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Auto Ownership Model For Southeast Florida Models Southeast Florida FSUTMS Users Group Meeting Ft. Lauderdale, FL. Why?. Life Style Gen Requires Number of HHs At each auto ownership level (0, 1, 2, 3+) For HH with and HH without children Current model input is: - PowerPoint PPT Presentation
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May 16, 2008May 16, 2008
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Auto Ownership ModelAuto Ownership Model For Southeast Florida ModelsFor Southeast Florida Models
Southeast Florida FSUTMS Users Group MeetingSoutheast Florida FSUTMS Users Group MeetingFt. Lauderdale, FLFt. Lauderdale, FL
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Why?Why?Life Style Gen Requires Number of HHs Life Style Gen Requires Number of HHs At each auto ownership level (0, 1, 2, 3+)At each auto ownership level (0, 1, 2, 3+) For HH with and HH without childrenFor HH with and HH without children
Current model input is:Current model input is: Vehicles in HH’s with childrenVehicles in HH’s with children Vehicles in HH’s without childrenVehicles in HH’s without children Disaggregated by a series of polynomialsDisaggregated by a series of polynomials
Lack of consistent and logical forecasting Lack of consistent and logical forecasting methodologymethodology Most models either grow vehicles in proportion to Most models either grow vehicles in proportion to
HH’s, orHH’s, or Perhaps adjust to meet county aggregate totalPerhaps adjust to meet county aggregate total
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Past WorkPast Work
For District 4 – Paper by Li, Ewing & Gross (late For District 4 – Paper by Li, Ewing & Gross (late 1990’s?).1990’s?).Other major urbanized areas throughout the US.Other major urbanized areas throughout the US.Encouraged by USDOTEncouraged by USDOTMost models use some combination of:Most models use some combination of: PersonsPersons WorkersWorkers DensityDensity ChildrenChildren Income – Almost all require this one ****Income – Almost all require this one **** AccessibilityAccessibility
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Since FSUTMS Doesn’t Use IncomeSince FSUTMS Doesn’t Use Incomeand Previous Work Required Incomeand Previous Work Required Income
UseUse Persons/HHPersons/HH Workers/HHWorkers/HH ChildrenChildren
WithWith
WithoutWithout Density (HH, Emp, Area)Density (HH, Emp, Area) Accessibility (Time & Trip Attractions)Accessibility (Time & Trip Attractions)
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Model FormModel Form
Multinomial LogitMultinomial Logit
SSxx = Exp(u = Exp(uxx)/[Exp(u)/[Exp(u00)+ Exp(u)+ Exp(u11)+ Exp(u)+ Exp(u22)+ Exp(u)+ Exp(u33)])]
WhereWhere
SSxx = = share of HH’s at each auto ownership level (0,1,2,3)share of HH’s at each auto ownership level (0,1,2,3)
uux x = utility for level x= utility for level x
== f(persons or workers/HH, density, accessibility)f(persons or workers/HH, density, accessibility)
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Density CalculationDensity Calculation
Density = (Households + Total Density = (Households + Total Employment)/(net area)Employment)/(net area)
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Accessibility CalculationAccessibility Calculation
InputsInputs Travel Time Skim Matrix (for GM)Travel Time Skim Matrix (for GM) Trip Attractions (from “trial” Gen run)Trip Attractions (from “trial” Gen run) Friction factorsFriction factors
For each TAZ:For each TAZ:
Accessibility=Accessibility=Sum of: FF(t)*Attractions for each purposeSum of: FF(t)*Attractions for each purpose
Over all destinationsOver all destinations
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Best ModelBest Model
Households without childrenHouseholds without children PersonsPersons DensityDensity AccessibilityAccessibility
Rho-squared: 0.342683 Rho-squared: 0.342683
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Best ModelBest Model
Households with childrenHouseholds with children WorkersWorkers DensityDensity AccessibilityAccessibility
Rho-squared: 0.288637 Rho-squared: 0.288637
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Other NotesOther NotesGross and Ewing found a rho-squared of 0.4704 for their Gross and Ewing found a rho-squared of 0.4704 for their model 4. model 4. For the 0, 1, 2+ models, comparable to Gross and Ewing, our For the 0, 1, 2+ models, comparable to Gross and Ewing, our models have rho-squared of 0.39 and 0.50 for without and with models have rho-squared of 0.39 and 0.50 for without and with children respectively. These models are at least as well as children respectively. These models are at least as well as Gross and Ewing. Gross and Ewing. For the 0, 1, 2, and 3+ models, the proposed models have rho-For the 0, 1, 2, and 3+ models, the proposed models have rho-squared of 0.34 and 0.29 for without and with children squared of 0.34 and 0.29 for without and with children respectively. These are still good models, but as expected, the respectively. These are still good models, but as expected, the task is more difficult when trying to estimate 4 levels. task is more difficult when trying to estimate 4 levels. The signs in all models are correct, and all variables included The signs in all models are correct, and all variables included in the equations are significant at the 0.05 level and beyond in the equations are significant at the 0.05 level and beyond for most variables.for most variables.
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Remaining WorkRemaining Work
County Biases will be testedCounty Biases will be tested
Life-Style Gen will have to be modified to Life-Style Gen will have to be modified to use the new modeluse the new model
Actual model implemented in MatrixActual model implemented in Matrix
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Questions?Questions?
