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* Alan Horowitz, White Paper: Statewide Travel Demand Forecasting (2009)
* Alan Horowitz, White Paper: Statewide Travel Demand Forecasting (2009)
Revision as of 17:17, 8 March 2018
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- 1 Introduction
- 2 Statewide Model Status/Rationale/Usage
- 3 Statewide Models: Data
- 4 Statewide Models: Components
- 5 Statewide Modeling Subcommittee ADA10(2)
- 6 Statewide Modeling Resources
Statewide travel forecasting models predict all travel in the state, potentially by all modes, for both goods and people. Logically included with statewide models are super-regional models that cover all or parts of multiple states, and possibly the whole US. The importance of statewide models stems directly from the amount of long-distance and intercity travel in the US. According to the 2001-02 NHTS just under one-third of all person miles are long-distance (as defined as more than 50 miles within the NHTS), and according to the 2002 Commodity Flow Survey the vast majority of freight ton-miles are long distance. Statewide models go beyond metropolitan models principally by including larger, if not all, portions of long distances trips and by explicitly including passenger and freight modes for intercity travel. The field of statewide modeling is still maturing, even though models have been deployed in Michigan and Kentucky for more than 40 years. The total number of states with active models now stands at 32 with one or two states completing a new model each year.
There have been several important documents and event in the dissemination of information on statewide model development.
Landmark documentation includes:
- Guidebook on Statewide Travel Forecasting” and Irvine Conference, Transportation Research Circular E-C011, 1999
- “Statewide Travel Forecasting Models”, NCHRP Synthesis #358, 2006 
- “Forecasting Statewide Freight Toolkit”, NCHRP Report #606, 2008
- NCHRP Report 735 Transferable Parameters for long distance and rural trip-making (2012)
- NCHRP 8-36(91) Validation and Sensitivity Considerations for Statewide Models (2010)
Statewide Modeling Meetings and Workshops includes:
- TRB Annual Meeting Sessions.;
- Meetings of the TRB Subcommittee on Statewide Travel Forecasting Models;
- Statewide Travel Demand Modeling: Peer Exchange, Transportation Research Circular E-C075, September 2004;
- Statewide planning conference (Atlanta 2009) with statewide modeling workshop; and
- 2013 Planning Applications Conference Workshops.
The initial motivation for information dissemination was to encourage the development of models in states that did not have them, but a more recent motivation has been to foster research and development to improve models across-the-board. Persistent dominant themes emerged from each of these sessions, conferences and reviews:
- Statewide models have for the most part developed along similar methodological lines to traditional metropolitan models; however, there is less certainty as to what should be contained within a statewide model.
- The largest problems in implementing statewide models relate to issues of scale.
- Models from different states vary greatly in complexity, cost and development time.
- Models are most successful when they are able to address statewide priorities as expressed by legislators and other political leaders.
- There are major deficiencies in our data about long-distance passenger travel and rural passenger travel.
- Statewide models are more compatible with secondary freight data sources, such as the Commodity Flow Survey, than are metropolitan models.
- There is keen interest among states (with or without models) in the progress other states have made in deploying models.
The statewide modeler community, centered on the TRB Subcommittee on Statewide Travel Forecasting, is promoting selective research topics to improve the state-of-the-practice. Successes have included multiple NCHRP projects or tasks that have documented the current state-of-the-practice, expanded our knowledge of freight forecasting and outlined a prospective national travel forecasting model.
Statewide Model Status/Rationale/Usage
Rationale for statewide models
"Historically travel demand models have been primarily created for urban and regional areas and have focused on forecasting travel demand within metropolitan areas. In the last 15 to 20 years, many state Departments of Transportation (DOT) have undertaken the development of statewide transportation demand models. Statewide models are used to forecast travel demand for the entire state and often areas within contiguous states. Urban transportation models focus on travel within and through the urban area. These trips, for the most part, are short-distance home-based and nonhome-based trip purposes. Conversely, statewide models focus on long-distance trips, freight, intercity, and rural trips that are frequently categorized into business, personal, and recreational purposes.
(As of September 2010,) over 30 states have developed or are developing statewide models. These models are often used to help formulate policies, to prioritize projects, and to identify the potential revenue streams from toll road, intercity rail, and other major transportation investments. Because these models play such a significant role in the planning process, careful and thoughtful evaluation of how well these models reproduce existing travel markets as well as their sensitivity to major market segments and behavioral responses is an increasingly important consideration for state and Federal DOTs. Most of these statewide or superregional models are built upon practices originally developed for a mono-centric urbanized area." http://statewideplanning.org/resource_list/validation-and-sensitivity-considerations-for-statewide-models/
Emerging uses of statewide models
From NCHRP project 8-36-B Task 91, emerging uses of statewide models include:
- Identification of transportation needs in rapid growth state (Arizona);
- Toll modeling (Florida, Delaware);
- Commodity flows (Iowa especially grain);
- Air quality (Massachusetts, Rhode Island); and
- Combined land use, travel demand, economic activity (Ohio and Oregon).
From NCHRP project 8-36-B, statewide models frequently use different market segments than urban/regional models. Long distance travel and freight travel are very important components of the models and thus the data needed for these models emphasizes long distance travel data and freight data.
Statewide Models: Data
Statewide Models: Components
Primarily from Task 91, NCHRP project 8-36-B, key data include:
- Long distance travel data sources include the 1995 American Travel Survey (ATS). A recent FHWA study (2013) updated the 1995 ATS with the Traveler Analysis Framework (TAF) for the years 2008 and 2040;
- Census data: Census Public Use Microdata, Census Transportation Planning Package (CTPP);
- Freight Data: Commodity Flow Survey (CFS), Freight Analysis Framework (FAF), Vehicle Identification and User Survey (VIUS), Transearch;
- Employment data: Dun and Bradstreet; Employment Security Data (ES-202), Info USA;
- Surveys: National Household Travel Survey (NHTS), household travel surveys;
- Economic models: Regional Economic model (REMI);
- Other data: MPO data, origin-destination data.
Land use and economic activity
A few advanced statewide models, such as the statewide models of California, Ohio, or Oregon, include land-use models that update the allocation of population and employment between model years.
Statewide/urban model integration
There are pros and cons on the level of integration between urban/regional models and statewide models. For example, if a statewide model uses the same demographic assumptions as a state's MPO models, there is a greater likelihood of consistency among different models. On the other hand, use of MPO demographic forecasts in a statewide model could lead to complications in maintaining and updating the statewide model. Without continuous coordination, the statewide model might become outdated as MPOs make corrections and updates to demographic data on a regular basis. Another consideration is that MPO forecasts likely reflect local politics and policies whereas use of independent forecasts for a statewide model could be considered as unbiased.
NCHRP Project 8-36-B Task 91 by Cambridge Systematics gives an excellent overview of validation and sensitivity issues to be considered in the development of statewide models. Key topic areas in the report include a look at seven state’s validation methodology (Arizona, Florida,Indiana, Tennessee, Texas, Utah and Wisconsin), structural metrics, reasonableness checks and sensitivity testing.
Long distance travel
"The modeling of long-distance trips in statewide models differs from that of urban and regional models that focus on differentiating home-based from non home-based trips. Long-distance trips are more likely to be divided into categories by frequency of travel or by purpose such as recreational/tourist versus business-oriented trips. Such considerations are more likely to be indicative of long-distance variations by trip length, mode choice, and other aspects of travel...
In the context of statewide forecasting, long-distance trip-making... constitute(s an) important market segment(s), much more so than in urban models. Information describing these markets, and how these markets vary from state to state, is somewhat sparse, and many states do not have the resources to initiate original data collection to develop a set of model parameters... The 1995 American Travel Survey (ATS) datasets are dated; however, these data are the only long-distance data that provide statistically sound estimates of long-distance travel in and between the states. Although the 2001 National Household Travel Survey (NHTS) had a long-distance component, this survey did not have sufficient samples to calculate estimates of long-distance travel for most states (New York and Wisconsin were exceptions to this, because of the large add-on in the former and stratified sampling of the latter, although neither add-on was included in the official 2001 NHTS long-distance file)." onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_735.pdf
NCHRP Report 735 Transferable Parameters for long distance and rural trip-making (2012) is a valuable source of information on long distance travel. The NCHRP report explains how statewide models have fundamental differences from urban models due to long distance trip making and rural trips. The report contains chapters on:
- long distance data sources;
- transferability and typologies;
- trip generation parameters and benchmark statistics;
- auto occupancy and mode choice parameters; and
- conclusions /comparisons.
The report also contains the following appendices:
- Recent examples of long-distance travel demand studies (ORNL, UMD);
- Travel behavior data from other countries;
- Modal-based travel data;
- Other demographic and origin-destination data;
- Urban versus rural truck trips; and
- Review of statewide models.
Over 30 states across the U.S. have operational statewide models that are used for policy analysis. Some case studies exemplify how such models are designed and used to support statewide planning. If you know another statewide model really well, please add a short description here.
National models strongly relate to statewide models since they use similar data sources and the movement to develop national models came from a statewide modeling committee research suggestion. The conventional thinking is that an accurate national model could be used as a source of information – networks, trip table, standard attributes – for developing more detailed statewide models. The National Travel Demand Forecasting Model Phase I Final Scope report developed a framework for developing a national model. The scope had the following components:
- Identify alternative model structures;
- Obtain and prepare input data;
- Model development and validation;
- Develop tools and documentation; and
- Future directions.
There has been significant movement in starting the development of the national model by FHWA, Office of Policy. This agency has started research on new sources of data for long distance travel as a first step in developing the national model.
Statewide Modeling Subcommittee ADA10(2)
The statewide travel forecasting committee has been in existence about 14 years. It is dedicated to statewide and multi-state travel forecasting. It has two parent committees: Statewide Multimodal Transportation Planning and Transportation Demand Forecasting. The committee website is http://www4.uwm.edu/statewidetrb/
Major components of the web site include:
- Presentations at the TRB Annual Meeting (2004, 2006-2013) and at the 2013 Planning Applications Conference;
- Source documents (listed in statewide modeling resources below);
- Organizations and individuals with expertise in statewide modeling;
- Data sources for use in statewide model development;
- Minutes from subcommittee meetings for 2002 and 2005-2103 along with members and friends of the committee; and
- A listing of possible research topics pertaining to statewide travel demand modeling.
ADA10(2) will meet at the annual TRB meeting on January 15th at 8:00 AM EST in the Hilton, Northwest. The agenda will focus on existing committee activities, research focus area status, and upcoming year’s activities.
Statewide Modeling Resources
- FHWA, Guidebook on Statewide Travel Forecasting (1999)
- NCHRP Synthesis 358 Statewide Travel Forecasting Models (2006)
- NCHRP Report 735 Transferable Parameters for long distance and rural trip-making (2012) http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_735.pdf
- NCHRP 8-36B Task 91: Validation and Sensitivity Considerations for Statewide Models (2010) http://onlinepubs.trb.org/onlinepubs/nchrp/docs/NCHRP08-36(91)_FR.pdf
- Transportation Research Circular E-C075, August 2005, Statewide Travel Demand Modeling, A Peer Exchange. http://onlinepubs.trb.org/onlinepubs/circulars/ec075.pdf
- AASHTO Standing Committee on Planning, National Travel Demand Forecasting Model Phase I Final Scope, Cambridge Systematics (2008). http://onlinepubs.trb.org/onlinepubs/nchrp/docs/NCHRP08-36(70)_FR.pdf
- Alan Horowitz, White Paper: Statewide Travel Demand Forecasting (2009)
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Pages in category "Statewide models"
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