Introduction to our Calibration Feature
For many transportation projects, one of the first questions asked is: “How many trips happen on a particular roadway or corridor?” Traffic counts are often available for large road segments, but they are not available for all of the roadways that transportation professionals want to analyze. We launched our Calibration Feature to help our users get estimate counts on all roads with StreetLight InSight.
The Calibration Feature utilizes additional data and analytics to scale StreetLight Index values to estimated counts. There are two options:
- “Single Factor with User-provided Counts ”: Uses user-provided and uploaded AADT (or similar counts) data for roads in or similar to your study area for calibration.
- “Single Factor with StreetLight AADT”: Uses our AADT values as your calibration data set.
No matter which option you choose, the Calibration Feature is an easy way to convert StreetLight InSight Index values into the industry-standard unit-estimated counts.
Calibrating our Metrics with your provided count data or AADT data is a feature available to all subscription levels.* The Calibration Feature can be used in the following Project Types: Zone Activity Analysis, O-D Analysis, O-D with Middle Filter, O-D to Preset Geography, and Segment Analysis. You may also use your bicycle or pedestrian count data to calibrate bicycle and pedestrian projects.
*If your subscription is from before January 1, 2019, it may not include the Single Factor with StreetLight AADT Calibration Type. Contact firstname.lastname@example.org if you would like to get access to this feature.
Here are a few important things to keep in mind when using the Calibration Feature:
- If, for example, you select all of 2017 for your Project’s Data Period, StreetLight InSight assumes that the calibration data represents all of 2017. If your calibration data is actually from 2015, you are making an implicit assumption that travel behavior in 2015 was the same as 2017 for these road segments.
- If you selected a data period that includes all of 2017, but your calibration data was only from January 2017, you’ve made an implicit assumption that all of 2017 was the same as the month of January.
- Data calibrated with StreetLight AADT from 2017 cannot be directly compared to data calibrated with StreetLight AADT from 2018.
- Note that the StreetLight AADT is calculated specifically for 2017 or 2018. For example, If are using StreetLight AADT from 2017 to calibrate, and you’re including data from other months or years other than 2017 in your Project, you’ll be making an implicit assumption that all of 2017 was the same as the data period you’ve selected.
Step 1: Zones and Zone Sets
To get estimated vehicle counts from a Project, start by creating a Calibration Zone Set. To do this, you can upload your own AADT, ADT, AWDT, or AAWDT information to the Calibration Zone Set using "Single Factor User-provided Counts," or if you do not have your own counts you can use "Single Factor with StreetLight AADT" for calibration. Using Single Factor calibration is different when using your own count data versus StreetLight AADT, so learn more on how to create a Calibration Zone Set.
Getting estimated bicycle or pedestrian counts largely follows the same process, except you will upload your own AADBT or AADPT data instead. Learn more about drawing calibration zones and adding bike/ped counts here.
- If you are calibrating with StreetLight's AADT, you will need to make sure your Calibration Zone Set uses Pass-through Zones and is marked as Bi-directional. Learn more on how to Calibrate with StreetLight's AADT.
- It is perfectly fine to have a Zone Set where some Zones have calibration data and some don’t. It’s also fine to have anywhere from one Zone to a hundred Zones when using “Single Factor User-provided Counts”. When using “Single Factor with StreetLight AADT,” we recommend using between seven and twenty zones for optimal results.
If you are calibrating with “Single Factor User-provided Counts” you will create a Zone Set that contains your count data, learn more on creating Calibrated Zone Sets. The guide below is an overview of the information you will need to use the Calibration Feature. This example calibrates with "Single Factor with User-provided Counts" and is based in Montgomery County, MD.
Calibrating with Single Factor User-provided Counts
Calibration Zones can be either polygons or lines, and they must always be Pass-through. When adding Calibration Data to your Zones you must include the following fields:
- Calibration Type: Choose whether your counts are AADT, ADT, AWDT, or AAWDT data.
- Calibration Value: Input your known counts.
- Personal Traffic Ratios, Commercial Medium Duty Traffic Ratios, and Commercial Heavy Duty Traffic Ratios: If you have information on the breakdown of traffic, you will input it here. If not, use our default settings.*
*This breakdown will only apply to Projects that use Navigation-GPS as a data source.
Pro Tip: Your Calibration Zone Set does not need to include the road or roads you are analyzing as Origin, Middle Filter or Destination Zones in your Project. Instead, you can calibrate using data for roads near and around your study area. Note that you will get the most accurate results by calibrating with data from roads that are as close as possible to your area of interest.
Step 2: Create Projects
If you’re creating a Zone Activity Analysis, O-D Analysis, O-D with Middle Filter, or O-D to Preset Geography Project in StreetLight InSight, then you can choose between three different types of calibration:
Descriptions of the Calibration Types
“None (StreetLight Index)”: Projects will run without calibration: Metrics will be provided as StreetLight Index values only. This is the default for all Project types.
“Single Factor with User-provided Counts”: StreetLight Index values will be scaled to estimated counts using Calibration Zone Sets that contain traffic count data. Both the StreetLight Index and the Calibrated Index will be included in the downloads.
This option is available for Projects with Location-Based Services with Pass-through and Navigation-GPS Data Sources.
“Single Factor with StreetLight AADT”: StreetLight Index values will be scaled to a “Calibrated Index”, or estimated counts, using StreetLight AADT. This option uses StreetLight InSight to calculate AADT for Pass-through Zones in your Calibration Zone Sets in order to scale the StreetLight Index to estimated counts. Both the StreetLight Index and the Calibrated Index will be included in the downloads.
- This option is available for Projects with Location-Based Services with Pass-through and Navigation-GPS Data Sources.
- This option is only available for Projects in the US.
- If your subscription is from before January 1, 2019, you may or may not have access to this Calibration Type.
2a. When you are calibrating, while setting up your project you will need to add your calibrated Zone Set to the “Selected Calibration Zone Set(s)” box.
Note: If your Calibrated Zone Set is a unique Zone Set from the one you are analyzing in your Project, then these Zones will not go towards your total unique Zone Count.
2b. If you used "Single Factor with StreetLight AADT" you will need to pick your "Calibration data Period." Click "Edit" to choose your data period.
2c. Pick either AADT 2018 or AADT 2017 for your "Calibration Data Period."
Note: For best results, pick the year from the"Calibration Data Period" that is closer to the Data Period you are analyzing. For example, if you are analyzing data from 2016, calibrate with AADT 2017 data.
Step 3: Visualize
When using Interactive Visualizations to analyze calibrated Projects, you can choose to view either the StreetLight Index, Percentages, or the Calibrated Index. The “Calibrated Index” are estimated counts. Learn more about our Interactive Visualizations.
Step 4: Further Analysis of the Metrics
4a. Download your Metrics. Learn more about downloading.
A few items in your downloaded Metrics will be different from Projects that are run without the Calibration Feature:
- First, you will see an additional .csv called “Your Project_calibration_Zones.” This file includes the data you entered for each Calibration Zone. In addition, this .csv indicates the Calibration Zones that are outliers and were therefore excluded from the average calibration factor. (In the column “Personal Calibration - Is Excluded Zone,” a Y value indicates the value was excluded as an outlier). In our example, no Zones were excluded.
- For each zone_traffic and od_traffic file, you will see new columns that include the Calibrated Index. As shown in the image, the column header (Zone Traffic, Origin Traffic, Destination Traffic, etc.) will be repeated. The second time it will be followed by “(Calibrated Index)”. This indicates that the StreetLight Index value was calibrated to estimate actual trip counts for the time period stated.
4b. Create a pivot table. Learn more on creating pivot tables.