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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:

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  1. Auto Ownership ModelFor Southeast Florida ModelsSoutheast Florida FSUTMS Users Group MeetingFt. Lauderdale, FL Corradino

  2. 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: • Vehicles in HH’s with children • Vehicles in HH’s without children • Disaggregated by a series of polynomials • Lack of consistent and logical forecasting methodology • Most models either grow vehicles in proportion to HH’s, or • Perhaps adjust to meet county aggregate total Corradino

  3. Past Work • For District 4 – Paper by Li, Ewing & Gross (late 1990’s?). • Other major urbanized areas throughout the US. • Encouraged by USDOT • Most models use some combination of: • Persons • Workers • Density • Children • Income – Almost all require this one **** • Accessibility Corradino

  4. Since FSUTMS Doesn’t Use Incomeand Previous Work Required Income • Use • Persons/HH • Workers/HH • Children • With • Without • Density (HH, Emp, Area) • Accessibility (Time & Trip Attractions) Corradino

  5. Model Form Multinomial Logit Sx = Exp(ux)/[Exp(u0)+ Exp(u1)+ Exp(u2)+ Exp(u3)] Where Sx = share of HH’s at each auto ownership level (0,1,2,3) ux = utility for level x = f(persons or workers/HH, density, accessibility) Corradino

  6. Density Calculation Density = (Households + Total Employment)/(net area) Corradino

  7. Accessibility Calculation • Inputs • Travel Time Skim Matrix (for GM) • Trip Attractions (from “trial” Gen run) • Friction factors • For each TAZ: Accessibility= Sum of: FF(t)*Attractions for each purpose Over all destinations Corradino

  8. Best Model • Households without children • Persons • Density • Accessibility • Rho-squared: 0.342683 Corradino

  9. Best Model • Households with children • Workers • Density • Accessibility • Rho-squared: 0.288637 Corradino

  10. Other Notes • Gross and Ewing found a rho-squared of 0.4704 for their model 4. • 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 children respectively. These models are at least as well as Gross and Ewing. • 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 respectively. These are still good models, but as expected, the task is more difficult when trying to estimate 4 levels. • The signs in all models are correct, and all variables included in the equations are significant at the 0.05 level and beyond for most variables. Corradino

  11. Remaining Work • County Biases will be tested • Life-Style Gen will have to be modified to use the new model • Actual model implemented in Matrix Corradino

  12. Questions? Corradino

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