Iowa Statewide Freight Commodity Model

Parsons Brinckerhoff as Subconsultant to Iowa statewide model development under CDM Smith. The Federal Railroad Administration also participated on the freight modeling team.
Iowa Department of Transportation
Goals and Objectives: 

The purpose of this model is to update the 2007 Iowa Traffic Analysis Model (iTRAM) in order to evaluate freight and commodity movements.  For rail in particular, there is a need for commodity flow models to estimate available freight rail capacity for agricultural and industrial development needs. A future year (2040) will also be developed.


This includes disaggregation of Freight Analysis Framework rail commodity flows. Long distance rail passenger movements are also considered with rail freight movements.

Overview and Description: 

The first generation iTRAM (statewide traffic model) focused on car and truck traffic. The 2013-2014 updated model incorporates freight and commodity flows plus long distance passenger movements. The updated iTRAM model consists of three main parts, each comprised of multiple steps (see Figure 1):

Figure 1.


A)    Commodity Flow Processing (Truck, Rail, Water)

  1.     County Level Rail Freight Commodity Flow Tables
  2.     National Rail Network Assignment
  3.     Rail-Highway Freight Mode Choice
  4.     Detailed Iowa Rail Network and Assignment of Carload Waybill Commodity Flows
  5.     Estimation of Rail-Highway and Rail-Water Multimodal Commodity Flows

B)    Long Distance Person Travel (Air, Car, Rail, Bus)

  1.     Demand Person Development
  2.     Network and Time Skim Development
  3.     National Person Mode Split
  4.     Passenger Rail Boardings

C)    iTRAM Model

  1.     Local Truck Trips using Quick Response Method (i.e., Trip Generation and Trip Distribution)
  2.     Truck Trips from Commodities (from part A - Commodity Flow Processing)  and Local Truck Trips adjusted for double counting and pivoted off an origin destination matrix estimation-expanded trip table
  3.     Iowa Household Trips (i.e. Trip Production and Attraction Choice)
Spatial Detail: 

iTRAM consists of 1,951 Traffic Analysis Zones.

Disaggregation for Rail
Model documentation provides more detailed information on the rail component. The rail network includes Class I Railroads and the Iowa Interstate Railroads. The information provided focuses on the mapping of the waybill sample and disaggregation of FAF3 data to the county level. Mapping the waybill sample results in selected waybill records being assigned to the assignment network created from the Oak Ridge National Laboratory (ORNL) rail network database. Disaggregating the FAF3 data to the county level uses employment data and SCTG commodity information to balance FAF3 regional flows amongst counties. The mapping of the waybill sample provides annual base year rail commodity flow tables and the FAF3 disaggregation provides both base and future year commodity flow tables.

Mode Detail: 

Truck, Rail, Water, Multimodal

Commodity Detail: 

This model uses U.S. Commodity Flow 2007 based Standard Classification of Transported Goods (SCTG) categories.


•    Rail ownership changes
•    Alternatives analysis (i.e., new truck-rail intermodal or warehouse/distribution center location; short line railroad planning; rail)

System Platform: 

Windows 7

Data Sources: 

FAF3; Surface Transportation Board Confidential Rail Waybill; Oak Ridge National Laboratory rail network; 2007 Economic Census; Bureau of Economic Analysis; County Business Patterns; American Transportation Research Institute; Iowa DOT state rail network; existing Iowa DOT iTRAM (statewide model) components including road network, zonal socioeconomic data, and point information in freight related areas.

Example Inputs & Outputs: 

•    Input: observed flows; cost to ship commodity by mode per ton per mile; network skimmed and scaled distances
•    Output: freight flows by mode; freight rail assignment; truck trip tables

Software Information: 

Development work in INRO’s EMME software (matrix convolutions and operations); Rail commodity model and Graphical User Interface built in Caliper Corporation’s TransCAD software (Version 6.0).  Designed to interface with the existing Iowa state model products in TransCAD:
•    First Generation Traffic Model: Iowa Traffic Analysis Model (iTRAM), developed 2005-2007
•    Second Generation Statewide Model: iTRAM Freight Commodity Model, in progress (2012-2014)

User Manual/User Interface: 

TransCAD 6.0 Graphical User Interface (GUI) for ease in application work.

Website & Contact Information: 

Phillip J. Mescher, AICP, Project Manager
Office of Systems Planning
Iowa Department of Transportation

Ron Eash, Freight Model Lead
Parsons Brinckerhoff
230 W. Monroe Suite 900
Chicago, IL 60606
312-803-6662 (office)