The Miasma Beach Transportation Model -- Traffic Assignment

Assign the estimated O-D matrix via User Equilibrium Assignment (UE). After an initial All-or-Nothing (A-o-N) Trip Assignment is made on initial minimum paths, the solution procedure iteratively applies (a) link performance functions to update travel times, (b) a minimum path algorithm, and (c) an All-or-Nothing (A-o-N) Assignment. A line search using the current and prior assignments is then used to find the next set of network flows.

Begin by setting "Highway/Streets" as the active map layer and select: Planning / Single Class Traffic Assignment / Traffic Assignment

• At the Traffic Assignment dialog box, verify/select the following:

• Line layer: Highways/Streets
• Network file: mb2005.net (for example)
• Delay Function: Bureau of Public Roads (BPR)
• Method: User Equilibrium
• Matrix File: OD_FINAL (e.g., final matrix for period vehicle-trips)
• Matrix: OD

• Under Fields:

• Time: *AB_Travel_Time/BA_Travel_Time
• Capacity: *AB_Capacity/BA_Capacity
• Alpha: None
• Beta: None
• Preload: None

• Under Values:

• Alpha: 0.15
• Beta: 4.0

• Under Settings:

• Iterations: 50
• Relative Gap: 0.1 (Best would be 0.0001 or 0.00001)

• Next, click on the Options button; in the Options dialog box, enter:

• Check the first box, Create Themes. You can leave the options unaltered.
• Under Other options, check Do Tabulation
• Under Critical Link Analysis Setting, for Analyses: None
• Leave the other fields in their defaults

After returning to the Traffic Assignment box, click OK. Under the Output File Settings dialog box, be sure to set you base folder to your working directory (note: only check the "Overwrite All Files" button if you wish to overwrite previously created files).

• Rename the Output Files:

• Flow Table => tassign.bin [file type is Table]
• Flow Matrix => flow.mtx [file type: Matrix]
• VOC Matrix => VOC.mtx [file type: Matrix]

• After the procedure is executed, three types of outputs are opened:

• Flow range matrix
• V/C range matrix
• Highways/Streets + TASSIGN dataview

In the Results Summary dialog box, click on Show Report to open a text file report.xml. The Results Settings box can be closed. Examine the contents of each report (don't close these output windows yet).