Lexington Area TransCAD Travel Demand Model - PowerPoint PPT Presentation

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Lexington Area TransCAD Travel Demand Model

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  1. Lexington Area TransCADTravel Demand Model July 22, 2003 Kentucky Traffic Model Users Group Meeting Kyeil Kim, Ph.D. Bernardin, Lochmueller & Associates, Inc.

  2. Main Features • Consists of separate time-of-day (TOD) models • Realistic free-flow speed based on a speed survey and HCM-based signal delays • Varying capacities by TOD for reversible lanes • Model parameters are based on recent travel survey and KYTC’s HIS database. • 2-stage assignments: Initial and Feedback • User-friendly model GUI

  3. Model Area

  4. Roadway Network • Incorporation of KYTC’s HIS and geometric/operations data • All MINUTP network attributes • FHWA functional class, posted speeds, etc. • Number of lanes, reversible lanes & bike lanes • Area type, shoulder widths, median type, etc. • Traffic signals & multi-way stops (signal priority, multiple signals) • Turn prohibitors

  5. TAZ DB • Total 489 zones • Internal zones = 445 zones • External zones = 44 zones • 51 data attributes • Date related to population and household • Employment by SIC code • Student population, group quarters & school enrollment • Vehicle ownership • Key data for estimating trip productions and attractions


  6. Speed/Capacity Estimation • Free-flow speed, peak-hour capacity & daily capacity • A special GIS-dk program to estimate directional capacities by TOD & free-flow speed • Consideration of changes in reversible lanes by TOD • Free-flow speed = f (functional class, posted speed, number of lanes, facility type, delays on interrupted facilities) • Daily capacity = f (functional class, number of lanes, facility type) • Peak-hour capacity = max. service flow * adjustment factors • where, Adjustment factors = f (geometric data, functional class, facility type, area type, delays on interrupted facilities)

  7. Speed/Capacity Estimation (Cont’d) • Delays on interrupted facilities • HCM 2000 procedure • delay/veh = uniform delay * PF + incremental delay + initial queue delay • where, PF = progression factor = f (arrival type, g/C) • uniform delay = • Varying g/C’s and PF’s by signal priority and multiple signals

  8. Lexington ModelGUI

  9. Lexington ModelGUI

  10. Trip Generation • Six internal trip purposes: - HBW, HBK12, HBU, HBO, NHBW & NHBO • Trip production • Cross-classification technique • Data: The 2000 Knoxville Household Travel Behavior Study, The 1999 Indiana University Travel Demand Survey • Analysis of Variance (ANOVA) and non-parametric correlations techniques to identify the predictor variables for various trip purposes • Stratification curve: distribution of households in a zone over various • levels of the predictor variables

  11. Trip Generation (Cont’d) Trip production model

  12. Trip Generation (Cont’d) Trip attraction model: the Atlanta regression model

  13. Trip Distribution • Doubly-constrained Gravity model for the 6 internal trip purposes & E-I trips • Friction factors - Initial factors from the old MINUTP model • Fitting to Gamma function for smoothing the factors • Adjustment of Gamma parameters to arrive at correct trip lengths by trip purpose • Socioeconomic (or K) factors

  14. Vehicle Occupancy Vehicle occupancy rates by trip purpose • HBW  1.09 persons/vehicle • HBK12  1.96 persons/vehicle • HBU  1.20 persons/vehicle • HBO  1.83 persons/vehicle • NHBW  1.17 persons/vehicle • NHBO  1.75 persons/vehicle (Source: The 2000 Knoxville Household Travel Behavior Study)

  15. Time-of-Day • AM peak (06:30~09:00); Midday peak (12:00~13:30); PM peak (15:30~18:00) and Off-peak • TOD factors - Split the 24-hr trip table into tables by TOD - by trip purpose • Directional factors - Convert trip tables in a production-attraction format to origin- destination tables - by trip purpose and by TOD • Data Source: the 2000 Knoxville Household Travel Behavior Study

  16. External Trips • 44 external stations • E-E trips • The 1994 O-D survey by Wilbur Smith Associates  Most of E-E trip interchanges except for the interstate and US60 exchanges • Kentucky Statewide Travel Model via critical link analysis  E-E trip interchanges for the interstate and US60 external stations • Modlin Equations  A check of reasonableness • E-I trips = ADT’s - E-E trips at each external station • 27 stations of the 44 stations carry through trips

  17. Traffic Assignment • Time-of-day user equilibrium assignments - separate AM-peak, Midday-peak, PM-peak & Off-peak assignments • Improved free-flow speeds and varying capacities by TOD by reversible lanes • Separate volume-delay functions (defaults) • Unsignalized facilities   = 0.20;  = 10.0 • Signalized facilities   = 0.05;  = 10.0 • Feedback assignment

  18. Feedback Loop 24-Hour Average Speed Gravity Model TOD Trip Table Factoring AM-peak Assignment Midday-peak Assignment PM-peak Assignment Off-peak Assignment 24-Hour Weighted Average Congested Link Speed

  19. CAL_REP • Assignment post-processor written in GIS-dk and incorporated in the GUI • Various error statistics by functional classification, volume group, screenline, cutline and specific corridors • Error statistics • total counts, average counts, counts standard deviation • total loadings, average loadings, loadings standard deviation • % root mean square error • mean error, % error • total counts VMT, total loadings VMT, % VMT error

  20. Assignment Results

  21. CAL_REP Report • Loading % error = -1 % • Loading VMT error = 0.9% • % RMSE = 25% • Interstate = 0.03% (% error); -2.6% (VMT error) • Urban Principal Arterial = -1.3%; -3.1% • Urban Minor Arterial = -3.8%; 3.7%

  22. In Progress • Model runs for future years and post-processing • 2030 with committed projects only • 2010 with committed plus Plan projects scheduled for completion by 2010 • 2020 with committed plus Plan projects scheduled for completion by 2020 • 2030 with all projects in the current LRP • “Multinet” feature in GUI for efficient network data handling

  23. THANK YOU!