How to Create an Internal/External (IIEE) Analysis

This guide shows you how to easily create an Internal/External (IIEE) analysis using StreetLight InSight. This type of analysis allows you to calculate the share of trips in a Zone that are fully internal (II), fully external (EE), inbound (EI), or outbound (IE).

The process to create an IIEE analysis requires creating Zones representing the internal area and Zones for the trips entering and exiting the area, then creating O-D Analysis using those Zones. Afterward, the share values can be seen in the Interactive Visualization or by manipulating the Metrics in Excel (or a similar tool).

For this guide, we will use Parsippany-Troy Hills Township in Morristown, New Jersey as our example. With four major highways running through the town, external-external (EE), or “pass-through” trips comprise a large volume of the total trips in the area. StreetLight’s O-D  analysis will help to understand the share of pass through trips compared to fully internal trips, and can even be used to examine the share of external trips by each highway gateway. While this is a good example, an IIEE analysis can be done in any location.

Step 1: Create the Zones and Zone Sets

To create an Internal/External analysis you will need to create two Zone Sets. Learn more on how to create Zone Sets. 

When creating your two Zones Sets you will need one for your Internal Zones and one for your External Zones.

Internal Zones

For this Zone Set, you can either upload a shapefile or draw a zone. The Zone needs to meet these requirements:

  • It must cover the entire area of analysis
  • Polygon or Line: Polygon
  • Pass-through: No

Note: This tutorial covered the Parsippany-Troy Hills Township with a single internal Zone. However, it is also possible to create multiple contiguous internal zones, so long as as they collectively cover the entire area.

External Zones

For this Zone Set, create a “gate” Zone on each major ingress/egress road--preferably State Route or Interstate Highways to your region of analysis. If you are drawing the Zones, this is generally easier if you show the internal Zone set before drawing.

 

 

The key is to make sure you are capturing the majority of the traffic entering and exiting your region of analysis. After adding all of your gates, you should have a Zone Set that covers all of the access and exit routes for your entire region. The Zone Set needs to meet these requirements:

  • It must include Zones that represent each entrance or exit to the region of analysis. Keep each gateway Zone small.
  • Pass-through: Yes
  • Direction: Optional
  • Bi-directional: Yes (If adding a direction)

Note: There’s also an alternate configuration. One could create two External Zone Sets with direction on the Zones, but not bi-directionality: This means you will have one Zone Set for ingress and one Zone Set for egress. Learn more

Step 2: Create Project

The Project Type used for an IIEE analysis is an Origin-Destination (O-D) Analysis. Learn more on creating an O-D analysis. 

For this project set up, you will need to make both your internal and external Zone Sets your Origins and Destinations. In our example, we made both “Parsippany” and “Parsippany Gateways” as both Origin and Destinations. You can adjust your Travel Type and Data Source accordingly. If you are unsure about which Data Source to feel free to learn more

Finally, you can edit your day parts, day periods, and more before confirming your Project.

 

Pro Tip:  You can configure this Project using calibration to get estimated counts. Learn more about our Calibration Feature.

Step 3: Visualize

You can visualize your project in our Interactive Visualizations, learn more about our Interactive Visualizations. You can see that you will be able to visualize both your Zone Sets in the visualizations.

While the visualizations are useful, it can be easier to get information by working with the downloaded Metrics. This will help you get a better understanding of the full IIEE analysis.

Step 4: Further Analysis of the Metrics

4a. Once your Project is complete, download the Metrics and complete your IIEE analyses using Microsoft Excel. To download your Metrics, go to the “Manage Projects” section, and click on the “All Projects” tab. In the Actions Column, click the Download icon.

4b. Select which files you want to download. For IIEE, you must select the “O-D Metrics CSVs”. The other downloads are optional. Click “Download” once you’ve made your selection.

 

4c. Open the folder you downloaded and the CSVs and shapefiles you selected will be there. There will also be a README and Project files text.

4d. Create a new column (column R) named “Origin = Dest”. Trips identified with the same Pass-through Zone for the origin and destination need to be filtered out for accurate results. Copy and paste this code into cell R2 and copy the formula down for the entire column: =IF(D2="yes",IF(C2=H2,"yes","no"),"no")

4e. Create another new column (column S) named “Trip Type”. Set up filters on the whole worksheet by going to the “Data” tab, and click “Filter”. Then, filter columns D and I (which designate the Origin and Destination Zones as pass-through with “yes” and not pass through as “no”). Filter the columns so they are selected to just have no or yes. When doing this you can label each row as one of the four trip types: internal-internal (II), internal-external (IE), external-internal (EI), and external-external (EE).

  • Internal-internal: Origin and Destination Zones are not pass-through
  • Internal-external: Origin Zone is not pass through, Destination Zone is pass-through
  • External-internal: Origin Zone is pass through, Destination Zone is not pass-through
  • External-external: Origin and Destination zones are pass-through

4f. Once all rows are appropriately tagged with a trip type, select the entire worksheet again and create a pivot table. Filter by the fields shown.

If you have never worked with pivot tables before, here is an introduction to pivot tables by Microsoft.

Using the Trip Type as the Row Labels, the sum of the O-D Traffic (STL Index), and controlling the table via Day Types, Day Parts, and Origin=Dest is no, you can easily visualize the percentage of each type of trip with a table, or pie chart, or other graph. Using the PivotTable Fields, you can also look at other Metrics, such as the trip type percentages by Origin or Destination Zone.

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