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The travel forecasting process is at the heart of urban transportation planning. Travel forecasting models are used to project future traffic and are the basis for the determination of the need for new road capacity, transit service changes and changes in land use policies and patterns. Travel demand modeling involves a series of mathematical models that attempt to simulate human behavior while traveling. The models are done in a sequence of steps that answer a series of questions about traveler decisions. Attempts are made to simulate all choices that travelers make in response to a given system of highways, transit and policies. The travel simulation process follows trips as they begin at a trip generation zone, move through a network of links and nodes and end at a trip attracting zone. The simulation process is known as the four step process for the four basic models used. These are: trip generation, trip distribution, modal split and traffic assignments. The traditional four step transportation modeling system is elaborately discussed in this scientific research paper and the whole calculation process is described step by step for better understanding.

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Bayes Ahmed: M.Sc. in Geospatial Technologies (Erasmus Mundus Scholar), Bachelor of Urban and Regional Planning from Bangladesh University of Engineering and Technology. Interests: Geographic Information System; Remote Sensing; Urban, Transportation and Environmental Planning and Management. I dream of a World free from Poverty, Racism and War.

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