JP3430883B2 - Fail-safe device in follow-up running system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a follow-up running system for automatically controlling an accelerator and a brake of a vehicle to adjust a vehicle speed so as to keep an inter-vehicle distance substantially constant, and monitors a driver's arousal level during follow-up running. Fail-safe device.

[0002]

2. Description of the Related Art In recent vehicle control technology, adaptive cruise control (ACC; Adaptive Cruise Control) is performed to automatically control a distance between a preceding vehicle and a preceding vehicle during traveling.
l) has been put to practical use. However, those currently put into practical use are usually provided with a running speed limit of 40 km / h or more.

Further, a traffic jam follow-up control system that follows a preceding vehicle even when traveling at a low speed such as a traffic jam, and a system that automatically controls handling at this time have been proposed. If the operation of the accelerator and the brake (further, the steering wheel) is automated, there is a concern that the driver's arousal level will be considerably reduced because the amount of operation of the driving and the matters to be noticed are considerably reduced.

As a conventional technique for detecting the degree of awakening of a driver, a pressure sensor is provided on the steering wheel to monitor the gripping force thereof (Japanese Patent Laid-Open No. 1-190545, etc.),
A method of monitoring the driver's condition (face orientation) by a visual sensor and image processing (eg, page 87 of the 2nd Image Sensing Symposium Lecture held on June 13 and 14, 1996) has been proposed.

[0005]

However, all of the above-mentioned conventional awakening level detection techniques have the following problems.

(1) That is, firstly, there is a problem that the driver's arousal level cannot always be accurately determined.
First of all, the normal gripping force of the steering varies depending on the driver's individuality and driving situation, and there is a large variation, so even if the gripping force is smaller than the set threshold value, the awakening level will decrease. This is not always the case. In addition, the orientation of the driver's face also varies depending on the driver's personality and driving situation, and it is difficult to determine whether the change is normal or due to a decrease in alertness. .

(2) In any case, there is a problem that a special sensor and a signal processing device are required, and that it takes a considerable cost to realize them.

Therefore, the present invention has been made in view of such conventional problems, can be realized at a low cost, and can reliably judge a decrease in driver's arousal level due to follow-up running especially in a low speed range. It is an object of the present invention to provide a fail-safe device in a follow-up traveling system that can take adaptive measures.

[0009]

In order to achieve the above object, a failsafe device in a follow-up traveling system according to claim 1 is an inter-vehicle distance detecting means for detecting a distance to a preceding vehicle and the inter-vehicle distance in the follow-up traveling mode. In a follow-up traveling system for a vehicle, which comprises a vehicle speed control means for automatically controlling the accelerator and brake of the vehicle to adjust the vehicle speed so as to keep the distance detected by the distance detecting means substantially constant, A fail-safe device for monitoring a driver's arousal level, comprising a shift lever actuator for forcibly actuating a shift lever for switching a running range of an automatic transmission of a vehicle to switch the running range, and a vehicle speed set to a first setting. In the low speed range which is less than the value, the shift lever actuator is controlled to operate the shift lever to force The shift lever control means for switching the position to the first speed range or the second speed range, and the vehicle speed adjusted by the vehicle speed control means unless the shift lever is detected to be in the drive range position is set to the first set value. And a vehicle speed limit control means for restricting the increase so as not to exceed the second set value having the above-mentioned magnitude.

A fail-safe device in a follow-up traveling system according to a second aspect of the invention provides a vehicle-interval distance detecting means for detecting a distance to a preceding vehicle and a distance detected by the inter-vehicle distance detecting means in the follow-up traveling mode to be substantially constant. A vehicle speed control means for automatically controlling the accelerator and brake of the vehicle so as to maintain the vehicle speed, and a vehicle follow-up traveling system comprising a fail-safe device for monitoring the awakening degree of the driver during follow-up traveling. A shift lever actuator for forcibly actuating a shift lever for switching the traveling range of the automatic transmission of the vehicle to switch the traveling range, and a vehicle speed in a low speed range equal to or lower than a first set value. The shift lever actuator is controlled to operate the shift lever to forcibly switch to the position of the first speed range or the second speed range. The shift lever control means and the vehicle speed adjusted by the vehicle speed control means are increased in spite of a situation in which the vehicle speed should be increased beyond a second set value that is greater than or equal to the first set value. Based on the fact that the lever is not detected to be in the drive range position, an awakening degree determining means for determining a decrease in awakening degree of the driver,
It is characterized in that it is provided with an alarm means for giving an alarm to the driver when the driver's awakening degree lowering is judged by the awakening degree judging means.

Further, in the fail-safe device in the follow-up traveling system according to claim 3, the follow-up traveling system comprises:
A steering control means for automatically controlling the steering device of the vehicle in the following traveling mode is further provided.

According to another aspect of the present invention, there is provided a fail-safe device for a follow-up traveling system, wherein the steering control means functions only when the vehicle speed is in a low speed range equal to or lower than the first set value, and the steering device for the vehicle is operated. It is characterized by automatic control.

According to a fifth aspect of the failsafe device in the following traveling system, the warning means gives a warning to the driver by voice.

According to a sixth aspect of the present invention, there is provided the fail-safe device in the following traveling system, wherein the warning means gives a warning to the driver by a warning sound.

According to a seventh aspect of the present invention, there is provided the fail-safe device in the following traveling system, wherein the warning means gives a warning to the driver by displaying characters.

According to another aspect of the fail safe device in the following traveling system, the warning means gives a warning to the driver by displaying an image.

According to a ninth aspect of the present invention, there is provided the fail-safe device in the following traveling system, wherein the alarm means gives a warning by stimulating a driver's sensation due to vibration, smell, or cold air. .

Further, in the fail-safe device in the following traveling system according to claim 10, the alarm means is
The present invention is characterized in that a stimulus to any one or two or more of the sense of hearing and the sense of touch is applied to the driver to give an alarm.

Further, in the fail-safe device in the following traveling system according to claim 11, the first set value is 1
It is characterized in that it is 0 km / h to 20 km / h, and the second set value is 20 km / h to 30 km / h.

[0020]

DETAILED DESCRIPTION OF THE INVENTION An example of an embodiment of the present invention will be described below with reference to the drawings. FIG. 1A is a block diagram showing the main configuration of a follow-up running system to which the fail-safe device of this example is applied. As shown in FIG. 1, the system of this example includes a vehicle speed sensor 1 (vehicle speed detection means), an inter-vehicle distance sensor 2 (inter-vehicle distance detection means), a shift lever position detection device 3 (shift lever position detection means), accelerator/
Brake actuator 4, shift lever actuator 5, alarm device 6 (alarm means), ACC switch 7, control circuit 10 (vehicle speed control means, shift lever control means, vehicle speed limit control means, awakening degree determination means, steering control And)).

Here, the vehicle speed sensor 1 is used in a general vehicle for detecting the output shaft rotational speed of an automatic transmission (not shown) of the vehicle (that is, the rotational speed of a rotating shaft connected to a propeller shaft of the vehicle). This is an existing sensor, and the control circuit 10 detects the vehicle speed from the detection output of this sensor. The inter-vehicle distance sensor 2 is, for example, a radio wave radar or a laser radar,
A sensor device for measuring the distance between the preceding vehicle and the own vehicle,
It is a well-known and existing component in a follow-up traveling system.

The shift lever position detecting device 3 is an existing switch for a general automatic transmission called, for example, an inhibitor switch, and is a shift lever (also referred to as a select lever) for selecting a running mode of the automatic transmission. This is an element that detects the selected position.

The accelerator / brake actuator 4 is
An actuator for forcibly actuating the accelerator or the brake under the control of the control circuit 10 even if the accelerator pedal or the brake pedal is not operated in order to carry out follow-up running, and is a well-known and existing component in the follow-up running system. Is. The shift lever actuator 5 is
In order to realize the fail-safe function of the present invention, the actuator forcibly operates the shift lever under the control of the control circuit 10 even if the shift lever is not operated.

The alarm device 6 gives an alarm to the driver by, for example, voice, alarm sound, character display, or image display, and is specifically composed of a speaker, an LED, or a liquid crystal display. The alarm device 6 may be a device that gives a warning by stimulating the driver's sensation due to vibration, smell, or cold air, or any one of visual sense, auditory sense, and tactile sense, Alternatively, a stimulus for two or more sensations may be applied to the driver to give an alarm.

The ACC switch 7 is an operation switch for instructing the control circuit 7 to shift to the ACC mode (following traveling mode) in which follow-up control is performed by the driver's operation.
When the ACC switch 7 is on, the control circuit 7 determines that the ACC mode is instructed.

In this case, the control circuit 10 is an element constituting various control means and determination means of the present invention. Specifically, the control circuit 10 operates according to a preset program and has a memory for storing various set values. It consists of a microcomputer. The control circuit 10 is characterized in that it performs follow-up running control and control as a fail-safe device by the processing shown in the flowchart of FIG. 2 described later in this case.

Next, the characteristic control processing of the control circuit 10 of this example will be described with reference to the flowchart of FIG. In addition,
The series of processing in FIG. 2 is repeatedly executed at a constant cycle (for example, a cycle of 0.1 second) by the activation of the control circuit 10.

First, in step S2, the ACC switch 7
Of the operation state of, and if it is on, step S6
Otherwise go to step S4. Then, in step S4, an alarm state (alarm device 6
Is operating), the alarm state is released, the alarm device 6 is stopped, and the series of processes is ended.

On the other hand, in step S6, the vehicle speed V0 at that time is determined from the detection output of the vehicle speed sensor 1. Then, in step S8, the set vehicle speed V1 after one cycle (for example, after 0.1 second) is calculated.

In this step S8, the inter-vehicle distance sensor 2
This set vehicle speed V1 is set as a preferable target vehicle speed for maintaining the inter-vehicle distance at a preset constant value from the distance to the preceding vehicle (inter-vehicle distance) detected at that time and the current vehicle speed V0. Desired. When no preceding vehicle is detected, for example, the traveling speed set in advance by the driver or the like when there is no preceding vehicle is the set vehicle speed V.
It is set as 1.

Next, in step S10, the current vehicle speed V0
Is less than or equal to a preset set value (for example, 20 km / h), and it is determined whether or not the condition that the set vehicle speed V1 obtained in step S8 is larger than the set value is satisfied. If this condition is satisfied, step S
12. If not, proceed to step S14.

The set value (for example, 20 km / h) in step S10 corresponds to the second set value of the present invention. Further, in this step S10, it is determined whether or not the vehicle speed is in a state in which the vehicle speed should be increased to a high speed range exceeding the second set value. Is resolved and it is determined whether or not there is a transition situation in which the acceleration is accelerated.

In step S14, if there is an alarm state at that time, the alarm state is released, the alarm device 6 is stopped, and the process proceeds to step S22.

On the other hand, in step S12, the detection output of the shift lever position detecting device 3 is read and it is determined whether or not the traveling mode selected at that time is the drive range (D range). If not, the process proceeds to step S18.

Then, in step S16, if there is an alarm state at that time, the alarm state is released, the alarm device 6 is stopped, and the process proceeds to step S22.

On the other hand, in step S18, the alarm device 6 is activated to enter the alarm state. The contents of the warning here are to inform the driver that the shift lever should be operated to the D range, and to notify the driver that the driver's awakening level has decreased and call attention. Things, as well as measures to increase driver alertness.

It should be noted that the warning in step S18 is the same as when the processing first proceeds to step S18.
The contents may be different depending on whether or not this step S18 is continuously executed every time and a fixed time has elapsed.

For example, at first, the driver is merely informed that the D range should be switched by display or voice, and if step S18 is still executed even after a certain time has passed, the driving is performed. Since it is highly possible that the driver's arousal level is low, a relatively loud warning sound is emitted, and after a certain period of time, vibration is added to the driver's seat to provide stronger awakening. May be taken.

Next, in step S20, the set vehicle speed V1 is forcibly set to the second set value (for example, 20 km / h) regardless of the set value in step S8. As a result, the vehicle speed during follow-up travel is limited to the second set value or less.

Next, in step S22, the accelerator / brake actuator 4 is controlled based on the latest set vehicle speed V1 obtained in step S8 or changed in step S20 and the vehicle speed V0 at that time, The actual vehicle speed is controlled to be substantially equal to the set vehicle speed V1. As a result, it is possible to automatically follow the preceding vehicle or automatically travel at the set speed when there is no preceding vehicle.

Next, in step S24, it is determined whether the latest set vehicle speed V1 is smaller than a set value (for example, 10 km / h). If it is smaller than the set value, the process proceeds to the next step S26.
A series of processing ends. The set value (for example, 10 km / h) here corresponds to the first set value of the present invention. Further, the judgment in step S24 is that the vehicle speed is the first
It is determined whether or not the low speed range is less than or equal to the set value of.

Then, in step S26, the shift lever actuator 5 is controlled to forcibly switch the selected position of the shift lever to the first speed range (or the second speed range), and the series of processing is terminated.

According to the above processing, when the vehicle speed is in the low speed range below the first set value (10 km / h),
The shift lever is forcibly driven by the processing of steps S24 and S26, and the travel range is automatically and forcibly set to 1.
It can be switched to the speed range or the second speed range.

Further, steps S10, S12, S18, S
According to the processing of 20, the situation in which the vehicle speed adjusted for follow-up travel (in this case, the set vehicle speed V1) should be increased beyond the second set value (20 km / h) that is equal to or higher than the first set value However, when it is not detected that the shift lever is in the drive range position, an alarm state is set, the warning is given by the warning device 6, and the vehicle speed adjusted for follow-up running is , Is restricted so as not to increase beyond the second set value (20 km / h).

That is, in this case, steps S10 and S12
By the processing in step S18, S, it is substantially determined that the driver's awakening degree is lowered due to the follow-up running in the low speed range.
At 20, safety measures will be taken in case of reduced alertness. For this reason, an excellent effect that it is possible to reduce a risk due to a decrease in the awakening degree of the driver is obtained particularly when the follow-up running is performed in the low speed range.

That is, in the case of the device of this example, when the follow-up running in the low speed range is performed due to, for example, traffic congestion, the vehicle speed falls below the first set value, and therefore, even if the shift lever is in the D range, The processing of S24 and S26 ensures that the selected position of the shift lever is the first speed or the second speed.

After that, for example, when the congestion is resolved and the vehicle is to be accelerated by following the preceding vehicle, the vehicle speed to be adjusted exceeds the second set value and the determination result of step S10 becomes affirmative. Therefore, the determination process of step S12 comes to be performed. In this case, if the driver grasps this situation and operates the shift lever to the D range, the determination result of step S12 becomes affirmative and the alarm state does not occur (it is not determined that the wakefulness is lowered), or the alarm is once issued. Even if it is in the state, step S16 is executed when the D range is operated and the alarm state is immediately released.

However, for example, when the driver's arousal level is lowered due to the follow-up run in the low speed range up to that point (or the follow-up run in the high speed range before that),
Since the driver cannot operate such a shift lever, the determination result of step S12 becomes negative, and steps S18 and S20 are executed (it is determined that the wakefulness has decreased and the coping measures are taken).

That is, according to the present apparatus, the switching between the general ACC (following running state in the high speed range) and the following running state in the low speed range such as traffic jam follow-up is performed as shown in FIG. 1 (b). When the driver's arousal level has decreased, the driver does not shift from the low-speed range following-up running state to the high-speed range following-up running state, and at the time when such a transition should be made, A drop is reliably determined and the driver is warned. Therefore, especially when the follow-up run is performed in the low speed range, the risk of the driver's awakening can be reliably reduced, and the safety of the follow-up running system that also performs the follow-up run in the low-speed range such as traffic jam follow-up There is an effect that can greatly contribute to the improvement of the property.

Further, as described above, the present apparatus is mainly composed of the existing elements in a general vehicle and the elements already generally used as the constituent elements of the follow-up traveling system, so that it is described as the prior art. Compared with the case of providing such a wakefulness detection device, there is an advantage in practical use that it can be realized at a significantly low cost and the space required in the vehicle is extremely small.

It should be noted that the present invention is not limited to the above-mentioned form example, and may have various forms. For example, the specific numerical values of the first set value and the second set value of the present invention may be appropriately set according to the required safety level and the like. However, considering the generally required safety level (safety speed), the traveling speed in the case of following traffic congestion, etc., the first set value is set to about 10 to 20 km / h, and the second set value is set to 20 It is preferably about 30 km / h.

Further, for example, step S18 in FIG.
It is also possible to delete the processing such as, but not particularly give a warning by the alarm device and only perform speed limitation (for example, the processing of step S20 in FIG. 2). On the contrary, there may be a mode in which only the alarm is issued without the speed limitation. However, it goes without saying that by combining the two, safety can be ensured even when the arousal level is reduced.

Further, for example, as shown by a dotted line in FIG. 1, a steering actuator 8 controlled by a control circuit 10 (steering control means) is provided to automatically control the steering device of the vehicle in the following traveling state. Good. In this case, since the steering wheel operation becomes unnecessary in addition to the operation of the brake and the accelerator, there is a high possibility that the driver's arousal level will be lowered, and the effect of the fail-safe device will be more remarkable.

It should be noted that the automatic control of the steering device is preferably performed only when the vehicle speed is in the low speed range below the first set value. This is because during low-speed follow-up driving, the vehicle speed is low, so the range to be noted is narrow, and there is plenty of processing time, so automatic steering control using image processing technology is relatively easy. However, since it is necessary to pay attention to a wide range in a short time when traveling at high speed, it is relatively difficult to automatically control the steering using high load processing such as image processing technology.

[0055]

According to the fail-safe device in the follow-up running system of the first aspect of the present invention, when the vehicle speed is in the low speed range below the first set value (for example, 10 km / h),
By the operation of the shift lever actuator under the control of the shift lever control means, the shift lever is forcibly driven, and the travel range is automatically and forcibly switched to the first speed range or the second speed range.

When it is not detected that the shift lever is in the drive range position, the vehicle speed adjusted for follow-up running is controlled by the vehicle speed limit control means to the second set value equal to or higher than the first set value. Set value (for example, 20 km
/ H) is not allowed to increase.

Therefore, an excellent effect that the danger due to a decrease in the awakening degree of the driver can be reduced is obtained particularly when the follow-up running is performed in the low speed range. That is, in the case of this device, when the follow-up running is performed in the low speed range due to, for example, traffic congestion, the vehicle speed falls below the first set value, and therefore even if the shift lever is in the D range, The selected position is surely set to the first speed or the second speed by the compulsory switching of the shift lever by the control.

After that, for example, when the traffic is cleared and the vehicle is to be accelerated by following the preceding vehicle, the vehicle speed to be adjusted exceeds the second set value, so the driver grasps this situation. When the shift lever is operated to the D range, the vehicle speed is not limited and the vehicle follows the preceding vehicle to accelerate. However, if the driver neglects to operate the shift lever to the D range, the vehicle speed limit control means The control limits the vehicle speed so as not to exceed the second set value.

That is, for example, in the case where the driver's awakening level is lowered by the follow-up running in the low-speed range up to then (or the follow-up running in the high-speed range before that),
Since the driver cannot operate the shift lever according to such a situation, the vehicle speed limiting control means operates and the vehicle speed is limited to the second set value or less.

Therefore, when the driver's awakening level is low, the follow-up running state in the low speed range is not changed to the follow-up running state in the high speed range, and the follow-up running especially in the low speed range is performed. In addition, it is possible to surely reduce the risk due to a decrease in driver's awakening level, and it is possible to greatly contribute to the improvement of the safety of the follow-up traveling system that also follows the vehicle in a low speed range such as following a traffic jam.

Further, since the present apparatus can be mainly constituted by the elements already existing in a general vehicle or the elements already generally used as the constituent elements of the follow-up traveling system, the awakening degree detecting apparatus as described in the prior art can be realized. Compared with the case where it is provided, there is an advantage in practical use that it can be realized at a significantly lower cost and the space required in the vehicle is extremely small.

Further, in the fail-safe device in the follow-up traveling system according to the second aspect, when the vehicle speed falls within the low speed range below the first set value (for example, 10 km / h), the shift lever control means controls The shift lever is forcibly driven by the operation of the shift lever actuator, and the travel range is automatically and forcibly switched to the first speed range or the second speed range.

Then, the vehicle speed adjusted for follow-up traveling is set to the second set value (20 km / h) which is equal to or higher than the first set value.
If it is not detected that the shift lever is in the drive range position, it is determined by the awakening degree determination means that the driver's awakening degree has decreased, despite the situation that the driver should be increased beyond The alarm means gives the driver an alarm as described in claims 5 to 10, for example.

Therefore, an excellent effect that the danger due to the decrease in the driver's awakening level can be reduced is obtained particularly when the follow-up running is performed in the low speed range. That is, in the case of this device, when the follow-up running is performed in the low speed range due to, for example, traffic congestion, the vehicle speed falls below the first set value, and therefore even if the shift lever is in the D range, The selected position is surely set to the first speed or the second speed by the compulsory switching of the shift lever by the control.

After that, for example, when the traffic is cleared and the vehicle is to be accelerated by following the preceding vehicle, the vehicle speed to be adjusted exceeds the second set value, and therefore the driver grasps this situation. If the shift lever is operated to the D range, it is not determined that the awakening degree is lowered, but if the driver neglects to operate the shift lever to the D range, the awakening degree of the driver is lowered by the awakening degree determination means. Is determined, and the above-mentioned alarm is issued by the alarm means.

That is, for example, when the driver's awakening level is lowered due to the follow-up running in the low speed range up to that point (or the follow-up running in the high speed range before that),
Since the driver cannot operate the shift lever according to such a situation, the alarm means is activated and an alarm is issued.

Therefore, when the driver's awakening level is decreasing, the decrease in the awakening level is surely determined at the time of shifting from the following running state in the low speed range to the following running state in the high speed range. When a warning is given to the driver and the follow-up run is performed especially in the low speed range, the risk due to the driver's awakening level can be reliably reduced, and the follow-up run in the low-speed range such as traffic jam follow-up can also be performed. There is an effect that can greatly contribute to improving the safety of the following traveling system.

Further, since this apparatus can be mainly constituted by the elements already existing in a general vehicle and the elements already generally used as the constituent elements of the follow-up traveling system, the awakening degree detecting apparatus as described in the prior art can be used. Compared with the case where it is provided, there is an advantage in practical use that it can be realized at a significantly lower cost and the space required in the vehicle is extremely small.

When the steering control means for automatically controlling the steering device of the vehicle in the following traveling mode is further provided as described in claim 3 or 4,
Since the steering device of the vehicle is automatically controlled, the driver's steering wheel becomes unnecessary and the burden on the driver can be further reduced.
In this case, the driver's arousal level is more likely to decrease, so that the effect of the fail-safe device of the present invention on the decrease in the arousal level becomes more remarkable.

When the steering control means is made to function only when the vehicle speed is in the low speed range equal to or lower than the first set value, the automatic control of the steering device is performed. Therefore, the burden of image processing and the like can be reduced, and the practicality is further improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a follow-up traveling system that is an example of the present invention.

FIG. 2 is a flowchart showing processing contents of a fail-safe device of the system.

[Explanation of symbols]

1 vehicle speed sensor (vehicle speed detection means) 2 inter-vehicle distance sensor (inter-vehicle distance detection means) 3 shift lever position detection device (shift lever position detection means) 4 accelerator / brake actuator 5 shift lever actuator 6 alarm device (alarm means) 7 ACC switch 8 Steering actuator 10 Control circuit (vehicle speed control means, shift lever control means, vehicle speed limit control means, awakening degree determination means, steering control means)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ identification code FI F16H 61/02 F16H 61/02 (58) Fields investigated (Int.Cl. ⁷ , DB name) B60T ^7/ 12-7/22 B60T 8/00-8/96 F16H 61/02 B60K 28/06 B60K 31/00 B60K 41/06 F02D 29/02

Claims (10)

(57) [Claims] 1. An inter-vehicle distance detecting means for detecting a distance to a preceding vehicle, and an accelerator and a brake of a vehicle are automatically controlled so that a distance detected by the inter-vehicle distance detecting means in a following traveling mode is kept substantially constant. A vehicle follow-up traveling system comprising a vehicle speed control means for adjusting a vehicle speed, which is a fail-safe device for monitoring a driver's awakening level during follow-up traveling, and switches a traveling range of an automatic transmission of the vehicle. When a shift lever actuator forcibly operating the shift lever to switch the traveling range and a vehicle speed in a low speed range equal to or lower than a first set value,
Shift lever control means for controlling the shift lever actuator to operate the shift lever to forcibly switch to the position of the first speed range or the second speed range; and unless it is detected that the shift lever is in the drive range position. A vehicle speed limiting control means for limiting the vehicle speed adjusted by the vehicle speed control means so as not to increase beyond a second set value which is greater than the first set value. Fail-safe device for traveling system. 2. An inter-vehicle distance detecting means for detecting a distance to a preceding vehicle, and an accelerator and a brake of the vehicle are automatically controlled so that the distance detected by the inter-vehicle distance detecting means in the following traveling mode is kept substantially constant. A vehicle follow-up traveling system comprising a vehicle speed control means for adjusting a vehicle speed, which is a fail-safe device for monitoring a driver's awakening level during follow-up traveling, and switches a traveling range of an automatic transmission of the vehicle. When a shift lever actuator forcibly operating the shift lever to switch the traveling range and a vehicle speed in a low speed range equal to or lower than a first set value,
The shift lever control means for controlling the shift lever actuator to operate the shift lever to forcibly switch to the position of the first speed range or the second speed range, and the vehicle speed adjusted by the vehicle speed control means are The driver's arousal level is based on the fact that the shift lever is not detected to be in the drive range position, even though the second set value larger than the set value should be increased. A fail in a follow-up running system comprising: an awakening degree determining means for determining a decrease; and an alerting means for giving a warning to the driver when the awakening degree determining means determines a decrease in the driver's awakening degree. Safe device. 3. The fail safe device according to claim 1, wherein the follow-up traveling system further comprises steering control means for automatically controlling a steering device of the vehicle in the follow-up traveling mode. 4. The steering control means functions only when the vehicle speed is in a low speed range equal to or lower than the first set value, and automatically controls the steering device of the vehicle. Fail-safe device in the follow-up system. 5. The fail-safe device in a follow-up traveling system according to claim 2, wherein the alarm means gives an alarm to the driver by voice. 6. The fail-safe device in a follow-up running system according to claim 2, wherein the warning means gives a warning to the driver by a warning sound. 7. The fail-safe device in a follow-up running system according to claim 2, wherein the warning means gives a warning to the driver by displaying characters. 8. The fail-safe device in a follow-up running system according to claim 2, wherein the warning means gives a warning to the driver by displaying an image. 9. The fail-safe device in a follow-up running system according to claim 2, wherein the alarm means gives an alarm by stimulating the driver's sensation by vibration, smell, or cold air. 10. The warning means gives a warning to the driver by applying a stimulus to one or two or more senses of sight, hearing, and touch. A fail-safe device in the following traveling system according to Item 2.