DE102014008732A1 - Method and device for monitoring a radar value of a radar system and traffic monitoring system - Google Patents

Abstract

A method is provided for monitoring a radar reading (101) of a radar system (102) of a traffic monitoring system (104). The traffic monitoring system (104) further has a laser scanner (110) which can be aligned in a detection area (106) of the radar system (102). The method includes a plausibility check step in which the radar reading (101) is plausibilized using a laser reading (119) of the laser scanner (110).

Description

State of the art

The present invention relates to a method for monitoring a radar measured value, to a corresponding device, to a corresponding computer program product and to a traffic monitoring system.

In a radar-based traffic monitoring system, reliable monitoring of radar system results is required to operate the traffic monitoring system without staffing.

Disclosure of the invention

Against this background, the present invention proposes a method for monitoring a radar value of a radar system of a traffic monitoring system, a device for monitoring a radar measurement of a radar system of a traffic monitoring system, a computer program product and a traffic monitoring system, according to the main claims. Advantageous embodiments emerge from the respective subclaims and the following description.

Traffic monitoring systems serve to enforce rules and laws in road traffic. A traffic monitoring system can serve the speed measurement and alternatively or in addition to the red light monitoring. In order to secure a measurement result of a radar system, the measurement result can be secured by at least one independently detected further measurement result. In this case, the further measurement result can be measured using a measurement method other than radar, for example to rule out a radar-type error. In particular, the further measurement result can be measured using a laser measuring device or a laser scanner.

The approach presented here enables an outstanding system for proof-proof speed measurement and red light recognition.

A method for monitoring a radar measurement of a radar system of a traffic monitoring system is presented, wherein the traffic monitoring system further comprises a laser scanner, which is alignable in a detection range of the radar system. The method includes a step of plausibilizing a radar reading using a laser reading, wherein the radar reading represents a reading of the radar system and the laser reading represents a reading of the laser scanner.

A radar system can be understood to mean a device having a transmitter for a radar signal or radar waves or radar beams and a receiver for a radar echo of the radar signal. Transmitter and receiver can be combined in one unit. The radar signal consists of electromagnetic waves. The radar system may include an evaluation unit configured to calculate a distance of the object from the radar system using a signal transit time of the radar signal from the transmitter to an object and an echo time of a radar echo from the object to the receiver. The evaluation unit can also be designed to calculate a speed of the object from a frequency change of the received radar echo with respect to the transmitted radar signal. The speed can also be calculated from a change in the distance between at least two measurements. When the radar signal is emitted and / or received with a pronounced directional characteristic, a direction from the radar system to the object can be determined. The evaluation unit may provide the distance and / or direction and / or speed as the radar reading. A laser scanner can be a device with a transmitter for a laser signal or a laser beam or laser waves and a receiver for a laser echo of the laser signal. Transmitter and receiver can be combined in one unit. The laser signal can be sent in bundled form. The laser signal can be emitted with a predetermined divergence. The laser signal can be sent out by scanning a web. The laser scanner may include an evaluation unit configured to calculate, using a signal propagation time of the laser signal from the transmitter to the object and an echo time of the laser echo from the object to the receiver. By changing the distance between at least two measurements, the speed of the object can be determined. The evaluation device can provide the distance, direction and / or velocity of the object in the laser measurement. The laser reading and / or radar reading may be provided when an object is detected.

The radar measured value and the laser measured value may each represent a speed and, alternatively or additionally, a location of a vehicle in the detection area.

In the step of plausibility checking, the radar measured value can be confirmed as a speed value and / or as a location value for the vehicle, if the radar reading and the laser reading correspond to one another, for example, having values within a tolerance range for the speed or within a tolerance range lying values for the position of the vehicle. For example, the radar reading may be confirmed as a speed value and for the vehicle when the laser reading substantially reflects the speed of the vehicle from the radar reading. Accordingly, the radar reading may be confirmed as the location value for the vehicle when the laser reading substantially reflects the location of the vehicle from the radar reading. For example, the radar reading may be confirmed when the laser reading reflects the location and / or speed of the vehicle within a tolerance range to the location and / or speed of the radar gauge.

The method may include a step of evaluating in which a comparison is made between the speed value and a maximum speed value. In this case, depending on a comparison result of the comparison, a speed violation signal can be output. Alternatively or additionally, in the step of evaluating a comparison between the location value and a predetermined position value can be performed. In this case, a location violation signal can be output depending on a comparison result of the comparison. A maximum speed value may correspond to a speed limit in the detection area. The speed violation signal may be output when the speed value deviates by a tolerance range from the maximum speed value. The position value may be assigned to a position in the detection area. The position value may correspond, for example, to a stop line on a traffic signal system. The position violation signal may be output when the location value deviates by more than a tolerance range from the position value. For example, when the vehicle drives over the stop line in red.

The method may include a step of determining a vehicle class of the vehicle using a plurality of laser readings of the laser scanner assignable to the vehicle and a step of determining the maximum speed value and / or the location value using the vehicle class of the vehicle.

Thus, the maximum speed value and, alternatively or additionally, the location value may be determined using a vehicle class of the vehicle, which in turn may be determined from a plurality of laser readings of the laser scanner assignable to the vehicle. This allows the laser scanner to be used to classify vehicles. For example, a lower maximum speed value may apply to trucks than to passenger cars. Likewise, for example, in a no-overtaking ban on trucks, it can be checked whether the truck is driving on the lane assigned to it.

The method may include a step of detecting the radar reading using the radar system. In the step of detecting, the laser measurement value may also be detected using the laser scanner to obtain information about a vehicle in the detection area.

The radar reading and the laser reading can be acquired in a common time window. In particular, the radar measured value can be detected substantially simultaneously with the laser measured value. As a result, for example, during braking or acceleration of the vehicle, an undesired difference between the measured values can be avoided.

In the step of detecting, at least one license plate of the vehicle may be detected by the laser scanner to obtain the laser measurement. Thus, in the step of detecting, the laser measured value can be detected as a measured value of the laser scanner directed to a license plate of the vehicle. A license plate can be called a license plate. The license plate can reflect back the laser light of the laser scanner particularly well. This allows a strong echo to be received.

Furthermore, a device for monitoring a radar measured value of a radar system of a traffic monitoring system is presented. The traffic monitoring system further comprises a laser scanner, which can be aligned in a detection range of the radar system. The device has a device for plausibilizing a radar measured value using a laser measured value, the radar measured value representing a measured value of the radar system and the laser measuring value representing a measured value of the laser scanner.

In the present case, a device can be understood as meaning an electrical device which processes sensor signals and outputs control and / or data signals in dependence thereon. The device may have an interface, which may be formed in hardware and / or software. In the case of a hardware-based embodiment, the interfaces can be part of a so-called system ASIC, for example, which contains a wide variety of functions of the device. However, it is also possible that the interfaces are separate, integrated circuits or at least partially discrete Consist of components. In a software training, the interfaces may be software modules that are present, for example, on a microcontroller in addition to other software modules.

Furthermore, a traffic monitoring system for monitoring a detection area of a traffic area is presented, wherein the monitoring system has the following features:
a radar system for detecting the detection area, wherein the radar system is configured to provide a radar reading including information about a radar reading representative of a vehicle located in the detection area;
a laser scanner aligned with the detection area and configured to provide a laser reading comprising information about the vehicle in the detection area; and
a device according to the approach presented here to plausibilize the Radarmesswert using the laser measurement.

The radar system and, alternatively or in addition, the laser scanner can be arranged at a height of between two meters and six meters. The radar system and the laser scanner can be arranged in particular between three meters and five meters above ground level. In particular, the radar system and the laser scanner can be arranged approximately four meters above the traffic area. By an arrangement in height, the detection area can be detected safely. In addition, the traffic detection system is protected against damage.

The laser scanner can be designed to monitor a line-shaped monitoring area on the traffic area. As a result, at least one entire lane can be monitored with a laser.

A computer program product with program code which can be stored on a machine-readable carrier such as a semiconductor memory, a hard disk memory or an optical memory and is used to carry out the method according to one of the embodiments described above if the program product is installed on a computer or a device is also of advantage is performed.

The invention will now be described by way of example with reference to the accompanying drawings. Show it:

1 a block diagram of an apparatus for monitoring a radar measured value of a radar system of a traffic monitoring system according to an embodiment of the present invention;

2 an illustration of a traffic monitoring system according to an embodiment of the present invention;

3 a representation of a vehicle in a monitoring area of a laser scanner of a traffic monitoring system according to an embodiment of the present invention;

4 A representation of geometric relationships of a laser scanner of a traffic monitoring system according to an embodiment of the present invention;

5 a representation of a truck by a laser scanner of a traffic monitoring system according to an embodiment of the present invention; and

6 a flowchart of a method for monitoring a radar measured value of a radar system of a traffic monitoring system according to an embodiment of the present invention.

In the following description of favorable embodiments of the present invention, the same or similar reference numerals are used for the elements shown in the various figures and similar acting, with a repeated description of these elements is omitted.

1 shows a block diagram of a device 100 to monitor a radar reading 101 a radar system 102 a traffic monitoring system 104 according to an embodiment of the present invention. The traffic monitoring system 104 is designed to be a detection area 106 a traffic area 108 to monitor. The traffic monitoring system 104 has the radar system 102 for entering the coverage area 106 and a laser scanner 110 on, also on the detection area 106 is aligned. The device 100 is also part of the traffic monitoring system 104 ,

The radar system 102 is designed to measure the radar reading using radar signals 101 to provide information about one in the coverage area 106 located vehicle 112 represents.

By a period of time between emitting a radar signal and receiving a signal on the vehicle 112 reflected radar signal can be a distance between the radar system 102 and the vehicle 112 be determined. By at least two distance measurements, a speed of the vehicle 112 be determined. Likewise, a frequency shift of the reflected radar signal can be evaluated to obtain the speed. The laser scanner 110 is designed to use a controllable laser, a line-shaped monitoring area 114 on the traffic area 108 monitor, with the surveillance area 114 within the coverage 106 is arranged. By a period of time between emitting a laser signal and receiving a signal on the vehicle 112 reflected laser signal can be a distance between the laser scanner 102 and the vehicle 112 be determined. The laser scanner 110 is trained to a laser measurement 119 provide a radar value 101 corresponding information about the vehicle 112 represents when the vehicle is 112 within the surveillance area 114 located. The traffic monitoring system 104 with the radar system 102 and the laser scanner 110 is on a mast 116 at a height of about four meters above the traffic area 108 arranged. The traffic area 108 is in this embodiment, an intersection of two roads.

The coverage area 106 includes much of the intersection area and part of one of the roads.

The device 100 has a facility 118 to make the radar reading plausible 101 using the laser reading 119 on. The radar reading 101 represents a current location of the vehicle 112 in the detection area 106 and additionally or alternatively a current speed of the vehicle 112 , The laser measurement 119 represents a current location of the vehicle 112 within one of the laser scanner 110 emitted laser fan 120 and additionally or alternatively a current speed of the vehicle 112 , The device 118 is designed to be the radar reading 101 and the laser reading 119 via an interface to receive and the radar reading 101 using the laser reading 119 to make it plausible. In one embodiment, the device is 118 trained to the radar reading 101 as a speed value and / or local value for the vehicle 112 to confirm if the laser reading 119 by the radar reading 101 displayed speed and / or by the Radarmesswert 101 displayed location of the vehicle 112 essentially, for example within specified tolerances.

According to one embodiment, in 1 is a red light measuring system 104 and / or a speed measuring system 104 with a tracking radar 102 and an elevated laser scanning system 110 shown. The red light measuring system 104 and / or the speed measuring system 104 is intended for use within traffic safety. The tracking radar 102 and the laser scanning system 110 can be considered field-proven subcomponents 102 . 110 be realized.

Advantageously, by the described approach using the laser scanner 110 the use of radar systems 102 for red light measuring systems 104 and speed measuring systems 104 be approved in unsupervised operation, as the rare cases can be detected in which the radar 102 due to multiple reflections an object 112 does not measure correctly. Likewise, due to the approach described, it is not required by the radar 102 the measurement of a highly accurate spatial position, in particular less than 0.25 m deviation to make.

For a reliable speed measurement, the laser scanner 110 be mounted at a height of about one meter above the ground. Typical is a height of 0.9 m to 1.4 m. At this installation height, however, the device is at risk of vandalism. In addition, the device is often covered by transverse movements. The approach proposed here is the laser scanner 110 spatially close to the tracking radar 102 mounted in a relatively high altitude. A typical height is about four feet above ground.

In the 1 The illustration shown mainly refers to crossing scenarios. This presentation is to be seen as an example. The proposed system 104 can be just as good as a pure speed measuring system 104 at a bridge or at a mast 116 operate. Modern radar systems 102 can be used to monitor red light violations. However, it can not be ruled out with 100% certainty that in rare cases false alarms will occur. For this reason it is suggested to use the laser scanner 110 also increased to mount and parallel to the tracking radar 102 to operate. For assembly reasons, the laser scanner 110 advantageous spatially close to the tracking radar 102 be installed. This spatially close association is not mandatory. The laser scanner beam 120 is aligned in such a way that, for example, it passes over the area of the holding beam in the case of red light monitoring. A good value for the center beam position on the target object 112 is about 0.6 m above ground, since at this altitude the very well reflective license plate of the vehicle 112 located. The beam 120 of the laser scanner 110 expands due to the divergence in horizontal and vertical direction. The expansion in the vertical direction is typically 19 milliradians. This effect means that, for example, the license plate with a mounting height of 0.5 m to 0.6 m above ground is much longer in the laser beam 120 seen as it would come from a simple ray tracing.

2 shows a representation of a traffic monitoring system 104 according to an embodiment of the present invention. The traffic monitoring system 104 essentially corresponds to the traffic monitoring system in 1 , In contrast, the traffic monitoring system 104 arranged here at a sign bridge or bridge. The traffic monitoring system 104 can over a multi-lane road 108 be arranged. In this case, the system components of the traffic monitoring system 104 be arranged within a single housing. Similarly, the laser scanner and the radar system can be attached as independent units to the gantry. The monitoring device may also be arranged in a remote installation box to allow easy service.

In the illustrated embodiment moves on the street 108 a tractor with semi-trailer 112 or a tractor-trailer 112 , The tractor trailer 112 is already within the detection range for more than one vehicle length 106 of the radar system. A size of the detection area 106 results from an opening angle of radar beams 200 of the radar system and an angle of incidence of the radar beams 200 in the street 108 , The radar opening angle here is 24 °. The laser beam 120 or laser fan 120 Here is the center of the radar beams 200 aligned. The laser beam 120 meets the tractor 112 in the area of a license plate 202 , The laser beam 120 expands to less than one degree. In particular, the laser beam has an aperture angle of 19 milliradians [mrad]. The license plate 202 is retroreflective and thereby enables a large proportion of the laser beam 120 is returned to the laser scanner, a strong signal from which the laser reading can be determined.

Because the laser scanner is also one of the vehicle 112 Reflected laser light is received when the license plate 202 outside the laser beam 120 The laser scanner forms the vehicle 112 three-dimensional while it is under the laser beam 120 by moving. From a resulting spatial information can a vehicle class of the vehicle 112 be determined because a passenger car is pictured differently than a truck.

3 shows a representation of a vehicle 112 in a surveillance area 114 a laser scanner 110 a traffic monitoring system according to an embodiment of the present invention. The laser scanner 110 is like in 1 on a mast 116 Installed. The laser beam 120 of the laser scanner 110 is sent from a height H _inst over ground. The laser beam 120 is at an angle α on the road 108 aligned. The vehicle 112 has a reflective license plate on a vehicle front 202 or license plate 120 on. When the laser beam 120 on the license plate 202 meets, a large part of the emitted laser light to the laser scanner 110 reflected back, whereby the laser measurement can be determined very well. The license plate 202 can from the laser scanner 110 be detected as soon as a lower edge of the license plate 202 an upper limit of the laser beam 120 transgresses. The license plate 202 can be so long from the laser scanner 110 be detected until an upper edge of the license plate 202 a lower limit of the laser beam 120 leaves. The upper limit and the lower limit are due to a divergence of the laser beam 120 certainly. The divergence is here as in 2 at about 19 milliradians. Between the place where the lower edge of the license plate 202 in the laser beam 120 penetrates, and the place where the license plate 202 from the laser beam 120 exit is the surveillance area 114 arranged. The surveillance area 114 lies between a point of impact of the laser beam 120 on the street and the mast 116 on which the laser scanner 110 is arranged. A distance value D _Inst describes a distance between the installation mast 116 and the location of the last visibility of the vehicle 112 or, at the top of the license plate 202 exits from the lower limit.

From a sample calculation for the coverage area 114 it can be seen that the detection area 114 the shorter the higher the laser scanner 110 is attached and the smaller the distance between the laser scanner 110 and the holding bar is. Therefore, the condition may arise that for a high-precision velocity estimation alone from the laser scanner data, the observation area 114 too small. Nevertheless, the area is 114 at least be so large that a valid estimate of the speed and the location can be derived. The estimate thus obtained will be against the radar measurement data regarding the location and speed of the vehicle 112 adjusted. Only if the measurement of the radar is consistent with the estimate of the laser scanner 110 is, the measurement is output as validated.

wobei L_Det + D_Inst = (H_Inst – H_max)tan(α + δ) 4 shows a representation of geometric relationships in a laser scanner 110 a traffic monitoring system according to an embodiment of the present invention. The presentation essentially corresponds to the representation in 3 , In addition, here are the upper limit 400 and the lower limit 402 of the laser beam 120 shown. Between the upper limit 400 and the lower limit 402 is the opening angle δ or the expansion of the laser beam 120 from 19 mrad. Because the license plate 202 At 0.5 meters above ground level and 0.6 meters above ground level, H _min at 0.5 m represents the minimum height required by the laser scanner 110 is seen. H _max , at 0.6 m, represents the maximum height seen by the laser scanner. Between a location of H _min and a location of H _max , L _Det extends the detection length of the laser 110 is detected. This results in an angle α to be set of the laser beam 120 With

in which L _Det + D _Inst = (H _Inst - H _max ) tan (α + δ)

H _Inst is the installation height of four meters. D _Inst is the distance to the stop line at 30 m. The limits of the area to be detected on the vehicle are H _Max at 0.6 m and H _Min at 0.5 m. The angle of the laser beam 120 α is 1.45794452 rad or 83.5340679 degrees. The vertical divergence δ is 19 mrad or 0.019 rad. In this case, α and δ are complementary to 1,476,94,452 rad. The maximum height difference between the installation height H _Inst and the area to be detected is 3.5 meters. L _Det is the measuring section with 7.18327844 meters. With the distance to the stop line D _Inst results a distance of 37.1832784 m. The maximum expected speed is assumed to be 70 m / s. The laser has a scan rate of 100 Hz. In other words, the surveillance area 100 sampled once per second. At a vehicle traveling at the maximum expected speed, 10.2618263 scans will result as the vehicle travels through the L _Det measurement path.

5 shows a representation 500 a truck 112 by a laser scanner of a traffic monitoring system according to an embodiment of the present invention. The laser scanner scans its surveillance area line by line. In the process, objects within the surveillance area are detected in the form of a two-dimensional section line. As the vehicle 112 moved relative to the laser beam, in particular moved transversely to the laser fan, represents the movement of the vehicle 112 a third dimension for the capture available. In other words, the vehicle drives 112 under the laser scanner. In this case, using the vehicle movement is a three-dimensional image 500 of the vehicle 112 calculated from a plurality of two-dimensional lines of intersection of the vehicle. The image 500 is not very detailed. Because of the image 500 but can be a class of the vehicle 112 be recognized. In particular, a distinction can be made between a passenger car and a truck.

The proposed system also has the advantage that the laser scanner based on the estimated vehicle width can provide a classification of the vehicle category (cars / trucks), which is difficult to determine in a frontal radar.

In one embodiment, a class-dependent speed limit is thus monitored. Then different speed limits are monitored for trucks and passenger cars.

Likewise, for example, a truck overtaking ban can be monitored. Then a violation of the overtaking ban can be detected when a truck is detected in a lane that is not released for the truck.

6 shows a flowchart of a method 600 for monitoring a radar reading of a radar system of a traffic monitoring system according to an embodiment of the present invention. The method may be applied to a device for monitoring a radar reading, as shown in FIG 1 is shown to be executed. The procedure 600 has at least one step 602 plausibility. In step 602 In the case of plausibility, the radar reading is plausibilized using the laser reading.

In one embodiment, the step is 602 Plausibilizing a step 604 upstream of the detection. In step 604 the radar reading is detected using the radar system. Furthermore, a laser measurement is detected using the laser scanner. The radar reading and the laser reading are recorded in a common time window. The laser scanner can be aligned so that a license plate of a vehicle is detected in a detection range of the radar system of the laser scanner. Thus, the laser reading may correspond to a reading of the laser scanner at a time when the license plate is detected by the laser scanner.

The radar reading may represent a speed value and / or a location value of a vehicle in the detection area.

In a further embodiment, the step 602 Plausibilizing a step 606 downstream of the evaluation.

In step 606 of the evaluation, a comparison can be made between a speed value represented by the radar measured value and a maximum speed value. Depending on a comparison result of the comparison, a speed violation signal is output. Alternatively or additionally, a comparison is made between a location value represented by the radar measured value and a predetermined position value. Depending on a comparison result of the comparison, a position violation signal is output. The maximum speed value and, alternatively or additionally, the location value may be determined using a vehicle class of the vehicle. In this case, according to one exemplary embodiment, the vehicle class is determined using a plurality of laser measurement values of the laser scanner that can be assigned to the vehicle.

The embodiments described and shown in the figures are chosen only by way of example. Different embodiments may be combined together or in relation to individual features. Also, an embodiment can be supplemented by features of another embodiment.

Furthermore, method steps according to the invention can be repeated as well as carried out in a sequence other than that described.

If an exemplary embodiment comprises a "and / or" link between a first feature and a second feature, then this is to be read so that the embodiment according to one embodiment, both the first feature and the second feature and according to another embodiment either only first feature or only the second feature.

LIST OF REFERENCE NUMBERS

100

Device for monitoring

101

Radar Reading

102

radar system

104

Traffic monitoring system

106

detection range

108

Traffic area, street

110

laser scanner

112

vehicle

114

monitoring area

116

mast

118

Setup for plausibility

119

Laser measurement

120

Laser beam, laser fan

200

radar beams

202

license plate

D _Inst

distance value

H _Inst

height

α

angle

400

upper limit

402

lower limit

L _Det

Detection length, measuring distance

H _Min

largest height of the license plate

H _M

smallest height of the license plate divergence

δ

divergence

600

Method of monitoring

602

Step of plausibility

604

Step of grasping

606

Step of the evaluation

Claims (12)

Procedure ( 600 ) for monitoring a radar reading ( 101 ) of a radar system ( 102 ) of a traffic monitoring system ( 104 ), which further comprises a laser scanner ( 110 ), which enters a detection area ( 106 ) of the radar system ( 102 ), the process being 600 ) comprises the following step: Plausibility check ( 602 ) of a radar reading ( 101 ) using a laser measurement ( 119 ), the radar reading ( 101 ) a measured value of the radar system ( 102 ) and the laser measurement ( 119 ) a reading of the laser scanner ( 110 ). Procedure ( 600 ) according to claim 1, wherein the radar reading ( 101 ) and the laser measurement ( 119 ) one speed and / or one location of a vehicle ( 112 ) in the coverage area ( 106 ), wherein in the step of plausibility ( 602 ) the radar reading ( 101 ) as a speed value and / or as a location value for the vehicle ( 112 ) is confirmed when the radar reading ( 101 ) and the laser measurement ( 119 ) correspond to each other. Procedure ( 600 ) according to claim 2, comprising a step of evaluating ( 606 ), in which a comparison between the speed value and a maximum speed value is performed, wherein a speed violation signal is output and / or in which a comparison between the location value and a predetermined position value is performed depending on a comparison result of the comparison, depending on a comparison result of Comparison a location violation signal is output. Procedure ( 600 ) according to claim 3, wherein in the step of evaluating ( 606 ) a vehicle class of the vehicle ( 112 ) using a plurality of the vehicle ( 112 ) assignable laser measurement values ( 119 ) of the laser scanner ( 110 ) and the maximum speed value and / or the location value using the vehicle class of the vehicle ( 112 ) is determined. Procedure ( 600 ) according to any one of the preceding claims, comprising a step of detecting ( 604 ) of the radar reading ( 101 ) using the radar system ( 102 ) and / or detecting ( 604 ) of the laser measurement value ( 119 ) using the laser scanner ( 110 ) to obtain information about a vehicle ( 112 ) in the coverage area ( 106 ) to obtain. Procedure ( 600 ) according to claim 5, wherein in the step of detecting ( 604 ) the radar reading ( 101 ) and the laser measurement ( 119 ) are detected in a common time window. Procedure ( 600 ) according to one of claims 5 to 6, in which in the step of detecting ( 604 ) the laser measuring value ( 119 ) as a reading of a license plate ( 202 ) of the vehicle ( 112 ) directed laser scanner ( 110 ) is detected. Contraption ( 100 ) for monitoring a radar reading ( 101 ) of a radar system ( 102 ) of a traffic monitoring system ( 104 ), which further comprises a laser scanner ( 110 ), which enters a detection area ( 106 ) of the radar system ( 102 ) is alignable, wherein the device ( 100 ) has the following features: a device ( 118 ) for checking the plausibility of a radar reading ( 101 ) using a laser measurement ( 119 ), the radar reading ( 101 ) a reading of the radar system and the laser reading ( 119 ) represents a measured value of the laser scanner. Traffic monitoring system ( 104 ) for monitoring a detection area ( 106 ) of a traffic area ( 108 ), the monitoring system ( 104 ) has the following features: a radar system ( 102 ) for detecting the detection area ( 106 ), whereby the radar system ( 102 ) is adapted to provide a radar reading ( 101 ) containing information about one in the coverage area ( 106 ) vehicle ( 112 ); a laser scanner ( 110 ), which refers to the scope ( 106 ) and is adapted to receive a laser measurement ( 119 ) providing information about the in the coverage area ( 106 ) vehicle ( 112 ); and a device ( 100 ) according to claim 8, to determine the radar reading ( 101 ) using the laser measurement ( 119 ) to make it plausible. Traffic monitoring system ( 104 ) according to claim 9, in which the radar system ( 102 ) and / or the laser scanner ( 110 ) at a height (H _inst ) between two meters and six meters. Traffic monitoring system ( 104 ) according to one of the preceding claims, in which the laser scanner ( 110 ) is adapted to a line-shaped monitoring area ( 114 ) on the traffic area ( 108 ). Computer program product with program code for carrying out the method ( 600 ) according to one of claims 1 to 7, when the program product is executed on a device.

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