5- 5
- The method does not perform trip distribution, traffic assignment, or mode split. These
decisions have to be made using professional judgment.
Travel Demand Model
The North Carolina Department of Transportation developed Triangle Regional Model ( TRM),
uses TransCAD and predicts traffic volumes for the Triangle Region based on socioeconomic
data and several different production and attraction models that vary by urban/ rural locations.
While the TRM is a complete travel demand model and performs all aspects of the 4- step process
( Trip Generation, Distribution, Mode Split, and Traffic Assignment) this project focuses
primarily on the Trip Generation portion of the model. Figure 5- 3- 3 shows the trip generation
procedure used by the Triangle Regional Model.
Figure 5- 3: TRM Trip Generation Method
Steps 1 through 3 involve separating the total number of households in the zone into categories
based on size and income. This procedure was developed using the results from the Triangle
Step 1: Input Socioeconomic Data for the Southern Village and Lake Hogan Farms
zones into TransCAD Triangle Regional Model.
Step 2: Disaggregate Households into Household Size by Income Matrix
Step 3: Use Fratar Model to Balance Household Size by Income Matrix
Step 4: Multiply Production Cross- Classification Matrix For Each Trip Type by
Household Size by Income Matrix to Find Productions by Trip Type for Study Area
Step 5: Use Attraction Regression Equations to Find Attractions Using
employment and Total Dwelling Units
Step 7: Balance Productions and Attractions holding Productions Constant Except
NHB Trips
Step 6: Verify Work Trips