Abstract
A large variety of transport planning and management task requires the knowledge of the pattern of trip flows. Travel Demand or Origin-Destination (OD) matrix is estimated by conventional techniques such as home interviews, roadside interviews, flagging techniques etc. and also by modeling of the network. To supplant the costly and time consuming conventional techniques, significant progress has been made in recent years on estimation of OD matrix from link volumes. A number of techniques have been developed and each of its applicability and practicability varies from one another.

There has been, however, very limited attention that has been devoted to the key problem of identifying a set of links for which flow information should be collected and used. The modern transportation planning software packages available in the market at present has the facility of estimating the OD but the identification of the link/movements according to their importance has not been incorporated. Even if the software has the capability of the carrying out the travel demand estimation, none has the GIS interface.

GIS interface can be very helpful in labeling and identifying the attributes in the network. As computation time becomes shorter and the demand on professional time becomes greater, the need for an innovative way to use computers to automate time – consuming processes becomes more apparent. In this study the estimation of OD matrix is done and other features such as Link selection procedure and Optimal Survey locations in the network are dealt with.

Full-fledged user-friendly software, TRADES, with GIS integrity, is developed in this study. This software is developed for estimating the Origin Destination matrix with Graphic User Interface, with additional features such as Link selection procedure and optimal survey station locations, to make the estimation process less tedious and interactive. TRADES is a state-of-the-art system for planning transportation facilities on multi-modal networks with GIS interface. It offers the planner a comprehensive and flexible set of tools for demand modeling and analysis, as well as network analysis and evaluation.

With TRADES it is possible to,

• View all network attributes using either a table view or a network plot. The attributes include nodes, links, zones etc.
• Zooming of the windows for easy viewing of the network attributes is possible.
• Save views as bitmap images using standard Windows controls
• Add, edit or delete centroids, nodes, links, transit lines and segments editing the database any time
• Add, edit or delete any matrix through the database used as the backend while program is running
• View the labels for nodes, links and centroids. It contains the information such as the number, the coordinates and for links it contains the speed, distance and volume of the particular link.
• Estimation of Origin – Destination matrix with Entropy Maximisation method
• View 2D charts for the iteration number and the error value for the travel demand estimation procedure
• Analysis for finding the important link in a set of links
• Viewing links numbered as per their order in the calculated link list
• Exporting the table to Excel spreadsheet using a template or directly to any spreadsheet
• Calculation for locating the optimal survey locations with user input error limit
• Viewing the survey locations on the network
• Copy (export) the network with details plotted to an external compact file and recall (import) the data when required
• Viewing Production / Attraction ratio for each zones
• Create desire line maps for the estimated OD matrix as well as available OD matrix

TRADES was validated with available hypothetical networks. It was checked with the results of earlier studies carried out by various researches. The network contained 6 zone centroids and 18 one way link. The trial was carried out and was found satisfactory with very little error.

This software was also applied to the real life situation. Mumbai City, capital of Maharastra and also the financial capital of India was taken as the study area. As per latest census (2001), Mumbai’s population is 119 lakhs, which is about 20 lakhs more than the previous census of 1991. Each square km of the land in Mumbai supports over 20200 people, which translates about 550 sq ft of land per person. The density of population in Mumbai is over 62 times the average of India. The study are consists of 24 zones. There are 69 nodes and 196 links in the network. There are inter-zonal trips found between the zones. Four zones are considered as external zones for the study.

The database for the software is created in Microsoft Access 2000 (9.0). The tables of the database include Node, Links, Zones, Zone connectors, Boundary, Actual OD matrix, Interchanges and Seed OD matrix. The network was plotted using the tools available in TRADES. To check the accuracy of TRADES, the network was plotted in universally accepted software, TRIPS. The network was found the same as the network which was plotted using TRADES.

The origin destination matrix was estimated using the sub-menus in TRADES. The Analysis menu in TRADES when clicked, gives the user to change the default values. The OD matrix comes in a new window. The matrix for a particular iteration number can be viewed using the Display menu. Plot between iteration number and error value can be viewed using the sub-menus.

As all the links in the network will not contain the same amount of information, it is very essential to find the links which contribute maximum to the travel demand matrix. Link selection procedure is based on the method suggested by Samson Mathew (1996).

TRADES, from a list of 196 links, selected the links which can provide maximum information for obtaining the travel demand matrix. It is possible to view important links in the network plot window.

It is tiresome to carry out surveys in all the links to get the volume counts for travel demand estimation. So it is necessary to find the location of optimal survey stations in the network. TRADES gives the list of links which should have survey locations. TRADES is capable of displaying the locations of the optimal survey stations in the network plot window.

TRADES quickly and efficiently displays large amounts of data in a form that allows for easy debugging by the user. With analysis tool such as OD Estimation, Link Selection and Optimal Survey locations, the user can obtain outputs in the form of charts and tables. This helps the user to locate useful information about the network from the interface. As the computation time is becoming shorter and the demands on professional time increases, the package proves to be competitive. Without in-depth knowledge of the software, network modeling can be done very easily. As the data formatting is done by the package itself, many computational errors are also eliminated.