OD Matrices Research Articles

Analysing Rail Freight Transportation InTurkey: A GIS Application

It is important to constitute a detailed, easily understandable, and visually appealing database related to rail freight transportation for carrying out various analyses, making more effective operational plans, and finding solutions for many management problems. Hence, in this paper, the rail freight transportation in Turkey is analysed, giving a special emphasis on Geographic Information Systems (GIS). In order to carry out the study, at first, the origin and destination (O-D) matrices for 20 different kinds of commodities carried by the Turkish State Railways (TCDD) in the year 2000 were determined by using the statistical data provided by TCDD. Afterwards, the railway network was coded, and the OD matrices obtained for these 20 different commodities were assigned onto this network based on an all-or-nothing assignment. Consequently, the commodity flows on the railway links resulting from assigning these matrices onto the railway network were found. Finally, these matrices and the commodity flows on the railway links were transferred into the GIS environment to enable the full range capability needed in this research. In other words, GIS were adopted for capture, storage, manipulation, and analysis of information related to the O-D matrices for different commodities transported by rail and commodity flows on railway links resulting from assigning these matrices onto the railway network. Consequently, this study places identification of the O-D matrices for various commodity types carried by rail and the commodity flows on railway links in a broader perspective by using GIS.

THE DEVELOPMENT OF THE REAL TIME INTEGRATED TRAFFIC INFORMATION SYSTEM (RITIS) FOR INDONESIA

The paper is written based on research on ‘Dynamic Origin-Destination Matrices From Real Time Traffic Count Information’ completed in March 2001. The latest development in automatic traffic count data collection enables us to obtain the traffic count information in real time or short-time-interval basis. For example, ATCS ( A rea T raffic C ontrol S ystem) already installed in several large cities in Indonesia, such as: DKI-Jakarta (1994), Bandung (1997), and Surabaya (1998) provided us the short-time-interval traffic count information for all signalised intersections. This traffic data is updated periodically in a short-time-interval basis (e.g., 5, 15, or 30 minute time interval). This information is provided at the T raffic C ontrol C entre (TCC) of ATCS project and can be directly and easily accessed at a very low cost through the Internet or a telephone line. This data is the main input for the short-time-interval OD matrix estimation. Before this traffic data is used in the OD matrix estimation process; firstly, these data have to be processed in the D ata P rocessing I nterface (DPI). Having it processed; the traffic data will then be ready for estimating the short-time-interval OD matrices. The output of short-time-interval OD matrices together with several practical applications will be the main input for the R eal T ime I ntegrated T raffic I nformation S ystem (RITIS). This information will be stored in a Website designed specifically and informatively for the purposes of user needs (numerical and graphical). This short-time-interval traffic system information will become the public-domain information which can be directly and freely accessed through the Internet by the users (e.g., planning authorities, traffic authorities, Department of Public Works, consultants, police, drivers, radio stations, and TV stations, and other related agencies, etc.). One of the most important information is the best routes from each origin zone to each destination zone which have already considered the effect of congestion. This information will be the main data for the development of the R oute G uidance S ystem (RGS) so that each driver can choose his best route through the road network. The best route information will be changed in a short-time-interval basis depending on the traffic condition. Moreover, this approach can also be extended to provide the short-time-interval environmental information. The system has been tested and validated in Bandung and it showed remarkably good results for Bandung condition.

On-line Estimation of OD Flows from Input/Output Counts

The dynamic procedure for the estimation of OD matrices within a junction, a freeway corridor and a subarea of urban network from time series counts of traffic flows on the entrances and exits are proposed. This paper presents two methods for identification of split parameters. One, which is appropriate for individual intersections, is formulated based on the assumptions that the travel time for each OD pair is identical and equivalent to a fixed value. The other, which is suitable for freeway networks. makes no specific assumptions about the travel time. The dynamic relations between time-varying OD flows and traffic counts are established through proposed methods.

Dynamic Estimators of Origin-Destination Matrices Using Traffic Counts

This paper proposes different “dynamic” estimators using time-varying traffic counts to obtain (discrete) time-varying OD flows or average OD flows. All the estimators can combine counts with other available information, e.g., out-dated matrices and surveys, on a general network and can be formulated as optimization problems. In the case of time-varying OD flows, two types of estimators are proposed. Simultaneous estimators produce joint estimates of the whole set of OD matrices, one for each time slice, whereas sequential estimators produce a sequence of OD estimates for successive time slices. A particular type of simultaneous and sequential estimator (namely Generalized Least Squares) was tested on the Italian Brescia–Padua motorway for which “true” OD flows over a whole day were available. Results were generally satisfactory, showing that also in the “no a priori information” case significant estimates could be obtained.

XNET: Extended Traffic Assignment Model

A PC-based traffic planning model for use by small cities is described. The software includes routines for estimating OD matrices from observed link data and for determining equilibrium traffic flows. The mathematical modeling and algorithmic implementation of the problem and its solution technique are emphasized. An example application of the model is included.