Abstract:
In a method and an apparatus for identifying through traffic, entry into and exit from a predefined area are ascertained and the transit time is used to determine whether unauthorized transit through the area has occurred.

Description:
FIELD OF THE INVENTION 
     The present invention relates to methods and apparatuses for identifying through traffic. 
     BACKGROUND INFORMATION 
     For a variety of traffic categories, for example heavy loads, hazardous cargo, or heavy transports, certain roads and areas are, for various reasons (e.g. environmental reasons) closed to through traffic. These closures can be valid for a limited time, for example only for certain days of the week and/or for certain hours of the day. Corresponding traffic signs are provided for in German road and traffic legislation. At present, checks that such prohibitions are being observed are made in particular by laborious traffic inspections. 
     On the other hand, there exist proposals in conjunction with the charging of fees for the use of roads subject to fee, for example from European Published Patent Application No. 0 741 373, according to which stations are provided, at least upon entry into and/or exit from the area subject to fee, which recognize the passage of a vehicle and with which a unit installed in the vehicle communicates in order to calculate the fee amount. 
     SUMMARY 
     A procedure is described below that detects, in particularly advantageous fashion, whether a vehicle is transiting through an area closed to the vehicle, or whether the vehicle constitutes delivery or resident traffic. This is achieved by a detection algorithm that proceeding from a typical transit time, which preferably is a function of the vehicle type and/or time of day and/or a property of the area (e.g. number of settlements, intersections, road types). If this transit time or a reference value derived therefrom reaches or falls below a typical value, a potential violation exists, whereas if the transit time or reference value derived therefrom is exceeded, then resident or delivery traffic is probably involved. 
     The aforementioned automatic through traffic detection system is preferably arranged in a vehicle device, i.e. in a device that is installed in a vehicle. An algorithm derived from the aforementioned procedure executes in the vehicle terminal device. This device monitors areas and times, and transmits a corresponding datum when a potential violation of a traffic prohibition can be assumed. 
     It is of considerable advantage that execution of the detection algorithm occurs locally, so that data transfer is considerably reduced and considerable reliability is obtained; and that a communication from the vehicle to a central unit takes place only in the context of an appropriate result. 
     In particularly advantageous manner, a vehicle terminal device of this kind, whether in conjunction with a toll utilization or as a driver information or navigation system, possesses the necessary technical equipment to carry out the through traffic detection function, so that the outlay for implementation can be minimized. 
     Advantageously, the necessary data with regard to transit times, entry and/or exit points, etc. are stored in a protected memory region of the vehicle terminal device, changes or additions being made from outside by an update of the data. Depending on the arrangement, individual restricted areas or a plurality thereof are stored in memory. 
     The procedure presented is advantageously usable not only to distinguish through traffic from resident or delivery traffic, but also to detect whether hazardous-goods and/or heavy transports are passing through prohibited areas or deviating from predetermined routes. 
     Advantages are evident from the description below of exemplifying embodiments. 
    
    
     DETAILED DESCRIPTION 
     Example embodiments of the present invention will be further explained below with reference to the drawings.  FIG. 1  shows, with reference to a schematic sketch, the basic procedure for through traffic detection, whereas  FIG. 2  depicts an exemplifying embodiment of an apparatus for automatic through traffic detection that is installed in the motor vehicle.  FIG. 3  sketches, on the basis of a flow chart, an example embodiment of the computer program executed in the vehicle terminal device for automatic through traffic detection.  FIG. 4  is a table for reference transit times of a fictitious area. 
       FIG. 1  depicts, for example, an area  10  that is closed to through traffic, in particular to certain classes of vehicle such as, for example, heavy-load traffic. The area has various roads  12 ,  14 ,  16  passing through it, and comprises various entry and exit points (A-F). 
     For automatic through traffic detection, passage past an entry point A-F and passage past one of the exit points A-F of the restricted area is detected in the terminal device installed in the vehicle. This is accomplished, in the example embodiment, on the basis of a position determination system of the vehicle, for example based on GPS or Galileo signals. In other exemplary embodiments, apparatuses (e.g. beacons) with which entry and exit of a vehicle is detected are present at the entry and exit points. Further alternatives encompass other position determination methods such as, for example, dead reckoning methods. 
     In addition to passage past entry and/or exit points of a restricted area, a determination is made of the presence time spent by the vehicle in this area delimited by the entry and exit points. This transit time is compared a stored reference time for the route between the entry and exit point. If this reference time is exceeded, it is assumed that delivery or resident traffic was in fact involved, whereas if the time falls below that value, it is apparent that a violation against the transit prohibition exists. 
     In the exemplifying embodiment, the reference value depends on a variety of factors. A specific transit time that is typical for the restricted area is defined, for example, for every possible combination of entry point and exit point. The reference value is also, depending on the embodiment, defined as a function of factors such as vehicle type (e.g. car, truck, motorcycle) and/or time of day (night, rush hour, etc.) and/or properties of the area (number of intersections, towns, etc.). 
     If the vehicle&#39;s measured presence time in an area reaches or falls below the reference transit time in that area, this constitutes a potential violation, since resident and delivery traffic has longer travel times for the area. 
     The reference transit time can also be dependent on the direction of travel, since the transit time can be different in each direction because of slopes or a different number of traffic signals. For example, a trip from A to B may have a different typical transit time than a trip from B to A. 
       FIG. 4  depicts an example of a table of reference transit times (in minutes), stored in the memory of the vehicle terminal device, for an area as sketched in  FIG. 1 . 
       FIG. 2  shows a terminal device  20  that is installed in the vehicle and serves to carry out the through traffic detection algorithm as outlined above. Vehicle terminal device  20  has a computer element  22  that has at least one memory  24  as well as input and output wiring  26 . The terminal device furthermore encompasses at least one position determination system  28 , for example a GPS system, that receives the signals necessary for position determination via an antenna  30 , and ascertains the vehicle position from these signals. A further constituent of the vehicle device is a communication unit  32 , for example a communication unit to a mobile radio network (e.g. GSM, GPRS, UMTS), and/or a short-range communication connections such as, for example, WLAN, infrared, Bluetooth, DECT, DSRC, etc. The apparatus depicted in  FIG. 2  can be a unit used specifically for through traffic detection, or can be a device that is already present, e.g. a telematics device, a tolling device, a navigation device, etc., or a part of such a device. 
     The coordinates of the entry and exit points of areas closed to through traffic are stored in the memory of this unit, preferably as geographical coordinates (longitude, latitude, plus capture radius in each case). When the vehicle drives through an entry point into the restricted area, its passage past the entry point is sensed on the basis of a comparison of the measured vehicle position and the stored position value range of the entry point. The time spent by the vehicle in the area since the entry point, and/or the positions of the vehicle, are then automatically sensed and stored in the internal memory. When the vehicle reaches an exit point (which, as depicted, is ascertained in conjunction with the entry point), the presence time between passing the entry point and reaching the exit point is then ascertained, and is compared with a reference transit time stored for that route of travel. The reference transit times are stored in the memory as a table. If the measured presence time is less than or equal to the predetermined reference time, which in the exemplifying embodiment is made up of a reference transit time plus a reserve time, then a violation of the through traffic prohibition exists with high probability. 
     The vehicle identification number, the times at which the entry and/or exit point is passed, and/or the vehicle trajectory (track) also recorded on the basis of the acquired positions are then, if applicable, compressed and/or coded in the vehicle device, and transmitted via the communication unit to a monitoring center. 
     If the measured travel time is greater than the reference time, then resident traffic or delivery traffic is present with high probability. In this case two variants for a further procedure are possible. It can be essentially be assumed that with such a constellation, there is no violation of the through traffic limitation. The result is that if the through traffic limitation is disregarded and the reference time is exceeded, for example, because of a traffic jam, accident, stoppage, etc., this disregard will not be detected. Communication costs to the center are not incurred. Another variant is that the aforementioned data are transmitted, optionally in compressed and/or coded fashion, to the monitoring center via the communication unit, and a decision is then made in the monitoring center, based on the route of travel, as to whether or not a violation of the transit limitation exists. 
     Both the entry and exit points and the reference transit time are updated via the communication interface of the vehicle device. 
     Additionally or alternatively, in an example embodiment, updating of these data via the communication interface is performed dynamically, i.e. as a function of time of day and/or current traffic conditions. In the case of, for example, areas that are closed as a function of time of day, the data are loaded into the vehicle device&#39;s memory only during the corresponding time period. Additionally or alternatively, when traffic jams are reported in an area, the reference times in that area are adapted on the basis of these traffic jam reports, and updated via radio. 
     The area and reference-time data are stored in manipulation-proof fashion in the vehicle device&#39;s memory. Depending on the size of the vehicle device&#39;s memory, a predetermined number of areas having transit limitations are kept on hand. 
     The aforementioned arrangement for automatic through traffic detection is also used to detect hazardous goods traffic in areas closed to hazardous cargo (e.g. because of tunnels or for watershed protection). Geographic data for the corresponding restricted areas are then provided in the terminal device of the hazardous goods transporter. As presented above a message is sent when transit through such an area is detected. In an example embodiment, the reference time for such areas is set to a very high value, so that any passage (even with a break) generates a message. 
     It also becomes possible to detect heavy transports on roads that have not been registered for heavy transport. Here as well, the areas that are restricted, i.e. are located outside the registered road network, are programmed into the vehicle unit via geographic data. Entries into and exits from such areas are logged as set forth above, and messages are sent. 
     In another example embodiment, the aforementioned procedure is utilized inversely. The registered route is programmed in as an area, a reference time is predefined, and the presence time in the area is acquired. If the presence time is greater than or less than the reference time plus a grace period, a message is sent. 
       FIG. 3  shows an example embodiment of the procedure presented above, as a computer program. The program is executed at predetermined time intervals, for example several milliseconds, and runs in the vehicle terminal device. 
     After the program starts, in the first step  100  the vehicle&#39;s current position is sensed by the position determination unit. In step  102  is then compared with the stored positions of entry and exit points of restricted areas, preferably only those adjacent to the current position. If the measured position corresponds to an entry point, or if the position is located in the capture region of an entry point, the program continues with step  104 ; otherwise step  100  is repeated. 
     If step  102  detects that the vehicle is driving into a restricted area, then in step  104  a timer T is started. In addition, in order to prevent an entry point from being detected more than once, a marker is set for the entry point, preventing the same entry point from being detected a second time in another program cycle. The vehicle&#39;s position value is also stored. In the next step  106 , the vehicle&#39;s position is determined again, and step  108  checks whether the position is located within the capture region of a predetermined exit point of the area in which the vehicle is located. If not, the program repeats with step  106 . The exit points checked in step  108  are all exit points of that area. If an exit point is detected in step  108 , timer T is stopped in step  110 . In step  112 , the reference time Tmax is then read out from the table in memory for the predetermined route, along with (if applicable) the vehicle type, direction of travel, time of day, weather conditions, etc. The following step  114  checks whether the measured time T is greater than the reference time. If so, step  116  detects that resident or delivery traffic was apparently involved, whereas in the opposite case, a transmission of predetermined data to a monitoring center is initiated in step  118 . After step  116  or  118 , the program repeats in step  100 .