CN116884245B - Intersection time period division method based on lane flow and grade interval - Google Patents
Intersection time period division method based on lane flow and grade interval Download PDFInfo
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Abstract
The invention discloses a method for dividing intersection time period based on traffic lane flow and a grade interval, which comprises the following steps: s1, calculating the single-lane subinterval average flow of each traffic flow at an intersection; s2, setting a flow grade interval, and generating a flow grade of the traffic flow according to the average flow of the traffic flow in the single-lane subinterval; s3, determining each phase interval of the intersection and a corresponding traffic flow chain according to the phase structure of the intersection; s4, generating a time interval division scheme of the phase interval according to the flow grade of each traffic flow in the phase interval; s5, generating a time division scheme of the intersection according to the time division scheme of each phase interval of the intersection. The invention utilizes the single-lane subinterval average flow and the grade interval of each strand of traffic flow of the intersection, and carries out time interval division according to the flow grade of the traffic flow chain of the phase interval, thereby providing a proper time interval division scheme for the signal control design of the intersection.
Description
Technical Field
The invention relates to the technical field of intersection time period division, in particular to an intersection time period division method based on lane flow and a grade interval, and belongs to the technical field of road traffic signal control.
Background
Traffic signal control plays an important role in ensuring the safe and orderly operation of each traffic flow at an intersection. Because urban traffic demand is relatively fixed within a period of time, traffic flow at intersections usually presents certain regularity characteristics, such as the occurrence of early and late peaks, daytime peaks, nighttime peaks and corresponding traffic flow are relatively stable, so that multi-period timing control is still a signal control mode commonly used for single intersections, and how to reasonably divide a day into a plurality of periods and design a corresponding signal timing scheme for each period is a key for improving the signal control benefit of the intersections.
In the aspect of theoretical research, students usually adopt a data cluster analysis means to design a time period division scheme by utilizing total arrival flow or other operation indexes of an intersection, the division effect of the method has strong dependence on the number of clusters and classification decision, and the conventional method usually considers the total flow of the intersection and cannot combine the traffic flow, the phase design and the traffic demand of non-critical traffic flow to divide the time period, so that the method is rarely applied in practice. In terms of engineering practice, traffic engineers typically divide a day into a plurality of time periods by experience according to the overall condition of traffic flow at intersections, including, for example, night, early peak, flat peak, noon peak, flat peak, late peak, flat peak and corresponding transition time periods, and this division method has a certain subjectivity and is difficult to popularize.
Therefore, according to the lane flow and phase structure of the intersection, the flow grade interval is reasonably set by analyzing the relation between the arrival flow and the passing time demand, and the traffic change condition of each strand of traffic flow is considered, so that an intersection time interval dividing method based on the lane flow and the grade interval is formed, technical support can be provided for urban traffic signal control design, and the method has important research significance and application prospect.
Disclosure of Invention
The invention aims to overcome the defects and shortcomings of the prior art, and provides a method for dividing the time period of an intersection based on traffic flow and a grade interval, which can carry out multi-time division scheme design according to the change of the demand of each traffic flow of the intersection on the passing time, and can be free from the restriction of the condition of the formation of the intersection and the phase design.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
the invention provides a method for dividing intersection time period based on traffic lane flow and grade interval, which comprises the following steps:
s1, calculating the single-lane subinterval average flow of each traffic flow at an intersection;
s2, setting a flow grade interval, and generating a flow grade of the traffic flow according to the average flow of the traffic flow in a single lane subinterval;
s3, determining each phase interval of the intersection and a corresponding traffic flow chain according to the phase structure of the intersection;
s4, generating a time interval division scheme of the phase interval according to the flow grade of each traffic flow in the phase interval;
s5, generating a time division scheme of the intersection according to the time division scheme of each phase interval of the intersection.
As a preferential technical solution, step S1 specifically includes:
defining the traffic flow running on one lane group as one traffic flow, wherein the number of lane groups contained in one intersection is the number of traffic flows in the intersection; setting a subinterval as m minutes, wherein the value of m is considered to avoid the instant influence of an upstream intersection signal timing scheme and reflect the continuous change rule of the arrival flow in time; and converting the subinterval flow of each lane group of the intersection into the single-lane subinterval average flow of the lane group to obtain the single-lane subinterval average flow of each traffic flow of the intersection.
As a preferential technical solution, the method further comprises the following steps:
the resulting single lane subinterval average flow of each stream is smoothed, including but not limited to a sliding average method and an exponential sliding average method.
As a preferential technical solution, step S2 specifically includes:
s201, setting a flow grade interval;
the flow class section consists of a group of continuous sections capable of covering the intersection flow change section, such as [0, q ] 1 )，[q 1 ，q 2 )，[q 2 ，q 3 ) ,. the length of each section is determined by setting a threshold for the change in the green-to-green ratio of each stream, and for flow class sections Δq of equal section length, the calculation method is as follows:
wherein q n The nth traffic class interval upper limit and the (n+1) th traffic class interval lower limit are given in units of vehicles/hour；q n-1 The upper limit of the nth-1 flow grade interval is the lower limit of the nth flow grade interval, and the unit is vehicle/hour; q 0 =0; delta n is a change threshold value of the number of vehicles arriving in a single lane in one period; c is the period duration of the intersection signal, and the unit is seconds; q s The unit is vehicle/hour, which is the saturation flow of a single lane; Δt is the change threshold of green time of one period, and the unit is seconds; Δλ is the threshold of change in traffic flow green to signal ratio;is an upward rounding operation;
s202, generating a traffic flow grade of a traffic flow;
determining the flow grade of the average flow of each traffic flow in a single-lane subinterval according to the flow grade interval; in order to avoid the adverse effect of instantaneous fluctuation of the flow on the time division, the duration of the flow class of the vehicle flow is set to at least n P For m minutes, so that there is at least n P The successive subintervals correspond to the same traffic class; dividing the average flow of the single-lane subinterval of the traffic flow calculated in the step S1 into different flow grades, wherein the number of continuous subintervals is smaller than n P Is modified to ensure that all levels last at least n continuously P Sub-periods.
As a preferred embodiment, in step S201:
setting the same green signal ratio change threshold value for each interval, thereby obtaining a group of flow grade intervals with equal interval length; or different green-to-signal ratio change thresholds are taken for each section to adapt to actual traffic demands, so that flow grade sections with different section lengths are obtained.
As a preferential technical solution, step S3 specifically includes:
defining the time when all traffic flows which are controlled by signals and have right of passage finish passing simultaneously as phase partitions, wherein two adjacent phase partitions form a phase interval, and the number of the phase intervals of the intersection is equal to the number of the phase partitions because the traffic right conversion of the intersection has periodicity; the traffic flows which successively acquire the right of passage in one phase interval form a traffic flow chain, and the same phase interval possibly comprises a plurality of traffic flow chains which share the same passage time.
As a preferential technical solution, step S4 specifically includes:
traversing all subintervals according to time sequence aiming at each phase interval, and judging whether the current subinterval needs to be switched into a new phase interval control interval or not by comparing the flow grade change condition of the traffic flow; the control period dividing scheme of each phase interval is relatively independent, and the dividing process is carried out in the phase interval; let the current subinterval sequence number be i,the sequence number of the control period is j, the subperiod set contained in the control period is S (j), and the initial value of the subperiod set is an empty set;
s401, calculating the flow grade of a key traffic chain in the subperiod i;
the flow grade of the traffic flow chain is the sum of the flow grades of all traffic flows in the traffic flow chain, and the calculation formula is as follows:
wherein R is Ll (i) For the first traffic chain L in the phase zone l Flow level at subinterval i; r is R f (i) The flow level of the traffic flow f in the subinterval i;
traffic class R of critical traffic chain K (i) The flow class maximum value of all traffic flow chains in the phase interval in the subperiod i is calculated as follows:
R K (i)＝max{R Ll (i)}
s402, calculating the maximum flow levels of all traffic flow chains in the current control period j;
calculating the flow grade of each flow chain in the current control period j, taking the sum of the historical maximum flow grades of each flow in the flow chain in the current control period as the flow grade of the flow chain, wherein the calculation formula is as follows:
wherein R 'is' f (j) Historical maximum flow level for flow f over control period j; r's' Ll (j) Traffic chain L for control period j l Is a flow rate class of (2);
further, the maximum flow rate grade R 'of all the traffic flow chains in the current control period j is obtained' K (j) The method comprises the following steps:
R′ K (j)＝max{R′ Ll (j)}
s403, judging whether the sub-period i needs to be switched to a new phase interval control period;
firstly, judging whether the demand of a key traffic chain on the passing time is obviously changed, namely comparing whether the flow levels of the key traffic chain in the current subperiod and the key traffic chain in the previous subperiod are equal;
if not, the traffic time requirement of the key traffic flow chain on the phase interval is obviously changed, and the key traffic flow chain needs to be switched into a new phase interval control period, and meanwhile, S (j) and S (j+1) are updated:
S(j)＝S(j)-{i}
S(j+1)＝S(j+1)∪{i}
if the traffic time requirements of the key traffic chain on the phase section are equal, namely the traffic time requirements of the key traffic chain on the phase section are kept unchanged, at the moment, whether the traffic time requirements of all traffic flows in the phase section in the control period S (j) can meet the requirements is judged, namely the maximum flow level R 'of all traffic flow chains in the current control period j is compared' K (j) Whether the flow level of the key traffic chain is larger than the subinterval i;
if the signal is larger than the threshold value, it indicates that when the same signal control scheme is executed in the sub-period i and other sub-periods in the control period j, the passing time requirement of at least one traffic flow in a certain sub-period is not satisfied, so that the control period needs to be switched to a new phase interval control period, and S (j) and S (j+1) are updated simultaneously:
S(j)＝S(j)-{i}
S(j+1)＝S(j+1)∪{i}
if not, the phase interval control period is not required to be switched into a new phase interval control period;
repeating the steps until all the sub-periods have the phase interval control period.
As a preferred technical solution, in step S402, before calculating the flow level of the critical traffic flow chain of the current control period j, the current control period j is first updated, that is, the subperiod i is incorporated into the subperiod set S (j):
S(j)＝S(j)∪{i}。
as a preferential technical solution, step S5 specifically includes:
combining the control time periods of each phase interval of the intersection in the same subinterval into a vector, and sequentially arranging according to the subinterval serial numbers:
V i a time period vector of the intersection in the subperiod i; element a in a period vector p (i) The control period of the p-th phase interval of the intersection in the subperiod i is adopted; p is p * The phase interval number of the intersection;
when the vectors of adjacent two periods are unequal, i.e. V i ≠V i-1 Indicating that at least one phase interval requires a switching control scheme; meanwhile, considering that the signal timing scheme of the intersection is not suitable for frequent switching, setting the duration of one control period of the intersection to be at least n Q M minutes, i.e. one control period of the intersection contains at least n Q Sub-periods; thus, when V i ≠V i-1 And the duration of the control period is greater than n Q Regenerating a control period empty set at m minutes, and incorporating a sub-period i therein; otherwise, sub-period i is incorporated into the current control period set.
As a preferred technical solution, step S5 further includes the following steps:
and traversing all the subintervals in sequence, and repeating the step S5 until all the subintervals have the corresponding intersection control intervals.
Compared with the prior art, the invention has the following advantages and beneficial effects:
1. the method comprehensively considers the influence of the flow changes of the key traffic flows and the non-key traffic flows on the time division, generates the time division scheme of the intersection on the basis of obtaining the time division scheme of the phase interval, fully considers the requirements of each traffic flow on the passing time, and improves the fineness of the time division scheme of the intersection.
2. The invention sets up the relation between the length of the flow grade interval and the green signal ratio change threshold value, so as to set the length of the flow grade interval reasonably according to the actual demand in practical application, and provide objective basis for the design of time interval dividing scheme.
3. According to the invention, the average flow of the single-lane subperiod is used as the basis of time division, so that the influence of different canalization conditions on the time division scheme of the intersection is avoided, the traffic flows of the intersections of different types can adopt the same time division standard, and the design flow of the time division scheme is unified.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of a method for dividing intersection time period based on traffic lane flow and level intervals according to an embodiment of the invention;
FIG. 2 is a schematic illustration of an intersection canalization design in accordance with an embodiment of the present invention;
FIG. 3 is a schematic diagram of a phase sequence design of an intersection according to an embodiment of the present invention;
FIG. 4 is a timing chart comparing average flows of single-lane sub-periods before and after a cross road west straight traffic smoothing process according to an embodiment of the present invention;
fig. 5 is a timing chart of average flow of single-lane subintervals after the smoothing process of each strand of traffic flow at the intersection according to the embodiment of the invention.
Detailed Description
In order to enable those skilled in the art to better understand the present application, the following description will make clear and complete descriptions of the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. It will be apparent that the described embodiments are only some, but not all, of the embodiments of the present application. All other embodiments, which can be made by those skilled in the art based on the embodiments herein without making any inventive effort, are intended to be within the scope of the present application.
Reference in the specification to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Those of skill in the art will explicitly and implicitly understand that the embodiments described herein may be combined with other embodiments.
The intersection of Buddha city Wenhua road and megaauspicious road is selected as an example intersection, the intersection consists of four entrance roads including 1 right-turning lane, 3 straight-going lanes and 2 left-turning lanes, as shown in fig. 2, wherein the saturated flow of each entrance lane is 1650pcu/h, and the right-turning lanes are not controlled by signals, so that the intersection does not participate in time division. The intersection is released in a lap joint manner as shown in fig. 3. Fig. 1 is a main flow of an intersection time period dividing method based on a lane flow and a level interval, which is adopted in the present embodiment, and specific implementation steps are as follows:
step one, calculating the single-lane subinterval average flow of each traffic flow at the intersection.
The design of the intersection is known that each entrance road of the intersection comprises 1 straight lane group consisting of 3 straight lanes and 1 left-turning lane group consisting of 2 left-turning lanes, namely each entrance comprises 1 straight traffic flow and 1 left-turning traffic flow. One sub-period is set to 5 minutes, and the entire day includes 288 sub-periods in total. Based on intersection bayonet data, calculating sub-period flow of each lane of an intersection, carrying out grouping summation on each lane according to the affiliated lane groups, and converting the grouping summation into single-lane sub-period average flow of each lane group of the intersection to obtain the single-lane sub-period average flow of each traffic flow of the intersection.
In order to avoid the influence of signal period setting on the statistics of the subinterval flow, a sliding average method is selected to carry out smoothing processing on the obtained single-lane subinterval average flow of each strand of traffic, the size of a smoothing window is 3, and the subsequent calculation is based on the flow data after the smoothing processing.
q f (i) F epsilon { ws, wl, ss, sl, es, el, ns, nl } is the single lane average flow of the traffic flow f in the sub-period i, q' f (i) F epsilon { ws, wl, ss, sl, es, el, ns, nl } is the single-lane average flow of the traffic flow f after the smoothing of the subinterval i.
Taking the west straight traffic as an example, the calculation result of the average flow of the single-lane subinterval before and after the smoothing process is shown in fig. 4. And (5) calculating the average flow of each strand of traffic flow at the intersection in a single lane subperiod after the smoothing treatment, as shown in fig. 5.
Setting a flow grade interval, and generating the flow grade of the traffic flow according to the average flow of the traffic flow in the single-lane subinterval.
For convenience, the same green-signal ratio change threshold is set for each section, so that a group of flow grade sections with equal section length are obtained, the green-signal ratio change threshold delta lambda=7.5% of each traffic flow is set, so that the flow grade section delta q=124 vehicles/hour is calculated, and for convenience in calculation, the actual length of the flow grade section is set to be 120 vehicles/hour. The average flow rate of each single-lane subinterval of each traffic flow at the intersection is not more than 300 vehicles/hour, so that three level intervals [0, 120 ], [120, 240 ]), [240, 360] are set to cover the variation interval of the flow rate.
According to the flow level interval, the flow level of the average flow of each traffic flow in the single-lane subinterval can be determined. To avoid the adverse effect of instantaneous fluctuations in flow on the division of time, the flow class duration of the traffic flow is set to be at least 3 and 5 minutes, so that at least 3 consecutive subintervals correspond to the same flow class. After dividing the average flow of the single-lane subinterval of the traffic flow calculated in the step Sl into different flow grades, correcting the grade with the continuous subinterval number smaller than 3 so as to ensure that all grades continuously last for at least 3 subintervals. The correction method can be as follows: and regarding 3 or more adjacent subintervals in the same level as a subinterval set, and when there is a subinterval without attribution between the two adjacent subinterval sets, averaging and rounding the flow levels of the subintervals. When the number of the non-attributive subintervals is smaller than 3, comparing the distance between the flow level obtained by averaging and the flow level of the front subinterval set and the rear subinterval set, and correcting the flow levels of the subintervals to the flow level of the subinterval set with a closer distance; when the number of the non-attributive subintervals is more than or equal to 3, the flow levels of the subintervals are corrected to be the value obtained by averaging and rounding.
Taking the single-lane subinterval average flow of the west straight traffic as an example, the calculation process for explaining the steps is shown in the following table:
TABLE 1 grade correction procedure for West straight ahead flow (ws)
And thirdly, determining each phase interval of the intersection and a corresponding traffic flow chain according to the phase structure of the intersection.
From the phase structure of the instance intersection, it is known that the signal is controlledThe traffic flow of the western straight-going vehicle and the western left-turning vehicle and the traffic flow of the southern straight-going vehicle and the southern left-turning vehicle can be finished at the same time. Therefore, the intersection has two phase partitions, and the corresponding two phase intervals are: the two traffic chains included in the phase zone 1 are L respectively 1 ＝{ws，el}、L 2 = { wl, es }, two traffic chains contained in phase zone 2 are L respectively 1 ＝{ns，sl}、L 2 ＝{nl，ss}。
And step four, generating a time interval division scheme of the phase interval according to the flow grade of each traffic flow in the phase interval.
And traversing all subintervals according to time sequence aiming at each phase interval, and judging whether the current subinterval needs to be switched into a new phase interval control interval or not by comparing the flow grade change condition of the traffic flow. The control period dividing scheme of each phase interval is relatively independent, and the dividing process is carried out in the phase interval.
Assuming that the current subperiod sequence number is i, i is more than or equal to 1 and less than or equal to 288; the control period sequence number is j, the subperiod set contained in the control period is S (j), and the initial value of the subperiod set is an empty set. The period division scheme procedure for generating the phase interval l is as follows:
first, the traffic class of the critical traffic chain for subinterval i is calculated.
The flow level of the traffic flow chain is the sum of the flow levels of all traffic flows in the traffic flow chain, and the flow levels of the two traffic flow chains in the phase interval 1 are respectively:
R L1 (i)＝R ws (i)+R el (i)
R L2 (i)＝R wl (i)+R es (i)
wherein R is Ll (i) L epsilon {1,2} is the first traffic chain in the phase section (L for short l ) Flow level at subinterval i; r is R f (i) F epsilon { ws, el, wl, es } is the flow level of the traffic flow f in the subinterval i.
Traffic class R of critical traffic chain K (i) The flow class maximum value of all traffic flow chains in the phase interval in the subperiod i is calculated as follows:
R K (i)＝max{R L1 (i)，R L2 (i)}
then, the maximum flow levels of all traffic chains in the current control period j are calculated.
Before calculating the flow level of the key traffic chain of the current control period j, the current control period j is updated firstly, namely, the subperiod i is integrated into the subperiod set S (j):
S(j)＝S(j)∪{i}
calculating the flow grade of each flow chain in the current control period j, taking the sum of the historical maximum flow grades of each flow in the flow chain in the current control period as the flow grade of the flow chain, wherein the calculation formula is as follows:
wherein R 'is' f (j) F epsilon { ws, el, wl, es } is the historical maximum flow level of the vehicle flow f in the control period j; r's' Ll (j) Traffic chain L with L epsilon {1,2} as control period j l Is a flow rate class of (c).
Thereby obtaining the maximum flow grade R 'of all the traffic flow chains in the current control period j' K (j) The method comprises the following steps:
R′ K (j)＝max{R′ L1 (j)，R′ L2 (j)}
finally, it is determined whether or not the switching to a new phase interval control period is required in the subinterval i.
There is no need to switch to a new phase interval control period in sub-period i when the following two conditions are satisfied at the same time: 1) The flow level of the key traffic chain of the current subinterval is equal to that of the key traffic chain of the previous subinterval; 2) Maximum flow level R 'for all traffic chains for current control period j' K (j) And the traffic class of the key traffic chain is not more than the subinterval i. Conversely, when at least one condition is not satisfied, a new phase interval control period needs to be switched to in the subperiod i, and S (j) and S (j+1) are updated:
S(j)＝S(j)-{i}
S(j+1)＝S(j+1)∪{i}
repeating the steps until all the sub-periods have the phase interval control period.
The control period division process of the phase zone 1 is as follows:
TABLE 2 control period partitioning procedure for phase section 1
The phase interval 1 is not repeated in the dividing process of the phase interval 2.
And fifthly, generating a time division scheme of the intersection according to the time division scheme of each phase interval of the intersection.
Combining the control time periods of each phase interval of the intersection in the same subinterval into a vector, and sequentially arranging according to the subinterval serial numbers:
V i ＝[a 1 (i)，a 2 (i)]，i＝1，2，...288
V i a time period vector of the intersection in the subperiod i; element a in a period vector p (i) P epsilon {1,2} is the control period to which the intersection p-th phase zone belongs in the subinterval i.
When the vectors of adjacent two periods are unequal, i.e. V i ≠V i-1 Indicating that at least one phase interval requires a switching control scheme; meanwhile, considering that the signal timing scheme of the intersection is not suitable for frequent switching, setting the duration of one control period of the intersection to be at least 3 and 5 minutes, namely, setting one control period of the intersection to comprise at least 3 subperiods. Thus, when V i ≠V i-1 Regenerating a control period empty set when the duration of the control period is more than 3 and 5 minutes, and incorporating the subperiod i therein;otherwise, sub-period i is incorporated into the current control period set.
And traversing all the subintervals in sequence, and repeating the steps until all the subintervals have the corresponding intersection control interval. The calculation process of this step is shown in the following table:
TABLE 3 control period division procedure for intersections
The time interval division scheme of the intersection and the single-lane average flow of each time interval can be obtained as shown in table 4:
TABLE 4 time period division scheme for intersection control and single lane average flow
Considering continuity of the intersection signal control scheme, the first control period "control period 1" and the last control period "control period 16" obtained by dividing may be combined into one period, which corresponds to a night low peak period.
Those skilled in the art will appreciate that all or part of the processes in the methods of the above embodiments may be implemented by a computer program for instructing relevant hardware, where the program may be stored in a non-volatile computer readable storage medium, and where the program, when executed, may include processes in the embodiments of the methods described above. Any reference to memory, storage, database, or other medium used in the various embodiments provided herein may include non-volatile and/or volatile memory. The nonvolatile memory can include Read Only Memory (ROM), programmable ROM (PROM), electrically Programmable ROM (EPROM), electrically Erasable Programmable ROM (EEPROM), or flash memory. Volatile memory can include Random Access Memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in a variety of forms such as Static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double Data Rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous Link DRAM (SLDRAM), memory bus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), among others.
The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above examples, and any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principle of the present invention should be made in the equivalent manner, and the embodiments are included in the protection scope of the present invention.
Claims (9)
1. The intersection time period dividing method based on the lane flow and the grade interval is characterized by comprising the following steps of:
s1, calculating the single-lane subinterval average flow of each traffic flow at an intersection;
s2, setting a flow grade interval, and generating a flow grade of the traffic flow according to the average flow of the traffic flow in a single lane subinterval;
s3, determining each phase interval of the intersection and a corresponding traffic flow chain according to the phase structure of the intersection;
s4, generating a time interval division scheme of the phase interval according to the flow grade of each traffic flow in the phase interval; the step S4 specifically comprises the following steps:
traversing all subintervals according to time sequence aiming at each phase interval, and judging whether the current subinterval needs to be switched into a new phase interval control interval or not by comparing the flow grade change condition of the traffic flow; each phase ofThe control time interval division scheme of the interval is relatively independent, and the division process is carried out in the phase interval; let the current subinterval sequence number be i,the sequence number of the control period is j, the subperiod set contained in the control period is S (j), and the initial value of the subperiod set is an empty set;
s401, calculating the flow grade of a key traffic chain in the subperiod i;
the flow grade of the traffic flow chain is the sum of the flow grades of all traffic flows in the traffic flow chain, and the calculation formula is as follows:
wherein R is Ll (i) For the first traffic chain L in the phase zone l Flow level at subinterval i; r is R f (i) The flow level of the traffic flow f in the subinterval i;
traffic class R of critical traffic chain K (i) The flow class maximum value of all traffic flow chains in the phase interval in the subperiod i is calculated as follows:
R K (i)＝max{R Ll (i)}
s402, calculating the maximum flow levels of all traffic flow chains in the current control period j;
calculating the flow grade of each flow chain in the current control period j, taking the sum of the historical maximum flow grades of each flow in the flow chain in the current control period as the flow grade of the flow chain, wherein the calculation formula is as follows:
wherein R is f ' j is the historical maximum flow level of the flow f over the control period j; r's' Ll (j) Traffic chain L for control period j l Is a flow rate class of (2);
further, the current control period is obtainedj maximum flow rating R 'for all traffic chains' K (j) The method comprises the following steps:
R′ K (j)＝max{R′ Ll (j)}
s403, judging whether the sub-period i needs to be switched to a new phase interval control period;
firstly, judging whether the demand of a key traffic chain on the passing time is obviously changed, namely comparing whether the flow levels of the key traffic chain in the current subperiod and the key traffic chain in the previous subperiod are equal;
if not, the traffic time requirement of the key traffic flow chain on the phase interval is obviously changed, and the key traffic flow chain needs to be switched into a new phase interval control period, and meanwhile, S (j) and S (j+1) are updated:
S(j)＝S(j)-{i}
S(j+1)＝S(j+1)∪{i}
if the traffic time requirements of the key traffic chain on the phase section are equal, namely the traffic time requirements of the key traffic chain on the phase section are kept unchanged, at the moment, whether the traffic time requirements of all traffic flows in the phase section in the control period S (j) can meet the requirements is judged, namely the maximum flow level R 'of all traffic flow chains in the current control period j is compared' K (j) Whether the flow level of the key traffic chain is larger than the subinterval i;
if the signal is larger than the threshold value, it indicates that when the same signal control scheme is executed in the sub-period i and other sub-periods in the control period j, the passing time requirement of at least one traffic flow in a certain sub-period is not satisfied, so that the control period needs to be switched to a new phase interval control period, and S (j) and S (j+1) are updated simultaneously:
S(j)＝S(j)-{i}
S(j+1)＝S(j+1)∪{i}
if not, the phase interval control period is not required to be switched into a new phase interval control period;
repeating the steps until all sub-periods have the phase interval control period;
s5, generating a time division scheme of the intersection according to the time division scheme of each phase interval of the intersection.
2. The intersection time period dividing method based on the lane flow and the level interval as claimed in claim 1, wherein the step S1 specifically comprises:
defining the traffic flow running on one lane group as one traffic flow, wherein the number of lane groups contained in one intersection is the number of traffic flows in the intersection; setting a subinterval as m minutes, wherein the value of m is considered to avoid the instant influence of an upstream intersection signal timing scheme and reflect the continuous change rule of the arrival flow in time; and converting the subinterval flow of each lane group of the intersection into the single-lane subinterval average flow of the lane group to obtain the single-lane subinterval average flow of each traffic flow of the intersection.
3. The intersection time period dividing method based on the traffic lane flow and the class section according to claim 2, further comprising the steps of:
the resulting single lane subinterval average flow of each stream is smoothed, including but not limited to a sliding average method and an exponential sliding average method.
4. The intersection time period dividing method based on the lane flow and the level interval as claimed in claim 1, wherein the step S2 specifically comprises:
s201, setting a flow grade interval;
the flow class section consists of a group of continuous sections capable of covering the intersection flow change section, such as [0, q ] 1 ),[q 1 ,q 2 ),[q 2 ,q 3 ) The length of each section is determined by setting a threshold for changing the green-to-signal ratio of each traffic stream, and the flow rate class section Δq with equal section length is calculated as follows:
wherein q n The upper limit of the nth flow level interval and the lower limit of the (n+1) th flow level interval are given in units of vehicles/hour; q n-1 For the n-1 th flowThe upper limit of the level interval and the lower limit of the nth flow level interval are given in units of vehicles/hour; q 0 =0; delta n is a change threshold value of the number of vehicles arriving in a single lane in one period; c is the period duration of the intersection signal, and the unit is seconds; q S The unit is vehicle/hour, which is the saturation flow of a single lane; Δt is the change threshold of green time of one period, and the unit is seconds; Δλ is the threshold of change in traffic flow green to signal ratio;is an upward rounding operation;
s202, generating a traffic flow grade of a traffic flow;
determining the flow grade of the average flow of each traffic flow in a single-lane subinterval according to the flow grade interval; in order to avoid the adverse effect of instantaneous fluctuation of the flow on the time division, the duration of the flow class of the vehicle flow is set to at least n P For m minutes, so that there is at least n P The successive subintervals correspond to the same traffic class; dividing the average flow of the single-lane subinterval of the traffic flow calculated in the step S1 into different flow grades, wherein the number of continuous subintervals is smaller than n P Is modified to ensure that all levels last at least n continuously P Sub-periods.
5. The intersection time period division method based on the lane flow and the class section according to claim 4, wherein in step S201:
setting the same green signal ratio change threshold value for each interval, thereby obtaining a group of flow grade intervals with equal interval length; or different green-to-signal ratio change thresholds are taken for each section to adapt to actual traffic demands, so that flow grade sections with different section lengths are obtained.
6. The intersection time period dividing method based on the lane flow and the level interval as claimed in claim 1, wherein the step S3 specifically comprises:
defining the time when all traffic flows which are controlled by signals and have right of passage finish passing simultaneously as phase partitions, wherein two adjacent phase partitions form a phase interval, and the number of the phase intervals of the intersection is equal to the number of the phase partitions because the traffic right conversion of the intersection has periodicity; the traffic flows which successively acquire the right of passage in one phase interval form a traffic flow chain, and the same phase interval possibly comprises a plurality of traffic flow chains which share the same passage time.
7. The intersection time period division method based on the lane traffic and the level interval according to claim 1, wherein in step S402, before calculating the traffic level of the key traffic chain of the current control time period j, the current control time period j is first updated, that is, the sub-time period i is incorporated into the sub-time period set S (j):
S(j)＝S(j)∪{i}。
8. the intersection time period dividing method based on the lane flow and the level interval as claimed in claim 1, wherein the step S5 specifically comprises:
combining the control time periods of each phase interval of the intersection in the same subinterval into a vector, and sequentially arranging according to the subinterval serial numbers:
V i a time period vector of the intersection in the subperiod i; element a in a period vector p (i) The control period of the p-th phase interval of the intersection in the subperiod i is adopted; p is p * The phase interval number of the intersection;
when the vectors of adjacent two periods are unequal, i.e. V i ≠V i-1 Indicating that at least one phase interval requires a switching control scheme; meanwhile, considering that the signal timing scheme of the intersection is not suitable for frequent switching, setting the duration of one control period of the intersection to be at least n Q M minutes, i.e. one control period of the intersection contains at least n Q Sub-periods; thus, when V i ≠V i-1 And the duration of the control period is greater than n Q Regenerating a control period empty set at m minutes, and incorporating a sub-period i therein; otherwise, sub-period i is incorporated into the current control period set.
9. The intersection time period division method based on the lane flow and the class section according to claim 8, wherein the step S5 further comprises the steps of:
and traversing all the subintervals in sequence, and repeating the step S5 until all the subintervals have the corresponding intersection control intervals.
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