JP3334326B2 - Stopper distance alarm - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention provides an alarm when the distance between a host vehicle and a stationary object detected in front of the host vehicle for a predetermined time is within an alarm distance set based on the running state of the host vehicle. The present invention relates to a stationary object distance alarm device for executing an operation to prevent an accident.

[0002]

2. Description of the Related Art Conventionally, as a device for warning when the distance between a vehicle and an object in front is in a dangerous range, Japanese Patent Laid-Open Publication No. Hei 5-
No. 166097 and JP-A-4-201643. The former (Japanese Patent Application Laid-Open No. H5-166097) is a device that issues an alarm when the distance between the own vehicle and a preceding vehicle traveling ahead is in a dangerous range, and detects only a simple inter-vehicle distance before that to issue an alarm. This is an improvement of the device. However, this warning device does not consider a stationary object such as a roadside body. Therefore, particularly when a roadside body is detected at a curve or the like, a warning is frequently issued, which may distract the driver's attention.

In order to prevent such false alarms,
In the latter (Japanese Patent Laid-Open No. 4-201643), the warning judging area of the beam on the roadside body is shortened so that the roadside body is not warned as much as possible in a curve.

[0004]

However, in the latter device, since three laser beams are used, the structure is complicated and the cost is increased. In particular, when the vehicle is traveling at a high speed, the warning determination area extends to a long distance in proportion to the vehicle speed in consideration of the idling distance and the braking distance. In the detection of an object at a long distance, the beam is scattered, so that an object in a wide range is easily detected. On the other hand, the detection accuracy is reduced, and it is difficult to determine the position accurately. For this reason, if approaching, even a roadside body that is known to be in danger of collision may frequently give a false alarm as a danger of collision.
Therefore, there is no difference from the former device in the problem of false alarm. If such a situation that does not require an alarm is detected and the alarm is issued frequently, the alarm will be extremely unpleasant for the driver, distracting and possibly turning off the alarm device. . In this case, there is no point in providing an alarm device.

SUMMARY OF THE INVENTION The present invention provides a stop object distance alarm device that can identify a stop object such as a roadside body that does not hinder running and, as a result, sufficiently fulfill the role of an alarm device or the like. .

[0006]

According to the first aspect of the present invention,
A stationary object distance alarm device that executes an alarm process when the distance between the own vehicle and a stationary object detected for a predetermined time in front of the own vehicle is within an alarm distance set based on the traveling state of the own vehicle. there, the warning distance, while being set so as to increase substantially in proportion to the vehicle speed of the vehicle, is set loose gradient of increase than low speed range in the high speed range, further, the predetermined
The time is set shorter as the vehicle speed increases,
A stationary object distance alarm device, which is set longer when the vehicle speed decreases .

According to a second aspect of the present invention, there is provided the stationary object distance warning device according to the first aspect, wherein a boundary between the low speed area and the high speed area is 40 to 70 km / h. The invention according to claim 3 is the stationary object distance alarm device according to claim 1 or 2, wherein the increasing gradient of the warning distance with the vehicle speed in the high speed region is approximately 1/5 of that in the low speed region.

According to a fourth aspect of the present invention, the increasing gradient of the warning distance with the vehicle speed in the high speed region is zero.
It is a stop thing distance alarm device of the statement. According to a fifth aspect of the present invention, there is provided the stationary object distance alarm device according to any one of the first to fourth aspects, wherein the warning distance in the low-speed region is set by the sum of the idle distance and the braking distance.

[0009]

[0010]

[0011]

The stop object distance alarm device according to the first aspect executes an alarm process when the detected stop object is within the alarm distance. This warning distance is to warn a collision with a stationary object, and when the time for avoiding the collision is converted into the distance, naturally, the faster the vehicle speed, the higher the vehicle speed.
Since the idling distance and braking distance become longer, the distance must be set longer in proportion to the vehicle speed. Therefore, when the vehicle is traveling at a high speed, the warning distance is set to be long, and even a stationary object located far ahead is within the warning distance.

However, as the length becomes longer, objects farther from the traveling area such as a roadside body are more likely to be detected as stationary objects ahead.
The detection accuracy decreases. This is because the detection device usually uses electromagnetic waves and sound waves, so the longer it is, the more it diffuses,
It is inevitable. For this reason, in the present invention, an increase in the warning distance is suppressed in a region where the warning distance is long in the high-speed region. That is, the increasing gradient of the warning distance is made gentler in the high-speed area than in the low-speed area. As a result, it is possible to prevent the detection of a stationary object having no problem in traveling such as a roadside body as much as possible, thereby preventing distraction of the driver and switching off the alarm device. Moreover, since the processing can be performed with one fixed beam, it is sufficient to change only the processing with the conventional configuration without increasing the cost. Also, detection of stationary objects
If the vehicle speed is low, there is enough time to approach
Since there is sufficient time, the above-mentioned predetermined time is extended, and the vehicle speed of the own vehicle is high.
If it is fast, there is no time to approach, so shorten the above specified time.
Make More specifically, for example, as shown in FIG.
Preferably.

According to a second aspect of the present invention, in the first aspect, the boundary between the low-speed region and the high-speed region is set to 40 to 40.
70 km / h. By setting the boundary of this range, in addition to the operation and effect of the first aspect, it is possible to further suppress erroneous alarms caused by the roadside body or the like particularly in high-speed traveling where the roadside body or the like is easily detected. In particular, it is preferable to set the above boundary at 50 to 60 km / h in order to further suppress false alarms.

According to a third aspect of the present invention, in the stationary object distance warning device according to the first or second aspect, the increasing gradient of the warning distance according to the vehicle speed in the high speed region is set to approximately 1/5 of that in the low speed region. In addition to the operation and effect of the first or second aspect, with this ratio, the effect of suppressing false alarms by the roadside body and the like is further increased.

According to a fourth aspect of the present invention, there is provided a stationary object distance warning device according to the first or second aspect, wherein the increasing gradient of the warning distance with the vehicle speed in a high-speed region is set to zero. As described above, even when the warning distance is completely constant in the high-speed region, the effect of suppressing false alarms by the roadside body or the like can be improved as in the first or second aspect.

According to a fifth aspect of the present invention, there is provided a stationary object distance warning device according to any one of the first to fourth aspects, wherein the warning distance in the low speed region is set by a sum of an idle running distance and a braking distance. With such a setting, in addition to the effects of any one of the first to fourth aspects, in a low-speed range, the driver can stop immediately before the alerted stop object.

[0017]

Here, the idling distance means a driving distance (for example, 1.5 seconds which is a human reaction time) from when a driver tries to apply a brake to when the brake actually starts to work.
The braking distance is a running distance from when the brake is applied to when it stops, and is substantially proportional to the speed. The avoidance distance is an idle running distance that can be avoided by steering operation (for example, 2 seconds), and the allowance distance is provided to smoothly connect to the low-speed warning distance.

[0019]

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a vehicle obstacle warning device according to an embodiment of the present invention will be described. This obstacle alarm device 1
This device is mounted on an automobile, detects an object in front of the automobile, and outputs an alarm to notify the driver when an obstacle exists in an area to be alarmed.

FIG. 1 is a system block diagram of the system.
The obstacle alarm device 1 is mainly configured with a controller 3. The controller 3 mainly includes a microcomputer and includes an input / output interface (I / O) and various drive circuits and detection circuits. Since these hardware configurations are general, detailed description will be omitted.

The controller 3 includes a fixed beam ranging device 5, a vehicle speed sensor 7, a brake switch 9, and a throttle opening sensor 1.
1, predetermined detection data is input. Further, the controller 3 outputs a predetermined drive signal to the alarm sound generator 13, the distance display 15, the sensor abnormality display 17, the brake driver 19, the throttle driver 21, and the automatic transmission controller 23.

The controller 3 further includes an alarm sensitivity setting unit 25 and an alarm volume setting unit 27, and reflects the settings in the alarm volume and processing described later. The controller 3 includes a power switch 29, and starts a predetermined process when the power switch 29 is turned “ON”. Here, the fixed beam distance measuring device 5 is
1 and a distance calculation unit 33. The transmission / reception unit 31 outputs laser light to the front of the vehicle to detect the reflected light, and based on the time until the distance calculation unit 33 captures the reflected light, an object in front of the vehicle is detected. It is a device that detects the distance up to. Since such a device is already well known, a detailed description is omitted. In addition to the laser beam, a radio wave such as a microwave or an ultrasonic wave may be used.

With this configuration, the controller 3 has a function of issuing an alarm when an obstacle is present in a predetermined alarm area described later for a predetermined time. The obstacle includes a preceding vehicle traveling in front of the own vehicle, a preceding vehicle that is stopped, or an object (a guardrail, a support, or the like) on the roadside.

Further, the brake driver 19, the throttle driver 21, and the automatic transmission controller 23 in FIG. 1 may not be provided, but in the present embodiment, these are provided and the vehicle speed is adjusted according to the situation of the preceding vehicle. Control, so-called cruise control, is also performed at the same time. FIG. 2 shows a control block diagram of the controller 3. The data of the distance L output from the distance calculation unit 33 of the fixed beam distance measuring device 5 is
According to 3, if the value of this data indicates an abnormal range, an indication to that effect is displayed on the sensor abnormality display 17.

The data of the distance L enters the object recognition block 45, and the type of recognition and the position of the object are obtained. The recognition type is for recognizing whether the object is a stationary object or a moving object. In addition, an object that affects traveling is selected by the distance display object selection block 47 based on the position of the object, and the distance is displayed by the distance display 15.

The vehicle speed (own vehicle speed) V output from the vehicle speed calculation block 49 based on the value detected by the vehicle speed sensor 7.
The relative speed calculation block 51 calculates the relative speed Vr of an obstacle such as a preceding vehicle based on the own vehicle position based on the position of the object. Further, based on the vehicle speed and the position of the object, the acceleration of the front vehicle is calculated based on the own vehicle position in the front vehicle acceleration calculation block 53.

Then, the alarm judgment and cruise judgment block 55 performs the own vehicle speed, the front vehicle relative speed, the front vehicle acceleration, the object position, the recognition type, the output of the brake switch 9, the opening from the throttle opening sensor 11 and the alarm. Sensitivity setting device 2
Based on the sensitivity set value by 5, it is determined whether or not an alarm is to be issued if the determination is an alarm, and the content of the vehicle speed control is determined if the determination is a cruise. The result is output to the alarm sound generator 13 via the volume control block 57 if an alarm is required.
Output to The sound volume adjustment block 57 controls the output sound volume of the alarm sound generator 13 based on the set value of the alarm sound volume setting device 27. If the cruise is determined, the automatic transmission controller 23, the brake driver 19, and the throttle driver 2
1 to output a control signal to perform necessary control.

Next, a description will be given of the alarm determination and cruise determination block 55 with reference to flowcharts, focusing on the alarm determination and warning. Since the cruise determination is not directly related to the present invention, the description is omitted. FIG. 3 shows a flowchart of the alarm process. This process is the power switch 2
This is a process that is repeatedly performed when 9 is turned on. First, object recognition is performed and the result is determined (step 1000. The steps are also simply referred to as S hereinafter). In this object recognition, the forward moving state is determined based on the distance measured by the fixed beam distance measuring device 5 and the vehicle speed detected by the vehicle speed sensor 7 to determine whether the moving object is a stationary object or a moving object. The object recognizing block 45 determines whether or not this is the case. Then, based on the result, if the object is a stationary object, the process proceeds to a stationary object alarm process (S2000), and if the object is a moving object, the process proceeds to a moving object alarm process (S3000). The moving object warning process warns the driver when there is a risk of a collision of the preceding vehicle based on the inter-vehicle distance between the preceding vehicle and the own vehicle, the braking force, the moving speed and acceleration of the own vehicle and the preceding vehicle, for example. Processing
The moving object warning process is a known process and is not directly related to the present invention, so that detailed description is omitted.

The stop object warning process (S2000) will be described with reference to the flowchart of FIG. First, a stop object alarm calculation (S2100) is performed. The stationary object alarm calculation is a process for obtaining a stationary object detection duration time and an approach distance. The detection continuation time is a time during which the stationary object continues to be detected by the fixed beam distance measuring device 5 and recognized by the object recognition block 45 as a stationary object. The approach distance is the distance between the stationary object and the host vehicle.

The detection continuation time and approach distance are stored in the memory in the alarm determination and cruise determination block 55 for each stationary object, and are calculated and updated for each detection cycle. This value is read out and used as the detection duration time and approach distance. Next, a collision determination (S2200) is made.
It is determined whether or not both the detection duration and the approach distance of each stationary object obtained in step 2100 are within a range in which a collision is likely (a range to be warned). This range is as shown in the graph of FIG. FIG. 5 (a)
It is a graph showing the area | region of the presence or absence of an alarm of the detection continuation time set according to the vehicle speed of the own vehicle. FIG. 5B is a graph showing an area indicating whether or not an approach distance warning is set according to the vehicle speed of the own vehicle.

FIG. 5A is a graph showing a boundary line indicating a tendency to decrease as the vehicle speed increases as a whole. Specifically, when the vehicle speed is equal to or less than the vehicle speed S1 (for example, 40 km / h), the time T2 is constant, and the vehicle speeds S1 to S4 (for example, 8
0 km / h) until the time T1 with a constant gradient,
At the vehicle speed S4 or higher, there is shown a boundary line that is a fixed time T1.

Above this boundary line, it indicates that a stationary object has been detected for a long time, and it is considered that there is a stationary object in the traveling direction of the vehicle. Since the detection is performed for a short time, the area below the area is a "stop without warning" area.

In FIG. 5B, the vehicle speed S2 (for example, 7
0 km / h), that is, a line having a constant gradient θ1 in a low speed region, and a line having a constant gradient θ2 in a high speed region or higher, ie, a line having a constant gradient θ2 (corresponding to a warning distance).
It is shown. Here, the gradient θ1> θ2. The gradients θ1 and θ2 are set based on the sum of the idle running distance and the braking distance for the gradient θ1. For the gradient θ2,
It may be 1/5 of the gradient θ1 or θ2 = 0. Further, by adding a margin time based on the avoidance distance by the steering operation, it may be set so as to be smoothly connected to the boundary line of the low speed region. The gradient θ1 is
Set by the sum of the idling distance and braking distance, the slope θ2,
FIG. 6 shows an example of setting by adding a margin time based on the avoidance distance by the steering operation.

Above this boundary line, it is a distance that can be avoided by operating the brake or steering, so it is an area of "stop without warning". Below the boundary line, it cannot be avoided by brake or steering. Stop area to be stopped ".

Therefore, based on the detection duration and approach distance obtained in step 2100, and the current vehicle speed, it is determined which area is located in the determination maps of FIGS. 5 (a) and 5 (b). . If both are determined to be "stopped objects to warn", it is determined that a collision has occurred, and false alarm measure 1 is implemented (S2400). If it is determined that one or both of them are "stops that do not warn", false alarm countermeasure 2 is performed (S2600).

The false alarm measure 1 is shown in the flowchart of FIG. This processing is performed to reduce false alarms by limiting the alarm operating conditions.
10 to S2440, an alarm is established (S
2450), alarm suspension (S2460), determination suspension (S2
470).

The alarm is established (S2450) at S2.
At 410, it is determined that the object is a stationary object approaching, at S2420 it is determined that the vehicle speed is equal to or higher than the alarm permitting vehicle speed, at S2430 it is determined that braking is not being performed, and at S2440 they continue for a certain period of time or longer. Only in cases. Also, the determination up to S2430 is the same, but if it is determined in S2440 that it does not continue for a certain period of time, the alarm is suspended in S2460. In other cases, the determination in S2470 is suspended.

The meaning of these determinations will be described. If it is determined in S2410 that the vehicle does not approach, it means that the distance from the own vehicle does not change or the vehicle goes away. Judgment is suspended. The alarm permission speed in S2420 is, for example, 20K.
About m / h is conceivable. For example, in a parking lot, the direction is frequently changed, so that if no guard is applied, other vehicles, walls, and pillars that are parked will be warned. Therefore, in order to avoid those false alarms, for example, 20 km
At low speeds equal to or lower than / h, the determination is suspended and no alarm is issued. In addition, once it becomes 20 km / h, it is preferable to give an alarm until it becomes less than 15 km / h.

In S2430, it is considered that the driver is trying to decelerate while the brake is being depressed, so that no alarm is issued in this case. The fixed time in the determination in S2440 is set to a relatively short time, for example, 0.3 seconds. This is to prevent a false alarm due to noise or the like. In a state where a true alarm is required, for example, it continues for 0.3 seconds or more, so that a false determination due to noise can be suitably avoided.
There is no mistake in making decisions when necessary.

FIG. 8 is a flowchart showing the second measure against false alarm. This process is performed when it is determined in S2200 that no collision occurs, as shown in FIG. 4, and when the determination is suspended in S2400, and as shown in FIG.
Then, the continuation state is determined, and the alarm is not established only when the continuation is continued for a predetermined time (S2620), and otherwise, the alarm is held (S2630). In other words, even if it is not necessary to issue an alarm, the alarm is not stopped for a moment, and the alarm is stopped only when the condition that does not need to be issued continues for a certain period of time. It is.

An actual operation state of the first embodiment having the above-described structure will be described. As shown in the schematic diagram of FIG. 9A, when the vehicle C is traveling on a curve of an expressway, if the detection area Ar of the fixed beam distance measuring device 5 is in the range as shown, the fixed beam The range finder 5 is located on the left roadside body L0, L
In the object recognition block 45, the speed at which the object (roadside body L0, L1, L2, L3) approaches the own vehicle is equal to the speed of the own vehicle. Judge. Therefore, in step 1000 of FIG. 3, it is determined that the object is a stationary object, and a stationary object alarm process (S2000) is performed.

In the stationary object alarm processing, the roadside bodies L0, L1, L
2. The distance between the time when L3 and L3 are detected by the fixed beam distance measuring device 5 and the vehicle C is checked. For example, FIG.
As shown in (b), at time t0, the roadside body L0 is detected by the fixed beam distance measuring device 5 at a distance d0 from the own vehicle, is recognized as a stationary object, and is continuously detected until time t1. I do.

In this case, the detection duration is from 0 to M0.
It extends sequentially to (t1-t0). At the same time, the approach distance also decreases from d0 to d2, and the roadside body L0 approaches the own vehicle C. Step 200 is performed several times during this time t0 to t1.
0, the vehicle speed and time (detection continuation time) at that time are included in any area shown in FIG. 5A, and the vehicle speed and distance (approaching distance) at that time are shown in FIG.
It is determined which of the areas shown in (b) is included. As a matter of course, the detection duration gradually increases, and the approach distance gradually decreases. Therefore, it is initially determined that the vehicle is a "stop without warning", but gradually approaches the boundary line.
However, if the duration M0 does not fall within the region above the boundary line in FIG.
If it does not enter the area below the boundary line of (b), every time the processing of step 2000 is executed, step 2
200, it is determined that no collision occurs, and countermeasure for false alarm 2 (S260
0) is executed, and if it is determined that no collision occurs for a predetermined time, an alarm stop process is performed in step 2700, and no alarm is issued.

The same applies to the roadside bodies L1 to L3 in which the appearing distance d1 and the closest approach distance d2 are almost the same. The final detection duration time (M1, M2, M3) and the approach distance (d1− If both d2) do not enter the area of "alarming stop object" in FIGS. 5A and 5B, no alarm is issued. Note that, for example, a stationary object that is easily detected from a long distance, such as a roadside body L0 at the beginning of a curve, has a longer detection duration than the roadside bodies L1 to L3 at other positions of the curve. The distance detected and recognized first starts from the longest distance d0.

Here, as shown in FIG. 5B, the gradient of the approaching distance decreases from the vehicle speed S2. In other words, even if the vehicle speed increases, the area of the "alarm stopped object" does not spread very far. At a long distance, the fixed beam spreads to easily detect an object, while the detection accuracy is reduced, so that a false alarm is likely to occur. Therefore, for such a long distance, the rise of the boundary line with respect to the vehicle speed is suppressed, instead of the slope as in the low speed region, and frequent occurrence of false alarms is prevented. At this long distance, it is sufficient to avoid a stationary object by steering. Therefore, there is no problem even if the gradient of the boundary line is reduced in a region where the vehicle speed is high (for example, 80 km / h) as shown in FIG. Actually, an example in which a boundary line is set for avoidance by braking in a low-speed area and for avoidance by steering in a high-speed area is as shown in FIG.

FIG. 10 shows a measurement result in which false alarms are drastically reduced by such a setting. FIG. 10 is a distribution explanatory diagram in which the distribution of the detected closest approach distance of the roadside body and the detection continuation time is plotted on a plane of distance and time when the vehicle travels on the highway at about 80 km / h. As is clear from FIG. 10, the "warning area" (approaching distance = 62 m or less and detection duration time = 1.5 seconds or more) includes only 4% of the entire roadside body, and all others are "not warn". Territory ". Conventionally, at 80 km / h, the stop object warning distance is 8
Since the distance exceeds 0 m, the area X becomes the "warning area" as shown by the dashed line in FIG. 10, and a false alarm is issued by nearly 20% of the roadside bodies, and does not make sense as an alarm device. At other speeds in the high speed region, almost no warning is issued to the roadside body. Of course,
Even in the low-speed area, almost no warning is issued to the roadside body.

Therefore, according to the present embodiment, it is possible to prevent a warning about a stationary object such as a roadside body having no problem in traveling as much as possible. For this reason, distraction of the driver's attention and switching off of the alarm device can be prevented. In addition, even if the configuration of the conventional one fixed beam is used, only the processing needs to be changed, and the cost does not increase.

[Brief description of the drawings]

FIG. 1 is a system block diagram of an obstacle alarm device according to one embodiment.

FIG. 2 is a control block diagram of the controller.

FIG. 3 is a flowchart of the alarm process.

FIG. 4 is a flowchart of the stop object alarm process.

FIGS. 5A and 5B are map diagrams for collision determination, wherein FIG. 5A shows an area of presence or absence of an alarm of a detection continuation time set according to the vehicle speed of the own vehicle, and FIG. 5B shows a map according to the vehicle speed of the own vehicle; Indicates the area of the set approaching distance with or without the alarm.

FIG. 6 shows an example in which the gradient in the low-speed region in FIG. 5 is set by the sum of the idling distance and the braking distance, and the gradient in the high-speed region is set by adding a margin time based on the avoidance distance by the steering operation. FIG.

FIG. 7 is a flowchart of a false alarm measure 1;

FIG. 8 is a flowchart of a false alarm measure 2;

9A and 9B are explanatory diagrams showing a relationship between an actual traveling state and a detected value, wherein FIG. 9A is a graph showing a traveling state, and FIG. 9B is a graph showing a detected state of a detected value of a stationary object.

FIG. 10 is a graph showing the effect of the embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Obstacle alarm device 3 ... Controller 5 ... Fixed beam distance measuring device 7 ... Vehicle speed sensor 9 ... Brake switch 11 ... Throttle opening degree sensor 13 ... Alarm sound generator 45 ... Object recognition block 49 ... Vehicle speed calculation block 51 ... Relative Speed calculation block 55 ... Alarm judgment and cruise judgment block

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FIG08G1 / 16 G08G1 / 16C (56) References JP-A-5-270335 (JP, A) JP-A-4-201643 ( JP, A) JP-A-4-245600 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60R 21/00 G01S 13/93 G08G 1/16

Claims (5)

(57) [Claims] 1. A stop for executing an alarm process when a distance between a host vehicle and a stationary object detected ahead of the host vehicle for a predetermined time is within an alarm distance set based on a running state of the host vehicle. An object distance warning device, wherein the warning distance increases almost in proportion to the vehicle speed of the own vehicle .
In addition, the gradient of the increase is set to be gentler in the high-speed region than in the low-speed region , and the predetermined time is set to be shorter when the own vehicle speed increases.
A stationary object distance alarm device, which is set longer when the vehicle speed of the own vehicle decreases . 2. The boundary between a low-speed region and a high-speed region is 40-70.
The stop object distance alarm device according to claim 1, wherein the distance is km / h. 3. The stop object distance alarm device according to claim 1, wherein the increasing gradient of the alarm distance with the vehicle speed in the high speed region is approximately 1/5 of that in the low speed region. 4. The stop object distance alarm device according to claim 1, wherein an increasing gradient of the alarm distance according to the vehicle speed in the high speed region is zero. Alarm distance wherein the low-speed region, empty run distance between any one of claims 1 to 4, which is set by the sum of the braking distance
Stationary object distance warning system according to.