FR3101044A1 - Driving assistance method with determination of a multi-target safety distance. - Google Patents

Abstract

Method and system for assisting the driving of a motor vehicle. The invention relates to a method for assisting the driving of an ego motor vehicle (ego) comprising - a step of detecting at least two target vehicles (C1, C2) preceding the ego vehicle (ego) - a step d 'evaluation of at least one distance value (d2) characterizing the position of the second target vehicle (C2) - a step of determining a setpoint safety distance value between the ego vehicle (ego) and the first target vehicle (C1) preceding it, characterized in that said setpoint safety distance value is a function of said distance value (d2) characterizing the position of the second target vehicle (C2). Figure for the abstract: Fig. 1

Description

Driving assistance method with determination of a multi-target safety distance.

The present invention generally relates to methods for assisting the driving of motor vehicles.

It relates more particularly to a method for assisting the driving of an ego motor vehicle comprising:
- a step of detecting at least two target vehicles preceding the ego vehicle
- a step of evaluating at least one distance value characterizing the position of the second target vehicle
- a step of determining a set safety distance value between the ego vehicle and the first target vehicle preceding it, said set safety distance value being a function of the value of the distance characterizing the position of the second target vehicle .

It also relates to a computer program product whose instructions are capable of implementing such a method.

It also relates to a system for assisting the driving of an ego motor vehicle comprising:
- a means of detecting at least two target vehicles preceding the ego vehicle
- means for evaluating at least one distance value characterizing the position of the second target vehicle
- A computer capable of implementing such a method.

It also relates to a motor vehicle comprising a powertrain, braking means and such an aid system.

It is well known to equip a motor vehicle with an adaptive cruise control system, we speak in particular of the ACC system, from the English "Adaptive Cruise Control".

Such an adaptive cruise control system comprises a means of detecting the environment of the vehicle such as a radar and can therefore detect other vehicles or objects on the roadway, in particular it can detect a vehicle which precedes it on the pavement.

These systems are for example designed to steer the vehicle so that its speed is equal to a setpoint given by the driver, except in the presence of an event on the road requiring the vehicle to be slowed down (followed by a vehicle which has a speed different from the instruction given by the driver, traffic jam, traffic light, etc.), in which case the speed of the vehicle is controlled accordingly.

Then, the speed of the vehicle equipped with such an adaptive speed regulation system can be adjusted to maintain a substantially constant safety distance with the vehicle in front. Thus, such a system interacts with an engine control system and/or with a braking system in order to accelerate or decelerate the vehicle.

As the adaptive cruise control system can autonomously control the speed of the vehicle, consideration of the vehicle's environment is necessary, in particular to determine the necessary safety distance.

We know from the state of the art the document US6856887B2 which describes such an adaptive speed regulation system with management of the distance between two vehicles. However, the calculated safety distance may vary suddenly depending on the behavior of the vehicle in front. Such a system therefore does not allow certain braking of the vehicle in front to be anticipated, resulting in excessive braking which can make driving uncomfortable.

Document US9783196B2 is also known, which discloses a multi-target detection and a measurement of the distance between two targets preceding the ego vehicle, this distance measurement between the two target vehicles serving as redundancy to robustify the relative positioning of the ego vehicle with respect to the vehicle preceding it and which constitutes the first target. However, the safety distance remains determined in relation to the first target vehicle alone and does not make it possible either to anticipate the braking operations upstream of the first target vehicle and thus to make the piloting carried out by the ego vehicle during regulation more flexible.

Indeed, the enslavement on the first target vehicle, whether human or robotic, is not always of good quality. Moreover, having at least two regulators in cascade induces a delay: accumulation of the reaction delay of the regulator of the first target compared to the second target and the reaction delay of the ego regulator compared to the first target. This delay can lead to instabilities or “accordion effects”. We can have a bad comfort because of excessive braking and there is a risk of collision if the phase shift reaches 180 degrees.

The object of the invention is to provide a method for assisting the driving of an ego motor vehicle with determination of a safety distance using multi-target detection, remedying the above drawbacks and improving the methods for assisting with driving a motor vehicle ego with determination of safety distance known from the prior art.

To this end, the first object of the invention is a method for assisting the driving of an ego motor vehicle comprising
- a step of detecting a first target vehicle preceding the ego vehicle and at least one other target vehicle preceding the first target vehicle
- a step of evaluating at least one distance value characterizing the position of said at least one other target vehicle preceding the first target vehicle
- a step of determining a set safety distance value between the ego vehicle and said first target vehicle,
said setpoint safety distance value being a function of said distance value characterizing the position of said at least one other target vehicle preceding the first target vehicle.

Thanks to the invention, the safety distance is determined according to the distance between the at least two vehicles preceding the ego vehicle, which makes it possible to take into account the behavior of the vehicles upstream and thus to be able to anticipate related braking, for example to a rapprochement between vehicles upstream, during concertina traffic for example.

According to particular embodiments, said at least one distance value characterizing the position of said at least one other target vehicle preceding the first target vehicle is an inter-target vehicle distance, which allows a simplification of the calculations, while constituting a distance easily deduced from the measurements.

According to another advantageous characteristic, the step of determining a set safety distance value comprises a sub-step of developing a first set safety distance which is a function of the traffic, which makes it possible to adapt to actual conditions.

Advantageously, the sub-step of developing a first set safety distance comprises a first sub-step of determining the dynamics of the distance characterizing the position of said at least one other vehicle preceding the first target vehicle, a second sub-step - step of calculating a statistical value representative of a target inter-vehicle distance, a third sub-step of consolidating a value of the stabilized target inter-vehicle distance and a fourth sub-step of consolidating the first distance safety function depending on the traffic, which makes it possible to avoid sudden variations in the setpoint.

Advantageously; the first sub-step of determining the dynamics of the distance characterizing the position of said at least one other vehicle preceding the first target vehicle consumes a temporal evolution of the inter-target vehicle distance value and assigns at output a boolean to a si in a time sliding window of a predetermined duration said inter-target vehicle distance remains in a hysteresis zone defined by a predetermined tolerance, which makes it possible to evaluate the fluidity of the traffic.

Advantageously, the sub-step of developing a first set safety distance comprises a second sub-step of developing a second set safety distance based on the first set safety distance and the distance characterizing the position of said at least one other target vehicle preceding the first target vehicle, which makes it possible to take into consideration the distances between target vehicles to anticipate their actions and compensate for the potential insufficient safety distances between these vehicles preceding the ego vehicle.

Advantageously, the step of determining a set safety distance value comprises a third sub-step of consolidating the set safety distance value, which makes it possible in particular to cover, without creating a conflict, the cases where a single second vehicle precedes the first target and the second target leaves the lane.

The advantage of comprising a step of comparing a current distance between the ego vehicle and the first target vehicle and a step of alerting if said current distance is less than said set safety distance is that this allows a driver who does not want automatic regulation of the speed setpoint to nevertheless be able to be informed and manage in the face of the risk by lowering their speed themselves, for example.

According to another advantageous characteristic, the method comprises a step of continuously calculating a target speed of the ego vehicle capable of creating and/or maintaining the set safety distance between the ego vehicle and the first target vehicle, and in that it includes in particular a step of enslaving a speed of the ego vehicle to said target speed, which allows the adaptive cruise control to follow this instruction without action by the driver.

According to another advantageous characteristic, said vehicles are located on the same traffic lane and drive in the same direction, which makes it possible not to take into account vehicles located on a lane in the opposite direction, for example.

A second object of the invention is a computer program product comprising program code instructions recorded on a computer-readable medium, these instructions, when the program is executed by the computer, lead the latter to implement the process as mentioned above.

A third object of the invention is an ego motor vehicle driving assistance system comprising:
- means for detecting a first target vehicle preceding the ego vehicle and at least one other target vehicle preceding the first target vehicle
- means for evaluating at least one distance value characterizing the position of said at least one other target vehicle preceding the first target vehicle
- A computer capable of implementing the method as mentioned above, which has advantages similar to those of the method.

A fourth object of the invention is a motor vehicle comprising a powertrain, braking and accelerating means and comprising a driver assistance system as mentioned above. This vehicle has advantages similar to those of the assistance system.

The attached figures illustrate the invention:

Figure 1 shows a schematic view of a vehicle driving situation.

FIG. 2 represents a flowchart of the method according to the invention.

In the following description, the front and the rear are defined according to the direction of progression of a vehicle. In forward gear and in a straight line, the vehicle progresses from the rear to the front.

FIG. 1 schematically illustrates a motor vehicle 1 according to one embodiment of the invention. The ego (ego) vehicle can be of any kind. In particular, it may for example be a private vehicle, a utility vehicle, a truck or a bus. With reference to this figure, the ego vehicle (ego) is preceded by a first target vehicle (C1) from which it (ego) is separated by a first distance (d1). The first target vehicle (C1) itself follows a second target vehicle (C2) and is moved away from it by a second distance (d2). The first distance of (d1) is controlled by the regulation of the ego vehicle (ego) and assimilated to a safety distance (d1), however the distance between target vehicles (d2) depends on the drivers of the target vehicles (C1 and C2) and is therefore independent of the ego vehicle (ego).

This figure illustrates the case of an ego vehicle (ego) following two target vehicles (C1, C2) but the invention also applies to more target vehicles as long as the known detection means are capable of locating said vehicles.

FIG. 2 illustrates the steps of the method for assisting the driving of an ego (ego) motor vehicle according to the invention, which therefore comprises:
- a step (E0) of detecting at least two target vehicles (C1, C2) preceding the ego vehicle
- a step (E1) of evaluating at least one distance value (d2) characterizing the position of the second target vehicle (C2)
- a step (E2) of determining a set safety distance value (d1) between the ego vehicle and the first target vehicle (C1) preceding it, said set safety distance value ( ) being a function of the value of the distance (d2) characterizing the position of the second target vehicle (C2)

To perform the step (E0) of detecting at least two target vehicles (C1, C2) preceding the ego vehicle, the ego vehicle (ego) preferably has a set of sensors capable of detecting fixed or mobile objects positioned in the vicinity of the ego (ego) vehicle. These sensors can be, for example, telemetry sensors of the radar, lidar, sonar type and/or even cameras. They can detect other vehicles, pedestrians, cyclists or any type of obstacle within a given perimeter around the vehicle. The output of this detection step (E0) is therefore a Boolean which equals 1 when at least two target vehicles (C1, C2) preceding the ego vehicle (ego) have been detected and 0 otherwise. This detection is therefore dynamic over time and takes into account in particular the incursions of the vehicles which overtake the ego vehicle (ego) (called the cut-in phenomenon) and the excursions of the target vehicles (C1, C2) which come out of the channel (called the cut-out phenomenon in English).

In the event of target vehicles being detected, the output signals from the sensors are then consumed in the step (E1) of evaluating at least one distance value (d2) characterizing the position of the second target vehicle (C2). According to a preferred embodiment, the ego (ego) vehicle includes a radar device used as a distance sensing sensor. Alternatively or in addition, a camera or a stereoscopic camera can be used. Thus the combination radar – stereoscopic camera constitutes a distance sensor by data fusion. Indeed, with the use of the camera or the stereoscopic camera, similar information about the target can be acquired. The radar and the stereoscopic camera are complementary in detection in terms of range and precision. Therefore, the ego (ego) vehicle can be equipped with both at least one radar and at least one stereoscopic camera, where the radar and the stereoscopic camera can be combined and their signals merged so as to detect distances robustly and reliably. Indeed, the stereoscopic camera can be used to acquire distance information with respect to targets at short range (for example about 15 meters) and the lateral position of a close target which is difficult to detect with the radar and the radar can be used to acquire distance information to targets from medium (eg about 100 meters) to long range (eg about 250 meters) and the lateral position of a distant target that is difficult to detect with the stereoscopic camera. The output signals from these sensors are then processed in a known manner by data fusion to provide in real time a distance value (d2) characterizing the position of the second target vehicle (C2) as well as its absolute speed or its relative speed with respect to to the vehicle ego (ego).

It should be mentioned that this distance value (d2) could also be obtained by other means such as inter-vehicle communication for example, or vehicle-infrastructure or even by the processing of satellite information. This distance (d2) is preferably the inter-target vehicle distance (d2) between the at least two target vehicles (C1, C2) preceding the ego vehicle (ego), in particular between the front of the first target vehicle (C1) and the rear of the second target vehicle (C2).

Nevertheless, in the case where the inter-vehicle distance value (d2) is vitiated by a high degree of inaccuracy, for example because of the inaccuracy of the measuring means, it is preferable to use the more precise distance (d _measured ) between the ego vehicle (ego) and the second target vehicle (C2), in particular between the front of the ego vehicle (ego) and the rear of the second target vehicle (C2). In this case, in the event of detection in step (E0), the step (E1) of evaluating at least one distance value (d2) characterizing the position of the second target vehicle (C2) consumes the distance ( d _measured ) more accurate between the ego vehicle (ego) and the second target vehicle (C2) and includes a sub-step (not shown) of evaluating the inter-target vehicle distance (d2) from the distance (d _measured ) between the ego vehicle (ego) and the rear of the second target (C2). To perform this change of variable, we assume a length ( standard for the first target (C1) depending on its type. In fact, it is known how to define in a known manner on the basis of information from the sensors previously described the class of the vehicle, for example light vehicle, truck, motorcycle. We then associate, via a map, typical values for each class, for example 2 meters for a motorcycle, 4.5 meters for a light vehicle, etc. These length values could also be transmitted by the vehicles themselves via inter-communication. vehicles, thus each vehicle would communicate its length, even its dimensions and even its absolute position. In this way, the target inter-vehicle distance (d2) is directly deduced as follows:

In cases of dense flowing traffic, the distance set point set basically by the driver or as a function of the speed of the first target vehicle (C1) may prove to be inadequate. For example, in fluid plug-type use, the distances between vehicles are usually relatively constant. An operation that is more representative of human behavior must therefore make sure to have the same distance between the ego vehicle (ego) and the first target (C1) as that measured between the first target (C1) and the second target (C2). The determination of the set safety distance (d _{1 _cons} ) is therefore advantageously a function of the traffic conditions.

For this, the step (E2) of determining the set safety distance value comprises a sub-step (E2-A) of developing a first set safety distance (d _{1_trafic} ) which is a function of the traffic . To do this, this sub-step (E2-A) comprises a first sub-step (E2-A1) of determining the dynamics of the target inter-vehicle distance (d2), this sub-step (E2-A1) having for the purpose of evaluating the state of the traffic and in particular of detecting whether the traffic is fluid, that is to say that the target vehicles (C1, C2) maintain a stabilized distance, that is to say almost constant, between them. More precisely, this sub-step (E2-A1) analyzes the temporal evolution of the distance value (d2) and considers that the inter-target vehicle distance (d2) is stabilized if in the temporal sliding window of a predetermined duration this distance (d2) remains within a hysteresis zone defined by a predetermined tolerance. By way of example, the predetermined duration is taken equal to 3 seconds and the tolerance equal to 0.5 seconds multiplied by the speed of the traffic, represented for example by the speed of the ego vehicle (ego), or that of the target vehicle (C1 ) or a combination of both. Thus, for a vehicle in slow traffic, which is traveling at 10m/s, we therefore detect a stabilized distance (d2) if for 3 seconds it (d2) remains within variations of more or less 5 meters. The output of this sub-step (E2-A1) is therefore a boolean which is for example 1 when the traffic is fluid, and 0 otherwise.

Another sub-step (E2-A2) of calculating a statistical value representative of the target inter-vehicle distance (d _{2_stat} ), preferably carried out in parallel with the previous sub-step (E2-A1) of determining the dynamic of the target inter-vehicle distance, then consumes as input the same signal as for the previous sub-step (E2-A1) and determines a statistical value representative of the target inter-vehicle distance (d _{2_ stat} ) by calculating for example the average, or the median, of the values of the inter-vehicle distance (d2) in the same time sliding window.

In a third sub-step (E2-A3) of consolidation of the value of the stabilized target inter-vehicle distance, receiving the output signals from the previous sub-steps (E2-A1 and E2-A2) the multiplication of the two input signals (0;1, d _{2_sta t} ) from which there results at output a consolidated signal of the value of the stabilized target inter-vehicle distance (d _{2_stabilized} ) which is therefore equal to d _2-stat when the traffic is fluid and a value not available otherwise.

In the fourth sub-step (E2-A4) of consolidating the first safety distance (d _{1_trafic} ) depending on the traffic, consuming the previous output (d _{2_stabilised} ) the safety distance relative to the traffic (d _{1 _trafic} ) is then determined. which is then taken equal to the value of the stabilized target inter-vehicle distance (d _{2_stabilized} ) saturated by a minimum safety distance value (d _{1_safe} ) so as not to endanger the customer by following the first target vehicle too closely (C1). The minimum safety distance (d _{1_safety} ) is also a function of the speed and a minimum distance value can be defined by the user. Usually this distance corresponds to the distance traveled in 3 seconds (at least 1.5 seconds), or in about 30 meters (or 15 meters) for the speed of 10m/s. To regulate this distance, the speed of the ego vehicle (ego) and of the first target vehicle (C1) are necessary, in fact, the ego vehicle (ego) consumes the relative speed information and its own speed to recalculate the speed of the first target vehicle (C1) and therefore comprises at least one speed sensor for measuring the speed of the ego vehicle (ego) and transmitting it as input to this fourth sub-step (E2-A4) of consolidating the first distance (d _{1_trafic} ) safety depending on the traffic.

We therefore obtain:

The distance between the target vehicles (d2) is also advantageously used to improve the quality of the ACC during the tracking by the ego vehicle (ego) of the first target (C1). Indeed, in the case of a decrease in speed of the second target (C2) and of a first target (C1) which reacts late, the ACC of the vehicle ego (ego) would conventionally have to command a strong braking detrimental to comfort , which is avoided with the invention. Similarly, heavy braking of the first target (C1) could cause difficulties when the ACC is limited in deceleration. To solve these drawbacks, the invention makes it possible to anticipate the behavior and in particular the braking of the first target (C1) by taking into consideration the distance between the target vehicles (d2) in determining the safety distance (d1), whatever or traffic. To do this, a second sub-step (E2-B) of developing a second setpoint safety distance (d _{1_anticipation} ) aimed at keeping the sum of the two inter-vehicle distances (d1, d2) constant and equal to double of the safety distance relative to traffic (d _{1_trafic} ) consumes the first set safety distance (d _{1_trafic} ) which is multiplied by two and from this product is subtracted the target inter-vehicle distance (d2):

From where

In this way, if the first target (C1) approaches the second target (C2) then automatically the ego vehicle (ego) will move away from the first target (C1).

Then a third sub-step (E2-C) of consolidation of the setpoint safety distance value (d _{1_ cons} ) consumes the outputs of the two previous sub-steps (E2-A and E2-B), and calculates their maximum . Indeed, the safety constraint having already been taken into account during the previous sub-steps (E2-A, E2-B), the setpoint safety distance (d _{1_ cons} ) can be defined as being:

Which amounts to:

The invention has been described in the case of two vehicles (C1, C2) preceding the ego (ego) vehicle but it can be generalized to a multiplicity of target vehicles preceding the ego (ego) vehicle in its path. Thus, in step E0 of detection if more than two targets, n targets, are detected either by the means previously described or for example via inter-vehicle communication or via vehicle-to-infrastructure communication or even via satellite signals . Thus, in the evaluation step (E1) the distance values (di) characterizing the position of the target vehicles between them or with respect to the ego vehicle (ego) are evaluated. Preferably, this distance (di) corresponds to the distance between the ith target vehicle and the ith-1 target vehicle, i belonging between 2 and n. Then the step (E2) of determining the setpoint safety distance value comprises a sub-step (E2-A) of developing a first setpoint safety distance (d_{1_traffic}) which is a function of the traffic and takes into account the average of the stabilized distances between the n target vehicles detected in step (E0) of detection, the conditions linked to the stabilization being able to be relaxed with n increasing. Let i be between 2 and n:

Then the second sub-step (E2-B) of developing a second setpoint safety distance (d _{1_anticipation} ) is described as follows:

And finally the third sub-step (E2-C) of consolidating the set safety distance value (d _{1_ cons} ) is defined as above, while preferentially adding saturation, for example by a multiple k (for example 1.5 ) of the value of the minimum safety distance (d _{1_securitaire} ) in order to avoid abusive overestimations of the set safety distance (d _{1_ cons} ) in the case where several targets follow each other without respecting the safety distance:

The method may also include, following the steps previously described, a step of comparing the current distance (d1) separating the ego vehicle (ego) and the target vehicle preceding it (C1), that is to say that the vehicle ego (ego) tracks, allowing to diagnose whether the tracking of the first target (C1) complies with the set safety distance previously determined as well as an alert step if said current distance (d1) is less than the set safety distance . This alert stage is particularly suitable for drivers who do not wish to have independent speed regulation because they wish to keep control of the speed of their vehicle but who nevertheless wish to be informed of the optimum behavior to adopt. Different alert modes for non-respect of safety distances exist and can co-exist, for example the display on a central screen of the dashboard of information on the calculated safety distance and the current distance, or even by sound or haptic alert. In addition, it should be specified that a hysteresis on the setpoint safety distance can be added in the calculation loop so as not to trigger the alert untimely, preferably this hysteresis can be fixed, in connection with the measurement accuracy of the sensors, and/or integrate a dependence on the setpoint safety distance via a percentage in particular, for example 10% of the setpoint safety distance .

For drivers wishing to have speed regulation following the steps previously described, the method also comprises a step of continuously calculating a target speed of the vehicle ego (ego) capable of creating and/or maintaining the safety distance (d1) between the ego vehicle (ego) and the preceding vehicle (C1). This calculation is not the subject of the invention, it corresponds to the known servo-control methods for adaptive cruise control (Adaptive Cruise Control in English, or ACC).

Preferably, the method also comprises a step of enslaving the speed of the vehicle ego (ego) to said target speed calculated in the step previously described. An adaptive vehicle speed regulation is thus obtained with following of the preceding vehicle (C1) so as to maintain or create a safety distance (d1) without the action of the driver while minimizing unpleasant excessive braking thanks to the regulation on the second target vehicle (C2) since the behavior, in particular via the position, of the latter is taken into account in determining the safety distance (d1).

All the steps of this method according to the invention are advantageously implemented by a safety distance control module of a computer, for example an ADAS computer. This module is then connected to a vehicle dynamics module connected to the braking and acceleration means of the ego vehicle.

The driving assistance system according to the invention includes a braking module and the safety distance control module.

Claims (12)

Method for assisting the driving of an ego (ego) motor vehicle comprising
- a step (E0) of detecting a first target vehicle (C1) preceding the ego vehicle (ego) and at least one other target vehicle (C2) preceding the first target vehicle
- a step (E1) of evaluating at least one distance value (d2) characterizing the position of said at least one other target vehicle (C2) preceding the first target vehicle (C1)
- a step (E2) for determining a setpoint safety distance value ( ) between the ego vehicle (ego) and said first target vehicle (C1),
characterized in that said setpoint safety distance value ( ) is a function of said distance value (d2) characterizing the position of said at least one other target vehicle (C2) preceding the first target vehicle (C1). Method according to Claim 1, characterized in that the said at least one distance value (d2) characterizing the position of the said at least one other target vehicle (C2) preceding the first target vehicle (C1) is an inter-target vehicle distance (d2) . Method according to any one of the preceding claims, characterized in that the step (E2) of determining a setpoint safety distance value ( ) comprises a sub-step (E2-A) of generating a first set safety distance (d _{1_trafic} ) which is a function of the traffic. Method according to the preceding claim, characterized in that the sub-step (E2-A) of producing a first set safety distance comprises a first sub-step (E2-A1) of determining the dynamics of the distance ( d2) characterizing the position of said at least one other target vehicle (C2) preceding the first target vehicle (C1), a second sub-step (E2-A2) of calculating a statistical value representative of a distance between target vehicles (d _{2_stat} ), a third sub-step (E2-A3) of consolidation of a value of the stabilized target inter-vehicle distance and a fourth sub-step (E2-A4) of consolidation of the first distance (d _{1_trafic} ) safety depending on the traffic. Method according to Claim 3 or 4, characterized in that the sub-step (E2-A) of generating a first set safety distance comprises a second sub-step (E2-B) of generating a second distance setpoint safety distance (d _{1_anticipation} ) as a function of the first setpoint safety distance (d _{1_trafic} ) and the distance (d2) characterizing the position of said at least one other target vehicle (C2) preceding the first target vehicle (C1). Method according to any one of the preceding claims, characterized in that the step (E2) of determining a setpoint safety distance value ( ) comprises a third sub-step (E2-C) of consolidating the setpoint safety distance value (d _{1_cons} ). Method according to any one of the preceding claims, characterized in that it comprises a step of comparing a current distance (d1) between the ego vehicle (ego) and the first target vehicle (C1) and a step of alerting if said current distance (d1) is less than said set safety distance ( ). Method according to any one of the preceding claims, characterized in that it comprises a step of continuously calculating a target speed of the ego vehicle capable of creating and/or maintaining the set safety distance ( ) between the ego vehicle (ego) and the first target vehicle (C1), and in that it comprises in particular a step of enslaving a speed of the ego vehicle (ego) to said target speed. Method according to any one of the preceding claims, characterized in that the said vehicles (ego, C1, C2) are located on the same traffic lane and are traveling in the same direction. Computer program product comprising program code instructions recorded on a computer-readable medium, characterized in that it comprises instructions which, when the program is executed by the computer, cause the latter to implement the method according to any one of claims 1 to 9. Driving assistance system for a motor vehicle ego (ego) comprising:
- a means of detecting at least two target vehicles (C1, C2) preceding the ego vehicle (ego)
- a means for evaluating at least one distance value (d2) characterizing the position of the second target vehicle (C2)
- a computer capable of implementing the method according to any one of claims 1 to 9. Motor vehicle (ego) comprising a powertrain, acceleration and braking means and characterized in that it comprises a driving assistance system according to the preceding claim.