Patent Publication Number: US-11027722-B2

Title: Yeilding action assistance system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. application Ser. No. 15/968,208 filed May 1, 2018, which claims the benefit of Japanese Patent Application No. 2017-100261 filed May 19, 2017, the entire disclosure of which each of which are incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     Field of the Disclosure 
     Embodiments of the present application relate to the art of a yielding action assistance system for assisting a vehicle to yield to an emergency vehicle. 
     Discussion of the Related Art 
     Following prior art documents describe vehicle guiding systems for sending information about an emergency vehicle to a vehicle to clear the way for the emergency vehicle. 
     JP-A-2014-154128 describes an emergency vehicle passage support system configured to allow an emergency vehicle pass in a preferential manner. Specifically, the support system taught by JP-A-2014-154128 is configured to guide other vehicle automatically to a shoulder of a road and then stop the other vehicle, in the event that the emergency vehicle approaches. The support system taught by JP-A-2014-154128 is further configured to change the traffic light to green when the emergency vehicle approaches an intersection. 
     JP-A-2011-79388 describes a control device for vehicle configured to detect the approach of an emergency vehicle by inter-vehicle communication, and to restrict a vehicle speed by adjusting a reaction force against a pedal force applied to an accelerator pedal, when the vehicle speed is higher than a predetermined level in the event that the emergency vehicle approaches. 
     JP-A-2008-84004 also describes a vehicle driving support system configured to detect the approach of an emergency vehicle by inter-vehicle communication. The vehicle driving support system taught by JP-A-2008-84004 is further configured to provide different information with a driver by alarm or the like, depending on whether or not the driver takes a yielding action in the event that the emergency vehicle approaches. 
     JP-A-2005-228111 describes a vehicle retreat instruction device configured to instruct vehicles running on a same lane with an emergency vehicle to take a yielding action in order to allow the emergency vehicle to pass. Specifically, the instruction device taught by JP-A-2005-228111 is configured to specify the vehicles travelling on an expected route of the emergency vehicle, and to determine contents of the yielding action to be taken by the vehicles to allow the emergency vehicle to pass. 
     JP-A-2006-184213 describes a route search system for emergency vehicle configured to search a route for the emergency vehicle from a start point to a destination taking account of a road width. Further, JP-A-2010-20371 describes a vehicle control system for guiding a vehicle in the event of disaster. The control system taught by JP-A-2010-20371 is configured to find an available space in a road shoulder, and guide the vehicle autonomously to the available space and stops the vehicle, upon reception of disaster information. 
     According to the teachings of JP-A-2014-154128, the emergency vehicle is allowed to travel smoothly if all of the other vehicles can be operated autonomously. However, if a vehicle that can be operated only manually also travels on the expected route of the emergency vehicle, the emergency vehicle has to travel while passing around the vehicle being operated manually. In addition, the vehicles operated autonomously may not be guided smoothly to the road shoulder and hence it may take longer time to clear the way for the emergency vehicle. 
     According to the teachings of JP-A-2011-79388, in the event that the emergency vehicle approaches, the vehicle may not move to an safety area smoothly due to the restriction on the vehicle speed. Further, the vehicle may not be accelerated sufficiently depending on the traffic conditions, and hence it may take longer time to clear the way for the emergency vehicle. 
     According to the teachings of JP-A-2008-84004, although the vehicle having the driving support system can be assisted to take a yielding action, other vehicles around the vehicle may not be controlled to clear the way for the emergency vehicle. Further, an action taken to travel in a cooperative manner with the other vehicles may be recognized erroneously as the yielding action. Therefore, the vehicle may not take an appropriate yielding action cooperatively with the other vehicles. 
     According to the teachings of JP-A-2005-228111, safety spaces are allotted for the specified vehicles travelling on the expected route of the emergency vehicle so that it is possible to clear the way promptly for the emergency vehicle. However, if some of the specified vehicles do not follow the instruction, the allotted safety spaces will not work properly, and the specified vehicles following the instruction may be confused. 
     The route search system taught by JP-A-2006-184213 may search an appropriate route for the emergency vehicle, but may not control the other vehicles on the planned route to clear the way for the emergency vehicle. The control system taught by JP-A-2010-20371 may find an available space in the road shoulder in the event of disaster, but may not control the other vehicles to clear the way for the emergency vehicle. 
     SUMMARY 
     Aspects of the present disclosure have been conceived noting the foregoing technical problems, and it is therefore an object of the present disclosure to provide a yielding action assistance system for assisting a vehicle driver to take an appropriate action in yielding to a passing emergency vehicle. 
     An embodiment of the present disclosure relates to a yielding action assistance system that assists a vehicle to yield to a passing emergency vehicle. In order to achieve the above-explained objective, according to the embodiment of the present disclosure, the yielding action assistance system is provided with: a detector that detects a proximity of the emergency vehicle to the vehicle; an information collector that collects information about a road on which the vehicle travels, and information about the emergency vehicle and other vehicle travelling on the same road with the vehicle; a target zone determiner that sets a target zone to pull over the vehicle to clear the way for the emergency vehicle based on the information about the other vehicle and the road, and that updates the target zone continuously based at least on the information about the other vehicle; and a notifier that informs a driver about the target zone. 
     In a non-limiting embodiment, the information collector may be configured to collect information about the emergency vehicle and the vehicle, and the target zone determiner may be configured to update the target zone until the emergency vehicle overtakes the vehicle. 
     In a non-limiting embodiment, the target zone determiner may be further configured to set the target zone in a shoulder of the road at a site at which a width of the target zone can be maintained wider than a width of the emergency vehicle, and a distance between the vehicle and the other vehicle to be stopped in an oncoming lane is maintained longer than a length of the emergency vehicle. 
     In a non-limiting embodiment, the yielding action assistance system may further comprise a first drive force controller that changes a drive force to increase a deceleration force when the driver pulls over the vehicle to the target zone indicated by the notifier. 
     In a non-limiting embodiment, the first drive force controller may be configured to calculate a distance between the vehicle and the target zone, and to change the drive force when the distance between the vehicle and the target zone is reduced to a threshold value. 
     In a non-limiting embodiment, the first drive force controller may be further configured to detect a speed of the vehicle, and to increase the threshold value with an increase in the speed of the vehicle. 
     In a non-limiting embodiment, the first drive force controller may be further configured to calculate a distance between the vehicle and the target zone, and to change the drive force to increase the deceleration force with a reduction in the distance between the vehicle and the target zone. 
     In a non-limiting embodiment, the target zone determiner may be further configured to set the target zone in a lane other than an innermost lane while avoiding interference with the other vehicle, in a case that the vehicle travels on a multi-lane road. 
     In a non-limiting embodiment, the yielding action assistance system may further comprise a second drive force controller that changes a drive force to increase a deceleration force after the vehicle arrives at the target zone. 
     Thus, according to the embodiment of the present disclosure, the target zone to pull over the vehicle is set based on the information about the emergency vehicle and the other vehicle. The target zone is updated continuously and the driver of the vehicle is informed about the updated target zone. According to the embodiment of the present disclosure, therefore, the driver is allowed to pull over the vehicle smoothly to the target zone so as to yield to the passing emergency vehicle, even if the driver is not aware of proximity of the emergency vehicle. In other words, the driver of the vehicle is allowed to clear the way smoothly for the passing emergency vehicle depending on a situation on the road. 
     In addition, according to the embodiment of the present disclosure, the deceleration force applied to the vehicle is increased to stop the vehicle or to reduce the speed of the vehicle when pulling over the vehicle to the target zone or when travels within the target zone. According to the embodiment of the present disclosure, therefore, the driver of the vehicle is allowed to yield to the emergency vehicle promptly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features, aspects, and advantages of exemplary embodiments of the present disclosure will become better understood with reference to the following description and accompanying drawings, which should not limit the disclosure in any way. 
         FIG. 1  is a schematic illustration showing an example of locations of vehicles and target zones for the vehicles to yield to an emergency vehicle on a single-lane road; 
         FIG. 2  is a block diagram showing a configuration of the controller; 
         FIG. 3  is a schematic illustration showing a distance between the target zone for the vehicle and a stopping point of the vehicle running in an oncoming lane; 
         FIG. 4  is a schematic illustration showing an example of locations of vehicles and target zones for the vehicles to yield to an emergency vehicle on a multi-lane road; 
         FIG. 5  is a flowchart showing a routine for setting the target zone to yield to the emergency vehicle; 
         FIG. 6  is a flowchart showing a routine for warning the driver and controlling a drive force to the emergency vehicle; 
         FIG. 7  is a graph indicating a relation between a threshold distance to the target zone and a vehicle speed; and 
         FIG. 8  is a time chart showing temporal changes in a speed ratio of a transmission, an engine speed etc. during execution of the routines shown in  FIGS. 5 and 6 . 
     
    
    
     DETAILED DESCRIPTI S N S F THE PREFERRED EMBODIMENT(S) 
     Embodiments of the present disclosure will now be explained with reference to the accompanying drawings. Referring now to  FIG. 1 , there is shown an example of a situation in which an emergency vehicle Ve such as an ambulance, a police car, a fire truck etc. approaches a vehicle Vm from behind. In such situation, the yielding action assistance system according to the present disclosure outputs information for assisting a driver of the vehicle Vm and the vehicle Vm to take an appropriate yielding action to clear the way for the emergency vehicle Vm. In the situation illustrated in  FIG. 1 , other vehicles Vo 1  and Vo 2  exist on a road R. In the following explanation, definition of the “other vehicle” includes a vehicle running on the road R in the same direction as the emergency vehicle Ve and the vehicle Vm, a vehicle running on an oncoming lane, and a vehicle stopping in any lane of the road R. 
     According to the present embodiment, the yielding action assistance system is installed at least partially in the vehicle Vm. The yielding action assistance system is configured to find a target zone Pe where the vehicle Vm stops or runs slowly to yield to the emergency vehicle Ve taking account of positional relationship among the emergency vehicle Ve and the other vehicles Vo, and guide the vehicle Vm to the target zone Pe. Specifically, the yielding action assistance system finds or selects the target zone Pe at a site where the vehicle Vm will not block the emergency vehicle Ve without interference with the other vehicles Vo, based on information about the emergency vehicle Ve, the other vehicles Vo, and the road R. 
     Turning to  FIG. 2 , there are shown configurations and function of a controller  1  of the yielding action assistance system. An information collector  2  of the controller  1  comprises: a first information collector  2   a  that collects information about the emergency vehicle Ve; a second information collector  2   b  that collects information about the other vehicles Vo; a third information collector  2   c  that collects road information; and a fourth information collector  2   d  that collects information about the vehicle Vm. Specifically, the first information collector  2   a  collects information about a speed, a destination, a current position, a width, a length, etc., of the emergency vehicle Ve. The second information collector  2   b  collects information about a speed, a direction, a current position, a destination, a width, a length, a position of an accelerator pedal (not shown), a position of a brake pedal (not shown) or a pedal force applied to the brake pedal, a steering angle, a driving preference of a driver etc., of the other vehicle Vo. The third information collector  2   c  collects information about the road R on which the vehicle Vm and the emergency vehicle Ve travel, and a planned route of the emergency vehicle Ve. More specifically, the information about the road R includes a straightness, a curvature, an existence of an intersection, a number of lanes, a width of the road R, a width of the shoulder, a color of the traffic light, an existence of a center divider etc., within a range in which the emergency vehicle Ve overtakes the vehicle Vm or within a range slightly larger than such range. The fourth information collector  2   d  collects information about a speed, a direction, a current position, a destination, a width, a length, a position of an accelerator pedal (not shown), a position of a brake pedal (not shown) or a pedal force applied to the brake pedal, a steering angle etc., of the vehicle Vm. 
     For example, the above-mentioned information may be obtained from an external site Dc such as a datacenter holding big data through a communication means, and through an inter-vehicle communication with the emergency vehicle Ve and the other vehicle Vo. The above-mentioned information may also be obtained from a storage means installed in the vehicle Vm. 
     The controller  1  further comprises a target zone determiner  3  configured to determine the target zone Pe for the vehicle Vm to yield to the emergency vehicle Ve, based at least on the information about the road R and the other vehicles Vo 1  and Vo 2  collected by the information collector  2 . Specifically, the target zone Pe is set based on: a condition of the road R; positions of the vehicle Vm, the emergency vehicle Ve, and the other vehicles Vo 1  and Vo 1 ; a travelling direction of the emergency vehicle Ve, and so on. Basically, the target zone Pe is set within the shoulder (or a side strip) of the road R, but various sites available to stop the vehicle Ve may be set as the target zone Pe. In the example shown in  FIG. 1 , the target zone Pe is set within the shoulder of the road R at a site possible to create a space for the emergency vehicle Ve to pass in the travel lane, outside of an intersection Is. The road R shown in  FIG. 1  is a single-lane road including a first lane L 1  and a second lane L 2  opposed to each other without a center divider. In the road R, the target zone Pe is set to a site at which an available width for the emergency vehicle Ve to overtake can be maintained wider than a width (We) of the emergency vehicle Ve. Specifically, such available width can be calculated by subtracting a total width of a width (Wm) of the vehicle Vm and a width (Wo 2 ) of the other vehicle Vo 2  running on the oncoming second lane L 2  from a total width (Wr) of the road R, as expressed by the following expression:
 
Available width=( Wr −( Wm+Wo 2)); and
 
the available width (Wr−(Wm+Wo 2 )) is wider than the width (We) of the emergency vehicle Ve, as expressed by the following inequality expression:
 
( Wr −( Wm+Wo 2))&gt; We.  
 
In a case that the road R is divided by the center divider, the available width is calculated by subtracting the width (Wm) of the vehicle Vm from a width (Wr/2) of the first lane L 1 , as expressed by the following expression:
 
Available width=( Wr/ 2 −Wm ).
 
In this case, the target zone Pe is also set to a site at which the available width can be maintained wider than the width (We) of the emergency vehicle Ve to satisfy the following inequality expression:
 
( Wr/ 2− Wm )&gt; We.  
 
     However, if the available width (Wr−(Wm+Wo 2 )) is narrower than the width (We) of the emergency vehicle Ve, and a distance between the target zone Pe for the vehicle Vm and a stopping point Pot of the other vehicle Vo 1  in the oncoming second lane L 2  in the direction of the road R is shorter than a length Le of the emergency vehicle Ve as illustrated in  FIG. 3 , it is difficult for the emergency vehicle Ve to pass between the vehicle Vm and the other vehicle Vo 1 . In order to avoid such disadvantage, the target zone determiner  3  is further configured to set the target zone Pe for the vehicle Vm to a site in the first lane L 1  away from the stopping point Po 2  in the oncoming second lane L 2  more than the length Le of the emergency vehicle Ve. 
     In the road R, behavior of the other vehicles differ from one another. For example, some of the vehicles may yield to the emergency vehicle Ve, but some of the vehicles may not yield to the emergency vehicle Ve. In order to set the target zone Pe to a site at which the vehicle Vm is allowed to yield to the emergency vehicle Ve without interference with the other vehicles, the target zone determiner  3  presumes the stopping points of the other vehicles Vo 1  and Vo 1  based on the information about the speeds and the steering angles of the other vehicles Vo 1  and Vo 1  collected by the second information collector  2   b . Such interference with the other vehicles may be avoided more certainly by setting the target zone Pe for the vehicle Vm based further on the road information collected by the third information collector  2   c.    
     In the situation illustrated in  FIG. 1 , the other vehicle Vo 1  running on the first lane L 1  has already entered into the intersection Is earlier than the vehicle Ve. In this situation, it is expected that the other vehicle Vo 1  passes through the intersection Is while increasing or maintaining a speed, and then pulls to a stopping pint Po 1  in the shoulder of the first lane L 1  to stop or to run slowly. Such movement of the other vehicle Vo 1  and the stopping point Po 1  are presumed or predicted based on the information collected by the second information collector  2   b . On the other hand, the other vehicle Vo 1  running on the oncoming second lane L 2  is expected to pass through the intersection Is, and then pulls to the stopping point Po 2  in the shoulder of the second lane L 2  to stop or to run slowly. Such movement of the other vehicle Vo 1  and the stopping point Po 2  are also presumed or predicted based on the information collected by the second information collector  2   b.    
     In the situation illustrated in  FIG. 1 , the vehicle Vm has not yet entered into the intersection Is. In this situation, therefore, the target zone Pe for the vehicle Ve may be set in front of the intersection Is. However, if the target zone Pe for the vehicle Vm is set in front of the intersection Is, the target zone Pe and the stopping point Po 2  at which the other vehicle Vo 1  is expected to stop would be situated next to each other in a width direction of the road R, and hence the available width between the target zone Pe and the stopping point Po 2  would be too narrow for the emergency vehicle Ve to pass therebetween. In other words, the distance between the target zone Pe and the stopping point Po 2  for the other vehicle Vo 1  in the direction of the road R would be shorter than the length Le of the emergency vehicle Ve. In order to avoid such disadvantage, the target zone Pe for the vehicle Vm is set further than the intersection Is and behind the expected stopping point Po 1  of the other vehicle Vo 1 . However, if the other vehicles Vo 1  and Vo 1  do not move onto the stopping points Po 1  and Po 2  against expectations, the vehicle Vm may not be allowed to pull over to the target zone Pe. The target zone determiner  3  updates the target zone Pe and the stopping points Po 1  and Po 2  continuously based on the information about the other vehicles Vo 1  and Vo 1 . In other words, the target zone Pe is updated continuously according to the current situation. 
     In a case that the road R is a multi-lane road as illustrated in  FIG. 4 , the emergency vehicle Ve is allowed to overtake other vehicles smoothly by clearing an inner lane L 3  adjacent to the center line CL. In the situation illustrated in  FIG. 4 , the target zone determiner  3  sets the target zone Pe within the first lane L 1  (i.e., an outer lane) between the other vehicles Vo 1  and Vo 3 . In other words, the target zone Pe is set within the lane other than the innermost lane L 3 . In this case, the vehicle Vm will not stop at the target zone Pe but runs slowly at the target zone Pe in formation with the other vehicles Vo 1  and Vo 3 . Such control may be executed only in a case that both of the vehicle Vm and the emergency vehicle Ve are in the inner lane L 3 . If the emergency vehicle Ve runs on the shoulder for some reason, the target zone Pe may be set between the other vehicles Vo 1  and Vo 3  other than the first lane L 1 . 
     In order to assist a driver  4  of the vehicle Vm to take an appropriate action in yielding to the emergency vehicle Ve, the controller  1  further comprises a notifier  5  that warns the driver  4  of the vehicle Vm to guide the driver  4  to pull over to the target zone Pe. The notifier  5  is configured to warn the driver  4  by an audio or visible message, or by controlling a steering force. According to the embodiment, the notifier  5  is configured to indicate a map identifying a route from a current position of the vehicle Vm to the target zone Pe on an indicator  6  such as a liquid-crystal monitor or a head-up display. Alternatively, the notifier  5  may also be configured to apply a steering force in such a manner as to guide the vehicle Vm to the target zone Pe while controlling direction indicator lamps. According to the embodiment, therefore, the driver  4  of the vehicle Vm is allowed to pull over to the target zone Pe smoothly in accordance with the guidance so as to yield to the emergency vehicle Ve. 
     In order to yield to the emergency vehicle Ve, the vehicle Vm is required to reduce the speed. To this end, the controller  1  further comprises a drive force controller  7  configured to control a relation between a position of the accelerator pedal and a drive force to be generated, and a relation between an operating amount of the brake pedal and a brake force to be generated, when yielding to the emergency vehicle Ve. For example, the drive force controller  7  may be configured to increase deceleration force when yielding to the emergency vehicle Ve. 
     The drive force and the deceleration force are changed in accordance with an output power of an engine, a speed ratio of a transmission, and a drive force or a regenerative force of a motor used in a hybrid vehicle (neither of which are shown). In order to control the drive force and the deceleration force, the drive force controller  7  transmits command signals to an engine controller (referred to as ENG-ECU in  FIG. 2 )  8 , a transmission controller (referred to as T/M-ECU in  FIG. 2 )  9 , and a hybrid controller (referred to as HV-ECU in  FIG. 2 )  10 . 
     When stopping the vehicle Vm to yield to the emergency vehicle Ve, the target zone Pe where the vehicle Vm is stopped is set by the target zone determiner  3 . In this situation, the deceleration force is increased by reducing the output power of the engine, by increasing the speed ratio of the transmission to increase an engine braking force, by increasing a regenerative braking force of the regenerative motor, or by increasing the brake force with respect to a pedal force applied to the brake pedal. Here, it is to be noted that an increasing amount of the deceleration force and a timing to increase the deceleration force are adjustable depending on a distance to the target zone Pe and a current speed of the vehicle Vm. For example, the deceleration force may be increased when the distance to the target zone Pe reaches a threshold value. The threshold value is also adjustable depending on a speed of the vehicle Ve. Specifically, the threshold value may be increased with an increase in the speed of the vehicle Ve. In addition, a reduction amount of the deceleration force may be reduced if the distance to the target zone Pe is long. In other words, the reduction amount of the deceleration force may be increased if the distance to the target zone Pe is short. 
     Otherwise, when changing a lane to yield to the emergency vehicle Ve without stopping the vehicle Ve, the deceleration force is increased after the vehicle Vm arrives at the target zone Pe so as to drive the vehicle Ve cooperatively with the other vehicles. 
     All of the information collector  2 , the target zone determiner  3 , the notifier  5 , and the drive force controller  7  of the controller  1  may be installed in the vehicle Vm. Instead, a predetermined component(s) of the controller  1  may be installed in the external site Dc according to a data processing capacity of the vehicle Vm and a data communication capacity of the communication means. For example, at least part of the information collector  2  and the target zone determiner  3  may be installed in the external site Dc, and the remaining components of the controller  1  may be installed in the vehicle Vm. 
     Here will be explained a routine for setting the target zone Pe with reference to  FIG. 5 , and the routine shown in  FIG. 5  is repeated at predetermined intervals. At step S 1 , a proximity of the emergency vehicle Ve to the vehicle Vm is determined based on the positional information of the emergency vehicle Ve collected by the first information collector  2   a , and the positional information of the vehicle Vm collected by the fourth information collector  2   d . Accordingly, the first information collector  2   a  and the fourth information collector  2   d  serve as a detector of the present embodiment. If the answer of step S 1  is NO, the routine returns without executing any specific control. By contrast, if the emergency vehicle Ve approaches the vehicle Vm so that the answer of step S 1  is YES, the routine progresses to step S 2  to obtain information about the emergency vehicle Ve, the other vehicles Vo 1  and Vo 1 , the road R, and the vehicle Vm. 
     Then, at step S 3 , it is determined whether the vehicle Vm is required to yield to the emergency vehicle Ve. For example, the answer of step S 3  will be YES if the vehicle Vm travels on the planned route of the emergency vehicle Ve. If the road R is a multi-lane road and both lanes are occupied by the other vehicles Vo 1  and Vo 1 , the answer of step S 3  will also be YES even if the vehicle Vm travels on the different lane from the lane on which the emergency vehicle Ve travels. Otherwise, if a planned route of the vehicle Vm and the planned route of the emergency vehicle V do not intersect with each other, the answer of step S 3  will be NO. For example, the answer of step S 3  will be NO in a case that the vehicle Vm takes a right or left turn at the intersection Is and the emergency vehicle Ve goes straight down the intersection Is, in a case that the emergency vehicle Ve takes a right or left turn at the intersection Is and the vehicle Vm goes straight down the intersection Is, and in a case that a destination of the emergency vehicle Ve is behind the vehicle Vm. 
     If the answer of step S 3  is NO, the routine returns without executing any specific control. By contrast, if the answer of step S 3  is YES, the routine progresses to step S 4  to set the target zone Pe by the above-explained procedures. Then, the routine progresses to step S 5  to set a flag F representing a completion of setting of the target zone Pe to “1”. Here, it is to be noted that the flag F is set to “0” in a normal situation in which there is no need to set the target zone Pe. 
     Then, it is determined at step S 6  whether the emergency vehicle Ve has overtaken the vehicle Vm based on the information about the emergency vehicle Ve collected by the first information collector  2   a . If the answer of step S 6  is NO, it is expected that the emergency vehicle Ve passes by the vehicle Vm and hence the routine returns to step S 2  to continue the yielding action of the vehicle Vm. In this case, if the speed and/or the steering angle of the other vehicle Vo 1  or Vo 1  have/has been changed, the estimated stopping point Po 1  of the other vehicle Vo 1  or the estimated stopping point Po 2  of the other vehicle Vo 1  is updated based on the updated information of the other vehicle Vo 1  or Vo 1 . Then, the target zone Pe for the vehicle Vm is updated based on the updated stopping point Po 1  of the other vehicle Vo 1  or the updated stopping point Po 2  of the other vehicle Vo 1 . Such update of the target zone Pe for the vehicle Vm is repeated until the emergency vehicle Ve overtakes the vehicle Vm. 
     By contrast, if the emergency vehicle Ve has overtaken the vehicle Vm so that the answer of step S 6  is YES, the routine progresses to step S 7  to reset the flag F representing a completion of setting of the target zone Pe to “0”, and thereafter returns. 
     Turning to  FIG. 6 , there is shown a routine for notifying the driver  4  of the proximity of the emergency vehicle Ve and changing the drive force to yield to the emergency vehicle, that is executed in conjunction with the routine shown in  FIG. 5 . In the routine shown in  FIG. 6 , it is determined at step S 10  whether the flag F is set to “1”. If the flag F is set to “1” so that the answer of step S 10  is YES, the routine progresses to step S 11  to inform the driver  4  about the target zone Pe. By contrast, if the answer of step S 10  is NO, the routine returns. 
     Then, it is determined at step S 12  whether the driver  4  is required to stop the vehicle Vm at the target zone Pe. As described, if the road R is a single-lane road, the vehicle Vm is required to pull over to the target zone Pe thereby clearing the way for the emergency vehicle Ve. In this case, the answer of step S 12  will be YES. By contrast, the road R is a multi-lane road, it may be possible to yield to the emergency vehicle Ve by pulling into another lane while running slowly. In this case, the answer of step S 12  will be NO. 
     If the answer of step S 12  will be YES, the routine progresses to step S 13  to determine whether a distance D to the target zone Pe is equal to or shorter than a threshold distance D 0 . Such determination at step S 13  is made to determine a timing to change the drive force to increase the deceleration force. In order to avoid an abrupt deceleration of the vehicle Vm, as shown in  FIG. 7 , the threshold distance D 0  may be increased with an increase in the speed V of the Vehicle Vm. Consequently, a deceleration rate (i.e., a reduction rate of the vehicle speed) of the vehicle Vm when pulling over to the target zone Pe may be substantially equalized regardless of the situation. 
     If the distance D to the target zone Pe is still shorter than the threshold distance D 0  so that the answer of step S 13  is NO, the routine returns to step S 12  to repeat the above-explained determination at step S 12 . By contrast, if the distance D to the target zone Pe is equal to or shorter than the threshold distance D 0  so that the answer of step S 12  is YES, the routine progresses to step S 14  to change the drive force of the vehicle Vm to increase the deceleration force. Then, it is determined at step S 15  whether the vehicle Vm arrives and stops at the target zone Pe based on the positional information and the current speed V of the vehicle Vm. 
     If the answer of step S 15  is NO, the routine returns to step S 14  to control the drive force of the vehicle Vm continuously. By contrast, if the answer of step S 15  is YES, the routine progresses to step S 16  to determine whether the flag F is set to “0”. As described, the flag F is reset to “0” when the emergency vehicle Ve overtakes the vehicle Vm stopping at the target zone Pe. That is, at step S 16 , it is determined whether the emergency vehicle Ve has overtaken the vehicle Vm. If the answer of step S 16  is NO, the routine returns to step S 14  to control the drive force of the vehicle Vm continuously, or to step S 15  to instruct the driver  4  of the vehicle Vm to stay in the target zone Pe continuously. 
     By contrast, if the answer of step S 16  is YES, the routine progresses to step S 17  to control the drive force of the vehicle Vm in a normal manner, and further progresses to step S 18  to terminate the notification. Thereafter, the routine returns. 
     Otherwise, if it is possible to yield to the emergency vehicle Ve while driving the vehicle Vm at a low speed so that the answer of step S 12  is NO, the routine progresses to step S 19  to determine whether the vehicle Ve has arrived at the target zone Pe based on the positional information of the vehicle Vm. At step S 19 , specifically, it is determined whether the lane change of the vehicle Vm has been completed. If the answer of step S 19  is NO, the routine returns to step S 12  to repeat the above-explained determination at step S 12 . By contrast, if the answer of step S 19  is YES, the routine progresses to step S 20  to change the drive force of the vehicle Vm to increase the deceleration force. At the foregoing step S 14 , the drive force of the vehicle Vm is changed to stop the vehicle Vm. On the other hand, at step S 20 , the drive force of the vehicle Vm is changed in such a manner as to propel the vehicle Vm at a low speed. To this end, therefore, an increasing amount of the deceleration force at step S 20  may be smaller than an increasing amount of the deceleration force at step S 14 . 
     Then, it is determined at step S 21  whether the flag F is reset to “0”. That is, it is determined whether the emergency vehicle Ve has overtaken the vehicle Vm. If the answer of step S 21  is NO, the routine returns to step S 20  to control the drive force of the vehicle Vm continuously. By contrast, if the answer of step S 20  is YES, the routine progresses to step S 17  to terminate the yielding action assisting control and further progresses to step S 18  to terminate the notification. Thereafter, the routine returns. 
     Turning to  FIG. 8 , there is shown a time chart during execution of the yielding action assisting control to stop the vehicle Vm at the target zone Pe. When the emergency vehicle Ve is detected, the target zone Pe is set and the driver  4  of the vehicle Ve is informed about the location of the target zone Pe. Consequently, the driver  4  returns the accelerator pedal so that an opening degree of the accelerator is “0”. In this situation, if the vehicle Vm propels at a speed close to a speed limit of the road R, a speed ratio (or a gear stage) of the transmission is set to the highest stage Y 6 . That is, the speed ratio of the transmission is reduced to a substantially smallest ratio and hence an engine braking force applied to the vehicle Vm is weak. In this situation, therefore, the vehicle speed V and an engine speed are maintained constant. 
     When the distance D to the target zone Pe reaches the threshold distance D 0  at point t 1 , the routine progressed from step S 13  to step S 14  and a downshift command is transmitted at point t 2  to increase the deceleration force. Consequently, the gear stage of the transmission is shifted from the highest stage Y 6  to a mid-low stage Y 3  to increase the speed ratio so that the engine braking force is increased. As a result, the engine speed is raised, a reduction rate of the vehicle speed V is increased, and a reduction rate of the distance D to the target zone Pe is reduced. In this situation, the engine speed is increased in accordance with the speed ratio after the downshifting, and then drops with a reduction in the vehicle speed V. Thus, the vehicle speed V is reduced gradually by increasing the deceleration force so that the vehicle Ve is allowed to pull over to the target zone Pe slowly. According to the embodiment, therefore, a behavior of the vehicle Ve will not be changed abruptly when yielding to the emergency vehicle Ve. 
     Although the above exemplary embodiments of the present disclosure have been described, it will be understood by those skilled in the art that the present disclosure should not be limited to the described exemplary embodiments, and various changes and modifications can be made within the scope of the present disclosure. 
     For example, the yielding action assistance system may be modified to increase the deceleration force when the other vehicle Vo 1  or Vo 2  comes close to the vehicle Vm. In addition, the yielding action assistance system may be modified to increase the deceleration force at a timing at which the emergency vehicle Ve passes by the vehicle Vm. Optionally, the drive force of the vehicle Vm may be reduced to “0” while the vehicle Ve stops at the target zone Pe by stopping the engine, by bringing the transmission into a neutral state, or by activating a parking brake.