Apparatus and method for controlling a target distance and a warning distance between traveling vehicles and a recording medium for storing the control method

• US 6,418,370 B1
• Filed: 08/04/1999
• Issued: 07/09/2002
• Est. Priority Date: 08/04/1998
• Status: Expired due to Term

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Isogai, Akira, Nishimura, Takao, Teramura, Eiji
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): TO, TUAN C
• Application Number:
  US09/366,790
• Time in Patent Office: 1,070 Days
• Field of Search: 701/96, 701/97, 342/455, 342/29, 340/436, 340/903, 340/437, 340/438, 180/169, 180/167, 180/179, 434/236, 434/238
• US Class Current: 701/96
• CPC Class Codes: B60K 31/0008 including means for detecting potential obstacles in vehicle path
• CPC Class Codes: B60Q 9/008 for anti-collision purposes
• CPC Class Codes: B60T 2201/08 Lane monitoring; Lane Keeping Systems
• CPC Class Codes: B60T 2201/082 using alarm actuation
• CPC Class Codes: B60W 2520/14 Yaw
• CPC Class Codes: B60W 2540/18 Steering angle
• CPC Class Codes: B60W 2754/30 Longitudinal distance
• CPC Class Codes: G08G 1/166 for active traffic, e.g. moving vehicles, pedestrians, bikes
• CPC Class Codes: G08G 1/167 Driving aids for lane monitoring, lane changing, e.g. blind spot detection

Abstract

A distance control is performed to maintain a target distance between two traveling vehicles by controlling an acceleration/deceleration actuator based on a physical quantity representing an actual distance between the two traveling vehicles. A temporary distance control is performed to suppress a deceleration degree of a succeeding vehicle to a smaller value compared with a deceleration degree attainable during an ordinary distance control, when the two traveling vehicles are departing from each other under a condition where the actual distance between the two traveling vehicles is already shorter or will soon become shorter than a standard target distance.

Claims

1. A distance control apparatus for controlling a distance between two traveling vehicles, said control apparatus comprising:

distance detecting means for detecting a physical quantity directly or indirectly representing an actual distance between said two traveling vehicles;

acceleration/deceleration means for accelerating and decelerating a succeeding vehicle; and

distance control means for performing a distance control so as to maintain a target distance between said two traveling vehicles by actuating said acceleration/deceleration means based on said physical quantity detected by said distance detecting means,

wherein said distance control means performs a temporary distance control for suppressing a deceleration degree of said succeeding vehicle to a smaller value compared with a deceleration degree attainable during an ordinary distance control when said two traveling vehicles are departing from each other under a condition where the actual distance between said two traveling vehicles is already shorter or will soon become shorter than a standard target distance.

2. The distance control apparatus in accordance with claim 1, wherein

distance control means obtains a control value based on a first physical quantity and a second physical quantity, said first physical quantity representing a distance deviation between an actual distance and a target distance between two traveling vehicles, and said second physical quantity representing a relative speed between said two traveling vehicles,

said acceleration/deceleration means is actuated based on said control value to adjust the actual distance between said two traveling vehicles, and

said distance control means performs said temporary distance control for suppressing the deceleration degree of said succeeding vehicle when said two traveling vehicles are departing from each other under a condition where said actual distance between two traveling vehicles is shorter than the standard target distance.

3. The distance control apparatus in accordance with claim 2, wherein the two traveling vehicles include the succeeding vehicle and a preceding vehicle with respect to which distance is being controlled by said apparatus, the temporary distance control being executed in control analysis cycles,

said apparatus further comprising means for judging whether a preceding vehicle based on which control analysis was performed in a previous control analysis cycle is the same as the preceding vehicle based on which control analysis is performed in a current control analysis cycle, and

wherein said temporary distance control is performed only when said preceding vehicle based on which control analysis was performed in said previous control analysis cycle is judged to be the same as the preceding vehicle based on which control analysis is performed in the current control analysis cycle.

4. The distance control apparatus in accordance with claim 2, wherein said distance control means temporarily changes said target distance to a provisional target distance to realize said temporary distance control for suppressing the deceleration degree of said succeeding vehicle, and said provisional target distance has an initial value substantially equal to the actual distance between said two traveling vehicles and a transitional value gradually restoring to said standard target distance.

5. The distance control apparatus in accordance with claim 1, wherein

said distance control means obtains a control value based on a first physical quantity and a second physical quantity, said first physical quantity representing a distance deviation between an actual distance and a target distance between two traveling vehicles, and said second physical quantity representing a relative speed between said two traveling vehicles,

said acceleration/deceleration means is actuated based on said control value to adjust the actual distance between said two traveling vehicles,

said distance control means performs said temporary distance control for suppressing the deceleration degree of said succeeding vehicle when said actual distance between said two traveling vehicles is shorter than a predetermined target distance,

said distance control means changes said target distance to a provisional target distance to realize said temporary distance control for suppressing the deceleration degree of said succeeding vehicle, and

said provisional target distance has an initial value determined in accordance with the relative speed between said two traveling vehicles and a transitional value gradually restoring to said standard target distance.

6. The distance control apparatus in accordance with claim 5, wherein said relative speed is a positive value when said two traveling vehicles are departing from each other and is a negative value when approaching to each other, and

said initial value of said provisional target distance is expressed by a decreasing function of said relative speed in a region between a predetermined negative value and a predetermined positive value of said relative speed.

7. The distance control apparatus in accordance with claim 5, wherein said initial value is equal or closer to said standard target distance when said relative speed is smaller than said predetermined negative value.

8. The distance control apparatus in accordance with claim 5, wherein said initial value is equal or closer to said actual distance between said two traveling vehicles when said relative speed is larger than said predetermined positive value.

9. The distance control apparatus in accordance with claim 5, wherein said relative speed is a positive value when said two traveling vehicles are departing from each other and is a negative value when approaching to each other, and

said initial value of said provisional target distance is expressed by a decreasing function of said relative speed in a region between a first positive value and a second positive value of said relative speed, where said second positive value is larger than said first positive value.

10. The distance control apparatus in accordance with claim 5, wherein said initial value is equal or closer to said standard target distance when said relative speed is smaller than said first positive value.

11. The distance control apparatus in accordance with claim 5, wherein said initial value is equal or closer to said actual distance between said two traveling vehicles when said relative speed is larger than said second positive value.

12. The distance control apparatus in accordance with claim 1, wherein the physical quantity representing said distance is expressed in terms of time interval which is obtained by dividing the distance between two traveling vehicles by a traveling speed of said succeeding vehicle.

13. The distance control apparatus in accordance with claim 1, wherein said distance control means performs said temporary distance control by setting a target acceleration of said succeeding vehicle,

wherein said distance control means temporarily suppresses the deceleration degree of said succeeding vehicle to the smaller value by changing a lower limit of said target acceleration to a provisional level, and

said provisional level has an initial value higher than an ordinary level and a transitional value gradually restoring to said ordinary level.

14. The distance control apparatus in accordance with claim 1, wherein

said distance control means obtaining a control value based on a first physical quantity and a second physical quantity, said first physical quantity representing a distance deviation between an actual distance and a target distance between said two traveling vehicles, and said second physical quantity representing a relative speed between said two traveling vehicles,

said acceleration/deceleration means is actuated based on said control value to adjust the actual distance between said two traveling vehicles,

said distance control means performs said temporary distance control for suppressing the deceleration degree of said succeeding vehicle when the actual distance between said two traveling vehicles is already shorter or will soon become shorter than the standard target distance due to an intentional driver'"'"'s operation of said succeeding vehicle performed to reduce the actual distance between said two traveling vehicles.

15. The distance control apparatus in accordance with claim 14, wherein said intentional driver'"'"'s operation of said succeeding vehicle is a lane change operation of said succeeding vehicle performed to follow up a new objective traveling on another traffic lane which is faster than said succeeding vehicle.

16. The distance control apparatus in accordance with claim 14, wherein said acceleration/deceleration means is manually operable by the driver of said succeeding vehicle, and

said intentional driver'"'"'s operation of said succeeding vehicle is an override operation performed to manually accelerate the succeeding vehicle so as to approach the preceding vehicle.

17. The distance control apparatus in accordance with claim 14, wherein said international driver'"'"'s operation of said succeeding vehicle is startup of said distance control.

18. The distance control apparatus in accordance with claim 14, wherein said relative speed is a positive value when said two traveling vehicles are departing from each other and is a negative value when approaching to each other, and

said distance control means performs said temporary distance control for suppressing the deceleration degree of said succeeding vehicle when a relative speed is larger than a predetermined value.

19. The distance control apparatus in accordance with claim 14, wherein said distance control means temporarily changes said target distance to a provisional target distance to realize said temporary distance control for suppressing the deceleration degree of said succeeding vehicle, and

said provisional target distance has an initial value substantially equal to the actual distance between said two traveling vehicles and a transitional value gradually restoring to said standard target distance.

20. The distance control apparatus in accordance with claim 14, wherein said distance control means temporarily changes said target distance to a provisional target distance to realize said temporary distance control for suppressing the deceleration degree of said succeeding vehicle, and

said provisional target distance has an initial value determined in accordance with the relative speed between said two traveling vehicles and a transitional value gradually restoring to said standard target distance.

21. The distance control apparatus in accordance with claim 20, wherein said initial value of said provisional target distance is expressed by a decreasing function of said relative speed in a region from a negative lower value to an upper value equal to or closer to 0.

22. The distance control apparatus in accordance with claim 20, wherein said initial value is equal or closer to said standard target distance when said relative speed is smaller than said negative lower value.

23. The distance control apparatus in accordance with claim 20, wherein said initial value is equal or closer to said actual distance between said two traveling vehicles when said relative speed is larger than said upper value.

24. The distance control apparatus in accordance with claim 21, wherein said upper value is a positive value closer to 0 when said intentional driver'"'"'s operation of said succeeding vehicle is a lane change operation of said succeeding vehicle performed to follow up a new objective traveling on another traffic lane which is faster than said succeeding vehicle.

25. The distance control apparatus in accordance with claim 21, wherein said upper value is a negative value closer to 0 when said intentional driver'"'"'s operation of said succeeding vehicle is an override operation performed to manually accelerate the succeeding vehicle so as to approach the preceding vehicle.

26. The distance control apparatus in accordance with claim 21, wherein said upper value is a negative value closer to 0 when said intentional driver'"'"'s operation of said succeeding vehicle is a control startup operation performed to start said distance control.

27. The distance control apparatus in accordance with claim 14, wherein said distance control means performs said temporary distance control by setting a target acceleration of said succeeding vehicle,

wherein said distance control means temporarily suppresses the deceleration degree of said succeeding vehicle to the smaller value by changing a lower limit of said target acceleration to a provisional level, and

said provisional level has an initial value higher than an ordinary level and a transitional value gradually restoring to said ordinary level.

28. The distance control apparatus in accordance with claim 14, further comprising a warning control means for performing a warning operation when said actual distance between said two traveling vehicles becomes shorter than a predetermined warning distance,

wherein said warning control means performs a temporary warning control for setting a provisional warning distance shorter than an ordinary warning distance when the actual distance between said two traveling vehicles is already shorter or will soon become shorter than said ordinary warning distance due to the intentional driver'"'"'s operation of said succeeding vehicle performed to reduce the actual distance between said two traveling vehicles.

29. The distance control apparatus in accordance with claim 28, wherein said provisional warning distance has an initial value substantially equal or closer to the actual distance between said two traveling vehicles and a transitional value gradually restoring to said ordinary warning distance.

30. The distance control apparatus in accordance with claim 28, wherein said acceleration/deceleration means comprises a plurality of deceleration devices being independently operable and different from each other in degree of attainable deceleration,

wherein said distance control means selects at least one of said plurality of deceleration devices corresponding to a deceleration degree determined to be necessary to decelerate said succeeding vehicle, and

wherein a warning prohibiting means is provided for preventing said warning control means from performing said warning operation if the determined deceleration degree is less than a predetermined maximum deceleration degree even if the actual distance between said two traveling vehicles is shorter than said ordinary warning distance.

31. The distance control apparatus in accordance with claim 30, wherein said warning prohibiting means judges that the deceleration level is higher than said predetermined maximum level when a deceleration device capable of generating a largest deceleration is included in said at least one of said deceleration devices selected by said distance control means.

32. The distance control apparatus in accordance with claim 30, wherein said warning prohibiting means judges that the deceleration level is higher than said predetermined maximum level when a predetermined combination of deceleration devices capable of generating a largest deceleration is selected by said distance control means.

33. The distance control apparatus in accordance with claim 30, wherein said warning prohibiting means judges that the deceleration level is higher than said predetermined maximum level when said control value obtained by said distance control means is equivalent to an available maximum deceleration.

34. The distance control apparatus in accordance with claim 28, wherein said intentional driver'"'"'s operation of said succeeding vehicle is a lane change operation of said succeeding vehicle performed to follow up a new objective traveling on another traffic lane which is faster than said succeeding vehicle.

35. The distance control apparatus in accordance with claim 34, wherein said warning control means cancels said temporary warning control for setting the provisional warning distance when said succeeding vehicle is approaching said new objective.

36. The distance control apparatus in accordance with claim 28, wherein said acceleration/deceleration means is manually operable by the driver of said succeeding vehicle, and

said intentional driver'"'"'s operation of said succeeding vehicle is an override operation performed to manually accelerate the succeeding vehicle so as to approach the preceding vehicle.

37. The distance control apparatus in accordance with claim 28, wherein said intentional driver'"'"'s operation of said succeeding vehicle is startup of said distance control.

38. A warning apparatus comprising:

a warning device for generating a warning or an alarm when an actual distance between two traveling vehicles becomes shorter than a predetermined warning distance; and

warning control means for activating or deactivating said warning device,

wherein said warning control means performs a temporary warning control for setting a provisional warning distance shorter than an ordinary warning distance when the actual distance between said two traveling vehicles is already shorter or will soon become shorter than said ordinary warning distance due to an intentional driver'"'"'s operation of a succeeding vehicle performed to follow up a new objective traveling on another traffic lane.

39. The warning apparatus in accordance with claim 38, wherein said provisional warning distance has an initial value substantially equal to the actual distance between said two traveling vehicles and a transitional value gradually restoring to said ordinary warning distance.

40. The warning apparatus in accordance with any claim 38, wherein said new objective traveling on said another traffic lane is faster than said succeeding vehicle.

41. The warning apparatus in accordance with claim 40, wherein said temporary warning control is canceled by said warning control means when said succeeding vehicle approaches said new objective during said temporary warning control.

42. A distance control method for controlling a distance between two traveling vehicles, said control method comprising the steps of:

detecting a physical quantity directly or indirectly representing an actual distance between said two traveling vehicles; and

performing a distance control so as to maintain a target distance between said two traveling vehicles based on said physical quantity,

wherein said distance control method further comprises the step of performing a temporary distance control for suppressing a deceleration degree of a succeeding vehicle to a smaller value compared with a deceleration degree attainable during an ordinary distance control when said two traveling vehicles are departing from each other under a condition where the actual distance between said two traveling vehicles is already shorter or will soon become shorter than a standard target distance.

43. The distance control method in accordance with claim 42, wherein

a control value is obtained based on a first physical quantity and a second physical quantity, said first physical quantity representing a distance deviation between an actual distance and a target distance between two traveling vehicles, and said second physical quantity representing a relative speed between said two traveling vehicles,

said succeeding vehicle is accelerated or decelerated based on said control value to adjust the actual distance between said two traveling vehicles, and

said temporary distance control is performed to suppress the deceleration degree of said succeeding vehicle when said two traveling vehicles are departing from each other under a condition where said actual distance between two traveling vehicles is shorter than a standard target distance.

44. The distance control method in accordance with claim 43, wherein the two traveling vehicles include the succeeding vehicle and a preceding vehicle with respect to which distance is being controlled, and wherein the temporary distance control is executed in control analysis cycles,

said method further comprising judging whether a preceding vehicle based on which control analysis was performed in a previous control analysis cycle is the same as the preceding vehicle based on which control analysis is performed in a current control analysis cycle, and

wherein said temporary distance control is performed only when said preceding vehicle based on which control analysis was performed in the previous control analysis cycle is judged to be the same as the preceding vehicle based on which control analysis is performed in the current control analysis cycle.

45. The distance control method in accordance with claim 43, wherein said target distance is temporarily changed to a provisional target distance to realize said temporary distance control for suppressing the deceleration degree of said succeeding vehicle, and said provisional target distance has an initial value substantially equal to the actual distance between said two traveling vehicles and a transitional value gradually restoring to said standard target distance.

46. The distance control method in accordance with claim 42, wherein

a control value is obtained based on a first physical quantity and a second physical quantity, said first physical quantity representing a distance deviation between an actual distance and a target distance between two traveling vehicles, and said second physical quantity representing a relative speed between said two traveling vehicles,

said succeeding vehicle is accelerated or decelerated based on said control value to adjust the actual distance between said two traveling vehicles,

said temporary distance control is performed to suppress the deceleration degree of said succeeding vehicle when said actual distance between said two traveling vehicles is shorter than the standard target distance,

said target distance is changed to a provisional target distance to realize said temporary distance control for suppressing the deceleration degree of said succeeding vehicle, and

said provisional target distance has an initial value determined in accordance with the relative speed between said two traveling vehicles and a transitional value gradually restoring to said standard target distance.

47. The distance control method in accordance with claim 46, wherein said relative speed is a positive value when said two traveling vehicles are departing from each other and is a negative value when approaching to each other, and

said initial value of said provisional target distance is expressed by a decreasing function of said relative speed in a region between a predetermined negative value and a predetermined positive value of said relative speed.

48. The distance control method in accordance with claim 46, wherein said initial value is equal or closer to said standard target distance when said relative speed is smaller than said predetermined negative value.

49. The distance control method in accordance with claim 46, wherein said initial value is equal or closer to said actual distance between said two traveling vehicles when said relative speed is larger than said predetermined positive value.

50. The distance control method in accordance with claim 46, wherein said relative speed is a positive value when said two traveling vehicles are departing from each other and is a negative value when approaching to each other, and

said initial value of said provisional target distance is expressed by a decreasing function of said relative speed in a region between a first positive value and a second positive value of said relative speed, where said second positive value is larger than said first positive value.

51. The distance control method in accordance with claim 46, wherein said initial value is equal or closer to said standard target distance when said relative speed is smaller than said first positive value.

52. The distance control method in accordance with claim 46, wherein said initial value is equal or closer to said actual distance between said two traveling vehicles when said relative speed is larger than said second positive value.

53. The distance control method in accordance with claim 42, wherein

a control value is obtained based on a first physical quantity and a second physical quantity, said first physical quantity representing a distance deviation between an actual distance and a target distance between said two traveling vehicles, and said second physical quantity representing a relative speed between said two traveling vehicles,

said succeeding vehicle is accelerated and/or decelerated based on said control value to adjust the actual distance between said two traveling vehicles, and

said temporary distance control is performed to suppress the deceleration degree of said succeeding vehicle when the actual distance between said two traveling vehicles is already shorter or will soon become shorter than the standard target distance due to an intentional driver'"'"'s operation of said succeeding vehicle performed to reduce the actual distance between said two traveling vehicles.

54. The distance control method in accordance with claim 53, wherein said intentional driver'"'"'s operation of said succeeding vehicle is a lane change operation of said succeeding vehicle performed to follow up a new objective traveling on another traffic lane which is faster than said succeeding vehicle.

55. The distance control method in accordance with claim 53, wherein said intentional driver'"'"'s operation of said succeeding vehicle is an override operation performed to manually accelerate the succeeding vehicle so as to approach the preceding vehicle.

56. The distance control method in accordance with claim 53, wherein said intentional driver'"'"'s operation of said succeeding vehicle is startup of said distance control.

57. The distance control method in accordance with claim 53, wherein said relative speed is a positive value when said two traveling vehicles are departing from each other and is a negative value when approaching to each other, and

said temporary distance control for suppressing the deceleration degree of said succeeding vehicle is performed when a relative speed is larger than a predetermined value.

58. The distance control method in accordance with claim 53, wherein said target distance is temporarily changed to a provisional target distance to realize said temporary distance control for suppressing the deceleration degree of said succeeding vehicle, and

said provisional target distance has an initial value substantially equal to the actual distance between said two traveling vehicles and a transitional value gradually restoring to said standard target distance.

59. The distance control method in accordance with claim 53, wherein said target distance is temporarily changed to a provisional target distance to realize said temporary distance control for suppressing the deceleration degree of said succeeding vehicle, and

said provisional target distance has an initial value determined in accordance with the relative speed between said two traveling vehicles and a transitional value gradually restoring to said standard target distance.

60. The distance control method in accordance with claim 59, wherein said initial value of said provisional target distance is expressed by a decreasing function of said relative speed in a region from a negative lower value to an upper value equal to or closer to 0.

61. The distance control method in accordance with claim 59, wherein said initial value is equal or closer to said standard target distance when said relative speed is smaller than said negative lower value.

62. The distance control method in accordance with claim 59, wherein said initial value is equal or closer to said actual distance between said two traveling vehicles when said relative speed is larger than said upper value.

63. The distance control method in accordance with claim 60, wherein said upper value is a positive value closer to 0 when said intentional driver'"'"'s operation of said succeeding vehicle is a lane change operation of said succeeding vehicle performed to follow up a new objective traveling on another traffic lane which is faster than said succeeding vehicle.

64. The distance control method in accordance with claim 60, wherein said upper value is a negative value closer to 0 when said intentional driver'"'"'s operation of said succeeding vehicle is an override operation performed to manually accelerate the succeeding vehicle so as to approach the preceding vehicle.

65. The distance control method in accordance with claim 60, wherein said upper value is a negative value closer to 0 when said intentional driver'"'"'s operation of said succeeding vehicle is a control startup operation performed to start said distance control.

66. The distance control method in accordance with claim 53, wherein said temporary distance control is performed by setting a target acceleration of said succeeding vehicle,

wherein the deceleration degree of said succeeding vehicle is temporarily suppressed to the smaller value by changing a lower limit of said target acceleration to a provisional level, and

said provisional level has an initial value higher than an ordinary level and a transitional value gradually restoring to said ordinary level.

67. The distance control method in accordance with claim 53, wherein a warning operation is performed when said actual distance between said two traveling vehicles becomes shorter than a predetermined warning distance,

wherein a temporary warning control is performed for setting a provisional warning distance shorter than an ordinary warning distance when the actual distance between said two traveling vehicles is already shorter or will soon become shorter than said ordinary warning distance due to the intentional driver'"'"'s operation of said succeeding vehicle performed to reduce the actual distance between said two traveling vehicles.

68. The distance control method in accordance with claim 67, wherein said provisional warning distance has an initial value substantially equal to the actual distance between said two traveling vehicles and a transitional value gradually restoring to said ordinary warning distance.

69. The distance control method in accordance with claim 67, wherein at least one of a plurality of deceleration devices is selected to decelerate said succeeding vehicle, said plurality of deceleration devices being independently operable and different from each other in degree of attainable deceleration, and

said warning operating is prohibited when a deceleration level attainable by said selected one or plurality of deceleration devices is lower than a predetermined maximum level even if the actual distance between said two traveling vehicles is shorter than said ordinary warning distance.

70. The distance control method in accordance with claim 69, wherein the deceleration level of said succeeding vehicle is judged to be higher than said predetermined maximum level when a deceleration device capable of generating a largest deceleration is selected to decelerate said succeeding vehicle.

71. The distance control method in accordance with claim 69, wherein the deceleration level of said succeeding vehicle is judged to be higher than said predetermined maximum level when a predetermined combination of deceleration devices capable of generating a largest deceleration is selected to decelerate said succeeding vehicle.

72. The distance control method in accordance with claim 69, wherein the deceleration level of said succeeding vehicle is judged to be higher than said predetermined maximum level when said control value is equivalent to an available maximum deceleration.

73. The distance control method in accordance with claim 67, wherein said intentional driver'"'"'s operation of said succeeding vehicle is a lane change operation of said succeeding vehicle performed to follow up a new objective traveling on another traffic lane which is faster than said succeeding vehicle.

74. The distance control method in accordance with claim 73, wherein said temporary warning control for setting the provisional warning distance is canceled when said succeeding vehicle is approaching said new objective.

75. The distance control method in accordance with claim 67, wherein said intentional driver'"'"'s operation of said succeeding vehicle is an override operation performed to manually accelerate the succeeding vehicle so as to approach the preceding vehicle.

76. The distance control method in accordance with claim 67, wherein said intentional driver'"'"'s operation of said succeeding vehicle is startup of said distance control.

77. A warning method for controlling a warning device, comprising the steps of:

judging whether an actual distance between two traveling vehicles becomes shorter than a predetermined warning distance;

activating or deactivating said warning device to generate a warning or an alarm based on judgement result; and

performing a temporary warning control for setting a provisional warning distance shorter than an ordinary warning distance when the actual distance between said two traveling vehicles is already shorter or will soon become shorter than said ordinary warning distance due to an intentional driver'"'"'s operation of a succeeding vehicle performed to follow up a new objective traveling on another traffic lane.

78. The warning method in accordance with claim 77, wherein said provisional warning distance has an initial value substantially equal to the actual distance between said two traveling vehicles and a transitional value gradually restoring to said ordinary warning distance.

79. The warning method in accordance with any claim 77, wherein said new objective traveling on said another traffic lane is faster than said succeeding vehicle.

80. The warning method in accordance with claim 79, wherein said temporary warning control for setting the provisional warning distance is canceled when said succeeding vehicle approaches said new objective during said temporary warning control.

81. A recording medium storing a control program for controlling a distance between two traveling vehicles, said recording medium being installable in a computer system, and said control program comprising the steps of:

detecting a physical quantity directly or indirectly representing an actual distance between said two traveling vehicles; and

performing a distance control so as to maintain a target distance between said two traveling vehicles based on said physical quantity,

wherein said control program further comprises the step of performing a temporary distance control for suppressing a deceleration degree of a succeeding vehicle to a smaller value compared with a deceleration degree attainable during an ordinary distance control when said two traveling vehicles are departing from each other under a condition where the actual distance between said two traveling vehicles is already shorter or will soon become shorter than a standard target distance.

82. The recording medium in accordance with claim 81, wherein

a control value is obtained based on a first physical quantity and a second physical quantity, said first physical quantity representing a distance deviation between an actual distance and a target distance between two traveling vehicles, and said second physical quantity representing a relative speed between said two traveling vehicles,

said succeeding vehicle is accelerated and/or decelerated based on said control value to adjust the actual distance between said two traveling vehicles, and

said temporary distance control is performed to suppress the deceleration degree of said succeeding vehicle when said two traveling vehicles are departing from each other under a condition where said actual distance between two traveling vehicles is shorter than the standard target distance.

83. The recording medium in accordance with claim 81, wherein

a control value is obtained based on a first physical quantity and a second physical quantity, said first physical quantity representing a distance deviation between an actual distance and a target distance between two traveling vehicles, and said second physical quantity representing a relative speed between said two traveling vehicles,

said succeeding vehicle is accelerated and/or decelerated based on said control value to adjust the actual distance between said two traveling vehicles,

said temporary distance control is performed to suppress the deceleration degree of said succeeding vehicle when said actual distance between two traveling vehicles is shorter than the standard target distance,

said target distance is changed to a provisional target distance to realize said temporary distance control for suppressing the deceleration degree of said succeeding vehicle, and

said provisional target distance has an initial value determined in accordance with the relative speed between said two traveling vehicles and a transitional value gradually restoring to said standard target distance.

84. The recording medium in accordance with claim 81, wherein

a control value is obtained based on a first physical quantity and a second physical quantity, said first physical quantity representing a distance deviation between an actual distance and a target distance between said two traveling vehicles, and said second physical quantity representing a relative speed between said two traveling vehicles,

said succeeding vehicle is accelerated and/or decelerated based on said control value to adjust the actual distance between said two traveling vehicles, and

said temporary distance control is performed to suppress the deceleration degree of said succeeding vehicle when the actual distance between said two traveling vehicles is already shorter or will soon become shorter than the standard target distance due to an intentional driver'"'"'s operation of said succeeding vehicle performed to reduce the actual distance between said two traveling vehicles.

85. A recording medium storing a control program for controlling a warning device, said recording medium being installable in a computer system, and said control program comprising the steps of:

judging whether an actual distance between two traveling vehicles becomes shorter than a predetermined warning distance; and

activating or deactivating said warning device to generate a warning or an alarm based on judgement result,

wherein said control program further comprises the step of performing a temporary warning control for setting a provisional warning distance shorter than an ordinary warning distance when the actual distance between said two traveling vehicles is already shorter or will soon become shorter than said ordinary warning distance due to an intentional driver'"'"'s operation of a succeeding vehicle performed to follow up a new objective traveling on another traffic lane.