CN111260947B - An analysis method of road network reachable range based on flooding algorithm - Google Patents

Abstract

The invention discloses a road network reachable range analysis method based on a flooding algorithm, and belongs to the technical field of traffic area reachability. For a selected vehicle A, determining a traffic area range by using maximum speed and time, adding road numbers in the range into a road network Set _ way, screening, adding start and end point numbers corresponding to each screened road into a road node Set _ node, and constructing a road network node class by using all node numbers: meanwhile, constructing a road network connection edge class according to the road numbers in the screened road network Set _ way; connecting the N road network node classes and the M road network connecting edge classes to construct a road network model; and finally, simulating the running of the selected vehicle A in the road network model by adopting a recursive flooding algorithm to obtain a reachable road network list, and distributing tasks for the vehicle A to realize accurate transportation operation. Compared with the existing method, the method is more accurate and the complexity of the calculation process is low.

Description

An analysis method of road network reachable range based on flooding algorithm

technical field

The invention belongs to the technical field of accessibility of traffic areas, in particular to a method for analyzing the reachability of a road network based on a flooding algorithm.

Background technique

Vehicle accessibility analysis refers to a specific vehicle, comprehensively considering space and time factors, to find the traffic area that the vehicle can reach within a specified time.

Vehicle accessibility analysis is a hot issue in logistics distribution and urban intelligent transportation research. For a logistics company, the coverage of its logistics service business is an important criterion for measuring its service capability. Whether a distribution center can be reasonably selected and the configuration of distribution vehicles are the keys to achieving full coverage of logistics services, and accurate accessibility analysis is the key to achieving full coverage of logistics services. It is an indispensable part of the optimal decision-making of the problem; for urban traffic, accurate analysis of the accessibility of vehicles such as taxis and online car-hailing in the city can provide guidance for the rational allocation of urban traffic resources, so as to effectively solve urban traffic congestion and Unreasonable allocation of resources, etc.

The flooding algorithm refers to: in the network, a packet sent from any node through a router will be sent to all other nodes connected to the router, which is a kind of fast dissemination of routing update information to each node of the entire large network. method. In the prior art, the flooding algorithm is mainly used in the field of data communication systems to realize the transmission and exchange of data packets between host networks. However, flooding algorithms are rarely used in the transportation domain.

At present, most of the existing vehicle reachable area calculation methods are based on vehicle trajectories, grid the traffic area according to the distance between the vehicle query point and the boundary point, and then analyze based on the shortest path to obtain the vehicle reachable area. Another improvement method introduces the influence of different time periods on the reachable area.

However, these methods are based on the spatial and temporal constraints of the area between the vehicle query point and the boundary point, and do not accurately analyze the characteristics of different roads in the traffic area. For logistics and distribution problems in remote areas, traffic and road conditions are often very complex. In addition to time constraints, issues such as road height and weight restrictions will also affect transportation. Therefore, the accessibility analysis of the above methods has limited application scope and insufficient accuracy.

SUMMARY OF THE INVENTION

In view of the above problems, the present invention provides a method for analyzing the reachable range of a road network based on a flooding algorithm, which constructs a road network according to the characteristics of different roads in a traffic area, and applies the flooding algorithm to the traffic road network to simulate the driving process of vehicles. , to carry out a more accurate reachability analysis of the vehicle. Compared with the common vehicle reachability analysis, the present invention takes into account the complexity of the roads in the traffic area, has a wide application range, and significantly improves the accuracy of the results obtained by the analysis.

The specific steps of the method for analyzing the reachable range of the road network based on the flooding algorithm are as follows:

Step 1: Set a given time as t, for a selected vehicle A, use the maximum speed v of vehicle A to determine the traffic area range, and add the road numbers within the range to the road network set Set_way.

The traffic area range includes: set the given time as t and the selected maximum speed of the vehicle as v, then the determined traffic area range is a circle made with the vehicle position as the center and vt as the radius.

Step 2: Screen all roads in the road network set Set_way according to the vehicle A information;

According to the height, width and load of the vehicle, the roads in the area are screened, and it is judged in turn whether the road and vehicle information in the selected traffic area match, and the roads that do not meet the restrictions on height, width, load, and vehicle type are removed from the road network set Set_way. The remaining roads that meet the conditions are used for the construction of the road network.

The filtered road network set Set_way={wgid1, wgid2, .

Step 3: Select each road in turn from the filtered road network set Set_way, and add the corresponding start and end numbers of each road to the road node set Set_node;

Set Set_node={ngid1,ngid2,...,ngidN}; ngidN is the Nth node number selected from the road in Set_way.

Step 4. Build all the node numbers in the road node set Set_node into a road network node class:

There are N objects in the road node set Set_node, then N road network node classes Node_way are generated to form the road network node class set Set<Node_way>, Set<Node_way>={Node_way1,Node_way2,...,Node_wayp,...,Node_wayq, ...,Node_wayN};

Each node class Node_way contains a node number ngid, a set Set<Linked_way> composed of multiple road network edge classes, and a flood time value flood_time.

The node number ngid corresponds to the number in the set Set_node; the elements of the set Set<Linked_way> are all the road network edges connected to the node; the flooding time value flood_time represents the remaining time value of the last flooding from this node, The default value is 0.

Step 5. Build a road network edge class according to the road number in the filtered road network set Set_way;

There are M objects in the road network set Set_way, and M road network edge classes Link_way are generated to form the road network edge class set Set<Link_way>={Link_way1,Link_way2,...,Link_waym,...,Link_wayM};

Each link class Link_way contains a road number information wgid, a travel time information travel_time, and a road network node class Node_target.

The road number information wgid corresponds to the number in the set Set_way; the travel_time value is the saved time of passing each road; Node_target stores the road network node Node_way pointed to by the road edge type Link_way.

Step 6: Connect the N road network node classes and the M road network edge classes to construct a road network model.

Connection refers to: assigning a value to each edge class in the set Set<Link_way>, adding the node Node_target, and adding it to the set Set<Linked_way> of the corresponding road network node class;

Specifically: for the edge type Link_waym, according to the corresponding road number wgidm value, obtain the corresponding road information in the database; the road information includes the passing time, the end point number and the start point number;

Assign the travel_time of the edge class Link_waym to the passing time of the corresponding road;

According to the end point number obtained by the road number wgidm, the road network node class Node_wayp corresponding to the end point number is found in the road network node class set Set<Node_way>, as the value of the node_target corresponding to the link class Link_waym.

At the same time, according to the starting point number obtained by the road number wgidm, find the road network node class Node_wayq corresponding to the starting point number in the set Set<Node_way>, and add the edge class Link_waym to the set<Linked_way> corresponding to the road network node class Node_wayq. .

Step 7, using a recursive flooding algorithm to simulate the driving of the selected vehicle A in the road network model to obtain a list of accessible road networks;

Specifically:

Step 701: Build the running position and state of the simulated vehicle A into a package class Packet_car and initialize it, and define the reachable road network set Set_arrived at the same time;

The package class Packet_car contains the life cycle of vehicle A and the set Set_router;

The initial value of the life cycle is counter;

The set Set_router is used to record the information of the road network edge passed by the packet, which is composed of the number of the road network edge passed by the packet, and the initial value is empty;

The reachable road network set Set_arrived is used to store the road network edge number that vehicle A finally experiences, and the initial value is empty.

Step 702: Find the road network node closest to the vehicle A in the road network node class set Set<Node_way> as the source point, denoted as Node_way0, and receive the packet class Packet_car;

Set the lifetime value counter to t ₀ .

Step 703, determine whether t ₀ is greater than 0, if so, go to step 704; otherwise, the packet has ended, go to step 708;

Step 704, determine whether t ₀ is greater than the flooding time in the road network node, if so, go to step 705; otherwise, the packet is an invalid packet, go to step 708;

Step 705: Determine whether there is a link that does not exist in the set Set_router in the link set Set<Linked_way> of the current road network node, if so, go to step 706; otherwise, the road network node has been flooded, go to step 708;

Step 706, create a new package Packet_new, and its time is t ₀ -t _w , and add the non-existing edge number to the set Set_router of the package Packet_new;

t _w corresponds to the travel_time of each network connection.

The specific process of adding the edge number is as follows:

Determine whether the number of the added edge is 1. If so, add the corresponding edge number to the Set_router of the package Packet_new. Otherwise, when the number of edge numbers is greater than 1, according to each time t ₀ - The difference value of t _w , select the connection edge corresponding to the time with the largest difference value, and add the connection edge number to the set Set_router of the packet Packet_new.

Step 707: Use the node Node_way1 pointed to by the edge number added in the set Set_router of the packet Packet_new as the next road network node for receiving the packet Packet_new, and update the flooding time travel_time of the node Node_way1 to t ₀ , return to step 703, start The flooding of a new group is calculated until it is judged that t ₀ -t _w is 0.

Step 708: Store the road network connection number in the set Set_router into the initially defined set Set_arrived and remove duplicates, and the algorithm ends;

The road network connection number in the set Set_router is the reachable road network list of vehicle A.

Step 8: Assign tasks to vehicle A according to the reachable road network list obtained in the road network model, so as to realize precise transportation operations.

The advantages and positive effects of the present invention are:

1), a kind of road network reachable range analysis method based on flooding algorithm of the present invention, fully considering the complexity of the road in the traffic area around the vehicle, screening according to its road characteristics, and considering the passing time of each route separately, Constructing a road network model is more accurate than existing methods, and the results are more similar to the actual situation.

2), a kind of road network reachable range analysis method based on flooding algorithm of the present invention, adopts flooding algorithm, simulates the operation of vehicles with packets transmitted between nodes, and at the same time carries out certain optimization according to the characteristics of the road network, the calculation process. It has the characteristics of low time complexity.

Description of drawings

Fig. 1 is the flow chart of a kind of road network reachability analysis method based on flooding algorithm of the present invention;

Fig. 2 is the method flow chart that the present invention adopts recursive flooding algorithm to calculate reachable road network list;

FIG. 3 is an embodiment of the present invention for explaining the recursive flooding algorithm.

Detailed ways

In order to facilitate the understanding and implementation of the present invention by those of ordinary skill in the art, the present invention will be further described in detail and in-depth below with reference to the accompanying drawings.

The method for analyzing the reachability of the vehicle road network based on the flooding algorithm provided by the present invention is suitable for analyzing the accessibility of a specific vehicle at a given time, and finally can calculate the traffic area that the vehicle may reach within a limited time; The process is: first determine the traffic area range according to the input vehicle information and time information, then filter the roads in the area according to the vehicle characteristics, and then construct the road network that meets the requirements in the selected area as a specific road network model, and use the recursive flooding algorithm. The list of reachable road networks is obtained by simulating vehicle driving in the road network, and finally assigns tasks to corresponding transport vehicles according to the reachable results to achieve precise transport operations.

As shown in Figure 1, the specific steps are as follows:

Step 1: Set a given time as t, for a selected vehicle A, use the maximum speed v of vehicle A to determine the traffic area range, and add the road numbers within the range to the road network set Set_way.

The traffic area range includes all possible areas that vehicle A can reach within a limited time. The determination process is as follows:

First, input the coordinates of vehicle A (lat, lon), the maximum speed of the vehicle v and the limited time t; then, take the coordinates of vehicle A (lat, lon) as the center and vt as the radius to make a circle C, and the range of the circle C is the traffic area Extent; add road numbers within circle C to the road network set Set_way.

The selected traffic area needs to include all possible areas that vehicles can reach within a limited time, so as to ensure the accuracy of subsequent analysis and calculation. At the same time, the area here needs to be as small as possible, so as to reduce invalid calculation in the process of subsequent analysis and calculation. Therefore, the circle C is selected as the selected area, and the circle C is the minimum area under the premise of ensuring that all possible areas are included.

Step 2: Screen all roads in the road network set Set_way according to the vehicle A information;

The information of vehicle A includes: height is height, width is width and load is load, each road in the road network set Set_way is retrieved from the database in turn, and the height, width and load information of each road are respectively related to the height, Width and load are compared, and roads that do not meet the height, width and load information of vehicle A are removed from the road network set Set_way.

The filtered road network set Set_way={wgid1, wgid2, .

The purpose of screening in this step is to eliminate the road network that is not passable by the vehicle. In the distribution problems in some remote areas, there are a large number of roads with poor road conditions and long-term disrepair. It is very important to eliminate these roads and then conduct accessibility analysis to improve the accuracy of the results.

Step 3: Select each road in turn from the filtered road network set Set_way, and add the corresponding start and end numbers of each road to the road node set Set_node;

Set Set_node={ngid1,ngid2,...,ngidN}; ngidN is the Nth node number selected from the road in Set_way.

Step 4. Build all the node numbers in the road node set Set_node into a road network node class:

There are N objects in the road node set Set_node, then N road network node classes Node_way are generated to form the road network node class set Set<Node_way>, Set<Node_way>={Node_way1,Node_way2,...,Node_wayp,...,Node_wayq, ...,Node_wayN};

Each node class Node_way is abstracted from the intersection of different roads in the area, and includes a node number ngid, a set of multiple road network connection edge classes Set<Linked_way> and a flood time value flood_time.

The node number ngid corresponds to the number in the set Set_node; the set Set<Linked_way> represents the road connected to the node, and the elements in the set are the numbers of all road network edges connected to the node; the flood time value flood_time represents the last time The remaining time value when flooding from this node, the default value is 0.

Step 5. Build a road network edge class according to the road number in the filtered road network set Set_way;

There are M objects in the road network set Set_way, and M road network edge classes Link_way are generated to form the road network edge class set Set<Link_way>={Link_way1,Link_way2,...,Link_waym,...,Link_wayM};

Each link class Link_way is abstracted from a single road in the area, and contains a road number information wgid, a travel time information travel_time, and a road network node class Node_target.

The road number information wgid corresponds to the number in the set Set_way; the travel_time value is the saved time of passing each road; Node_target represents the road network node pointed to by the link, and stores the road network node Node_way pointed to by the road link class Link_way .

Step 6: Connect the N road network node classes Node_way and the M road network edge classes Link_way to construct a road network model.

Connection refers to: assigning a value to each edge class in the set Set<Link_way>, and adding the node Node_target; at the same time, adding it to the set Set<Linked_way> of the corresponding road network node class;

Specifically: for the edge type Link_waym, according to the corresponding road number wgidm value, obtain the corresponding road information in the database; the road information includes the passing time, the end point number and the start point number;

Assign the travel_time of the edge class Link_waym to the passing time of the corresponding road;

According to the end point number obtained by the road number wgidm, the road network node class Node_wayp corresponding to the end point number is found in the road network node class set Set<Node_way>, as the value of the node_target corresponding to the link class Link_waym.

At the same time, according to the starting point number obtained by the road number wgidm, find the road network node class Node_wayq corresponding to the starting point number in the set Set<Node_way>, and add the edge class Link_waym to the set<Linked_way> corresponding to the road network node class Node_wayq. .

Step 7, using a recursive flooding algorithm to simulate the driving of the selected vehicle A in the road network model to obtain a list of accessible road networks;

When implementing the flooding calculation, the present invention provides a packet class Packet_car as the medium that propagates in the network in the flooding algorithm, and simulates the running position and state of the vehicle. First, according to the vehicle information, find the node closest to the vehicle as the source point in the nodes, and establish a packet with the initial time as the input time, so that the source point receives the packet and starts the recursive flooding calculation.

As shown in Figure 2, it is specifically:

Step 701: Build the running position and state of the simulated vehicle A into a package class Packet_car and initialize it, and define the reachable road network set Set_arrived at the same time;

The package class Packet_car contains the life cycle of vehicle A and the set Set_router;

The initial value of the life cycle is counter, which is used to record the time remaining in the vehicle operation.

The set Set_router is used to record the information of the road network edge passed by the packet, which is composed of the number of the road network edge passed by the packet, and the initial value is empty;

The reachable road network set Set_arrived is used to store the number of reachable road network edges that vehicle A finally experiences, and the initial value is empty.

Step 702: Find the road network node closest to the vehicle A in the road network node class set Set<Node_way> as the source point, denoted as Node_way0, and receive the packet class Packet_car;

Set the lifetime value counter to t ₀ .

Step 703, determine whether t ₀ is greater than 0, if so, go to step 704; otherwise, the package has ended its life cycle, go to step 708;

Step 704, determine whether t ₀ is greater than the flooding time in the road network node, if so, go to step 705; otherwise, the packet is an invalid packet, go to step 708;

Step 705: Determine whether there is a link that does not exist in the set Set_router in the link set Set<Linked_way> of the current road network node, if so, go to step 706; otherwise, the road network node has been flooded, go to step 708;

Step 706, create a new package Packet_new, and its time is t ₀ -t _w , add the non-existing edge number to the set Set_router and use it as the path set Set_router of the package Packet_new;

t _w corresponds to the travel_time of each network connection.

The specific process of adding the edge number is as follows:

Determine whether the number of the added edge is 1. If so, add the corresponding edge number to the set Set_router. Otherwise, when the number of edge numbers is greater than 1, according to each time t ₀ -t _w Difference, select the edge corresponding to the time with the largest difference, and add the edge number to the set Set_router.

As shown in Figure 3, determine whether the packet received by the node is valid: that is, determine whether the remaining time of the packet is greater than the flooding time recorded by the node, if so, it is a valid packet and floods it, otherwise it is an invalid packet, Finish.

The recursive flooding calculation starts from source point O. Suppose node B receives the packet twice, from source point O and node A, respectively. When node B receives the packet from node A and performs flooding calculation, the remaining time of the packet If it is less than the remaining time of the packet from node O, the result of its flooding calculation must be included in the calculation result of the packet from node O, so node B receives the packet from node A and performs flooding calculation as Invalid calculation. The invention judges whether the packet is an invalid packet by comparing the remaining time in the packet with the node flooding time before the flooding calculation starts, so as to avoid the calculation of the invalid packet.

Step 707: Use the node Node_way1 pointed to by the edge number added in the set Set_router of the packet Packet_new as the next road network node for receiving the packet Packet_new, and update the flooding time travel_time of the node Node_way1 to t ₀ , return to step 703, and proceed to Recursively, start a new set of flooding calculations until it is judged that t ₀ -t _w is 0.

Step 708: Store the road network connection number in the set Set_router into the initially defined set Set_arrived and remove duplicates, and the algorithm ends;

The road network connection number in the set Set_router={wgid1,wgid2,...,wgidK} is the reachable road network list of vehicle A.

When the flooding algorithm of recursive transmission is completed, it means that all the packages used to simulate the running of the vehicle have completed their life cycle. At this time, the number recorded in Set_arrived is the road number that a specific vehicle can reach within a limited time. The road numbers are deduplicated and sorted and output, and the vehicle accessibility analysis is completed.

Step 8: Assign tasks to vehicle A according to the reachable road network list obtained in the road network model, so as to realize precise transportation operations.

Display the road number results that a specific vehicle A can reach with the help of a graphical interface or borrow other devices for analysis, assign tasks to the corresponding transport vehicles, and achieve precise transport operations.

The invention establishes a special road network model according to the characteristics of the traffic road, fully considers the complexity of different roads in the area, selects and builds the network according to the specific road, so that the accessibility analysis result is accurate and the application range is wide; The information is extracted from the database into the model, which provides a carrier for subsequent recursive flooding calculations.

The present invention uses a flooding algorithm to simulate the operation of the vehicle. In the prior art, the flooding algorithm is mainly applied in the field of data communication systems, and is rarely used in the field of traffic. The flooding algorithm performs recursive transmission of media packets in the network, each packet can represent the running vehicle, and the relevant parameters of the packet represent the position and status information of the running vehicle. By analyzing the transmission of each packet in the network, accurate reachability analysis results can be obtained.

At the same time, the flooding algorithm is optimized for the vehicle problem. For the special situation of simulated vehicle operation, the packets received by some nodes will be invalid packets. If the ordinary flooding algorithm is used, there will be some invalid calculations, which will consume a lot of time. The invention optimizes the algorithm, increases the steps of judging the validity of the packet, avoids the invalid calculation of this part, and reduces the time complexity of the algorithm.

For a specific vehicle, the invention takes into account the complexity of the roads in the surrounding area, constructs the road network, uses the flooding algorithm to analyze the accessibility of the vehicle, and obtains and outputs the result. Compared with the existing method, the obtained reachable road network has high accuracy, and the method and the device have wide application range. In particular, for some areas with complex traffic conditions, the method and device provided by the present invention can accurately determine whether the road allows vehicles to pass, so that the unpassable roads are eliminated before the time-space reachability analysis is performed, which makes the results more accurate. Sex is greatly improved.

Claims (5)

1. a road network reachability analysis method based on flooding algorithm, is characterized in that, concrete steps are as follows: Step 1. Set the given time as t, and for a selected vehicle A, determine the traffic area range by using the maximum speed v of the vehicle A, and add the road numbers within the range to the road network set Set_way; Step 2: Screen all roads in the road network set Set_way according to the vehicle A information; The filtered road network set Set_way={wgid1,wgid2,...,wgidM}; wgidM is the M-th road number that matches the height, width and load information of vehicle A; Step 3: Select each road in turn from the filtered road network set Set_way, and add the corresponding start and end numbers of each road to the road node set Set_node; Set Set_node={ngid1,ngid2,...,ngidN}; ngidN is the Nth node number selected from the road in Set_way; Step 4. Build all the node numbers in the road node set Set_node into a road network node class: There are N objects in the road node set Set_node, then N road network node classes Node_way are generated to form the road network node class set Set<Node_way>, Set<Node_way>={Node_way1,Node_way2,...,Node_wayp,...,Node_wayq, ...,Node_wayN}; Each node class Node_way contains a node number ngid, a set Set<Linked_way> composed of multiple road network edge classes, and a flood time value flood_time; The node number ngid corresponds to the number in the set Set_node; the elements of the set Set<Linked_way> are all the road network edges connected to the node; the flooding time value flood_time represents the remaining time value of the last flooding from this node, The default value is 0; Step 5. Build a road network edge class according to the road number in the filtered road network set Set_way; There are M objects in the road network set Set_way, and M road network edge classes Link_way are generated to form the road network edge class set Set<Link_way>={Link_way1,Link_way2,...,Link_waym,...,Link_wayM}; Each edge class Link_way contains a road number information wgid, a travel time information travel_time, and a road network node class Node_target; The road number information wgid corresponds to the number in the set Set_way; the travel_time value is the saved time of passing each road; Node_target stores the road network node Node_way pointed to by the road edge class Link_way; Step 6: Connect the N road network node classes and the M road network edge classes to construct a road network model; Connection refers to: assigning a value to each edge class in the set Set<Link_way>, adding the node Node_target, and adding it to the set Set<Linked_way> of the corresponding road network node class; Step 7, using a recursive flooding algorithm to simulate the driving of the selected vehicle A in the road network model to obtain a list of accessible road networks; Specifically: Step 701: Build the running position and state of the simulated vehicle A into a package class Packet_car and initialize it, and define the reachable road network set Set_arrived at the same time; The package class Packet_car contains the life cycle of vehicle A and the set Set_router; The initial value of the life cycle is counter; The set Set_router is used to record the information of the road network edge passed by the packet, which is composed of the number of the road network edge passed by the packet, and the initial value is empty; The reachable road network set Set_arrived is used to store the road network edge number that vehicle A finally experiences, and the initial value is empty; Step 702: Find the road network node closest to the vehicle A in the road network node class set Set<Node_way> as the source point, denoted as Node_way0, and receive the packet class Packet_car; Set the lifetime value counter to t ₀ ; Step 703, determine whether t ₀ is greater than 0, if so, go to step 704; otherwise, the packet has ended, go to step 708; Step 704, determine whether t ₀ is greater than the flooding time in the road network node, if so, go to step 705; otherwise, the packet is an invalid packet, go to step 708; Step 705: Determine whether there is a link in the set Set<Linked_way> of the current road network node that does not exist in the set Set_router, if so, go to step 706; otherwise, the road network node has been flooded, go to step 708; Step 706, create a new package Packet_new, and its time is t ₀ -t _w , and add the non-existing edge number to the set Set_router of the package Packet_new; t _w corresponds to the travel_time of each network connection; Step 707: Use the node Node_way1 pointed to by the edge number added in the set Set_router of the packet Packet_new as the next road network node for receiving the packet Packet_new, and update the flooding time travel_time of the node Node_way1 to t ₀ , return to step 703, start Flood calculation of a new group until t ₀ -t _w is judged to be 0; Step 708: Store the road network connection number in the set Set_router into the initially defined set Set_arrived and remove duplicates, and the algorithm ends; The road network connection number in the set Set_router is the reachable road network list of vehicle A; Step 8: Assign tasks to vehicle A according to the reachable road network list obtained in the road network model, so as to realize precise transportation operations. 2. a kind of road network reachable range analysis method based on flooding algorithm as claimed in claim 1 is characterized in that, in described step 1, the traffic area range comprises: set given time as t, selected The maximum speed of the vehicle is v, then the determined traffic area range is a circle with the vehicle position as the center and vt as the radius. 3. a kind of road network reachable range analysis method based on flooding algorithm as claimed in claim 1 is characterized in that, the vehicle A information described in described step 2 comprises: height is height, width is width and The load is load, and each road in the road network set Set_way is retrieved from the database in turn. According to the height, width and load information of each road, they are compared with the height, width and load of the vehicle information respectively. The height, width and load of vehicle A will not be satisfied. Roads with width and load information are removed from the road network set Set_way. 4. a kind of road network reachable range analysis method based on flooding algorithm as claimed in claim 1, is characterized in that, in described step 6, the connection is specifically: for edge class Link_waym, according to the corresponding road number wgidm value , obtain the corresponding road information in the database; the road information includes the passing time, the end point number and the start point number; Assign the travel_time of the edge class Link_waym to the passing time of the corresponding road; According to the end point number obtained by the road number wgidm, find the road network node class Node_wayp corresponding to the end point number in the road network node class set Set<Node_way>, as the value of the node_target corresponding to the link class Link_waym; At the same time, according to the starting point number obtained by the road number wgidm, find the road network node class Node_wayq corresponding to the starting point number in the set Set<Node_way>, and add the edge class Link_waym to the set<Linked_way> corresponding to the road network node class Node_wayq. . 5. a kind of road network reachability analysis method based on flooding algorithm as claimed in claim 1, is characterized in that, in described step 706, the process of specifically adding the number of connected edges is: Determine whether the number of the added edge is 1. If so, add the corresponding edge number to the Set_router of the package Packet_new. Otherwise, when the number of edge numbers is greater than 1, according to each time t ₀ - The difference value of t _w , select the connection edge corresponding to the time with the largest difference value, and add the connection edge number to the set Set_router of the packet Packet_new.

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