Activity-Based Travel Demand Models: A Primer (2014) / Chapter Skim
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51.1 WHY DO WE MODEL TRAVEL? Transportation decision makers confront diffi cult questions and must make informed choices.
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6Part 1: ACTIVITY-BASED TRAVEL DEMAND MODELS: A PRIMER where order-of-magnitude information is all that is required. These models are typically simple and easy to implement, require less data, and often are implemented using common desktop software tools such as spreadsheets and geographic information systems (GISs)
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7Chapter 1: MOVING TO ACTIVITY-BASED TRAVEL DEMAND MODELS for an individual person as well as across multiple persons in a household. These linkages enable them to more realistically represent the effect of travel conditions on activity and travel choices.
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8Part 1: ACTIVITY-BASED TRAVEL DEMAND MODELS: A PRIMER and activity-based models generally have longer run times and greater development, application, and maintenance times and costs. 1.5 ACTIVITY-BASED TRAVEL MODELS 1.5.1 Activity-Based Travel Model Definition A fundamental premise of activity-based travel models is that travel demand derives from people's needs and desires to participate in activities.
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9Chapter 1: MOVING TO ACTIVITY-BASED TRAVEL DEMAND MODELS 1.5.2.2 Aggregation Bias Aggregation bias refers to the assumption that group characteristics are shared by all the individuals who are members of that group. Tripbased models use aggregations of households that share the same attribute values to make forecasts, the idea being that all households of the same type behave similarly.
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10 Part 1: ACTIVITY-BASED TRAVEL DEMAND MODELS: A PRIMER One of the primary means through which consistency is achieved is through the representation of tours and trips. Activity-based models treat the tours and trips made by an individual as interrelated across the entire day.
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11 Chapter 1: MOVING TO ACTIVITY-BASED TRAVEL DEMAND MODELS 1.5.3.3 Detailed Information Activity-based models incorporate significantly more detailed input information and produce significantly more detailed outputs than tripbased models. By operating at the level of individual persons and households, activity-based models can use a wider range of important explanatory variables to predict travel patterns than trip-based models.
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12 Part 1: ACTIVITY-BASED TRAVEL DEMAND MODELS: A PRIMER detailed outputs also allow insights into how changes such as the vehicle miles traveled or emissions can be attributed to individual households. It is even possible for traveler benefits to be attributed to clusters of employment, which can be important for economic development analyses.
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13 Chapter 1: MOVING TO ACTIVITY-BASED TRAVEL DEMAND MODELS based model. The primary data used to develop and apply both activity-based and trip-based models include household travel survey information, economic and demographic information about the spatial distribution of employment and households, and representations of transportation networks.
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14 Part 1: ACTIVITY-BASED TRAVEL DEMAND MODELS: A PRIMER activity-based model software is typically designed to employ distributed computing across multiple processors. 1.5.4.4 Model Run Times Activity-based model system run times are dependent primarily on the size of the population of the region being simulated, the number of zones and time periods for which the network supply models are run, and the amount of computing resources available.
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15 Chapter 1: MOVING TO ACTIVITY-BASED TRAVEL DEMAND MODELS • Land use models typically provide more detailed information about subregional land use development and redevelopment, the economy, employment, and population. There is a broad spectrum of approaches to modeling land use and the land use– transportation interaction, and the outputs from these models may be aggregated, disaggregated, and transformed in order to provide direct inputs to an activity-based model.
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16 Part 1: ACTIVITY-BASED TRAVEL DEMAND MODELS: A PRIMER individual parcels and has applied the model to a variety of innovative analyses. For example, to analyze the impacts of a large-scale residential development that was designed to produce more pedes trian, transit, and other short- distance trips, the activity-based model was used to compare the travel behavior of tens of thousands of residents in two different scenarios: one in which these residents lived in the proposed development and an alternative in which these exact same residents lived in more typical suburban developments.
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