Calibration

Formatting Volume Data

 

After each simulation two files (.mer and .att) are generated. They can both be opened with Excel. The “.mer” file is a detailed record of every vehicles in the simulation. For this example, the “.att” file will be used.

  1. Locate the “.att” file in the Evaluation output directory defined in the previous section.

    • It will have the same name as your project, followed by the simulation number (001) and “Data Collection Measurements”

  2. If the file does not open with Excel by default, Right Click and select “Open with…” and choose Excel

  3. Once the file is open, locate the row with the text “$DATACOLLECTIONMEASUREMENT” (see Figure below)

  4. Delete all previous rows

  5. Select the entire “Column A” by moving your cursor and Clicking next to the letter “A” in the column header

  6. From the top Ribbon Select “Data” and “Text to Columns"

 
 

  1. A new “Convert Text to Columns Wizard” window will appear (see Figure below)

  2. Select “Delimited”

  3. Click Next

  4. Only Check the “Semicolon” box

  5. Click Finish

 
 

After adjusting column widths, the data should look similar to the “Data Collection Measurement” window in Vissim (see Figure below)

 
 

  1. Delete unnecessary columns like $DATA and DATACOLLECTIONPOINTS.

  2. Delete VEHS columns that have volumes for LAST, TOTAL, AVG

    • VEHS(CURRENT,1,ALL) should be the first column with vehicles volumes and VEHS(CURRENT,36,ALL) should be the last

  3. Rename the station numbers under the NAME column to only contain 6 digits

    • Format these cells to a number without decimal places and uncheck the box “Use 1000 Separator (,)”

  4. Select the remaining data (Ctrl + A)

  5. Copy (Ctrl +C)

  6. In columns “A”, select a row below the existing data (example: row 10)

  7. Right Click in that row and select the Paste Option to “Transpose” (see Figure below)

  8. Delete the original rows of data

 
 

  • Rename the NAME columns header with “Time Stamp”

  • Replace the 36 - VEHS(CURRENT,#,ALL) cells with the 5 minute time intervals from the PeMS spreadsheet

GEH Formula

The following GEH (Geoffrey E. Havers) equation is the required method of determining an “Acceptable fit” for the project. It requires the vehicles per hour (vph) from the VISSIM simulation (m) and the volumes (c) from PeMS. As the Figure below indicates, GEH < 5.0 is acceptable. At least 85% of all freeway links (Mainlines, Off-Ramps and On-Ramps) must meet the criteria of GEH < 5.0.

 
 

The Figure below illustrates an example of GEH calculations using excel. The “GEH” column contains the required formula.

=SQRT((2*(D2-C2)^2)/(D2+C2))

 
 

The Figure below shows a formula for determining the percentage (passing rate) of acceptable GEH values per station. Divided the number of GEH values below 5.0 by the total number of time intervals (36). This value should be greater than 0.85 or 85%.

=(COUNTIF(F2:F37,"<5"))/36

 
 
WARNING: Do not forget to use Hourly Flow values for the GEH calculations otherwise your passing rates will be artificially high.

The Figure below shows a line chart that compares Observed traffic volumes (PeMS) and Simulation volumes (Vissim). Note that lower GEH values will cause both lines to mimic and overlap.