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CHAPTER ONE
INTRODUCTION
Statewide travel forecasting models address numerous · There are data opportunities for statewide models that
planning needs by estimating, for a future date, the num- are not available for urban models, such as freight flow
ber of vehicles that use major transportation facilities databases and economic forecasts for subareas.
within a state. Statewide models can encompass both pas-
senger and freight issues, and provide forecasts for a vari- Statewide travel forecasting models seek to determine the
ety of modes including highways, urban transit systems, amount and location of travel by looking at parts of the traveler
intercity passenger services, airports, seaports, and rail- decision processes. A model based on behavioral principles
roads. Statewide models are particularly useful for fore- would differ substantially from one based entirely on empirical
casting in rural areas that are not covered by urban travel findings, such as growth factor methods. Nonetheless, some
forecasting models. Statewide models provide a consistent states feel that purely empirical models still meet their needs.
way to forecast travel on transportation facilities across a
state in a manner that reflects current understanding of
travel behavior. MAJOR SOURCES OF INFORMATION ON
STATEWIDE TRAVEL FORECASTING MODELS
Only about half of the 50 states have created statewide There are few general sources of information on statewide or
models. Most of these models resemble urban transportation intercity passenger components; however, there have been
planning (UTP) models in structure. However, almost all two significant NCHRP studies on statewide freight model-
states with models have faced unusual challenges resulting ing. This section highlights important historical and recent
from the large sizes respective of their geographic areas and documents that have been useful to individuals or groups
the large amounts of data required to adequately describe building statewide travel forecasting models.
these areas. With few exceptions, several characteristics of
statewide planning demonstrate the need for distinguishing Appendix C is an excerpt from the literature review sec-
between statewide and urban models. tion of the Guidebook on Statewide Travel Forecasting
(Horowitz 1999) that concerns passenger and intercity travel
· Statewide models cover far more land area than urban forecasting. Appendix D is an annotated bibliography of the
models within the same state. statewide and national freight forecasting techniques. Refer-
· Statewide models cover far more facilities than urban ences to the literature found in this section are intended to up-
models within the same state. date these earlier literature reviews.
· Statewide models are often concerned with economic
developments that extend well beyond the borders of a Guidebook on Statewide Travel Forecasting
region, such as national and international trade issues 1999
and trends.
· There is less experience with statewide models than ur- The Guidebook (Horowitz 1999) was the last major reference
ban models. that covered both passenger and freight components of
· There is less research on intercity travel patterns than statewide models. This resource contains extensive advice on
on urban travel patterns. individual steps within the models, network preparation, and
· Statewide models must incorporate long distance, mul- data sources. A comprehensive literature review and several
tiday trips. short case studies are included in an appendix. One chapter is
· Statewide freight components require recognition of devoted entirely to time series methods such as BoxJenkins
many modes, whereas most urban freight components techniques.
only focus on trucks.
· Software products do not address the special needs of The Guidebook emphasizes three- or four-step modeling
statewide models. approaches. Details are given on how urban transportation mod-
· The legal impetus for statewide models is insufficient eling software packages could be adapted for statewide models.
when compared with metropolitan planning organization It recommends that freight forecasting be commodity-based,
(MPO) models. although there was some treatment of truck-only models.
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The Guidebook does not include discussions of two completed by many of the representatives. States reporting on
emerging topics: tour-based passenger components and com- their models were Florida, Indiana, Kentucky, Louisiana,
bining freight and passenger components with a built-in eco- Massachusetts, Missouri, New Hampshire, New Jersey, Ohio,
nomic activity component. Oregon, Virginia, and Wisconsin. The proceedings of the Peer
Exchange have been published by TRB as Transportation
Research Circular E-C075.
Transportation Research Circular E-C011:
Statewide Travel Demand Forecasting
(Conference Proceedings) 1999 Presentations at the 2004 Annual Meeting of the
Transportation Research Board, Session on
This specialty conference, roughly coinciding time-wise Statewide Travel Forecasting Models
with the publication of the Guidebook, heard reports from
several states about their existing statewide models and plans This session involved presentations by six authors on new
for new statewide models. Breakout sessions also provided developments in statewide travel forecasting models.
research recommendations. Presentations were made by rep-
resentatives from California, Florida, Indiana, Kentucky, · Ohio Statewide Travel Demand Forecasting Model
Michigan, New Hampshire, New Jersey, Oregon. Rhode · An update on the Transportation and Land Use Model
Island, Washington, and Wisconsin. Information Project (TLUMIP) in Oregon
· Wisconsin Statewide Model
· Statewide Modeling: The New Frontier
NCHRP Report 260: Application of Statewide · The Trouble with Intercity Travel Demand Models
Freight Demand Forecasting Techniques 1983
· A Brief Synthesis of the State of the Practice in Statewide
This report (Memmott 1983) provided a methodology for Travel Forecasting.
building a freight component for a statewide model. The re-
port recommended a commodity-based approach and sug- The PowerPoint slides can be found on the Statewide
gested that commodity distribution be performed by a gravity Travel Forecasting website: http://www.uwm.edu/~horowitz/
expression. An all-or-nothing mode-split step was proposed. statewide.html.
Modal costs were to be determined with the help of regulated
tariffs then in effect. The location of commodity consumption On-Line Documents About Statewide Travel
was to be determined by an inputoutput (IO) model. Forecasting Models
Numerous states or their consultants have web pages that
NCHRP Report 8-43, Methods for Forecasting contain documents about their statewide travel forecasting
Statewide Freight Movements and Related
Performances 2005 models. These web pages are volatile, and a fresh web search
is required to find the most current information. Here are a
This draft report (Cambridge Systematics, Inc., et al. 2005) few web pages that were active at the time of this report.
is a comprehensive reference on the current state of the prac-
tice in statewide freight forecasting models. It describes sev- · Florida Statewide Freight Model: webservices.
eral approaches to model building, depending on project camsys.com/freightmodel/freightmodel.htm.
needs and data availability, including the direct facility flow · Vermont Statewide Model: http://www.aot.state.vt.us/
factoring method, origindestination (OD) factoring method, planning/TDModel.htm.
truck model, four-step commodity model, and economic ac- · Virginia Statewide Model: http://www.wilbursmith.com/
tivity model. Ten case studies of freight components are pre- vdotmodel/howandwhen.html.
sented: Minnesota Trunk Highway 10 truck trips, Florida · Virginia Statewide Freight Model: http://www.wilbur
ports, Ohio's interim freight component, FHWA's Freight smith.com/vdotmodel/attachments/082902/Freight%
Analysis Framework (FAF), New Jersey truck trip table, 20Report%20(Draft%2008-20-02).pdf.
Southern California Association of Governments heavy-duty · Ohio Statewide Model: http://www.dot.state.oh.us/
trucks, Indiana commodity transport, Florida statewide urban/AboutUs/Statewide.htm.
freight, Cross-Cascades Corridor Analysis Project, and Ore- · Connecticut Statewide Model: http://www.ct.gov/dot/
gon combined passenger and freight. cwp/view.asp?a=1383&q=259806.
· Oregon Statewide Model: http://www.oregon.gov/
ODOT/TD/TP/TMR.shtml.
Statewide Travel Demand Models Peer Exchange
2004
Quick Response Freight Manual 1996
The attendees of the Peer Exchange (Longboat Key, Florida,
September 2324, 2004) included representatives from 14 Although not specifically for statewide models, the Quick
states and consultants who reported on their statewide model- Response Freight Manual (QRFM) (Cambridge Systematics,
ing efforts. The proceedings are distilled from a questionnaire Inc., et al. 1996) (Travel Model Improvement Program,
