Travel Demand Forecasting: Parameters and Techniques (2012) / Chapter Skim
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Pages 80-88
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From page 80... ...
("Validation and Sensitivity Considerations for Statewide Models") • Validation is "forecasting" current travel patterns to demonstrate sufficient ability to reproduce highway counts and transit line volumes.
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From page 81... ...
Variability and error occur in the input data used to estimate and apply travel models, in estimated or specified model parameters, and in the data used to validate the models. 5.2.3 Uses of Data in This Report for Validation and Reasonableness Checking If the data and parameters included in Chapter 4 of this report are used to specify or enhance travel models for an area, the specification and collection of independent validation data such as traffic counts, transit boardings, travel time studies, and special generator cordon counts (see Chapter 3)
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Modeled home-based work trip production rates for example urban area. Income Group Household Size Average1 2 3 4 5+ Low (Less than $25,000)
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Comparison of example region to NHTS trip production rates by household size. Trip Purpose and Data Source Income Range Less than $10,000 $10,000– $24,999 $25,000– $49,999 $50,000– $99,999 $100,000 or More Home-Based Work Hypothetical Region 0.8 1.9 2.2 NHTS 0.6 0.8 1.3 1.9 2.0 Home-Based Nonwork Hypothetical Region 2.2 4.9 6.2 NHTS 4.1 4.7 5.0 6.2 7.6 Nonhome based Hypothetical Region 1.1 2.8 4.4 NHTS 1.6 1.9 2.7 3.8 4.7 Total Hypothetical Region 4.1 9.6 12.8 NHTS 6.3 7.4 9.0 11.9 14.3 Source: 2009 NHTS.
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From page 84... ...
For the home-based nonwork trip purpose, the trip rates by household size for the example urban area are all lower than the NHTS trip rates. For the nonhome-based trip purpose and for all trip purposes combined, the results were mixed with example urban area rates being higher than NHTS rates for the lowest two household sizes and lower for the top three household sizes.
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However, some caution might be warranted if the example region was medium sized. The example function is generally steeper at low travel times and produces friction factors that are lower than the other medium-sized region friction factors over most of the range of travel times.
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From page 86... ...
. In addition, staff from the MPO and their families were asked to record travel times on their trips to and from work.
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Table 5.10 shows the trips per household resulting from the applications of the original model based on NCHRP Report 365 rates along with results from the application of the model summarized in Table 5.9 using the MPO's socioeconomic distributions of households by household size. Table 5.10 also shows the average trip rates for MPOs from Tables C.5 through C.7.
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From page 88... ...
Based on the information provided by the reasonableness checks for the trip production and trip distribution models and the model validation results, both the trip production and trip distribution models were deemed to produce reasonable results. 5.5 Cautions Regarding Use of This Report for Validation The examples shown in this chapter illustrate both the risk and value of using information contained in this report for model validation and reasonableness checking.
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