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Pages 26-46

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From page 26...
... 1 Proposed Work Elements for the TPB Models Development Program Introduction The TRB Review Committee indicated during the September 12, 2003 telephone conference with TPB staff that it would be very helpful to them to review proposed work program elements from the TPB staff as the panel prepares its second letter report.
From page 27...
... 2 • "The committee's findings are based upon its experience in regions with populations, institutional complexity, travel patterns, and air quality planning requirements comparable to those of the metropolitan Washington area." (p.
From page 28...
... 3 Finally, there are three observations by the TRB Committee which the TPB staff believes require further consideration and discussion between the TRB Committee, TPB staff and other interested parties: 7. TPB's extensive use of adjustment factors in trip generation, trip distribution, and mode choice to enhance the match between simulated and observed base-year data undermines the fundamental behavioral logic of the four-step modeling process.
From page 29...
... 4 Activities aimed at improving the current application method now known as the Version 2.1/TP+, Release C model and the emissions post-processor constitute the Application track (Track 1)
From page 30...
... 5 Figure 1 Multi-year staging of models development activities FY-04 FY-2005 FY-2006 FY-2007 FY-2008 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 1. Application Track A
From page 31...
... 6 Application (Track 1) In formulating Application track work elements TPB staff has considered the observations made in the first letter report and has shared the concerns with stakeholders in the region.
From page 32...
... 7 arrival model which estimates the shares of access modes at Metrorail stations, will be migrated to the TP+ platform. These models will be estimated using information contained in the 1994 HTS and the 1994 Metrorail Survey.
From page 33...
... 8 Fi gu re 2 St ru ct ur e of th e R eg io na l M od el M od e C ho ic e M od el
From page 34...
... 9 1.B Business and Commercial Trips As is the case in many metropolitan areas, the structure of the commercial truck models employed by TPB were developed many years ago, and have been informed by the results of internal and external truck surveys periodically. Most recently, an external truck survey was undertaken for the region in spring and summer 2003, and the information is being tabulated this fall.
From page 35...
... 10 selected method and related modeling changes will be produced during the second half of FY2004. 1.D Minimize the Use of Adjustment Factors The TRB Committee has commented that "TPB's extensive use of adjustment factors in trip generation, trip distribution, and mode choice to enhance the match between simulated and observed base-year data undermines the fundamental behavioral logic of the four-step modeling process." TPB staff disagrees with the statement that the fundamental behavioral logic is undermined, and has undertaken a review of practice in several major MPOs.
From page 36...
... 11 and mode split steps conducted earlier in the sequential trip distribution/mode choice/traffic assignment procedure. TPB staff has examined the results of some sample applications of the TPB's speedback procedure to assess the level of agreement achieved between the various steps in the modeling process.
From page 37...
... 12 1.F. Emissions Post-processor The TRB Committee has observed that "the TPB's procedure for estimating hourly traffic volumes and speeds – is questionable -- -- Testing will be needed to determine the procedure's effects on emissions estimates." The TRB Committee's first letter report did not provide any specific suggestions for sensitivity tests to be conducted on the TPB's emissions estimation procedures.
From page 38...
... 13 Table 1 Emissions Post-Processor Sensitivity Analysis 2005 MSA Summary Test 1 Base Test 2 Test 3 Freeway capacity reduced by 22%; Freeway speed based on 'standard' speed-flow function using the postspread hourly volume. Freeway capacity unadjusted; speed based on 'standard' speed-flow function using the maximum pre/post- spread hourly volume.
From page 39...
... 14 case estimates for 2005 and 2015 respectively. Since running emissions represent less than half of total mobile emissions for VOC in both 2005 and 2015, and about 86 and 83 percent for NOx for 2005 and 2015 respectively, these tests generally show relatively small changes in mobile emissions estimates in all of the cases.
From page 40...
... 15 1.G Incremental Refinements to the Version 2.1C Model This is a global activity to integrate the latest refinements emerging from the ongoing program, as these can be made ready for production modeling (i.e., air quality conformity of the TIP and Plan, and project planning studies)
From page 41...
... 16 Tour-based models have been used in European countries, such as Sweden and the Netherlands, for a number of years. By contrast, their use in the U.S.
From page 42...
... 17 • the need to add jurisdictions to the modeled region reflecting the EPA-designated nonattainment boundary. Considerable time and energy were expended in getting this 2,191-zone structure in place in 1994.
From page 43...
... 18 The first option would be to conduct a new regional household travel survey similar to the 1994 COG/TPB Household Travel Survey. This survey would be a trip-based survey designed to support further refinement and validation of the COG/TPB Version 2.1 four-step travel forecasting model.
From page 44...
... 19 It is anticipated that this first option for a new regional household travel survey could be designed to fit within expected UPWP budget levels over a two fiscal year period. The second option for the conduct of a new regional household travel survey would be very similar to the first option, except that it would also include a GPS household vehicle tracking add-on sub-sample.
From page 45...
... 20 4.C Analysis of Census Journey to Work Data This project will obtain, tabulate, and analyze Census Journey to Work data collected in the 2000 Census. This work activity will include tabulation and analysis of Summary File 3 (SF 3)
From page 46...
... 21 Development and Research tracks. TPB staff has prepared a number of special summaries and sensitivity tests of the Version 2.1/C model at the request of the TRB review panel during FY2003 and FY-2004.

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