Navigation system and navigation method

Field of the Invention

0001The invention relates to a navigation system and a navigation method for predetermining a driving route of a vehicle and outputting driving indications to a driver of the vehicle according to the predetermined route.

Related Art

0002Navigation systems have become known in the art as computer-based systems which are mounted in a vehicle for calculating a driving route to a final destination input by the driver and outputting driving indications for guiding the driver to the desired destination. The driving indications include announcements and instructions relating to forthcoming driving maneuvers which have to be performed by the driver in order to follow the calculated driving route. They are determined by the navigation system in dependence on the calculated driving route (i.e. crossings, junctions and the like) and output to the driver, typically by an audio-response unit for voice output of the navigation system.

0003More specifically, once a driving route to a final destination has been calculated, the navigation system determines the driving maneuvers which have to be performed by the driver at different points (locations) along the route for following the calculated driving route from the starting point to the final destination.

0004Subsequently, when the vehicle, which is traveling along the calculated driving route, approaches the point of the route where a driving maneuver has to be performed, different driving indications relating to the forthcoming driving maneuver are output sequentially to the driver in dependence on the distance to the respective point of the route.

0005As to the content of such driving indications, they may comprise different announcements of the forthcoming maneuver. For example, at first, a general announcement such as "turn off to the right coming soon" at a rather long distance of 400 - 700m may be output, followed by an advance announcement of the imminent maneuver including the distance to the maneuver, such as "turn off to the right after 100 meters", and, finally, in the immediate vicinity of the point of the maneuver, the instruction to perform the driving maneuver such as "now turn off to the right".

0006However, these different announcements output sequentially by the navigation system may be confusing for the driver, in particular if she/he is not familiar with the use of a navigation system. Furthermore, it happens that the indications given by speech output via the audio response unit are missed or misinterpreted by the driver. As a result, it occurs that the driver does not comply with the instructions output by the navigation system, what - in the worst case - may lead to a significant deviation between the position of the vehicle and the calculated route which should be followed by the driver, i.e., to wrong-way-driving.

0007In such a case, if the vehicle leaves the calculated driving route and wrong-way-driving, i.e., a predetermined significant positional deviation between the set position of the vehicle according to the predetermined driving route and the actual position of the vehicle, is determined by the navigation system by comparison of the actual position of the vehicle and the calculated driving route, a modified driving route is calculated by the navigation system. As an example, EP 0 833 291 B1 describes details relating to a method for "re-searching" the driving route when the vehicle is out of the calculated route. Such a method may include a search for an entire new route to the final destination from the current position of the vehicle, or, alternatively, the calculation of an additional route for returning to the original driving route calculated previously.

0008In both cases, the driver is provided with additional driving indications as to the additional maneuvers that have to be performed according to the newly calculated modified driving route. Nevertheless, in any case a modified driving route means a detour as compared to the original route what, of course, should be avoided.

Summary of the invention

0009An object of the invention is to overcome the above-mentioned problems and to provide a navigation system and a navigation method capable to provide improved driving indications which make it easier for the driver to follow the calculated route and which avoid that the driver ignores the driving indications.

0010The above objects are accomplished by a navigation system according to claim 1 and a navigation method according to claim 17. The dependent claims are directed to preferred embodiments and further developments of the invention.

0011The navigation system according to the invention comprises means for determining a driving route of the vehicle, means for determining a position of a vehicle, , means for determining a driving maneuver in accordance with the determined route, means for outputting indications relating to the determined driving maneuver to a driver of the vehicle, and means for alerting the driver to potential wrong-way-driving including means for detecting a potential wrong-way-driving situation and means for outputting an indication relating to the potential wrong-way-driving situation to the driver.

0012The invention also provides a navigation method for guiding a driver of a vehicle comprising the steps of determining a driving route of vehicle, determining a position of a vehicle, , determining a driving maneuver in accordance with the determined driving route, outputting indications relating to the determined driving maneuver to the driver, and alerting the driver to potential wrong-way-driving by the steps of detecting a potential wrong-way-driving situation and outputting an indication as to the potential wrong-way-driving situation to the driver, if a potential wrong-way-driving has been detected.

Detailed description of the invention

0013According to the invention, a potential wrong-way-driving of the driver is detected by the navigation system and a respective indication is output to the driver as an alert message. "Potential" wrong-way-driving in the sense of the invention has to be understood as a situation occurring prior to the above mentioned calculation of a modified driving route, i.e., a situation where the driver is still staying on the (pre)determined driving route. Accordingly, when the warning is output by the navigation system, the driver is still in the position to follow the originally determined driving route and to comply with the instructions output by the navigation system so that exclusively the driving maneuver(s) according to the originally calculated driving route have to be performed for reaching the final destination, i.e., without any additional turn off or turn back maneuvers which would be necessary according to a modified or a new driving route.

0014As a result of alerting the driver to potential wrong-way-driving, the guidance of the driver by the navigation system according to the calculated route is significantly improved, because, after the driver has become aware of potential wrong-way-driving, she/he may take steps for avoiding wrong-way-driving in order to keep to the announced maneuvers according to the originally determined driving route, thereby staying on the calculated route.

0015Furthermore, since the driver is alerted early to potential wrong-way driving, namely already at a point of the route which is still comparatively far distant from the point of the route where the maneuver has to be performed, it is easier for the driver to initiate countermeasures and to correct her/his driving behavior as compared to later stages of the drive. This resides from the fact that the distance to the imminent maneuver is still comparatively large so that the time period available for initiating countermeasures and correcting the driving behavior is comparatively longer.

0016Moreover, in many cases the traffic situation near the spot or the location where the maneuver has to be performed is more difficult for complying with the driving instructions output by the navigation system as compared to earlier stages of drive. At the time of the announcement of a turning maneuver, for example, the driver might be standing in a lane where a line of cars are standing from which it might be difficult to get into another lane for performing the turning maneuver. In such a case, due to an indication of the risk of wrong-way-driving such as a repetition of the forthcoming driving maneuver output by the navigation system well before the point of the road where the turning maneuver has to be performed, the driver's attention is heightened and focussed on the forthcoming maneuver.

0017It is a further advantage of the invention to be capable to compensate for deficiencies of the database of map data used for navigation. For example, it occurs that the map data of the database does not reflect the precise point of the road where the driver should get into a certain lane in order to be prepared for a forthcoming turning maneuver, for example. In such a case it may occur that at the time of the announcement of the maneuver, the driver might already stand in a wrong lane from which it might be - not only difficult - but prohibited by traffic regulations to get into the correct line for performing the turning maneuver, similarly to the situation described above. Situations like that can be reliably prevented by the navigation system and the method according to the invention, whereby routing is significantly improved.

0018For determining the driving route, the navigation system according to the invention may comprise means for calculating the driving route in accordance with an information input by the driver, for example, a final destination. The information input by the driver may also relate to a route section or a point which shall be included or excluded in the resulting driving route, for example, for defining a driving route for transportation of dangerous media such as an ignitable liquid or gas, or a particular sightseeing route, city tour and the like. In particular in the case of transportation of dangerous media it is extremely important to ensure that the vehicle will not leave the predetermined driving route.

0019It goes without saying that the driving route may also be stored in the storage device of the navigation system or on a server to which the navigation system may have access by use of a telematic device for selection of a driving route. Alternatively, the driving route may be defined completely by user input without any calculation by the navigation system. Preferably, the means for detecting a potential wrong-way-driving comprises means for detecting at least one value of at least one parameter relating to an operation state of the vehicle, means for determining, in dependence on the predetermined driving route of the vehicle, at least one set value of the parameter(s) relating to an operation state of the vehicle, means for comparing the detected value(s) of the parameter(s) and the determined set value(s) of the parameter(s) and means for judging the result of the comparison for detecting a potential wrong-way-driving situation on the basis of the result of the comparison.

0020The set value(s) of parameter(s), which is/are determined by means for determining at least one set value of said parameter(s) relating to the operation state of the vehicle in dependence on the predetermined driving route of the vehicle, may be a value indicating potential wrong-way-driving or a value indicating right-way-driving.

0021In case the set value(s) define(s) right-way-driving, "potential wrong-way-driving" in the sense of the invention has to be understood as a deviation of the actual value(s) of parameter(s) relating to the operation state of the vehicle and the determined set value(s) of the parameter(s) or the respective ranges thereof. A predetermined amount of deviation may be defined, for example 30 %. Of course, the extent of deviation may strongly depend on the kind of the respective parameter and the respective traffic situation (speed limit etc.) where the maneuver has to be performed and may vary from one situation to another.

0022In case the set value(s) define(s) wrong-way-driving, "potential wrong-way-driving" in the sense of the invention occurs if the actual value of a parameter relating to the operation state of the vehicle reaches the determined set value.

0023The definition of a set value which indicates potential wrong-way-driving or a value which indicates right-way-driving aims in facilitating the processing of the large amount of data what is required for detection of potential wrong-way-driving.

0024Preferably, the set value(s) of the parameter(s) are only determined in the vicinity (i.e., within a predetermined distance) of a location of the route where there is a possibility to leave the route by taking a wrong road which does not belong to the predetermined driving route. For this purpose, the means for alerting the driver to potential wrong-way-driving contains means for determining a location of the route where it is possible to leave the route, such as junctions, crossings and the like, i.e., spots where wrong-way-driving may occur. Thereby, checking for potential wrong-way-driving can be restricted to route sections where there is an actual risk for wrong-way-driving, so that the amount of data processing necessary for potential-wrong-way-driving can be significantly reduced.

0025A parameter relating to an operation state of the vehicle in the sense of the invention may be a position of a vehicle, a time period, an advancing direction of a vehicle, a position of a driving direction indicator control, an acceleration or a deceleration of a vehicle, a vehicle speed, a rotational speed of a vehicle and the like. The position of the vehicle may be a relative position such as a distance to a predetermined location of the route or an absolute position, i.e., a geographical position.

0026Actual values of the parameter(s) relating to an operation state of the vehicle are detected by suitable sensors known in the art which are connected to the navigation unit. The sensors may continuously detect the current values of the parameter(s) relating to an operation state of the vehicle. For example, for determining an advancing direction of the vehicle a gyroscope or a steering wheel sensor may be applied and the position of the vehicle may be determined by a GPS-system, GSSN-system or the like. A relative position of the vehicle, such as a distance to a predetermined location of the route may be determined based on the absolute (geographical) position of the vehicle and map data stored in a storage device of the navigation system.

0027It has to be noticed that a positional deviation between the actual position of the vehicle and the set position of the vehicle according to the predetermined driving route does not necessarily indicate wrong-way-driving but, in dependence on the amount of deviation, may still fall under the coverage of "potential" wrong-way-driving. For example, the positional deviation that occurs if a driver gets into the left lane, for example, near to a point of the road where the driver should turn off to the right side may be detected as potential wrong-way-driving. Preferably, staying on the predetermined driving route in the sense of the present invention may be defined as staying on the road (street) of the respective section of the originally predetermined driving route, including all driving lanes of the respective driving directions.

0028It should be understood that the respective parameter(s) of the actual value(s) and the parameter(s) of the set value(s) correspond to each other. The set value(s) of the parameter(s) may be time dependent, e.g. maintaining a vehicle speed (parameter) of lower than 50 km/h (value) for more than 30 seconds.

0029The set value(s) of the parameter(s) relating to the operation state may be derived from a combination of two or more of the above mentioned parameters. Without listing all possible combinations, in dependence on the respective traffic situation, any of them may be utilized. Among that large variety, in particular a combination of the position of the vehicle and one or more parameters from the group vehicle speed, direction indicator control, advancing direction of the vehicle, and the time period during which these parameter are within at least one predetermined range of values is preferable for detection of potential wrong-way-driving. More preferably, the set value of the parameter relating to an operation state of the vehicle may be a relative position of the vehicle which is defined by a distance to a location of the road where the driving maneuver has to be performed and, additionally, by a distance of the position of the vehicle to the predetermined driving route. Such a definition of set values (here: two distances) of the respective parameter (here: relative position) may be helpful to increase the accuracy of detection of potential wrong-way-driving. The set values of the two distances may also be set in dependence on each other. For example, the distance to the predetermined driving route required for the detection of potential wrong-way-driving may decrease with the decrease of the distance to the point of the road where the next turning off maneuver has to be performed.

0030Of course, the means for determining at least one set value of the parameter(s) relating to the operation state of the vehicle and the means for detecting at least one actual value of these parameters may be adapted to these preferred configurations by comprising the respective means for determining the set value(s) of the parameter(s), such as the above two distances and the actual values thereof during the operation of the moving vehicle, respectively.

0031The set value(s) of said parameter(s) is/are determined in dependence on the predetermined driving route. Since for following the predetermined driving route different operation states of the vehicle in terms of parameter values of velocity, advancing direction and the like are required at different locations of the route, the at least one set value of parameter(s) is determined in dependence on the circumstances at individual locations of the respective driving route or driving route section. More in detail, the set values may be determined in dependence on the kind of the driving maneuver, the traffic regulations along the respective route section and/or the course of the road along the driving route section. As a simple example for illustration, a turning off maneuver at an turning off angle of more than 90° requires a lower vehicle speed than a turning off angle of 30°.

0032By using, for example, the position of the direction indicator control as a parameter relating to the operation state of the vehicle for determining a potential wrong-way-driving according to the invention, the occurrence of a positional deviation between the actual position of the vehicle and the predetermined driving route is not necessarily required for detecting potential wrong-way-driving. A relating example may be a predetermined route going straight ahead, on the one hand, and setting of the direction indicator control to a certain position, e.g., for turning left, by the driver and maintaining it in this position for longer than a predetermined time period without changing the driving direction. In such a case, the intention of the driver to turn off to the left is detected by the navigation system and a potential wrong-way-driving is concluded, i.e. detected. A further example of the determination of a potential wrong-way-driving may be an excessive vehicle speed determined at a position near the location of a turning off maneuver according to the predetermined route.

0033In other words, the navigation system according to the invention is capable to alert the driver to potential wrong-way-driving while the vehicle is still staying on the (pre)determined driving route.

0034According to a preferred embodiment of the invention, the means for outputting an indication relating to potential wrong-way-driving to the driver comprises means for determination the content of indication output to said driver.

0035The means for determining the content of indication output to the driver may comprise means for determining output information relating to the correct driving route, i.e. the originally predetermined driving route. Thereby, the driver's attention is drawn to the risk of wrong-way-driving, so that she/he can easily conclude what has to be done for staying on the correct route. For more complicated situations, where it is rather difficult for the driver to infer what to do, the means for determination the content of indication output to said driver may comprise means for determining driving recommendations for avoiding wrong-way-driving. That is, in dependence on the situation of potential wrong-way-driving, instructions may be output to the driver on how to stay on the predetermined driving route.

0036The output means for outputting driving indications to the driver may comprise an audio-response unit in combination with loudspeakers and/or a display of the navigation system.

0037Further features and advantages of the navigation system and the navigation method according to the invention become apparent from the following description of preferred embodiments with reference to the accompanying drawings in which <dl id="dl0001"><dt>Fig. 1</dt><dd>is a schematic functional block diagram of an embodiment of a navigation system for altering the driver to potential wrong way driving;</dd><dt>Fig. 2</dt><dd>is a schematic functional block diagram of the alert unit of the navigation system shown in Fig. 1;</dd><dt>Fig. 3</dt><dd>is a schematic illustration of a situation of potential wrong-way-driving, and</dd><dt>Fig 4</dt><dd>shows a flow chart of an embodiment of a navigation method according to the invention for alerting the driver to potential wrong-way-driving in the situation illustrated in Fig. 3.</dd></dl>

0038The first embodiment of a navigation system 100 according to the invention shown in Fig. 1 comprises a navigation unit 101, a position determination unit 102 including a GPS-unit 121 and a unit 122 for determining a relative position of a vehicle, an operation panel 103, a display 104, a set of loudspeakers 105 and a storage device 106. An audio-response unit (ARU) 110 including a text-to-speech (TTS) synthesizer 111 and a speech recognition unit 112 for voice command purposes are connected to the navigation unit 101. The input/output equipment of the navigation system 100 according to the present embodiment is constituted of the operation panel 103, the display 104, the audio-response unit (ARU) 110 including the text-to-speech (TTS) synthesizer 111 and the speech recognition unit 112. However, the configuration of the input/output equipment is not limited thereto and any kind of human machine interface known in the art for transferring data between user and system may be provided in dependence on the demands of the individual user. For example, the display 104 may be constituted of a touch screen and the operation panel 103 may comprise a joy stick and/or a microphone not shown in Fig. 1.

0039The navigation unit 101 comprises a driving route calculating unit 107, a driving maneuver determination unit 108, and an alert unit 109 which is described in more detail below with reference to Fig. 2.

0040The storage device 106 is a mass storage medium for storing map data constituted of a CD-ROM and a CD-ROM drive, for example, and is connected to the navigation unit 101 and the position determination unit 102. The navigation system 100 according to the invention further comprises as a plurality of sensors including a steering wheel sensor 113, a rotational speed counter 115, wheel sensors 116, ABS sensors 117, a gyroscope 118, and a sensor 119 for determining the position of the driving direction indicator control as well as a timer 120 which are connected to the navigation unit 101. A unit 114 for providing a tachometer signal is also connected to the navigation unit 101.

0041The alert unit 109 of the navigation unit 101 of the navigation system 100 shown in Fig. 1 is illustrated in more detail in Fig. 2. The alert unit 109 comprises a potential wrong-way-driving detection unit 201, an indication content determination unit 202 and a unit 208 for determining a location of the route where it is possible to leave the route. The unit 208 determines locations of the route where it is possible to leave the route on the basis of the calculated driving route as determined by the driving route calculation unit 107 and the map data provided by the storage device 106.

0042The potential wrong-way-driving detection unit 201 includes a set value determination unit 203 for the determination of set value(s) of a parameter(s) relating to the operation state of the vehicle. The set value determination unit 203 comprises a plurality of subunits for determining at least one set value of at least one parameter or a combination thereof from the group: geographical position of a vehicle (unit 210), relative position of a vehicle (unit 211), advancing direction of a vehicle (unit 212), position of a driving direction indicator control (unit 213), acceleration/deceleration of a vehicle (unit 214), vehicle speed (unit 215), rotational speed of a vehicle (unit 216) and a time period during which at least one value of said parameter(s) is within a predetermined value range (unit 217), which - for the sake of simplicity - are illustrated in Fig. 2 as an unitary component with reference numerals 210-217.

0043The potential wrong-way-driving detection unit 201 further comprises a comparator 204 for comparing the set value(s) determined by the set value determination unit 203 and the actual values determined or detected by the position determination unit 102 including units 121 and 122 and/or the sensors 113-120 including unit 114. A judging unit 205 is provided for judging the result of the comparison performed by the comparator 204.

0044The indication content determination unit 202 comprises a unit 206 for determining output information relating to the correct driving route and a unit 207 for determining driving recommendations for staying on the correct driving route (i.e., the originally calculated driving route) in dependence on the detected potential wrong-way-driving situation.

0045A situation of potential wrong-way-driving is illustrated schematically in Fig. 3. A vehicle 300 is moving along a three-lane road 301 comprising lanes 302-304. More specifically, the vehicle 300 is moving along traffic lane 302 at point A of road 301 when the navigation system 100 of the vehicle 300 outputs an advance announcement of a maneuver "right-hand turn after 400 meters" in accordance with the calculated driving route 305 indicated as a dotted line in Fig. 3. The driver who heard the advance announcement notices the crossing 306 lying ahead and misinterprets the advance announcement output by the navigation system as to be related to crossing 306 instead of crossing 307. As a result, the driver operates the lever of the driving indicator control for moving to the right, reduces the vehicle speed, and switches from lane 302 to lane 304 at point C of the road 301.

0046Accordingly, since in the present situation the driver misunderstood the advance announcement output by the navigation system at point C of road 301, there is a risk that the driver turns off to the right side at crossing 306 instead of crossing 307 according to the calculated driving route 305. In other words, at point C of road 301 a situation of potential wrong-way-driving in the sense of the invention occurs.

0047Such a situation of potential wrong-way-driving can be recognized and wrong-way-driving can be avoided by the use of a navigation system 1 according to the invention as shown in Fig. 1, for example.

0048In the following an embodiment of a navigation method according to the invention for guiding a driver of vehicle 300, if a potential wrong-way-driving situation as shown in Fig. 3 happens, will be described with reference to Fig. 4.

0049In step 400, after starting the engine of the vehicle, the position of the vehicle is determined by the position determination unit 102 of the navigation system 100. In the following the determination of the geographical position is continued periodically during the drive by the position determination unit 102. In step 401, after an input of a desired destination by the driver via the operation panel 103, a driving route to the final destination is calculated by the driving route calculation unit 107. The resulting driving route from the starting point to the final destination as input by the driver includes a route section constituted of sections of roads 301 and 308 shown in Fig. 3.

0050While in the present embodiment the driving route has been predetermined by calculation in accordance with an input information (final destination), the driving route may also be predetermined by selection and download from an external server via the internet, for example.

0051For following the calculated route, a plurality of driving maneuvers is determined in step 402 by the driving maneuver determination unit 108. Among these maneuvers, there is a right-hand turn off maneuver at crossing 307 in order to reach road 308 coming from road 301 as shown in Fig. 3.

0052During the drive the distance to crossing 307 where the turning off maneuver to the right has to be performed is continuously determined in step 403 by the unit 122 for determining a relative position of the vehicle by comparing the actual position of the vehicle 306 as determined by the GPS system 121 and the location of crossing 307 based on map data of the storage device 106.

0053In step 404, when reaching a predetermined distance to the location of the maneuver such as 200 m to crossing 37, the advance announcement "turn off to the right after 200 meters" is output to the driver by the audio response unit 110 via loudspeakers 105. Furthermore, in step 405 a set value of parameters relating the operation state of the vehicle is determined by the set value determination unit 203. In the present case, the set value of the parameters represents a value which indicates potential wrong-way-driving and is constituted of a combination of the parameters position of the vehicle, vehicle speed, position of the driving direction indicator control and time. The specific values of these parameters are set as follows: <dl id="dl0002" compact="compact"><dt>Condition A:</dt><dd>a distance of the vehicle to crossing 306 of less than 300 meters,</dd><dt>Condition B:</dt><dd>a vehicle speed lower than 40 km/h for more than 5 seconds</dd><dt>Condition C:</dt><dd>a downward position of the driving direction indicator control maintained for more than 5 seconds.</dd></dl>

0054In the present embodiment, since the position of the vehicle 300 is continuously determined by the position determination unit 102 of the navigation system 100, in the following merely the position of the driving direction indicator control is determined by sensor 119 in step 406. If the driving direction indicator control is set to a downward position indicating the willingness of the driver to perform a turn off maneuver to the right, in step 407 the timer 120 is started and the time period of the driving direction indicator control being set to the downward position is monitored.

0055As mentioned above, the set value of parameters for defining a potential wrong-way-driving in the present embodiment is defined by the combination of the conditions A + B + C. Accordingly, in step 408 the actual position of the vehicle as determined in step 400 by the position determination unit 102 of the navigation system 1 is compared with the set position according to condition A; in step 409 the speed of the vehicle obtained from the tachometer signal unit 114 is compared with the set value as specified by condition B and in step 410 the position of the driving direction indicator control as determined by sensor 119 in step 406 is compared with the set value as specified by condition C by means of the comparator 204.

0056If no potential wrong-way-driving is detected in step 411 by the judging unit 205, in step 412 an advance announcement as to the approaching crossing 307 is output when the vehicle which is following the calculated driving route reaches a predetermined distance to the point of the route where the maneuver has to be performed, i.e., the crossing 307, what is determined by the relative position detection unit 122. If, in step 411, a potential wrong-way-driving is detected, in step 413 the content of indication relating to potential wrong-way-driving is determined by the indication content determination unit 202. That is, according to the example of the present embodiment, the current distance to the driving maneuver (here: 200 m) and the kind of driving maneuver (here: turn off to the right) are determined as the information to be output to the driver by the unit 206 for determining output information relating to the correct driving route. Furthermore, in step 414 a driving recommendation for avoiding wrong-way-driving is determined by the unit 207 for determining driving recommendations for staying on the correct driving route. In the exemplary situation of the present embodiment, from the location of crossing 307, the position of the vehicle and the course of the road between the location of the crossing 307 and the position of the vehicle 300 at point C of road 301, as illustrated in Fig. 3, based on the map data stored in the storage device 106, it is determined that going straight ahead is the appropriate driving behavior for reaching crossing 307 from the current position of the vehicle 300 at point C.

0057Accordingly, the following warning is output in step 415 to the driver: "Attention; possibly wrong-way-driving; Keep going straight ahead; turn off to the right after 200 m".

0058Further embodiments relating to methods according to the invention are described in the following. The embodiments 2 to 5 are based on the above first embodiment described with reference to Figs. 3 and 4 but comprising the following modifications:

0059According to a second embodiment, instead of the detection of potential wrong-way-driving in dependence on the combination of set values according to the above conditions A + B + C, wrong-way-driving may also be detected by a combination of set values A + B or A + C.

0060According to a third embodiment, instead of calculating a set value being an indicative value of said parameter(s) relating to an operating state of the vehicle for leaving route, a value of said parameter(s) relating to an operating state of the vehicle which indicates that the vehicle is staying on the route is calculated as a set value. Specifically, instead of condition B a speed range of Vset > 40 km/h is determined as a set value (condition D) based on the speed limit of 70 km/h on road 301. If the vehicle speed falls below 40 km/h, potential wrong-way-driving is concluded since the reduction of speed is interpreted as an indication that the driver intends to turn off at crossing 306.

0061As becomes apparent from the above embodiments the determination of set values strongly depends on the traffic regulations at the respective road sections or locations.

0062For example, according to a fourth embodiment, if a traffic signal is installed at the crossing 306 the above conditions A and D are not sufficient because it has to be expected that the vehicle has to stop at the traffic light what according to the conditions A+D or A+C would lead to a detection of wrong-way driving, erroneously. In order to distinguish between waiting at the traffic light and potential wrong-way-driving, in such a case a combination of conditions A+B+C is necessarily required.

0063A further important factor for the determination of the set value(s) is the driving route and the circumstances at the point of the road where the maneuver has to be performed. For example, according to a fifth embodiment of the invention, potential wrong-way-driving is to be detected in the area of crossing 307 where the driver has to get on route 308 for following the calculated driving route, as shown in Fig.3.

0064Accordingly, the set values of parameters indicating potential wrong-way-driving may be defined as follows: <dl id="dl0003" compact="compact"><dt>Condition E:</dt><dd>a distance of the vehicle to crossing 307 of less than 150 meters,</dd><dt>Condition F:</dt><dd>a vehicle speed higher than 70 km/h</dd></dl>

0065That is, if the vehicle exceeds a speed limit of 70 Km/h within a comparatively small distance of 150 meters to crossing 307 this is interpreted as an indication that the driver will not turn off to the right at crossing 37 but intends to drive straight on along road 301 what would lead to wrong way driving.

0066It goes without saying that the embodiments 1-5 as described above may be combined in any manner suitable to put the invention into practice, according to the knowledge of a person skilled in the art in dependence on the particular demands of the respective application.