AU2016202560B2

AU2016202560B2 - Method for determining the speed of motor vehicles with autonomous plausibility check

Info

Publication number: AU2016202560B2
Application number: AU2016202560A
Authority: AU
Inventors: Heiko Frohn
Original assignee: Vitronic Dr Ing Stein Bildverarbeitungssysteme GmbH
Current assignee: Vitronic Dr Ing Stein Bildverarbeitungssysteme GmbH
Priority date: 2015-05-21
Filing date: 2016-04-21
Publication date: 2017-08-31
Anticipated expiration: 2036-04-21
Also published as: EP3096305A1; EP3096305B1; AU2016202560A1; DK3096305T3

Abstract

Abstract The invention relates to a method for determining the speed of vehicles (1) on a roadway (2), in which a first measuring system and a second measuring system are provided, the first measuring system is provided with a sensor device (5) covering a detection area (7) and a first time measuring device (8), wherein the first measuring system measures at several points of time the distance (D) of a vehicle (1) moving within the detection area (7) and determines by means of the distance (D), changing over time, a driving speed (vpe) of the vehicle (1) and the second measuring system checks the determined driving speed (vpe), characterised in that the second measuring system is provided with a second time measuring device (9) being independent of the first time measuring device (8), wherein the second measuring system monitors by means of the sensor device (5) a virtual entry line (11) of a roadway section (10) situated within the detection area (7) and records by means of the second time measuring device (9) an entry point of time (ti), at which the sensor device (5) detects an object point at the entry line (11), wherein the second measuring system checks at least at a later check point of time (t2 ) by means of the sensor device (5), whether an object point is within a defined section window (2xi) around a virtual exit line (12) of the roadway section (10). Fig. 1 --- -- ~- -- 4 Fig. 2 f (-----------------------------4-------

Description

1001439428 2016202560 21 Apr 2016

METHOD FOR DETERMNG THE SPEED OF MOTOR VEHICLES WITH AUTONOMOUS PLAUSIBILITY CHECK

The present invention relates to a method for determining the speed of vehicles on a roadway, in which a first measuring system and a second measuring system are provided and the first measuring system is provided with a sensor device covering a detection area and a first time measuring device, wherein the first measuring system measures at several points of time the distance of a vehicle moving within the detection area and determines by means of the distance, changing over time, a driving speed of the vehicle, and in which the second measuring system checks the determined driving speed.

To determine the speed of vehicles, a number of known technologies is available. For example, optical speed measuring systems with a LiDAR-sensor device (abbreviated from: Light Detection and Ranging) can be used, which measure within a detection area of the sensor several times the distance to vehicles by means of time of flight method (TOF). The principle of the time of flight measuring is that a laser diode of the sensor device produces short laser pulses, which are projected onto the vehicle. The light reflected by the vehicle is recorded by a sensor element. Via the time of flight of the laser pulses to the vehicle and back, the distance is derived, wherein the speed of the respective vehicle is determined by the distance, changing over time, and is respectively calculated. Such LiDAR-systems are for example positioned stationary or mobile on traffic islands, grass strips or on flyovers, to monitor roadways of a road. Besides LiDAR-systems, however, also other technologies, for example radar systems, which calculate by means of the Doppler Effect the speed of the vehicle from the measured frequency changing between the sent and reflected signal, or piezo cables or induction loops, embedded in the road surface, can be used for measuring the speed. If the known speed measuring systems detect an excess of a maximum speed limit allowed on the monitored roadway, commonly photos and/or videos of the vehicles, travelling too fast, are recorded, to be able to start a penalisation of the speed violation. l 1001885928 2016202560 10 Aug 2017

From US 8,712,105 B2 a method for determining the speed of vehicles on a roadway is known. The speed of the vehicle is measured by means of an optical sensor device, which is provided with a LiDAR-sensor. To be able to exclude measuring errors or measuring inaccuracies of the optical sensor device, the measured speed of a possibly to fast driving vehicle is checked by a second speed measuring method. For this, two photos of the to be checked vehicle are recorded chronologically one after the other. These photos are transmitted to a central office, in which the photos are manually evaluated. To be able to check the speed by means of the photos, in the chronologically first photo a point is selected on the to be checked vehicle. Then, in a software aided manner a line extending through the selected point is shown graphically transversally to the roadway on both photos. Furthermore, two further lines, extending transversally to the roadway are graphically added on the second photo. The second line, when seen in driving direction, represents a path, which the to be checked vehicle would have reached when maintaining the allowed speed limit. The third line represents in contrast the path, which the vehicle reaches, when the speed measured by the LiDAR-sensor would have been maintained. Then, the photos are manually evaluated. If the second photo shows, that the vehicle has reached the third line, an operator of the central office confirms, that the speed measured by the LiDAR-sensor of the too fast driving vehicle was correctly measured. When the to be checked vehicle remains behind the second line, this vehicle has obviously not exceeded the allowed speed and the speed measurement by means of the LiDAR-sensor evidently led to a measuring error.

It is seen as disadvantageous, that the data, especially the photos of all passing vehicles, which supposedly are driving too fast, are transmitted to a central office. By means of transmission of sensitive data to the central office the risk exists that a third party could tap the data. Furthermore, the method is because of the manual check time consuming and labour intensive.

Reference to any prior art in the specification is not an acknowledgment or suggestion that this prior art forms part of the common general knowledge in any jurisdiction or that this prior art could reasonably be expected to be combined with other pieces of prior art by a skilled person in the art. 2 1001885928 2016202560 10 Aug 2017

Therefore, it is the object of the present invention to provide a simple and/or, secure and/or self-checking method for determining the speed of vehicles.

According to the invention, there is provided a method for determining the speed of vehicles on a roadway, in which a first measuring system and a second measuring system are provided, the first measuring system is provided with a sensor device covering a detection area and a first time measuring device, wherein the first measuring system measures at several points of time the distance of a vehicle moving within the detection area and determines by means of the distance, changing over time, a driving speed of the vehicle and the second measuring system checks the determined driving speed wherein the second measuring system is provided with a second time measuring device being independent of the first time measuring device, wherein the second measuring system monitors by means of the sensor device of the first measuring device a virtual entry line of a roadway section situated within the detection area and records by means of the second time measuring device an entry point of time, at which the sensor device of the first measuring device detects an object point at the entry line, wherein the second measuring system checks at least at a later check point of time by means of the sensor device of the first measuring device, whether an object point is within a defined section window around a virtual exit line of the roadway section.

Thus, the invention is based on the consideration to provide a method, in which besides the determination of the driving speed of a vehicle also an automated, respectively autonomous plausibility check is carried out. In other words, as part of a primary measuring method, the driving speed is determined by means of a first measuring system, preferably of each vehicle driving on the roadway through the detection area of the sensor device, and as part of a secondary method of proof, it is checked by means of the second measuring system, whether the determined driving speed of the individual vehicles could be plausible. Because of the self-checking method for determining the speed, according to the invention, the judicial usability of the determined driving speeds is given.

For this, the invention suggests, that the sensor device of the first measuring system monitors the roadway, respectively the roadways, which can comprise also the roadways of a road for both driving directions. When a vehicle moves within the 3 1001885928 2016202560 10 Aug 2017 detection area of the sensor device, the first measuring system measures as part of the primary measuring method at several points of time, i.e. at least at two different points of time, by means of the sensor device the distance of the sensor device to the respective vehicle. For each distance measurement, a time value, detected by the first time measuring device, is deposited as a time stamp for the measured distance value in order to determine or calculate by means of the distance changing over time the driving speed of the respective vehicle.

According to one Or more embodiments of the invention, the second measuring system checks autonomously, i.e. without manual operation, as part of the second method of proof, whether the driving speed of the respective vehicle, which has been determined with the primary measuring method, is plausible. For this, the second measuring system uses the sensor device of the first measuring system. However, for the secondary method of proof a second time measuring device, which is independent from the first time measuring device, is used, in order to be able to exclude measuring errors or measuring inaccuracies caused by the first time measuring device. To start the secondary method of proof, a virtual entry line of a roadway section, situated within the detection area of the sensor device, is monitored by means the sensor device of the first measuring system. As soon as an object point, which does not have to be an object point of the vehicle, which determined driving speed is to be checked for plausibility, but generally can be an object point of any object moving on the roadway, crosses the entry line, the second measuring system records an entry point of time by means of the second time measuring device. Generally, the roadway section can have a fixed, predetermined length or a variable length, especially in dependency of the determined driving speed. The virtual entiy line, limiting the roadway section, can be measured off locally on the roadway during installation of the measuring systems and can be taught software based via the sensor device. Thus, the virtual entry line corresponds to real positions on the roadway, wherein the entry line itself cannot be seen as markings on the roadway. Especially, when the roadway section has a fixed predetermined length, also the virtual exit line can be taught software based in analogous manner. Both virtual lines may extend parallel to each other and extend transversally across the to be monitored roadway. The distance between the two virtual lines corresponds to the length of the roadway section, so that the way section 4 1001885928 2016202560 10 Aug 2017 is bounded, when seen in driving direction, at the entry side by the entry line and at the exit side by the exit line.

As soon as the second measuring system has recorded the entry point of time, it checks at least at a later check point of time by means of the sensor device, whether an object point or an object point of any object moving on the roadway is within a defined section window around the virtual exit line of the roadway section. To prevent measuring errors, the section window extends preferably only across the to be monitored roadway. The defined section window around the virtual exit line represents a tolerance range, in which the sensor device detects object points, so that object points do not compulsorily have to be right on the exit line at the least at one check point of time, in order to be detected. The size of the section window can particularly be ± 10 % of the length of the roadway section, which can have a fixed predetermined length or a variable length around the virtual exit line, when seen in driving direction. According to the invention, it is thus provided, that the sensor device does not have to continuously monitor the to be checked vehicle during the drive through the detection area, however can, in order to give a statement for plausibility of the determined driving speed. In fact, already two points of time are sufficient, namely the entry point of time and a chronologically later check point of time, to check the plausibility of the driving speed determined by means of the first measuring system.

Preferably, static objects within the detection area are detected and deposited by the sensor device during the local installation of the measuring systems. Thus, the sensor device can differentiate static objects or objects moving next to the roadway from objects moving on the roadway.

However, to be able to predict with sufficient probability that the object point being detected on the entry line is an object point of the to be checked vehicle, the chronological and spatial sequence of the primary measuring method and of the secondary proof method may be synchronised to each other. In particular, the sensor device may monitor the virtual entry line, from a temporal perspective, particularly immediately after the step of measuring the driving speed with the primary measuring method. Furthermore, the virtual entry line, which bounds the roadway section, in driving direction at the entry side, may be arranged within the 5 1001885928 2016202560 10 Aug 2017 detection area of the sensor device such that the to be checked vehicle, particularly immediately after finishing the primary measuring method would pass the entry line. By doing so, a spatial and timely close link, between the to be checked vehicle and the object point crossing the entry line, can be assumed, so that with sufficient probability the detected object point is an object point of the to be Checked vehicle.

According to one or more embodiments of the present invention, a section length of the roadway section may be known by a defined distance of the exit line to the entry line. Based on the known section length and the determined driving speed of the vehicle a predicted time interval may be calculated, which the vehicle would need for passing the roadway section when maintaining the constant determined driving speed. In general, the speed is a quotient of the distance and the time required for it. Here, the driving speed determined by the first measuring device, and the predetermined roadway section , which can be, for example, ten meters, are known so that the time needed for roadway section can be calculated. Here, this is an estimated time interval, as for calculating the time it is assumed that the determined driving speed is constant.

Furthermore, the second measuring system may check at the at least one check point of time, which corresponds to the sum of the entry point of time and the predicted time interval, by means of the sensor device, whether an object point is within the defined section window around the exit line. Thus, based on the detected driving speed and the known section length it is estimated, at which point of time the respective vehicle should be expected to be at the exit line, so that doing so a spatial and timely close link is established to the object being captured at the entry line and moving on the roadway and the object point of the object. Thus, the object point detected in the section window around the exit line at the check point for time belongs with sufficient probability to the moving object detected at the entry line. Because of the preferably spatial and timely adjustment of the primary measuring method with the secondary proof method, it can furthermore be assumed with sufficient probability, that the object point, detected in the section window around the exit line, is an object point of the to be monitored vehicle. In this manner, an efficient and self-checking measurement method is provided, in which the second measuring system does not have to access the sensor device continuously, but only at least at two points of time, namely the entry point of time the sensor device and the at least 6 1001885928 2016202560 10 Aug 2017 one further check point of time, so that the vehicles do not have to be monitored constantly during the drive through the detection area.

According to another embodiment of the present invention a distance of the exit line to the entry line may correspond to a section length of the roadway section, which behaves proportional to the determined driving speed, wherein based on a defined time interval and the determined driving speed of the vehicle the second length may be predicted, which the vehicle would pass when maintaining the determined driving speed within the time interval. In general, the speed is the quotient of the length and

6A 1001439428 2016202560 21 Apr 2016 the time needed for it. Here, the driving speed determined by the first measuring system and the time interval are known, so that the section length, which can be passed under the assumption of a constant driving speed within the predetermined time interval, corresponds to the product of the determined driving speed and the predetermined time interval. In particular, the time interval can have a fixed value, for example one second. Alternatively, the time interval may depend on the determined driving speed, for example in such a manner, that with a determined driving speed of up to 30 km/h the time interval is 1.2 seconds, above 30 km/h up to 50 km/h is 0.72 seconds, above 50 km/h up to 100 km/h is 0.36 seconds, above 100 km/h up to 200 km/h is 0.18 seconds and above 200 km/h is 0.1 seconds. Other as well as more or fewer than the only exemplary mentioned five gradations are also possible.

Furthermore, the second measuring system may check at the at least one check point of time, which corresponds to the sum of the entry point of time and the defined time interval, by means of the sensor device, whether an object point is within the defined section window around the exit line. Because of the section length of the roadway section being depend on the determined driving speed, the second measuring system monitors by means of the sensor device the defined section window around the exit line at the at least one check point of time and detects in this case generally any object point moving on the roadway. Under the assumption that the object point detected at the entry line moves further on the roadway section while maintaining the detected driving speed, a spatial and timely link of the object detected at the entry line or the object point of the object moving on the roadway is established to the object point detected in the section window around the exit line. In this way, the object point detected in the section window around the exit line at the check point of time belongs with sufficient probability to the object being detected at the entry line and moving on the roadway. Because of the preferably spatial and timely adaptation of the primary measuring method with the secondary proof method, furthermore, with sufficient probability it can be assumed that the object point detected in the section window around the exit line is an object point of the to be checked vehicle. In this way, an efficient self-checking measurement method is provided, in which the second measuring system does not have to constantly access, the sensor device, but only at least at two points of time, namely the entry 7 1001439428 2016202560 21 Apr 2016 point of time and the at least one further check point of time, so that the vehicles do not permanently have to be monitored during the drive through the detection area.

Particularly, the determined driving speed of the vehicle may be confirmed by the second measuring system, in particular only then, when an object point is within the defined section window around the virtual exit line at the at least one check point of time. Thus, the secondary proof method, may only then regard the driving speed detected by the first measuring method as plausible, if any object point of an object moving on the roadway has been associated with an entry point of time and at the at least one check point of time, any object point of an object moving on the roadway has been detected in the section window around the exit line. However, the object point being detected at the entry point of time at the entry line and being detected at the at least one check point of time in the section window around the exit line, do not have to be the same object point nor an object point of the to be checked vehicle. When, however, no object point is within the defined section window at the at least one check point of time, this may indicate for example to an measuring error of the driving speed by the first measuring system or to a faulty measurement by the second measuring system, particularly by the second time measuring device, or to an abrupt slowing down of the to be checked vehicle, so that as part of the secondary proof method the determined driving speed is classified as wrong or not provable.

Particularly, the determined driving speed of the vehicle may only checked then by the second measuring system, when the driving speed is larger than a given maximum speed limit on the roadway. This way of checking provides an efficient measuring method for monitoring the speed of vehicles. Only when the primary measuring method reveals that the driving speed of the vehicle is in excess of an allowed speed limit, the secondary proof method is initiated. If then the plausibility check reveals that the driving speed of the vehicle being determined by the first measuring system is plausible, the determined driving speed besides further data, like for example taken photos and/or videos of the provably too fast driving vehicle as well as local time and location information of the measuring systems can be combined to a set of evidence data. If, however, the plausibility check reveals, that the determined driving speed is wrong and/or is not provable, all data concerning the vehicle can be deleted from the measuring systems because of data protection 8 1001439428 2016202560 21 Apr 2016 reasons. Such a deletion can be carried out automatically, as soon as the respective vehicle has left the detection area.

In particular, the sensor device may be provided as an area-wide monitoring or space-monitoring sensor device. Particularly, the sensor device can be provided as an optical sensor device, in particular, a LiDAR-sensor device with a laser transmission unit and a laser receiver unit in order, to measure the distance to the vehicles by means of a time of flight method (TOF). For measuring the distance, the receiver unit is usually arranged directly next to the transmitter unit. To measure the distance to the respective vehicle, a time difference between a transmission time of a laser pulse and an arrival time of the radiation scattered or reflected by the vehicle is determined wherein the time difference is detected by the first measuring system by means of the first time measuring device. For measuring the driving speed of the respective vehicle, this process is repeated at least once, preferably with a high repetition rate, especially 100-times per second. To monitor the detection area in an area-wide manner, the sensor device can comprise a polygon mirror, which deflects the particularly in quick rates pulsed laser beams within the detection area over the roadway. For each sending of a laser beam a time stamp is set by means of the first time measuring device and is stored together with the value of the reflection angle. The sensor device may also be provided with a TOF-camera. TOF-cameras are spatial monitoring 3D-camera systems, which measure distances with the time of flight method also. The detection area is illuminated by means of light pulses and the camera measures for each image point the time of flight, which the light requires up to the vehicle and back again. Alternatively, the sensor device may be provided as a radar sensor device with a radar transmitter unit and a radar receiver unit in order to measure the distance to the vehicles by means of a time of flight method.

In particular, the detection area of the sensor device when seen in driving direction may extend over a distance of 75 meters when seen in driving direction, wherein the driving speed of the vehicles may be measured in a distance of particularly 75 up to 40 meters to the sensor device when seen in driving direction. In particular, the driving speed of the respective vehicle is determined several times within the detection area by the first measuring system and an averaged value is calculated for the respective vehicle from the determined driving speed values. In particular the plausibility of the averaged driving speed is checked by means of the secondary 9 1001439428 2016202560 21 Apr 2016 proof method. The roadway section necessary for the plausibility check is, when seen in driving direction, preferably 10 meters long, wherein, when seen in driving direction, the virtual entry line may extend particularly 40 meters and the virtual exit line may extend particularly 30 meters distanced from the sensor device transversal ly across the roadway.

Furthermore, both measuring systems can form one measuring device, particularly autarkic, accommodated, in a housing, particularly a stationary constructed columnlike housing or in a mobile, particularly transportable, box-like housing. To enable a remote reading or a remote maintenance of the measuring systems, the measuring device may be connected via data cables to a central server. A preferred embodiment of the invention is shown in the drawings and described followingly using the same. Herein it shows:

Fig. 1 at an early point of time, a schematically shown measuring arrangement for carrying out a method according to the invention according to an embodiment and

Fig. 2 at a check point of time the measuring arrangement for carrying out the method according to the invention of Fig. 1.

The drawings show a measuring arrangement for carrying out a method for determining the speed of vehicles 1 on a speed limited roadway 2. The measuring arrangement is arranged here for the digital speed check of vehicles 1 on the roadway 2, exemplary shown with two lanes, wherein the roadway 2 is conveniently shown with only one roadway direction. On a shoulder of the roadway 2, a cylindrical measuring column 3 is stationarily set-up. In the measuring column 3, a measuring device 4 is accommodated for measuring the speed of vehicles 1 on the roadway 2. The speed of the vehicle 1 may also be determined on a road with several directional roadways 2. For this, the measuring column 3 could be set-up stationarily on a central reservation of the road, wherein at least two of the measuring devices 4 10 1001439428 2016202560 21 Apr 2016 would be accommodated in the measuring column 3. In this way, at least one of the measuring devices 4 could be assigned to each directional roadway.

In more detail, the measuring device 4 has a first measuring system with a sensor device 5, which, in this embodiment, is designed as a LiDAR-sensor device (abbreviation for: Light Detection and Ranging). The sensor device 5 comprises a laser transmitter unit, not shown in more detail here, and a polygon mirror, also not shown in more detail, which directs laser beams being pulsed in a quick succession by means of the laser transmitter unit fan-like over the roadway 2. Furthermore, the sensor device 5 has a not shown laser receiver unit. The laser transmitter unit, the laser receiver unit and the polygon mirror are aligned such to the roadway that the sensor device 5 covers area-wide a detection area 7 that extends across both traffic lanes 6 of the roadway 2. When seen in the driving direction X, the detection area 7 extends, across a roadway length of 75 meters and is indicated in Figures 1 and 2 by the two dashed boundary lines 7’, 7”. Furthermore, the first measuring system comprises a first time measuring device 8, so that for each transmission and reception of a laser beam time stamps being necessary for measuring the time of flight can be set by means of the first time measuring device 8,

As soon as any vehicle 1, as shown in Fig. 1, enters the detection area 7, it is detected by the LiDAR-sensor device 5. By means of the sensor device 5, the first measuring system measures the distance D to the respective vehicle 1 by means of the time of flight method (TOF) several times. For this, the laser transmitter unit produces in a known manner short laser pulses, which are deflected by the polygon mirror across the traffic lanes 6 and thus, also projects them onto the respective vehicle 1. For each transmission of a laser beam, an output time stamp is set by means of the first time measuring device 8 and is stored together with the value of a beam angle of the laser beam being deflected by the polygon mirror. The laser beam reflected by the vehicle 1 is received by the laser receiver unit, wherein its incidence angle is provided with an input time stamp by means of the first time measuring device 8. By means of the difference between the output time and input time, i.e. the time of flight of the laser pulse to the vehicle 1 and back, the distance D is derived for the respective vehicle. To achieve an as accurate as possible movement profile of the respective vehicle 1 within the detection area 7, the distance D to the respective vehicle is measured 100 times per second. The first measuring system calculates 11 1001439428 2016202560 21 Apr 2016 the driving speed vpe of the respective vehicle by means of the time varying distances. When seen in driving direction X, this process is repeated several times, up to a distance of 40 meters to the measuring device 4. From the multitude of determined speed values, the first measuring system calculates an average value, so that as a result of the primary measuring method, an averaged driving speed vpe for each vehicle 1 is received. Even though the method is explained exemplary for only one vehicle 1, the measuring device 4 can analogously determine the distances D for several vehicles 1, present at the same time or one after the other within the detection area 7 simultaneously or one after the other, and correspondingly can determine simultaneously or one after the other the driving speeds vpe of several vehicles 1.

When the averaged driving speed vpe of the respective vehicle 1 exceeds an allowed speed limit on the roadway 2, the measuring device 4 autonomously checks the plausibility of the determined driving speed vpe within a secondary proof method automomously. For carrying out the autonomous plausibility check, the measuring device 4 is provided with a second measuring system. The second measuring system has a second time measuring device 9 being independent from the first time measuring device 8. In other words, the two time measuring devices 8, 9 provide independently from each other time values, particularly the current local time, which is ideally equal on the two time measuring devices 8, 9. The second measuring system is connected to the sensor device 5 of the first measuring system, so that the second measuring system has access to data of the sensor device 5.

According to a first possibility, an plausibility check is carried out on a roadway section 10 of fixed length Δχ. For this, the roadway section 10 is assigend to a section of the roadway 2 covered by the detection portion 7 of the sensor device 5. When seen in driving direction X, the roadway section 10 is limited at the entry side by a virtual entry line 11 and at the exit side by a virtual exit line 12. The virtual lines 11, 12 can be measured off locally on the roadway 2 before carrying out the speed detection, for example during the installation and repeatedly during maintenance work of the measuring device 4, and can be taught in two measuring systems software based via the sensor device 5. Thus, the virtual lines 11,12 correspond to real positions on the roadway 2, wherein the lines 11,12 themselves cannot be seen on the roadway 2 as markings. The two lines 11, 12 are measured parallel to each 12 1001439428 2016202560 21 Apr 2016 other and extend transversally across the roadway 2. When seen in driving direction X, in this embodiment the entry line 11 runs with a distance of 40 meters away from the exit line 12 runs with a distance of 30 meters away from the measuring device 4, so that the distance between the two lines 11,12 gives the length Δχ of the roadway section 10 with ten meters. Because of the predetermined distance of the two lines 11, 12 to each other, the length Δχ of the roadway section 10 can be included as a fixed value in the further calculations for the plausibility check.

As soon as the first measuring system has calculated the averaged driving speed value of the vehicle 1 on the roadway 2, the second measuring system monitors the virtual entry line 11 by means of the sensor device 5. When the sensor device 5 recognizes after the finish of the speed determination by means of the first measuring system on the roadway 2 any moving object point, which not necessarily has to be an object point of the to be checked vehicle 1, the second measuring system records by means of the second time measuring device 9 an entry point of time ti. The entry point of time ti is assigned to the to be checked vehicle 1.

Based on the recorded entry point of time ti and the driving speed vpe already determined by the primary measuring method, the second measuring system calculates a predicted time interval o, within the respective vehicle 1 would pass the roadway section 10 with a length Δχ of ten meters. Based on the predicted time interval ό and the recorded entry point of time t-ι, a check point of time t2 is determined. In this case, the formula is: t2 = t-ι + ό with u=—. At the check point of vpe time t2, the second measuring system monitors a defined section window 2x, around the exit line 12 by means of the sensor device 5. The section window 2x, represents the tolerance range, which is here ± 10% of the length Δχ of the roadway section 10, i.e. ± 1 meter. Thus, the sensor device 5 monitors at the check point of time t2 the section window 2xj with a length of 2 meters around the exit line 12, i.e. when seen in driving direction x, with x, = 1 meter before and x, = 1 meter behind the exit line 12. If the sensor device 5 detects at the check point of time t2, as shown in Fig. 2, an object point, here an object point of the to be checked vehicle 1, within the defined section window 2xj around the exit line 12, the driving speed of the vehicle 1 determined by the first measuring device is confirmed as plausible and is classified as provable by the plausibility check conducted by means of the second measuring 13 1001439428 2016202560 21 Apr 2016 system. For the preservation of evidence of the speed violation, at least one photo and/or a video of the vehicle 1 driving too fast can be combined with the local time and or location information of the violation to one combined evidence data set.

If in contrast no object point of an object, moving on the roadway 2 is within the section window 2x, around the exit line 12, speed violation cannot be proved. This may be the case, for example, when the checked vehicle 1 has slowed down drastically within the roadway section 10 or when the primary measuring method conducted by means of the first measuring system has led to a measuring error. Then, the driving speed ^determined with of the primary measuring method, cannot be confirmed by the secondary proof method. For this case, all vehicle related data are deleted from the measuring device 4 for data protection reasons. Such a deletion can be carried out automatically after a predefined time interval, for example after a minute.

In contrast to the above described first possibility, according to a second possibility, a plausibility check is carried out on a roadway section 10 of variable length Δχ. In contrast to the first possibility, the distance between the virtual entry line 11 and the virtual exit line 12 can vary in dependency of the determined driving speed vpe, wherein the entry line 11 has a fixed predefined distance of 40 meters to the sensor device 5. Insofar, the entry line 11 is measured off locally on the roadway 2 before carrying out the speed detection, for example during the installation or repeatedly during the maintenance work of the measuring device 4, and is taught in the two measuring systems software based via the sensor device 5. Thus, the virtual exit line 11 corresponds to real positions on the roadway 2, wherein the two lines 11, 12 themselves cannot be seen on the roadway 2 as markings.

As soon as the first measuring system has calculated the averaged speed value of the vehicle 1 on the roadway 2, the second measuring system monitors the virtual entry line 11 by means of the sensor device 5. When the sensor device 5 detects after the speed determination by means of the first measuring system any object point which not necessarily has to be an object point of the to be examined vehicle 1, moving on the roadway 2 the second measuring system records by means of the second time measuring device 9 an entry point of time t-ι. The entry point of time ti is assigned to the to be checked vehicle 1. 14 1001439428 2016202560 21 Apr 2016

From the entry point of time h and a defined time interval At-ι, which for example at a determined driving speed vpe of up to 30 km/h is 1.2 seconds, above 30 km/h up to 50 km/h is 0.72 seconds, above 50 km/h up to 100 km/h is 0.36 seconds, above 100 km/h up to 200 km/h is 0.18 seconds and above 200 km/h is 0.1 second, a check point of time t2 is determined, at which the second measuring system checks by means of the sensor device 5, whether any object point moving on the roadway 2 is present within the predefined section window 2x, around the virtual exit line 12. At a determined driving speed vpe of for example 70 km/h, thus, the check point of time t2 is the sum of the entry point of time ti and the time interval At of 0.36 seconds.

Furthermore, depending on the determined driving speed vpe, the section length Ax is predicted, which the vehicle 1 would pass when maintaining the determined driving speed vpe over the predetermined time interval At. At a determined driving speed vpe of 70 km/h, the vehicle 1 would drive over the predetermined time interval At, of exemplary 0.36 seconds, a section length Ax of 7 meters.

At the check point of time t2, the second measuring system monitors the defined section window 2x, around the exit line 12 by means of the sensor device 5. The section window 2xj represents a tolerance range, which is in this case ± 10% of the speed dependent length Ax of the roadway section 10. I.e. at a determined driving speed vpe of here 70 km/h the section window 2x, has a length of 1.4 meters. Thus, the sensor device 5 monitors at the check point of time t2 the section window 2x, with a length of 1.4 meters around the exit line 12, i.e. when seen in driving direction X, with Xj = 0.7 meters before and x, = 0.7 meters behind the exit line 12. If the sensor device 5 detects at the check point of time t2, as shown in Fig. 2, any object point, on the roadway 2 within the defined section window 2x, around the exit line 12, the driving speed of the vehicle 1 determined by the first measuring system is confirmed as plausible and is classified as provable by the plausibility check conducted by means of the second measuring system. For the preservation of evidence of the speed violation, at least one photo and/or a video of the vehicle 1, driving too fast can be combined in the known manner with the local time and a location information of the violation to one combined evidence data set.

If in contrast no object point of any object on the roadway 2 is present within the section window 2xj around the exit line 12, the speed violation is cannot be proved. 15 1001439428 2016202560 21 Apr 2016

This, for example, can be the case, when the to be checked vehicle 1 has drastically slowed down or the primary measuring method conducted by means of the first measuring system has led to a measuring error. As a result, the determined driving speed vpe determined with the primary measuring method cannot be confirmed by the secondary proof method. In this case, all data concerning the vehicle are deleted from the measuring device 4 because of data protection reasons. Such a deletion can be carried out automatically after a defined time interval, for example after one minute. 16 1001439428 2016202560 21 Apr 2016

Reference numerals list 1 vehicle 2 roadway 3 measuring column 4 measuring device 5 sensor device 6 traffic lane 7 detection area 8 first time measuring device 9 second time measuring device 10 roadway section 11 entry line 12 exit line 2xi section window D distance Δχ section length ti entry point of time t2 check point of time Vpe driving speed X driving direction 17

Claims

The claims defining the invention are:

1. Method for determining the speed of vehicles on a roadway, in which a first measuring system and a second measuring system are provided, the first measuring system is provided with a sensor device covering a detection area and a first time measuring device, wherein the first measuring system measures at several points of time the distance of a vehicle moving within the detection area and determines by means of the distance, changing over time, a driving speed of the vehicle and the second measuring system checks the determined driving speed, wherein the second measuring system is provided with a second time measuring device being independent of the first time measuring device, wherein the second measuring system monitors by means of the sensor device of the first measuring device a virtual entry line of a roadway section situated within the detection area and records by means of the second time measuring device an entry point of time, at which the sensor device of the first measuring device detects an object point at the entry line, wherein the second measuring system checks at least at a later check point of time by means of the sensor device of the first measuring device, whether an object point is within a defined section window around a virtual exit line of the roadway section.
2. Method according to claim 1, characterised in that a section length of the roadway section is known by a defined distance of the exit line to the entry line and that based on the known section length and the determined driving speed of the vehicle a predicted time interval is calculated, which the vehicle would need for passing the roadway section when maintaining the constant determined driving speed.
3. Method according to claim 2, characterised in that the second measuring system checks at the at least one check point of time, which corresponds the sum of the entry point of time and the predicted time interval, by means of the sensor device of the first measuring device, whether an object point is within the defined section window around the exit line.
4. Method according to claim 1, characterised in that a distance of the exit line to the entry line corresponds to a section length of the roadway section, which behaves proportional to the determined driving speed, wherein based on a defined time interval and the determined driving speed of the vehicle the section length is predicted, which the vehicle would pass when maintaining the determined driving speed within the time interval.
5. Method according to claim 4, characterised in that the second measuring system checks at least at the one check point of time, which corresponds to the sum of the entry point of time and of the defined time interval, by means of the sensor device of the first measuring device, whether an object point is within the defined section window around the exit line.
6. Method according to one of the preceding claims, characterised in that the determined driving speed of the vehicle is confirmed by the second measuring system, when an object point is within the defined section window around the virtual exit line at least at the one check point of time.
7. Method according to one of the preceding claims, characterised in that the determined driving speed of the vehicle is only checked by the second measuring system, if the driving speed is larger than a given maximum speed limit on the roadway.
8. Method according to one of the preceding claims, characterised in that the sensor device of the first measuring deviceis provided as an areawide monitoring or space-monitoring sensor device.
9. Method according to one of the preceding claims, characterised in that the sensor device of the first measuring device is provided as a LiDAR-sensor device or a radar-sensor device with a transmitter unit and a receiver unit in order to measure the distance to the vehicle by means of a time of flight method.