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TPB Travel Forecasting Model, Version 2.3: Specification, Validation, and User’s Guide (Draft Report)

TPB Travel Forecasting Model, Version 2.3: Specification, Validation, and User’s Guide (Draft Report). Presentation to the Travel Forecasting Subcommittee Ron Milone and Mark Moran Metropolitan Washington Council of Governments National Capital Region Transportation Planning Board (COG/TPB)

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TPB Travel Forecasting Model, Version 2.3: Specification, Validation, and User’s Guide (Draft Report)

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  1. TPB Travel Forecasting Model, Version 2.3: Specification, Validation, and User’s Guide (Draft Report) Presentation to the Travel Forecasting Subcommittee Ron Milone and Mark Moran Metropolitan Washington Council of GovernmentsNational Capital Region Transportation Planning Board (COG/TPB) July 18, 2008 Ver2.3model_tfsPres_2008-07-18e.ppt

  2. Overview of the presentation • Overview of the Ver. 2.3 travel model • Overview draft documentation • Model release schedules • Detailed description of what is new in the Ver. 2.3 travel model • Truck models • Mode choice • Summary of model performance • Conclusions and next steps The Ver. 2.3 Regional Travel Model: A presentation to the Travel Forecasting Subcomm., 7/18/08

  3. Overview of theVer. 2.3 travel model • Base used for development: Ver. 2.2 travel model • Major enhancements • Updated of the medium and heavy truck models • Replacement of the 5-choice, sequential, multinomial logit mode choice model with a 15-choice, nested-logit mode choice model and the ability to conduct transit assignments • Calibration years: • 2002 for NL MC • 2005 for truck model • Validation years: • 2002 (transit) • 2005 (highway) • 2030 (for reasonableness) The Ver. 2.3 Regional Travel Model: A presentation to the Travel Forecasting Subcomm., 7/18/08

  4. Yet, some things remain the same: Ver. 2.3 vs. Ver. 2.2 • Both models share: • Modeled area (2,191 TAZ, 6,800 sq. mi.) • Trip-based, aggregate, four-step model • Four trip purposes (HBW, HBS, HBO, NHB) • Commercial vehicle model • Queuing delay function applied to freeways & ramps • Ability to model both fixed-price and variably priced toll facilities (e.g., toll roads, HOT lanes) The Ver. 2.3 Regional Travel Model: A presentation to the Travel Forecasting Subcomm., 7/18/08

  5. Overview of thedraft documentation • Ver. 2.3 model is in draft and so is the documentation • Report is divided into three main sections • Model specification and validation • User’s guide • Technical appendices • Some sections of the documentation are unfinished, especially in the user’s guide The Ver. 2.3 Regional Travel Model: A presentation to the Travel Forecasting Subcomm., 7/18/08

  6. Model release schedules The Ver. 2.3 Regional Travel Model: A presentation to the Travel Forecasting Subcomm., 7/18/08

  7. Ver. 2.3 draft documentation Focus of this presentation:What’s different between Ver. 2.3 and its predecessor, Ver. 2.2

  8. Ver. 2.3: Revised medium and heavy truck models • Motivation: • Previous truck models had not been updated recently • Air quality planning: Trucks are major contributors to nitrogen oxides (NOx) and airborne particulates • Difficulty: • Collecting observed travel patterns of trucks • Consequently, many MPOs use either “borrowed” truck models from comparable regions or truck models comprised of default parameter values taken from the literature The Ver. 2.3 Regional Travel Model: A presentation to the Travel Forecasting Subcomm., 7/18/08

  9. Ver. 2.3: Revised medium and heavy truck models • TPB initiated a project in FY-2005 • To develop a new commercial vehicle model (implemented in the Ver. 2.2 model) and • To revise the existing truck models using locally collected data (in the Ver. 2.3 model) • A consultant (Bill Allen) was retained to support this multi-year effort, which involved the development of an innovative truck modeling approach that obviated the need to collect operator-based information The Ver. 2.3 Regional Travel Model: A presentation to the Travel Forecasting Subcomm., 7/18/08

  10. Ver. 2.3: Revised medium and heavy truck models • TPB travel models have historically distinguished two types of trucks: • Medium • Definition: Single unit, two-axle vehicles with six tires (i.e., vehicles with dual rear wheels) • Examples: Recreational vehicles (RVs) or medium-duty delivery trucks • Heavy • Definition: Any multi-unit vehicle with three or more axles • Example: Tractor trailers • These designations have been retained The Ver. 2.3 Regional Travel Model: A presentation to the Travel Forecasting Subcomm., 7/18/08

  11. Ver. 2.3: Revised medium and heavy truck models • Structure • Trip generation and trip distribution models • Results in daily truck trips • Time-of-day process, before traffic assignment, results in AM, PM, and off peak • Medium & heavy truck trips are assigned to the highway network as a separate and distinct market (trip table) • More details to be found in Bill Allen’s presentation (next) The Ver. 2.3 Regional Travel Model: A presentation to the Travel Forecasting Subcomm., 7/18/08

  12. Ver. 2.3: Revised medium and heavy truck models • Ver. 2.3 traffic assignment procedures have been modified, as a result of the new truck models • Ver. 2.2: Loading of five trip tables • 1) SOVs and commercial vehicles; 2) 2-occupant HOVs; 3) 3+ occupant HOVs; 4) Total trucks - heavy and medium; 5) Air passenger vehicles • Ver. 2.3: Loading of six trip tables • Same as Ver. 2.2, except medium and heavy trucks are now loaded separately • Drawback: 6 trip tables means longer model run times • Advantage: Affords TPB staff the opportunity to explore the option of treating medium and heavy trucks as varying passenger car equivalents (PCEs) in the assignment process. This option is but one of many that will be evaluated in the coming months. The Ver. 2.3 Regional Travel Model: A presentation to the Travel Forecasting Subcomm., 7/18/08

  13. Ver. 2.3: Nested-logit (NL) mode choice model • A 15-choice, NL mode choice model (replaces the 5-choice, sequential, multinomial-logit mode choice model) • Includes • Three auto modes • Drive alone, shared ride 2, and shared ride 3+ • Four transit modes • Commuter rail, all bus, all Metrorail, and combined bus/Metrorail • Three modes of access to transit • Park and ride (PNR), kiss and ride (KNR), and walk The Ver. 2.3 Regional Travel Model: A presentation to the Travel Forecasting Subcomm., 7/18/08

  14. Ver. 2.3: Nested-logit (NL) mode choice model • Although not explicitly listed, the NL MC model can also model light rail transit (LRT), bus rapid transit (BRT), and street car. • TPB NL MC model was based on an earlier NL MC model developed by AECOM for WMATA in 2004-2005. • We have retained some features of the AECOM/WMATA model and have changed some features: • Table on next slide compares the two NL MC models The Ver. 2.3 Regional Travel Model: A presentation to the Travel Forecasting Subcomm., 7/18/08

  15. Ver. 2.3: TPB NL MC vs. AECOM NL MC The Ver. 2.3 Regional Travel Model: A presentation to the Travel Forecasting Subcomm., 7/18/08

  16. Ver. 2.3: Nested-logit (NL) mode choice model • Calibration data (assembled by AECOM; used by both agencies): • 2002 land use and networks • Control data • 2002 WMATA Metrorail survey • 2002 published transit boarding counts by operator • Other data • 2000 Regional Bus Survey • 2000 Census journey-to-work data • This contrasts with the Ver. 2.2 MNL MC model: • Calibrated with the 1994 Household Travel Survey • Validated to 2000 Census Transportation Planning Package (CTPP) data The Ver. 2.3 Regional Travel Model: A presentation to the Travel Forecasting Subcomm., 7/18/08

  17. Ver. 2.3: Nested-logit (NL) mode choice model • Definition of HOV trips has changed • SMNL (Ver. 2.2 and earlier): • “HOV trips” coming out of the mode choice model referred to only those that use HOV facilities for a substantial portion of their trip. • “LOV trips” included both drive-alone and carpools (provided the carpools did not use a preferential HOV facility). • NL (Ver. 2.3): • LOV refers to only the drive-alone trips. • HOV refers to all shared-ride trips, irrespective of whether they use an HOV facility or not The Ver. 2.3 Regional Travel Model: A presentation to the Travel Forecasting Subcomm., 7/18/08

  18. Ver. 2.3: Nested-logit (NL) mode choice model • The new NL MC model is applied using a Fortran program named AEMS.EXE, which replaces the COGMC.EXE program that has been used for years • AEMS is completely parametric, i.e., all characteristics for any given MC model are specified in a control file. • Characteristics represented in the control file include • nesting structure, market segmentation, utility/disutility functions, and the values of coefficients and constants. • AEMS can handle models with any nesting structure and up to 15 choices (a newer version can handle up to 18) The Ver. 2.3 Regional Travel Model: A presentation to the Travel Forecasting Subcomm., 7/18/08

  19. Ver. 2.3: Nested-logit (NL) mode choice model • Geographic market segmentation: • Seven superdistricts were combined to make 20 production/attraction “market segments” • There is one nesting constant for each market segment and each travel mode • Calibration consists of estimating these nesting constants • Automated calibration routine: CALIBMS The Ver. 2.3 Regional Travel Model: A presentation to the Travel Forecasting Subcomm., 7/18/08

  20. Ver. 2.3: Nested-logit (NL) mode choice model • Revised transit access coding • The consolidation station file/database • Six new fields/variables added • Sidewalk links and zonal walk links • Zonal auto-access links • Station transfer links • Zonal percent walk to transit calculations The Ver. 2.3 Regional Travel Model: A presentation to the Travel Forecasting Subcomm., 7/18/08

  21. Ver. 2.3 NL MC choice model:Consolidation station file/database The Ver. 2.3 Regional Travel Model: A presentation to the Travel Forecasting Subcomm., 7/18/08

  22. Ver. 2.3 NL MC choice model: Sidewalk links and zonal walk links • In Ver. 2.2 and earlier models, there was a walk network, used for transferring from one transit line to another, in downtown DC and downtown Silver Spring, MD • In Ver. 2.3, there is a sidewalk network in almost the entire modeled area • Regional sidewalk network (Mode 13) is generated using a new Fortran program WALKACC.EXE • WALKACC.EXE also generates zonal walk-access-to-transit links (Mode 16). The Ver. 2.3 Regional Travel Model: A presentation to the Travel Forecasting Subcomm., 7/18/08

  23. Ver. 2.3 NL MC choice model: Zonal auto-access links • Fortran program AUTOACC4.EXE is used to generate auto-access-to-transit links. Auto access links (Mode 11) are a function of multiple criteria: • Orientation toward downtown (defined as the Ellipse); • A backtracking penalty and a prohibition of crossing the Potomac River (except for trips from Loudoun County to MARC commuter rail); • A maximum link distance, which is a function of station type (e.g., terminal vs. non-terminal) and transit mode; See next slide. • Manually specified overrides (e.g., pentagon.prn, which lists zones that should be connected to the Pentagon with KNR-access, or slugging) The Ver. 2.3 Regional Travel Model: A presentation to the Travel Forecasting Subcomm., 7/18/08

  24. Ver. 2.3 NL MC choice model: Zonal auto-access links The Ver. 2.3 Regional Travel Model: A presentation to the Travel Forecasting Subcomm., 7/18/08

  25. Ver. 2.3 NL MC choice model: Station transfer links • Station transfer links are walk links connecting • Stations and sidewalks (Mode 12) • Stations and bus service (Mode 12) • Stations and PNR lots (Mode 15) • These links are generated automatically from data in the consolidated station file. • For PNR-station transfer links (Mode 15), the walk time is a function of parking capacity and cost, • Impedance (Mode 15) = (walking time from PNR to sta.) + (parking cost, converted to time @ $10/hr) • walking time from PNR to sta. = function of lookup table, e.g., <= 500 spaces = 2.0 min; 500-1000 spaces = 2.5 min; etc. • For details, see memorandum from Manish Jain – AECOM, “MWCOG network coding guide for Nested Logit Model.” February 2008. • Mode 15 links are generated by the Fortran program PARKER.EXE. • Mode 12 links are generated by the Fortran program STAPROTP_V1.EXE The Ver. 2.3 Regional Travel Model: A presentation to the Travel Forecasting Subcomm., 7/18/08

  26. Ver. 2.3 NL MC choice model: Zonal percent walk to transit • Zonal percent walk is the percent of a zone’s area that lies within walking distance to transit service • Short walk: ≤ 0.5 miles • Long walk: > 0.5 miles and ≤ 1.0 mile • (Previous: Short ≤ 1/3; Long ≤ 1.0) • The following walk designations are used: • Short walk to Metrorail; • Long walk to Metrorail; • Short walk to AM transit; • Long walk to AM transit; • Short walk to off-peak transit; • Long walk to off-peak transit. • A GIS procedure is used to develop point buffers around transit stop nodes and then overlay these point buffers with zone (TAZ) boundaries. The Ver. 2.3 Regional Travel Model: A presentation to the Travel Forecasting Subcomm., 7/18/08

  27. Ver. 2.3 travel model:Summary of model performance • General observations on 2005 simulation • Ver. 2.3 Est/Obs VMT = 1.03 for the MSA • By contrast, Ver. 2.2 was 1.00 • Ver. 2.3 total vehicle trips ≈ 1.5% higher than Ver. 2.2 • Ver. 2.3 total VMT ≈ 4.0% higher than Ver. 2.2 • Ver. 2.3 transit ≈ 3.0% higher than Ver. 2.2 • Details on calibration results, model performance can be found in the draft report The Ver. 2.3 Regional Travel Model: A presentation to the Travel Forecasting Subcomm., 7/18/08

  28. Conclusions • Version 2.3 travel model is in DRAFT (beta release) • Evaluation will proceed in the coming months The Ver. 2.3 Regional Travel Model: A presentation to the Travel Forecasting Subcomm., 7/18/08

  29. Next steps • Begin sensitivity testing • Possible refinements to the model • Move from Cube TP+ ver. 4.1 to Cube Voyager ver. 5.1 • Implement a procedure for the applying the transit constraint through the regional core • Consistent networks • HOT lane evaluation The Ver. 2.3 Regional Travel Model: A presentation to the Travel Forecasting Subcomm., 7/18/08

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