openflow conflict detection06338624

1、2012 15th International IEEE Conference on Intelligent Transportation Systems Anchorage, Alaska, USA, September 16-19, 2012Advanced method of detection of unnecessary conflicts of traffic flowsIvan Dadic, Damir karo, Kresimir Vidovic, Marko Sevrovic, Marko Sostaric, Dragana Jeremic978-1-4673-3063-3/

2、12/$31.00 2012 IEEE178Relations between the traffic flows in intersections are one of the causes of reduced throughput. Avoiding the unnecessary conflicts and reduction of breakage of traffic flows are one of the possible significant factors that may favorably affect the increase in intersection cap

3、acity. Relationships among the traffic flows in the form of unnecessary conflicts occur mainly at intersections, and also on roads between intersections, and are caused by the organization and direction of traffic flow in the network. For advanced identification of unnecessary intersections, modern

4、IT solutions are used as a novelty approach in research and visualisation of this phenomenon. The goal of this research is to create a computer tool based on open source technologies that use data stored in a GIS environment about the movement of the users within the transport network for identifica

5、tion of unnecessary conflicts by monitoring the flow of vehicles and deviations in speed. Further development and research will be focused on creating algorithms for automatic identification of unnecessary conflicts based on gathered input data.I. INTRODUCTIONThe phenomenon of unnecessary conflicts

6、is relatively new phenomenon identified in traffic flows theory. This phenomenon was not recognized in the mutual connection between sources and destinations in the urban environment, where very different causes may affect the selection of itinerary of each driver, or in the wider sense anyone invol

7、ved in transport system. Due to the nature of a road traffic and the massive scale of individual transportation reduction of unnecessary conflicts of traffic flow is particularly important in the city center. The reduction of unnecessary conflicts among the traffic flows and the methods which are su

8、itable, with a goal of creating a selection of few real and applicable solutions of traffic flow organization within the network is manifested especially at the intersections.Theoretical background of this theory may be applied on the real network by using the IT systems which are based on real data

9、 collected from road network and being presented toIvan Dadic, Ph.D., Faculty of Traffic and Transportation Engineering, Zagreb, Croatia (dadicifpz.hr)Damir karo, Ph.D, AK “Siget”, Zagreb, CroatiaKresimir Vidovic, B.Sc. Faculty of Traffic and Transportation Engineering, Zagreb, Croatia (vidovickfpz.

10、hr)Marko Sevrovic, M.Sc., Faculty of Traffic and Transportation Engineering, Zagreb, Croatia (marko.sevrovicfpz.hr)Marko Sostaric, M.Sc., Faculty of Traffic and Transportation Engineering, Zagreb, Croatia (marko.sostaricfpz.hr)the researches in the visualized way by using the appropriate GIS solutio

11、n. Precision of such systems in combination with data mining in the appropriate IT environment creates the ability to display the load of traffic flows with the speed of the vehicle on the map, creating a base for further research. At this stage of research, a visual method is used to determine the

12、possible locations where the unnecessary conflicts phenomenon appears, and the implementation of tools and methods proposed in this paper can make a plan of reorganization or traffic flows regulation. A further phase of research is focused on creating algorithms in a GIS environment that will enable

13、 automatic identification of unnecessary conflicts and suggestionsfor their solution.II. UNNECESSARY CONFLICTS OF TRAFFIC FLOWSUnnecessary conflict of traffic flows is a conflict between traffic flows which are not needed and can be avoided. For example, if there are two zones, or two points between

14、 which a by directional traffic is running, and then the traffic flows between these two zones should not intersect with each other. In practice, however, for various reasons vehicle trajectories between these two zones do intersect. This phenomenon can be noticed and proved if, for instance, driver

15、, while driving from zone “I” in zone “J” imagines that he is in parallel driving from zone “J” to zone “I” and intersects with his own trajectory. If from the zone “I” originates 100 vehicles in one hour with destination in zone “j” and vice versa, this leads to unnecessary conflicts of 200 vehicle

16、s more. If there are now other vehicles besides these two flows at that intersection, the unnecessary conflict of traffic flows wouldoccur.Unnecessary conflict of traffic flows can occur at one or more conflict points, and usually the number of points is two. Unnecessary conflict which occurs in one

17、 point is very rare in real transport environment. For the phenomenon of unnecessary conflicts between traffic flows to occur, it is necessary to have a unnecessary conflict in at least one point. Unnecessary conflict is consequence, in wider scope, of deviation of driving on the right or left side

18、of the road which depends on traffic regulations in dedicated country or state.Until now, the unnecessary conflict of traffic flows was considered as a phenomenon when the traffic is running between two different zones. This phenomenon of unnecessary conflict can be identified easily if by realizati

19、on of one drive towards a defined goal a trajectories of the vehicle intersects with its own trajectories in return. This is the main indication that this is not an isolated case and thatthe other drivers within the same network perform the same actions, and there are indicators that that the organi

20、zation of traffic flows is forcing the drivers to do so. In dependence with the number of vehicles in unit of time, which are intersecting in one point, the amount of conflicts will be bigger or smaller. If the further analysis about traffic flow directions is performed, it is possible to easily ide

21、ntify that unnecessary conflicts occur and between two pair of zones. This unnecessary conflicts can be identified and by the driver himself by analyzing its own return trajectories.By using several methods, it is possible to find a solution for avoidance of phenomena of unnecessary conflicts among

22、the two pairs of traffic flows. Unnecessary conflicts are quite common in traffic networks. Figure 1 shows the example of unnecessary conflict of traffic flows between zones (1) and(2) and zones (3) and (4). In this example, unnecessary conflict occurs at two intersections and at four critical point

23、s per intersections which sums to in total of eight critical points.Figure 1: Unnecessary conflicts of traffic flow at tointersectionsRegulatory influence on reducing the unnecessary conflicts of traffic flows is very important. Orientation of street network, and proper directions of one-way streets

24、 have a particularly great importance in decreasing the phenomenon of unnecessary conflicts of traffic flows. For instance, it is clear that in the two-way street, no one will drive on the left side. But, in the case of wrong orientation of the pair of one- way streets the phenomenon will occur, as

25、well as in the possible path selection process in two-way parallel streets.If the driving on the right side in regard on the point between two traffic flow is identified as a positive momentum, then the driving on the left side is negative flow. This method is very useful for basic understanding of

26、unnecessary conflicts of traffic flows phenomenon.A detailed analysis of available real variants based on the minimum of unnecessary conflicts among traffic flows may, in accordance with established goals, choose the optimum regulations within the network.Although the avoidance of unnecessary confli

27、cts is present throughout the entire process, it is the most prominent part in finding solutions for the organization of traffic flows and their evaluation. Knowledge about the described phenomenon is particularly important because it enables the experts to eliminate a number of solutions for organi

28、zing the traffic network and living a few possible iterations which are the tested against other methods to define the optimum one.I. SYSTEM FUNCTIONALITIES AND ARCHITECTURE OVERVIEWThe accurate estimations of road traffic status is a major issue to be resolved in successful ITS development. The sys

29、tem consists of a mobile phone equipped with appropriate software support, and GPS device. Using the software solution at any modern spartphone with either Android or similar operating system, data about movement of the vehicle within the network may be utilised and stored in database for additional

30、 research. Collected data from a mobile phone can be sent directly to a database using the GPRS system for data transmission, but it can also be stored and the memory card inside the device and later manually be entered in the database. The collected data is stored in log files containing informatio

31、n received via a GPS device about the location of the device. Using the appropriate conversion tools log files are transferred in shape format.SYSTEM ARHITECTURETRAFFIC FLOW CONDITION WEB SERVICEDATA PRESENTATION/XML /JavaSCRIPT / PHP / APACHE / HTMLDATA INTEGRATION AND ANALYSISqGIS, TimeMapDATA STO

32、RAGEPostgreSQL / PostGIS / CSV/ ESRI SHAPEFigure 1 System architecture overviewA shapefile is a digital vector storage format for storing geometric location and associated attribute information. This format lacks the capacity to store topological information. The shapefile format was introduced with

33、 ArcView GIS version 2 in the beginning of the 1990s. It is now possible to read and write shapefiles using a variety of free and non-free programs. Shapefiles are simple because they store primitive geometrical data types of points, lines, and polygons. These primitives are of limited use without a

34、ny attributes to specify what they represent. Therefore, a table of records will store properties/attributes for each primitive shape in the shapefile. Shapes (points/lines/polygons) together with data attributes can create infinitely many representations about geographical data. Representation prov

35、ides the ability for powerful and accurate computations.Shape file is being imported into QGIS open source GIS solution and is presented as an data layer. That data layer contains information about every vehicle trajectory divided181into points. Each point represents the data which was collected in

36、1 second interval. Data in QGis application is suitable for spatial analysis and by applying adequate filters at digital cadastre the road segments of network are defined.The data is available locally for desktop users and can be operated trough the desktop applications, and for a purpose of a backg

37、round layer of the online application data must be saved in adequate form. For that purpose spatial database is formed by using PostgreSQL database with PostGIS spatial extension. Time Map interactive solution is used as java oriented application for creating interface for web users which enables cr

38、eation of presentation layer which can be used for various purposes.System architecture consists of three layers. Data storage layer is used for data storage, which includes the raw data gathered from sensors, as well as for data which is storedRoad Traffic Data Database Static dataRoad infrastructu

39、re DataIDLatitudeLongitudeSpeedRoad segmentGPS info.CELL IDTA. . . .Dynamic dataTraffic flow dataIncident and maintainance dataafter being processed. Data integration and analysis layer uses data from data storage layer and is prepared as input for algorithms for road segment calculation. That data

40、is then presented at web service in third layer.II. DATABASE AND DATA VISUALISATIONThe application for database access and updating was initially to be bound to QGIS. Quantum GIS. Quantum GIS is an application for storage, editing and displaying od any geospatial data. Geospatial information databas

41、e which stores Road Traffic Data must consist of two logical sections. First section is reserved for static data and stores information about road infrastructure and objects, which represents the constant value. Static data is used to visualise road network map as a separate presentation layer and i

42、s located bellow the layer with the traffic data. Second section of the database is reserved for Dynamic data about traffic flow characteristics, which is updated in real time by informations gathered by sensors (most used sensor is GNSS device) which are located and cruising within the traffic netw

43、ork. Second table consists of “temporary” informations about incident situation like traffic accident or road maintenance which are valid for a limited period of time. Data visualization is a process of transforming information into a visual form. Visualisation method depends on specific task, so it

44、 is important to choose most adequate methods for traffic data visualisation. As Traffic data contains spatial information it follows that presentation of Traffic data on digital map of traffic network is most appropriate method for presenting traffic data, which is subject to reviewing, analysis, p

45、rocessing, and decision- making. Data visualization is important tool in data mining, it enables user to recognize trends and data relationship in large data sets characteristic for Road Traffic data.Figure 2 Road information database structureDuring the research selected methods were implemented on

46、 Road traffic data set on real traffic network. Geodatabase containing both data about road infrastructure and up to date and real time Road traffic data was formed. The final result is layer with road traffic data which is available via web service. Figure 4 shows major city networks in the City of

47、 Zagreb which were chosen for this pilot project. Different colors of road segments at the chosen coverage area represented the different road segments. This segments in future program iterations are suitable for determining traffic flow characteristics using either GPS or mobile network data gather

48、ed from mobile phones. Image 6 shows the example of raw data which is imported as a layer above the digital cadastre, or digital city map.Figure 4. Geo processed data in GIS application with example of unnecessary conflicts in real traffic networkFigure 5. Road segment definition based on GPS dataAs

49、 final result of road visualisation a online application was created which uses data from online database for presenting the road networks segments. Since this is an online application associated to PostGIS database data from sensors after processing is automatically updated on the digital map. This

50、 kind of service in future iterations of project will be used as a background layer for different kind of user oriented applications, especially for identification of unnecessary conflicts of traffic flows within the road network, an to measure and track performance of the read network after the pro

51、posed solution is integrated within the network.III. CONCLUSIONUnnecessary conflict of traffic flows is a conflict between traffic flows which are not needed and can be avoided. Avoiding the unnecessary conflicts and reduction of breakage of traffic flows are one of the possible significant factors

52、that may favorably affect the increase in intersection capacity, as well as other aspects like traffic safety, ecological and economical factors. For advanced identification of unnecessary intersections, modern IT solutions are used as a novelty approach in research and visualisation of this phenome

53、non. The goal of this research is to create a computer model based on open source technologies that use data stored in a GIS environment about the movement of the users within the transport network for identification of unnecessary conflicts by monitoring the flow of vehicles and deviations in speed. Further development and research will be focused on creating algorithms for automatic identification of unnecessary conflicts based on gathered input data as w