Patent Publication Number: US-2022227393-A1

Title: Vehicle control system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of and claims the benefit to U.S. patent application Ser. No. 16/832,705 filed Mar. 27, 2020, which claims the benefit of Japanese Patent Application No. 2019-067652 filed Mar. 29, 2019. Each of these applications are hereby expressly incorporated by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a vehicle control system configured for autonomous driving. 
     BACKGROUND ART 
     According to a known vehicle control system for a shift by wire vehicle, when the shift lever is shifted to the parking position, the hydraulic brake is activated at the same time as setting the transmission range to the parking range. See JP2018-138449A, for instance. In an emergency situation such as when the driver has become unconscious, this prior art allows a passenger (who may be a fellow passenger or the driver) to activate the hydraulic brake by operating the shift level which can be more readily operated by the passenger than the brake pedal so that the vehicle can be brought to a stop with a minimum delay. 
     According to this prior art, the vehicle may come to a stop relatively promptly, but no consideration is made regarding the selection of the position at which the vehicle comes to a stop. If the vehicle comes to a stop in a part of the road which is not visible from approaching vehicles, the vehicle that is brought to a stop in such a place may create a hazardous condition for other vehicles. To overcome such a problem, it has been proposed to use an autonomous driving vehicle which, in an emergency situation, can execute a stop process whereby a relatively safe stop area is determined, and the vehicle is autonomously driven to the stop area to be parked therein. 
     Once the vehicle has come to a stop, the shift position is shifted to the parking position, and the parking brake is engaged while the hydraulic brake is released. As a result, the brake lamp is turned off as soon as the vehicle comes to a stop in the stop area. Therefore, the visibility of the vehicle which has come to a stop to approaching vehicles may be low so that there is a risk that the approaching vehicle may fail to properly avoid the parked vehicle. 
     On the other hand, it is not desirable to keep the hydraulic brake engaged while the vehicle is parked in the emergency situation since the pump for actuating the hydraulic brake is required to be kept in operation while the vehicle is parked, and this involves a significant consumption of electric power. Therefore, if the vehicle is kept parked for a long period of time, the onboard battery may run out, and this not only prevents the brake lamp to be kept turned on, but may also cause an inconvenience for the subsequent rescue effort. 
     SUMMARY OF THE INVENTION 
     In view of such a problem of the prior art, a primary object of the present invention is to provide a vehicle control system configured for autonomous driving which can keep the brake lamp turned on for a long period of time when the vehicle is parked in a stop area as a result of a stop process. 
     To achieve such an object, the present invention provides a vehicle control system ( 1 ,  101 ,  201 ) configured for autonomous driving, comprising: a control unit ( 15 ) for steering, accelerating, and decelerating a vehicle; a brake device ( 4 ) for applying a brake force to the vehicle; and a brake lamp ( 14   a ); wherein the control unit is configured to execute a stop process by which the vehicle is parked in a prescribed stop area when it is detected that the control unit or a driver has become incapable of properly maintaining a traveling state of the vehicle, and a stop maintaining process for keeping the vehicle parked following the vehicle coming to a stop in the stop process, the control unit keeping the brake lamp turned on while the stop maintaining process is being executed. 
     Since the brake lamp is turned on when the vehicle is parked in the stop area, the visibility of the vehicle to approaching vehicles can be increased so that the risk of an accident can be minimized. 
     Preferably, the brake device includes a hydraulic circuit ( 99 ), a brake force applying device ( 84 ) for applying a brake force to a wheel of the vehicle in response to a hydraulic pressure in the hydraulic circuit, and a pressurization/depressurization device ( 84 ) configured to change the hydraulic pressure in the hydraulic circuit. Further, the control unit turns on the brake lamp when the hydraulic pressure is equal to or higher than a first threshold, and turns off the brake lamp when the hydraulic pressure is lower than the first threshold, the control unit being configured to execute a pressurization process to control the pressurization/depressurization device so as to cause the hydraulic pressure to be equal to or higher than the first threshold. 
     Thereby, when the vehicle is parked as a result of the stop process, the control unit causes the hydraulic pressure to be equal to or higher than the first threshold so that the brake lamp lights up. 
     Preferably, the brake force applying device ( 84 ) is configured to apply a brake force to a wheel of the vehicle when the hydraulic pressure in the hydraulic circuit is equal to or higher than a second threshold which is higher than the first threshold, and the control unit is configured to execute the pressurization process to control the pressurization/depressurization device so as to cause the hydraulic pressure to be equal to or higher than the first threshold and lower than the second threshold while the stop maintaining process is being executed. 
     Thus, by selecting the hydraulic pressure to be high enough to turn on the brake lamp, but low enough not to engage the hydraulic brake, the power consumption required to engage the hydraulic brake can be saved while the surrounding vehicles and pedestrians can be properly warned 
     Preferably, the vehicle control system further comprises a driving operation device ( 10 ) configured to receive an operation input from a driver, wherein the control unit maintains the hydraulic pressure to be equal to or higher than the first threshold and lower than the second threshold until an operation input is applied to the driving operation device. 
     Thereby, the surrounding vehicles and pedestrians are properly warned, and once the cause for the stop process is eliminated, the driver or a person taking over the driving can readily drive the vehicle to a desired destination. 
     Preferably, the control unit is configured to execute the pressurization process and a pressure reduction process to control the pressurization/depressurization device ( 83 ) in an intermittent manner so as to cause the hydraulic pressure to alternate between a first value equal to or higher than the first threshold, and a second value lower than the first threshold while the stop maintaining process is being executed. 
     By thus blinking the brake lamp when the vehicle is at a stop as a result of the stop process, the visibility of the vehicle can be enhanced for an increased safety, and the consumption of power can be reduced even further. 
     Preferably, the control unit is configured to execute the pressurization process and a pressure reduction process to control the pressurization/depressurization device ( 83 ) in an intermittent manner so as to cause the hydraulic pressure to alternate between a first value equal to or higher than the first threshold and lower than the second threshold, and a third value lower than the first threshold while the stop maintaining process is being executed. 
     By thus blinking the brake lamp when the vehicle is at a stop as a result of the stop process, the visibility of the vehicle can be enhanced for an increased safety, and the consumption of power can be reduced even further. 
     Preferably, the control unit is configured to shift a shift range of an automatic transmission ( 71 ) of the vehicle to a parking range before turning on the brake lamp in the stop maintain process (ST 11 ). 
     Thereby, the safety of the vehicle after coming to a stop can be increased. 
     Preferably, the control unit is configured to shift a shift range of an automatic transmission ( 71 ) of the vehicle to a parking range, and engage a parking brake device ( 85 ) of the vehicle before turning on the brake lamp in the stop maintain process. 
     Thereby, the safety of the vehicle after coming to a stop can be increased. 
     The present invention thus provides a vehicle control system configured for autonomous driving which can keep the brake lamp turned on for a long period of time when the vehicle is parked in a stop area as a result of a stop process. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING(S) 
         FIG. 1  is a functional block diagram of a vehicle on which a vehicle control system according to the present invention is mounted; 
         FIG. 2  is a flowchart of a stop process; 
         FIG. 3  is a functional block diagram of a brake device; 
         FIG. 4  is a functional block diagram of a hydraulic circuit of the brake device; 
         FIG. 5  is a flow chart of a stop maintaining process according to a first embodiment of the present invention; 
         FIG. 6  is a flow chart of a stop maintaining process according to a second embodiment of the present invention; and 
         FIG. 7  is a flow chart of a stop maintaining process according to a third embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
     A vehicle control system according to a preferred embodiment of the present invention is described in the following with reference to the appended drawings. The following disclosure is according to left-hand traffic. In the case of right-hand traffic, the left and the right in the disclosure will be reversed. 
     As shown in  FIG. 1 , the vehicle control system  1  according to the present invention is a part of a vehicle system  2  mounted on a vehicle. The vehicle system  2  includes a power unit  3 , a brake device  4 , a steering device  5 , an external environment recognition device  6 , a vehicle sensor  7 , a communication device  8 , a navigation device  9  (map device), a driving operation device  10 , an occupant monitoring device  11 , an HMI  12  (Human Machine Interface), an autonomous driving level switch  13 , an external notification device  14 , and a control unit  15 . These components of the vehicle system  2  are connected to one another so that signals can be transmitted between them via a communication means such as CAN  16  (Controller Area Network). 
     The power unit  3  is a device for applying a driving force to the vehicle, and may include a power source and a transmission unit. The power source may consist of an internal combustion engine such as a gasoline engine and a diesel engine, an electric motor or a combination of these. The brake device  4  is a device that applies a brake force to the vehicle, and may include a brake caliper that presses a brake pad against a brake rotor, and an electrically actuated hydraulic cylinder that supplies hydraulic pressure to the brake caliper. The brake device  4  may also include a parking brake device. The steering device  5  is a device for changing a steering angle of the wheels, and may include a rack-and-pinion mechanism that steers the front wheels, and an electric motor that drives the rack-and-pinion mechanism. The power unit  3 , the brake device  4 , and the steering device  5  are controlled by the control unit  15 . 
     The external environment recognition device  6  is a device that detects objects located outside of the vehicle. The external environment recognition device  6  may include a sensor that captures electromagnetic waves or light from around the vehicle to detect objects outside of the vehicle, and may consist of a radar  17 , a lidar  18 , an external camera  19 , or a combination of these. The external environment recognition device  6  may also be configured to detect objects outside of the vehicle by receiving a signal from a source outside of the vehicle. The detection result of the external environment recognition device  6  is forwarded to the control unit  15 . 
     The radar  17  emits radio waves such as millimeter waves to the surrounding area of the vehicle, and detects the position (distance and direction) of an object by capturing the reflected wave. Preferably, the radar  17  includes a front radar that radiates radio waves toward the front of the vehicle, a rear radar that radiates radio waves toward the rear of the vehicle, and a pair of side radars that radiates radio waves in the lateral directions. 
     The lidar  18  emits light such as an infrared ray to the surrounding part of the vehicle, and detects the position (distance and direction) of an object by capturing the reflected light. At least one lidar  18  is provided at a suitable position of the vehicle. 
     The external camera  19  can capture the image of the surrounding objects such as vehicles, pedestrians, guardrails, curbs, walls, median strips, road shapes, road signs, road markings painted on the road, and the like. The external camera  19  may consist of a digital camera using a solid-state imaging device such as a CCD and a CMOS. At least one external camera  19  is provided at a suitable position of the vehicle. The external camera  19  preferably includes a front camera that images the front of the vehicle, a rear camera that images the rear of the vehicle and a pair of side cameras that image the lateral views from the vehicle. The external camera  19  may consist of a stereo camera that can capture a three-dimensional image of the surrounding objects. 
     The vehicle sensor  7  may include a vehicle speed sensor that detects the traveling speed of the vehicle, an acceleration sensor that detects the acceleration of the vehicle, a yaw rate sensor that detects an angular velocity of the vehicle around a vertical axis, a direction sensor that detects the traveling direction of the vehicle, and the like. The yaw rate sensor may consist of a gyro sensor. 
     The communication device  8  allows communication between the control unit  15  which is connected to the navigation device  9  and other vehicles around the own vehicle as well as servers located outside the vehicle. The control unit  15  can perform wireless communication with the surrounding vehicles via the communication device  8 . For instance, the control unit  15  can communicate with a server that provides traffic regulation information via the communication device  8 , and with an emergency call center that accepts an emergency call from the vehicle also via the communication device  8 . Further, the control unit  15  can communicate with a portable terminal carried by a person such as a pedestrian present outside the vehicle via the communication device  8 . 
     The navigation device  9  is able to identify the current position of the vehicle, and performs route guidance to a destination and the like, and may include a GNSS receiver  21 , a map storage unit  22 , a navigation interface  23 , and a route determination unit  24 . The GNSS receiver  21  identifies the position (latitude and longitude) of the vehicle according to a signal received from artificial satellites (positioning satellites). The map storage unit  22  may consist of a per se known storage device such as a flash memory and a hard disk, and stores or retains map information. The navigation interface  23  receives an input of a destination or the like from the user, and provides various information to the user by visual display and/or speech. The navigation interface  23  may include a touch panel display, a speaker, and the like. In another embodiment, the GNSS receiver  21  is configured as a part of the communication device  8 . The map storage unit  22  may be configured as a part of the control unit  15  or may be configured as a part of an external server that can communicate with the control unit  15  via the communication device  8 . 
     The map information may include a wide range of road information which may include, not exclusively, road types such as expressways, toll roads, national roads, and prefectural roads, the number of lanes of the road, road markings such as the center position of each lane (three-dimensional coordinates including longitude, latitude, and height), road division lines and lane lines, the presence or absence of sidewalks, curbs, fences, etc., the locations of intersections, the locations of merging and branching points of lanes, the areas of emergency parking zones, the width of each lane, and traffic signs provided along the roads. The map information may also include traffic regulation information, address information (address/postal code), facility information, telephone number information, and the like. 
     The route determination unit  24  determines a route to the destination according to the position of the vehicle specified by the GNSS receiver  21 , the destination input from the navigation interface  23 , and the map information. When determining the route, in addition to the route, the route determination unit  24  determines the target lane which the vehicle will travel in by referring to the merging and branching points of the lanes in the map information. 
     The driving operation device  10  receives an input operation performed by the driver to control the vehicle. The driving operation device  10  may include a steering wheel, an accelerator pedal, and a brake pedal. Further, the driving operation device  10  may include a shift lever, a parking brake lever, and the like. Each element of the driving operation device  10  is provided with a sensor for detecting an operation amount of the corresponding operation. The driving operation device  10  outputs a signal indicating the operation amount to the control unit  15 . 
     The occupant monitoring device  11  monitors the state of the occupant in the passenger compartment. The occupant monitoring device  11  includes, for example, an internal camera  26  that images an occupant sitting on a seat in the vehicle cabin, and a grip sensor  27  provided on the steering wheel. The internal camera  26  is a digital camera using a solid-state imaging device such as a CCD and a CMOS. The grip sensor  27  is a sensor that detects if the driver is gripping the steering wheel, and outputs the presence or absence of the grip as a detection signal. The grip sensor  27  may be formed of a capacitance sensor or a piezoelectric device provided on the steering wheel. The occupant monitoring device  11  may include a heart rate sensor provided on the steering wheel or the seat, or a seating sensor provided on the seat. In addition, the occupant monitoring device  11  may be a wearable device that is worn by the occupant, and can detect the vital information of the driver including at least one of the heart rate and the blood pressure of the driver. In this conjunction, the occupant monitoring device  11  may be configured to be able to communicate with the control unit  15  via a per se known wireless communication means. The occupant monitoring device  11  outputs the captured image and the detection signal to the control unit  15 . 
     The external notification device  14  is a device for notifying to people outside of the vehicle by sound and/or light, and may include a warning light and a horn. A headlight (front light), a taillight, a brake lamp, a hazard lamp, and a vehicle interior light may function as a warning light. 
     The HMI  12  notifies the occupant of various kinds of information by visual display and speech, and receives an input operation by the occupant. The HMI  12  may include at least one of a display device  31  such as a touch panel and an indicator light including an LCD or an organic EL, a sound generator  32  such as a buzzer and a speaker, and an input interface  33  such as a GUI switch on the touch panel and a mechanical switch. The navigation interface  23  may be configured to function as the HMI  12 . 
     The autonomous driving level switch  13  is a switch that activates autonomous driving as an instruction from the driver. The autonomous driving level switch  13  may be a mechanical switch or a GUI switch displayed on the touch panel, and is positioned in a suitable part of the cabin. The autonomous driving level switch  13  may be formed by the input interface  33  of the HMI  12  or may be formed by the navigation interface  23 . 
     The control unit  15  may consist of an electronic control unit (ECU) including a CPU, a ROM, a RAM, and the like. The control unit  15  executes various types of vehicle control by executing arithmetic processes according to a computer program executed by the CPU. The control unit  15  may be configured as a single piece of hardware, or may be configured as a unit including a plurality of pieces of hardware. In addition, at least a part of each functional unit of the control unit  15  may be realized by hardware such as an LSI, an ASIC, and an FPGA, or may be realized by a combination of software and hardware. 
     The control unit  15  is configured to execute autonomous driving control of at least level 0 to level 3 by combining various types of vehicle control. The level is according to the definition of SAE J3016, and is determined in relation to the degree of machine intervention in the driving operation of the driver and in the monitoring of the surrounding environment of the vehicle. 
     In autonomous driving of level 0, the control unit  15  does not control the vehicle, and the driver performs all of the driving operations. Thus, autonomous driving of level 0 means a manual driving. 
     In autonomous driving of level 1, the control unit  15  executes a certain part of the driving operation, and the driver performs the remaining part of the driving operation. For example, autonomous driving level 1 includes constant speed traveling, inter-vehicle distance control (ACC; Adaptive Cruise Control) and lane keeping assist control (LKAS; Lane Keeping Assistance System). The level 1 autonomous driving is executed when various devices (for example, the external environment recognition device  6  and the vehicle sensor  7 ) required for executing the level 1 autonomous driving are all properly functioning. 
     In autonomous driving of level 2, the control unit  15  performs the entire driving operation. The level 2 autonomous driving is performed only when the driver monitors the surrounding environment of the vehicle, the vehicle is within a designated area, and the various devices required for performing the level 2 autonomous driving are all functioning properly. 
     In level 3 autonomous driving, the control unit  15  performs the entire driving operation. The level 3 autonomous driving requires the driver to monitor or be aware of the surrounding environment when required, and is executed only when the vehicle is within a designated area, and the various devices required for performing the level 3 autonomous driving are all functioning properly. The conditions under which the level 3 autonomous driving is executed may include that the vehicle is traveling on a congested road. Whether the vehicle is traveling on a congested road or not may be determined according to traffic regulation information provided from a server outside of the vehicle, or, alternatively, that the vehicle speed detected by the vehicle speed sensor is determined to be lower than a predetermined slowdown determination value (for example, 30 km/h) over a predetermined time period. 
     Thus, in the autonomous driving of levels 1 to 3, the control unit  15  executes at least one of the steering, the acceleration, the deceleration, and the monitoring of the surrounding environment. When in the autonomous driving mode, the control unit  15  executes the autonomous driving of level 1 to level 3. Hereinafter, the steering, acceleration, and deceleration operations are collectively referred to as driving operation, and the driving and the monitoring of the surrounding environment may be collectively referred to as driving. 
     In the present embodiment, when the control unit  15  has received an instruction to execute autonomous driving via the autonomous driving level switch  13 , the control unit  15  selects the autonomous driving level that is suitable for the environment of the vehicle according to the detection result of the external environment recognition device  6  and the position of the vehicle acquired by the navigation device  9 , and changes the autonomous driving level as required. However, the control unit  15  may also change the autonomous driving level according the input to the autonomous driving level switch  13 . 
     As shown in  FIG. 1 , the control unit  15  includes an autonomous driving control unit  35 , an abnormal state determination unit  36 , a state management unit  37 , a travel control unit  38 , and a storage unit  39 . 
     The autonomous driving control unit  35  includes an external environment recognition unit  40 , a vehicle position recognition unit  41 , and an action plan unit  42 . The external environment recognition unit  40  recognizes an obstacle located around the vehicle, the shape of the road, the presence or absence of a sidewalk, and road signs according to the detection result of the external environment recognition device  6 . The obstacles include, not exclusively, guardrails, telephone poles, surrounding vehicles, and pedestrians. The external environment recognition unit  40  can acquire the state of the surrounding vehicles, such as the position, speed, and acceleration of each surrounding vehicle from the detection result of the external environment recognition device  6 . The position of each surrounding vehicle may be recognized as a representative point such as a center of gravity position or a corner positions of the surrounding vehicle, or an area represented by the contour of the surrounding vehicle. 
     The vehicle position recognition unit  41  recognizes a traveling lane, which is a lane in which the vehicle is traveling, and a relative position and an angle of the vehicle with respect to the traveling lane. The vehicle position recognition unit  41  may recognize the traveling lane according to the map information stored in the map storage unit  22  and the position of the vehicle acquired by the GNSS receiver  21 . In addition, the lane markings drawn on the road surface around the vehicle may be extracted from the map information, and the relative position and angle of the vehicle with respect to the traveling lane may be recognized by comparing the extracted lane markings with the lane markings captured by the external camera  19 . 
     The action plan unit  42  sequentially creates an action plan for driving the vehicle along the route. More specifically, the action plan unit  42  first determines a set of events for traveling on the target lane determined by the route determination unit  24  without the vehicle coming into contact with an obstacle. The events may include a constant speed traveling event in which the vehicle travels in the same lane at a constant speed, a preceding vehicle following event in which the vehicle follows a preceding vehicle at a certain speed which is equal to or lower than a speed selected by the driver or a speed which is determined by the prevailing environment, a lane changing event in which the vehicle change lanes, a passing event in which the vehicle passes a preceding vehicle, a merging event in which the vehicle merge into the traffic from another road at a junction of the road, a diverging event in which the vehicle travels into a selected road at a junction of the road, an autonomous driving end event in which autonomous driving is ended, and the driver takes over the driving operation, and a stop event in which the vehicle is brought to a stop when a certain condition is met, the condition including a case where the control unit  15  or the driver has become incapable of continuing the driving operation. 
     The conditions under which the action plan unit  42  invokes the stop event include the case where an input to the internal camera  26 , the grip sensor  27 , or the autonomous driving level switch  13  in response to an intervention request (a hand-over request) to the driver is not detected during autonomous driving. The intervention request is a warning to the driver to take over a part of the driving, and to perform at least one of the driving operation and the monitoring of the environment corresponding to the part of the driving that is to be handed over. The condition under which the action plan unit  42  invokes the stop even include the case where the action plan unit  42  has detected that the driver has become incapable of performing the driving while the vehicle is traveling due to a physiological ailment according to the signal from a pulse sensor, the internal camera or the like. 
     During the execution of these events, the action plan unit  42  may invoke an avoidance event for avoiding an obstacle or the like according to the surrounding conditions of the vehicle (existence of nearby vehicles and pedestrians, lane narrowing due to road construction, etc.). 
     The action plan unit  42  generates a target trajectory for the vehicle to travel in the future corresponding to the selected event. The target trajectory is obtained by sequentially arranging trajectory points that the vehicle should trace at each time point. The action plan unit  42  may generate the target trajectory according to the target speed and the target acceleration set for each event. At this time, the information on the target speed and the target acceleration is determined for each interval between the trajectory points. 
     The travel control unit  38  controls the power unit  3 , the brake device  4 , and the steering device  5  so that the vehicle traces the target trajectory generated by the action plan unit  42  according to the schedule also generated by the action plan unit  42 . 
     The storage unit  39  is formed by a ROM, a RAM, or the like, and stores information required for the processing by the autonomous driving control unit  35 , the abnormal state determination unit  36 , the state management unit  37 , and the travel control unit  38 . 
     The abnormal state determination unit  36  includes a vehicle state determination unit  51  and an occupant state determination unit  52 . The vehicle state determination unit  51  analyzes signals from various devices (for example, the external environment recognition device  6  and the vehicle sensor  7 ) that affect the level of the autonomous driving that is being executed, and detects the occurrence of an abnormality in any of the devices and units that may prevent a proper execution of the autonomous driving of the level that is being executed. 
     The occupant state determination unit  52  determines if the driver is in an abnormal state or not according to a signal from the occupant monitoring device  11 . The abnormal state includes the case where the driver is unable to properly steer the vehicle in autonomous driving of level 1 or lower that requires the driver to steer the vehicle. That the driver is unable to steer the vehicle in autonomous driving of level 1 or lower could mean that the driver is not holding the steering wheel, the driver is asleep, the driver is incapacitated or unconscious due to illness or injury, or the driver is under a cardiac arrest. The occupant state determination unit  52  determines that the driver is in an abnormal state when there is no input to the grip sensor  27  from the driver while in autonomous driving of level 1 or lower that requires the driver to steer the vehicle. Further, the occupant state determination unit  52  may determine the open/closed state of the driver&#39;s eyelids from the face image of the driver that is extracted from the output of the internal camera  26 . The occupant state determination unit  52  may determine that the driver is asleep, under a strong drowsiness, unconscious or under a cardiac arrest so that the drive is unable to properly drive the vehicle, and the driver is in an abnormal condition when the driver&#39;s eyelids are closed for more than a predetermined time period, or when the number of times the eyelids are closed per unit time interval is equal to or greater than a predetermined threshold value. The occupant state determination unit  52  may further acquire the driver&#39;s posture from the captured image to determine that the driver&#39;s posture is not suitable for the driving operation or that the posture of the driver does not change for a predetermined time period. It may well mean that the driver is incapacitated due to illness or injury, and in an abnormal condition. 
     In the case of autonomous driving of level 2 or lower, the abnormal condition includes a situation where the driver is neglecting the duty to monitor the environment surrounding the vehicle. This situation may include either the case where the driver is not holding or gripping the steering wheel or the case where the driver&#39;s line of sight is not directed in the forward direction. The occupant state determination unit  52  may detect the abnormal condition where the driver is neglecting to monitor the environment surrounding the vehicle when the output signal of the grip sensor  27  indicates that the driver is not holding the steering wheel. The occupant state determination unit  52  may detect the abnormal condition according to the image captured by the internal camera  26 . The occupant state determination unit  52  may use a per se known image analysis technique to extract the face region of the driver from the captured image, and then extracts the iris parts (hereinafter, iris) including the inner and outer corners of the eyes and pupils from the extracted face area. The occupant state determination unit  52  may detect the driver&#39;s line of sight according to the positions of the inner and outer corners of the eyes, the iris, the outline of the iris, and the like. It is determined that the driver is neglecting the duty to monitor the environment surrounding the vehicle when the driver&#39;s line of sight is not directed in the forward direction. 
     In addition, in the autonomous driving at a level where the drive is not required to monitor the surrounding environment or in the autonomous driving of level 3, an abnormal condition refers to a state in which the driver cannot promptly take over the driving when a driving takeover request is issued to the driver. The state where the driver cannot take over the driving includes the state where the system cannot be monitored, or, in other words, where the driver cannot monitor a screen display that may be showing an alarm display such as when the driver is asleep, and when the driver is not looking ahead. In the present embodiment, in the level 3 autonomous driving, the abnormal condition includes a case where the driver cannot perform the duty of monitoring the surrounding environment of the vehicle even though the driver is notified to monitor the surrounding environment of the vehicle. In the present embodiment, the occupant state determination unit  52  displays a predetermined screen on the display device  31  of the HMI  12 , and instructs the driver to look at the display device  31 . Thereafter, the occupant state determination unit  52  detects the driver&#39;s line of sight with the internal camera  26 , and determines that the driver is unable to fulfill the duty of monitoring the surrounding environment of the vehicle if driver&#39;s line of sight is not facing the display device  31  of the HMI  12 . 
     The occupant state determination unit  52  may detect if the driver is gripping the steering wheel according to the signal from the grip sensor  27 , and if the driver is not gripping the steering wheel, it can be determined that the vehicle is in an abnormal state in which the duty of monitoring the surrounding environment the vehicle is being neglected. Further, the occupant state determination unit  52  determines if the driver is in an abnormal state according to the image captured by the internal camera  26 . For example, the occupant state determination unit  52  extracts a driver&#39;s face region from the captured image by using a per se known image analysis means. The occupant state determination unit  52  may further extract iris parts (hereinafter, iris) of the driver including the inner and outer corners of the eyes and pupils from the extracted face area. The occupant state determination unit  52  obtains the driver&#39;s line of sight according to the extracted positions of the inner and outer corners of the eyes, the iris, the outline of the iris, and the like. It is determined that the driver is neglecting the duty to monitor the environment surrounding the vehicle when the driver&#39;s line of sight is not directed in the forward direction. 
     The state management unit  37  selects the level of the autonomous driving according to at least one of the own vehicle position, the operation of the autonomous driving level switch  13 , and the determination result of the abnormal state determination unit  36 . Further, the state management unit  37  controls the action plan unit  42  according to the selected autonomous driving level, thereby performing the autonomous driving according to the selected autonomous driving level. For example, when the state management unit  37  has selected the level 1 autonomous driving, and a constant speed traveling control is being executed, the event to be determined by the action plan unit  42  is limited only to the constant speed traveling event. 
     The state management unit  37  raises and lowers the autonomous driving level as required in addition to executing the autonomous driving according to the selected level. 
     More specifically, the state management unit  37  raises the level when the condition for executing the autonomous driving at the selected level is met, and an instruction to raise the level of the autonomous driving is input to the autonomous driving level switch  13 . 
     When the condition for executing the autonomous driving of the current level ceases to be satisfied, or when an instruction to lower the level of the autonomous driving is input to the autonomous driving level switch  13 , the state management unit  37  executes an intervention request process. In the intervention request process, the state management unit  37  first notifies the driver of a handover request. The notification to the driver may be made by displaying a message or image on the display device  31  or generating a speech or an acoustic notification from the sound generator  32 . The notification to the driver may continue for a predetermined period of time after the intervention request process is started or may be continued until an input is detected by the occupant monitoring device  11 . 
     The condition for executing the autonomous driving of the current level ceases to be satisfied when the vehicle has moved to an area where only the autonomous driving of a level lower than the current level is permitted, or when the abnormal state determination unit  36  has determined that an abnormal condition that prevents the continuation of the autonomous driving of the current level has occurred to the driver or the vehicle. 
     Following the notification to the driver, the state management unit  37  detects if the internal camera  26  or the grip sensor  27  has received an input from the driver indicating a takeover of the driving. The detection of the presence or absence of an input to take over the driving is determined in a way that depends on the level that is to be selected. When moving to level 2, the state management unit  37  extracts the driver&#39;s line of sight from the image acquired by the internal camera  26 , and when the driver&#39;s line of sight is facing the front of the vehicle, it is determined that an input indicating the takeover of the driving by the driver is received. When moving to level 1 or level 0, the state management unit  37  determines that there is an input indicating an intent to take over the driving when the grip sensor  27  has detected the gripping of the steering wheel by the driver. Thus, the internal camera  26  and the grip sensor  27  function as an intervention detection device that detects an intervention of the driver to the driving. Further, the state management unit  37  may detect if there is an input indicating an intervention of the driver to the driving according to the input to the autonomous driving level switch  13 . 
     The state management unit  37  lowers the autonomous driving level when an input indicating an intervention to the driving is detected within a predetermined period of time from the start of the intervention request process. At this time, the level of the autonomous driving after the lowering of the level may be level 0, or may be the highest level that can be executed. 
     The state management unit  37  causes the action plan unit  42  to generate a stop event when an input corresponding to the driver&#39;s intervention to the driving is not detected within a predetermined period of time after the execution of the intervention request process. The stop event is an event in which the vehicle is brought to a stop at a safe position (for example, an emergency parking zone, a roadside zone, a roadside shoulder, a parking area, etc.) while the vehicle control is degenerated. Here, a series of procedures executed in the stop event may be referred to as MRM (Minimum Risk Maneuver). 
     When the stop event is invoked, the control unit  15  shifts from the autonomous driving mode to the autonomous stopping mode, and the action plan unit  42  executes the stop process. Hereinafter, an outline of the stop process is described with reference to the flowchart of  FIG. 2 . 
     In the stop process, a notification process is first executed (step ST 1 ). In the notification process, the action plan unit  42  operates the external notification device  14  to notify the people outside of the vehicle. For example, the action plan unit  42  activates a horn included in the external notification device  14  to periodically generate an acoustic notification. The notification process continues until the stop process ends. After the notification process has ended, the action plan unit  42  may continue to activate the horn to generate an acoustic notification depending on the situation. 
     Then, a degeneration process is executed (step ST 2 ). The degeneration process is a process of restricting events that can be invoked by the action plan unit  42 . The degeneration process may prohibit a lane change event to a passing lane, a passing event, a merging event, and the like. Further, in the degeneration process, the speed upper limit and the acceleration upper limit of the vehicle may be more limited in the respective events as compared with the case where the stop process is not performed. 
     Next, a stop area determination process is executed (step ST 3 ). The stop area determination process refers to the map information according to the current position of the own vehicle, and extracts a plurality of available stop areas (candidates for the stop area or potential stop areas) suitable for stopping, such as road shoulders and evacuation spaces in the traveling direction of the own vehicle. Then, one of the available stop areas is selected as the stop area by taking into account the size of the stop area, the distance to the stop area, and the like. 
     Next, a moving process is executed (step ST 4 ). In the moving process, a route for reaching the stop area is determined, various events along the route leading to the stop area are generated, and a target trajectory is determined. The travel control unit  38  controls the power unit  3 , the brake device  4 , and the steering device  5  according to the target trajectory determined by the action plan unit  42 . The vehicle then travels along the route and reaches the stop area. 
     Next, a stop position determination process is executed (step ST 5 ). In the stop position determination process, the stop position is determined according to obstacles, road markings, and other objects located around the vehicle recognized by the external environment recognition unit  40 . In the stop position determination process, it is possible that the stop position cannot be determined in the stop area due to the presence of surrounding vehicles and obstacles. When the stop position cannot be determined in the stop position determination process (No in step ST 6 ), the stop area determination process (step ST 3 ), the movement process (step ST 4 ), and the stop position determination process (step ST 5 ) are sequentially repeated. 
     If the stop position can be determined in the stop position determination process (Yes in step ST 6 ), a stop execution process is executed (step ST 7 ). In the stop execution process, the action plan unit  42  generates a target trajectory according to the current position of the vehicle and the targeted stop position. The travel control unit  38  controls the power unit  3 , the brake device  4 , and the steering device  5  according to the target trajectory determined by the action plan unit  42 . The vehicle then moves toward the stop position and stops at the stop position. 
     After the stop execution process is executed, a stop maintaining process is executed (step ST 8 ). In the stop maintaining process, the travel control unit  38  drives the parking brake device according to a command from the action plan unit  42  to maintain the vehicle at the stop position. Thereafter, the action plan unit  42  may transmit an emergency call to the emergency call center by the communication device  8 . When the stop maintaining process is completed, the stop process ends. 
     The vehicle control system  1  is provided with the brake device  4 , the power unit  3 , the external notification device  14 , the control unit  15 , and the driving operation device  10  as discussed earlier. In this embodiment, as shown in  FIGS. 1 and 3 , the vehicle control system  1  includes a brake lamp  14   a  as a part of the external notification device  14 , and turns on the brake lamp  14   a  after the vehicle has come to a stop until the stop process is ended. For this purpose, the vehicle control system  1  is provided with an oil pressure sensor  59  that detects the oil pressure applied to the brake device  4 . 
     The brake device  4  includes a hydraulic brake device  81  and a parking brake device  85 . The hydraulic brake device  81  includes a brake actuator  82  that converts an input from the control unit  15  or the driving operation device  10  (a brake pedal  89 ) into a hydraulic pressure and applies a brake force according to the hydraulic pressure value to the wheels. The control unit  15  further includes a brake actuator control unit  62  that controls the brake actuator  82  and a parking brake control unit  63  that controls the parking brake device  85 . The control unit  15  turns on the brake lamp  14   a  according to the hydraulic pressure detected by the oil pressure sensor  59 . 
     As shown in  FIGS. 3 and 4 , the brake actuator  82  includes a brake force applying device  84  that actuates the brake caliper so as to press a brake pad against a brake disk of each wheel, and a pressurizing/depressurizing device  83 . The pressurizing/depressurizing device  83  includes a master cylinder  91 , a retaining solenoid valve  92 , a pressure reducing solenoid valve  93 , a reservoir tank  94 , and a pump  95 . The master cylinder  91 , the retaining solenoid valve  92 , the pressure reducing solenoid valve  93 , the brake force applying device  84 , and the pump  95  are connected by piping which is filled with brake oil to form a hydraulic circuit  99 . Thus, the brake device  4  includes the hydraulic circuit  99 , the brake force applying device  84 , and the pressurizing/depressurizing device  83 . 
     As shown in  FIG. 4 , the master cylinder  91  is provided with a piston  96 , and the piston  96  is connected to the brake pedal  89 . When the driver depresses the brake pedal  89 , the piston  96  in the master cylinder  91  moves so that a pressure is generated in the master cylinder  91 , and is applied to a brake actuator  82  of the brake caliper. 
     The brake force applying device  84  is connected to the master cylinder  91  via a part of the piping which is provided with a cut valve  97 . 
     The retaining solenoid valve  92  is provided in a part of the piping connecting the brake force applying device  84  with the cut valve  97 . Thus, the brake force applying device  84  and the master cylinder  91  are connected to each other via the cut valve  97  and the retaining solenoid valve  92 . 
     The pressure reducing solenoid valve  93  is provided between the reservoir tank  94  and a part of the piping connecting the brake force applying device  84  with the retaining solenoid valve  92 . Thus, the brake force applying device  84  and the reservoir tank  94  are connected to each other via the pressure reducing solenoid valve  93 . 
     The pump  95  is provided between the reservoir tank  94  and a part of the piping connecting the retaining solenoid valve  92  with the cut valve  97 . The pump  95  circulates the brake oil in the reservoir tank  94  to the part of the piping connecting the retaining solenoid valve  92  with the cut valve  97 . The pump  95  is provided with a check valve so that the brake oil is prevented from flowing backward from the part of the piping connecting the pressure reducing solenoid valve  93  with the reservoir tank  94  to the part of the piping connecting the cut valve  97  with the retaining solenoid valve  92 . 
     The oil pressure sensor  59  is provided in a part of the piping connecting brake force applying device  84  with the retaining solenoid valve  92 , and detects a hydraulic pressure of the oil in a part of the piping connecting the brake force applying device  84  with the retaining solenoid valve  92 . The oil pressure sensor  59  forwards the detected oil pressure value to the control unit  15 . 
     The brake actuator control unit  62  controls the retaining solenoid valve  92 , the pressure reducing solenoid valve  93 , and the pump  95  according to the signal from the oil pressure sensor  59 , and adjusts the oil pressure value in the part of the piping connecting the retaining solenoid valve  92  with the brake force applying device  84 . In the present embodiment, the brake actuator  82  can set the oil pressure value in the part of the piping connecting the retaining solenoid valve  92  with the brake force applying device  84  to the oil pressure value commanded by the action plan unit  42 . The action plan unit  42  in particular turns on the brake lamp  14   a  via the external notification control unit  64  when the oil pressure value is equal to or higher than a first threshold as will be discussed hereinafter. 
     For example, when the brake actuator control unit  62  opens the cut valve  97  and the retaining solenoid valve  92  and closes the pressure reducing solenoid valve  93 , the connection between the master cylinder  91  and the brake force applying device  84  is established while the connection between the reservoir tank  94  and the piping between the master cylinder  91  and the brake force applying device  84  is cut. When the driver steps on the brake pedal  89 , the piston  96  is pushed into the master cylinder  91 , and the hydraulic pressure in the master cylinder  91  increases. The hydraulic pressure produced in the master cylinder  91  is transmitted to the brake force applying device  84 . As a result, the brake pad is pressed against the brake disk in each of the wheels, and a brake force is applied to the wheels. Further, when the oil pressure in the piping connecting the brake force applying device  84  with the retaining solenoid valve  92  becomes equal to or higher than an oil pressure threshold (first threshold), the brake lamp  14   a  is turned on. 
     Similarly, when the brake actuator control unit  62  closes the cut valve  97 , opens the retaining solenoid valve  92 , closes the pressure reducing solenoid valve  93 , and drives the pump  95 , the oil in the piping connecting the brake force applying device  84  with the cut valve  97  is pressurized by the pump  95 . As a result, the brake pad is pressed against the brake disk in each of the wheels, and a brake force is applied to the wheels. Further, when the oil pressure in the piping connecting the brake force applying device  84  with the retaining solenoid valve  92  becomes equal to or higher than the oil pressure threshold (first threshold), the brake lamp  14   a  is turned on. 
     When the brake actuator control unit  62  closes the cut valve  97 , closes the retaining solenoid valve  92 , and opens the pressure reducing solenoid valve  93 , the oil in the piping between the retaining solenoid valve  92  and the brake force applying device  84  flows into the reservoir tank  94 , and the oil in the piping between the retaining solenoid valve  92  and the brake force applying device  84  is depressurized. When the pressure in the piping between the retaining solenoid valve  92  and brake force applying device  84  becomes lower than the oil pressure threshold (first threshold), the brake lamp  14   a  turns off 
     As shown in  FIG. 1 , the power unit  3  includes an automatic transmission  71 . The automatic transmission  71  may be a continuously variable transmission or a step-wise automatic transmission. In either case, the automatic transmission  71  is provided with a shift actuator  72 . The shift actuator  72 , either manually or under command from the control unit  15 , selects a shift position from a drive range (D range), a neutral range (N range), a parking range (P range), and a reverse range (R range). In particular, the action plan unit  42  switches the shift range according to the manual operation of the driver during manual driving, and automatically transmits a signal to the automatic transmission  71  to change the shift range as required in autonomous driving. 
     The parking brake device  85  is a device for frictionally holding the wheels when the vehicle is at a stop. In the present embodiment, the parking brake device  85  holds the rear wheels by pressing a brake pad on a brake drum provided on each rear wheel. The parking brake device  85  may be manually engaged by the driver, and may also be engaged under the command from the parking brake control unit  63 . For example, when there is an input from the driver to the parking switch during manual driving, the action plan unit  42  drives the parking brake device  85  to hold the rear wheels. In autonomous driving, the action plan unit  42  drives the parking brake device  85  as needed to hold the rear wheels. 
     The external notification device  14  is a device that notifies the outside of the vehicle by light and/or sound. The external notification device  14  includes a hazard lamp  14   b,  and a horn  14   c  in addition to the brake lamp  14   a.  The control unit  15  further includes an external notification control unit  64  that controls the external notification device  14 . The external notification control unit  64  performs the notification via the external notification device  14  by controlling the voltage applied to the external notification device  14  according to the signal from the action plan unit  42 . The notification by the hazard lamp  14   b  and the horn  14   c  may be continuously performed before the vehicle comes to a stop in the stop process (typically as soon as the stop process is initiated). 
     With reference to  FIG. 5 , details of the stop maintaining process executed by the action plan unit  42  to turn on the brake lamp  14   a  even after the vehicle has come to a stop will be described. 
     In the first step ST 11  of the stop maintaining process, the action plan unit  42  drives the shift actuator  72  to set the shift range of the automatic transmission  71  to the parking range. After the shift range of the automatic transmission  71  is set to the parking range, the action plan unit  42  executes step ST 12 . 
     In step ST 12 , the action plan unit  42  transmits a signal instructing the parking brake control unit  63  to engage the parking brake. When the transmission of the signal is completed, the action plan unit  42  executes step ST 13 . 
     In step ST 13 , the action plan unit  42  commands the brake actuator control unit  62  to control the brake actuator  82  so that the oil pressure value acquired by the oil pressure sensor  59  becomes a first oil pressure value (pressurization process). When the hydraulic pressure value acquired by the oil pressure sensor  59  becomes the first hydraulic pressure value, the action plan unit  42  executes step ST 14 . The first oil pressure value is set to a predetermined value equal to or higher than an oil pressure threshold. In the present embodiment, the first oil pressure value is equal to the oil pressure threshold. 
     In step ST 14 , the action plan unit  42  executes step ST 13  when it is determined that there is no prescribed input to the driving operation device  10 , and executes step ST 15  when there is a prescribed input to the driving operation device  10 . 
     In step ST 15 , the action plan unit  42  transmits a signal commanding the external notification control unit  64  to end the notification by the external notification device  14 . When the transmission of the signal is completed, the action plan unit  42  ends the stop maintaining process. 
     The mode of operation of the thus configured vehicle control system  1  is discussed in the following. 
     In the vehicle control system  1  according to the present embodiment, after the vehicle has come to a stop in the stop process, the action plan unit  42  executes the stop maintaining process. At this time, the action plan unit  42  first sets the shift range of the automatic transmission  71  to the parking range (ST 11 ), and engages the parking brake device  85  (ST 12 ). Thereafter, the action plan unit  42  drives the brake actuator  82  to perform a pressurization process, and sets a hydraulic pressure value applied to the brake force applying device  84  to the first hydraulic pressure value (ST 13 ). As a result, a brake force is applied to the wheels by the brake force applying device  84 , and the brake lamp  14   a  is turned on. Thereafter, the hydraulic pressure value is maintained at the first hydraulic pressure value until a prescribed operation input is applied to the driving operation device  10  (ST 14 ). When a driving operation input is received, the action plan unit  42  ends the notification by the external notification device  14  (ST 15 ). 
     The advantages of the vehicle control system  1  of this embodiment are discussed in the following. The brake lamp  14   a  is not turned on by engaging the parking brake device  85 . Therefore, if only the parking brake device  85  is engaged when the vehicle is parked in an emergency situation, the brake lamp  14   a  is not turned on, and the surrounding vehicles and pedestrians may not be appropriately warned of the emergency situation or the presence of the parked vehicle. 
     In this embodiment, even when the vehicle is at a stop, and the parking brake device  85  is operated (while the hydraulic brake device  81  is not engaged), the brake oil in the piping of the hydraulic circuit  99  is pressurized such that the oil pressure value becomes equal to or higher than the first oil pressure threshold. As a result, the brake lamp  14   a  is turned on so that the surrounding vehicles and pedestrians are enabled to readily recognize that the vehicle is parked. This allows the other vehicles approaching the parked vehicle to avoid the parked vehicle, and/or allows the occupants of other vehicles and pedestrian to become aware of the emergency situation. 
     The brake oil in the hydraulic circuit  99  is pressurized by the pump  95 . At this time, driving of the pump  95  consumes power of the battery mounted on the vehicle. In the present embodiment, the oil pressure in the piping is maintained is equal to or higher than the first threshold so that the brake lamp  14   a  is turned on, but is lower than a second threshold so that the hydraulic brake device  81  is not engaged, and the consumption of power by the pump  95  is relatively low. Thus, the brake oil is not pressurized by the pump  95  more than necessary to light the brake lamp  14   a  so that the power consumption by the pump  95  is reduced. As a result, the power consumption of the battery required for lighting the brake lamp  14   a  is reduced, and after the vehicle has come to a stop, the brake lamp  14   a  can be kept turned on for a long period of time to notify the outside of the vehicle that the vehicle is kept parked under an emergency situation. 
     Second Embodiment 
     A vehicle control system  101  according to a second embodiment of the present invention is described in the following with reference to  FIG. 6 . The vehicle control system  101  of the second embodiment is different from the vehicle control system  1  of the first embodiment in that step ST 21  is performed between step ST 13  and step ST 14  shown in  FIG. 5 . The second embodiment is otherwise similar to the first embodiment. Therefore, only step ST 21  is described in detail, and the remaining part of the vehicle control system  101  is omitted from the following description. In the following description, the parts common to the first embodiment are denoted by the same reference numerals. 
     In step ST 21 , the action plan unit  42  drives the brake actuator  82 , and controls the brake actuator  82  so that the oil pressure value acquired by the oil pressure sensor  59  becomes a third oil pressure value (pressure reduction process). The third oil pressure value is lower than the first oil pressure value, and is therefore lower than the threshold value at which the brake lamp  14   a  is turned on. When the hydraulic pressure value acquired by the oil pressure sensor  59  becomes the third hydraulic pressure value, the action plan unit  42  executes step ST 14 . 
     The mode of operation and advantages of the vehicle control system  101  of the second embodiment are discussed in the following. 
     In the stop process, once the vehicle comes to a stop, the action plan unit  42  executes the stop maintaining processing. At this time, similarly to the first embodiment, the action plan unit  42  executes the pressurization process (ST 13 ) and turns on the brake lamp  14   a.  Thereafter, the action plan unit  42  performs a pressure reduction process for setting the oil pressure value acquired by the oil pressure sensor  59  to be lower than the first threshold (ST 21 ). As a result, the oil pressure value becomes lower than the first threshold value for turning on the brake lamp  14   a,  and the brake lamp  14   a  is turned off 
     Further, in the present embodiment, the pressurizing process and the depressurizing process are repeatedly executed until a prescribed operation input is applied to the driving operation device  10 . As a result, the brake lamp  14   a  blinks. This makes it easier for the surrounding vehicles and pedestrians to recognized that the vehicle in an emergency situation is parked, as compared to the case where the brake lamp  14   a  is kept turned off or kept turned on, so that the safety of the vehicle is further enhanced. 
     In addition, as compared to the case where the pressurizing process is continuously performed as in the first embodiment, the power consumption of the pump  95  can be further reduced. Therefore, the brake lamp  14   a  can be kept blinking for a long period of the time for the given capacity of the onboard battery. 
     Third Embodiment 
     A vehicle control system  201  according to a third embodiment of the present invention is described in the following with reference to  FIG. 7 . The vehicle control system  201  of the third embodiment differs from the vehicle control system  1  of the first embodiment in that the action plan unit  42  executes step ST 31  in the stop maintaining process, instead of step ST 13  shown in  FIG. 5 . In step ST 31 , the control unit  15  commands the external notification control unit  64  to turn on the brake lamp  14   a.  The third embodiment is otherwise similar to the first embodiment. Hereinafter, only step ST 31  is described in detail, and the remaining part of the vehicle control system  201  is omitted from the following description. In the following description, the parts common to the first embodiment are denoted by the same reference numerals. 
     In step ST 31 , the action plan unit  42  transmits a signal to command to the external notification control unit  64  to turn on the brake lamp  14   a.  In this case, the brake lamp  14   a  is turned on without regard to the hydraulic pressure in the hydraulic circuit. When the transmission of the signal is completed, the action plan unit  42  executes step ST 14 . 
     The mode of operation and the advantages of the vehicle control system  201  of the third embodiment are discussed in the following. 
     When the vehicle has come to a stop in the stop process, the action plan unit  42  executes the stop maintaining process. After engaging the parking brake device  85 , the action plan unit  42  commands the external notification control unit  64  to turn on the brake lamp  14   a.  As a result, the brake lamp  14   a  is turned on and kept turned on regardless of the oil pressure value. The brake lamp  14   a  can be turned on without requiring to driving the pump  95  or pressurizing the hydraulic circuit as opposed to the first and second embodiments so that the overall structure can be simplified, and energy consumption can be minimized even further. 
     The present invention has been described in terms of specific embodiments, but is not limited by such embodiment, but can be modified in various ways without departing from the scope of the present invention. In the foregoing embodiments, the control of the hydraulic pressure (the pressurizing process and the depressurizing process) is performed until the driver&#39;s operation input is received, but the present invention is not limited to this mode. For example, the vehicle sensor may include a sensor that detects the opening and closing of the door in the vehicle, and the action plan unit  42  may end the control of the hydraulic pressure upon detecting that the door is opened according to the detection result of the sensor. 
     Also, in the foregoing embodiments, the vehicle control system ( 1 ,  101 ,  201 ) had a hydraulic circuit for actuating the hydraulic brake device  81 , but the present invention is not limited to this mode. For example, the brake device  4  may be provided with an electrically actuated brake device, and the control unit  15  may be configured to turn on the brake lamp  14   a  when the electrically actuated brake device is engaged.