WO2018006963A1

WO2018006963A1 - A driver assistance system

Info

Publication number: WO2018006963A1
Application number: PCT/EP2016/066127
Authority: WO
Inventors: Johan Bjernetun; Henrik Andersson
Original assignee: Volvo Truck Corp
Current assignee: Volvo Truck Corp
Priority date: 2016-07-07
Filing date: 2016-07-07
Publication date: 2018-01-11
Anticipated expiration: 2019-01-07

Abstract

The present invention relates to a driver assistance system (100) arranged to control an active cruise control system (108) of a vehicle, said active cruise control system (108) being at least operable in a minimum speed limit operating state; wherein said driver assistance system (100) comprises a device (102) mountable to a first vehicle (1), the device (102) comprising a control unit (104), wherein the device (102) comprises at least one sensor (106, 202, 204) connected to the control unit (104) and arranged to detect a second vehicle (2) in the vicinity of the first vehicle (1), wherein the control unit (104) is configured to control the active cruise control system (108) of the first vehicle (1) to be operated in the minimum speed limit operating state if the at least one sensor (106, 202, 204) detects that said first vehicle (1) is overtaking said second vehicle (2).

Description

A DRIVER ASSISTANCE SYSTEM

TECHNICAL FIELD

The present invention relates to a driver assistance system. The invention also relates to method for controlling an active cruise control system. The invention is applicable on vehicles, in particularly low, medium and heavy duty vehicles commonly referred to as trucks. Although the invention will mainly be described in relation to a truck, it may also be applicable for any other type of vehicle driving on roads with surrounding traffic.

BACKGROUND

In the field of vehicles, in particularly low-, medium- and heavy duty vehicles commonly referred to as trucks, there is a continuous demand of improvements relating to various aspects thereof, such as driving comfort, engine performance, fuel savings, etc. In particular when relating to trucks, it is desirable to improve the smoothness and intuitively of driving when other vehicles are in the surrounding, that can thus improve fuel economy and safety. This is especially applicable in cases when a truck is overtaking another vehicle, which overtaking is often associated with a relatively extensive time period where queues are easily building up behind the truck.

Overtaking by heavy duty vehicles are often problematic as the vehicle that is being overtaken might increase its vehicle speed when being overtaken, which thus further increase the time period of overtaking the vehicle in comparison to what was initially determined/estimated.

EP 2 060 466 relates to a driver assistance system for motor vehicles, such as trucks. An object of the system in EP 2 060 466 is to improve the flow of traffic and thus to reduce traffic congestions and accidents. The system in EP 2 060 466 can, for example, control the vehicle to keep a sufficient distance to the vehicle in front.

Although EP 2 060 466 describes a system for a vehicle intending to improve traffic flow, it is still in need of further improvements in terms of e.g. drivability of the vehicle. SUMMARY

It is an object of the present invention to provide a driver assistance system which at least partially overcomes the deficiencies of the prior art. This is achieved by a driver assistance system according to claim 1 .

According to a first aspect of the present invention, there is provided a driver assistance system arranged to control an active cruise control system of a vehicle, the active cruise control system being at least operable in a minimum speed limit operating state; wherein the driver assistance system comprises a device mountable to a first vehicle, the device comprising a control unit, wherein the device comprises at least one sensor connected to the control unit and arranged to detect a second vehicle in the vicinity of the first vehicle, the control unit being configured to control the active cruise control system of the first vehicle to be operated in the minimum speed limit operating state if the at least one sensor detects that the first vehicle is overtaking the second vehicle.

The wording "minimum speed limit operating state" should be understood to mean that the first vehicle is prevented from being driven at a speed below a

predetermined/preset speed limit, which will be described further below. As an example, if the first vehicle has initiated overtaking of the second vehicle, operating the active cruise control system in the minimum speed limit operating state prevents the first vehicle from reducing engine torque. Thus, the first vehicle is inhibited from reducing engine torque. The minimum speed limit operating state can also relate to a dynamic lower speed limit, which is dependent on the present vehicle speed of the second vehicle. For example, a predetermined or preset difference in vehicle speed between the first vehicle and the second vehicle may always (during the overtaking) be provided for the first vehicle. Hereby, if the second vehicle reduces its vehicle speed during overtaking thereof, the minimum allowable speed for the first vehicle may also be reduced. Likewise, if the second vehicle increases its vehicle speed during overtaking thereof, the minimum allowable speed for the first vehicle is increased within currently allowable speed limits of the road.

Furthermore, the "vicinity" of another vehicle is of course dependent on the specific sensor used. Hence, sensors of different kind are able to detect surrounding vehicles at different distances from the vehicle. However, the wording of the present disclosure should be understood to mean that the second vehicle is positioned such that it can be overtaken by the first vehicle.

Still further, an active cruise control system should be interpreted as a cruise control system arranged to adapt its speed to various driving conditions and ambient traffic conditions. The active cruise control system of the vehicle can thus, for example and as will be described below, adapt the vehicle speed based on vehicles driving ahead of the vehicle as well as based on vehicles driving behind the vehicle. The present invention is based on the insight that by providing a minimum speed limit operating state for the vehicle, fuel saving functionalities of the vehicle, which may also reduce the vehicle speed unfavorably, can be inhibited. An advantage is thus that the first vehicle will be able to overtake the second vehicle in a relatively efficient manner. Thus, the risk of unintentionally reducing the vehicle speed due to fuel saving functionalities of the vehicle is reduced and overtaking can be executed relatively fast which in turn minimizes queue formation behind the vehicles, producing a more continuous traffic flow. It is thus beneficial from a traffic flow point of view which can thus also reduce the number of traffic accidents. By providing an improved driver assistance system, a reduction in fuel consumption can also be achieved. The present invention may be especially beneficial for autonomous vehicles where vehicle operators take few, or no, decisions regarding vehicle speed, etc. The system may thus preferably be controlled when other vehicles are present in the vicinity of the first vehicle and when the first vehicle detects overtaking of the second vehicle.

According to non-limiting examples, the control unit may in addition be configured to control the active cruise control system in relatively "difficult" driving situations where e.g. the road comprises a plurality of lanes, or where the traffic speed limits changes. In the latter situation it may be beneficial to prevent the active cruise control system to increase the vehicle speed when driving on a road with a relatively low maximum allowable speed limit, and to prevent the active cruise control system to reduce the vehicle speed when driving on a road with a relatively high maximum allowable speed limit. According to an example embodiment, the active cruise control system may be further operable in a maximum speed limit operating state, the control unit being further configured to control the active cruise control system of the first vehicle to be operated in the maximum speed limit operating state if the at least one sensor detects that the first vehicle is being overtaken by the second vehicle.

The wording "maximum speed limit operating state" should be understood to mean that the first vehicle is unable to increase its speed above a predetermined speed limit. Thus, if the at least one sensor detects that the first vehicle is being overtaken, or is about to be overtaken, by the second vehicle, the active cruise control system of the first vehicle is inhibited from increasing the vehicle speed above a predetermined speed limit. The maximum speed limit operating state has an opposite functionality in comparison to the minimum speed limit operating state described above. The maximum speed limit may also be dynamical and depend on the vehicle speed of the second vehicle overtaking the first vehicle.

An advantage is thus that the first vehicle can be overtaken in a relatively efficient manner which is associated with the same overall advantages as described above. Hence, the first vehicle enables for efficiency in traffic, both as an overtaking vehicle as well as an overtaken vehicle thereby improving traffic safety as well as reducing fuel consumption.

According to an example embodiment, the at least one sensor may be arranged to measure a vehicle speed of the second vehicle and detect that the first vehicle is overtaking the second vehicle if a detected vehicle speed of the second vehicle is lower than a vehicle speed of the first vehicle.

Hereby, it can be assured that the first vehicle is intending to overtake the second vehicle. Other alternatives of determining that overtaking is about to take place are of course conceivable. For example, if the first vehicle operates its indicator signal, this can trigger the control unit to control the active cruise control system of the first vehicle to be operated in the minimum speed limit operating state. Further, it may also be desirable to determine if the first vehicle is overtaking the second vehicle by detecting vehicle accelerations of the first and/or second vehicles. This may be especially beneficial when e.g. overtaking the second vehicle during uphill driving. According to an example embodiment, the at least one sensor may be arranged to measure a vehicle speed of the second vehicle and detect that the first vehicle is being overtaken by the second vehicle if a detected vehicle speed of the second vehicle is higher than a vehicle speed of the first vehicle.

Hereby, it can be assured that the first vehicle is about to be overtaken by the second vehicle. Other alternatives of determining that overtaking is about to take place are of course conceivable. For example, if the second vehicle operates its indicator signal, this can trigger the control unit to control the active cruise control system of the first vehicle to be operated in the maximum speed limit operating state. Another alternative is that the sensor sends detected vehicle data to the control unit which receives the data and determines the vehicle speed of the second vehicle. Detecting vehicle accelerations as described above may also be utilized when determining that the first vehicle is being overtaken by the second vehicle.

According to an example embodiment, the minimum speed limit operating state may prevent the first vehicle from being operated in a vehicle speed below a

predetermined lower threshold limit. According to an example, the predetermined lower threshold limit may be a speed limit corresponding to the vehicle speed of the first vehicle when initiating overtaking of the second vehicle. The predetermined lower threshold limit may also, as described above, be a dynamic speed limit which is dependent on the vehicle speed of the second, overtaken vehicle. According to an example embodiment, the maximum speed limit operating state may prevent the first vehicle from being operated in a vehicle speed above a

predetermined higher threshold limit. According to an example, the predetermined upper threshold limit may be a speed limit corresponding to the vehicle speed of the first vehicle when the second vehicle initiated overtaking of the first vehicle. The predetermined upper threshold limit may also, as described above, be a dynamic speed limit which is dependent on the vehicle speed of the second, overtaking vehicle.

According to an example embodiment, the at least one sensor may be arranged to measure a vehicle speed of the second vehicle, wherein the control unit is configured to control the active cruise control system of the first vehicle to be operated in the minimum speed limit operating state if a difference in vehicle speed between the first vehicle and the second vehicle is below a predetermined threshold limit.

Hereby, if the first vehicle is driving at a speed well above the speed of the second vehicle, it can be determined that overtaking of the second vehicle will be performed efficiently without the need of controlling the active cruise control system of the first vehicle to be operated in the minimum speed limit operating state. Hence, a further trigger as to when to control the active cruise control system is provided.

According to an example embodiment, the control unit may be further configured to transmit a control signal to an active cruise control system of the second vehicle, the control signal being configured to control the active cruise control system of the second vehicle to be operated in a maximum speed limit operating state if the at least one sensor detects that the first vehicle is overtaking the second vehicle.

Hereby, the control unit of the first vehicle can actively control the active cruise control of the second vehicle to be operated in the maximum speed limit operating mode. It is thus further assured that the second, overtaken vehicle will not increase its speed, which will provide for an efficient overtaking thereof. Naturally, the second vehicle must be provided with functionalities of receiving such control signals and to be controlled accordingly. The control unit may also transmit a control signal to the control unit of the second vehicle once overtaking is finished, which control signal terminates the control of the second control unit.

According to an example embodiment, the control unit may comprise a transmitter arranged to transmit the control signal to the active cruise control system of the second vehicle, and a receiver arranged to receive a signal from the at least one sensor for detecting the second vehicle in the vicinity of the first vehicle.

According to an example embodiment, the control unit may comprise a logic unit configured to determine the vehicle speed of the second vehicle and to establish the control signal to be transmitted to the active cruise control system of the second vehicle. The logic unit may thus be arranged to perform the necessary calculations and assumptions in order to establish the various control signals of the control unit. According to an example embodiment, the at least one sensor may be arranged to detect the second vehicle forwardly, laterally and/or rearwardly of the first vehicle.

The various sensor positions are advantageous since they can detect surrounding vehicles from substantially every location with regards to the first vehicle. For example, a forward seeing sensor can detect a vehicle in front of the first vehicle and thus receive information that overtaking of the second vehicle is about to take place. The forward seeing sensor can also determine that an overtaking second vehicle has finished its overtaking and thus send a signal to the control unit to end control of the active cruise control to be operated in the maximum speed limit operating state. The sensors may further advantageously determine the vehicle speed of the vehicles in the vicinity of the first vehicle.

A sideway seeing sensor arranged to detect a vehicle laterally is beneficial since it can instantaneously detect that overtaking takes place and control the active cruise control of the first vehicle accordingly depending on if it is an overtaken vehicle or an overtaking vehicle.

A rearward seeing sensor is beneficial since it can determine that overtaking is about to take place or that overtaking is finished, depending on if the first vehicle is an overtaken vehicle or an overtaking vehicle.

As an example, if the rearward seeing sensor looses track of a second vehicle and thereafter the sideway seeing sensor detects the same second vehicle, it can be assumed that the second vehicle is overtaking the first vehicle.

According to a second aspect of the present invention, there is provided a method for controlling an active cruise control system of a first vehicle, the active cruise control being at least operable in a minimum speed limit operating state; the method comprising the steps of detecting a second vehicle in the vicinity of the first vehicle; determining that the first vehicle is overtaking the second vehicle; and controlling the active cruise control system of the first vehicle to be operated in the minimum speed limit operating state.

According to an example, the method may be terminated once it is determined that the overtaking is finished. This can be determined from the above described sensors arranged at various positions of the vehicle. Thus, a signal may be received from one of the sensors that overtaking is finished. The method may also be terminated if it is determined that e.g. the time period for the overtaking is taking too long, or that the difference in vehicle speed between the first and second vehicle changes during the overtaking, which might be the case when arriving at a steep uphill of the road, etc. The method may also be terminated if registering hinders in in front of the vehicle that demands braking.

Further effects and features of the second aspect are largely analogous to those described above in relation to the first aspect.

According to a third aspect of the present invention, there is provided a computer program comprising code means for performing the steps of the above described second aspect when the program is run on a computer.

According to a fourth aspect of the present invention, there is provided a computer readable medium carrying the computer program of the third aspect.

According to a fifth aspect of the present invention, there is provided a vehicle comprising a driver assistance system according to any of the embodiments described above in relation to the first aspect.

Effects and features of the third, fourth and fifth aspects of the present invention are largely analogous to those described above in relation to the first aspect.

Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following description. The skilled person realize that different features of the present invention may be combined to create embodiments other than those described in the following, without departing from the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

The above, as well as additional objects, features and advantages of the present invention, will be better understood through the following illustrative and non-limiting detailed description of exemplary embodiments of the present invention, wherein:

Fig. 1 is a side view of a first vehicle comprising a system according to an example embodiment of the present invention, which first vehicle intending to overtake a second vehicle;

Fig. 2 is side view of a first vehicle comprising a system according to an example embodiment of the present invention, which first vehicle is about to be overtaken by a second vehicle; and Fig. 3 is a flow chart of a method for controlling an active cruise control system according to an example embodiment of the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness. Like reference character refer to like elements throughout the description.

With particular reference to Fig. 1 , there is depicted a vehicle 1 , in the following also referred to as a first vehicle 1 , driving behind a second vehicle 2. The first vehicle 1 is approaching the second vehicle 2 and is intending to overtake the second vehicle 2. The first vehicle 1 comprises a driver assistance system 100 which is arranged to control an active cruise control system 108 of the vehicle. The driver assistance system 100 comprises a device 102 which is connected to the vehicle 1 . The device 102 comprises the described active cruise control system 108. However, the active cruise control system 108 could also be arranged as an external system not arranged in the device 102. In such a case, the driver assistance system 100 is connected to the active cruise control system 108 for controlling functionalities thereof. Further, the device 102 comprises a control unit 104 and at least one sensor 106 arranged to detect other vehicles in the vicinity/surrounding environment of the first vehicle 1 . The control unit 104 comprises a transmitter 1 10, a receiver 1 12 and a logic unit 1 14. The transmitter 1 10 is arranged to transmit control signals to surrounding vehicles, as will be described further below, while the receiver 1 12 is arranged to receive control signals from other vehicles or to receive signals from the at least one sensor 106. Moreover, the logic unit 1 14 is arranged to establish control signals to be transmitted by the transmitter 1 10 and to determine e.g. vehicle speed of surrounding vehicles detected by the at least one sensor 106.

As described above, the first vehicle 1 is driving behind the second vehicle 2. The first vehicle 1 is approaching the second vehicle 2, thus driving with a speed slightly higher than the speed of the second vehicle 2. When the first vehicle 1 approaches the second vehicle 2 the sensor 106 of the first vehicle 1 detects the second vehicle 2. The sensor 106 depicted in Fig. 2 is thus a forward seeing sensor which is arranged to detect vehicles in front of the first vehicle 1 . The sensor 106 can also determine the vehicle speed of the second vehicle 2, or the vehicle speed of the second vehicle 2 relative to the first vehicle 1 . The sensor 106 may also simply send a signal to the control unit 104 whereby the logic unit 1 14 determines the vehicle speed, either the actual vehicle speed or the relative vehicle speed, of the second vehicle 2.

The control unit 104 may thus determine if the first vehicle 1 is intending to overtake the second vehicle 2. This may, for example, be determined if the vehicle speed of the first vehicle 1 is higher than the vehicle speed of the second vehicle 2.

When it is determined that the first vehicle 1 is overtaking, or will overtake, the second vehicle 2, the control unit 104 controls the active cruise control system 108 to be operated in a minimum speed limit operating state. Hereby, the first vehicle 1 will not be able to be operated in any kind of fuel saving modes which will likely reduce the vehicle speed and/or engine torque of the first vehicle 1 . The first vehicle 1 is thus prevented from being operated in a speed below a threshold limit. This threshold limit may, for example, correspond to the vehicle speed of the first vehicle 1 before initiating the overtaking of the second vehicle 2. Thus, overtaking of the second vehicle 2 can be accomplished as fast as possible. According to a non- limiting example, it may be determined to operate the active cruise control 108 in the minimum speed limit operating state if a difference in vehicle speed between the first 1 and second 2 vehicle is below a predetermined limit.

According to an example, the second vehicle 2 may also comprise a corresponding device (not shown) which is arranged to receive control signals transmitted by the transmitter 1 10 of the control unit 104 in the first vehicle 1 . Hereby, the transmitter 1 10 of the control unit 104 in the first vehicle 1 can transmit control signals to the receiver of the second vehicle 2. The control signal can instruct/control an active cruise control system of the second vehicle 2 to be operated in a maximum speed limit operating state. Hereby, the first vehicle 1 can control the second vehicle 2 not to increase its vehicle speed above a predetermined speed limit. This will thus further speed-up overtaking of the second vehicle 2. The predetermined speed limit of the maximum speed limit operating state may, for example, be set to the vehicle speed the second vehicle 2 had when overtaking thereof was initiated.

The second vehicle 2 may also comprise a sensor which detects the first vehicle 1 in front of the second vehicle 2, wherein the sensor of the second vehicle 2 can transmit a signal to the control unit of the second vehicle 2 that overtaking is finished. Hereby, the second vehicle 2 can be controlled to be operated in a normal operating mode, i.e. not be operated in the maximum speed limit operating state. Other alternatives are of course conceivable. For example, the transmitter 1 10 of the first vehicle 1 may send an updated control signal to the second vehicle 2 when overtaking is finished such that the second vehicle 2 is no longer controlled to be operated in the maximum speed limit operating state.

Turning now to Fig. 2, illustrating an example embodiment of the present invention where the first vehicle 1 is the overtaken vehicle and the second vehicle 2 is the overtaking vehicle.

In the embodiment depicted in Fig. 2, also sideways looking sensors 204 and rearward looking sensors 202 are depicted. Hence, the first vehicle 1 comprises rearward seeing sensors 202 arranged to detect vehicles behind the first vehicle 1 , sideways seeing sensors 204 arranged to detect vehicles laterally of the first vehicle 1 , as well as the above described forward seeing sensor 106.

Furthermore, in the illustrated embodiment depicted in Fig. 2, the rearward seeing sensors 202 detect the second vehicle 2, and determine, either by themselves or by sending a control signal to the control unit 104 for determining a vehicle speed of the second 2 vehicle. The rearward seeing sensors 202 or the control unit 104 may either determine the absolute speed of the second vehicle 2, or the vehicle speed of the second vehicle 2 relative to the vehicle speed of the first vehicle 1 . If the vehicle speed of the second vehicle 2 is higher than the vehicle speed of the first vehicle 1 , it can be determined that the second vehicle 2 will overtake the first vehicle 1 .

When it is determined that the second vehicle 2 is about to overtake the first vehicle 1 , the control unit 104 is configured to operate the active cruise control system 108 in the above described maximum speed limit operating state. Hereby, the first vehicle 1 is prevented from being operated in a vehicle speed above a predetermined higher threshold limit, which may be set as the vehicle speed the first vehicle 1 had at the time overtaking by the second vehicle 2 was detected/determined. Other alternatives of a predetermined higher threshold limit are of course conceivable, such as e.g. a predetermined limit lower than the vehicle speed of the second overtaking vehicle 2.

Furthermore, when the second vehicle 2 has finished its overtaking, a control signal may be delivered to the control unit 104 such that the active cruise control system 108 is no longer operated in the maximum speed limit operating state.

Reference is now made to Fig. 3, which illustrates a flow chart of a method for controlling an active cruise control system of the first vehicle 1 . As described above, the second vehicle is detected S1 in the vicinity of the first vehicle 1 . This can be accomplished by means of the various sensors 106, 202, 204 described above. It is thereafter determined S2 that the first vehicle 1 is overtaking the second vehicle 2. This can be determined by means of e.g. determining a speed difference between the first 1 and the second 2 vehicle, and/or by a sideways seeing sensor 204 detecting the second vehicle 2 laterally of the first vehicle 1 , etc. When it is determined that the first vehicle 1 is overtaking the second vehicle 2, the active cruise control system 108 of the first vehicle 1 is controlled S3 to be operated in the above described minimum speed limit operating state.

It is to be understood that the present invention is not limited to the embodiment described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.

Claims

1 . A driver assistance system (100) arranged to control an active cruise control system (108) of a vehicle (1 ), said active cruise control system (108) being at least operable in a minimum speed limit operating state; wherein said driver assistance system (100) comprises a device (102) mountable to a first vehicle (1 ), the device comprising a control unit (104), characterized in that the device (102) comprises at least one sensor (106, 202, 204) connected to the control unit (104) and arranged to detect a second vehicle (2) in the vicinity of the first vehicle (1 ), wherein the control unit (104) is configured to:

- control the active cruise control system (108) of the first vehicle (1 ) to be operated in the minimum speed limit operating state if the at least one sensor (106, 202, 204) detects that said first vehicle (1 ) is overtaking said second vehicle (2).

2. The driver assistance system (100) according to claim 1 , wherein said active cruise control system (108) is further operable in a maximum speed limit operating state, the control unit (104) being further configured to:

- control the active cruise control system (108) of the first vehicle (1 ) to be operated in the maximum speed limit operating state if the at least one sensor (106, 202, 204) detects that said first vehicle (1 ) is being overtaken by said second vehicle (2).

3. The driver assistance system (100) according to claims 1 or 2, wherein the at least one sensor (106, 202, 204) is arranged to measure a vehicle speed of the second vehicle (2) and detect that said first vehicle (1 ) is overtaking said second vehicle (2) if a detected vehicle speed of the second vehicle (2) is lower than a vehicle speed of the first vehicle (1 ).

4. The driver assistance system (100) according to any one of the preceding claims, wherein the at least one sensor (106, 202, 204) is arranged to measure a vehicle speed of the second vehicle (2) and detect that said first vehicle (1 ) is being overtaken by said second vehicle (2) if a detected vehicle speed of the second vehicle (2) is higher than a vehicle speed of the first vehicle (1 ).

5. The driver assistance system (100) according to any one of the preceding claims, wherein the minimum speed limit operating state prevents the first vehicle (1 ) from being operated in a vehicle speed below a predetermined lower threshold limit.

6. The driver assistance system (100) according to claim 2, wherein the maximum speed limit operating state prevents the first vehicle (1 ) from being operated in a vehicle speed above a predetermined higher threshold limit.

7. The driver assistance system (100) according to any one of the preceding claims, wherein the at least one sensor (106, 202, 204) is arranged to measure a vehicle speed of the second vehicle (2), wherein the control unit (104) is configured to control the active cruise control system (108) of the first vehicle (1 ) to be operated in the minimum speed limit operating state if a difference in vehicle speed between the first vehicle (1 ) and the second vehicle (2) is below a predetermined threshold limit.

8. The driver assistance system (100) according to any one of the preceding claims, wherein the control unit (104) is further configured to:

- transmit a control signal to an active cruise control system of said second vehicle (2), said control signal being configured to control the active cruise control system of said second vehicle (2) to be operated in a maximum speed limit operating state if the at least one sensor (106, 202, 204) detects that said first vehicle (1 ) is overtaking said second vehicle (2).

9. The driver assistance system (100) according to claim 8, wherein the control unit (104) comprises a transmitter (1 10) arranged to transmit the control signal to the active cruise control system of said second vehicle (2), and a receiver (1 12) arranged to receive a signal from the at least one sensor (106, 202, 204) for detecting the second vehicle (2) in the vicinity of the first vehicle (1 ).

10. The driver assistance system (100) according to claims 8 or 9, wherein the control unit (104) comprises a logic unit (1 14) configured to determine the vehicle speed of the second vehicle (2) and to establish the control signal to be transmitted to the active cruise control system of said second vehicle (2).

1 1 . The driver assistance system (100) according to any one of the preceding claims, wherein the at least one sensor is arranged to detect said second vehicle forwardly, laterally and/or rearwardly of said first vehicle (1 ).

12. A method for controlling an active cruise control system of a first vehicle, said active cruise control being at least operable in a minimum speed limit operating state; the method comprising the steps of:

- detecting (S1 ) a second vehicle (2) in the vicinity of said first vehicle (1 );

- determining (S2) that said first vehicle (1 ) is overtaking said second vehicle (2); and

- controlling (S3) the active cruise control system (108) of the first vehicle (1 ) to be operated in the minimum speed limit operating state.

13. A computer program comprising code means for performing the steps of claim 12 when the program is run on a computer.

14. A computer readable medium carrying the computer program according to claim 13.

15. A vehicle (1 ) comprising a driver assistance system (100) according to any one of claim 1 - 1 1 .