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3.2 Non-Graphic Data
The non-graphic data consisted the details of traffic zones and the road network. The non-graphic database was created using the inbuilt data base utilities. The database of traffic zones, which are the electoral wards of Calicut city, consisted of the population, number of employees, area, and road length per sq.km. of area. The non-graphic data of the road network consisted of the information like link number, starting node number, ending node number, length and volume for each link. These data were stored in separate data tables in the database that do not have any relation with the graphic objects until the connection is established.

3.3 Linking Database
It means that after the database is created with all the details regarding the graphic objects, a connection should be established between the database and the graphic file. There is one option in MAP called Link Path Name (LPN) to establish the relation between the database and graphic file. The link path name consists of the name and location of database file and establishes the connections as and when the graphic data file is opened. The next step in linking database is to establish the connections between the objects in graphic data file and the information contained in database. This is done by selecting a record in the data sheet and attaching it to the corresponding graphic object.

3.4 Minimum Path Tracing
Minimum paths between zones based on selected criteria are required for estimation of travel demand and obtaining the link volumes. The MAP software does not have any utilities to trace the minimum path along the links of the road network. A program was written in 'C' based on Moore's algorithm was used to obtain the minimum paths between the zones based on distance as the criteria.

3.5 Traffic Volumes on Selected Links
Another input required for estimation of travel demand through indirect approaches is traffic volumes on selected links. Traffic volumes on 23 selected links were obtained by manual methods.

4.0 Estimation of O-D Matrix
The knowledge about the travel pattern between various zones in study area is required for transportation planning and management activities. This information about the travel pattern between every origin-destination pair in an area is organized in the form of a matrix called trip matrix or Origin-Destination Matrix. Estimation of O-D matrices is one of the major issues transportation planning process. The O-D matrix can be estimated using techniques such as home interview survey, roadside interview survey, work place interview, etc. But, conduct of surveys involves large amounts of resources and thus these methods are expensive and time consuming. To overcome these difficulties, O-D estimation through simple link volume modeling philosophy has been adopted.

The model proposed by Vanzyulen and Willumsen (1980)based information minimization approach was used for estimation of O-D matrix from link volume information. The estimated O-D matrix was assigned was assigned on to the existing road network using all or nothing assignment technique.

5.0 Preparation of Desire Line Diagram
In desire line diagram the travel between various pairs of zones is represented by bands, whose width is proportional to the travel, drawn between the centroids of the zones. The desire line diagram is very useful in understanding the travel pattern in a study area and carrying out the capacity sufficiency or deficiency studies of the road network. Desire line diagram has got important application in this study. The MAP does not have any tools for preparation of desire line diagram. A macro 'desire' was written in AutoLISP to prepare the desire line diagram taking the travel information from the data file and graphic details of the zones from the graphic data file of the traffic zones. A desire line diagram prepared using the macro 'desire' is shown in Fig. 3.

6.0 Identification of Missing Links
The road links that are required to carry the traffic between two places but missing in the existing road network are called missing links. Because of the missing connections between places the traffic takes a circuitous route resulting in heavy congestion on the few available links. By providing new roads along the desired direction of travel or between places of major traffic generators the traffic situation can be improved to a great extent. For identifying the missing connections between zonal pairs the prepared desire line diagram was superimposed over the existing road network. The superimposed maps were observed closely along the major O-D pairs and were checked whether direct links between those O-D pairs are available or not. If a direct connection is not available, it means that by adding one or more new links a direct connection can be established resulting in considerable reduction in travel distance between zones. The desire line diagram superimposed over the minimum path diagram was carefully observed and a few sets of missing links were identified, which are shown in Fig. 4.