JPH0772245A - Car-mounted collision-prevention warning device - Google Patents

Abstract

PURPOSE:To generate a warning at the relative distance matching the driver's sensation. CONSTITUTION:An antenna part 1 is provided with a transmitting part 2 for transmitting electromagnetic waves and a receiving parts 3 for receiving the electromagnetic waves reflected from forward obstacles. The received signal is outputted into a signal processing part 4. In the signal processing part 4, a relative distance R to a preceding vehicle and a relative speed Vr between own vehicle and the preceding vehicle are operated on the basis of the input signals. The results are outputted into an MCU 10. A vehicle speed sensor 6 detects a running speed V1 and outputs the speed into the MCU 10. A ROM 11 stores the three-dimensional map, the deceleration in response to the running speed V1 and the relative distance R and the free running time are set. The deceleration and the running time are operated by the method of least squares in nonlinear form for the value based on the running speed V1 and the relative distance R, which are judged by the driver as real danger in experiment. The results are stored in the memory.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle collision prevention alarm device.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 3, a driver driving a vehicle collides with an obstacle such as an own vehicle 51 and an obstacle such as a preceding vehicle 52 traveling in front of the own vehicle 51 or a stopped vehicle. It may be difficult to determine whether the distance is dangerous. Therefore, for the own vehicle 51, the relative distance R between the driving own vehicle 51 and the preceding vehicle 52 traveling ahead is measured, and the relative distance R is measured.
An anti-collision warning device has been proposed which issues a warning in response to the warning and informs the driver of caution or danger information.

As shown in FIG. 4, a collision prevention warning device 53 is provided.
Is composed of a laser sensor 54, a display 55 and a vehicle speed sensor 56. The laser sensor 54 is provided in the lower front part of the vehicle 51 and irradiates infrared laser light to the front.
It mainly receives the reflected light from the reflex reflector 57 of the preceding vehicle 52. The laser sensor 54 receives the reflected light and receives the relative distance R from the preceding vehicle 52 and the own vehicle 51.
The relative speed Vr between the vehicle and the preceding vehicle 52 is measured, and the relative distance R and the relative speed Vr are output to the display 55.

The display 55 is provided in a driver's seat (not shown) and displays the input relative distance R.
A vehicle speed sensor 56 is connected to the display 55 to detect the traveling speed V1 of the vehicle 51.

The indicator 55 indicates that the vehicle 51 is the preceding vehicle 52 based on the detected traveling speed V1 and relative speed Vr.
The safety distance D that does not collide with is calculated by the safety distance calculation formula. The safety distance calculation formula is shown below.

D = V ₁ · T + Vr ² / 2a + V ₁ · Vr / a where T is idle time and a is deceleration. The deceleration a is a negative acceleration when the traveling speed of the vehicle is reduced by depressing the brake 7, and is always a negative value. The idle running time T is the time from when the driver hears the warning to when the driver steps on the brake. The free running time T and the deceleration a are preset to be constant through experiments or the like. And the relative speed V
r has a negative value when the host vehicle 51 approaches the preceding vehicle 52, and has a positive value when the host vehicle 51 moves away from the preceding vehicle 52.

The display 55 compares the calculated safety distance D with the detected relative distance R. As a result, the relative distance R
Is less than or equal to the safety distance D, the display 55 informs the driver of the alarm by the built-in display element 58 and speaker 59.

[0008]

By the way, the driving speed V1 is low and the driver pays sufficient attention to the preceding vehicle 52 as in the case of a traffic jam.
1 can be stopped, so that the driver can set the traveling speed V
In some cases, the relative distance R may be shortened with respect to 1.
However, since the deceleration a and the idle running time T are set constant with respect to the running speed V1, the calculated safe distance D is long. As a result, the relative distance R becomes less than or equal to the safety distance D, so that there is a problem in that, unlike the driver's sensation, a danger warning continues to be generated while the vehicle is traveling, which hinders driving.

An object of the present invention is to provide a vehicle-mounted collision prevention warning device capable of issuing a warning at a distance that matches the driver's sense.

[0010]

In order to solve the above problems, the invention according to claim 1 is to provide a relative distance for detecting a relative distance between a speed detecting means for detecting a traveling speed and an obstacle in front. Detecting means, detecting means for detecting relative speed with respect to an obstacle, safe distance calculating means for calculating a safe distance by the detected running speed and relative speed, idle running time and deceleration, and the safe distance In a vehicle-mounted collision prevention alarm device provided with a comparison means for comparing a relative distance and an alarm signal output means for outputting an alarm signal when the relative distance is equal to or less than a safe distance based on the comparison result of the comparison means. A storage means for storing a plurality of pairs of deceleration and idle running time corresponding to each traveling speed and each relative distance; and a plurality of pairs of deceleration and idle running time stored in the storage means. Traveling speed and Selecting means for selecting a pair of deceleration and free running time corresponding to the pair distance, and deceleration for calculating a safe distance by the safe distance calculating means based on the deceleration and free running time selected by the selecting means, The gist is that the rewriting means for rewriting the free running time is provided.

Further, the invention according to claim 2 is a speed detecting means for detecting a traveling speed, a relative distance detecting means for detecting a relative distance to an obstacle ahead, and a relative speed to the obstacle. Detecting means, a safe distance calculating means for calculating a safe distance by the detected running speed and relative speed, idle running time and deceleration, comparing means for comparing the safe distance and relative distance, and the comparison An in-vehicle collision prevention warning device provided with warning signal output means for outputting a warning signal when the relative distance is less than or equal to the safety distance based on the comparison result of the means, corresponding to each traveling speed and each relative distance. The storage means for storing the plurality of decelerations, the selection means for selecting the deceleration corresponding to the traveling speed and the relative distance at that time among the plurality of decelerations stored in the storage means, and the selection means for selecting. Was based on the deceleration, the gist in that a rewriting means for rewriting the deceleration for calculating a safe distance by the safety distance calculating means.

Further, the invention according to claim 3 is such that a speed detecting means for detecting a traveling speed, a relative distance detecting means for detecting a relative distance to an obstacle ahead, and a relative speed to the obstacle are detected. Detecting means, a safe distance calculating means for calculating a safe distance by the detected running speed and relative speed, idle running time and deceleration, comparing means for comparing the safe distance and relative distance, and the comparison An in-vehicle collision prevention warning device provided with warning signal output means for outputting a warning signal when the relative distance is less than or equal to the safety distance based on the comparison result of the means, corresponding to each traveling speed and each relative distance. Storage means for storing the plurality of idle running times, selection means for selecting the idle running time corresponding to the running speed and relative distance at that time among the plurality of idle running times stored in the storage means, and the selection means Based on the selected empty run time, and summarized in that provided with rewriting means for rewriting the empty run time for calculating a safe distance by the safety distance calculating means.

Further, the deceleration is obtained by a traveling experiment of a plurality of drivers, based on respective data of a relative velocity with respect to an obstacle when the drivers feel dangerous, a traveling velocity and a relative distance. Further, the idle running time is obtained by a running experiment of a plurality of drivers based on each data of a relative speed with respect to an obstacle when the driver feels dangerous, a running speed, and a relative distance.

[0014]

According to the invention described in claim 1, of the plurality of pairs of deceleration and idle running time stored in the storage means, a pair of deceleration and idle running time corresponding to the running speed and relative distance at that time. Is selected, a safety distance is calculated based on the deceleration and idle running time, and an alarm signal is output based on the calculated result and the detected relative distance, so it corresponds to the running speed and relative distance. An alarm can be generated at any distance.

According to the second aspect of the invention, the deceleration corresponding to the traveling speed and the relative distance at that time is selected from among the plurality of decelerations stored in the storage means, and based on the deceleration. Since the safety distance is calculated based on the calculated result and the detected relative distance, an alarm signal can be generated at a distance corresponding to the traveling speed and the relative distance.

According to the third aspect of the invention, the idle running time corresponding to the running speed and the relative distance at that time is selected from the plurality of idle running times stored in the storage means, and the idle running is selected. Since the safety distance is calculated based on time and the warning signal is output based on the calculated result and the detected relative distance, the warning can be generated at the distance corresponding to the traveling speed and the relative distance. .

Further, the deceleration can be obtained on the basis of data of the relative speed with respect to the obstacle when the driver feels dangerous, the traveling speed and the relative distance by a running experiment of a plurality of drivers. It is possible to issue an alarm at a relative distance suitable for the sense of.

Further, since the free running time is obtained on the basis of each data of the relative speed with respect to the obstacle when the driver feels dangerous, the traveling speed and the relative distance by the running experiment of a plurality of drivers, It is possible to generate an alarm at a relative distance suitable for a person's sense.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment embodying the present invention will be described below with reference to FIGS. As shown in FIG. 1, the antenna section 1 of the vehicle collision prevention warning device is provided in the lower front portion of a vehicle body (not shown) such as a truck. The antenna 1 is a laser sensor, which is provided with a transmitter 2 and a receiver 3 and is connected to a signal processor 4. The signal processing unit 4 is connected to the alarm determination unit 5.

The transmitting section 2 of the antenna section 1 transmits an electromagnetic wave such as an infrared laser toward the front of the vehicle body, and the receiving section 3 receives the electromagnetic wave reflected by the preceding vehicle 52 in front. Then, the antenna section 1 outputs the signal of the electromagnetic wave received by the receiving section 3 to the signal processing section 4.

The signal processing section 4 calculates the relative distance R between the own vehicle 51 and the preceding vehicle 52 at a predetermined time interval based on the input electromagnetic wave signal, and outputs it to the alarm determination section 5. Further, the signal processing unit 4 calculates the relative speed Vr of the own vehicle 51 and the preceding vehicle 52 based on the calculated relative distance R,
It outputs to the alarm determination unit 5.

A vehicle speed sensor 6 is provided on the vehicle body, and the vehicle speed sensor 6 is connected to the alarm determination unit 5. The vehicle speed sensor 6 detects the traveling speed V1 of the host vehicle 51, and the alarm determination unit 5
Output to.

An alarm generation unit 7 is connected to the alarm determination unit 5. The alarm generator 7 has a display 8 and a speaker 9
Is provided. Next, the electrical configuration of the vehicle-mounted collision warning device will be described.

The control circuit is a control unit (hereinafter referred to as MCU)
10, read-only memory (hereinafter referred to as ROM) 11,
It is composed of a readable / writable memory (hereinafter referred to as RAM) 12 and an interface 13.
The interface 13 has a vehicle speed sensor 6 provided on the vehicle body.
Are connected. The interface 13 is the vehicle speed sensor 6
The traveling speed V1 detected in step 1 is output to the MCU 10.

The signal processing unit 4 provided in the antenna unit 1 is connected to the MCU 10, and the relative distance R and the relative speed Vr calculated by the signal processing unit 4 are input. As shown in FIG. 2, the ROM 11 stores a three-dimensional map showing the characteristics of the deceleration a and the idle time T according to the traveling speed V1 and the relative distance R. The traveling speed V1 is divided into a plurality of predetermined speeds, and the relative distance R is divided into a plurality of predetermined distances. Then, a pair of deceleration a and idle running time T corresponding to each divided traveling speed V1 and relative distance R are stored. In this embodiment, the traveling speed V1
Between 0 and 100 km / h is divided every 20 km / h, and the relative distance R is between 0 and 100 m every 20 m.

The deceleration a and the idle time T are set by an actual running experiment by a plurality of drivers. The deceleration a is set so that the value of the deceleration a becomes smaller as the value becomes larger with respect to the traveling speed V1, and the value of the deceleration a becomes smaller as the value becomes longer with respect to the relative distance R. It is set. The free running time T is set so that the value of the free running time T increases as the value increases with respect to the running speed V1, and the value of the free running time T increases as the value increases with respect to the relative distance R. It is set to be large. Therefore, in this embodiment, the deceleration a is set to be the largest deceleration a _{11 and the} largest deceleration a ₅₅ . The free running time T is the free running time T ₁₁
Is the smallest and the free running time T ₅₅ is the largest.

In this embodiment, the data of the traveling speed V1, the relative speed Vr and the relative distance R obtained when the driver feels dangerous by the actual traveling experiment by a plurality of drivers. Is calculated using the nonlinear least squares method.

The MCU 10 reads a pair of deceleration a and idle time T corresponding to the detected traveling speed V1 and relative distance R from the three-dimensional map and stores them in the RAM 12. At this time, if the deceleration a and the idling time T are already stored, the stored deceleration a and the idling time T are replaced with the deceleration a and the idling time T read from the ROM 11. Then, the MCU 10 calculates the safety distance D based on the detected traveling speed V1 and relative speed Vr, the deceleration a stored in the RAM 12, and the idle time T based on the safety distance calculation formula. The safety distance calculation formula is shown below.

[0029] ^{D = V1 · T + Vr 2} / 2a + Vr · V1 / a and, MCU 10 compares the relative distance R detected as safe distance D computed. As a result, if the relative distance R is less than or equal to the safety distance D multiplied by a predetermined coefficient, M
The CU 10 outputs the caution warning signal SW to the warning generation unit 7. If the relative distance R is less than or equal to the safety distance D, M
The CU 10 outputs the danger warning signal SK to the warning generation unit 7.

The alarm generator 7 receives the respective alarm signals S inputted.
A display corresponding to W and SK is displayed on the display unit 8 and a sound corresponding to each alarm signal SW and SK is generated from the speaker 9.

Next, the operation of the vehicle-mounted collision prevention alarm device constructed as described above will be described. When the driver starts the engine of the truck and drives the truck, the antenna 1
Transmits an electromagnetic wave from the transmitter 2 toward the front of the vehicle body. The electromagnetic wave is reflected by the preceding vehicle 52 traveling ahead and is received by the receiving unit 3, and the signal of the received electromagnetic wave is output from the antenna unit 1 to the signal processing unit 4.

The signal processing unit 4 calculates the relative distance R from the own vehicle 51 to the preceding vehicle 52 based on the input electromagnetic wave signal,
The relative speed Vr between the own vehicle 51 and the preceding vehicle 52 is detected, and M
Output to CU10. On the other hand, the vehicle speed sensor 6 detects the traveling speed V1 of the traveling truck and outputs the traveling speed V1 to the MCU 10 via the interface 13. MC
U10 temporarily stores the input relative distance R, relative speed Vr and traveling speed V1 in the RAM 12.

Next, the MCU 10 inputs the traveling speed V1 and the relative distance R input from the three-dimensional map stored in the ROM 11.
The deceleration a and the idle time T corresponding to
Store in M12. At this time, if the deceleration a and the idling time T are already stored in the RAM 12, the stored deceleration a and the idling time T and the deceleration a and the idling time T read from the ROM 11 are stored. replace. Then, the MCU 10 uses the traveling speed V1 stored in the RAM 12
The safety distance D is calculated from the relative speed Vr, the free running time T and the deceleration a.

When the vehicle approaches the preceding vehicle 52 and the relative distance R becomes less than or equal to the distance obtained by multiplying the safety distance D by a predetermined count, M
The CU 10 outputs the caution warning signal SW to the warning generation unit 7. The alarm generation unit 7 issues a caution alarm based on the caution alarm signal SW. Then, when the vehicle approaches the preceding vehicle 52 and the relative distance R becomes equal to or less than the safety distance D, the MCU 10 outputs the danger warning signal SK to the warning generation unit 7. The alarm generator 7 issues a danger alarm based on the danger alarm signal SK.

At this time, the idling time T is obtained from the traveling speed V1 and the relative distance R when the driver actually determines that it is dangerous by the experiment, and therefore the relative distance R when the alarm is issued. Is a value suitable for the driver's sense of danger.

Generally, when the driver's vehicle 51 is traveling at a low speed due to traffic congestion or the like, the relative distance R to the preceding vehicle 52 is R.
Also becomes smaller. Therefore, the MCU 10 has its running speed V1.
And a pair of deceleration a ₁₁ and idle running time T ₁₁ corresponding to the relative distance R and the relative distance R. Then, the MCU 10 uses the pair of deceleration a ₁₁ and the idle running time T ₁₁ and the detected running speed V 1
Based on the relative distance R and the relative speed Vr, the safety distance D is calculated by the safety distance calculation formula. At this time, deceleration a
_{Since 11} is large and free running time T ₁₁ is small, safety distance D
Becomes smaller. Further, the safety distance D has a value suitable for the driver's sense of low speed driving. When the relative distance R is less than or equal to the safety distance D, the MCU 10 outputs an alarm signal, so that the alarm can be issued at the relative distance R that matches the driver's sense.

In the vehicle-mounted collision prevention alarm device of this embodiment, the deceleration a corresponding to the traveling speed V1 and the relative distance R is used.
And the free running time T are read from the ROM 11, and the safety distance D is calculated based on the deceleration a, the free running time T, the running speed V1 and the relative speed Vr. Then, the relative distance R and the safety distance D are compared, and an alarm is generated based on the result. Therefore, an alarm corresponding to the traveling speed V1 and the relative distance R can be generated.

Further, the deceleration a and the idle time T are calculated based on the traveling speed V1 and the relative distance R when the driver actually judges that the driver is actually dangerous by the traveling experiment, and the ROM 11
Remembered in. Since the safety distance D is calculated based on the stored deceleration a and free running time T,
An alarm can be issued at a traveling speed V1 and a relative distance R that match the driver's sense.

Further, during low speed traveling, the deceleration a ₁₁ stored in the ROM ₁₁ is large and the idling time T ₁₁ is small, and the safety distance D as the calculation result becomes short, so the alarm continues to be issued at low speed. Can be prevented.

The present invention is not limited to the above embodiments, but may be modified as follows without departing from the spirit of the present invention. (1) In the above embodiment, the vehicle collision prevention warning device of the present invention is provided in the truck, but it may be provided in another vehicle such as a passenger car.

(2) In the above embodiment, the relative distance R to the preceding vehicle 52 and the relative speed Vr are detected using an electromagnetic wave which is an infrared laser, but it may be detected using an electromagnetic wave having another frequency. . Alternatively, it may be detected by a sound wave or the like.

(3) In the above embodiment, the detected traveling speed V1, relative speed Vr, and relative distance R are temporarily stored in the RAM 12.
Stored in RAM 12, but not stored in RAM 12
May be calculated. Further, the safety distance D may be calculated without storing the deceleration a and the free running time T read from the ROM 11 in the RAM 12.

(4) In the above embodiment, the deceleration a and the idle time T corresponding to the divided traveling speeds V1 and relative distances R are divided.
Was stored in the ROM 11, but the deceleration a was stored in the ROM 11 as a predetermined constant value, and the free running time T corresponding to the deceleration a and the relative speed V1 and the relative distance R at that time.
The safety distance D may be calculated by using. Further, the deceleration a is set to a value corresponding to either the relative distance R or the traveling speed V1 and stored in the ROM 11, and the deceleration a and the idle time T corresponding to the traveling speed V1 and the relative distance R at that time are stored. The safety distance D may be calculated based on

Further, the free running time T is stored in the ROM 11 as a predetermined constant value, and the safe distance D is calculated by the free running time T and the deceleration a corresponding to the relative speed V1 and the relative distance R at that time. You may do it. Further, the idle running time T is set to a value corresponding to either the relative distance R or the running speed V1 and stored in the ROM 11, and the deceleration a and the idle running time according to the running speed V1 and the relative distance R at that time are stored. The safety distance D may be calculated based on T.

(5) In the above embodiment, the signal processor 4 receives the relative distance R and the relative speed V based on the signal from the antenna 1.
Although r is calculated, the signal is directly input to MCU10, and MC
The relative distance R and the relative speed Vr may be calculated in U10.

(6) In addition to the brake sensor 8, a steering sensor may be provided to stop the alarm generation or change the detection distance based on the operation angle. That is, an alarm is not issued for an extra obstacle at a curve or an intersection.

(7) In the above embodiment, the traveling speed V1 of the three-dimensional map is divided every 20 km / h, but it is 10 km / h.
You may make it divide | segment by arbitrary values, such as every. Also, 0
You may make it change suitably between -100 km / h.

(8) In the above embodiment, the relative distance R of the three-dimensional map is divided every 20 m, but it may be divided at any value such as every 10 m. Moreover, you may make it change suitably between 0-100m.

[0049]

As described above in detail, according to the vehicle-mounted collision prevention alarm device of the first aspect, among the plurality of pairs of deceleration and idle running time stored in the storage means, the running speed and Select a pair of deceleration and free running time corresponding to the relative distance, calculate a safety distance based on the deceleration and free running time, and output an alarm signal based on the calculation result and the detected relative distance As a result, the excellent effect that the alarm can be generated at a distance corresponding to the traveling speed and the relative distance is achieved.

According to the vehicle-mounted collision prevention alarm device of the present invention, the deceleration corresponding to the traveling speed and the relative distance at that time is selected from among the plurality of decelerations stored in the storage means. Since the safety distance is calculated based on the deceleration and the warning signal is output based on the calculation result and the detected relative distance, the warning can be generated at the distance corresponding to the traveling speed and the relative distance. It has an excellent effect that

According to the vehicle-mounted collision prevention alarm device of the present invention, the idling time corresponding to the traveling speed and the relative distance at that time is selected from the plurality of idling times stored in the storage means. Then, the safety distance is calculated based on the free running time, and an alarm signal is output based on the calculated result and the detected relative distance, so an alarm is issued at a distance corresponding to the traveling speed and the relative distance. It has an excellent effect that it can be generated.

Further, the deceleration is obtained based on the data of the relative speed with respect to the obstacle when the driver feels dangerous, the traveling speed, and the relative distance by the traveling experiment of the plurality of drivers. It has an excellent effect that an alarm can be generated at a relative distance suitable for the sense of.

Since the idle running time is obtained on the basis of the data of the relative speed with respect to the obstacle when the driver feels dangerous, the running speed and the relative distance by a running experiment of a plurality of drivers, It has an excellent effect that an alarm can be generated at a relative distance suitable for a person's sense.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of a vehicle collision prevention warning device according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a three-dimensional map of the present invention.

FIG. 3 is a schematic plan view showing a relationship between a vehicle and a preceding vehicle.

FIG. 4 is a schematic view showing a conventional collision prevention warning device.

[Explanation of symbols]

R ... Relative distance, Vr ... Relative speed, V1 ... Travel speed, D ...
Safety distance, a ... deceleration, T ... free running time, 10 ... selection means, safety distance calculation means, MCU as comparison means and alarm signal output means, 11 ... ROM as storage means, 12
... RAM.

Claims (5)

[Claims] 1. A speed detecting means for detecting a traveling speed, a relative distance detecting means for detecting a relative distance to an obstacle ahead, a detecting means for detecting a relative speed to an obstacle, and the detected traveling. Speed and relative speed, safety distance calculation means for calculating a safety distance by free running time and deceleration, comparison means for comparing the safety distance and relative distance, based on the comparison result of the comparison means, relative, In a vehicle-mounted collision prevention alarm device provided with an alarm signal output means for outputting an alarm signal when the distance is equal to or less than a safe distance, a plurality of pairs of deceleration and idle running corresponding to each traveling speed and each relative distance are provided. A storage unit for storing time, and a selection unit for selecting a pair of deceleration and idle running time corresponding to the running speed and relative distance at that time among a plurality of pairs of deceleration and idle running time stored in the storage unit. When An in-vehicle collision prevention alarm device comprising: a rewriting unit that rewrites the deceleration and the free running time for calculating the safe distance by the safe distance calculating unit based on the deceleration and the free running time selected by the selecting unit. 2. A speed detecting means for detecting a traveling speed, a relative distance detecting means for detecting a relative distance to an obstacle ahead, a detecting means for detecting a relative speed to the obstacle, and the detected traveling. Speed and relative speed, safety distance calculation means for calculating a safety distance by free running time and deceleration, comparison means for comparing the safety distance and relative distance, based on the comparison result of the comparison means, relative, In a vehicle-mounted collision prevention alarm device provided with an alarm signal output means for outputting an alarm signal when the distance is equal to or less than a safe distance, a memory for storing a plurality of decelerations corresponding to each traveling speed and each relative distance. Means, selecting means for selecting a deceleration corresponding to the traveling speed and relative distance at that time from among the plurality of decelerations stored in the storage means, and based on the deceleration selected by the selecting means, Safe distance automotive anti-collision warning apparatus provided with a rewriting means for rewriting the deceleration for calculating a safe distance by calculating means. 3. A speed detecting means for detecting a traveling speed, a relative distance detecting means for detecting a relative distance to an obstacle ahead, a detecting means for detecting a relative speed to the obstacle, and the detected traveling. Speed and relative speed, safety distance calculation means for calculating a safety distance by free running time and deceleration, comparison means for comparing the safety distance and relative distance, based on the comparison result of the comparison means, relative, An in-vehicle collision prevention warning device provided with a warning signal output means for outputting a warning signal when a distance is equal to or less than a safe distance, and stores a plurality of idle running times corresponding to each traveling speed and each relative distance. A storage unit, a selection unit for selecting a free running time corresponding to a running speed and a relative distance at that time among a plurality of free running times stored in the storage unit, and a free running time selected by the selection unit. Each Te, said safety distance vehicle anti-collision warning apparatus provided with a rewriting means for rewriting the empty run time for calculating a safe distance by calculating means. 4. The deceleration is obtained by a traveling experiment of a plurality of drivers based on respective data of a relative velocity with an obstacle when the drivers feel dangerous, a traveling velocity and a relative distance. The vehicle-mounted collision prevention alarm device according to claim 1 or 2. 5. The idle running time is obtained based on data of a relative speed with respect to an obstacle when the driver feels dangerous, a running speed, and a relative distance by a running test of a plurality of drivers. The vehicle-mounted collision prevention alarm device according to claim 1 or 3.