Travel demand


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Unformatted text preview: I/ TEN BASIC ELEMENTS OF A 3C PLANNING PROCESS These steps had been pioneered by the urban transportation planning studies that were carried out during the 1950s. It was an empirical approach that required a substantial amount of data and several years to complete. The process consisted of establishing an organization to carry out the planning process, development of local goals and objectives, surveys and inventories of existing conditions and facilities, analyses of current conditions and calibration of forecasting techniques, forecasting of future activity and travel, evaluation of alternative transportation networks resulting in a recommended transportation plan, staging of the transportation plan, and identification of resources to implement it. The product of these 3C planning studies was generally an elaborate report describing the procedures, analyses, alternatives and recommended plans. II/ TRAVEL DEMAND FORECASTS Travel Demand Forecasting is a key component of the transportation engineers technical repertoire. It allows the engineer to predict the volume of traffic that will use a given transportation element in the future, whether that element is an existing highway or a potential light-rail route. The model set is based on the traditional four-step urban transportation planning process of trip generation, trip distribution, mode choice, and trip assignment. This process is used to estimate the daily transit ridership and highway traffic volumes, based on changes to the transportation system. The Four-Step Model 1. Trip Generation: In the first step, the total number of trips produced by the residents in the model area is calculated using demographic and socio-economic data. Similarly, the numbers of trips attracted by different types of land use such as employment centers, schools, hospitals, shopping centers etc., are estimated using land use data and trip generation rates obtained from travel surveys . 2. Trip Distribution: In the second step, the model determines how the trips produced and attracted would be matched throughout the region. Trips are distributed based on transit and highway travel times between TAZ and the relative attractiveness of each TAZ. The attractiveness of a TAZ is influenced by the number and type of jobs available, the size of schools, hospitals, shopping centers etc. 3. Mode choice: Once the total number of trips between all combinations of TAZs is determined, the mode choice step of the model splits the total trips among the available modes of travel. The modes of travel are walk, auto and transit. To determine what proportions of trips each mode receives, the model takes into account the travel times,...
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