JP3872033B2 - Rear side warning device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rear side alarm device that detects an obstacle such as a vehicle existing behind a traveling vehicle and issues an alarm.
[0002]
[Prior art]
Conventionally, this type of rear side warning device is equipped with a distance measuring sensor or the like in order to prevent an accident while the vehicle is running, detects obstacles around the vehicle, and notifies the driver. This distance measuring sensor monitors a rearward direction in a direction in which the lane of the vehicle is changed, and detects a subsequent vehicle in that direction. In this device, a lane change instruction operation is detected, and when this instruction operation is performed, it is determined whether or not the following vehicle is in a predetermined region, and an overtaking danger warning is issued according to the determination result. (For example, refer to Patent Document 1).
[0003]
In addition, another rear side warning device identifies a vehicle traveling situation based on information such as a steering angle, a yaw rate sensor, and navigation, and detects an object in a direction suitable for the traveling situation. Control is performed to issue an alarm when an object is detected (see, for example, Patent Document 2).
[0004]
However, these conventional rear side warning devices issue a warning to all that enter a predetermined area. For example, they issue a warning to guardrails and barriers, which is troublesome to the passengers. There was a problem.
Therefore, a rear side warning device that suppresses false alarms such as guardrails prevents false alarms when the vehicle is traveling along a lane, and reliably alerts when there is a possibility of contact with an obstacle ( For example, see Patent Document 3.)
[0005]
[Patent Document 1]
JP 54-1118036 A [Patent Document 2]
JP 2000-233699 A [Patent Document 3]
JP-A-2002-274303 [0006]
[Problems to be solved by the invention]
However, in order to detect that the vehicle is traveling along the lane, expensive additional devices such as a yaw rate sensor and a navigation system are required.
[0007]
An object of the present invention is to provide a rear side alarm device that can prevent a false alarm due to a guard rail or the like without requiring an expensive additional device.
[0008]
[Means for Solving the Problems]
A rear side warning device according to the present invention includes a distance measuring means for measuring an object distance between an own vehicle and an object existing on the rear side, a lane change detecting means for detecting a lane change of the own vehicle, and the own vehicle. An alarm distance setting means for setting an alarm distance from the alarm distance and an alarm processing means for comparing the alarm distance with the object distance on the lane change side and determining that an alarm is generated when the object distance is smaller than the alarm distance. The setting means sets the warning distance as a first warning distance that is predetermined in synchronization with the detection of the lane change, and a second warning distance that is predetermined in inverse proportion to the elapsed time from the detection of the lane change. Is set to be constant at the second alarm distance.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
FIG. 1 is a configuration diagram of a rear side alarm device according to Embodiment 1 of the present invention. FIG. 2 is a flowchart of the operation of the alarm processing means of FIG. FIG. 3 is a situation diagram in which the vehicle changes lanes. FIG. 4 shows a flowchart of the operation of the lane change detection means. FIG. 5 is a relationship diagram between the alarm distance and the time from the start of lane change.
In this description, an object means both a stationary object such as a stationary guardrail, roadside wall, and sound insulation board around the road, and a moving object such as another vehicle traveling on the road. .
[0010]
The rear side warning device includes a right distance measuring sensor 1 for measuring an object distance between an object and the own vehicle over a range on the right side of the own vehicle, and an object and the own vehicle over a range on the left side of the own vehicle. A distance measuring means 3 having a left distance measuring sensor 2 for measuring an object distance from a vehicle, distance information emitted from the distance measuring means 3 and an alarm processing means 4 for controlling a rear side alarm device; It has distance information via the alarm processing means 4 and also has a lane change detection means 6 for inputting a signal from the direction indicator 5 and detecting a lane change. The distance measuring means 3 measures the object distance between the object and the host vehicle at intervals of several tens of msec and outputs the distance to the alarm processing means 4 as distance information.
[0011]
The lane change detection means 6 detects a signal from the direction indicator 5, and simultaneously stores the distance storage means 7 for storing distance information emitted from the right distance measuring sensor 1 and the left distance measuring sensor 2, and the stored left and right Distance difference calculation means 8 for calculating the difference between the reference distance and the object distance between the vehicle and the object obtained by distance measurement by the left and right distance measurement sensors 1 and 2 at regular intervals (for example, several tens of milliseconds). have.
[0012]
Further, the rear side warning device includes an alarm distance setting means 9 for setting an alarm distance from the host vehicle based on information on a lane change from the lane change detection means 6, an alarm distance storage means 10 for storing the alarm distance, and There is an alarm means 11 for alarming the driver.
The distance measuring means 3 may be a laser light or radio wave type distance measuring sensor that has been conventionally used. However, the distance measuring means 3 is not particularly limited to this, and anything may be used.
[0013]
Next, the alarm processing procedure will be described with reference to FIG. First, in step (hereinafter abbreviated as S) 101, the left and right distance measuring sensors 1 and 2 measure the object distance between the object and the host vehicle and input the distance to the alarm processing means 4. Next, in S102, the lane change detection means 6 performs a lane change detection process. In S103, the warning distance setting means 9 sets the warning distance based on the result of the lane change detection process. In S104, the warning processing means 4 issues a warning when the direction indicator 5 is operated and the object distance between the object measured by the distance measuring sensors 1 and 2 and the subject vehicle is smaller than the set warning distance. 1 is set in the flag 13. In S105, the alarm unit 11 outputs an alarm only when the alarm flag 13 is set.
[0014]
Next, the lane change detection process will be described in detail. In the following description, as shown in FIG. 3, it is assumed that there are continuous objects such as guard rails 14 on the left and right sides of the road, but the same applies to other stationary road side walls or sound insulation walls. It is. In such a road, when the lane is changed to the right side, the object distance between the object measured by the right distance measuring sensor 1 and the own vehicle becomes shorter, and the object measured by the left distance measuring sensor 2 and the own vehicle are reduced. The phenomenon that the object distance between becomes longer occurs. Conversely, when the lane is changed to the left side, the object distance between the object measured by the right distance measuring sensor 1 and the own vehicle becomes longer, and the distance between the object measured by the left distance measuring sensor 2 and the own vehicle is increased. The object distance is shortened. Therefore, if this characteristic is used, it is possible to detect that the vehicle has actually changed lanes after the direction indicator 5 is released. For example, after operating the direction indicator 5 and blinking the blinker, it can be determined that the lane is not changed when the vehicle is traveling in the lane for several seconds.
[0015]
The lane change detection procedure is S201, and the lane change detection means 6 determines whether or not there is an input from the direction indicator 5. If the operation is in operation, the operation proceeds to S202. If not, the operation proceeds to S213. In S202, the lane change detection means 6 determines whether or not the direction indicator 5 has started to be operated. If it is determined that the direction indicator 5 has started to operate, the process proceeds to S203, where the direction indicator 5 has already been operated. If it is determined that it has been performed, the process proceeds to S204. In S203, the distance storage means 7 stores the object distances Rs (0), Ls (0) between the object measured by the left and right distance measuring sensors 1 and 2 and the host vehicle as reference distances. In S204, the distance difference calculation means 8 obtains data of the object distances Rs (1) and Ls (1) between the own vehicle and the object newly measured by the left and right distance measuring sensors 1 and 2. In S205, the distance difference calculation means 8 calculates the first differences ΔRs (1) and ΔLs (1) between the left and right reference distances Rs (0) and Ls (0), and the distance storage means 7 One difference ΔRs (1), ΔLs (1) is stored. In S206, the distance difference calculation means 8 further obtains data of the object distances Rs (2) and Ls (2) between the own vehicle and the object newly measured by the left and right distance measuring sensors. In S207, the distance difference calculation means 8 calculates the second differences ΔRs (2) and ΔLs (2) between the left and right reference distances Rs (0) and Ls (0), and the distance storage means 7 Two differences ΔRs (2) and ΔLs (2) are stored. In S208, the lane change detection means 6 calculates the left difference difference (ΔLs (2) −ΔLs (1)) and the right difference difference (ΔRs (2) −ΔRs (1)). In S209, the lane change detection means 6 determines whether the left difference difference (ΔLs (2) −ΔLs (1)) has increased and the right difference difference (ΔRs (2) −ΔRs (1)) has decreased. To do. When the determination in S209 is YES, in S210, the lane change detection means 6 determines that the lane has been changed to the right side, and the lane change detection process ends. Otherwise, the process proceeds to S211, and in S211, the lane change detection means 6 decreases the left difference difference (ΔLs (2) −ΔLs (1)) and the right difference difference (ΔRs (2) −ΔRs (1). )) Is increased, and if the result of the determination is YES, the process proceeds to S212, and in S212, the lane change detection means 6 determines that the host vehicle is changing the lane to the left side, and a lane change detection process Ends. When the determination in S211 is No, the process proceeds to S213. In S213, the lane change detection unit 6 determines that the host vehicle has not yet started the lane change, and the lane change detection process ends.
[0016]
Next, the alarm distance setting process will be described. When the lane change detection means 6 determines that the lane change operation is started, the alarm distance setting means 9 sets the first alarm distance R1 (m) as shown in FIG. To do. As time elapses, the alarm distance decreases sequentially from the first alarm distance R1 (m) to the second alarm distance R2 (m) in inverse proportion to the elapsed time, and after the time T1 (s) has elapsed, the alarm distance Is constant for the second alarm distance R2 (m).
[0017]
Next, the alarm determination process will be described. The warning determination means 12 determines whether or not there is a lane change from the lane change detection means 6, and when it is determined that the lane change has started, the warning distance stored in the warning distance storage means 10, in the above example, The value of R1 (m) to R2 (m) is compared with the distance Rs (i) between the object on the right side measured at an interval of several tens of msec and the host vehicle. At that time, when the object distance Rs (i) between the object on the right rear side of the host vehicle and the host vehicle is shorter than the alarm distance, 1 is set in the alarm flag 13. Normally, the warning determination means 12 resets the warning flag to 0 when it is determined that there is no lane change.
[0018]
Thus, by reducing the warning distance from R1 to R2 at the moment when it is determined that the lane has been changed, it is possible to prevent a false alarm due to a guardrail or the like. For example, when it is determined that the lane is changed, it is assumed that the distance to the guard rail is 5 m. If the alarm distance R1 = 3.5 m, the distance to the guardrail is greater than the alarm distance R1 at the beginning of the lane change, so the guardrail is not subject to alarm. According to the lane change operation, the distance to the guardrail becomes shorter, and sooner than R1. Therefore, by reducing the alarm distance from R1 to R2 as in the present invention, no alarm is erroneously issued even if the distance to the guard rail is shortened.
[0019]
Further, when it is determined that the lane change is started only by the operation of the direction indicator and the warning distance is decreased from R1 to R2, the warning distance is decreased even if the lane is not actually changed. When the lane change is actually performed later, an error that the approach of the following vehicle or the like cannot be detected and the warning must be issued occurs. However, since such a post-measurement warning device reduces the warning distance after confirming that the vehicle has actually changed lanes, it is possible to prevent an error that a warning is not issued when a warning should be given.
[0020]
In this way, it is possible to reduce false alarms caused by roadside objects such as guardrails when changing lanes at low cost.
[0021]
Embodiment 2. FIG.
FIG. 6 is a block diagram of a rear side alarm device according to Embodiment 2 of the present invention. FIG. 7 is a flowchart of the lane change detection process of FIG.
FIG. 6 is different from FIG. 1 in that a difference averaging means 15 is added to the lane change detection means 6, and the others are the same as those in FIG. 7, S301 through S303 and S312 through S317 are the same steps as S201 through S203 and S208 through S213 in FIG. 4, respectively. Note that the first difference and the second difference in S208 correspond to the average first difference and the average second difference in S312.
[0022]
The difference averaging means 15 averages the difference between the reference distance obtained by the distance difference calculating means 8 and the object distance between the object measured by the distance measuring means 3 and the host vehicle several times. The difference averaging procedure will be described with reference to FIG. In S304, the distance difference calculation means 8 obtains data of the object distances Rfs (1) and Lfs (1) between the host vehicle and the object newly measured by the left and right distance measuring sensors. In S305, the distance difference calculation means 8 calculates the differences ΔRfs (1) and ΔLfs (1) between the left and right reference distances Rs (0) and Ls (0), and the distance storage means 7 calculates the difference ΔRfs ( 1) and ΔLfs (1) are stored. In step S306, the difference averaging unit 15 determines whether the number of distance measurements is N or more. If the number is less than N, the process returns to step S304, and further performs distance measurement and difference calculation / storage in steps S304 and S305. If the number of distance measurements exceeds N, the process proceeds to S307. In S307, the difference averaging means 15 stores (N-1) differences ΔRfs (1), ΔRfs (2),..., ΔRfs (N-1) and ΔLfs (1) stored in the distance storage means 7. ), ΔLfs (2),..., ΔLfs (N−1) average first differences AVEΔRfs (1) and AVEΔLfs (1) are calculated. In S308, the distance difference calculation means 8 obtains data of the object distances Rss (1) and Lss (1) between the host vehicle and the object newly measured by the left and right distance measuring sensors. In S309, the distance difference calculation unit 8 calculates the differences ΔRss (1) and ΔLss (1) between the left and right reference distances Rs (0) and Ls (0), and the distance storage unit 7 calculates the difference ΔRss ( 1) and ΔLss (1) are stored. In S310, the difference averaging means 15 determines whether the number of distance measurements is M times or more. When the number is less than M times, the difference average unit 15 returns to S308, and further performs distance measurement and difference calculation / storage in S308 and S309. If the number of distance measurements exceeds M, the process proceeds to S311. In S <b> 311, the difference averaging unit 15 determines the difference ΔRss (1), ΔRss (2),..., ΔRss (M) and ΔLss (1), ΔLss (2) for M times stored in the distance storage unit 7. ,..., ΔLss (M) average second differences AVEΔRss (2) and AVEΔLss (2) are calculated. In S312, the distance difference calculation means 8 subtracts the average first differences AVRΔRfs (1) and AVEΔLfs (1) from the left and right average second differences AVRΔRss (1) and AVEΔLss (1), respectively. 2) Calculate -ΔLfs (1) and right difference difference ΔRss (2) -ΔRfs (1).
[0023]
Such a rear side warning device can reduce the influence due to the variation in the distance value from the distance measuring sensor by taking the moving average of the difference, and can improve the reliability of the lane change detection.
[0024]
Embodiment 3 FIG.
FIG. 8 is a block diagram of a rear side alarm device according to Embodiment 3 of the present invention.
FIG. 8 is different from FIG. 1 in that the alarm processing means 4 of FIG. 1 is further provided with an alarm permission flag 16, and the other parts are the same as those in FIG.
[0025]
The warning processing means 4 sets 1 to the warning permission flag 16 when the lane change detection means 6 determines that the lane change is started, and sets 0 to the warning permission flag 16 after a predetermined time has elapsed. On the other hand, the warning determination means 12 determines whether or not there is a lane change from the lane change detection means 6, and when it is determined that the lane change has started to either the right side or the left side, it is stored in the warning distance storage means 10. Alarm distance, in the above example, when the right lane is changed, the value of R1 (m) to R2 (m), and the object distance between the object on the right and the vehicle measured at intervals of several tens of msec Compare with Rs (i). When the object distance Rs (i) between the right object and the host vehicle at that time is shorter than the alarm distance, 1 is set in the alarm flag 13.
The alarm means 11 issues an alarm to the driver only when 1 is set in the alarm flag 13 and the alarm permission flag 16.
[0026]
Since such a rear side warning device restricts the time for warning output to only a certain time after it is determined that the lane change is started, it further reduces false alarms caused by roadside objects such as guardrails at the time of lane change. Can be implemented at low cost.
[0027]
Embodiment 4 FIG.
FIG. 9 is a block diagram of a rear side alarm device according to Embodiment 4 of the present invention. FIG. 10 is a flowchart of the lane change detection process of FIG.
FIG. 9 is different from FIG. 1 in that the lane change detection means 6 is further provided with a lateral movement amount calculation means 17, and the other parts are the same as those in FIG. In FIG. 10, S401 to S413 are the same steps as S201 to S213 in FIG.
[0028]
The horizontal movement amount calculation unit 17 calculates the horizontal movement amount based on the output from the distance difference calculation unit 8. In the lane change detection process, a procedure for calculating a lateral movement amount from a change in distance of a continuous object such as a roadside guardrail will be described.
[0029]
When the lane change detection means 6 determines that the lane has been changed in S410 or S412, the process proceeds to S414. In S414, the lateral movement amount calculation means 17 obtains the lateral velocity V (m / s) from the second difference calculated in S407 and the elapsed time between the first distance measurement time and the third distance measurement time. . Further, the lateral movement amount calculation means 17 measures the elapsed time T (s) between the first distance measurement time and the current time in S414, and calculates the lateral movement amount X ( m) is calculated. When it is determined in S413 that the lane change has not started, in S415, the lateral movement amount calculation means 17 sets the lateral movement amount to 0.
[0030]
Next, the operation of the alarm distance setting means 9 will be described. When the lane change detection means 6 determines that the lane change has occurred, when it is determined that the lane change operation has started as shown in FIG. 11, the first warning distance R1 (m) is set, and the warning distance storage means 10 Remember. In accordance with the change in the lateral movement amount X (m), the warning distance is sequentially decreased from the first warning distance R1 (m) to the second warning distance R2 (m), and the horizontal movement amount X (m) is determined in advance. After reaching the threshold value A (m), the alarm distance is set to be constant at the second alarm distance R2 (m).
[0031]
Such a rear side warning device sets the warning distance according to the amount of movement in the lateral direction, so the warning distance is set in inverse proportion to the amount of movement in the lateral direction of the vehicle, regardless of how the driver operates. For example, when the lane is suddenly changed in the lateral direction, the warning distance is also suddenly reduced, so that an object on the roadside such as a guardrail is not erroneously warned.
[0032]
Embodiment 5 FIG.
FIG. 12 is a configuration diagram of a rear side alarm device according to Embodiment 5 of the present invention. FIG. 13 is a flowchart of the lane change detection process of FIG.
FIG. 12 is the same as FIG. 6 except that the lateral direction movement amount calculation means 17 described in FIG. 9 is added to the lane change detection means 6 of FIG. Since 17 has been described in relation to FIG. In FIG. 13, S501 to S517 are the same steps as S301 to S317 in FIG.
[0033]
If it is determined in S514 or S516 that the lane change detection means 6 has changed the lane, the process proceeds to S518. In S518, the lateral movement amount calculation means 17 calculates the lateral speed V (m / s) from the average second difference calculated in S511 and the elapsed time between the first distance measurement time and the Mth distance measurement time. Ask. Further, the lateral movement amount calculation means 17 measures the elapsed time T (s) between the initial distance measurement time and the current time in S518, and the lateral movement amount X ( m) is calculated. When it is determined in S517 that the lane change has not started yet, in S519, the lateral movement amount calculation means 17 sets the lateral movement amount to zero.
[0034]
Such a rear side warning device can reduce the influence due to the variation in the output of the distance measuring sensor by taking the average of the lateral movement amount, and can improve the reliability of the lane change detection.
[0035]
Embodiment 6 FIG.
FIG. 14 is a block diagram of a rear side alarm device according to Embodiment 6 of the present invention.
FIG. 14 is the same as FIG. 8 except that the lateral movement amount calculating means 17 described in FIG. 9 is added to the lane change detecting means 6 of FIG. 8, and the other is the same as FIG. Since 17 has been described in relation to FIG.
[0036]
Since such a rear side warning device restricts the time for warning output to only a certain time after it is determined that the lane change is started, it further reduces false alarms caused by roadside objects such as guardrails at the time of lane change. Can be implemented at low cost.
[0037]
【The invention's effect】
The effect of the rear side warning device of the present invention is that the distance measuring means for measuring the object distance between the own vehicle and the object existing on the rear side, the lane change detecting means for detecting the lane change of the own vehicle, An alarm distance setting means for setting an alarm distance from the own vehicle, and an alarm processing means for comparing the alarm distance with the object distance on the side where the lane is changed, and determining that an alarm is generated when the object distance is smaller than the alarm distance, The warning distance setting means sets the warning distance as a first warning distance that is predetermined in synchronization with the detection of the lane change, and reaches a predetermined second warning distance in inverse proportion to the elapsed time from the detection of the lane change. Since it is set so that it decreases and becomes constant at the second warning distance, it is possible to reduce false alarms caused by roadside objects such as guardrails when changing lanes.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a rear side alarm device according to Embodiment 1 of the present invention;
FIG. 2 is a flowchart of alarm processing in FIG. 1;
FIG. 3 is a situation diagram in which a vehicle changes lanes.
4 shows a flowchart of the lane change detection process of FIG.
FIG. 5 is a diagram showing the relationship between the warning distance and the time from the start of lane change adopted in the embodiment.
FIG. 6 is a configuration diagram of a rear side alarm device according to Embodiment 2 of the present invention.
7 is a flowchart of the lane change detection process of FIG.
FIG. 8 is a configuration diagram of a rear side alarm device according to Embodiment 3 of the present invention.
FIG. 9 is a flowchart of the alarm process of FIG.
FIG. 10 is a configuration diagram of a rear side alarm device according to Embodiment 4 of the present invention.
11 is a flowchart of the lane change detection process of FIG.
FIG. 12 is a configuration diagram of a rear side alarm device according to Embodiment 5 of the present invention;
13 is a flowchart of the lane change detection process of FIG.
FIG. 14 is a configuration diagram of a rear side alarm device according to Embodiment 6 of the present invention;
[Explanation of symbols]
1 right distance sensor, 2 left distance sensor, 3 distance measurement means, 4 alarm processing means, 5 direction indicator, 6 lane change detection means, 7 distance storage means, 8 distance difference calculation means, 9 alarm distance setting means, DESCRIPTION OF SYMBOLS 10 Alarm distance memory | storage means, 11 Alarm means, 12 Alarm determination means, 13 Alarm flag, 14 Guard rail, 15 Difference average means, 16 Alarm permission flag, 17 Lateral movement amount calculation means

Claims (5)

A distance measuring means for measuring an object distance between the host vehicle and an object existing on the rear side;
Lane change detection means for detecting a lane change of the host vehicle;
An alarm distance setting means for setting an alarm distance from the host vehicle;
Comparing the alarm distance with the object distance on the lane change side, and comprising alarm processing means for determining that an alarm is generated when the object distance is smaller than the alarm distance,
The alarm distance setting means is
The warning distance is set to a first warning distance determined in advance in synchronization with the detection of the lane change, and is reduced to a predetermined second warning distance in inverse proportion to the elapsed time from the detection of the lane change. A rear side warning device that is set to be constant at the second warning distance. A distance measuring means for measuring an object distance between the host vehicle and an object existing on the rear side;
Lane change detection means for detecting a lane change of the host vehicle;
An alarm distance setting means for setting an alarm distance from the host vehicle;
Lateral movement amount calculating means for calculating the lateral movement amount of the host vehicle using the object distance obtained from the distance measuring means;
Comparing the alarm distance with the object distance on the lane change side, and comprising alarm processing means for determining that an alarm is generated when the object distance is smaller than the alarm distance,
The alarm distance setting means is
The warning distance is set as a first warning distance that is determined in advance in synchronization with the detection of the lane change, up to a second warning distance that is determined in inverse proportion to the lateral movement amount from the detection of the lane change. A rear side warning device, which is set so as to decrease and become constant at the second warning distance. The distance measuring means includes left and right distance measuring means,
The lane change detection means is
Synchronizing with the operation of the direction indicator, distance storage means for storing the distance between the vehicle measured by the left and right distance measuring means and the object existing on the rear side as a reference distance;
Distance difference calculating means for calculating a difference between the stored reference distance and the object distance measured by the distance measuring means for the right side and the left side of the own vehicle,
For the right side and the left side, the first difference is calculated after several tens of msec from the operation of the direction indicator, and the second difference is calculated after the predetermined tens of msec , and the second of the right side is calculated. Is smaller than the first difference and the second difference on the left side is greater than the first difference, it is determined that the host vehicle is changing the lane to the right side, and the second difference on the right side is determined. The vehicle is determined to have changed its lane to the left when the vehicle is larger than the first difference and the second difference on the left side is smaller than the first difference. Rear side alarm device described in. The distance measuring means includes left and right distance measuring means,
The lane change detection means is
Synchronizing with the operation of the direction indicator, distance storage means for storing the distance between the vehicle measured by the left and right distance measuring means and the object existing on the rear side as a reference distance;
Distance difference calculating means for calculating a difference between the stored reference distance and the object distance measured by the distance measuring means for the right side and the left side of the own vehicle;
Difference average means for obtaining an average of differences calculated by the distance difference calculation means for a predetermined number of times,
Calculate the left and right side differences for multiple times, average them for each of the left and right sides to obtain the first average difference, and then calculate the left and right side differences for multiple times and then calculate them for the left and right sides respectively. When the second average difference on the right side is smaller than the first average difference and the second average difference on the left side is larger than the first average difference, The host vehicle determines that the lane is changed to the right side, the second average difference on the right side is larger than the first average difference, and the second average difference on the left side is smaller than the first average difference. The rear side warning device according to claim 1, wherein the vehicle determines that the lane is changed to the left side. The alarm processing means is
The alarm distance is compared with the object distance on the lane change side only until a predetermined time elapses after the start of lane change, and it is determined that an alarm is generated when the object distance is smaller than the alarm distance. The rear side warning device according to any one of claims 1 to 4, wherein the rear side warning device is provided.

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