A method for evaluating a highway interchange spacing arrangement scheme

Abstract

The application belongs to the technical field of traffic planning of expressway network, and discloses an evaluation method of an expressway intercommunication overpass interval setting scheme, which is used to select the best setting scheme of the expressway intercommunication overpass interval. First, based on the operation characteristics of the expressway, an evaluation index system composed of traffic efficiency, traffic risk, accessibility and construction cost is constructed. Then, combined with the VISSIM simulation model, the entropy weight method and the TOPSIS comprehensive evaluation method, the evaluation method of the expressway intercommunication overpass interval setting scheme based on the aforementioned evaluation index system is constructed. The evaluation method designed by the application can provide support for the relevant departments to set the expressway intercommunication overpass interval for strengthening the connection of the highway traffic network of the urban agglomeration under the background of the continuous expansion of the urbanization scale.

Description

Technical Field

[0001] The present invention relates to the technical field of traffic planning of expressway networks, and in particular to an evaluation method for setting schemes of interchange spacing of expressways. Background Art

[0002] Expressways are transportation corridors connecting modern megacities, playing a vital role in guiding regional economic development and ensuring the reliable operation of transportation networks. With increasing urbanization, transportation demand continues to grow, placing higher demands on expressway service quality and efficiency. Interchanges are a key component of the expressway system, significantly impacting the mobility and efficiency of the entire transportation system. Shorter interchange spacing allows vehicles to more conveniently access expressway services, thereby improving accessibility. However, shorter spacing also means increased interchange density, negatively impacting operational efficiency, safety, and project costs. Therefore, to improve expressway operational efficiency, the spacing of interchanges should consider the combined impacts of traffic efficiency, traffic risk, accessibility, and construction costs.

[0003] Current research on interchange spacing primarily focuses on reducing traffic risks, using weaving volume, signage, driver reaction time, and speed change lane length as references to define minimum interchange spacing related to geometric design variables. Application No. CN201210140911 defines the scope of the ramp functional zone for driver safety within highway ramps, providing a calculation basis for the optimal spacing of highway interchanges. Existing patents rely on a single influencing factor and cannot guarantee the operational efficiency of highways. Furthermore, their implementation focuses on two adjacent interchanges, failing to reflect the impact of regional traffic demand along highways on interchange spacing in real-world applications.

[0004] Therefore, in order to ensure the comprehensive benefits of highways in terms of traffic efficiency, traffic risk, accessibility, and construction cost, it is necessary to design an evaluation method for highway interchange spacing schemes so that relevant transportation departments can plan interchange spacing that is conducive to improving highway operational efficiency in the context of urban expansion. Summary of the Invention

[0005] Purpose of the invention: The present invention aims to provide a method for evaluating the spacing schemes of highway interchanges, which is used to evaluate the operating benefits of different interchange spacing schemes. It can address the limitation of existing highway interchange spacing setting methods that cannot take into account multiple performance aspects such as highway traffic efficiency, traffic risk, accessibility, and construction cost. Moreover, with highways as the implementation object, it helps to select spacing schemes that meet the traffic needs of the areas along the highway, strengthen the connectivity of the highway transportation network, and promote the sustainable development of the urban agglomeration economy.

[0006] Technical Solution: To achieve the above objectives, the present invention designs a method for evaluating interchange spacing plans for highways. Taking highways as implementation objects, the present invention selects the interchange spacing plan that meets the traffic needs of the areas along the highway and optimizes the overall operational benefits of the highway through the following steps S1-S3:

[0007] S1: Based on the four operational influencing factors of traffic efficiency, traffic risk, accessibility, and construction cost, an evaluation index system for highway interchange spacing plans is constructed. Traffic efficiency includes two evaluation indicators: average speed and average delay; traffic risk is evaluated by traffic accident rate; accessibility is evaluated by comprehensive traffic accessibility; and construction cost is evaluated by project cost.

[0008] S2: Using the interchange spacing value as a variable, design an interchange spacing setting plan for the target expressway. At the same time, based on the traffic demand along the target expressway and taking townships as the basic units, establish a VISSIM simulation model to simulate the traffic flow operation status on the target expressway for each interchange spacing setting plan, and collect traffic flow operation status simulation data.

[0009] S3: Based on the number and location distribution of interchange spacings determined in step S2 and the target highway simulation data, evaluate each spacing scheme in terms of traffic efficiency, traffic risk, accessibility, and construction cost. Based on the numerical values ​​of the evaluation indicators, the entropy weight method is used to calculate the weights of each evaluation indicator. Then, using the TOPSIS comprehensive evaluation method and the evaluation indicator system described in step S1, a comprehensive evaluation of each interchange spacing scheme is performed. The schemes are ranked in descending order. The highest-ranked spacing scheme is the interchange spacing setting scheme that maximizes the overall operational efficiency of the target highway. This interchange spacing scheme is used to set the interchange spacing on the target highway.

[0010] As a comprehensive and optimal technical solution of the present invention, the evaluation indicators of traffic efficiency, traffic risk, accessibility, and construction cost in step S1 can be calculated as follows:

[0011] average speed It represents the average speed of all vehicles on the target expressway (including the main line and interchanges), in km / h, and is calculated as follows:

[0012]

[0013] Among them, v i represents the speed of vehicle i on the target highway (km / h); N represents the number of vehicle samples during the entire process of VISSIM simulation of traffic flow on the target highway

[0014] Average delay It represents the average delay of all vehicles on the target highway, its unit is s, and its calculation formula is:

[0015]

[0016] Among them, d i represents the delay of vehicle i on the target highway (s);

[0017] Traffic accident rate ∈ represents the accident rate per 100 million vehicle kilometers that increases exponentially with the increase of vehicle speed standard deviation. Its unit is: times / (km·10 -8 ·veh -1 ), the calculation formula is:

[0018] ∈=9.583exp 0.055σ (3)

[0019] Where σ represents the standard deviation of all vehicle speeds on the target highway,

[0020] Comprehensive traffic accessibility φ represents the comprehensive evaluation value of the accessibility of each township along the entire expressway area, and the calculation formula is:

[0021]

[0022] Among them, M i is the comprehensive aggregation scale of township i in the area along the target expressway, which is calibrated by the per capita income and population of township i; a i is the accessibility of township i; T is the set of townships along the target highway;

[0023] The project cost Ω represents the comprehensive construction cost of all interchanges on the target expressway, with the unit being 10,000 yuan. The calculation formula is:

[0024]

[0025] Where ρ is the density of interchanges on the target highway; l c , δ c , β c These are the relevant parameters for project cost.

[0026] As a comprehensive optimization technical solution of the present invention, the accessibility a of township i in the calculation formula of comprehensive traffic accessibility φ is i Calculated by the following formula:

[0027] Accessibility a of township i i The inverse of the distance from the township to the interchange entrance and exit is expressed as:

[0028]

[0029] Among them, L i is the comprehensive evaluation index value of road service level in township i; ij Represents the distance from township i to interchange entrance j, j∈R i ; R i represents the set of interchanges that can provide travel services for township i, R i The number of interchanges included is less than the number of interchanges set up on the target expressway according to the spacing plan;.

[0030] Comprehensive evaluation index of road service level in each township area L i The calculation formula is:

[0031]

[0032] Among them, α is the service level of roads in the township area, which is expressed by road grade, and the values ​​of expressway, main road, secondary road and branch road are assigned as 1, 2, 3 and 4 respectively; len α represents the length of the road with grade α; h α Indicates the evaluation index value of the road with grade α; Len i Represents the total length of roads passing through town i.

[0033] As a comprehensive and optimal technical solution of the present invention, the interchange spacing setting scheme for the target expressway in step S2 is designed with the interchange spacing value as a variable. At the same time, the VISSIM simulation model is modeled based on the overall operating environment of the target expressway, including the expressway mainline, the interchanges set according to the spacing scheme, and the expressway traffic demand environment (including the traffic demand environment along the line and the transit traffic demand environment). The simulation model is constructed as follows:

[0034] S21: Using the interchange spacing value as a variable, design several interchange spacing setting schemes for the target expressway;

[0035] S22: The mainline of the expressway is constructed based on the length, alignment, lane configuration, and lane width of the target expressway; interchanges are set based on the spacing plan;

[0036] S23: Based on the distance decay theory, the cumulative travel probability of the interchange to the areas at different distances from the interchange is used to allocate the traffic demand along the line to each interchange entrance and exit, so as to set the traffic demand environment along the expressway. The cumulative travel probability z of the interchange to the areas at different distances is t (l j ) is calculated as:

[0037]

[0038] Among them, z t (l j ) is the distance l from the interchange j j The cumulative travel probability from the kilometer area to the interchange; R is the interchange set on the target highway according to the spacing plan; ζ and ψ are the relevant parameters of the distance decay function;

[0039] S24: Input the number and location distribution of interchanges in steps S21-S23 and the constructed highway main line, interchanges, and traffic demand environment along the line into VISSIM, and build a simulation model in combination with the transit traffic demand data.

[0040] As a comprehensive optimization technical solution of the present invention, the specific process of evaluating the advantages and disadvantages of the interchange spacing scheme in step S3 is as follows:

[0041] S31: Based on the number of interchange spacing settings, location distribution and target highway simulation data in step S2, calculate the values ​​of the various evaluation indicators of traffic efficiency, traffic risk, accessibility and construction cost mentioned in step S1, and construct the initial data matrix X = [x ij ] m×n , x ij is the value of the jth evaluation index in the i-th spacing scheme, m is the number of interchange spacing schemes, and n is the number of evaluation indicators. The step transformation method is used to normalize each indicator to eliminate the influence of different indicator units on the evaluation results. The calculation formula is:

[0042]

[0043]

[0044] Among them, x jmax 、x jmin are the maximum and minimum values ​​of the jth evaluation index in all spacing schemes; in the evaluation index system described in S1, the average speed Comprehensive traffic accessibility φ is a benefit-based indicator; average delay Traffic accident rate ∈ and construction cost Ω are cost indicators.

[0045] S32: Calculate the entropy value e of each evaluation index j , the calculation formula is:

[0046]

[0047] Where, k = 1 / lnn; p ijis the weight of the jth evaluation index in the i-th spacing scheme, When p ij = 0, p ij lnp ij =0.

[0048] S33: Calculate the weight w of each evaluation index j , the calculation formula is:

[0049]

[0050] S34: The values ​​x' of each evaluation index after normalization based on formulas (9)-(10) in step S31 ij , let z ij =x' ij , construct the matrix [z ij ] m×n is the normalized decision matrix Z used for evaluation in TOPSIS, and its expression is as follows:

[0051]

[0052] Among them, m represents the number of spacing schemes, and the i-th spacing scheme is represented by A i Indicates, i=1,2,...,m; n represents the number of evaluation indicators, and the evaluation indicator j is determined by C j Indicates that j = 1, 2, ..., n; z ij is the value of the jth evaluation index in the i-th spacing scheme.

[0053] S35: Determine the ideal optimal spacing solution Z + and the ideal worst spacing solution Z - , the calculation formula is:

[0054]

[0055]

[0056] in, is the maximum value of the evaluation index j among all spacing schemes; is the minimum value of the evaluation index j among all spacing schemes.

[0057] S36: Calculate the Euclidean distance between the spacing scheme and the ideal optimal spacing scheme and the Euclidean distance from the ideal worst solution The calculation formula is:

[0058]

[0059]

[0060] in, It is divided into the value of evaluation index j in the ideal optimal (inferior) spacing scheme.

[0061] S37: Calculate the relative closeness S between the spacing scheme and the ideal optimal spacing scheme i , the calculation formula is:

[0062]

[0063] Where 0≤S i ≤1;

[0064] S38: The similarity value S of each spacing scheme calculated in step S37 i , which is the comprehensive score of each spacing scheme. The spacing schemes are arranged in descending order according to the comprehensive score. The spacing scheme with a larger comprehensive score is closer to the ideal optimal scheme. The spacing scheme with the highest comprehensive score is selected as the optimal setting for the interchange spacing of the target highway.

[0065] Beneficial effects: Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0066] 1. This invention's evaluation method for highway interchange spacing schemes constructs an evaluation index system for highway operational effectiveness based on four aspects: traffic efficiency, traffic risk, accessibility, and construction cost. Furthermore, it proposes a scheme evaluation method for regional highway interchange spacing that combines the VISSIM simulation model, the entropy weight method, and the TOPSIS comprehensive evaluation method. This highway interchange spacing scheme evaluation method targets the overall operational efficiency of highways, helps strengthen the connectivity of highway transportation networks within the region along highways, and promotes urbanization.

[0067] 2. This invention considers the overall benefits of expressways in terms of traffic efficiency, traffic risk, accessibility, and construction costs, and constructs a comprehensive evaluation index system for expressway operational effectiveness. This system meets the development needs of improving expressway access capacity within regions and urban agglomerations. In the context of promoting urban agglomeration development, setting interchange spacing to ensure efficient expressway operation requires consideration of multiple factors. This invention, based on a regional perspective, combines expressway routes with VISSIM simulation modeling to comprehensively evaluate multiple interchange spacing schemes, facilitating regional planning and decision-making for new and renovated expressways. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 The present invention provides a flowchart of a method for evaluating a plan for setting the spacing between interchanges on a highway according to an embodiment of the present invention.

[0069] Figure 2is a target highway section provided according to an embodiment of the present invention.

[0070] Figure 3 This is the demand environment along the target highway section provided according to an embodiment of the present invention.

[0071] Figure 4 It is a VISSIM simulation model of a target highway section provided according to an embodiment of the present invention. DETAILED DESCRIPTION

[0072] The following is a detailed description of the present invention in conjunction with the accompanying drawings. The embodiments are used to more clearly illustrate the technical solution of the present invention and are not intended to limit the scope of protection of the present invention.

[0073] An evaluation method for setting the spacing of highway interchanges designed in an embodiment of the present invention is to evaluate the spacing of highway interchanges on a target highway according to the following criteria: Figure 1 The following steps S1-S3 are performed to obtain an interchange spacing arrangement plan that optimizes the overall operational efficiency of the target expressway under the traffic demand conditions of the areas along the expressway:

[0074] S1: Based on the four operational influencing factors of traffic efficiency, traffic risk, accessibility, and construction cost, an evaluation index system for highway interchange spacing plans is constructed. Traffic efficiency includes two evaluation indicators: average speed and average delay; traffic risk is evaluated by traffic accident rate; accessibility is evaluated by comprehensive traffic accessibility; and construction cost is evaluated by project cost.

[0075] S2: The present invention takes the interchange spacing value as a variable, with a value range of 4 to 24 km, and designs a total of several highway interchange spacing setting schemes. The interchange spacing schemes are shown in Table 1. At the same time, based on the traffic demand of the area along the target highway, with townships as the basic units, for each interchange spacing setting scheme, a VISSIM simulation model is established to simulate the traffic flow operation status on the target highway, and the traffic flow operation status simulation data is collected. The target highway and its surrounding areas are as follows. Figure 2 The established VISSIM simulation model is as follows: Figure 3 The object is the overall operating environment of the target expressway, including the main line of the expressway, the interchanges set up according to the spacing plan, and the traffic demand environment of the expressway (including the traffic demand environment along the line and the transit traffic demand environment).

[0076] Table 1 Interchange spacing setting plan for target expressways

[0077] Spacing scheme <![CDATA[A1]]> <![CDATA[A2]]> <![CDATA[A3]]> <![CDATA[A4]]> <![CDATA[A5]]> <![CDATA[A6]]> <![CDATA[A7]]> <![CDATA[A8]]> <![CDATA[A9]]> <![CDATA[A 10 ]]> <![CDATA[A 11 ]]> Average spacing / km 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 Number of interchanges 43 35 29 25 21 19 17 15 14 13 12 Spacing scheme <![CDATA[A 12 ]]> <![CDATA[A 13 ]]> <![CDATA[A 14 ]]> <![CDATA[A 15 ]]> <![CDATA[A 16 ]]> <![CDATA[A 17 ]]> <![CDATA[A 18 ]]> <![CDATA[A 19 ]]> <![CDATA[A 20 ]]> <![CDATA[A 21 ]]> Average spacing / km 15.0 16.0 17.0 18.0 19.0 20.0 21.0 22.0 23.0 24.0 Number of interchanges 11 10 10 9 9 8 8 7 7 7

[0078] In one embodiment of the present invention, the Beijing-Hong Kong-Macao Expressway in Henan Province was used as an example. The target expressway is a two-way, eight-lane highway with a total length of 175 km and a lane width of 3.75 m. The area along the target expressway consists of 31 townships, each with a traffic demand of 1003 pcu / d. Based on the interchange spacing scheme, the distance decay method was used to calculate the traffic demand along each interchange. The transit traffic demand was calculated based on the ratio of transit traffic demand to route traffic demand = 3:17. A VISSIM simulation model was run to collect data related to evaluation indicators.

[0079] S3: Based on the number and location distribution of interchange spacings in step S2 and the simulation data for the target highway, evaluate each spacing scheme in terms of traffic efficiency, traffic risk, accessibility, and construction cost. Based on the numerical values ​​of the evaluation indicators, the entropy weight method is used to calculate the weights of each evaluation indicator. Then, using the TOPSIS comprehensive evaluation method and the evaluation indicator system described in step S1 as the standard, comprehensively evaluate the advantages and disadvantages of each interchange spacing scheme and rank them in descending order. The highest-ranked spacing scheme is the interchange spacing setting scheme that achieves the highest overall operational efficiency for the target highway. This interchange spacing scheme is used to set the interchange spacing on the target highway.

[0080] In step S3, the values ​​of the evaluation indicators of traffic efficiency, traffic risk, accessibility, and construction cost described in step S1 are calculated based on the number and location distribution of the interchange spacing in step S2 and the simulation data of the target highway, and the initial data matrix X = [x ij ] m×n ;

[0081] In one embodiment, based on the entropy weight method, the constructed initial data matrix X is normalized and the entropy value e of each evaluation index is calculated. j , and further calculate the weight w of each evaluation index j ;The weights of each evaluation index are shown in Table 2;

[0082] Table 2 Evaluation index weights of interchange spacing scheme

[0083] Evaluation indicators average speed Average delay Traffic accident rate Comprehensive transportation accessibility Project Cost <![CDATA[Weight w j > 0.20211 0.25285 0.16918 0.13340 0.24246

[0084] Based on the TOPSIS comprehensive evaluation scheme, the normalized data matrix obtained in step 31 is used to construct the normalized decision matrix Z. The normalized decision matrix Z is shown in Table 3.

[0085] Table 3 Standardized decision matrix for evaluation of interchange spacing schemes

[0086]

[0087]

[0088] According to step S35, the ideal optimal (inferior) spacing scheme is determined, and the Euclidean distance between each spacing scheme and the ideal optimal (inferior) spacing scheme is calculated. Further calculation is performed to obtain the relative closeness S between each spacing scheme and the ideal optimal spacing scheme. i , which is the comprehensive score of the scheme. The comprehensive scores and ranking results of each spacing scheme are shown in Table 4. According to Table 4, the interchange spacing scheme with the highest comprehensive score and the highest ranking is the optimal scheme. That is, in this embodiment, the average interchange spacing on the target expressway should be set to 14 km.

[0089] Table 4 Evaluation results of target expressway interchange spacing schemes

[0090] Spacing scheme <![CDATA[A1]]> <![CDATA[A2]]> <![CDATA[A3]]> <![CDATA[A4]]> <![CDATA[A5]]> <![CDATA[A6]]> <![CDATA[A7]]> <![CDATA[A8]]> <![CDATA[A9]]> <![CDATA[A 10 ]]> <![CDATA[A 11 ]]> Average spacing / km 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 Comprehensive score 0.49 0.39 0.59 0.63 0.55 0.63 0.62 0.66 0.65 0.48 0.66 Sorting 13 20 8 5 10 4 6 2 3 14 1 Spacing scheme <![CDATA[A 12 ]]> <![CDATA[A 13 ]]> <![CDATA[A 14 ]]> <![CDATA[A 15 ]]> <![CDATA[A 16 ]]> <![CDATA[A 17 ]]> <![CDATA[A 18 ]]> <![CDATA[A 19 ]]> <![CDATA[A 20 ]]> <![CDATA[A 21 ]]> Average spacing / km 15.0 16.0 17.0 18.0 19.0 20.0 21.0 22.0 23.0 24.0 Comprehensive score 0.39 0.60 0.36 0.58 0.52 0.42 0.50 0.39 0.42 0.44 Sorting 19 7 21 9 11 16 12 18 17 15

[0091] The above embodiments in conjunction with the accompanying drawings are only used to illustrate the technical solutions of the present invention in detail and cannot be used to limit the scope of protection of the present invention. Those skilled in the art may make various changes and modifications based on their knowledge, but it should be noted that all changes and modifications within the spirit and basic features of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for evaluating the spacing between interchanges on a highway, characterized in that: The evaluation method includes the following evaluation steps: S1: Based on the four operational influencing factors of traffic efficiency, traffic risk, accessibility, and construction cost, an evaluation index system for highway interchange spacing plans is constructed. Traffic efficiency includes two evaluation indicators: average speed and average delay; traffic risk is evaluated by traffic accident rate; accessibility is evaluated by comprehensive traffic accessibility; and construction cost is evaluated by project cost. S2: Using the interchange spacing value as a variable, design an interchange spacing setting scheme for the target expressway. Based on the traffic demand along the target expressway and taking townships as the basic unit, establish a VISSIM simulation model to simulate the traffic flow operation status on the target expressway for each interchange spacing setting scheme, and collect traffic flow operation status simulation data. S3: Based on the number and location distribution of interchange spacing settings in step S2 and the simulation data of the target expressway, the evaluation indicators of each spacing scheme in terms of traffic efficiency, traffic risk, accessibility, and construction cost are calculated. According to the evaluation indicator values, the weight of each evaluation indicator is calculated using the entropy weight method; based on the TOPSIS comprehensive evaluation method, the evaluation indicator system described in step S1 is used as the standard to comprehensively evaluate each interchange spacing scheme, and each scheme is arranged in descending order. The highest-ranked spacing scheme is the interchange spacing setting scheme that achieves the highest comprehensive operating efficiency of the target expressway. This interchange spacing scheme is used to set the interchange spacing on the target expressway; In step S2, the interchange spacing setting scheme for the target expressway is designed with the interchange spacing value as a variable. The VISSIM simulation model is modeled based on the overall operating environment of the target expressway, including the expressway mainline, the interchanges set according to the spacing scheme, and the expressway traffic demand environment, which includes the traffic demand environment along the expressway and the transit traffic demand environment. The simulation model is constructed as follows: S21: Using the interchange spacing value as a variable, design several interchange spacing setting schemes for the target expressway; S22: The mainline of the expressway is constructed based on the length, alignment, lane configuration, and lane width of the target expressway, and interchanges are set based on the spacing plan; S23: Based on the distance decay theory, the cumulative travel probability of the interchange to the areas at different distances from the interchange is used to allocate the traffic demand along the line to each interchange entrance and exit, so as to set the traffic demand environment along the expressway. The cumulative travel probability z of the interchange to the areas at different distances is t (l j ) is calculated as: Among them, z t (l j ) is the distance l from the interchange j j The cumulative travel probability from a kilometer area to the interchange; R is the set of interchanges set on the target highway according to the spacing plan; ζ and ψ are the relevant parameters of the distance decay function; S24: Input the number and location distribution of interchanges in steps S21-S23 and the constructed highway main line, interchanges, and traffic demand environment along the line into VISSIM, and build a simulation model in combination with the transit traffic demand data.

2. The evaluation method for setting the spacing between interchanges on a highway according to claim 1, characterized in that: In the evaluation index system constructed in step S1, the evaluation indicators of traffic efficiency, traffic risk, accessibility, and construction cost are calculated as follows: average speed It represents the average speed of all vehicles on the target highway, in km / h, and is calculated as follows: Among them, v i represents the speed of vehicle i on the target highway; N represents the number of vehicle samples during the entire process of VISSIM simulation of traffic flow on the target highway; Average delay It represents the average delay of all vehicles on the target highway, its unit is s, and its calculation formula is: Among them, d i represents the delay of vehicle i on the target highway; Traffic accident rate ∈ represents the accident rate per 100 million vehicle kilometers that increases exponentially with the increase of vehicle speed standard deviation. Its unit is: times / (km·10 -8 ·veh -1 ), the calculation formula is: ∈=9.583exp 0.055σ (3) Where σ represents the standard deviation of all vehicle speeds on the target highway, Comprehensive traffic accessibility φ represents the comprehensive evaluation value of the accessibility of each township along the entire target expressway area, and the calculation formula is: Among them, M i is the comprehensive aggregation scale of township i in the area along the target expressway, which is calibrated by the per capita income and population of township i; a i is the accessibility of township i; T is the set of townships along the target highway; The project cost Ω represents the comprehensive construction cost of all interchanges on the target expressway, and its unit is 10,000 yuan. The calculation formula is: Where ρ is the density of interchanges on the target highway; l c , δ c , β c These are the relevant parameters for project cost.

3. The evaluation method for setting the spacing between interchanges on a highway according to claim 2, characterized in that: The accessibility a of township i in the calculation formula of comprehensive transportation accessibility φ i Calculated by the following formula: Accessibility a of township i i The inverse of the distance from the township to the interchange entrance and exit is expressed as: Among them, L i is the comprehensive evaluation index value of road service level in township i; ij Represents the distance from township i to interchange entrance j, j∈R i ; R i represents the set of interchanges that can provide travel services for township i, R i The number of interchanges included in is less than the number of interchanges to be provided on the target expressway according to the spacing plan; Comprehensive evaluation index of road service level in each township area L i The numerical value is calculated as follows: Among them, α is the service level of roads in the township area, which is expressed by road grade, and the values ​​of expressway, main road, secondary road and branch road are assigned as 1, 2, 3 and 4 respectively; len α represents the length of the road with grade α; h α Indicates the evaluation index value of the road with grade α; Len i Represents the total length of roads passing through town i.

4. The evaluation method for setting the spacing between interchanges on a highway according to claim 1, characterized in that: The specific process of evaluating the advantages and disadvantages of the interchange spacing scheme in step S3 is as follows: S31: Based on the number of interchange spacing settings, location distribution and target highway simulation data in step S2, calculate the values ​​of the various evaluation indicators of traffic efficiency, traffic risk, accessibility and construction cost mentioned in step S1, and construct the initial data matrix X = [x ij ] m×n , x ij is the value of the jth evaluation index in the i-th spacing scheme, m is the number of interchange spacing schemes, and n is the number of evaluation indicators. The step transformation method is used to normalize each indicator to eliminate the influence of different indicator units on the evaluation results. The calculation formula is: Among them, x jmax 、x jmin are the maximum and minimum values ​​of the jth evaluation index in all spacing schemes; in the evaluation index system described in S1, the average speed Comprehensive traffic accessibility φ is a benefit-based indicator; average delay Traffic accident rate ∈ and construction cost Ω are cost indicators; S32: Calculate the entropy value e of each evaluation index j , the calculation formula is: Where, k = 1 / lnn; p ij is the weight of the jth evaluation index in the i-th spacing scheme, When p ij = 0, p ij lnp ij =0; S33: Calculate the weight w of each evaluation index j , the calculation formula is: S34: The values ​​x' of each evaluation index after normalization based on formulas (9)-(10) in step S31 ij , let z ij =x' ij , construct the matrix [z ij ] m×n is the normalized decision matrix Z used for evaluation in TOPSIS, and its expression is as follows: Among them, m represents the number of spacing schemes, and the i-th spacing scheme is represented by A i Indicates, i=1,2,...,m; n represents the number of evaluation indicators, and the evaluation indicator j is determined by C j Indicates that j = 1, 2, ..., n; z ij is the value of the jth evaluation index in the i-th spacing scheme; S35: Determine the ideal optimal spacing solution Z + and the ideal worst spacing solution Z - , the calculation formula is: in, is the maximum value of the evaluation index j among all spacing schemes; is the minimum value of the evaluation index j among all spacing schemes, j = 1, 2, ..., n; S36: Calculate the Euclidean distance between the spacing scheme and the ideal optimal spacing scheme and the Euclidean distance from the ideal worst solution The calculation formula is: in, and are the values ​​of evaluation index j in the ideal optimal and worst spacing schemes respectively; S37: Calculate the relative closeness S between the spacing scheme and the ideal optimal spacing scheme i , the calculation formula is: Where 0≤S i ≤1; S38: The similarity value S of each spacing scheme calculated in step S37 i , which is the comprehensive score of each spacing scheme. The spacing schemes are arranged in descending order according to the comprehensive score. The spacing scheme with a larger comprehensive score is closer to the ideal optimal scheme. The spacing scheme with the highest comprehensive score is selected as the optimal setting for the interchange spacing of the target highway.

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