Abstract:
Control logics for the traffic-dependent controlling of traffic signal installations ( 1 ) are described with flow diagrams that become increasingly difficult to understand as phase sequences become more complex, and can only with difficulty be converted, in automated fashion, into traffic-oriented descriptions for signal programs. In a database data file ( 15 ), conditional equations (B 1 , B 2 , B 3 ) that compare traffic-oriented characteristic quantities with predetermined threshold values are stored together with actions (A 1 , A 2 , A 3 , A 4 ) for exchanging signal programs and together with rules (R 1 , R 2 , R 3 , R 4 ). The rules (R 1 , R 2 , R 3 , R 4 ) have control values and action directions (X). The control values are compared with truth values of the conditional equations, and, given complete agreement between the control values of a particular rule and the truth values, the action (A 1 , A 2 , A 3 , A 4 ) to which the action indication (X) of the particular rule (R 1 , R 2 , R 3 , R 4 ) refers is executed.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a method and apparatus for traffic-dependent controlling of means for controlling traffic. 
     Traffic-dependent traffic controlling takes place today for example via traffic signal installations, alternating traffic signs, changeable parking space information signs or radio announcements. The traffic-dependent data is obtained via traffic detectors such as induction loops, radar detectors, or infrared detectors. 
     For example, given traffic signal installations as means for controlling traffic, the phase sequences or signal sequences thereof are determined by predetermined signal programs. The signal programs can thereby be varied according to the selected control method. Thus, in traffic-dependent control methods, e.g. the time duration of the individual phases, the sequence of the individual phases and the number of different phases (given need-related requests) in the signal program are changed. In time-of-day-dependent control methods, different signal programs, and thus different phase sequences, are switched at fixedly predetermined times of day (e.g. in peak traffic hours). 
     For the selection of the signal program or, respectively, for the selection of the phase duration, the sequence of phases or the number of phases, traffic-related characteristic quantities are evaluated that are determined using the traffic detectors. In the case of a signal program with fixed times, the characteristic quantities are converted off-line during the design processing. In the case of a signal program adaptation or signal program formation, the characteristic quantities are processed continuously, with the possibility of a controlling alternating between traffic flow and signal controlling. The momentary signal programs are thereby calculated on-line and evaluated according to a predetermined control logic, on the basis of respectively updated characteristic quantities. With the aid of traffic detectors, occupation values are detected in the spatial surroundings of the traffic signal installations, from which values characteristic quantities of the traffic flow are derived. Characteristic quantities include for example the wait time of the vehicles at the traffic signal installation, the length of the traffic queue at the traffic signal installation, the traffic heaviness, i.e. vehicles per cross-section, travel speed, signaling (request) by pedestrians, cyclists and/or vehicles, degree of occupation, traffic density, degree of capacity utilization and the load quotient. Given a traffic-dependent signal program selection, the prepared characteristic quantities of the traffic flow are combined in the control logic for the selection of the signal programs with conditional equations and threshold values. 
     From the reference “Richtlinien für Lichtsignalanlagen” ((RiLSA)—Lichtzeichenanlagen für den Straβenverkehr—ed. 1992, published by the Forschungsgesellschaft für Straβen- und Verkehrswesen, Arbeitsgruppe Verkehrsführung und Verkehrssicherheit, pp. 46 to 47, as well as Appendix D, pp. 90 to 110), it is known how control logics are represented using flow diagrams. The phases and phase sequences of the traffic signal installation that are useful for the traffic-dependent controlling are thereby shown in a phase sequence plan. The exchange between the phases is defined precisely and is shown in comprehensible fashion in the phase transition. A flow diagram contains the logical and chronological conditions for the duration of the phases and for the switching of the phase transitions, and thus completely represents the sequence of the traffic-dependent controlling. Logical conditions thereby hold for the combination of the characteristic quantities of the traffic flow, and chronological conditions predetermine the chronological context of the program sequences, such as for example minimal and maximal clearance times of a signal group given free circulation time. Only a single flow diagram is thereby to be represented for all signal programs. This single flow diagram becomes increasingly difficult to understand as the complexity of the control logic increases, and a translation of the conditions prescribed in the flow diagram into a traffic-oriented description that a control apparatus of a traffic signal installation can interpret becomes increasingly difficult. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a method and apparatus for traffic-dependent controlling of means for controlling traffic, which are constructed so as to be able to be adapted to new traffic conditions with a low expense, and which permit simple conversion into a traffic-oriented specification. 
     In a common database data file there are stored the conditional equations, as well as actions that are to be executed upon a transition, located within a predetermined context, of a momentary state into an updated state better adapted to the momentary traffic flow, and rules that combine the conditional equations and the actions with one another. By means of this common storing in a predetermined database format, there results both an easily surveyable representation and also a common format for various changes between states. 
     In a preferred construction of the method, several database data files are combined with one another in order flexibly to handle complex sequences. 
     According to another embodiment, it is advantageously provided that fixed control hierarchies are constructed by means of predetermined processing sequences of various database data files. 
     The construction according to a further embodiment is particularly flexible, according to which the control hierarchies can be modified, in that within the database data files reference is made to database data files that do not follow directly in the processing sequence. 
     The method can advantageously be adapted to traffic conditions changed in this way, which can be taken into account only by means of a adaptation and/or selection of the control program located outside the predetermined context. The adaptation takes place in that the conditional equations, the rules and/or the actions of the database data files are modified and stored. 
     The method according to another embodiment can be adapted particularly well to the traffic conditions in that within the actions calculations are carried out whose results are taken into account in subsequent database data files of a processing sequence. 
     For traffic signal installations as means for controlling traffic, the momentary signal sequence (momentary signal program) as a momentary state is advantageously replaced by a further signal sequence (further signal program) as an updated state. 
     For traffic management systems as means for controlling traffic, the momentary control strategy as a momentary state is advantageously replaced by a further control strategy as an updated state. 
     The structure common to all database data files permits an implementation of the determination, described in the database data file, of the current control program by means of an algorithm that is common for all database data files. 
     A combination direction allocated to the actions is provided that, after the execution of the action, refers to a further database data file, in order advantageously to obtain, by means of a combination of database data files, an apparatus that is to be used flexibly for various traffic sequences. 
     In a further advantageous construction, in the database data files a combination direction to further database data files is contained, independent of the executed actions, whereby a fixed processing hierarchy of the database data files among themselves is achieved. 
     By means of the assembling of conditional equations by means of logical combinations of individual conditions and the logical combination thereof, complex control conditions can be combined in an easily surveyable, flexible manner. 
     For traffic signal installations as means for controlling traffic, the momentary signal sequence as a momentary state is advantageously replaced by a further signal sequence as an updated state. 
     For traffic management systems as means for controlling traffic, the momentary control strategy as a momentary state is replaced by a further control strategy as an updated state. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features of the present invention which are believed to be novel, are set forth with particularity in the appended claims. The invention, together with further objects and advantages, may best be understood by reference to the following description taken in conjunction with the accompanying drawings, in the several figures of which like reference numerals identify like elements, and in which: 
     FIG. 1 thereby schematically shows the construction of a traffic signal installation with traffic detectors; 
     FIG. 2 shows a schematic flow plan as used in the prior art for the control logic; 
     FIG. 3 schematically shows the construction of an inventive database data file with conditional equations, rules and actions; and 
     FIG. 4 schematically shows a processing sequence of several database data files. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a traffic signal installation  1  as an example of a means for controlling traffic. The method is also suited for alternating traffic signs, parking space information signs, or for determining detour measures or automatic radio announcements, as well as for money exchange are additional control strategies in traffic management systems. 
     In the traffic signal installation  1 , two light signal transmitters  2  are controlled via a control apparatus  3 , whereby the cable connections are arranged within a whip mast  4 , which serves at the same time as a fastening means for the light signal transmitters  2 . With the light signal transmitters  2 , the traffic is regulated on a first traffic lane  5  (e.g. into the city), which lane is divided from a second traffic lane  8  in the opposite direction (e.g. leaving the city) by a center stripe  7 . Two traffic detectors  10 , e.g. inductive loops, record occupation values of vehicles in a first measurement cross-section  6  on the first traffic lane  5  and in a second measurement cross-section  9  of the second traffic lane  7 , and send them to the control device  3 , in which characteristic quantities of the traffic flow on the first traffic lane  5  and the second traffic lane  8  are determined therefrom. With the aid of the determined characteristic quantities, the momentarily switched signal sequences (momentary signal program, momentary state) within the control device  3  are evaluated on the basis of the momentary traffic flow, and, by means of a control program in the control device  3 , if necessary a further signal sequence (further signal program, updated state) suited for the momentary traffic sequence is determined with which the traffic signal installation  1  is subsequently operated in order to achieve an improved traffic flow. Given traffic management systems as means for controlling traffic, momentary strategies as momentary states are analogously replaced by further control strategies that are better suited to the momentary traffic situation. 
     FIG. 2 shows a conventional flow diagram for the transition of a phase 1 into a phase 2, and from the phase 2 into a phase 3, whereby in phase 2 the vehicles on the first traffic lane  5  receive a clearance signal. The phase transition PU  1 , 2  from phase 1 to phase 2 thereby lasts 15 s, as is shown in an action element  11 . During phase 2, the time t, which elapses from the phase transition to phase 2, is measured, and is compared with the shortest time duration T 1  of the phase 2, as shown in a decision element  12  for chronological conditions. As long as the chronological conditional equation that the elapsed time t is greater than the shortest time duration T 1  receives the truth value ‘false’ or ‘no N,’ waiting takes place in a time loop  14 . The process continues only when the conditional equation, that the elapsed time t be greater than the shortest time duration T 1 , receives the truth value ‘true’ or ‘yes Y.’ For an adaptation of the clearance time in phase 2 that meets the requirements, in this example it is checked, in a logical conditional equation B, whether the time gap between two successive vehicles detected by the vehicle sensor  10  is greater than a given predetermined time, e.g. 2.5 s. This logical conditional equation B 1  is shown schematically in a decision element  13  for logical conditions. If this logical conditional equation receives the truth value ‘true Y,’ then on the basis of the low traffic density resulting therefrom the transition PU  2 , 3  is carried out from phase 2 into a phase 3, whereby the transition lasts 10 s. If the logical conditional equation B 1  receives the truth value ‘false N,’ then it is checked whether the elapsed time t since the phase transition to phase 2 is already greater than the longest time duration T 2  of phase 2. If this second chronological conditional equation receives the truth value ‘true Y,’ then the phase transition PU  2 , 3  from phase 2 to phase 3 is likewise introduced. If this second chronological conditional equation receives the truth value ‘false N,’ then in a further time loop, in a next time step, the logical conditional equation B 1  is again evaluated. For traffic signal installations that are more complex than described in this example, the flow diagram rapidly becomes difficult to understand, difficult to modify, and difficult to implement automatically into a traffic-oriented description that can be used in the control program of the control device  3 . 
     Analogously to the described transition between two phases, transitions between different signal programs are also shown dependent on the characteristics of the traffic flow. 
     For the specification of the inventive solution, in FIG. 3 it is assumed that a separate signal program is available for each of five different traffic situations. These are the following: a first situation S 1 : low traffic; a second situation S 2 : daytime traffic; a third situation S 3 : peak traffic into the city; a fourth situation S 4 : peak traffic away from the city; a fifth situation S 5 : balanced peak traffic. For the description of the traffic flow, individual conditions are used that place the determined characteristic quantities into relation with predetermined threshold values. In this example, the individual conditions are thereby a first individual condition b 1 , which states that the traffic heaviness in the first measurement cross-section  6  is greater than a threshold value of 800 vehicles per hour, a second individual condition b 2  stating that the speed in the first measurement cross-section  6  is less than the threshold value 30 km/h, a third individual condition b 3  stating that the traffic heaviness in the second measurement cross-section  6  is greater than 800 vehicles per hour, and the one individual condition that states that the speed in this second measurement cross-section  8  is less than 30 km/h. If the first and second individual conditions b 1 , b 2  are fulfilled for the first measurement cross-section  6 , this corresponds to a peak traffic directed into the city, which is described by the second conditional equation B 2 . Correspondingly, fulfillment of the third and of the fourth individual condition b 3 , b 4  for the second measurement cross-section  9  means that there is a peak traffic flow coming out of the city, described in the third conditional equation B 3  by an AND combination of the third and the fourth individual condition b 3 , b 4 . The first conditional equation B 1  describes a balanced peak traffic flow, characterized in that all four individual conditions are fulfilled. The conditional equations are stored in a first field of a database data file  15  as a decision table, based in this example on the momentarily switched third situation S 3 . The possible actions for the signal program selection are thereby stored in a second field of the database data file  15 . FIG. 3 concerns a first action A 1  in which the fifth situation S 5  (balanced peak traffic) is switched, a second action A 2  in which the selected signal program for the third situation S 3 : peak traffic flow into the city is further maintained, a third action A 3 , in which switching takes place into the fourth situation S 4  (peak traffic flow out of the city), and a fourth action in which switching takes place into the second situation S 2  (daytime traffic). The selection of the actions A 1 , A 2 , A 3 , A 4  takes place with the aid of rules R 1  . . . R 4 , stored in a third field in the database data file  15 . The rules R 1  to R 4  thereby consist of control values and action directions. In each rule a control value is thereby allocated to each condition, which value indicates whether the condition has to assume the truth value ‘true Y,’ the truth value ‘false N’ or an arbitrary truth value ‘−’, so that the action corresponding to the action indication is executed. FIG. 3 shows that in the first rule R 1  the first conditional equation B 1  must receive the truth value ‘true Y,’ the truth values of the two other conditional equations B 2 , B 3  are not taken into account, and that the action indication X then indicates the first action A 1 , with which switching takes place into the balanced peak traffic. The second rule specifies that for the case in which the first conditional equation B 1  assumes the truth value ‘false N,’ the second conditional equation B 2  assumes the truth value ‘true Y,’ and the third conditional equation B 3  assumes an arbitrary truth value, the action direction X indicates the second action A 2 , in which the signal program remains switched for the peak traffic directed into the city. The third rule R 3  indicates, with its action indication X, the third action A 3 , in which switching over takes place to the peak traffic flow directed out of the city, if the first and the second conditional equations B 1 , B 2  receive the truth value ‘false N’ and the third conditional equation B 3  receives the truth value ‘true Y.’ In the fourth rule R 4 , an action direction X to the fourth action A 4  is shown, in which switching takes place into the second situation S 2 , which action is carried out when all conditional equations B 1 , B 2 , B 3  receive the truth value ‘false N.’ In a fourth field, a combination action V is stored that contains further steps that are to be carried out after the executed action. In this example, the processing is terminated by an abort indication E (Exit). 
     FIG. 4 shows how, by means of combination actions V, a module-type assembling of several database data files D 1  . . . D 4  is achieved after processing of the actions A 1  . . . A 4 . A fixedly predetermined processing sequence  20  is thereby defined in which the individual database data files D 1  . . . D 4  are brought into a fixed sequence as a control hierarchy. First a third database data file D 3 , then a second database data file D 2 , then a first database data file D 1 , and finally a fourth database data file  4 , are hereby processed. The combination actions V in the individual database data files D 1  . . . D 4  thereby also permit modification of the fixedly predetermined processing sequence  20 . Thus, for example, in the third database data file D 3  a possibility of jumping ahead directly to the fourth database data file D 4  is represented, and in the second database data file D 2  the control program is terminated directly after processing of the second database data file D 2 , by means of the abort indication E. In the normal case, the database data files D 1  . . . D 4  are processed in the processing sequence  20 , as indicated by the combination action  21  to the address of the subsequent table. 
     For an adaptation to traffic conditions changed in such a way that they can no longer be controlled within the predetermined context with the aid of the additional signal sequence, in the database data files  15  the conditions, the rules, the actions, the combination actions or the processing sequences are to be adapted if warranted. As indicated in FIG. 3, individual conditions b 1 , b 2 , b 3 , b 4  can thereby be combined to form conditional equations by means of Boolean operators. Within the actions, calculations can also be carried out that are accessed in later database data files  15  of a processing sequence  20 . By means of the identical structure of different database data files  15 , it is also possible to indicate an algorithm that is common for all database data files  15 , with which the contents of the database data files  15  are implemented into a traffic-oriented description for the control apparatus  3 . 
     The inventive method can analogously be carried over to traffic management systems in which, on the basis of occupation values, momentary control strategies are replaced by further control strategies that are then realized by means of detour measures, modified indication of alternating traffic signs, or parking space information signs, or by means of radio announcements. 
     The invention is not limited to the particular details of the method and apparatus depicted and other modifications and applications are contemplated. Certain other changes may be made in the above described method and apparatus without departing from the true spirit and scope of the invention herein involved. It is intended, therefore, that the subject matter in the above depiction shall be interpreted as illustrative and not in a limiting sense.