The National Academies Press

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From page 12... ... South Dakota has pursued an interesting variation on trend–trend line forecasting that seems to embody principles of behavioral travel forecasting. STATES WITH STATEWIDE MODELING CAPABILITY Unlike MPO models, which are often permanent components of the UTP process and get incremental upgrades, statewide models go through a life cycle. Read the entire page →
From page 13... ... Figure 1 provides an additional overview of the status as of spring 2005, as well as a rough estimate of the cost of model development and, in a few cases, the amount of time allowed for model development. 14 RATIONALE FOR STATEWIDE MODELS Dynamics of Modeling Process Responses to the synthesis and Peer Exchange questionnaires revealed that the statewide modeling process is dynamic. Read the entire page →
From page 14... ... ■■■ Operational Dormant Developing Revising Partial FIGURE 1 Status of statewide travel forecasting models, Spring 2005. Environmental and Planning Factors Desired Spatial Detail Anticipated Projects Goals and Objectives Outreach to Decision Makers Model Development Funding Applications to Plans and Projects State-of-theArt/Practice Statewide Travel Forecasting Model Secondary Data Sources Primary Data Sources Staff and Consultant Training FIGURE 2 Typical statewide model development process. Read the entire page →
From page 15... ... . The model was also used to produce future year growth factors to forecast future traffic volumes in a statewide interchange assessment study. Read the entire page →
From page 16... ... Intermodal terminals, major seaports, and rail yards are included as special generators. The model will be used to analyze and evaluate conditions and performance of passenger and freight transportation under different scenarios, which will lead to the prioritization of proposed projects for SIS planning analysis (H. Read the entire page →
From page 17... ... urban area models with our statewide model. • The statewide model has two components: a passenger model and a freight model. Read the entire page →
From page 18... ... Selected states will deliver their models to outside agencies or universities on request, although with conditions. For example, Texas asks borrowers to sign a confidentiality agreement, Kentucky requests that borrowers sign an agreement as to acceptable use of the model, Wisconsin has procedures by which it will allow the use of its model and the modeling software by outside parties, and Michigan only distributes trip tables and networks. Read the entire page →
From page 19... ... Example of the Use of Geographic Information Systems In Louisiana, the statewide model network was developed based on several existing DOT legacy databases including: • Louisiana Road GIS file in Geomedia format; • Surface Type log file, a Microsoft Access database containing mile post and key roadway attributes; and • Highway Needs Inventory Summary log file, another Microsoft Access database, containing mile post and additional roadway attributes, roadway conditions, and future needs information. Substantial resources were devoted by the model development consultant Wilbur Smith Associates (WSA) Read the entire page →
From page 20... ... Yoder, personal communication, 2005, and Wilbur Smith Associates 2004) Read the entire page →
From page 21... ... With a few exceptions, passenger components look much like urban travel forecasting models in structure; containing the four major steps of trip generation, trip distribution, model spit, and trip assignment. Oregon's model and Ohio's new model (see chapter three) Read the entire page →
From page 22... ... For out-of-state highway networks, Florida and Trend Analysis OD Table Estimation & Assignment Freight Only PassengerOnly Combined Passenger & Freight Integrated Passenger, Freight & Economic Activity Individual Link ADT Freight or Passenger Volumes Across State Inputs to Traffic Operational Analysis Details of Freight and Passenger Volumes Transport Effect on Economic Development Generic Structures G en er al iz ed O ut pu ts FIGURE 4 Generic model structures and their potential outputs. Read the entire page →
From page 23... ... , trip purposes, special generators, time of day, and modes. MODAL CHOICE All states with passenger components have at least the passenger automobile as a mode. Read the entire page →
From page 24... ... Traffic microsimulation was being explored as a possibility in Ohio and Oregon, but consideration of dynamic traffic assignment has not been reported for any statewide model. Zone Systems All statewide models have zone systems for organizing spatial information on a network. Read the entire page →
From page 25... ... Ohio and Oregon have integrated land use and economic activity components, which encompass the functionality of trip generation, trip distribution, and mode split. Ohio implemented OD table estimation from traffic counts within its interim model. Read the entire page →
From page 26... ... ■■ Tour-based multinomial destination choice model (1) ■ Those statewide models that are considered multimodal require a mode split step. Read the entire page →
From page 27... ... Finding the effects of freight on the transportation system requires that commodity flows be converted to trucks, rail cars, shiploads, aircraft, barges, or containers. Read the entire page →
From page 28... ... For example, Florida used these techniques only for non-freight truck trips. If a model is commodity-based, it is likely that states would need data on commodity flows for calibrating their trip generation and distribution steps. Read the entire page →
From page 29... ... All states reported using fixed shares, derived from the CFS, Reebie's TRANSEARCH database, expert judgment, or the VIUS. Traffic assignments usually involve the mixing of passenger and freight traffic. Read the entire page →
From page 30... ... ■■■■■■■■■■ Statewide and MPO models use similar computational steps, trip purposes, base-year, or modes to promote compatibility (7) ■■■■■■■ Statewide model shares GIS databases with MPO models (6) Read the entire page →
From page 31... ... A few states gave vague responses, such as "well," "acceptable," and "fair." Texas reported good comparisons between its freight component and flows from Reebie's database. California stated that 44% of the links meet the "maximum desirable deviation" standard and an R-square of 0.83 between link counts and base case link volumes. Read the entire page →

From page 12...

... South Dakota has pursued an interesting variation on trend–trend line forecasting that seems to embody principles of behavioral travel forecasting. STATES WITH STATEWIDE MODELING CAPABILITY Unlike MPO models, which are often permanent components of the UTP process and get incremental upgrades, statewide models go through a life cycle.