Driver assistance device

Abstract

Driving assistance device (15) installed in a vehicle and performing driving assistance for the vehicle, the driving assistance device comprising: a first determination device (S132, S159) that determines a recommended lane for the vehicle to travel in based on a comparison between a predetermined vehicle speed to enable the vehicle to travel at a constant speed, a driving condition of a vehicle ahead of the vehicle in a lane in which the vehicle is traveling, and a driving condition of a neighboring vehicle ahead of the vehicle in a neighboring lane adjacent to the lane;and an output device (S133, S145, S155, S163, S255, S265, S300) that performs an output based on the recommended lane, characterized in that the output device (S145) performs an output to allow the own vehicle to travel at a lane-change speed equal to or higher than the pre-set vehicle speed until the lane change to the adjacent lane is completed, when the first determination device determines that the recommended lane is the adjacent lane (S132), and the speed of the adjacent vehicle is higher than the pre-set vehicle speed (JA in S135).

Description

[Technical Field]The present invention relates to a technology that is mounted in a vehicle and performs driving assistance for the vehicle.[Prior Art]Conventionally, a technology that is mountable in a vehicle and performs various kinds of driving assistance for the vehicle is known. In JP H06-8 747 A, a technology is proposed in which, while a vehicle is running at constant speed, a predetermined vehicle speed set so that the vehicle can run at the constant speed is corrected to a higher side and increased if an intention of the driver of the vehicle to change lanes is confirmed. As a result, a lane change is carried out temporally matching the traffic flow or floating therewith.DE 10 2013 021 337 A1 discloses a driver assistance device according to the preamble of claims 1 and 2 and a method according to the preamble of claims 14 and 15.[Brief Explanation of the Invention][Technical Problem]However, in the conventional technique described in JP H06-8 747 A, the driver of an own vehicle itself needs to determine the lane in which the own vehicle is to travel.The inventors of the present invention have studied technologies that allow a driving assistance device to determine, instead of the driver of the own vehicle, the lane in which the own vehicle is to travel. As a result, the inventors have found that, in order to determine the lane in which the own vehicle is to travel, when changing lanes, it is not sufficient to take into account only the state of the own lane and the state of an adjacent lane.It is therefore an object of the invention to provide an apparatus capable of appropriately determining a lane in which an own vehicle is to travel without a driver of the own vehicle itself making the determination.[Solution of Object]One aspect of the present invention is a driving assistance apparatus having the features recited in claim 1 or 2. Advantageous refinements are the subject matter of the dependent claims. A further aspect relates to a corresponding method having the features listed in claim 14 or 15.As a result of such a configuration, the recommended lane is determined based on the predetermined vehicle speed, the traveling state of the preceding vehicle, and the traveling state of the adjacent vehicle. Therefore, the lane in which the own vehicle is to travel can be determined appropriately without the driver of the own vehicle making the determination by himself.Reference numerals within the brackets recited in the claims indicate corresponding relationships to specific devices in embodiments described below as an aspect, and do not limit the technical scope of the present invention.[Brief Explanation of Figures]FIG. 1 is a block diagram showing a configuration of a driving assistance system; FIG. 2 is a flowchart (1 / 2) of a tracking operation according to a first embodiment; FIG. 3 is a flowchart (2 / 2) of the tracking operation according to the first embodiment; FIG. 4 is a diagram of an example in which a preceding vehicle is followed; FIG. 5A is a diagram of an example of the behavior of an own vehicle when a neighboring vehicle travels at 100 km / h; FIG. 5B is a diagram of an example of the behavior of the own vehicle when the adjacent vehicle travels at 105 km / h; FIG. 5C is a diagram of an example of the behavior of the own vehicle when a speed difference between a predetermined vehicle speed and the vehicle speed is the same for the preceding vehicle and the adjacent vehicle, and the speed of the adjacent vehicle is higher than the predetermined vehicle speed; FIG. 6 is a diagram of an example of the behavior of the own vehicle when a space having the size required for the lane change is present in front of the overtaking preceding vehicle; FIG. 7 is a diagram of an example of the behavior of the own vehicle when the space having the size required for the lane change is not present in front of the overtaking preceding vehicle; FIG. 8 is a diagram of an example of the behavior of the own vehicle in a variation example; FIG. 9 is a flowchart (1 / 2) of a tracking operation according to a second embodiment; FIG. 10 is a flowchart (2 / 2) of the tracking operation according to the second embodiment; FIG. 11 is a flow chart of a track selection process according to a third embodiment; FIG. 12 is a flowchart (1 / 2) of a lane change operation according to the third embodiment; FIG. 13 is a flowchart (2 / 2) of the lane change operation according to the third embodiment; FIG. 14 is a flow chart (1 / 2) of a track return operation according to the third embodiment; and FIG. 15 is a flow chart (1 / 2) of the track return operation according to the third embodiment.[Description of Embodiments]Embodiments in which the present invention is applied will be described below with reference to the figures.[1. First Embodiment][1-1. Constitution]A driving assistance system 1 shown in FIG. 1 is a system mounted on a vehicle (own vehicle). The driving assistance system 1 includes a target detection device 11, a position detection device 12, a constant speed switch 13, a driving assistance execution device 14, and a control device 15.The target detection device 11 is a device that detects various kinds of targets existing in the surroundings of the own vehicle in which the driving assistance system 1 is mounted. For example, the target detection device 11 includes an image sensor 111, a radar sensor 112, and a vehicle speed sensor 113.The image sensor 111 captures an image of an area in front of the vehicle and captures image data. The image sensor 111 then performs image processing on the captured image data, thereby capturing a target present in a predetermined imaging range. The image sensor 111 then outputs the detection result to the control device 15.The radar sensor 112 transmits radio waves in front of the vehicle. Then, based on reception results of reflected waves from a target positioned in front of the vehicle, the radar sensor 112 detects at least a distance between the own vehicle and the target and a relative speed of the own vehicle relative to the target. The radar sensor 112 then outputs the detection result to the control device 15. A millimeter wave radar or laser radar (not shown) may be provided as the radar sensor 112.The image sensor 111 and the radar sensor 112 need only be capable of detecting at least one target required for a tracking operation (described below) by the control device 15. According to the present embodiment, the image sensor 111 and the radar sensor 112 detect at least a preceding vehicle and an adjacent vehicle. The preceding vehicle refers to a vehicle that travels in a lane in front of the own vehicle (a vehicle that travels directly in front of the own vehicle). The driving lane refers to the driving lane on which the own vehicle travels. The adjacent vehicle refers to a vehicle that travels in front of the own vehicle on an adjacent lane adjacent to the driving lane.The vehicle speed sensor 113 is a known vehicle speed sensor that detects a rotational speed of an axle of the own vehicle and calculates a speed of the own vehicle based on the detected rotational speed. The vehicle speed sensor 113 then outputs the calculated vehicle speed to the control device 15.The position detection device 12 is a device that detects a current position of the own vehicle. For example, the position detection device 12 includes a position detector 121 and a map data recording unit 122.The position detector 121 includes a global positioning system (GPS) receiver, a gyroscope, and an odometer (each not shown). The GPS receiver receives transmission signals from artificial satellites for GPS and recognizes position coordinates and a geographical height of the own vehicle. The gyroscope outputs a detection signal based on an angular velocity of a rotational motion acting on the own vehicle. The distance sensor outputs a travel distance of the own vehicle. The position detector 121 calculates the current position of the own vehicle based on the signals output from the sensors, and outputs the calculation result to the controller 15.The map data recording unit 122 is a recording unit in which map data that represents a map is recorded. As information related to roads that the vehicle can travel, the map data includes information indicating road types (freeways, expressways, other general roads, and the like), information indicating curved roads, and the like, and information indicating whether a road allows lane changes.The constant speed running cruise switch 13 is a switch for detecting an instruction from the driver of the own vehicle to perform constant speed running control. The cruise control refers to the control performed to allow the own vehicle to travel at a predetermined vehicle speed. The predetermined vehicle speed refers to a vehicle speed that the driver of the own vehicle sets in advance. Hereinafter, a state in which the instruction from the driver of the own vehicle to perform constant speed running is detected by the cruise control switch 13 will be referred to as a cruise control running mode.The driving assistance execution device 14 includes a plurality of devices that control the behavior of control objects in a body system, a powertrain system, and a chassis system of the vehicle. The control items may include at least a steering device (such as an electric power steering) 141, an engine 142, a speaker 143, a display 144, a braking device such as brakes (not shown), an accelerator driving device, and the like.According to the present embodiment, the display 144 is a touch panel display capable of receiving input from the driver of the own vehicle. In addition, the devices constituting the driving assistance execution device 14 may be devices that execute known vehicle control such as steering control, engine control, cruise control, and various types of warning controls such as speed warning, collision warning, and vehicle mutual warning by controlling the behaviors of the control objects based on the traveling state of the vehicle and controlling the behaviors of the control objects based on commands from the control device 15.The control device 15 is an electronic control unit including a central processing unit (CPU) 51, a read only memory (ROM) 52, a random access memory (RAM) 53, and the like. The control device 15 performs integrated control of the driving assistance system 1 by the CPU 51 performing various operations based on programs recorded on a recording medium such as the ROM 52. For example, the CPU 51 executes operations to output instructions for the various types of vehicle control described above. In addition, the CPU 51 performs a tracking operation in parallel with these operations to allow the own vehicle to track a vehicle traveling in front of the own vehicle.An external recording device 16 is a rewritable recording device such as a flash ROM. The external recording device 16 records the preset vehicle speed for the cruise control described above, a change amount upper limit value described below, and the like.[1-2. Operations]Next, the following operation performed by the control device 15 (CPU 51) will be described with reference to the flowcharts in FIGS. 2 and 3. The process shown in FIGS. 2 and 3 is repeatedly performed while the own vehicle is traveling on a road on which lane change is possible.First, in step S 110, the control device 15 determines whether or not the own vehicle is in the cruise control mode. Specifically, the control device 15 determines whether the own vehicle is in the cruise control mode based on the output result of the cruise control switch 13 described above. When it is determined that the own vehicle is in the cruise control mode, the control device 15 proceeds to step S 115. When it is determined that the own vehicle is not in the cruise control mode, the controller 15 terminates the current tracking operation.In step S 115, the control device 15 acquires information on the own vehicle. Specifically, the control device 15 acquires the own vehicle speed and the preset vehicle speed as the own vehicle information.In step S 120, the control device 15 acquires information on the preceding vehicle. Specifically, the control device 15 acquires a distance between the vehicles and a relative speed between the preceding vehicle and the own vehicle as the information on the preceding vehicle.In step S 125, the control device 15 acquires information on the adjacent vehicle. Specifically, the control device 15 acquires an inter-vehicle distance and a relative speed between the adjacent vehicle and the own vehicle as the information on the adjacent vehicle.In step S 130, the control device 15 determines whether or not the adjacent vehicle is the vehicle of the preceding vehicle and the adjacent vehicle that has a smaller speed difference from the predetermined vehicle speed and the speed of which is less deviated from the predetermined speed. Specifically, the control device 15 determines the smaller one of the difference between the speed of the preceding vehicle and the predetermined vehicle speed and the difference between the speed of the adjacent vehicle and the predetermined vehicle speed based on the own vehicle information, the preceding vehicle information, and the adjacent vehicle information acquired in steps S 110 to S 125.Therefore, when it is determined that the difference between the speed of the adjacent vehicle and the predetermined vehicle speed is less than the difference between the speed of the preceding vehicle and the predetermined vehicle speed, the control device 15 proceeds to step S 132, in which a lane change to the adjacent vehicle is set as recommended behavior. Thus, when it is determined that the difference between the speed of the adjacent vehicle and the predetermined vehicle speed is equal to or greater than the difference between the speed of the preceding vehicle and the predetermined vehicle speed, the control device 15 proceeds to step S 131.In step S 131, the control device 15 makes an affirmative judgment when the difference between the speed of the preceding vehicle and the predetermined vehicle speed and the difference between the speed of the adjacent vehicle and the predetermined vehicle speed are equal, and the speed of the adjacent vehicle is higher than the preset vehicle speed. The control device 15 proceeds to step S 132, in which a lane change to the adjacent lane is set as the recommended behavior. When a negative judgment is made, the control device 15 proceeds to step S 159, where the preceding vehicle tracking is set as the recommended behavior.When tracking of the preceding vehicle is set as the recommended behavior (NO in step S 130 and NO in step S 131), the control device 15 proceeds to step S 159. In step S 159, the controller 15 determines that the lane is a recommended lane, and writes the lane as the recommended lane in the RAM 53. The controller 15 then proceeds to step S 160. The recommended lane is a lane recommended for the own vehicle to travel. In other words, setting the driving lane as a recommended driving lane means setting the preceding vehicle (in the driving lane) to be recommended behavior.Next, in step S 160, the controller 15 performs adjustment of the vehicle speed and ends the current tracking operation. According to the present embodiment, the control device 15 outputs a command to the driving assistance execution device 14 to allow the own vehicle to travel at a speed at which a predetermined inter-vehicle distance to the preceding vehicle is maintained and the preset vehicle speed is not exceeded. After the control is performed so as to allow the own vehicle to track the preceding vehicle, the control device 15 ends the current tracking operation.When the lane change is set as the recommended behavior (YES in step S 130 or YES in step S 131), the control device 15 proceeds to step S 132. In step S 132, the controller determines that the adjacent lane is the recommended lane, and writes the adjacent lane as the recommended lane in the RAM 53. The controller 15 then proceeds to S 35. In other words, setting the adjacent lane as a recommended lane means setting the lane change to the adjacent lane as recommended behavior.Next, in step S 135, the control device 15 determines whether or not the speed of the adjacent vehicle is higher than the predetermined vehicle speed. When it is determined that the speed of the adjacent vehicle is higher than the predetermined vehicle speed, the control device 15 proceeds to step S 140. When it is determined that the speed of the adjacent vehicle is equal to or lower than the predetermined vehicle speed, the control device 15 proceeds to step S 150.When it is determined that the speed of the adjacent vehicle is equal to or lower than the predetermined vehicle speed (NO in step S 135), the control device 15 proceeds to step S 150. In step S 150, the control device 15 performs adjustment of the vehicle speed. Specifically, for example, the control device 15 outputs a command to the driving assistance execution device 14 to allow the own vehicle to travel at the same speed as the adjacent vehicle. After performing adjustment of the vehicle speed, the control device 15 proceeds to step S 195.When it is determined that the speed of the adjacent vehicle is higher than the preset vehicle speed (YES in step S 135), the control device 15 proceeds to step S 140. In step S 140, the control device 15 acquires an upper limit value α of the change amount. The change amount upper limit value α is a maximum value of a change amount by which the speed of the own vehicle can be changed from the predetermined vehicle speed when the speed of the own vehicle is to be changed to a value larger than the predetermined vehicle speed. The upper limit value α of the amount of change is recorded in advance in the external recording device 16. For example, the upper limit value α of the amount of change is set in advance to a value at which the driver of the own vehicle does not feel uncomfortable even when the own vehicle travels at this speed if the speed of the own vehicle becomes a speed obtained by adding the upper limit value α of the amount of change to the set vehicle speed. As an example, in the present embodiment, the upper limit value α of the change amount is set to 10 km / h.In subsequent step S 145, the control device 15 performs vehicle speed adjustment. Specifically, the control device 15 outputs, to the driving assistance execution device 14, a command at the speed obtained by the upper limit value α of the amount of change added to the predetermined vehicle speed as the speed of the own vehicle after the setting to allow the own vehicle to travel at that speed.Next, in step S 155, the control device 15 allows the own vehicle to travel at a lane change speed and perform lane change. The traveling speed in lane change is a speed of the own vehicle for performing lane change. According to the present embodiment, the control device 15 outputs a command to the driving assistance execution device 14 to perform lane change of the own vehicle at the vehicle speed (current vehicle speed) set as the vehicle speed at the time of lane change in step S 145 or S 150.In subsequent step S 165, the control device 15 determines whether a predetermined space, i.e., a space having a size required for performing a lane change, exists in front of the preceding vehicle that has been bypassed as a result of the lane change performed in step S 555. Specifically, the control device 15 determines that there is the space having a size required for performing a lane change when there is no other vehicle in front of the overtaking preceding vehicle in the lane in which the preceding vehicle is traveling within the range of a predetermined safe distance from the overtaking preceding vehicle.The safety distance may be a fixed value. Alternatively, the safe distance may be a value set in advance based on the speed of the own vehicle or a value set in advance based on the speed of the own vehicle and the speed of the passing preceding vehicle (relative speed). The guard distance is recorded in advance in the external recording apparatus 16. The method for determining whether or not the space having the size required for performing a lane change is present is exemplary. The determination may be made by other methods. When it is determined that the space is present, the control device 15 proceeds to step S 66. When it is determined that the space is not present, the control device 15 proceeds to step S 175.When it is determined that the space having the size required for performing a lane change is present in front of the preceding vehicle (YES in step S 165), the control device 15 proceeds to step S 666. In step S66, the controller 15 determines that the original lane is the recommended lane and writes the original lane as the recommended lane in the RAM 53. The controller 15 then proceeds to step S170. The original lane refers to the lane in which the preceding vehicle that has been passed through the lane change travels. In other words, the lane in which the own vehicle was driven before the lane change in step S 155 is the original lane.Next, in step S 170, the control device 15 outputs a command to the driving assistance execution device 14 to perform lane change at the predetermined vehicle speed. The control device 15 then terminates the current tracking operation.When it is determined that the space of the size required for performing a lane change is not present in front of the passing preceding vehicle (NO in step S 165), the control device 15 proceeds to step S 175. In step S 175, the control device 15 determines whether or not a predetermined change instruction for the vehicle speed has been issued by the driver of the own vehicle. The predetermined vehicle speed change instruction is a command for changing the predetermined vehicle speed. Here, when it is determined that the predetermined change instruction for the vehicle speed has been issued, the control device 15 proceeds to step S 190. When it is determined that the predetermined change instruction for the vehicle speed has not been output, the control device 15 proceeds to step S 180.When it is determined that the predetermined change instruction for the vehicle speed has not been output (NO in step S 175), the control device 15 proceeds to step S 180. In step S 180, the control device 15 determines whether or not a predetermined period of time has elapsed. Here, when it is determined that the predetermined period of time has not elapsed, the control device 15 proceeds to step S 175. When it is determined that the predetermined period of time has elapsed, the control device 15 proceeds to step S 185.In step S 185, the control device 15 sets the current vehicle speed as a new preset vehicle speed, i.e., records (overwrites) the current vehicle speed as the preset vehicle speed in the external recording device 16. The control device 15 then terminates the current tracking operation.When it is determined that the predetermined instruction for changing the vehicle speed has been issued (YES in step S 175), the control device 15 proceeds to step S 190. In step S 190, the control device 15 performs a reset with a driver determined vehicle speed as the current vehicle speed, i.e., records the driver determined vehicle speed as the predetermined vehicle speed in the external recording device 16. The vehicle speed determined by the driver is a vehicle speed that the driver of the own vehicle sets. The control device 15 then terminates the current tracking operation.In other words, it is assumed that, for the driver of the own vehicle, the driving in the original lane in which the own vehicle has driven at the initially set predetermined vehicle speed is the originally desired driving control. Therefore, when a lane change is performed (step S 155), if traveling on the original lane is possible again (YES in step S 165), the control device 15 performs a lane change to the original lane (step S 170). The control device 15 then terminates the current tracking operation.In addition, the control device 15 changes the preset vehicle speed to perform tracking at a speed as close as possible to that of the preceding vehicle in the lane in which the own vehicle travels after the lane change, that is, that of the adjacent vehicle before the lane change (step S 185), when a lane change is performed (step S 155) and further traveling in the original lane is not possible (NO in step S 165), if the driver of the own vehicle has not issued the preset instruction for changing the vehicle speed (NO in step S 175). The control device 15 then terminates the current tracking operation.[1-3. Operations]Next, the operations of the driving assistance system 1 will be described with reference to FIGS. 4 to 7. In the examples shown in FIGS. 4 to 7, it is assumed that an own vehicle 100 is in a cruise control mode and travels at the predetermined vehicle speed as the current vehicle speed unless otherwise specified.In the example shown in FIG. 4, a state is illustrated in which the predetermined vehicle speed of the own vehicle 100 is 80 km / h. The speed of a preceding vehicle 101 is 70 km / h. The speed of a neighboring vehicle 102 is 100 km / h. In this case, among the preceding vehicle 101 and the neighboring vehicle 102, the preceding vehicle 101 has the smaller speed difference from the predetermined vehicle speed. Therefore, the control is performed in which the own vehicle can track the preceding vehicle 101 at the speed reduced to 70 km / h (step S 160).In the example shown in FIG. 5A, a state is illustrated in which the predetermined vehicle speed of the own vehicle 100 is 90 km / h. The speed of the preceding vehicle 101 is 70 km / h. The speed of the adjacent vehicle 102 is 100 km / h. In this case, the preceding vehicle 101 and the adjacent vehicle 102 have the smaller speed difference from the predetermined vehicle speed. Therefore, the control is performed in which the lane change is performed, the speed is increased to 100 km / h, and the own vehicle 100 can track the tracked vehicle 102. One hundred kilometers per hour corresponding to the speed of the own vehicle 100 at this time is a value obtained by adding the upper limit value α (10 km / h) of the amount of change to 90 km / h corresponding to the predetermined vehicle speed (step S 145).In addition, according to the present embodiment, as in the example shown in FIG. 5B, even in a state where the speed of the adjacent vehicle 102 is 105 km / h, the control is performed in which the lane change is performed with the speed of the own vehicle 100 set to 100 km / h and the own vehicle 100 is allowed to track the adjacent vehicle 102. One hundred kilometers per hour is the value obtained by adding the change amount upper limit value α (10 km / h) to 90 km / h, which corresponds to the predetermined vehicle speed.In addition, in the example shown in FIG. 5C, a state in which the preset vehicle speed of the own vehicle 100 is 90 km / h is shown. The speed of the preceding vehicle 101 is 80 km / h. The speed of the adjacent vehicle 102 is 100 km / h. In this case, the speed difference between the vehicle speed and the predetermined vehicle speed is equal for the preceding vehicle 101 and the adjacent vehicle 102. However, the speed of the adjacent vehicle 102 is higher than the predetermined vehicle speed of the own vehicle 100 (step S 131). Therefore, the control is performed in which the lane change is performed, the speed of the own vehicle 100 is increased to 100 km / h, and the own vehicle 100 is allowed to track the adjacent vehicle 102.In the example shown in FIG. 6, a state is shown in which, after performing the lane change in the state shown in FIG. 5A, i.e., after the preceding vehicle 101 has been passed, the space having the size required for performing a lane change is present in front of the preceding vehicle 101. In this case, the lane change is performed with the speed of the own vehicle 100 reduced to 90 km / h, i.e., the vehicle speed set in advance (step S 170).In the example shown in FIG. 7, a state is shown in which, after the lane change in the state shown in FIG. 5A, i.e., after passing the preceding vehicle 101, the space in the amount required for performing a lane change is not present in front of the preceding vehicle 101. In this case, the predetermined vehicle speed is set to 100 km / h, which is the driver set vehicle speed (step S 190), when the driver of the own vehicle outputs the predetermined vehicle speed change instruction to change the preset vehicle speed to, for example, 100 km / h, which corresponds to the current speed of the own vehicle 100 (YES in step S 175). When the driver of the own vehicle has not issued the instruction for changing the predetermined vehicle speed even after the elapse of the predetermined period (YES in step S 180), the predetermined vehicle speed is set to 100 km / h corresponding to the current speed (lane change speed) of the own vehicle 100 (step S 185).[1-4. Effects]With the first embodiment described above, the following effects are obtained.[1A] An output is made to allow the own vehicle to travel so as to track the vehicle from among the preceding vehicle and the adjacent vehicle traveling at the speed closer to the predetermined vehicle speed. When the difference between the speed of the adjacent vehicle and the predetermined vehicle speed is smaller than the difference between the speed of the preceding vehicle and the predetermined vehicle speed, the lane change to the adjacent lane is set as recommended behavior, and the output is made based on the recommended behavior. That is, when the preceding vehicle travels at a speed closer to the predetermined vehicle speed than that of the adjacent vehicle, output is made to allow the own vehicle to track the preceding vehicle. When the adjacent vehicle travels at a speed closer to the predetermined vehicle speed than that of the preceding vehicle, the output is performed to perform the lane change and allow the own vehicle to track the adjacent vehicle. As a result of such a configuration, the output may be made to allow the own vehicle to travel at a speed close to the predetermined vehicle speed in accordance with the traffic flow.In addition, when the difference between the speed of the adjacent vehicle and the predetermined vehicle speed and the difference between the speed of the preceding vehicle and the predetermined vehicle speed are the same and the speed of the adjacent vehicle is higher than the predetermined vehicle speed, the output is made to make a lane change to the adjacent lane as recommended behavior. Conversely, when the speed differences are equal and the speed of the preceding vehicle is higher than the predetermined vehicle speed, the lane in which the preceding vehicle travels is determined as the recommended lane. Output is made to set the preceding vehicle tracking as the recommended behavior.That is, when the differences in speed are equal, the lane in which the vehicle travels at a speed higher than the preset vehicle speed is set as the recommended lane. An output is provided to allow the own vehicle to track the vehicle. One reason for this is that in a state in which the own vehicle cannot travel at the predetermined vehicle speed and needs to travel at a speed near the predetermined vehicle speed, it is considered more desirable for the driver of the own vehicle when the own vehicle is able to travel at a speed higher than the predetermined vehicle speed, rather than at a speed lower than the predetermined vehicle speed.Based on the above, even when the own vehicle travels at a speed close to the predetermined vehicle speed, output may be performed to allow the own vehicle to travel at a speed that is considered desirable for the driver of the own vehicle.[1B] A command to control the own vehicle based on the recommended behavior is output to the driving assistance output device 14. As a result, automatic driving control of the own vehicle can be performed based on the recommended behavior.[1C] When the recommended behavior is lane change to the adjacent lane, the own vehicle travels at the lane change speed equal to or higher than the preset vehicle speed until the lane change to the adjacent lane is completed if the speed of the adjacent vehicle is higher than the preset vehicle speed. As a result, the own vehicle can smoothly change lanes according to the traffic flow.[1D] The lane change speed is set to be equal to or less than a value obtained by the change amount upper limit value α being a predetermined upper limit value added to the predetermined vehicle speed. As a result, the lane change performed at a speed exceeding the skill of the driver of the own vehicle can be suppressed. Consequently, it is possible to prevent the driver of the own vehicle from feeling discomfort when a lane change of the own vehicle is performed.[1E] When the space having the size required for the lane change is present before the preceding vehicle after performing the lane change, the own vehicle is allowed to lane change to the lane in which the preceding vehicle that has been passed travels. That is, it is assumed that, for the driver of the own vehicle, the driving in the original lane in which the own vehicle has been driven at the set predetermined vehicle speed is the originally desired driving control. Therefore, a lane change to the original lane is performed if traveling in the original lane becomes possible again (YES in step S 165) after the lane change is performed (step S 155). The current tracking operation is then ended. As a result, a travel control very similar to the travel intended by the driver of the own vehicle can be performed.[1F] When the space of the lane change required size is not present in front of the preceding overtaking vehicle, the predetermined vehicle speed is changed to the own vehicle speed determined by the driver if an instruction to change the predetermined vehicle speed has been issued by the own vehicle driver. Consequently, the own vehicle can travel at the speed determined by the driver of the own vehicle in accordance with the traffic flow in the lane in which the own vehicle is traveling.[1G] When the driver of the own vehicle has not issued an instruction regarding the change in the predetermined vehicle speed, the predetermined vehicle speed is changed to the vehicle speed for lane change after the lapse of the predetermined period of time. As a result, the predetermined vehicle speed is changed to the lane change speed after the lapse of the predetermined time period, that is, at a time when it can be assumed that the driver of the own vehicle has become accustomed to driving at the lane change speed. Therefore, the own vehicle can subsequently travel at the same speed as other vehicles in its lane in which the own vehicle is traveling.According to the first embodiment, the control device 15 corresponds to an example of a driving assistance device. In addition, steps S 132 and S 159 correspond to an example of a process serving as a first determination means. Steps S 145 and S 155 correspond to an example of a process serving as an output device. In addition, step S166 corresponds to an example of a process serving as a third determination means.In a configuration [4F] described below, step S 130 corresponds to an example of a process serving as determination means. Steps S 145, S 150, S 155, S 160, S 170, and S 185 correspond to an example of a process serving as an output device.[1-5. Variation Examples](1) According to the above-described embodiment, after the lane change from the driving lane to the adjacent lane is performed, when the space of the size required for performing a lane change does not exist in front of the preceding vehicle, the operation of changing the predetermined vehicle speed to the driving lane changing speed is performed after the lapse of the predetermined time period, even if no instruction is issued from the driver of the own vehicle to change the preset vehicle speed. In this regard, the predetermined vehicle speed does not need to be changed when the instruction from the driver of the own vehicle to change the preset vehicle speed has not been issued.More specifically, in the flowchart in FIG. 3, steps S 180 and S 185 may be eliminated. The current tracking process may be ended when a negative determination is made in step S 175 (NO in step S 175). The operation of such a structure will be described with reference to Fig. 8. In the example shown in FIG. 8, a state is shown in which, after the lane change in the state shown in FIG. 5A, i.e., after passing the preceding vehicle 101, the space in the size required for performing a lane change is not present in front of the preceding vehicle 101 that has been passed. In this case, when the driver of the own vehicle has not issued an instruction to change the predetermined vehicle speed to the current vehicle speed, the following operation for this cycle is ended. Then, in the next cycle tracking operation, the output is made to set the lane change by the own vehicle 100 as the recommended behavior, so that an adjacent vehicle 104 whose speed difference from the predetermined vehicle speed is small is tracked.(2) According to the above-described embodiment, the lane change by the own vehicle is performed at a vehicle speed obtained by adding the upper limit value α of the change amount to the predetermined vehicle speed when the recommended behavior is a lane change to the adjacent lane and the speed of the adjacent vehicle should be equal to or higher than the predetermined vehicle speed. In this regard, when the speed of the adjacent vehicle is equal to or higher than the predetermined vehicle speed, the vehicle speed for lane change may be set to a vehicle speed obtained by adding the upper limit value α of the change amount as an upper limit value to the predetermined vehicle speed based on the proportion by which the speed of the adjacent vehicle exceeds the predetermined vehicle speed.[2. Second Embodiment][2-1. Constitution]A basic structure of a second embodiment is similar to that of the first embodiment. Therefore, descriptions of analog configurations will be omitted. Above all, differences will be described.According to the first embodiment described above, the control device 15 performs the control of the own vehicle on the basis of the recommended behavior. In this regard, the second embodiment is different from the first embodiment in that the control device 15 performs control for notifying the driver of the own vehicle based on the recommended behavior, instead of performing the control of the own vehicle based on the recommended behavior. Specifically, the second embodiment is different in that steps S 133 and S 134 are added to the tracking operation according to the first embodiment shown in FIGS. 2 and 3. In addition, step S155 is eliminated and step S156 is added instead. Step S170 is eliminated and steps S171 to S173 are added instead.[2-2. Procedure]Next, the tracking operation according to the present embodiment will be described with reference to flowcharts in FIGS. 9 and 10.In steps S 110 to S 130, the control device 15 executes processes similar to those of the first embodiment.When the lane change is set as the recommended behavior (YES in step S 130 or YES in step S 131), the control device 15 proceeds to step S 133 when the adjacent lane is set as the recommended lane (step S 132). In step S 133, the control device 15 executes an output to inform the rider that the lane change to the adjacent lane is recommended. Specifically, the control device 15 outputs a command to output a message recommending the lane change by the speaker 143 or the display 144.In subsequent step S 134, the control device 15 determines whether or not an expression of the intention of the driver of the own vehicle to lane change is recognized. Specifically, the control device 15 determines that an expression of the intention of the driver of the own vehicle to change lanes is recognized when, for example, the driver of the own vehicle operates a turn signal. Here, when it is determined that the expression of the intention of the driver of the own vehicle to lane change is detected, the control device 15 proceeds to step S 153. The control device 15 then performs processes similar to those according to the first embodiment in steps S 135 to S 150. That is, the control device 15 performs speed adjustment of the own vehicle for lane change. On the other hand, when it is determined that no expression of the intention of the driver of the own vehicle to change lanes is detected, the control device 15 proceeds to step S 1959. The control device 15 determines that the driving lane is the recommended lane, similarly to the first embodiment. The control device 15 then proceeds to step S 160 and performs speed adjustment of the own vehicle to track the preceding vehicle. The control device 15 then terminates the present tracking operation.After ending the vehicle speed adjustment for the lane change (step S 145 or S 150), the control device 15 proceeds to step S 56. In step S 156, the control device 15 determines whether or not a lane change of the own vehicle has been performed by operation by the driver of the own vehicle. Specifically, the control device 15 determines that the lane change of the own vehicle has been performed when, for example, the own vehicle travels between the traveling lane and the adjacent lane. When it is determined that the lane change of the own vehicle has not been performed, the control device 15 proceeds to step S 134. That is, the control device 15 ensures whether or not the lane change has actually been performed (step S 156) while expressing the intention of the driver of the own vehicle to lane change (YES in step S 134). Meanwhile, the control device 15 proceeds to step S 165 when it is determined that the lane change of the own vehicle has been performed.In step S 165, in a similar manner to the first embodiment, the control device 15 determines whether or not there is a space in a size required for performing a lane change in front of the preceding vehicle that has been passed through the lane change. When it is determined that the area is present, the controller 15 proceeds to step S 66. When it is determined that the area is not present, the controller 15 proceeds to S 175. The control device 15 performs processes similar to those according to the first embodiment in steps S 175 to S 190.When the space having the size required for performing a lane change is present in front of the preceding vehicle (YES in step S 165), the control device 15 proceeds to step S 666. In step S66, the control device 15 determines that the original lane is the recommended lane in a manner similar to that according to the first embodiment. The controller 15 then proceeds to step S 171.Next, in step S 171, the control device 15 performs notification that suggests a lane change to the driver of the own vehicle. More specifically, in a similar manner to step S 133, the control device 15 outputs a command to perform notification that suggests lane change using the speaker 143 or the display 144.In the following step S172, the control device 15 determines whether or not an expression of the intention of the driver of the own vehicle to change lanes is recognized. Specifically, similarly to step S 132, the control device 15 determines that the expression of the intention of the driver of the own vehicle to change lanes is recognized when, for example, the driver of the own vehicle operates a turn signal. Here, when it is determined that an expression of the intention of the driver of the own vehicle to change lanes is recognized, the control device 15 proceeds to step S 173. In step S 173, the control device 15 waits until the lane change of the own vehicle is performed by the operation by the driver of the own vehicle. After the lane change is performed, the control device 15 ends the current lane change operation. Thus, when it is determined that an expression of the intention of the driver of the own vehicle to change lanes is not recognized, the control device 15 proceeds to step S 175. The control device 15 performs speed adjustment of the own vehicle to track the preceding vehicle after the lane change, i.e., the originally adjacent vehicle (steps S 175 to S 190), and ends the current lane change operation.[2-4. Operations]In the examples shown in FIGS. 5A to 5C and 6, according to the present embodiment, notification is made that suggests a lane change to the driver of the own vehicle.[2-3. Effects]According to the second embodiment described above in more detail, in addition to the effect [1A] of the first embodiment described above, the following effect is obtained.[2A] When it is determined in step S 132 that the recommended lane is the adjacent lane, the controller 15 performs, in step S 133, an output for notification recommending a lane change to the adjacent lane to the vehicle occupant of the own vehicle. As a result of such an operation, a notification requesting the lane change is made when the recommended behavior is a lane change. Therefore, the driver of the own vehicle may allow the own vehicle to travel at the set speed (driver set vehicle speed) or a speed in the vicinity of the set vehicle speed, according to the notification.According to the second embodiment, step S 133 corresponds to an example of a process serving as an output device.In the configuration [4F] described below, steps S 133 and S 171 correspond to an example of a process serving as output means.[3. Third Embodiment][3-1. Constitution]A basic structure according to a third embodiment is similar to that according to the first embodiment. Therefore, descriptions of similar configurations will be omitted. Differences will be mainly described.According to the first embodiment described above, when the space in front of the preceding vehicle that has been passed after the lane change is not free (NO in step S 165), the control device 15 performs the own vehicle control to directly track the preceding vehicle, i.e., the adjacent vehicle before the lane change. In this regard, the third embodiment is different from the first embodiment in that the control device 15 determines the recommended lane in which the own vehicle is to travel and performs control until the own vehicle returns to the original lane after the lane change is performed to allow the own vehicle to travel in the recommended lane. Specifically, the control device 15 performs a lane selection operation instead of the tracking operation according to the first embodiment.[3-2. Operation][3-2-1. Track Selection Operation]The track selection operation will be described with reference to the flow chart in Fig. 11. The lane selection process is repeatedly performed while the own vehicle is in the cruise mode and is traveling on a road on which lane change is possible. In cases where the triggering object is omitted in the following description, the object is the control device 15.In step S 10, the control device 15 resets or clears a lane change flag (hereinafter, LCFlag). That is, 0 is set as the value LCFlag of the lane change flag. The lane change flag LCFlag is a flag indicating whether the lane change has not yet been performed (the own vehicle travels on the original lane) or the lane change has been performed (the own vehicle travels on the adjacent lane). The lane change flag LCFlag is set to 1 when the lane change from the lane to the adjacent lane is performed. The lane change flag LCFlag continues to be set to 0 when the lane change from the adjacent lane to the original lane is performed.In step S 20, the control device 15 determines whether or not the lane change flag LCFlag is 0. When it is determined that the lane change flag LCFlag is 0, the control device 15 proceeds to step S 30. When it is determined that the lane change flag LCFlag is not 0, the control device 15 proceeds to step S 40.In step S 30, the control device 15 performs a lane change operation. As described below, the lane change operation is an operation for allowing the own vehicle to perform lane change based on the predetermined vehicle speed, a traveling state of the preceding vehicle, and a traveling state of the adjacent vehicle. After performing the lane change operation, the control device 15 proceeds to step S 20. Then, the control device 15 repeatedly executes the processes in step S 20 and the subsequent steps.In step S 40, the controller 15 performs a lane return operation. As described below, the lane return process is a process for allowing the own vehicle to return to the lane in which the own vehicle has traveled before the lane change, based on the predetermined vehicle speed, the traveling state of the preceding vehicle, and the traveling state of the adjacent vehicle. After performing the lane return operation, the controller 15 proceeds to step S 20. Then, the control device 15 repeatedly executes the processes at step S 20 and the subsequent steps.That is, when the lane change from the lane to the adjacent lane is performed (LCFlag=1), the control device 15 repeatedly performs the lane return operation until the own vehicle returns by again initiating the lane change to the lane in which the own vehicle has traveled before performing the lane change.[3-2-2. Lane Change Operation]Next, the lane change operation performed at step S 30 of the lane selection operation will be described with reference to the flowcharts in FIGS. 12 and 13. The lane change operation is a method of determining the recommended lane on which the own vehicle is to travel based on a comparison of the predetermined vehicle speed with the traveling state of the preceding vehicle and the traveling state of the adjacent vehicle, and performing output of the recommended lane.The traveling state of the preceding vehicle refers to the state in which the preceding vehicle travels. For example, the determination of whether or not a preceding vehicle exists may be given the speed of the preceding vehicle and the distance from the own vehicle as the traveling state of the preceding vehicle. The running state of the adjacent vehicle refers to the state in which the adjacent vehicle is running. For example, the determination of whether or not there is an adjacent vehicle may be the speed of the adjacent vehicle and the distance from the own vehicle as the traveling state of the adjacent vehicle.The lane change operation is different in that steps S 100, S 126 to S 129, S 136, S 141, S 156 to S 158, S 161 to S 163 are added to the lane following operation according to the first embodiment shown in FIGS. 2 and 3. In addition, steps S 110, S 145, and S 150 are eliminated.In step S 100, the control device 15 sets a speed flag (hereinafter, VFlag) to 0. The speed flag VFlag is a flag indicating the state of the speed of the own vehicle. The speed flag VFlag set to 0 indicates that the own vehicle is traveling at the predetermined vehicle speed.In steps S 115 to S 125, the control device 15 performs similar processes to steps S 115 to S 125 in FIG. 2.In step S 126, the control device 15 determines whether or not the speed of the preceding vehicle is less than the predetermined vehicle speed. Specifically, the control device 15 determines that the speed of the preceding vehicle is less than the predetermined vehicle speed when the vehicle speed of the preceding vehicle is equal to or less than the predetermined vehicle speed. When it is determined that the vehicle speed of the preceding vehicle is equal to or less than the predetermined vehicle speed, the control device 15 proceeds to step S 127. When it is determined that the vehicle speed of the preceding vehicle is higher than the predetermined vehicle speed, the control device 15 proceeds to step S 129. In cases where a basic preset vehicle speed is mentioned in the following description, the basic preset vehicle speed refers to the preset vehicle speed when the own vehicle is traveling in the lane while the current step is being performed, that is, the preset vehicle speed before the lane change is performed to the adjacent lane which is an overtaking lane.In addition, in the present step, if the preceding vehicle information acquired in step S 120 indicates that there is no preceding vehicle in the lane, the controller 15 determines that the vehicle speed of the preceding vehicle is infinite. That is, when the vehicle speed of the preceding vehicle is higher than the basic predetermined vehicle speed, or when the preceding vehicle is not present, the control device 15 proceeds to step S 129.In step S 129, the control device 15 prohibits determination of the travel lane in steps S 132 and S 159. The control device 15 then ends the current lane change operation. That is, the control device 15 terminates the current lane change operation without performing the processes in steps S 132 and S 159.When it is determined that the vehicle speed of the preceding vehicle is equal to or lower than the basic predetermined vehicle speed, the control device 15 proceeds to step S 127. In step S 127, the controller 15 determines whether or not there is a predetermined space on the adjacent lane. The predetermined space refers to a space that, when a direction perpendicular to a direction of the lane on a horizontal plane (to a tangent direction in cases where the lane is curved) is a lateral direction and the own vehicle moves in the lateral direction and is positioned on the adjacent lane, a predetermined distance is present within a range from the position of the own vehicle forward and rearward in which no other vehicle is located.The predetermined distance is a distance required when the own vehicle performs the lane change from the adjacent lane. The distance is set based on the speed of the own vehicle, the speed limit of the road, the time when a driver of an adjacent vehicle typically applies the brakes, and the like. The predetermined distance is recorded in the external recording device 16.When it is determined that the predetermined space is not present on the adjacent lane, the controller 15 proceeds to step S 195. When it is determined that the predetermined space exists on the adjacent lane, the controller 15 proceeds to step S 128.In step S 128, the control device 15 determines whether or not there is an adjacent vehicle outside the predetermined space referred to by step S 127 on the adjacent lane based on the output signal of the radar sensor 112. When it is determined that there is no adjacent vehicle, the control device 15 proceeds to step S 195. When it is determined that there is an adjacent vehicle, the control device 15 proceeds to step S 130.At steps S 130 to S 153, the control device 15 performs similar operations to steps S 130 to S 153 in FIG. 2.That is, in step S 130, the controller 15 determines whether or not the adjacent vehicle has the smaller speed difference from the basic preset vehicle speed among the preceding vehicle and the adjacent vehicle. Specifically, the control device 15 compares the preceding vehicle running state and the adjacent vehicle running state with the basic preset vehicle speed based on the own vehicle information, the preceding vehicle information, and the adjacent vehicle information acquired in steps S 115 to S 125, and determines the smaller one of the difference between the preceding vehicle speed and the basic preset vehicle speed and the difference between the adjacent vehicle speed and the basic preset vehicle speed.Here, when it is determined that the difference between the speed of the adjacent vehicle and the basic preset vehicle speed is smaller than the difference between the speed of the preceding vehicle and the basic preset vehicle speed, the control device 15 proceeds to step S 132. On the other hand, when it is determined that the difference between the speed of the adjacent vehicle and the basic preset vehicle speed is equal to or greater than the difference between the speed of the preceding vehicle and the basic preset vehicle speed, the control device 15 proceeds to step S 131.In step S 131, the control device 15 makes an affirmative judgment when the difference between the speed of the preceding vehicle and the basic predetermined vehicle speed and the difference between the speed of the adjacent vehicle and the basic predetermined vehicle speed are equal to each other and the speed of the adjacent vehicle is higher than the predetermined vehicle speed. The controller 15 then proceeds to step S 132. If a negative determination is made, the controller 15 proceeds to step S 1959.In step S 159, the control device 15 determines that the driving lane is the recommended driving lane. Then, the control device 15 proceeds to step S 160. That is, the control device 15 determines that the driving lane is the recommended driving lane when the difference between the speed of the adjacent vehicle and the basic preset vehicle speed is greater than the difference between the speed of the preceding vehicle and the basic preset vehicle speed, or when the difference between the speed of the preceding vehicle and the basic preset vehicle speed and the difference between the speed of the adjacent vehicle and the basic preset vehicle speed is equal and the speed of the adjacent vehicle is lower than the basic preset vehicle speed (NO in step S 131).In this way, the control device 15 determines the lane in which the vehicle having the speed closer to the basic predetermined vehicle speed is present from the speed of the preceding vehicle and the speed of the adjacent vehicle as the recommended lane for the own vehicle. In addition, the control device 15 sets the recommended lane so that the amount of deceleration during driving at the predetermined vehicle speed is small.Next, in step S 160, the control device 15 performs vehicle speed adjustment of the own vehicle in a similar manner to that in step S 160 in FIG. 2, and performs the current lane change operation. According to the present embodiment, the control device 15 outputs a command to the driving assistance execution device 14 to allow the own vehicle to travel at the same speed as the vehicle speed of the preceding vehicle.In step S 132, the controller 15 determines that the adjacent lane is the recommended lane. Then, the controller 15 proceeds to step S 153. That is, the controller 15 determines that the adjacent lane is the recommended lane when the difference between the speed of the adjacent vehicle and the basic preset vehicle speed is less than the difference between the speed of the preceding vehicle and the basic preset vehicle speed (YES in step S 130), or when the difference between the speed of the preceding vehicle and the basic preset vehicle speed and the difference between the speed of the adjacent vehicle and the basic preset vehicle speed is equal and the speed of the adjacent vehicle is higher than the basic preset vehicle speed (YES in step S 131).In this way, the control device 15 determines the lane in which the vehicle travels at the speed closer to that of the basic predetermined vehicle speed from among the speed of the preceding vehicle and the speed of the adjacent vehicle as the recommended lane for the own vehicle. In addition, the control device 15 sets the recommended lane so that the amount of deceleration during driving at the basic preset vehicle speed is small.Next, in step S 135, the control device 15 determines whether or not the speed of the adjacent vehicle is higher than the basic predetermined vehicle speed. When it is determined that the speed of the adjacent vehicle is higher than the basic preset vehicle speed, the control device 15 proceeds to step S 140. When it is determined that the speed of the adjacent vehicle is equal to or lower than the basic predetermined vehicle speed, the control device 15 proceeds to step S 136.In step S 136, the controller 15 sets the speed flag VFlag to 2 and proceeds to step S 555. The speed flag VFlag set to 2 indicates that the own vehicle is traveling at the predetermined vehicle speed (basic preset vehicle speed) or slower.When an affirmative judgment is made in step S 135 (YES in step S 135), the control device 15 proceeds to step S 140. In step S 140, the control device 15 performs a similar process to step S 140 in FIG. 2, and then proceeds to step S 141.In step S 141, the controller 15 sets the speed flag VFlag to 1, and then proceeds to step S 555. The speed flag VFlag set to 1 indicates that the own vehicle is traveling at a speed higher than the predetermined vehicle speed (the basic predetermined vehicle speed).When it is determined that there is no adjacent vehicle in the adjacent lane (NO in step S 128) or when it is determined that the adjacent lane is the recommended lane, the control device 15 proceeds to step S 155. In step S 155, the control device 15 performs output to perform traveling control of the own vehicle to switch the traveling lane to the adjacent traveling lane. That is, the control device 15 executes output to the driving assistance execution device 14 (steering device 141) to perform traveling control of the own vehicle such that the own vehicle changes lanes to get on the adjacent lane.In subsequent step S 156, the control device 15 sets the lane change flag LCFlag to 1.Next, in step S 157, the controller 15 determines whether or not the speed flag VFlag is 1. When it is determined that the speed flag VFlag is 1, the control device 15 proceeds to step S 163. When it is determined that the speed flag VFlag is not 1, the control device 15 proceeds to step S 195.When it is determined that the speed flag VFlag is not 1, the control device 15 proceeds to step S 195. In step S 195, the control device 15 determines whether or not the speed flag VFlag is 2. When it is determined that the speed flag VFlag is 2, the control device 15 proceeds to step S 132. When it is determined that the speed flag VFlag is not 2, the control device 15 proceeds to step S 161.When it is determined that the speed flag VFlag is not 2, the control device 15 proceeds to step S 161. In step S 161, the control device 15 performs vehicle speed adjustment of the own vehicle. Specifically, the control device 15 outputs a command to the driving assistance execution device 14 to allow the own vehicle to travel at the basic predetermined vehicle speed. The control device 15 then ends the current lane change operation.When it is determined that the speed flag VFlag is 2, the control device 15 proceeds to step S 132. In step S 162, the control device 15 performs vehicle speed adjustment of the own vehicle. Specifically, the control device 15 outputs a command to the driving assistance execution device 14 to allow the own vehicle to travel at the same speed as the adjacent vehicle. The control device 15 then ends the current lane change operation. Here, the adjacent vehicle refers to the adjacent vehicle before the own vehicle changes lanes. That is, the adjacent vehicle refers to the vehicle traveling in front of the own vehicle in the lane in which the own vehicle travels after the lane change (step S 155).When it is determined that the speed flag VFlag is 1, the control device 15 proceeds to step S 163. In step S 163, the control device 15 performs vehicle speed adjustment of the own vehicle. Specifically, the control device 15 outputs a command to the driving assistance execution device 14 to allow the own vehicle to travel at a speed higher than the basic preset vehicle speed. The control device 15 then ends the current lane change operation. The speed at which the own vehicle travels is set to be equal to or lower than a speed obtained by adding the upper limit value α of the change amount to the predetermined vehicle speed.[3-2-2. Track Return Operation]Next, the track return operation performed in step S40 of the track selection operation will be described with reference to the flow chart in Figs. 14 and 15. The lane return process is a process for returning the own vehicle to the lane in which the own vehicle was driven before the lane change after the lane change of the own vehicle was performed in the lane change process.In step S 200, the control device 15 acquires the own vehicle information in a manner similar to that shown in step S 115 in FIG. 12.In step S 205, the control device acquires the information on the preceding vehicle in a manner similar to that shown in step S 120 in FIG. 12. However, the preceding vehicle refers to a vehicle that travels in front of the own vehicle in the lane in which the own vehicle travels after performing the lane change by the lane change operation (step S 155), that is, the vehicle on the adjacent lane before the own vehicle performs the lane change.In step S 210, the control device 15 acquires the information on the adjacent vehicle in a manner similar to that shown in step S 125 in FIG. 12. However, the adjacent vehicle refers to the vehicle traveling in the adjacent lane adjacent to the lane in which the own vehicle travels after performing the lane change by the lane change operation (step S 155), that is, the vehicle in the lane before the own vehicle performs the lane change (hereinafter, referred to as the original lane).In step S 215, the control device 15 determines whether or not the lane change to the adjacent lane is completed. Here, the completion of the lane change to the adjacent lane refers to the own vehicle passing the preceding vehicle in the original lane as a result of the lane change. More specifically, the control device 15 acquires the time elapsed since the lane change was performed (step S 155). When a predetermined period of time has elapsed since the lane change was performed, the control device 15 determines that the lane change to the adjacent lane is completed. When it is determined that the predetermined time has elapsed since the lane change was performed, the control device 15 proceeds to step S 220. When it is determined that the predetermined time has not elapsed yet, the control device 15 proceeds to step S 200 and repeats the processes in step S 200 and the subsequent steps. The elapsed time from the execution of the lane change is recognized based on a method performed as a method independent of the present lane return operation by the controller 15.In step S 220, the control device 15 determines whether or not there is sufficient space in the original lane, i.e., a predetermined space for the own vehicle, to execute a lane change. The predetermined space for the own vehicle to perform lane change refers to a space having a size necessary for performing lane change to return the own vehicle to the original lane. More specifically, the control device 15 determines that the predetermined space exists for the own vehicle to perform the lane change, that is, a sufficient area exists in the original lane when there is no other vehicle in front of the overtaking preceding vehicle in the original lane within the range having the above-described safe distance from the overtaking preceding vehicle.When it is determined that the sufficient space exists in the original lane, the control device 15 proceeds to step S 264. When it is determined that the sufficient space is not present, the control device 15 proceeds to step S 225.The controller 15 determines in step S 220 that the sufficient space is not present in the original lane, and proceeds to step S 225. In step S225, the control device 15 determines whether or not the speed flag VFlag is 1. When it is determined that the speed flag VFlag is 1, the control device 15 proceeds to step S 230. When it is determined that the speed flag VFlag is not 1, the controller 15 terminates the current process of lane return.At step S 230, the control device 15 outputs a command to the speakers 143 and the display 144 to transmit a request to the driver of the own vehicle as to whether or not to change the predetermined vehicle speed. That is, the control device 15 makes a request to the driver of the own vehicle using audio and an image 144 displayed on the display as to whether or not the predetermined vehicle speed is to be changed, for example, the current vehicle speed higher than the basic predetermined vehicle speed is settable as a new predetermined vehicle speed.Next, in step S 235, the control device 15 determines whether or not an input allowing the present vehicle speed to be changed has been made by the driver of the own vehicle. Here, the input by the driver of the own vehicle is performed by the display 144. Here, when it is determined that the input allowing a change has been made, the control device 15 proceeds to step S 255. When it is determined that no input allowing the change has been made, the control device 15 proceeds to step S 240.In step S 240, the control device 15 acquires the elapsed time from the time when the request was made to the driver of the own vehicle in step S 230. When the elapsed time exceeds a predetermined time, the control device 15 proceeds to step S 245. When the elapsed time does not exceed the predetermined time period, the control device 15 proceeds to step S 230, and repeats the processes in step S 230 and the subsequent steps. The elapsed time from the request to the driver of the own vehicle is acquired based on a method performed by the controller 15 as a method independent of the present lane return operation.In step S 245, the control device 15 outputs a command to the driving assistance execution device 14 to allow the own vehicle to travel at the basic preset vehicle speed.In subsequent step S250, the controller 15 sets the speed flag VFlag to 0 and terminates the present lane return operation.When it is determined that the input by the driver of the own vehicle that allows a change in the predetermined vehicle speed is made in step S 235, the control device 15 proceeds to step S 255. In step S 255, the control device 15 sets (writes to the external recording device 16) the current speed of the own vehicle that is higher than the basic preset vehicle speed as a new preset vehicle speed.In subsequent step S 260, the controller 15 sets the speed flag VFlag to 3 and ends the present lane return operation. The speed flag VFlag set to 3 indicates that the own vehicle is traveling at a speed higher than the basic preset vehicle speed and that the preset vehicle speed is also higher than the basic preset vehicle speed.The controller 15 determines that the sufficient space exists in the original lane in step S 220, and proceeds to step S 264. In step 264, the controller 15 determines that the original lane is the recommended lane, and writes the original lane as the recommended lane in the RAM 53.Next, in step S 265, the control device 15 performs output to allow the own vehicle to make a lane change to the original lane. More specifically, the control device 15 outputs a command to the driving assistance device 14 to perform the lane change to the original lane.In subsequent step S 270, the control device 15 sets the lane change flag LCFlag to 0.Next, in step S 275, the controller 15 determines whether or not the speed flag VFlag is 1 or 2. When it is determined that the speed flag VFlag is 1 or 2, the control device 15 proceeds to S 305. When it is determined that the speed flag VFlag is neither 1 nor 2 (the speed flag VFlag is either 0 or 3), the control device 15 proceeds to step S 280.In step S 280, the controller 15 determines whether or not the speed flag VFlag is 3. Here, the controller 15 terminates the present track return operation when it is determined that the speed flag VFlag is not 3 (the speed flag VFlag is 0). When it is determined that the speed flag VFlag is 3, the control device 15 proceeds to step S 285.When it is determined that the speed flag VFlag is 3, the control device 15 proceeds to step S 285. In step S285, the control device 15 outputs a command to the speakers 143 and the display 144 to transmit a request to the driver of the own vehicle regarding whether or not to change the set vehicle speed.Next, in step S 290, the control device 15 determines whether an input has been made by the driver of the own vehicle that allows the preset vehicle speed to be changed. Here, the control device 15 proceeds to step S 300 when it is determined that the input has been made via the display 144 that allows a change. When it is determined that the input allowing a change has not been made, the control device 15 proceeds to S 209.In step S 295, the control device 15 acquires the time elapsed since the request was transmitted to the driver of the own vehicle in step S 285. When it is determined that the elapsed time has exceeded a predetermined time, the controller 15 ends the current lane return operation. When it is determined that the predetermined time has not been exceeded, the control device 15 proceeds to step S 225 and repeats the processes in step S 225 and the subsequent steps. The elapsed time from the transmission of the request to the driver of the own vehicle (step S 285) is acquired based on a method from the controller 15, which is a method executed independently of the present lane return operation.When it is determined in step S 290 that the input is made by the driver of the own vehicle that enables a change in the predetermined vehicle speed, the control device 15 proceeds to step S 300. In step S 300, the control device 15 sets (records) the basic preset vehicle speed as a new preset vehicle speed.In step S 305, the control device 15 outputs a command to the driving assistance execution device 14 to allow the own vehicle to travel at the basic predetermined vehicle speed. The control device 15 then terminates the present track return operation.[3-3. Effects]By the third embodiment described above in detail, the following effects are obtained.[3A] The control device 15 determines the recommended lane in which the own vehicle is to travel (steps S 132 and S 159) based on the comparison of the predetermined vehicle speed with the traveling state of the preceding vehicle and the traveling state of the adjacent vehicle. The predetermined vehicle speed is set in advance to allow the own vehicle to travel at a constant speed. The preceding vehicle is the vehicle that travels in front of the own vehicle in the lane in which the own vehicle travels. The adjacent vehicle is the vehicle that travels in front of the own vehicle on the adjacent lane adjacent to the own lane. Moreover, the control device 15 performs output based on the recommended lane (steps S 155, S 163, S 255, S 265, and S 300). As a result, the control device 15 determines the recommended lane based on the comparison of the predetermined vehicle speed with the traveling state of the preceding vehicle and the traveling state of the adjacent vehicle. Therefore, the lane in which the own vehicle is to travel can be determined appropriately without the driver of the own vehicle itself making the decision.[3B] The control device 15 may determine, as the recommended lane, the lane in which the vehicle travels on the adjacent lane that is closer to the predetermined vehicle speed from among the speed of the preceding vehicle ahead in the lane in front of the own vehicle and the speed of the adjacent vehicle in front of the own vehicle (steps S 132 and S 159). That is, the recommended lane is set so that the amount of deceleration during traveling at the predetermined vehicle speed is small.When the preceding vehicle travels at a speed closer to the predetermined vehicle speed than that of the adjacent vehicle, output is performed to allow the own vehicle to track the preceding vehicle. When the adjacent vehicle travels at a speed closer to the predetermined vehicle speed than the preceding vehicle, output is made to make a lane change and allow the own vehicle to travel in the adjacent lane. As a result, an output can be made which allows the own vehicle to float in the traffic flow at a speed close to the predetermined vehicle speed (i.e., so that the amount of deceleration is small).[3c] In step S126, the control device 15 may determine whether or not the speed of the preceding vehicle is slower than the predetermined vehicle speed. In step S 132, the control device 15 may determine the recommended lane based on the determination result in step S 126. As a result, the recommended lane may be determined based on the speed of the preceding vehicle.[3D] Specifically, the control device 15 may prohibit the determination of the recommended lane in step S 129 when it is determined in step S 126 that the speed of the preceding vehicle is faster than the predetermined vehicle speed. As a result, the determination of the recommended lane is prohibited, for example, when the vehicle speed of the preceding vehicle is higher than the predetermined vehicle speed or when there is no preceding vehicle. Therefore, the own vehicle can be allowed to travel in the current lane. That is, in cases where a lane change does not need to be performed, the own vehicle may be allowed to travel in the current lane.[3E] Specifically, the control device 15 may perform the determination of the recommended lane in step S 132 in step S 126 when it is determined in step S 126 that the speed of the preceding vehicle is equal to or lower than the predetermined vehicle speed. As a result, a lane change can be performed when the vehicle speed of the preceding vehicle is equal to or lower than the predetermined vehicle speed, that is, when it is difficult for the own vehicle to continue traveling in the lane.[3F] In step S 155, the control device 15 may perform output to perform the own vehicle traveling control such that the own vehicle switches the traveling lane to the adjacent lane when it is determined in step S 132 that the recommended traveling lane is the adjacent lane. As a result, automatic driving control of the own vehicle can be performed based on the recommended lane.[3G] In step S 163, the control device 15 may perform output to allow the own vehicle to travel at the lane change speed that is a speed equal to or higher than the predetermined vehicle speed (basic predetermined vehicle speed) after the lane change to the adjacent lane is completed, when it is determined in step S 132 that the recommended lane is the adjacent lane and the speed of the adjacent vehicle is higher than the predetermined vehicle speed (basic predetermined vehicle speed). As a result, the own vehicle can change lanes in the traffic flow in a floating manner. Here, the lane change speed refers to the vehicle speed of the own vehicle after the lane change to the adjacent lane.[3H] The lane change speed may be equal to or less than the value obtained by a predetermined upper limit value added to the predetermined vehicle speed (basic predetermined vehicle speed). As a result, it is possible to suppress the lane change from being performed at a speed exceeding the skill of the driver of the own vehicle. Consequently, discomfort of the driver of the own vehicle experienced when a lane change of the own vehicle is performed can be suppressed.[3I] In step S 255, the control device 15 may change the predetermined vehicle speed when an instruction is issued from the driver of the own vehicle regarding a change in the predetermined vehicle speed (YES in step S 235) after the lane change to the adjacent vehicle is completed (YES in step S 215), if the predetermined space required for the lane change is not present for the own vehicle in the original lane (NO in step S 220), and the speed of the preceding vehicle ahead of the own vehicle is higher than the predetermined vehicle speed (basic predetermined vehicle speed) (YES in step S 225).As a result, after performing the lane change to the adjacent lane, the control device 15 may adjust the vehicle speed of the own vehicle in the adjacent lane when a lane change to the original lane is difficult. The own vehicle can thus float together in the traffic flow without problems. Moreover, discomfort experienced by the driver due to the shift to the new preset vehicle speed without an instruction of the driver of the own vehicle becoming a new preset vehicle speed can be suppressed because the shift is performed based on the instruction by the driver of the own vehicle.[3J] In step S 300, the control device 15 may perform output to allow the own vehicle to change the lane to the original lane and change the predetermined vehicle speed to the predetermined vehicle speed before the change (basic predetermined vehicle speed) if there is the space for changing lanes of the own vehicle in the original lane after the predetermined vehicle speed (step S 255) is changed (YES in step S 220). As a result, the own vehicle can be allowed to travel in the original lane at the predetermined vehicle speed (basic predetermined vehicle speed) at which the own vehicle was originally traveling in the original lane. Therefore, the own vehicle can travel at the speed originally desired by the driver of the own vehicle (the basic preset vehicle speed, which is the speed at which it has traveled in the original lane).[3K] In step S 265, the control device 15 may perform output to allow the own vehicle to change the lane to the original lane if the range prescribed in advance for the lane change by the own vehicle is in the original lane (YES in step S 220) after the lane change to the adjacent lane is completed (YES in step S 215). As a result, the own vehicle can travel in the lane (original lane) originally desired by the driver of the own vehicle because the own vehicle can return to the original lane.[3L] In step S66, the control device 15 may set the traveling lane in which the own vehicle has traveled before performing the lane change as a recommended traveling lane when the output is performed in step S155 to perform the traveling control of the own vehicle such that the own vehicle switches the traveling lane to that of the adjacent vehicle. As a result, the own vehicle can return to the original lane by controlling the own vehicle to travel in the recommended lane because the original lane is set as the recommended lane after the lane change is performed.According to the third embodiment, steps S 132 and S 159 correspond to an example of a process serving as first determination means. Step S 126 corresponds to an example of a process serving as a second determination means and a determination execution means. Step S129 corresponds to an example of a process serving as determination prohibiting means. Moreover, steps S 155, S 163, S 255, S 265, and S 300 correspond to an example of a process serving as an output device. In addition, step S 146 corresponds to an example of a process serving as third determination means.[3-4. Examples of Variations]According to the third embodiment, vehicle speed setting of the own vehicle is performed in step S 163 after the lane change in step S 155. However, the vehicle speed of the own vehicle may be adjusted in a manner similar to step S 163 while the lane change is performed in step S 555.[4. Other Embodiments]The embodiments of the present invention are described above. However, the present invention is not limited to the above-described embodiments. Obviously, different modes are possible.[4A] According to the above-described embodiments, traveling control is performed such that the own vehicle returns to the original lane, the original lane being the recommended lane, after performing the lane change from the traveling lane to the adjacent lane (step S 155). In view of this, the control device 15 may be configured such that after performing the lane change from the driving lane to the adjacent lane (step S 155), the vehicle traveling in front of the own vehicle on the adjacent lane (current driving lane) is set as a new preceding vehicle, the vehicle traveling on the original driving lane (current adjacent lane) is set as a new adjacent vehicle, and the driving lane is set as the recommended driving lane on which the vehicle travels from the new preceding vehicle and the new adjacent vehicle whose speed is closer to the basic preset vehicle speed.In addition, the control device 15 may be configured to perform output for controlling the traveling of the own vehicle in the recommended lane.In this case, for example, the preceding vehicle in the flowcharts in FIGS. 2 and 3 may be replaced with the new preceding vehicle. The adjacent vehicle may be replaced with the new adjacent vehicle. The driving lane may be replaced with the current driving lane. The adjacent track may be replaced with the current adjacent track. Thereby, the operations in the flowcharts in FIGS. 2 and 3 can be executed.[4B] In the above-described embodiments, an example in which the own vehicle travels on a road composed of two lanes, the traveling lane and the adjacent lane will be described. However, the road is not limited thereto. The road can have a plurality of lanes or be composed of a plurality of lanes, that is to say of two or more lanes, such as three or four lanes, for example.[4C] A function provided by a single constituent element according to the above-described embodiments may be distributed to a plurality of constituent elements. Functions distributed over a plurality of structural elements can be integrated in a single constituent or structural element. In addition, at least a part of a structure according to the above-described embodiments may be replaced with a well-known structure for providing a similar function. Further, a part of a configuration according to the above-described embodiments can be omitted to an extent that allows the problem to be solved. In addition, at least a part of a configuration according to the above-described embodiments may be added or may replace another configuration according to the above-described embodiments. Each embodiment included in the technical field indicated by the terms including the scope of the claims is an embodiment of the present invention.[4D] The present invention can also be realized by various modes such as a program that causes the control device 15 to function, a medium on which the program is recorded, and a driving assistance method in addition to the above-described driving assistance system 1 and the control device 15.[4E] The present invention can be realized by the following configurations.(Configuration 1) A driving assistance apparatus that is a driving assistance apparatus (15) mounted in an own vehicle and performs driving assistance for the own vehicle, and includes: determination means (S 130) that determines tracking of either a preceding vehicle or an adjacent vehicle, the vehicle traveling at a speed whose difference from a predetermined speed is smaller than a recommended behavior of the own vehicle on the basis of the difference between the speed of the preceding vehicle in a lane and the predetermined vehicle speed, and the difference between the speed of the adjacent vehicle traveling in front of the own vehicle in an adjacent lane adjacent to the own lane and a predetermined vehicle speed to cause the own vehicle to travel at a constant speed than the predetermined vehicle speed, and setting a traveling lane on which the own vehicle travels as a recommended traveling lane; and an output device (S 133, S 145, S 150, S 155, S 160, S 170, S 171, S 185, S 190) that performs output based on the recommended behavior.That is, the output is performed to cause the own vehicle to travel such that, of the preceding vehicle and the adjacent vehicle, the vehicle traveling at a speed closer to the predetermined vehicle speed is followed. For example, an output is performed so that the own vehicle follows the preceding vehicle when the preceding vehicle travels at a speed closer to the predetermined vehicle speed than that of the adjacent vehicle. When the adjacent vehicle travels at a speed closer than that of the preceding vehicle to the predetermined vehicle speed, output for lane change is performed and the own vehicle is caused to follow the adjacent vehicle.As a result of such a configuration, the own vehicle can be allowed to float in the traffic flow at a speed close to the predetermined vehicle speed.(Configuration 2) A driving assistance apparatus including the driving assistance apparatus according to Configuration 1, wherein the determination means sets a lane change to the adjacent lane as recommended behavior when the difference between the speed of the adjacent vehicle and the predetermined vehicle speed is less than the difference between the speed of the preceding vehicle and the predetermined vehicle speed.(Constitution 3) A driving assistance apparatus including the driving assistance apparatus according to Constitution 2, wherein the output means (S 145, S 150, S 155, S 160, S 170, S 185, S 190) controls the own vehicle based on the recommended behavior.(Configuration 4) A driving assistance apparatus including the driving assistance apparatus according to Configuration 3, wherein the output means (S 145) allows the own vehicle to travel at a lane change speed equal to or higher than the predetermined vehicle speed until the lane change to the adjacent lane is completed when the recommended behavior of the lane change to the adjacent lane is and the speed of the adjacent vehicle is equal to or higher than the predetermined vehicle speed.(Configuration 5) A driving assistance device including the driving assistance device according to Configuration 4, wherein the lane change speed is equal to or less than a value obtained by adding a predetermined upper limit value to the preset vehicle speed.(Configuration 6) A driving assistance device including the driving assistance device according to Configuration 4 or 5, wherein the output means (S 170) allows the own vehicle to switch the lane to the lane in which the preceding vehicle that has been passed travels when there is a space having a size necessary for the lane change in front of the preceding vehicle that has been passed after performing the lane change.(Configuration 7) A driving assistance apparatus including the driving assistance apparatus according to Configuration 4 or 5, wherein the output means (S 190) changes the predetermined vehicle speed to a speed designated by the driver of the own vehicle when the driver of the own vehicle instructs a change in the predetermined vehicle speed if the space having a size necessary for lane change is present in front of the preceding vehicle that has been passed.(Configuration 8) A driving assistance apparatus including the driving assistance apparatus according to Configuration 7, wherein the output means (S 185) changes the predetermined vehicle speed to the lane change speed after a predetermined period of time has elapsed when the instruction for changing the predetermined vehicle speed is not issued by the driver of the own vehicle.(Configuration 9) A driving assistance apparatus including the driving assistance apparatus according to Configuration 1 or 2, wherein the output device (S 133, S 171) performs control regarding notification to the driver of the own vehicle on the basis of the recommended behavior.[List of Selected Reference Numerals Not Entryable in the Figures]1 Driving assistance system 14 Driving assistance execution device 15 Control device 51 CPU S 110 Speed?Befindet own vehicle in the traveling mode with constant S 126 Is speed of the preceding vehicle ≤ basic preset vehicle speed? S127 There is a predetermined space on adjacent track? S128 There is a neighbouring vehicle? S130 Has adjacent vehicle less speed difference of basic preset vehicle speed? S131 Vehicle Are differences equal and is the speed of the adjacent higher than the predetermined vehicle speed? S135 Actual speed of the adjacent vehicle set to be greater than the vehicle speed in advance? S 145 Perform adjustment of the vehicle speed (vehicle speed after adjustment ≤ preset vehicle speed + α) S 150 Perform adjustment of the vehicle speed by S 161 Perform adjustment of the speed of the own vehicle (speed of the own vehicle = basic preset vehicle speed) S 162 (speed of the vehicle) Perform adjustment of the speed of the own vehicle by the own vehicle = speed of the adjacent S 163 (speed of the vehicle speed Perform adjustment of the speed of the own vehicle by the own vehicle ≤ basic preset + α) S 165 Vehicle? Gives it a preset space before the overtaking preceding S 170 Perform lane change with preset vehicle speed S 175 Vehicle speed Has been obtained from the previous time Driver Issued Instruction? S185 Vehicle speedVorab Festgelegte Festgelegte Vehicle speed=Current S235 Vehicle speed Has input permission of the change of the predetermined driver performed? S245 (speed) Perform adjustment of the speed of the own vehicle by the own vehicle = Basic preset S255 Perform adjustment of the preset speed (preset speed = speed of the own vehicle) S290 Vehicle speed Has input of permission of change of the preset speed performed by the driver? S300 (Perform adjustment of the predetermined vehicle speed by fixed speed = Basic predetermined speed) S305 (Speed Speed) Perform adjustment of the predetermined vehicle speed by the own vehicle = Basic predetermined speed

Claims

A driving assistance apparatus (15) mounted in an own vehicle and performing driving assistance for the own vehicle, the driving assistance apparatus comprising: first determination means (S132, S159) that determines a recommended lane on which the own vehicle is to travel based on a comparison between a predetermined vehicle speed determined in advance to allow the own vehicle to travel at a constant speed, a driving state of a preceding vehicle that travels in front of the own vehicle in a lane on which the own vehicle travels, and a driving state of an adjacent vehicle that travels in front of the own vehicle in an adjacent lane that is adjacent to the lane; An output device (S133, S145, S155, S163, S255, S265, S300) that performs output based on the recommended lane, characterized in that the output device (S145) performs output to allow the own vehicle to travel at a lane change speed equal to or higher than the predetermined vehicle speed until the lane change to the adjacent lane is completed, when the first determination device determines that the recommended lane is the adjacent lane (S132), and the speed of the adjacent vehicle is higher than the predetermined vehicle speed (YES in S135).A driving assistance apparatus (15) mounted in an own vehicle and performing driving assistance for the own vehicle, the driving assistance apparatus comprising: first determination means (S132, S159) that determines a recommended lane on which the own vehicle is to travel based on a comparison between a predetermined vehicle speed determined in advance to allow the own vehicle to travel at a constant speed, a driving state of a preceding vehicle that travels in front of the own vehicle in a lane on which the own vehicle travels, and a driving state of an adjacent vehicle that travels in front of the own vehicle in an adjacent lane that is adjacent to the lane, and output means (S133, S145, S155, S163, S255, S265, S300), which performs output based on the recommended lane, characterized in that the output means (S 163) performs output for allowing the own vehicle to travel at a lane change speed equal to or higher than the predetermined vehicle speed after the lane change to the adjacent lane is completed, if the first determination means determines that the recommended lane is the adjacent lane (S 132) and the speed of the adjacent vehicle is higher than the predetermined vehicle speed (YES in S 135).The driving assistance apparatus (15) according to claim 1 or 2, further comprising: the first determination means (S130, S132, S159) sets, as the recommended lane, a lane in which a vehicle travels at a speed closer to the predetermined vehicle speed, out of a speed of a preceding vehicle ahead of the own vehicle in the lane and a speed of the adjacent preceding vehicle ahead of the own vehicle in the adjacent lane.The driving assistance apparatus (15) according to any one of claims 1 to 3, further comprising: second determination means (S126) that determines whether or not the speed of the preceding vehicle is slower than the predetermined vehicle speed, wherein the first determination means determines the recommended lane based on the determination result of the second determination means.The driving assistance apparatus (15) according to claim 4, further comprising: determination prohibiting means (S129) that prohibits the determination of the recommended lane by the first determining means when the second determining means determines that the speed of the preceding vehicle is greater than the predetermined vehicle speed (NO in S126).The driving assistance apparatus (15) according to any one of claims 4 or 5, further comprising: determination execution means (S126) that allows the first determination means to perform the determination of the recommended lane when the second determination means determines that the speed of the preceding vehicle is equal to or lower than the predetermined vehicle speed (YES in S126).The driving assistance apparatus (15) according to any one of claims 1 to 6, wherein: the output means (S133) performs output to an occupant of the own vehicle that a lane change to the adjacent lane is recommended when the first determination means (S132) determines that the recommended lane is the adjacent lane.The driving assistance apparatus (15) according to any one of claims 1 to 7, wherein: the output means (S155) performs output to perform driving control of the own vehicle to switch to the adjacent lane when the first determination means (S132) determines that the recommended lane is the adjacent lane.The driving assistance device (15) according to any one of claims 1 to 8, wherein: the lane change speed is equal to or less than a value obtained by adding a predetermined upper limit value to the predetermined vehicle speed.The driving assistance apparatus (15) according to any one of claims 3 to 9, wherein: the output means (S255) changes the predetermined vehicle speed when there is an instruction from a driver of the own vehicle regarding the change of the predetermined vehicle speed (YES in S235), if a space predetermined for the change of the own vehicle is not present in an original lane (NO in S220) after a lane change to the adjacent lane has been completed (YES in S215), and the speed of the vehicle traveling in front of the own vehicle is higher than the predetermined vehicle speed (YES in S225).The driving assistance apparatus (15) according to claim 10, wherein: the output means (S300) performs output to allow the own vehicle to change the driving lane to the original driving lane and change the predetermined vehicle speed to the predetermined vehicle speed before the change, if after the change of the predetermined vehicle speed (S255), the space predetermined for the driving lane change by the own vehicle is present in the original driving lane (YES in S220).The driving assistance apparatus (15) according to any one of claims 1 to 11, wherein: the output means (S265) performs output to allow the own vehicle to change the lane to the original lane if, after the lane change to the adjacent lane is completed (YES in S215), the space set in advance for the lane change by the own vehicle is present in the original lane (YES in S220).The driving assistance apparatus (15) according to claim 8, further comprising: third determination means (S166) that determines the driving lane as a recommended driving lane in which the own vehicle has driven before the lane change when the output means performs output for driving control of the own vehicle to change the lane to the adjacent driving lane (YES in S155, S156).A driving assistance method for driving assistance for an own vehicle, the driving assistance method comprising the steps of: determining, by a driving assistance device (15) mounted in a vehicle, a recommended lane in which the own vehicle is to travel based on a comparison of a predetermined vehicle speed set in advance to allow the own vehicle to travel at a constant speed, a traveling state of a preceding vehicle traveling in front of the own vehicle in a lane in which the own vehicle travels, and a traveling state of an adjacent preceding vehicle traveling in front of the own vehicle in an adjacent lane adjacent to the lane; An output by the driving assistance device (15) based on the recommended lane, wherein the driving assistance method further comprises the step of: performing an output to allow the own vehicle to travel at a lane change speed equal to or higher than the predetermined vehicle speed until the lane change to the adjacent lane is completed when it is determined that the recommended lane is the adjacent lane (S132), and the speed of the adjacent vehicle is higher than the predetermined vehicle speed (YES in S135)..A driving assistance method for driving assistance for an own vehicle, the driving assistance method comprising the steps of: determining, by a driving assistance device (15) mounted in a vehicle, a recommended lane in which the own vehicle is to travel based on a comparison of a predetermined vehicle speed set in advance to allow the own vehicle to travel at a constant speed, a traveling state of a preceding vehicle traveling in front of the own vehicle in a lane in which the own vehicle travels, and a traveling state of an adjacent preceding vehicle traveling in front of the own vehicle in an adjacent lane adjacent to the lane; An output by the driving assistance device (15) based on the recommended lane, wherein the driving assistance method further comprises the step of: performing an output to allow the own vehicle to travel at a lane change speed equal to or higher than the predetermined vehicle speed after the lane change to the adjacent lane is completed, when it is determined that the recommended lane is the adjacent lane (S132), and the speed of the adjacent vehicle is higher than the predetermined vehicle speed (YES in S135).

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