BAGHDAD COMPREHENSIVE TRANSPORTATION STUDY MODEL CALIBRATION AND MODAL SPLIT

One of the main aims of this study was to develop a computerised transportation model capable of simulating travel within the study area. This model was used to synthesise the travel demands and patterns in future years and evaluate alternative transportation strategies which might cope with this demand. The modelling work was based on the data collected in the traffic surveys described earlier. The main transportation model was the city model which takes account of the fact that some trips may be captive to one mode of travel thus reducing the number of trips which have a true choice of mode. In the trip generation phase of the model the household categories chosen covered five different variables including household density. This variable was only included when it became apparent that the other four variables could not satisfactorily reproduce the observed number of trips in several areas of the city. In the base year situation in Baghdad there were five separately identifiable modes of transport that each carried more than 10% of the weekday passenger movements. The calculation of the modal split functions included only those trips which were surveyed as having a true choice of mode. The limited number of such choice trips in Baghdad made the process of modal split calibration even more difficult. The final test applied in each case was to assign the synthesised matrices to the appropriate network and compare the flows with the observed counts. As expected there were some differences at particular points but overall the results were in sufficiently close agreement to be within acceptable confidence limits. (Author/TRRL)