Statewide and Megaregional Travel Forecasting Models: Freight and Passenger (2017) / Chapter Skim
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Pages 69-94
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70 chapter seven Case examples Five case examples were selected to demonstrate typical implementations of statewide and mega regional models. However, standards for model application do not exist, as every implementation is unique and geared toward the needs of an individual state.
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71 The Chesapeake Bay Megaregion Model (CBM) for the megaregion around Washington, D.C.
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72 megaregions nationally, and to some respect even globally, the twolayer approach facilitates to represent the study area with sufficient detail, yet acknowledges that megaregions cannot be treated as monolithic islands. 7.1.2 model overview The megaregion framework implemented for the CBM is shown in Figure 49.
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73 trends, while nonbasic employment is driven by statespecific personal income forecasts. The land use model further allocates these state control totals to model zones.
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74 years 2000, 2005, and 2009. The ratio of employment for each county is then extrapolated for 5year periods beginning in 2010 and ending in 2030 using an exponential smoothing method.
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75 Commodity flows between zones are converted into trucks trips using average payload factors pro vided by FAF. These factors describe how many tons of a given commodity are carried by a truck on average.
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76 North America level with the megaregional level. On the other hand, horizontal integration captures the interaction between different modeling domains, such as transport models with land use models.
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77 between commodities and consumption. Special generators were developed for counties whose actual tonnage (from the Transearch data)
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78 generator attractions were calculated for unique land use types, such as universities, hospitals, military bases, and airports. Doubly constrained gravity models are used for trip distribution, using distance as the measure of impedance for infrequent longdistance trips and travel time for all other trip purposes.
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79 7.2.4 innovative data development The developers of the Arkansas model had to overcome several data shortcomings, with the lack of household and truck travel survey data being the most significant. It is common in such cases to bor row or assert models, or synthesize them using data from different sources, and to calibrate the model to what local data are available.
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80 • Considerable work went into the development of a graphical user interface and standardized reporting, which make the system and its outputs more accessible to both modelers and their clients. Having a model that is easier to use enables AHTD staff to spend more time evaluating results, rather than setting up and running the model in an ad hoc manner.
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81 Partnerships Caltrans has partnered with several agencies to fund and direct its statewide data and modeling pro gram. The firstgeneration model was funded through university research, as is work on a new freight modeling framework.
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82 Overview of the Modeling System The second version of the California Statewide Travel Demand Model (CSTDM) was delivered in 2014 (Cambridge Systematics 2014)
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83 was an integral part of the first generation statewide model, but is not an active part of the current version. The network includes more than 325,000 nodes, including its sparse representation of the national Interstate and U.S.
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84 7.3.2 The California high-speed rail ridership and revenue model The California HighSpeed Rail Authority maintains a separate ridership forecasting model used to support business and system planning, as well as corridor studies and analysis of alternative alignments and phasing of implementation. It is a complete statewide model, and uses some of the same data used to develop the Caltrans model.
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86 The BPMV3 system and its predecessors have been used to generate ridership and revenue estimates for initial and detailed system planning and in support of corridor studies and evaluation of candidate initial operating segments. This has included the environmental studies required at all levels of analyses for the program, and use for stationlevel impact analyses.
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87 7.4 Florida sTaTewide model The Florida Statewide Model is a particularly interesting case example for this report for two reasons. First, the consistency between MPO models and the statewide model in terms of input data and model design is remarkable.
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88 7.4.2 model structure The person transportation model is a traditional tripbased, 3step travel demand model. Florida's Turn pike Enterprise has developed a separate model that validated well and has been used to provide input data for the development of the statewide model.
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89 The network covers the entire country, with more detail in Florida and a decreasing degree of detail outside of Florida. Network resolution and zone system resolution decrease in detail similarly and gradually the further one travels away from Florida.
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90 To further improve freight modeling, a tourbased truck model is envisioned as well. The Freight Sim model system was originally developed with a tourbased truck model for Chicago.
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91 within a single framework, with linkages to various evaluation and impact models. It motivated a revival in land usetransportation modeling in the U.S.
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92 travel models. The Oregon Household Activity Survey (OHAS)
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93 A flow chart of the SWIM2 system in shown in Figure 58. The economic, land use, and transporta tion models are tightly integrated.
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94 The SWIM2 system was calibrated and implemented in a staged manner. The preparation and test ing of the software code, preparation of validation and calibration data and targets, and estimation and calibration of initial parameters were completed first.
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95 addition, two ODOT staff members have been involved for at least half of their time in model design, development, and implementation over the entire period that TLUMIP has been active. A final key to the success of the SWIM2 system was an active international peer review panel.
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