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Analyzing the Effects of Tolls and Operating Costs on Statewide Travel Patterns

Analyzing the Effects of Tolls and Operating Costs on Statewide Travel Patterns. Vishal Gossain Thomas A. Williams Joseph P. Savage Jr. Christopher E. Mwalwanda. OBJECTIVES.

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Analyzing the Effects of Tolls and Operating Costs on Statewide Travel Patterns

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  1. Analyzing the Effects of Tolls and Operating Costs on Statewide Travel Patterns Vishal Gossain Thomas A. Williams Joseph P. Savage Jr. Christopher E. Mwalwanda

  2. OBJECTIVES • Illustrate the application of the Generalized Cost Function (GCF) as a proxy to a toll diversion curve • Investigate the use of Operating Costs in the GCF • Highlight pros and cons of implementing the GCF for statewide modeling. • The analysis presented here does not represent the WSA procedure for toll based revenue estimation.

  3. MODEL USED • Texas Statewide Analysis Model (Texas Department of Transportation) • Four Step Travel Demand Model • Implemented in TransCAD using GISDK programming

  4. SALIENT FEATURES

  5. 288 COUNTIES COVERED (Including some outside Texas)

  6. 4600 Zones + 142 External Stations, 323,350 square miles more than 35 million population

  7. 106,000 miles of network, 54,500 links with over 1 billion VMT

  8. Four Step Model • 2030 horizon year chosen, base year data grown to 2030 based on TDC forecasts and disaggregated. • Passenger Trip Generation: TripCAL5 • Passenger Trip Distribution: ATOM2 • Passenger Mode Choice: Nested logit

  9. Four Step Model • Freight Trip Generation using regression equations developed based on Reebie and WEFA • Freight Trip Distribution: ATOM2 • Mode Choice: Logit

  10. Assignments • All or Nothing Assignment • STOCH Assignment • Incremental Assignment • Capacity Restraint • User Equilibrium • Stochastic User Equilibrium • System Optimum Assignment

  11. User Equilibrium Assignment • TransCAD Multi Modal Multi Class Assignment utilized. • All travelers have identical perceptions of time and cost. • Equilibrium problem: No traveler can reduce his/her travel time by switching to another path (Wardrop conditions)

  12. User Equilibrium Equation Generalized Cost Function Dummy variable Number of vehicles from i to j

  13. Implementation Compute GC for each link using seed values (Free flow times) Compute GC for each link with new solution Compute shortest paths for every O-D minimizing GC (Solcurr) Assign all O-D trips to shortest path (Soltemp) Solcurr = (1-λ) Solcurr + λ Soltemp , λ chosen to minimize new objective function (Frank-Wolfe algorithm) No Solution converged? Yes Terminate

  14. Crux of Equilibrium: VDF function • Bureau of Public Records Function Capacity Free Flow Time

  15. Crux of Equilibrium: VDF function • Conical Volume Delay Function

  16. A Generalized Cost Delay Function Value of Time for mode m Passenger Car Equivalent Volume Delay Function Toll for Section i and mode m

  17. Toll Sensitivity • What is the current and anticipated demand in the corridor? • Toll Sensitivity as a proxy to potential demand • How to incorporate sensitivities related to willingness to pay operating cost ?

  18. Key Variables • Value of Time • Operating Costs • Volume Delay Curves – Travel Time Savings (Urban vs. Rural)

  19. Toll Corridor

  20. Toll Corridor

  21. Toll Corridor • A high speed (>=80 mph) competing toll corridor • Separate Auto only (6 lanes) and Truck only Routes (4 lanes) • Separate Toll Rates for Auto and Truck • Limited Access (provided to only FM and above category roadways)

  22. Value of Time for Auto • Urban versus Intercity Markets • Income / Wage Rate Distribution • Rural / Purpose Segmentation and Distribution • Average 10-12 cents per minute ($7.2 per hour) for rural interstate travel in 2005 dollars

  23. Variations in Value of Time for Auto 2004 Value of Time per Hour 2004 Value of Time per Hour

  24. Value of Time for Trucks • Commercial Vehicle/Commodity Composition • Fleet/Shipper versus Independent Operator • Just-in-Time versus Flexible Scheduling • Long versus Short Haul • $ 26.7 per hour • $ 17.4 - $ 22.6 per hour • $23.4 per hour based on logit model • Adopted Value of 42 cents per minute ($25.2 per hour) in 2005 dollars

  25. Operating Costs • Helps to control utilization of unrealistic paths compared to a pure time based GC function • Full Costs versus Perceived Costs

  26. Operating Costs Direct Costs • Importance of fuel costs with the current volatility in fuel prices. Indirect/Hidden Costs • Maintenance (tires, oil and other work) • Unanticipated repairs • Depreciation in the value of the vehicle • Depends on speed (magnitude and duration) • Depends on pavement roughness

  27. Operating Costs • 15.3 cents per mile recommended for auto and 43.4 cents recommended for trucks • City Driving conditions (19.1 cents and 52.9 cents respectively) • Poor pavement quality (17.9 cents and 48.9 cents) • All costs mentioned in 2003 dollars; 14 cents per mile for auto and 42 cents per mile for trucks used in 2005 dollars

  28. Modeling Criteria • Values of Time and Operating Costs based on overall market averages • Toll rates set at 0 to 30 cents per mile • UE Assignment, BPR VDF • Optimal number of iterations and convergence criteria

  29. Typical Toll Rates Ranges 2004 Cash Toll Rates per mile Nationwide Toll Facilities Averages (USA - 75 Facilities)

  30. Toll Sensitivity Curve (12 runs) UE BPR

  31. Sensitivities to Toll Percentage of the total length of the corridor which has traffic more than 1000 vehicles for the considered toll rate

  32. UE Assessment • Fixed point equilibrium cut off • The same generalized cost function for all links (toll or non toll) • Perfect perception of time and costs along each route by all drivers.

  33. Stochastic User Equilibrium • No perfect information about network characteristics • Different travel costs perception • Eliminates “zero volume” roads • Implemented in TransCAD (utilizes Method of Successive Averages) • Requires large number of iterations and hence a longer run time

  34. Stochastic User Equilibrium • Utility Maximization. • Random error term added to the utility to mimic differences in perceived costs and imperfect information. Randomly distributed error Deterministic Utility All influencing factors

  35. Stochastic User Equilibrium • Estimate probability • Multinomial Logit, Multinomial Probit etc.

  36. Stochastic User Equilibrium (8 runs)

  37. Stochastic User Equilibrium

  38. Conical Volume Delay Function (12 runs)

  39. Conical Volume Delay Function

  40. Operating Cost Analysis

  41. Operating Cost Analysis

  42. Operating Cost Analysis

  43. SUMMARY • Toll road modeling using statewide models has its limitations. • Inclusion of operating costs is beneficial and requires further analysis. • Different assignment techniques should be evaluated on a case by case basis. • The analysis presented here does not represent the WSA procedure for toll based revenue estimation.

  44. SUMMARY • A single Generalized Cost function alone may not be adequate to capture the differences in the elasticity associated with tolls and travel times. • Volume delay functions (reflecting adequate delay in urban vs rural areas) and GC function should be carefully considered and analyzed on a case by case basis.

  45. QUESTIONS / COMMENTS WILBUR SMITH ASSOCIATES http://www.wilbursmith.com

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