WO2003052716A1

WO2003052716A1 - Method for the geometric measurement and tracing of objects by means of laser scanners

Info

Publication number: WO2003052716A1
Application number: PCT/AT2002/000340
Authority: WO
Inventors: Dieter Schmidradler
Original assignee: Kapsch Trafficcom Ag
Priority date: 2001-12-14
Filing date: 2002-12-05
Publication date: 2003-06-26
Also published as: ATA19622001A; AU2002361367A1; AT412746B

Abstract

The invention relates to a method and a device for the geometric measurement and tracing of objects (6), such as motor vehicles, moving along a road in the longitudinal direction of the same, by means of at least two laser scanners (1, 2, 27, 28) which are respectively mounted above the level of the road. Said laser scanners scan the road or an object (6) moving along said road, within a defined measuring range in a measuring plane, and produce a profile of the object in the measuring plane as measuring data of a scan cycle. The invention is characterised in that the measuring plane of at least one first laser scanner (1, 27) is oriented essentially perpendicularly to the road and the measuring plane of at least one second laser scanner (2, 28) is oriented essentially in the longitudinal direction of the road, and in that the measuring data of the laser scanner is linked to a time-related spatial representation of the objects.

Description

METHOD FOR GEOMETRIC MEASUREMENT AND TRACKING OF OBJECTS BY MEANS OF LASER SCANNERS

The present invention relates to a method and a device for geometric measurement and tracking of objects moving on a roadway in the longitudinal direction of the same, such as motor vehicles, with the aid of at least two laser scanners, which are respectively mounted above the roadway level and the roadway or on it scanning the moving object within a limited measuring range in a measuring plane and generating a profile of the object in the measuring plane as measuring data of a scanning cycle. The device also includes a computer system connected to the laser scanner for evaluating the measurement data. The geometry of motor vehicles is a possible evaluation criterion for the classification of vehicles, typical application fields are the determination of tariff levels for toll collection, applications of the traffic control system or the statistical collection of traffic data. The required scope of services ranges from the pure sequence control (eg starting a tolling process, control of barriers) to complex measuring tasks such as the geometric measurement of towing vehicles, trailer recognition or the detection and classification of side-by-side single-track vehicles. Today, various sensor concepts are pursued in single-lane surroundings (typical: toll stations with manual handling) for the tracking and classification of vehicles as well as for the timing of processes. The sensor arrangement and the measurement data evaluation are always designed specifically for the application. Induction loops are used, if necessary in combination with other sensors such as light barriers, light curtains or other sensors in the. Lane to meet the requirements of each measurement task. A method of the type mentioned is known for example from WO 90/09014, which describes two laser scanners, which are oriented in each case normal to the direction of travel. The vehicle speed is determined from the path-time difference of the successive passing of the laser scanner. A determination of the geometry of a vehicle is not disclosed in this document.

Due to their application-specific adaptation to the respective task all known systems are neither universally applicable nor modular expandable. Moreover, due to the majority of individual sensors, the known systems always have certain detection gaps between the sensors, which leads to measurement and classification errors in adverse operating conditions such as bad weather, stop-and-go traffic situations, and consequently to impaired operation can lead.

In accordance with the above, it is the object of the present invention, the geometry and the location of single and multi-lane vehicles in single-lane road sections even in adverse environmental conditions, such as stop-and-go traffic or impaired weather, using laser scanners reliably in to measure a way that allows easy adaptation to all today common tasks of geometric vehicle measurement, classification and tracking.

This object is achieved in a first aspect of the invention with a method of the aforementioned type, which is characterized in that the measuring plane of at least one first laser scanner substantially transverse to the roadway and the measuring plane of at least one second laser scanner substantially in the longitudinal direction of the roadway is, and that the measurement data of the laser scanner are linked to a time-related spatial representation of the objects.

The term "substantially transverse to the direction of travel" used in the present description does not require an orthonormal orientation of the measuring plane to the direction of travel; Rather, it also includes any suitable inclinations, as long as the first laser scanner allows detection of the transverse profile of the objects passing. In the same way, the term "substantially in the longitudinal direction of the roadway" does not necessarily mean a parallel alignment of the measuring plane of the second laser scanner with the direction of travel, but rather also includes any suitable inclinations as long as the second laser scanner detects a longitudinal position of the passing objects, ie their position in the direction of travel, allows.

Compared to the known vehicle classification and tracking systems, in which the base information to be provided is at least provided for the purpose of fulfilling the present measuring task and the appropriate sensor is compiled, the invention proceeds from the novel knowledge, which is typical of single-lane road sections To generate conditions as complete as possible image of the measuring range, in order to be able to incorporate in the individual case required additional information in a particular case with relatively low adaptation effort in the overall system. This is achieved in a particularly simple and trouble-free way by the use of two generally crossed scanned laser scanners, which enable gapless imaging and tracking of vehicles passing in the measuring range. Thus, a high degree of Meßredundanz is achieved, which ensures trouble-free operation even in adverse environmental conditions, such as bad weather, stop-and-go traffic, etc. The temporally and spatially linked joint evaluation of the measured data of the two laser scanners achieves a total functionality that goes far beyond the achievable with separate treatment of the individual measurements.

According to a preferred embodiment of the invention, the first laser scanner is seen in the object direction of travel in front of the second laser scanner arranged and, if the profile measured by him exceeds a predetermined threshold criterion for the detection of a new object, registered this profile as the front of a new object representation. This represents a particularly simple and trouble-free way of detecting a passing object.

In this case, the object representations registered by the first laser scanner can be verified and their movements can be tracked on the basis of the measured data of the second laser scanner, which further increases the susceptibility to interference. It is even better if, in addition, the movements of the object representations pursued by the second laser scanner are also verified for plausibility on the basis of the measurement data of the first laser scanner. According to a further preferred feature of the invention, measurement data of successive scanning cycles of the first laser scanner, which have a common overlap region, are assigned to the same object representation, which further increases the operational reliability of the method. It may be preferred that for small object representations the possible overlap area is increased with a search area, e.g. Also to assign trailer drawbar areas of road trains or single-track vehicles correctly. In any case, it is particularly favorable if objects whose length can not be determined by the second laser scanner are assigned a predetermined standard length, in order to arrive at a deliverable result in each case.

Further preferred variants of the invention consist in that a plurality of first laser scanners are spaced from one another in the longitudinal direction of the lane and / or a plurality of second laser scanners are arranged at a distance from one another in the lane transverse direction. As a result, an even greater Meßredundanz can be achieved. In addition, with the aid of light barriers, the movement tion direction of the object representations recognized and / or verified.

Last but not least, with the aid of sensors in the roadway, preferably pressure sensors, the number of vehicle axles of an object can be determined in order to obtain additional evaluation criteria for the verification and classification of the measurement results.

In a second aspect of the invention, the above-mentioned objects are achieved with a device for geometric surveying and tracking of objects moving on a roadway in the longitudinal direction of the same, such as motor vehicles, with at least two laser scanners each mounted above the roadway level scanning the roadway or an object moving thereupon within a limited measuring range in a measuring plane and generating a profile of the roadway in the measuring plane as measuring data of a scanning cycle, and with a computer system connected to the laser scanner for evaluating the measuring data which thereby results characterized in that the measuring plane of at least a first laser scanner substantially transverse to the roadway and the measuring plane of at least a second laser scanner is oriented substantially in the longitudinal direction of the road and the computer system, the measurement data of the laser scanner to a time-related spatial Repräse ntation of the objects linked. Preferred features of the device according to the invention are specified in the subclaims. With regard to the advantages of these embodiments, reference is made to the corresponding comments on the method.

Further features and advantages of the invention will become apparent from the following description with reference to embodiments shown in the enclosed drawings. In the drawings, Figures la to lc show an example of a sensor arrangement in side view (Figure la), in plan view (Figure lb) and in front view (Figure lc); FIGS. 2a to 2f show, by way of an example, the principle of object measurement at six temporally successive, exemplarily selected times, u.zw. each on the left in the side view and on the right in the front view; 3 shows a flow chart for the cyclic measurement data evaluation; 4a to 4o an example of the principle of the context analysis at fifteen temporally successive, exemplarily selected times, u.zw. each seen in the measurement plane of the transverse scanning laser scanner, ie in the front view;

Fig. 4p is the drawing legend for Figs. 4a to 4o; FIGS. 5a to 5h show, by way of an example, the principle of recognition and tracking of vehicles driving one behind the other at eight time-sequential, exemplarily selected points in time, u.zw. each on the left in the side view and on the right in the front view; and Figs. βa and βb show examples of expansion possibilities of the method or apparatus. FIGS. 1a to 1c show an example of an advantageous realization of the invention. In the present case, laser scanners mounted above the roadway are used, with one laser scanner 1 performing the measurement of the transverse profile and the other laser scanner 2 effecting the measurement of the vehicle in the longitudinal direction (travel direction 5). A pair of light barriers 3 makes it possible to detect vehicles that can not be reliably tracked by the second laser scanner 2 at a defined longitudinal position. The Cartesian reference system 4 is uniformly chosen for this and the following figures.

As an application example, the typical task is to determine the length, width and height of vehicles and their trailer status; These data should be output together with a unique vehicle number when a defined longitudinal position is reached. A retreat An already completed vehicle should be reported as well as a vehicle passage in the wrong direction. Finally, the juxtaposition of single-lane vehicles and the close succession of vehicles within the observation area should not lead to any errors in vehicle measurement and tracking.

A vehicle 6 entering in the correct direction of travel 5 is detected by both laser scanners and registered by the system. FIGS. 2a to 2f show the tracking and surveying of a multi-lane motor vehicle with a trailer at selected points in time. After the object has been registered in the system (FIG. 2a) and moves further in the direction of travel, the trailer drawbar is occasionally detected only at a single measuring point (FIG. 2b). In order to prevent the coherent object from being "torn off", this measuring point must not be eliminated by any filtering operations whatsoever, since, as will be shown later, this measured value could well have originated from a singular false measurement (raindrops, etc.) In addition, measures are taken which enable a robust distinction between a measurement error and an object detection.

The vehicle continues to move and the end of the vehicle is detected in the measuring range of the first laser scanner 1 (FIGS. 2c, 2d). If this is the case, the length of the vehicle is measured by determining the measuring point with the maximum longitudinal position which is available from the second scanner 2 and which is assigned to the vehicle. The measurement results assigned to the vehicle are output upon reaching a defined longitudinal position 3 (FIGS. 2e, 1a, 1b). Finally, the vehicle leaves the measuring range in the correct direction.

It can be seen from the side views that measured values at road level are always detected between towing vehicle and trailer, ie the trailer drawbar would not be reliably detected from the perspective of the second scanner 2. Nevertheless, to ensure correct tracking of the complete driving In this case, linking of the information determined on the basis of the measured data of the first laser scanner 1 with the information determined based on the measured data of the second laser scanner 2 is also carried out in this case.

It can be seen from FIGS. 2a to 2f that, due to the continuous availability of the longitudinal vehicle position during the passage of the laser scanner 2 scanning transversely to the traffic lane, an object representation which is correctly scaled in the longitudinal direction can also be determined, so that with the illustrated system for multi-lane Vehicles also any geometry-based classification tasks can be realized.

A measurement of length and longitudinal profile is meaningless for single-track vehicles, so that they can give way to the allocation of a standard length. Similarly, it is usually possible to proceed with very compact multi-lane vehicles which travel so far on the track edge that observation by the scanning in the direction of travel laser scanner is not possible. FIG. 3 shows, with reference to a flow chart, the cyclical sequence of the measurement, which is explained using the example of the vehicle passage shown in FIGS. 2a to 2f. In Figs. 2a to 2f, the so-called tracking corresponds to that of Figs. 3), the object areas indicated by rectangles in the X / Z plane 7, and the profile (left processing path in FIG. 3) of the object areas in the Y / Z plane 8 marked by rectangles ,

Initially there are no objects in the measuring range of the two laser scanners, the number of object representations 9 registered in the system is zero. After the threshold value criteria for the detection of a new object are fulfilled in preliminary profile 10, the new object is registered (11). A consideration of the object representations 9 and the current tracking 12 is required, since it can be determined in this way whether a new vehicle is actually in enters the observation area or whether a vehicle that pushes back or drives in the wrong direction of travel has been detected. Incidentally, object registration at 11 is also carried out to correctly treat vehicles arriving from the wrong direction later, if it is not detected in the observation area of the profile but for the time being only in the exit area (in tracking) taking into account predetermined minimum dimensions.

In the present case, the vehicle is first recognized in the profile and also detected in the subsequent measurement cycle of the other laser scanner 2, so that an assignment to the object representation produced (13) and also checked whether this laser scanner can actually track the vehicle reliably. This is only the case if the detected vehicle extends at the start of detection in the current profile over a defined tolerance range both left and right of the measurement plane of the laser scanner 2. In this case, an attribute is set (14) in the object representation, which distinguishes it as a "longitudinally traceable object", so that the further geometry measurement takes place taking into account both scanner data measured data of those objects, the attribute "longitudinally traceable object Otherwise, as long as the object can be observed by both the first laser scanner 1 and the second laser scanner 2, new geometry data is detected (14) for further processing if and only if exceeding of equidistant fixed longitudinal distance increments is detected. Accompanying it is also checked whether a minimum dimension of a possible towing vehicle has been reached, so that is set upon detection of smaller object areas. see Fig. 2b, an attribute "possible trailer tongue." with the further Vorwärtsbewe ^¬ supply of the vehicle is in the present Beispi el a later exceeding of a trailer finally transferred to an object property "vehicle with trailer" (14).

As long as a vehicle is detected in the measuring range of the first laser scanner 1, it is clear that it must extend at least until then. If a plurality of separate objects are first detected in the tracking, the provisionally created tracking is corrected (13) in such a way that the vehicle extends to the measurement plane of the first scanner 1. As soon as a vehicle apparently consisting of two objects has been combined once in the tracking from the point of view of the second laser scanner 2, the correct object assignment usually succeeds - by a constant overlapping of the individual objects with the then correct tracking from the previous cycle 15 - already during the preliminary determination of the current tracking 16 without subsequent corrective measures 13. Only in exceptional cases, for example if the trailer or the entire object temporarily disappears from the measuring range of the second laser scanner, appropriate corrective measures are required, which work based on already measured object properties 9. As soon as the vehicle has completely passed the measuring range of the first laser scanner 1, the vehicle measurement is completed. In the present case of an "object that can be tracked in the longitudinal direction", the current longitudinal position of the vehicle front is assigned as object length. In the underlying application example, a representative width and height value is determined from previously measured geometric data using familiar filter methods. Subsequently, a defined longitudinal position (longitudinal position of the light barriers 3, cf., FIGS. 1a-c) is achieved, at which the results of the vehicle measurement, provided with an incremental object number, are brought into a suitable form and output (17 ). Finally, the system is no longer found in the predefined active measuring range (see Fig. 2f), the associated object representation is deleted (18). The case study shows that the ongoing consideration of the dependencies between the measured data of the individual sensors and the plurality of already known object properties and internal states first of all a three-dimensional reconstruction of multi-lane vehicles and subsequently a reliable separation of vehicles also outside the measuring range of the first laser scanner. 1 ensures.

From FIG. 3 it can also be seen that, unlike tracking, a preliminary profile 10 is first determined without reference to the measurement from the previous cycle 19, 20, 15 and only later, taking into account the current tracking 12 and the old profile 20 an assignment of already registered objects 21 and a possible correction 22 are made.

FIGS. 4a to 4p show the principle of object recognition and object separation; A separation of vehicles behind and next to each other happens after initial registration by the local correlation of measurement data of successive sampling cycles. In the illustrated example, it is assumed that initially the number of registered objects 9 (Figure 3) is zero.

First, an object reaches the measurement plane of the transversely scanning laser scanner 1 (FIG. 4a). It is not yet registered (23), because the detected object has not yet exceeded a predetermined minimum dimension (see also measurement error in Fig. 4c). Once this criterion is met, an internal object representation 11 (Fig. 3) and 24 (Fig. 4p) and is applied and the measurement data acquisition is started. From this point in time, all measured data which have a common overlapping area in successive measuring cycles are assigned to the object 24.

In Fig. 4d, another object 25 is detected and treated in the same way. 4f shows that the objects 24 and 25 previously treated as separate objects evidently belong to one and the same vehicle, so that the previous object representations are combined to form a single object 24. the (see also 22, Fig. 3). In the further cycles (FIGS. 4g-4n), a separate object 26 is observed next to the object 24, which is finally treated as an object located next to object 24. To ensure that object areas of low or vanishing width (see Fig. 2b) have no overlapping area in the following cycle due to small lateral displacements, the valid search area is increased in such cases, cf. Fig. 4k.

A coherent object is thus detected in the measuring range of the first laser scanner 1 until no more object is found in the search range which results from previous measurements or until it is interpreted as being part of the other object by merging with another object , FIGS. 5a to 5h show the system behavior when another follows immediately after one object. A truck is, as already described, detected and measured by the system (Fig. 5a to 5d). In the measuring range of the second laser scanner 2 it can be seen that an object apparently connected to the front vehicle follows (5f). However, since the front vehicle no longer occupies the measuring range of the first scanner 1, it can be ruled out that this object is a part of this already detected vehicle. By the combined consideration of the individual data of the two scanners, an error-free object tracking can be realized (FIGS. 5g, 5h).

From the foregoing, it can also be deduced that for multi-lane vehicles, which initially enter the measuring range correctly, then reach the trigger line and finally leave the measuring range under observation by the second laser scanner 2 by pushing back the measuring range, a further information about this Push back an already issued object can be provided.

Drive motor vehicles from the wrong direction in the measuring range, so the direction of movement can first from the Occupancy order can be detected at the light barrier 3, multi-track vehicles can also be observed by the second laser scanner 2, so that after complete passage a message about a wrong passing vehicle can be issued.

In the case of narrow vehicles that pass off the measuring range of the second laser scanner 2, the output can not be made immediately when the vehicle leaves the measuring range of the first laser scanner 1, since at this time is not yet determined whether the detection on the first laser scanner 1 actually can be assigned to the wrong retracted vehicle. Only on the basis of an assessment during the subsequent vehicle passage can it be determined under typical conditions whether the one-lane vehicle actually passed the measuring range in the wrong direction.

For the correct handling of vehicles passing in the right direction, it is usually sufficient, on the basis of a sequential procedure (no overtaking), to recognize vehicles running behind each other at a defined longitudinal position. In the present implementation example, this can be done both on the basis of the data of the second laser scanner 2 and through the light barriers 3. A remaining fuzziness in this case is the lack of observability of side-by-side single-lane vehicles in the area of the light barriers. One possible solution is to output the measured data of single-lane vehicles immediately when several single-lane vehicles have retracted one after the other into the observation area, have already passed the measuring range of the first laser scanner 1 and the foremost single-lane vehicle has been detected at the trigger line.

In order to further reduce the uncertainties mentioned above, it is possible to proceed with equipment-related additional expenditure, but with a method which remains the same in its basic principle; for reliable detection in the wrong direction driving narrow vehicles can in the simplest case, for example, too an additional light barrier can be arranged at a small distance to the measuring plane of the first laser scanner 1 in order to determine the occupancy order in connection with the measuring plane of this laser scanner, and thus also to determine the fitting direction of a passing, narrow vehicle.

Figures 6a and 6b show the modular extensibility of the system by way of example. It is easy to see that by arranging another transverse scanning laser scanner 27, as an alternative or in addition to a light barrier 3, it can be ensured that the described vehicle separation can be repeated at each further point of the observation area and that already in the measuring plane the first transversely scanned laser scanner assigned object representations can be found again. Finally, for single-lane, side-by-side vehicles that are so similar in geometry that they can not be distinguished from one another in the detection area, it is irrelevant whether the object instances between the two real objects in the measurement area of the subsequent transversely scanning scanner were mistakenly traded.

It can be seen from FIGS. 1 a to 1 c that the measuring range of the laser scanner scanning in the longitudinal direction is limited at a predetermined mounting height. By attaching one or more laser scanners 28 (FIGS. 6a-b), an extension of the measuring range in the longitudinal direction can be realized.

Likewise, the tracking of even narrow multi-lane vehicles can be ensured by the system shown so far being extended by one or more laser scanning devices which scan in the longitudinal direction and which are arranged in different measurement planes 29.

If, in addition to the vehicle geometry, the number of axles of a vehicle is to be ascertained, suitable sensors, for example pressure sensors 30, can be introduced into the traffic lane for axle counting. By the one in the longitudinal Direction scanning laser scanner, the position and the state of motion of the vehicle are determined, whereby a robust evaluation of the measurement data of such sensors is possible.

It can easily be reconstructed that a measurement of a vehicle passing in the reverse direction is also possible without any further restrictions, for example by merging sections of a vehicle evaluated by the second laser scanner 2 as separate objects during the passage of the first laser scanner 1. If the system measures both in the planned entry and exit area with a cross-scanning laser scanner (Fig. 5a-h), the measure described above can be completely eliminated, especially since the relationship analysis described above for both directions basically runs in the same way. The invention is of course not limited to the illustrated embodiments, but includes all variants and modifications that fall within the scope of the appended claims.

Claims

Claims:

1. Method for geometrical measurement and tracking of objects (6), such as motor vehicles, moving on a roadway in the longitudinal direction thereof, such as motor vehicles, with the aid of at least two laser scanners (1, 2, 27, 28), which are each mounted above the roadway level and scan the roadway or an object (6) moving thereon within a limited measuring range in a measuring plane and generate a profile of the object in the measuring plane as measurement data of a scanning cycle, characterized in that the measuring plane of at least one first laser scanner (1, 27) is oriented essentially transversely to the carriageway and the measurement plane of at least one second laser scanner (2, 28) essentially in the longitudinal direction of the carriageway, and that the measurement data of the laser scanners are linked to form a time-related spatial representation of the objects.

2. The method according to claim 1, characterized in that the first laser scanner (1) seen in the object direction (5) is arranged in front of the second laser scanner (2) and that when the profile measured by it a predetermined threshold value criterion for the detection of a new object, this profile is registered as the front of a new object representation.

3. The method according to claim 2, characterized in that on the basis of the measurement data of the second laser scanner (2, 28) the object representations registered by the first laser scanner (1, 27) are verified and their movements are tracked.

4. The method according to claim 3, characterized in that on the basis of the measurement data of the first laser scanner (1, 27) the movements of the object representations tracked by the second laser scanner (2, 28) are verified for plausibility.

5. The method according to any one of claims 1 to 4, characterized in that measurement data from successive scanning cycles of the first laser scanner (1, 27), which have a common Show overlap area, be assigned to the same object representation.

6. The method according to claim 5, characterized in that for small object representations the possible overlap area is enlarged with a search area.

7. The method according to any one of claims 1 to β, characterized in that objects, the length of which cannot be determined with the second laser scanner (2, 28), are assigned a predetermined standard length.

8. The method according to any one of claims 1 to 7, characterized in that a plurality of first laser scanners (1, 27) spaced apart in the longitudinal direction of the road and / or a plurality of second laser scanners (2, 28) are arranged spaced apart in the transverse direction of the road.

9. The method according to any one of claims 1 to 8, characterized in that the direction of movement of the object representations is additionally detected and / or verified with the aid of light barriers (3).

10. The method according to any one of claims 1 to 9, characterized in that the number of vehicle axles of an object is determined with the aid of sensors in the roadway, preferably pressure sensors (30).

11. Device for geometrical measurement and tracking of objects (6), such as motor vehicles, moving on a roadway in the longitudinal direction thereof, such as motor vehicles, with at least two laser scanners (1, 2, 27, 28), which are each mounted above the roadway level and which Scan the roadway or an object (6) moving thereon within a limited measuring range in a measuring plane and generate a profile of the roadway in the measuring plane as measurement data of a scanning cycle, and with a computer system connected to the laser scanner for evaluating the measurement data, characterized in that the measuring plane of at least one first laser scanner (1, 27) essentially transverse to the carriageway and the measuring plane of at least one second laser scanner (2, 28) essentially in the longitudinal direction of the carriageway is oriented and the computer system links the measurement data of the laser scanners to a time-related spatial representation of the objects.

12. The apparatus according to claim 11, characterized in that the first laser scanner (1) seen in the object direction of travel (5) lies in front of the second laser scanner (2) and if the profile exceeds a predetermined threshold criterion for the detection of a new object, the Profile registered as the front of a new object representation in the computer system.

13. The apparatus according to claim 12, characterized in that the computer system uses the measurement data of the second laser scanner (2, 28) to verify the object representations registered by the first laser scanner (1, 27) and to track their movements.

14. The apparatus according to claim 13, characterized in that the computer system uses the measurement data from the first laser scanner (1, 27) to verify the plausibility of the movements of the object representations tracked by the second laser scanner (2, 28).

15. Device according to one of claims 11 to 14, characterized in that the computer system assigns measurement data from successive scanning cycles of the first laser scanner (1, 27), which have a common overlap area, to the same object representation.

16. Device according to one of claims 11 to 15, characterized in that the computer system for small object representations increases the possible overlap area with a search area.

17. Device according to one of claims 11 to 16, characterized in that the computer system objects whose

Length cannot be determined with the second laser scanner (2, 28), assigns a predetermined standard length.

18. Device according to one of claims 11 to 17, that a plurality of first laser scanners (1, 27) spaced apart in the longitudinal direction of the roadway and / or a plurality of second laser scanners (2, 28) are arranged at a distance from one another in the transverse direction of the carriageway.

19. The device according to one of claims 11 to 18, characterized in that the roadway is additionally equipped with light barriers (3) for detecting or verifying the direction of movement of the object representations.

20. Device according to one of claims 11 to 19, characterized in that the roadway is provided with sensors, preferably pressure sensors (30) for counting vehicle axles.