CN104484514B - A Design Method for Elastic Bus Routes Avoiding Congested Sections - Google Patents

Abstract

The invention discloses a kind of elastic public bus network method for designing for evading congested link, road network topology is considered in the method for designing, traffic control, road traffic flow, routing behavior etc. concerns road traffic system component (road, car, people) mass action, for identical numbering public bus network, on the premise of origin and destination and most of driving path are not changed, vehicle transition website on the way is set up with regard to some congested links, obtain effectively substituting public bus network network, and the optimal effective replacement public transport line of selection one replaces original public bus network as elastic public bus network in effectively public bus network network is substituted, make what public transit vehicle can be autonomous during operation to avoid congested link, reduce trip duration of the passenger in bus and ensure the minimum ground traveling value added of passenger；Advantage is the operational efficiency and service level that improve bus operation system.

Description

A Design Method for Elastic Bus Routes Avoiding Congested Sections

technical field

The invention relates to a bus line design method, in particular to a flexible bus line design method for avoiding congested road sections.

Background technique

The bus operation system is an indispensable and important transportation system in urban life at present. Each bus vehicle in the bus operation system transports passengers through each station according to the established bus route. Due to the rapid pace of urbanization in our country, the population density, traffic flow and passenger flow are relatively large. In the actual bus operation process, many bus lines often have road congestion. Bus vehicles cannot flexibly change their driving routes according to road traffic conditions. This increases the transportation time of public transport vehicles and the travel time of passengers, and the operating efficiency of the public transport operation system drops sharply.

According to the public transport willingness survey, 47.6% of private car owners are willing to take public transport during off-peak hours, and 12% of private car owners are willing to take public transport during peak hours. Explanation: During peak hours, some bus stops in the central city are very congested, causing a waste of time. Therefore, it is more willing to choose private cars to bypass congested roads to reduce travel time.

In view of this, it is important to design a flexible bus route design method to avoid congested roads, so that buses can avoid congested roads autonomously during operation, which is of great importance for improving the operation efficiency and service level of the bus operation system and advocating green and environmentally friendly public transportation. significance.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for designing elastic bus routes to avoid congested road sections. The method uses elastic bus routes to replace the established original bus routes, so that buses can autonomously avoid congested road sections during operation and improve Improve the operating efficiency and service level of the bus operation system.

The technical solution adopted by the present invention to solve the above-mentioned technical problems is: a method for designing elastic bus lines to avoid congested road sections, comprising the following steps:

Step 1: Download the Shapefile vector file of the urban topological road network through the OpenStreetMap open source website; obtain the current traffic flow of each road section in the city through the video detector, and the current traffic flow of the road section refers to the traffic flow of the road section in the past 15 minutes from the current time; Obtain the city's dynamic traffic demand from the Urban Planning Bureau; input the Shapefile vector file, the current traffic flow and dynamic traffic demand of each road section into the VISTA software, and run the VISTA software to obtain the future dynamic traffic distribution flow of each road section, as shown in formula (1). Show:

In the formula (1), every 15 minutes starting from the current time is regarded as a time period, y _a,t is the dynamic traffic allocation flow of road section a from the current time to the t time period in the future, and x _a is the road section The current traffic flow of a, q _{ω, τ} represents the dynamic traffic demand for ω generated from the start and end points in the τth time period in the future; is the element of the traffic distribution matrix, which represents the number of the demand for ω from the starting point to ω in the τth time period in the future. The corresponding matrix of traffic flow is obtained by running the VISTA software; W represents the set of origin-destination pairs, and W is obtained from the dynamic traffic demand of the city;

Step 2: Obtain the free flow travel time, theoretical traffic capacity and green signal ratio of intersection signal lights from the Urban Transportation Commission, and calculate the travel time per unit length of vehicles running on each road segment at each time period in the future. The calculation formula is as in formula (2) Shown:

In the formula (2), T _a,t is the travel time per unit length of the vehicle on the road section a in the future t-th time period, the unit is second/km; u _a is the free flow travel time on the road section a, the unit is second/km ; j is the delay parameter, j=p×k, p is the density of delay-causing elements, p is obtained from the Shapefile vector file, k represents the randomness level of vehicle arrival and service process, and the value of k is taken at non-signalized intersections is 1, and the value of k at signalized intersections is 0.5; δ is the flow analysis time length, which is 1 hour; is the traffic service level of road segment a in the tth time period, Q _a is the theoretical traffic capacity of road section a, in car/hour; λ _a is the green signal ratio of road section a; the unit of y _a,t is car/hour;

Step 3: Loop all original bus start-destination pairs, and construct alternative bus lines for all original bus lines according to the travel time per unit length of vehicles running on each road segment in each time period in the future obtained in step 2. The specific process is as follows:

Step 3.1: Take the original bus line as the baseline, select the road network included in the area with a vertical distance of v meters on both sides of the original bus line as the basic network of the alternative bus line, and call the basic network of the alternative bus line the backup Route selection network, 500≤v≤1000;

Step 3.2: Correct the travel time per unit length of all congested road sections contained in each alternative bus route in the alternative road network according to the principle of penalty for congested road sections. The specific process is as follows:

Step 3.2.1: Record the congestion coefficient as ρ, ρ is a constant and 100 seconds/km ≤ ρ ≤ 200 seconds/km, if the travel time of a certain road section is greater than ρ, it is judged that the road section is a congested road section, otherwise it is not Congested road section;

Step 3.2.2: Set the travel time per unit length of all non-congested sections contained in the original bus line to 0;

Step 3.2.3: Correct the travel time per unit length of all congested road sections contained in the alternative bus lines in the alternative road network: add the calculated value of the travel time per unit length of the corresponding congested road section calculated in step 2 to M As the travel time per unit length after correction of the congested section, M=1000;

Step 3.3: For the starting and ending points of the original bus line, select all the alternative bus lines on the alternative road network, calculate the travel time of the original bus line and each alternative bus line, the travel time of the original bus line is equal to the original bus line The sum of the travel time of all road segments included in the line, the travel time of each alternative bus line is equal to the sum of the travel time of all road segments contained in each alternative bus line, and the travel time of each road segment is equal to the unit length of the road segment Multiply the travel time by the length of the road section; sort all the alternative bus lines in the alternative road network according to the travel time from small to large, and record them as the first alternative bus line, the second alternative bus line, and the second alternative bus line. 3 alternative bus lines, ..., the Gth alternative bus line, where G is the total number of alternative bus lines;

Step 3.4: Compare the alternative bus lines in the sorted alternative road network with the original bus lines in turn to determine effective alternative bus lines. The specific process is as follows:

Step 3.4.1: For each origin-destination point pair, starting from the first alternative bus line, compare the travel time of the alternative bus line with the travel time of the original bus line in turn, if the travel time of the alternative bus line Time is less than the travel time of the original bus line and the current number of candidate bus lines is less than J, then compare the travel time of the latter alternative bus line with the travel time of the original bus line, and so on; When the travel time of the selected bus line is greater than the travel time of the original bus line or the sorting number of the Kth alternative bus line is equal to J, then stop the comparison, and the K-1 alternative bus lines before the Kth alternative bus line As an effective alternative bus line network; where 1≤K≤J, J is a constant greater than or equal to 3 and less than or equal to 7;

Step 3.5: Perform correlation analysis on each effective alternative bus line in the effective alternative bus line network and the original bus line, and select the effective alternative bus line with the optimal correlation degree as the elastic bus line. The specific steps are as follows;

Step 3.5.1: For the original site s of the original bus line, s=1,2,3,...,n, where n is the total number of sites on the original bus line, and the original site s of the original bus line is in the effective alternative bus line All have corresponding transition stations. By comparing the additional travel time of passengers generated by the following three transition schemes, the station corresponding to the minimum additional passenger travel time is taken as the optimal transition station:

(1) Effectively replace the bus stop on the bus line with the least walking time from the corresponding stop on the original bus line; (2) Effectively replace the intersection on the bus line with the least walking time from the corresponding stop on the original bus line; (3) belongs to the original bus line It also belongs to the bus stop with the least travel time of the detour route;

Step 3.5.2: From the Shapefile vector file, output the shortest travel time from the original station s of the original bus line to the change station of the ith effective alternative bus line, where i=1,2,...,K-1, and The average number of passengers getting on and off at this station is multiplied to obtain a comparison series D _i,s , D _i,s = {D _1,s ,D _2,s ,…,D _K,s }, the average number of passengers getting on and off at this station is obtained from the bus Obtained from the database of the operating company, the D _i, s corresponding to the original station s of the original bus line is normalized by the following formula:

Among them, Δ is the minimum value in the comparison series of all effective alternative bus lines, is the maximum value in the comparison series of all effective alternative bus lines, and the correlation coefficient ξi _,s corresponding to the s-th station of the i-th effective alternative bus line is obtained as follows:

Among them, m is the resolution coefficient, which is a constant between 0 and 1;

Step 3.5.3: Record the correlation degree of the i-th effective alternative bus line as r _i , i=1,2,...,K-1, and the solution formula for r _i is as follows:

Step 3.5.4: Select the effective alternative bus line with the largest r _i in the effective alternative bus line network as the elastic bus line to be adopted.

After the elastic bus line is determined, the bus driver will operate according to the elastic bus line through the intelligent bus system, and at the original bus line site where the elastic bus line no longer passes, the bus line site will be announced by the electronic display sign one departure interval in advance Change notification; thus, passengers who take the corresponding line can go to another station to take a bus, reducing the inconvenience caused to passengers.

Compared with the prior art, the present invention has the advantage of comprehensively considering the overall effect of road network topology, traffic control, road traffic flow, road selection behavior and other elements (roads, vehicles, and people) related to the road traffic system. For bus lines, under the premise of not changing the origin and destination points and most of the driving routes, vehicle change stations are added on some congested road sections on the way to obtain an effective alternative bus line network, and an optimal and effective alternative bus line network is selected in the effective alternative bus line network. The bus line is used as a flexible bus line to replace the original bus line, so that the bus vehicles can autonomously avoid congested roads during operation, reduce the travel time of passengers in the bus and ensure that passengers walk on the ground at least, which improves the bus operation. System operational efficiency and service levels.

Description of drawings

Fig. 1 is a kind of flow chart of the elastic public transport route design method of avoiding congested section of the present invention;

Fig. 2 obtains the internal flowchart of dynamic traffic distribution flow for VISTA software;

Fig. 3 is the coil and video detection map of current traffic flow collection;

Figure 4 is a route diagram of Ningbo Bus No. 367 in the case;

Figure 5 shows the alternative road network within 800 meters around the original bus line (including road section number and bus stop name);

Figure 6 is a schematic diagram of three forms of bus station relocation;

Figure 7 is the optimal alternative bus route and station layout diagram;

Figure 8 is a release map of the station relocation information on the electronic information board of the Jingjia Road bus station in the case.

detailed description

The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

Embodiment: as shown in Figure 1, a kind of elastic public transport line design method of avoiding congested section, comprises the steps:

Step 1: Download the Shapefile vector file of the urban topological road network through the OpenStreetMap open source website; obtain the current traffic flow of each road section in the city through the video detector, and the current traffic flow of the road section refers to the traffic flow of the road section in the past 15 minutes from the current time; Obtain the city's dynamic traffic demand from the Urban Planning Bureau; input the Shapefile vector file, the current traffic flow and dynamic traffic demand of each road section into the VISTA software, and run the VISTA software to obtain the future dynamic traffic distribution flow of each road section, as shown in formula (1). Show:

In the formula (1), every 15 minutes starting from the current time is regarded as a time period, y _a,t is the dynamic traffic allocation flow of road section a from the current time to the t time period in the future, and x _a is the road section The current traffic flow of a, q _{ω, τ} represents the dynamic traffic demand for ω generated from the start and end points in the τth time period in the future; is the element of the traffic distribution matrix, which represents the number of the demand for ω from the starting point to ω in the τth time period in the future. For the corresponding matrix of traffic flow, the traffic allocation matrix is derived in the VISTA software based on the optimization of the route diversion ratio based on the stepwise iterative averaging method (MSA) and the mutual iterative principle of the traffic flow simulation based on the link cell transfer model (LTM); W means A set of origin-destination pairs, W is obtained from the dynamic traffic demand of the city;

Step 2: Obtain the free flow travel time, theoretical traffic capacity and green signal ratio of intersection signal lights from the Urban Transportation Commission, and calculate the travel time per unit length of vehicles running on each road segment in each time period in the future. The calculation formula uses the Akcelik road resistance function (The advantage of this road resistance function is that it can cope with various saturation situations at intersections), as shown in formula (2):

In the formula (2), T _a,t is the travel time per unit length of the vehicle on the road section a in the future t-th time period, the unit is second/km; u _a is the free flow travel time on the road section a, the unit is second/km ; j is the delay parameter, j=p×k, p is the density of delay-causing elements, p is obtained from the Shapefile vector file, k represents the randomness level of vehicle arrival and service process, and the value of k is taken at non-signalized intersections is 1, and the value of k at signalized intersections is 0.5; δ is the flow analysis time length, which is 1 hour; is the traffic service level of road segment a in the tth time period, Q _a is the theoretical traffic capacity of road section a, in car/hour; λ _a is the green signal ratio of road section a; the unit of y _a,t is car/hour;

Step 3: Loop all original bus start-destination pairs, and construct alternative bus lines for all original bus lines according to the travel time per unit length of vehicles running on each road segment in each time period in the future obtained in step 2. The specific process is as follows:

Step 3.1: Take the original bus line as the baseline, select the road network included in the area with a vertical distance of v meters on both sides of the original bus line as the basic network of the alternative bus line, and call the basic network of the alternative bus line the backup Road selection network, v is subject to the constraints of the acceptable travel distance of passengers and the actual density of the road network, 500≤v≤1000;

Step 3.2: In order to make the alternative bus line meet the dual goals of passing through the non-congested road section of the original bus line and avoiding the congested road section, according to the penalty principle of the congested road section, correct Travel time per unit length, the specific process is:

Step 3.2.1: Record the congestion coefficient as ρ, ρ is a constant and 100 seconds/km ≤ ρ ≤ 200 seconds/km, if the travel time of a certain road section is greater than ρ, it is judged that the road section is a congested road section, otherwise it is not Congested road section;

Step 3.2.2: Set the travel time per unit length of all non-congested sections contained in the original bus line to 0;

Step 3.2.3: Correct the travel time per unit length of all congested road sections contained in the alternative bus lines in the alternative road network: add the calculated value of the travel time per unit length of the corresponding congested road section calculated in step 2 to M As the corrected travel time per unit length of the congested road section, M=1000, thereby reducing the probability that the congested road section is selected to enter an alternative bus route;

Step 3.3: For the starting and ending points of the original bus line, select all the alternative bus lines on the alternative road network, calculate the travel time of the original bus line and each alternative bus line, the travel time of the original bus line is equal to the original bus line The sum of the travel time of all road segments included in the line, the travel time of each alternative bus line is equal to the sum of the travel time of all road segments contained in each alternative bus line, and the travel time of each road segment is equal to the unit length of the road segment Multiply the travel time by the length of the road section; sort all the alternative bus lines in the alternative road network according to the travel time from small to large, and record them as the first alternative bus line, the second alternative bus line, and the second alternative bus line. 3 alternative bus lines, ..., the Gth alternative bus line, where G is the total number of alternative bus lines;

Step 3.4: Compare the alternative bus lines in the sorted alternative road network with the original bus lines in turn to determine effective alternative bus lines. The specific process is as follows:

Step 3.4.1: For each origin-destination point pair, starting from the first alternative bus line, compare the travel time of the alternative bus line with the travel time of the original bus line in turn, if the travel time of the alternative bus line Time is less than the travel time of the original bus line and the current number of candidate bus lines is less than J, then compare the travel time of the latter alternative bus line with the travel time of the original bus line, and so on; Stop when the travel time of the selected bus line is greater than the travel time of the original bus line or the sorting number of the K-th alternative bus line is equal to J, then stop the comparison, and compare the K-1 alternative bus lines before the K-th alternative bus line The line serves as an effective alternative bus line network; where 1≤K≤G, J is a constant greater than or equal to 3 and less than or equal to 7;

Step 3.5: Since the optimization goal of bus lines is not to find the shortest route, but to take into account the convenience of the majority of passengers, the original bus line is often not the shortest route between the origin and destination, but comprehensively considers the station service coverage and line service quality In order to maintain the same direction as the original bus line, by using the gray correlation analysis method, each effective alternative bus line in the effective alternative bus line network is associated with the original bus line, and the optimal correlation is selected. To effectively replace the bus line as a flexible bus line, the specific steps are as follows;

Step 3.5.1: For the original site s of the original bus line, s=1,2,3,...,n, where n is the total number of sites on the original bus line, and the original site s of the original bus line is in the effective alternative bus line All have corresponding transition stations. By comparing the additional travel time of passengers generated by the following three transition schemes, the station corresponding to the minimum additional passenger travel time is taken as the optimal transition station:

(1) Effectively replace the bus stop on the bus line with the least walking time from the corresponding stop on the original bus line; (2) Effectively replace the intersection on the bus line with the least walking time from the corresponding stop on the original bus line; (3) belongs to the original bus line It also belongs to the bus stop with the least travel time of the detour route;

Step 3.5.2: From the Shapefile vector file, output the shortest travel time from the original station s of the original bus line to the change station of the ith effective alternative bus line, where i=1,2,...,K-1, and The average number of passengers getting on and off at this station is multiplied to obtain a comparison series D _i,s , D _i,s = {D _1,s ,D _2,s ,…,D _K,s }, the average number of passengers getting on and off at this station is obtained from the bus Obtained from the database of the operating company, the D _i, s corresponding to the original station s of the original bus line is normalized by the following formula:

Among them, Δ is the minimum value in the comparison series of all effective alternative bus lines, is the maximum value in the comparison series of all effective alternative bus lines, and the correlation coefficient ξi _,s corresponding to the s-th station of the i-th effective alternative bus line is obtained as follows:

Among them, m is the resolution coefficient, which is a constant between 0 and 1;

Step 3.5.3: Record the correlation degree of the i-th effective alternative bus line as r _i , i=1,2,...,K-1, and the solution formula for r _i is as follows:

Step 3.5.4: Select the effective alternative bus line with the largest r _i in the effective alternative bus line network as the elastic bus line to be adopted;

Step 4: After the flexible bus route is determined, the bus driver will run according to the flexible bus route through the intelligent bus system, and at the position of the original bus route stop where the flexible bus route no longer passes, the departure interval will be released by the electronic display sign in advance Notification of bus line stop change.

In the present invention, the dynamic traffic allocation can fit the real-time fluctuation law of the road network traffic flow, and can guide the daily real-time traffic management including the congestion control based on the intelligent traffic guidance system. The focus of dynamic traffic allocation is on the authenticity of results and solution efficiency, because it is directly used to guide real-time traffic management, and there is no application market for wrong information and overtime calculations. From the perspective of the core link of traffic flow loading, there are two main branches—continuous and discrete dynamic traffic allocation. Most of the former set up variational inequalities or fixed-point equations based on cybernetics ideas, and discretization time is still needed to obtain state variables when solving, but the problem of determining the control parameters is still unsolved, and the convergence of the solution cannot always be guaranteed. Therefore, Even in the combined road network of several road sections, there are few applications. The latter can be said to be a quasi-dynamic allocation, but it is not a simple superposition of static traffic allocation flow in the time dimension. It actually also considers the interaction of time and space flow, and only increases the discrete division of time units to facilitate variables. The expression of the actual relationship between them can present the first-come-first-out rules, capacity constraints, overflow and other problems encountered in traffic loading more clearly, and can be solved more targetedly. Therefore, many dynamic traffic allocation software are based on discrete branches. And the development generally rises in universities and research institutes, and VISTA is one of them. The essence of the solution process of the software is the stepwise average iterative (MSA) method to search for the shortest travel path and the link cell transfer model (LTM) simulator to simulate the actual road flow operation status of the continuous iterative process. The process is shown in Figure 2, that is, for MSA The diversion ratio of each path obtained by the method is used to simulate the actual road flow operating state with the LTM simulator, and then the MSA method is used to optimize the diversion ratio of the path according to the current simulated road flow, and so on until the final dynamic traffic flow changes meet the requirements (the flow difference is less than ε given by the decision maker, output the dynamic traffic flow required by the above formula.

The road traffic flow of the candidate road network in this embodiment comes from the current situation survey, so the time-varying traffic occupancy on the candidate road network is the same at each time period. The road coil detector shown in Figure 3 is used to measure the traffic flow of each road segment in the past 15 minutes from the current time: for any road segment a on the alternative road network, its upstream detection coil or video detector detects the passing vehicles Detect and count to obtain the number of vehicles that have entered the road section a in the past 15 minutes since the current time, and the final traffic flow is transformed into x _a after unit time; assuming that the final dynamic traffic flow value of any time period in the future is as shown in the following table, where , the column is the road section number, from Figure 5; in order to be used in the Akcelik road resistance function in the subsequent formula (2), the unit of traffic flow has been converted to vehicle/hour.

road section 1 2 3 4 5 6 7 8 traffic flow 532 463 478 696 1582 657 544 735 road section 9 10 11 12 13 14 15 16 traffic flow 668 306 387 1434 564 679 688 644 road section 17 18 19 20 twenty one twenty two twenty three twenty four traffic flow 337 750 794 651 1402 583 429 441 road section 25 26 27 28 29 30 31 32 traffic flow 675 532 435 431 664 739 323 399

According to the obtained green signal ratio and traffic capacity of each road section, combined with the traffic flow of the above road section, the Akcelik road resistance function formula is used to obtain the unit mileage travel time of each road section in each time period, and after multiplying by the actual road section length, the travel time result ( The unit is seconds) as shown in the table below.

road section 1 2 3 4 5 6 7 8 travel time 118 113 151 154 453 93 123 119 road section 9 10 11 12 13 14 15 16 travel time 470 139 145 371 150 102 142 273 road section 17 18 19 20 twenty one twenty two twenty three twenty four travel time 140 275 91 301 441 86 124 170 road section 25 26 27 28 29 30 31 32 travel time 109 133 97 150 100 301 125 144

In this embodiment, a certain bus line 367 in Ningbo City shown in FIG. 4 is used as an example. Some lines close to the starting position and the end position are not optimized for line changes. There are three reasons: (1) There is less congestion in these road sections during peak hours, and the corresponding buses arrive early or late at the station. Bus punctuality rate and customer service level; (2) It is difficult to find alternative routes in the short distance around. Here, only some lines that pass through the core of Jiangdong District are detoured during peak hours, and some bus lines to be adjusted are marked with thick lines, as shown in Figure 5. The road network without coloring in Figure 5 can be used as an alternative road network. It is within 800 meters (v=800 meters) around the bus line. The number of the road section is marked with numbers beside the road section. The bus stop and its name are also on the original line Labels are given. Taking ρ as 100 seconds/km, it is calculated by the unit mileage travel time of each alternative bus line. The numbers of the congested road sections are: 5, 9, 12, 16, 18, 20, 21, 30.

In step 3.4, K here is taken as 4, and the three shortest paths finally generated are shown in the following table; since the travel time of each time period is equal, there is no time-period representation.

bus routes section number Travel time (seconds) 1 1,2,6,13,17,14,11,15,22,27,28,29,31,32 485 2 1,2,3,7,11,15,22,27,28,29,31,32 519 3 1,2,6,10,11,15,22,27,28,29,31,32 526

In this embodiment, the migration effects of bus stops corresponding to several types of original bus lines are shown in Figure 6. The first sub-graph corresponds to the nearest intersection as the type of temporary bus stop, and the second sub-graph corresponds to bus stops on other lines As the type of temporary bus stops, the third sub-graph corresponds to the type of adjacent bus stops on the original bus line as temporary bus stops. Taking the resolution coefficient m=0.5, the correlation coefficients of the stations on each alternative bus line are shown in the table below.

Affected site East China Sea Garden Jinyuan District Jinyuan East Lane Jinyuan West Lane startled road Yonggang New Village line 1 0.59 1 1 1 0.69 0.61 line 2 0.33 0.37 0.33 0.45 0.38 0.61 line 3 0.59 0.71 0.45 0.45 0.38 0.61

The average correlation coefficient of each alternative alternative bus line is shown in the table below:

line 1 2 3 average correlation coefficient 0.82 0.41 0.53

Select the most relevant route 1 from the above correlation degrees as the departure route at that time, and the travel route and station layout are shown in Figure 7. Taking the original bus stop on Jingjia Road as an example, the published content when the route is changed is shown in Figure 8. The information generally consists of three sentences, respectively expressing the travel situation of the broadcast line, the station migration situation, and the arrival time prediction; among them, according to whether the bus system has intelligent prediction technology, choose whether to display the content of the third sentence.

Claims (2)

1. A method for designing flexible public transport routes for avoiding congested road sections, is characterized in that comprising the steps: Step 1: Download the Shapefile vector file of the urban topological road network through the OpenStreetMap open source website; obtain the current traffic flow of each road section in the city through the video detector, and the current traffic flow of the road section refers to the traffic flow of the road section in the past 15 minutes from the current time; Obtain the city's dynamic traffic demand from the Urban Planning Bureau; input the Shapefile vector file, the current traffic flow and dynamic traffic demand of each road section into the VISTA software, and run the VISTA software to obtain the future dynamic traffic distribution flow of each road section, as shown in formula (1). Show: In the formula (1), every 15 minutes starting from the current time is regarded as a time period, y _a,t is the dynamic traffic allocation flow of road section a from the current time to the t time period in the future, and x _a is the road section The current traffic flow of a, q _{ω, τ} represents the dynamic traffic demand for ω generated from the start and end points in the τth time period in the future; is the element of the traffic distribution matrix, which represents the number of the demand for ω from the starting point to ω in the τth time period in the future. The corresponding matrix of traffic flow is obtained by running the VISTA software; W represents the set of origin-destination pairs, and W is obtained from the dynamic traffic demand of the city; Step 2: Obtain the free flow travel time, theoretical traffic capacity and green signal ratio of intersection signal lights from the Urban Transportation Commission, and calculate the travel time per unit length of vehicles running on each road segment at each time period in the future. The calculation formula is as in formula (2) Shown: In the formula (2), T _a,t is the travel time per unit length of the vehicle on the road section a in the future t-th time period, the unit is second/km; u _a is the free flow travel time on the road section a, the unit is second/km ; j is the delay parameter, j=p×k, p is the density of delay-causing elements, p is obtained from the Shapefile vector file, k represents the randomness level of vehicle arrival and service process, and the value of k is taken at non-signalized intersections is 1, and the value of k at signalized intersections is 0.5; δ is the flow analysis time length, which is 1 hour; is the traffic service level of road segment a in the tth time period, Q _a is the theoretical traffic capacity of road section a, in car/hour; λ _a is the green signal ratio of road section a; the unit of y _a,t is car/hour; Step 3: Loop all original bus start-destination pairs, and construct alternative bus lines for all original bus lines according to the travel time per unit length of vehicles running on each road segment in each time period in the future obtained in step 2. The specific process is as follows: Step 3.1: Take the original bus line as the baseline, select the road network included in the area with a vertical distance of v meters on both sides of the original bus line as the basic network of the alternative bus line, and call the basic network of the alternative bus line the backup Route selection network, 500≤v≤1000; Step 3.2: Correct the travel time per unit length of all congested road sections contained in each alternative bus route in the alternative road network according to the principle of penalty for congested road sections. The specific process is as follows: Step 3.2.1: Record the congestion coefficient as ρ, ρ is a constant and 100 seconds/km ≤ ρ ≤ 200 seconds/km, if the travel time of a certain road section is greater than ρ, it is judged that the road section is a congested road section, otherwise it is not Congested road section; Step 3.2.2: Set the travel time per unit length of all non-congested sections contained in the original bus line to 0; Step 3.2.3: Correct the travel time per unit length of all congested road sections contained in the alternative bus lines in the alternative road network: add the calculated value of the travel time per unit length of the corresponding congested road section calculated in step 2 to M As the travel time per unit length after correction of the congested section, M=1000; Step 3.3: For the starting and ending points of the original bus line, select all the alternative bus lines on the alternative road network, calculate the travel time of the original bus line and each alternative bus line, the travel time of the original bus line is equal to the original bus line The sum of the travel time of all road segments included in the line, the travel time of each alternative bus line is equal to the sum of the travel time of all road segments contained in each alternative bus line, and the travel time of each road segment is equal to the unit length of the road segment Multiply the travel time by the length of the road section; sort all the alternative bus lines in the alternative road network according to the travel time from small to large, and record them as the first alternative bus line, the second alternative bus line, and the second alternative bus line. 3 alternative bus lines, ..., the Gth alternative bus line, where G is the total number of alternative bus lines; Step 3.4: Compare the alternative bus lines in the sorted alternative road network with the original bus lines in turn to determine effective alternative bus lines. The specific process is as follows: Step 3.4.1: For each origin-destination point pair, starting from the first alternative bus line, compare the travel time of the alternative bus line with the travel time of the original bus line in turn, if the travel time of the alternative bus line Time is less than the travel time of the original bus line and the current number of candidate bus lines is less than J, then compare the travel time of the latter alternative bus line with the travel time of the original bus line, and so on; Stop when the travel time of the selected bus line is greater than the travel time of the original bus line or the sorting number of the K-th alternative bus line is equal to J, then stop the comparison, and compare the K-1 alternative bus lines before the K-th alternative bus line The line serves as an effective alternative bus line network; where 1≤K≤G, J is a constant greater than or equal to 3 and less than or equal to 7; Step 3.5: Perform correlation analysis on each effective alternative bus line in the effective alternative bus line network and the original bus line, and select the effective alternative bus line with the optimal correlation degree as the elastic bus line. The specific steps are as follows; Step 3.5.1: For the original site s of the original bus line, s=1,2,3,...,n, where n is the total number of sites on the original bus line, and the original site s of the original bus line is in the effective alternative bus line All have corresponding transition stations. By comparing the additional travel time of passengers generated by the following three transition schemes, the station corresponding to the minimum additional passenger travel time is taken as the optimal transition station: (1) effectively replace the bus stop on the bus line with the least walking time from the corresponding stop on the original bus line, (2) effectively replace the intersection on the bus line with the least walking time from the corresponding stop on the original bus line, (3) belong to the original bus line It also belongs to the bus stop with the least travel time of the detour route; Step 3.5.2: From the Shapefile vector file, output the shortest travel time from the original station s of the original bus line to the change station of the ith effective alternative bus line, where i=1,2,...,K-1, and The average number of passengers getting on and off at this station is multiplied to obtain a comparison series D _i,s , D _i,s = {D _1,s ,D _2,s ,…,D _K,s }, the average number of passengers getting on and off at this station is obtained from the bus Obtained from the database of the operating company, the D _i, s corresponding to the original station s of the original bus line is normalized by the following formula: Among them, Δ is the minimum value in the comparison series of all effective alternative bus lines, is the maximum value in the comparison series of all effective alternative bus lines, and the correlation coefficient ξi _,s corresponding to the s-th station of the i-th effective alternative bus line is obtained as follows: Among them, m is the resolution coefficient, which is a constant between 0 and 1; Step 3.5.3: Record the correlation degree of the i-th effective alternative bus line as r _i , i=1,2,...,K-1, and the solution formula for r _i is as follows: Step 3.5.4: Select the effective alternative bus line with the largest r _i in the effective alternative bus line network as the elastic bus line to be adopted. 2. a kind of flexible bus line design method for avoiding congested sections according to claim 1 is characterized in that after the elastic bus line is determined, the bus driver operates according to the elastic bus line by the intelligent public transport system, and the flexible bus line For the location of the original bus line stop where the line no longer passes, the change notice of the bus line stop will be issued by the electronic display sign one time in advance of the departure interval.