Selecting a target vehicle for a driver assistance function

Abstract

The invention relates to a method for managing a driving assistance function of a motor vehicle comprising the following steps: - allocation (201) of a risk level to the right and left of the current lane, the risk level being representative of a risk of crossing limits of the current lane; - determination (202) of a position of at least one other vehicle in the environment of the motor vehicle, the position being associated with the right limit or the left limit; - determination (203) of a proportion of the other vehicle present in the current lane; - decision (204) to select (205) or not said other vehicle as the target vehicle for the driving assistance function, as a function of said determined proportion and as a function of the risk level associated with the limit associated with the position of the other vehicle. FIG. 2

Description

Title of the invention: Selecting a target vehicle for a driving assistance function

[0001] The present invention belongs to the field of driving assistance in a motor vehicle, and relates in particular to driving assistance functions taking into account other vehicles circulating in the environment of the vehicle, called target vehicles.

[0002] The term “vehicle” means any type of vehicle such as a private, utility or heavy goods vehicle.

[0003] The term "driving assistance" for a vehicle means any method capable of assisting in driving the vehicle. The method may thus consist of partially or totally steering the vehicle or providing any type of assistance to a physical person driving the vehicle. Driving assistance functions may relate to different levels of autonomy. The OICA scale, for "Organisation International des Constructeurs Automobile" (International Organization of Motor Vehicle Manufacturers), provides for 6 levels. Other scales are provided to define the levels of autonomy permitted by driving assistance systems, for example the SAE scale, for "Society of Automotive Engineers".

[0004] Thus, the driving assistance covers manual driving assistance functions, for the lowest levels, such as levels 1 and 2 of the aforementioned scales, and autonomous vehicle control functions for the highest levels of autonomy.

[0005] Driving assistance systems, such as AD AS for example, for “Advanced Driver-Assistance Systems” in English, make it possible to assist the driver of the vehicle or even to fully control certain parameters of the vehicle's driving, such as the longitudinal trajectory, the speed in particular, and the lateral trajectory, turning or changing lanes in particular.

[0006] These systems make it possible to improve driving comfort as well as safety, by taking advantage of data from vehicle sensors, such as radar or lidar data, cameras and / or geolocation devices.

[0007] Certain driving assistance functions, such as the ACC function in particular, for “Adaptive Cruise Control” in English, take into account the presence or absence of other vehicles in the vehicle's current lane of travel.

[0008] In the case where other vehicles are located in a lane adjacent to the current lane, it is difficult to anticipate whether or not the other vehicle will cross the boundary between the adjacent lane and the current lane, to switch into the current lane in front of the vehicle.

[0009] Such uncertainty may lead the driving assistance function to brake when it is not necessary, or to not take the other vehicle into account, which may cause a collision.

[0010] There is therefore a need to improve both the safety and driving comfort of driving assistance functions taking into account other road users.

[0011] The present invention improves the situation.

[0012] To this end, a first aspect of the invention relates to a method for managing a driving assistance function of a motor vehicle comprising the following steps: - allocation of a risk level to the right of a current lane of the vehicle and / or a risk level to the left of the current lane, the risk level to the right being representative of a risk of crossing a right limit of the current lane and the risk level to the left being representative of a risk of crossing a left limit of the current lane; - determining a position of at least one other vehicle in the environment of the motor vehicle, the position being associated with the right limit or the left limit; - determination of a proportion of said other vehicle present in the current lane; - decision whether or not to select the said other vehicle as the target vehicle for the driving assistance function, depending on the said determined proportion and depending on the level of risk associated with the limit associated with the position of the other vehicle.

[0013] Thus, it is made possible to anticipate more precisely the tipping of another vehicle into the current lane, which improves driving comfort as well as the safety associated with the driving assistance function.

[0014] According to embodiments, the right risk level and the left risk level may be assigned based on vehicle sensor data.

[0015] Thus, differentiated crossing risk levels can be determined for the left boundary and the right boundary, which improves the accuracy associated with decision-making, and consequently improves the operation of the driving assistance function. In addition, the risk levels can be continuously updated.

[0016] Alternatively, the right risk level and the left risk level may be assigned based on map data stored by the motor vehicle.

[0017] Thus, differentiated crossing risk levels can be determined for the left boundary and the right boundary, which improves the accuracy associated with decision-making, and consequently improves the operation of the driving assistance function. In addition, the risk levels can be continuously updated.

[0018] According to embodiments, the decision whether or not to select said other vehicle as the target vehicle for the driving assistance function may to understand : - the determination of a threshold value based on the level of risk attributed to the limit associated with the position of the other vehicle; - the comparison of the said determined proportion with the determined threshold value; - the selection of said other vehicle as a target for the driving assistance function, only if the determined proportion is greater than the threshold value.

[0019] Such decision-making is both precise and quick to execute for a control device having computing means. High responsiveness in the implementation of the selection of target vehicles is thus enabled, which improves the speed of implementation of the driving assistance function.

[0020] According to embodiments, the right risk level and the left risk level may be assigned from a set of several possible risk levels.

[0021] Thus, the determination of the risk level is simplified, the different driving situations being able to be determined in advance.

[0022] In addition, the set of several possible risk levels includes one or more of the following levels: - a first level of risk attributed to the right limit or the left limit when the current lane is limited by a roadside edge on the right or left; - a second risk level assigned to the right limit or the left limit when the current lane is limited by a continuous line on the right or left; - a third risk level assigned to the right limit or the left limit, when the current route is limited by a broken line on the right or left; - a fourth risk level assigned to the right limit or the left limit, when the current lane is joined on the right or left by an insertion lane.

[0023] Thus, it is made possible to differentiate several driving situations, which encompasses all possible cases when driving the vehicle. The selection of target vehicles is thus improved regardless of the driving situation.

[0024] In addition, each of the possible risk levels can be associated with a predefined threshold value.

[0025] Thus, the determination of the threshold value is simplified, which allows rapid selection of target vehicles for the driving assistance function.

[0026] Additionally, a threshold value associated with the second risk level may be greater than a threshold value associated with the third risk level, and / or a threshold value associated with the third risk level is greater than a threshold value associated with the fourth risk level.

[0027] Thus, the comparison is adapted to each driving situation, which makes it possible to improve the precision associated with the selection of target vehicles for the function. driving assistance.

[0028] A second aspect of the invention relates to a computer program comprising instructions for implementing the method according to the first aspect of the invention, when these instructions are executed by a processor.

[0029] A third aspect of the invention relates to a control device for a motor vehicle, comprising a processor configured to: - assign a risk level to the right of a current lane of the vehicle and / or a risk level to the left of the current lane, the risk level to the right being representative of a risk of crossing a right limit of the current lane and the risk level to the left being representative of a risk of crossing a left limit of the current lane; - determining a position of at least one other vehicle in the environment of the motor vehicle, the position being associated with the right limit or the left limit; - determine a proportion of said other vehicle present in the current lane; - decide whether or not to select the said other vehicle as the target vehicle for the driving assistance function, depending on the said determined proportion and depending on the level of risk associated with the limit associated with the position of the other vehicle.

[0030] Other characteristics and advantages of the invention will appear on examining the detailed description below, and the appended drawings in which:

[0031] [Fig-1] illustrates a motor vehicle according to embodiments of the invention;

[0032] [Fig.2] is a diagram illustrating the steps of a process according to rea modes lization of the invention;

[0033] [Fig.3a] illustrates a motor vehicle according to embodiments of the invention, in a first driving situation;

[0034] [Fig.3b] illustrates a motor vehicle according to embodiments of the invention, in second first driving situation;

[0035] [Fig.3c] illustrates a motor vehicle according to embodiments of the invention, in second third driving situation;

[0036] [Fig.3c] illustrates a motor vehicle according to embodiments of the invention, in second fourth driving situation;

[0037] [Fig.4] illustrates a motor vehicle according to embodiments of the invention, in a driving situation in which another vehicle is detected;

[0038] [Fig.5] illustrates a control device according to embodiments of the invention.

[0039] [Fig.l] illustrates a motor vehicle 100, according to embodiments of the invention.

[0040] The vehicle 100 notably comprises a control device 101, which may be a centralized control device in charge of a plurality of functions of the vehicle. car. The control device 101 may be of the ECU type in particular, for “Electronic Control Unit” in English.

[0041] The control device 101 can at least be in charge of selecting target vehicles for a driving assistance function implemented by a driving assistance module 102 of the vehicle, also called AD AS, for “Advanced Driver Assistance Systems” in English. The AD AS module 102 is capable of implementing at least one driving assistance function on the basis in particular of data from at least one sensor.

[0042] The vehicle 100 notably comprises a first sensor 105.1 which may be an image acquisition device, such as a camera capable of acquiring images of a scene in front of the vehicle 100. The image acquisition device 105.1 may be arranged in an upper part of a windshield of the vehicle 100.

[0043] The vehicle 100 may comprise at least one other sensor 105.N, and more generally Nl other sensors, N being an integer greater than or equal to 2. The at least one other sensor 105.N may be a radar or a lidar for example.

[0044] Based on data from one of the vehicle's sensors, the AD AS module 102 is capable of implementing at least a first function for controlling a lateral and / or longitudinal trajectory of the vehicle 100.

[0045] No restrictions are attached to the vehicle 100, in particular to the level of driving autonomy permitted by the vehicle. The AD AS module 102 can assist the driver in piloting the vehicle, in particular for determining or maintaining the speed or acceleration, or can ensure autonomous piloting of the vehicle, without the contribution of the driver. Driving assistance thus also covers automatic piloting of the vehicle.

[0046] According to the invention, the at least one first driving assistance function implemented by the AD AS module 102 is a function capable of taking into account one or more target vehicles traveling on the same road as the vehicle 100 or on an adjacent road.

[0047] Such consideration of a target vehicle may in particular take into account the position, speed, acceleration and / or direction of movement of the target vehicle.

[0048] The first function may for example be a function for adapting the longitudinal speed of the vehicle, also called ACC, for “Adaptive Cruise Control” in English. Other driving assistance functions taking into account a target vehicle may alternatively or additionally be implemented by the AD AS 102 module.

[0049] The vehicle 100 may further comprise a memory 103 capable of storing data used by the control device 101, by the ADAS module 102 and / or by any other module of the vehicle 100. The memory 103 may in particular store cartographic data, representative of a given territory or an area comprising a current position of the vehicle. The cartographic data can be updated remotely via a communication interface 106, which can be a cellular interface allowing the vehicle 100 to access a cellular network, such as a 3G, 4G, 5G network or any other generation, for example. Thus, the vehicle 100 can obtain updated cartographic data stored in a remote server.

[0050] The vehicle 100 can further comprise a satellite positioning module, of the GPS type for example, for “Global Positioning System”, capable of obtaining and maintaining a current position of the vehicle.

[0051] Such a current position of the vehicle 100 may be superimposed by the control device 101 and / or by the ADAS module 102, with the map data in order to locate the vehicle 100 in the road infrastructure surrounding it. Such an overlay may be used by the ADAS 102 as input data of a driving assistance function. Furthermore, as described in the following, such an overlay may be used by the control device 101 when selecting the target vehicle for managing a driving assistance function, according to the invention.

[0052] [Fig.2] is a diagram illustrating the steps of a method for managing a driving assistance function, according to embodiments of the invention.

[0053] In a step 200, the control device 101 obtains data representative of the current lane on which the vehicle 100 is traveling, in particular data relating to a type of right limit and / or left limit of the current lane. Such data representative of the current lane can be obtained: - by superimposing the current position from the satellite positioning module 104 and the cartographic data stored in the memory 103 or obtained from a remote server. Indeed, such superposition makes it possible to identify a type of right limit and / or left limit of the current lane of the vehicle when the cartographic data includes such details on the traffic lanes that they represent; and / or - from sensor data, in particular data from the first sensor 105.1 capable of obtaining images or series of images representative of a scene facing the vehicle, i.e. directed towards a half-space in front of the vehicle. No restriction is attached to the manner in which the data representative of the current lane are derived from the image or series of images acquired by the first sensor 105.1. Methods for identifying lines in images or series of images are known and are not described further in this description.

[0054] Data representative of the track may furthermore come from the other sensor 105.N, in particular when the other sensor 105.N is a radar or a lidar, capable of detecting when the right or left limit is a roadside.

[0055] In a step 201, the control device 101 assigns a risk level to the right of the current lane of the vehicle and / or a risk level to the left of the current lane, as a function of at least some of the data obtained in step 200, in particular as a function of the type of limit to the right and the type of limit to the left of the current lane. The risk level to the right is representative of a risk of crossing the right limit of the current lane and the risk level to the left is representative of a risk of crossing the left limit of the current lane.

[0056] For example, the right risk level and the left risk level may be assigned from a set of several possible risk levels, or predetermined. The set of several possible risk levels may include one or more of the following levels: - a first level of risk attributed to the right limit or the left limit when the current lane is limited by a roadside edge on the right or left; - a second risk level assigned to the right limit or the left limit when the current lane is limited by a continuous line on the right or left; - a third risk level assigned to the right limit or the left limit, when the current route is limited by a broken line on the right or left; - a fourth risk level assigned to the right limit or the left limit, when the current lane is joined on the right or left by an insertion lane.

[0057] The risk levels can be compared with each other, in particular according to the degree of risk they represent. For example, the first risk level may be a “zero risk”, that is to say that the risk of crossing the right or left limit associated with the first risk level is very low. Similarly, the second risk level may be a “low risk”, the third risk level may be a “medium risk” and the fourth risk level may be a “high risk”.

[0058] According to embodiments, in step 201, the control device 101 assigns two risk levels: a right risk level to the right limit of the current lane and a left risk level to the left limit of the current lane.

[0059] Figures 3a to 3d illustrate driving situations corresponding respectively to the four aforementioned risk levels.

[0060] [Fig.3a] illustrates a vehicle 100 according to embodiments of the invention, in a first driving situation.

[0061] In the first driving situation, one of the limits of a current lane 300 in which the vehicle 100 is traveling is a roadside edge 301. In this case, in [Fig. 3a], it is a right roadside edge 301 of the current lane 300. In this case, the risk of another vehicle crossing the roadside edge 301 from the right is zero and therefore corresponds to the first risk level attributed to the right limit of the current lane 300.

[0062] [Fig.3b] illustrates the vehicle 100 according to embodiments of the invention, in a second driving situation.

[0063] In the second driving situation, one of the limits of the current lane 300 in which the vehicle 100 is traveling is a continuous line 311. In this case, it is the limit to the right of the current lane 300. In this case, the risk of a vehicle crossing the continuous line 311 from a lane 310 to the right of the current lane is low, and therefore corresponds to the second level of risk attributed to the right limit of the current lane 300.

[0064] [Fig.3c] illustrates the vehicle 100 according to embodiments of the invention, in a third driving situation.

[0065] In the third driving situation, one of the limits of the current lane 300 in which the vehicle 100 is traveling is a broken line 321. In this case, it is the limit to the left of the current lane 300. In this case, the risk of a vehicle crossing the broken line 321 from a lane 320 to the left of the current lane 300 is medium, and therefore corresponds to the third risk level attributed to the left limit of the current lane 300.

[0066] [Fig.3d] illustrates the vehicle 100 according to embodiments of the invention, in a fourth driving situation.

[0067] In the fourth driving situation, one of the limits of the current lane 300 in which the vehicle 100 is traveling is an oblique broken line 331 which indicates that the current lane is joined by an insertion lane. In this case, this is the limit to the right of the current lane 300. In this case, the risk of a vehicle crossing the broken line 331 to join the current lane 300 is high, and therefore corresponds to the fourth risk level attributed to the right limit of the current lane 300.

[0068] Referring again to [Fig. 2], at a step 202, the control device 101 detects a position of at least one other vehicle relative to the current lane of the motor vehicle. The detection of such a position may be based on data from sensors, such as sensors 105.1 and 105.N, or may be based on communication between vehicles, in particular V2V type communication, or with the road infrastructure, in particular V2I type communication. V2V corresponds to “Vehicle To Vehicle” and V2I corresponds to “Vehicle To Infrastructure” in English. The detection may comprise the identification of another vehicle in the environment of the vehicle 100, then the identification of the position of said other vehicle, relative to the current lane. Such detection being known, it is not described further in the present description.

[0069] Such position detection can in particular identify the limit of the current lane 300 to which the other vehicle is closest, among the right limit and the left limit. The vehicle thus detected is associated with the right limit or the left limit by the control device 101.

[0070] At a step 203, the control device 101 determines a proportion of the other vehicle present in the current lane of the vehicle 100.

[0071] Such a proportion thus indicates: - if the other vehicle is completely in the adjacent lane, on the other side of the boundary associated with the other vehicle. In this case, the proportion of presence in the current lane is equal to 0; - if the other vehicle is completely in the current lane. In this case, the proportion of presence in the current lane is equal to 1; and - if the other vehicle is partially in the current lane, i.e. straddling the limit associated with it. In this case, the proportion of presence is strictly between 0 and 1.

[0072] [Fig.4] illustrates a motor vehicle according to embodiments of the invention, in a driving situation in which another vehicle 401 is detected in the environment of the vehicle 100.

[0073] More precisely, [Fig.4] illustrates the case where the other vehicle 401 straddles one of the limits of the current lane 300, namely the right limit 400. The other vehicle 401 is thus partially in the current lane 300 and in zone 410 which may be an adjacent lane or a roadside edge.

[0074] The proportion of presence of the other vehicle 401 may be equal to the ratio of a first distance 402 to a second distance 403. The first distance 402 corresponds to the distance between the limit 400 and the part of the other vehicle 401 in the current lane which is furthest from the limit 400. The second distance may correspond to a lateral dimension of the other vehicle 401. A lateral dimension is a dimension normal to a main direction of the current lane.

[0075] However, the aforementioned ratio is given for illustrative purposes and no restriction is attached to the manner of determining the proportion of presence in the current lane of the other vehicle 401.

[0076] In a step 204, the control device 101 determines, as a function of the proportion determined in step 203, and as a function of the risk level assigned to the limit of the current lane to which the other vehicle is closest, whether the other vehicle is a target vehicle or not for the driving assistance function.

[0077] For this purpose, a set of rules can be applied by the control device 101 to the risk level assigned to the limit associated with the other vehicle and to the determined proportion, the set of rules indicating at output whether the other vehicle is a target vehicle or not for the driving assistance function.

[0078] If this is the case, the control device 101 selects the other vehicle as target vehicle at a step 205, and returns to step 202 if a second other vehicle is detected in the environment of the vehicle 100. Otherwise, if no other vehicle is detected in the environment of the vehicle 100, the method returns to step 200. The method can thus be iterated, which allows an update of the target vehicle(s) according to the evolution of the current position of the vehicle 100.

[0079] The step 205 of selecting the other vehicle as a target vehicle may comprise the transmission of target information, identifying the other vehicle, to the AD AS module 102, so that it takes the other vehicle into account as a target vehicle when implementing the first driving assistance function.

[0080] If this is not the case, i.e. if the other vehicle is not selected as the target vehicle for the driving assistance function, the method returns to step 202 if a second other vehicle is close to the current lane. Otherwise, if no other vehicle is detected in the environment of the vehicle 100, the method returns to step 200. The method can thus be iterated, which allows an update of the target vehicle(s) according to the evolution of the current position of the vehicle 100.

[0081] The set of rules may in particular comprise the comparison of the proportion determined in step 203 for the other vehicle, with a threshold value which depends on the risk level assigned to the limit of the current lane which is closest to the other vehicle. For example, if the other vehicle is closer to the right limit of the current lane, a threshold value is determined by the control device 101 as a function of the risk level assigned to the right limit of the current lane.

[0082] If the proportion determined in step 203 for the other vehicle is greater than or equal to the threshold value, then the other vehicle is selected as the target vehicle for consideration by the driving assistance function. Otherwise, the other vehicle is ignored and is not selected as the target vehicle for implementation of the driving assistance function.

[0083] In the following, an example of determining threshold values ​​is given for illustrative purposes.

[0084] For example, each risk level of the set of risk levels may be associated in a predetermined manner with a given threshold value.

[0085] Thus: - the first risk level is associated with a first threshold value; - the second risk level is associated with a second threshold value; - the third risk level is associated with a third threshold value; and / or - the fourth risk level is associated with a fourth threshold value.

[0086] For example, the first threshold value may be equal to 0.25, or 25%. As a reminder, the first risk level corresponds to the situation in [Fig.3a] in which the limit of the current lane considered is a roadside. Consequently, any other A vehicle close to the roadside, and whose proportion of presence in the current lane is less than 0.25, is not selected as a target. Indeed, it is likely that the other vehicle is stationary, for example parked on the roadside. On the other hand, any other vehicle close to the roadside and whose proportion of presence in the current lane is greater than or equal to 0.25 is selected as a target vehicle. Indeed, since there is no traffic lane on the other side of the roadside, it is likely that the vehicle is traveling on the current lane, although partially on the roadside.

[0087] Preferably, the second threshold value is greater than the third threshold value which is greater than the fourth threshold value.

[0088] For example, the second threshold value is equal to 0.75, or 75%, the third threshold value is equal to 0.5, or 50%, and the fourth threshold value is equal to 0.25, or 0.25%. In this case, the fourth threshold value is equal to the first threshold value. Alternatively, the first and fourth threshold values ​​may be different.

[0089] Thus, in the second driving situation of [Fig.3b], associated with a low risk of insertion, if the other vehicle is close to the right limit 311 of the current lane, its proportion of presence is compared to 0.75, and, if it is greater than or equal to 0.75, then the other vehicle is selected as the target vehicle.

[0090] In the third driving situation of [Fig.3c], associated with a moderate risk of insertion, if the other vehicle is close to the left limit 321 of the current lane 310, its proportion of presence is compared to 0.50, and, if it is greater than or equal to 0.50, then the other vehicle is selected as the target vehicle.

[0091] In the fourth driving situation of [Fig.3d], associated with a high risk of insertion, if the other vehicle is close to the right limit 331 of the current lane 310, its presence proportion is compared to 0.25, and, if it is greater than or equal to 0.25, then the other vehicle is selected as the target vehicle.

[0092] [Fig.5] shows the structure of a control device 101 according to modes of realization of the invention.

[0093] The control device 101 comprises a processor 501 configured to communicate unidirectionally or bidirectionally, via one or more buses or via a direct wired connection, with a memory 502 such as a memory of the “Random Access Memory” type, RAM, or a memory of the “Read Ordy Memory” type, ROM, or any other type of memory (Flash, EEPROM, etc.). Alternatively, the memory 502 comprises several memories of the aforementioned types.

[0094] The memory 502 is capable of storing, permanently or temporarily, at least some of the data used and / or resulting from the implementation of the method described with reference to [Fig.2].

[0095] In particular, the memory 502 can store the aforementioned associations between values threshold and risk levels, as well as the set of at least one rule whose application indicates whether another vehicle is a target vehicle or not for the driver assistance function.

[0096] The processor 501 is capable of executing instructions, stored in the memory 502, for implementing the steps of the method according to the invention, described with reference to [Fig. 2]. Alternatively, the processor 501 can be replaced by a microcontroller designed and configured to carry out the steps of the method according to the invention, described with reference to [Fig. 2].

[0097] The control device 101 comprises a first interface 503 capable of obtaining the data during step 200, from the sensor(s) 105.1 and 105.N, the memory 103 of the vehicle 100, the GPS module 104 and / or the communication module 106.

[0098] The control device 101 may further comprise a second interface 504 capable of communicating with the AD AS module 102, in particular to indicate to it the vehicle(s) selected as target vehicles.

[0099] The control device 101 may comprise other interfaces for communicating with other equipment of the vehicle 100.

[0100] The present invention is not limited to the embodiments described above as examples; it extends to other variants.

Claims

Claims

1. Method for managing a driving assistance function of a motor vehicle (100) comprising the following steps: - allocation (201) of a risk level to the right of a current lane (300) of the vehicle and / or a risk level to the left of the current lane, the risk level to the right being representative of a risk of crossing a right limit (301; 311; 331) of the current lane and the risk level to the left being representative of a risk of crossing a left limit (321) of the current lane; - determination (202) of a position of at least one other vehicle (401) in the environment of the motor vehicle, the position being associated with the right limit or the left limit; - determination (203) of a proportion of said other vehicle present in the current lane;- decision (204) to select (205) or not said other vehicle as target vehicle for the driving assistance function, depending on said determined proportion and depending on the risk level associated with the limit associated with the position of the other vehicle.;

2. The method of claim 1, wherein the right risk level and the left risk level are assigned based on sensor data (105.1; 105.N) of the vehicle (100).

3. The method of claim 1, wherein the right risk level and the left risk level are assigned based on map data stored by the vehicle (100).

4. Method according to one of the preceding claims, wherein the decision (204) to select (205) or not said other vehicle (401) as the target vehicle for the driving assistance function comprises: - determining a threshold value as a function of the risk level attributed to the limit associated with the position of the other vehicle; - comparing said determined proportion with the determined threshold value; - selecting said other vehicle as the target for the driving assistance function, only if the determined proportion is greater than the threshold value.

5. A method according to any preceding claim, wherein the right risk level and the left risk level are assigned among a set of several possible risk levels.

6. Method according to claim 5, wherein the set of several possible risk levels comprises one or more of the following levels: - a first risk level assigned to the right limit or the left limit when the current lane (300) is limited by a roadside (301) on the right or on the left; - a second risk level assigned to the right limit or the left limit when the current lane is limited by a continuous line (311) on the right or on the left; - a third risk level assigned to the right limit or the left limit, when the current lane is limited by a broken line (321) on the right or on the left; - a fourth risk level assigned to the right limit or the left limit, when the current lane is joined on the right or on the left by an insertion lane (410).

7. A method according to claim 4 and claim 5 or 6, wherein each of the possible risk levels is associated with a predefined threshold value.

8. The method of claims 6 and 7, wherein a threshold value associated with the second risk level is greater than a threshold value associated with the third risk level, and / or a threshold value associated with the third risk level is greater than a threshold value associated with the fourth risk level.

9. Computer program comprising instructions for implementing the method according to one of the preceding claims, when these instructions are executed by a processor (501).

10. Control device (101) for a motor vehicle (100), comprising a processor (501) configured to: - assign a risk level to the right of a current lane (300) of the vehicle and / or a risk level to the left of the current lane, the risk level to the right being representative of a risk of crossing a right limit (301; 311; 331) of the current lane and the risk level to the left being representative of a risk of crossing a left limit (321) of the current lane; - determine a position of at least one other vehicle (401) in the environment of the motor vehicle, the position being associated with the right limit or the left limit; - determine a proportion of said other vehicle present in the current lane; - decide whether or not to select the said other vehicle as the target vehicle for the driving assistance function, depending on the said determined proportion and depending on the level of risk associated with the limit associated with the position of the other vehicle.

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