received from a roadside device 3 on the upstream side of the road (step S1: YES), and if the roadside device is a base roadside device (step S3: YES), the activation control disabling unit 359 disables the activation control unit 353 (step S5). This causes the sensor unit 31 to be in a constantly activated state. On the other hand, if the roadside device is not a base roadside device (step S3: NO), the activation control unit 353 activates the sensor unit 31 (step S7).

[0049] Next, when a vehicle is detected in the detection target area as a result of the analysis by the analysis unit 351 (step S9: YES), the approach notification control unit 355 determines the exit route of the vehicle at the target intersection (step S11). Then, the approach notification control unit 355 reads out the device ID of the roadside unit 3 downstream of the exit route determined in step S11 from the adjacent roadside unit table 373, and performs control to transmit a vehicle approach notification to the corresponding roadside unit 3 (step S13).

[0050] Thereafter, if the device is not a base end roadside device (step S15: NO), the sleep control unit 357 determines whether the vehicle has left the detection target area based on the vehicle position detected by the analysis unit 351. Then, if the sleep control unit 357 determines that the vehicle has left (step S17: YES), it puts the sensor unit 31 into a sleep state (step S19).

[0051] As described above, according to this embodiment, the roadside unit 3 designated as the base roadside unit keeps the sensor unit 31 in a constantly active state, while the roadside units 3 other than the base roadside unit can activate the sensor unit 31 and then switch to a sleep state as needed. For example, a roadside unit 3 installed on a route with relatively heavy traffic can be designated as the base roadside unit, and the other roadside units 3 can be subject to switching control. Specifically, when the roadside unit 3 receives a vehicle approach notification from a roadside unit 3 upstream on the road, the corresponding roadside unit 3 activates the sensor unit 31. When the roadside unit 3 detects a vehicle within the detection target area, it determines the exit route at the target intersection and transmits the vehicle approach notification to roadside units 3 downstream of the determined exit route. Furthermore, when the vehicle exits the detection target area, the roadside unit 3 switches the sensor unit 31 to a sleep state. This shortens the operating time of the sensor unit 31 of roadside units 3 other than the base roadside unit, thereby extending the life of the sensor unit 31.

[0052] The forms to which the present invention can be applied are not limited to the above-described embodiments, and constituent elements can be added, omitted, or modified as appropriate.

[0053] [Variation 1] For example, in the above embodiment, an example has been described in which the roadside device 3 puts the sensor unit 31 into a sleep state when a vehicle leaves the detection target area. However, a configuration may be adopted in which the roadside device 3 waits for an entry notification from a roadside device 3 downstream on the road before transitioning to the sleep state. In this modification, when the roadside device 3 detects a vehicle that has newly entered the detection target area based on the point cloud data from the sensor unit 31, the roadside device 3 performs control as an entry notification control means to send an entry notification to the upstream roadside device 3.

[0054] 9 and 10 are diagrams for explaining the switching control between the wake-up state and the sleep state in this modification, and Fig. 9 shows a scene in which the roadside unit 3b transmits a vehicle approaching notification to the roadside unit 3c downstream of the exit route of the vehicle 10a. In this modification, after transmitting the vehicle approaching notification, the roadside unit 3b waits for an entry notification from the downstream roadside unit 3c.

[0055] In the same manner as in the above embodiment, the roadside device 3c activates the sensor unit 31 upon receiving a vehicle approach notification from the upstream roadside device 3b. Then, as shown in FIG. 10, when the roadside device 3c detects a vehicle 10a that has entered the detection target area, it transmits an entry notification to the upstream roadside device 3b. More specifically, when the roadside device 3c detects a new vehicle 10 (here, vehicle 10a), it determines the entry route of the vehicle 10a at the target intersection Ic, identifies the destination roadside device 3b, and transmits the entry notification. When the roadside device 3b receives an entry notification from the downstream roadside device 3c, it switches the sensor unit 31 to a sleep state as second sleep control means.

[0056] Furthermore, the configuration of the above embodiment may be configured to further perform control to put the sensor unit 31 into a sleep state in response to an entry notification from a roadside unit 3 on the downstream side of the road. In this case, when a vehicle 10a that has entered the detection target area is detected, control is performed to transmit an entry notification to the roadside unit on the upstream side.

[0057] [Variation 2] Alternatively, the roadside units 3 may be configured to switch between the awake state and the sleep state only during nighttime hours. In this case, all the roadside units 3 can be kept in the awake state at all times except during preset nighttime hours.

[0058] [Variation 3] In the above embodiment, the roadside system 1 is exemplified in which the roadside unit 3 is installed at each intersection, but there is no particular limitation on the installation locations of the roadside units 3. The present invention can be similarly applied to a roadside system in which multiple roadside units 3 are installed at arbitrary locations along a road. [Explanation of symbols]

[0059] 1. Roadside systems 3…Roadside machine 31...Sensor section 330…Communications Department 350...Processing section 351…Analysis Department 353...Start control unit 355...Approach notification control unit 357...Sleep control unit 359...Startup control disable unit 370...Storage section 371… Base end roadside machine information 373...Adjacent roadside unit table 5...Central device N...Network 10...Vehicle I…Intersection

Claims

1. A roadside unit of a roadside system in which a plurality of roadside units, each having a sensor unit and a communication unit, are installed along a road, an activation control means for activating the sensor unit when a vehicle approach notification is received from a roadside device on the upstream side of the road; a first sleep control means for putting the sensor unit into a sleep state when it is determined that the vehicle has left the detection target area based on the detection result of the sensor unit; A roadside unit comprising:

2. an approach notification control means for transmitting the vehicle approach notification to a roadside device downstream of the road when the sensor unit detects a vehicle within the detection target area; The roadside device according to claim 1 , further comprising:

3. The roadside unit is installed near an intersection, the approach notification control means transmits the vehicle approach notification to a roadside device downstream of the route from which the vehicle is to enter based on the detection result of the sensor unit. The roadside unit according to claim 2.

4. a second sleep control means for putting the sensor unit into a sleep state when receiving an approach notification from a roadside device on a downstream side of the road; an entry notification control means for transmitting an entry notification to the upstream roadside device when the sensor unit detects that a vehicle has entered the detection target area; The roadside device according to claim 1 , further comprising:

5. A roadside unit of a roadside system in which a plurality of roadside units, each having a sensor unit and a communication unit, are installed along a road, an activation control means for activating the sensor unit when a vehicle approach notification is received from a roadside device on the upstream side of the road; a sleep control means for putting the sensor unit into a sleep state when receiving an approach notification from a roadside device on a downstream side of the road; A roadside unit comprising:

6. an entry notification control means for transmitting the entry notification to the upstream roadside device when the sensor unit detects that a vehicle has entered a detection target area; The roadside device according to claim 5 , further comprising:

7. a start-up control disabling means for disabling the start-up control means and keeping the sensor unit in a constantly activated state when the roadside unit is a base end roadside unit installed at the most upstream of the road among the plurality of roadside units; The roadside device according to any one of claims 1 to 6, further comprising:

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