Health Assessment Model
What Does It Do?
The Health Assessment Model is used to analyze health outcomes for a community based on a variety of demographic and built environment characteristics. With the Health Assessment Model, users can explore health outcomes based on existing conditions within their study area. In addition to baseline analyses, the Health Assessment Model can also respond to the core scenario functionality of Envision Tomorrow to test how land use and demographic shifts may impact health outcomes.
Who Created It?
The Health Assessment Model was developed by Urban Design 4 Health (UD4H), a research and consulting firm that specializes in applied research on the interactions between land use, transportation, air quality, climate change, and public health. UD4H’s mission is to support clients with innovative tools to realize health promotion, environmental, economic, and quality of life goals that are intrinsic in efforts to build new communities and to retrofit existing ones.
UD4H are the developers of both the tool architecture and the underlying statistical models that are used to estimate health outcomes. UD4H partnered with Fregonese Associates to integrate the Health Assessment Model into the Envision Tomorrow suite of planning tools.
How Does It Work?
The Envision Tomorrow Health Assessment Model is an analysis module component of the Envision Tomorrow suite of planning tools. It exists separately from the core scenario painting functionality of Envision Tomorrow, but is included in the core installation files that users can access at www.EnvisionTomorrow.org/downloads.
The tool works within ArcGIS for desktop but performs most of its statistical analysis via a cloud-based API. In addition to a valid installation of Envision Tomorrow, ArcGIS for Desktop (Basic) is required as well as a live internet connection. As inputs, users provide the tool with a relevant census block group featureclass in ArcGIS which should contain all the input variables needed to run the Health Assessment Model. Once that user has specified the location of this featureclass, the ArcGIS-based user interface sends information to the API which then returns the results in the form of a new block group featureclass. The results can be visualized both spatially at the block group level or at the study-area level in an associated Health Assessment Model Spreadsheet.
The following provides an overview of the separate model components and inputs needed to operate the Envision Tomorrow Health Assessment Model.
Understanding the Inputs
The basic input required to run the Health Assessment Model is a census block group featureclass with a valid GEOID field. GEOIDs are census-designated unique identifiers for census block group geographies. The block group features you use must be contained within a file geodatabase and should utilize geographic boundaries from the 2010 census. For baseline analyses, it is recommended that users use a subset of EPA’s Smart Location Database, though census block groups from any valid source such as TIGER/LINE products will suffice. For more information about the Smart Location Database visit: https://www.epa.gov/smartgrowth/smart-location-mapping.
In order to run a baseline analysis, users must only submit a valid census block group featureclass as described above with a GEOID. If an alternative scenario outcome is desired, other preparatory steps need to first be taken using other tools in the Envision Tomorrow suite. Steps for that process are covered in the “Creating Scenario Alternatives” section of this guide.
Accessing the Tool
To access the Envision Tomorrow Health Assessment Model, browse to the file menu in the Envision Paint Tools window. Then select the “Analysis Tools” fly out menu and select “Health Assessment Model App”. Once selected, the Health Assessment Model user interface will appear.
The user interface contains 4 sections.
1. Scenario and Baseline Selection – this section allows the user to choose between running a “baseline” aka “existing conditions” analysis or any one of up to five alternative scenarios.
2. Census Block Group Selection – the drop down menu prompts users to select a census block group featureclass from within their map document. Note: the geodatabase in which this feature is contained will be the default work space for any model outputs.
3. Health Assessment Model Spreadsheet File Path – user must specify location of Envision Tomorrow Health Assessment Model Spreadsheet
4. E-Mail – user account registration for model run. This e-mail will be sent to the API for verification. Default is email@example.com. At this time, it is not necessary for users to change this value.
Health Assessment Model Excel File
The Health Assessment Model Excel File is a macro-enabled Microsoft Excel workbook (.XLSM) where summarized results of a user’s Health Assessment Model runs are summarized and compared with one another. The excel file contains a three tabs: “Quick Start Guide,” “EPAP Outputs,” and “Summary.” The Quick Start Guide contains a basic overview of the model and provides basic field name and color definitions. The EPAP Outputs tab is where outputs from the model are summarized and written from the GIS-based tool. The Summary tab contains a number of relevant tables and figures that are automatically populated when a user runs the tool. The excel file can be downloaded here: www.EnvisionTomorrow.org/downloads.
The following provides a step-by-step guide for using the Envision Tomorrow Health Impact Tool. This guide assumes a basic knowledge of ArcGIS and prior experience with the Envision Tomorrow GIS Painting Tool. If you require more information about the basic setup and installation of Envision Tomorrow, please visit www.EnvisionTomorrow.org/user-guide.
A “baseline” or “existing conditions” analysis can be run by selecting “existing conditions” in user interface section #1 and by selecting a valid census block group featureclass from the map document in user interface section #2. The census block group featureclass that is selected must have a GEOID field. It is recommended that the Smart Location Database (referenced above) be used as the input for any baseline analysis but any featureclass with a valid GEOID can be used. Users can also run the analysis on a selection of features within a featureclass by selecting a subset of features before running the tool. If the user has made a feature selection, only selected features will be processed as part of the baseline analysis.
- Step 1: Scenario/Baseline Selection: Select the “existing conditions” radio button
- Step 2: Input Features: Select a census block group featureclass from the map document
- Step 3: Excel File: Specify the file path for the Health Assessment Model Excel File
- Step 4: Model Run: Click “Run”
The tool will return a new census block group featureclass that includes both input and output variables for the Health Impact Assessment model. The default workspace for this featureclass is the same as the input blockgroup featureclass. The tool will also summarize and export study area average values to the Health Impact Assessment Excel workbook.
Alternative Scenario Analysis
It is possible to produce alternative health outcomes using parcel-based Envision Tomorrow land use scenarios as an input to the Health Assessment Model. In order to develop alternative scenarios, users must go through a series of additional steps, including the development of parcel-based Envision Tomorrow land use scenarios. For a detailed guide to creating Envision Tomorrow land use scenarios, visit www.EnvisionTomorrow.org/user-guide.
In addition to preparing Envision Tomorrow land use scenarios, users must ensure they track relevant input variables. Through its core set of indicators, Envision Tomorrow is able to produce many of the same input variables that are used by the Health Assessment Model. These must be tracked through the Envision Tomorrow Attribute Field Manager and then aggregated to their respective census block groups using the Envision Tomorrow Scenario Aggregator. For reference, the relevant fields that Envision Tomorrow can produce as inputs for the model are listed below:
- totpop2010 - 2010 Census total population
- tothhs2010 - 2010 Census total households
- totemp2010 - 2010 Census total employees, work location
- totwrk2010 - 2010 Census total workers, home location
- popdens_ac - Gross population density in terms of people per acre on unprotected land
- empdens_ac - Gross employment density in terms of workers per acre on unprotected land
- retailempl - Retail jobs within 5-tier employment classification scheme
- empentropy - Employment entropy index using 5-tier employment classification scheme
- intrsndens - Street intersection density, weighted, auto-oriented intersections eliminated
- avg_hhsize - Average household size
- pct_lowinc - Percent of households classified as low income, $0-$35k
- pct_medinc - Percent of households classified as middle income, $35k-$100k
- pct_higinc - Percent of households classified as high income, $100k+
The overall workflow for pre-processing an alternative scenario model run is depicted in the figure below:
Step 1: Attribute Field Manager
Once the user has an Envision Tomorrow scenario they would like to test, they must turn on relevant input variables using the Attribute Field Manager. The Attribute Field Manager is a tool that allows users to track and write any of ET’s indicators to individual scenario polygons. The Attribute Field Manager can be access through the ET File Menu as shown in the figure below:
Once activated, the user is prompted to select a range of ET indicators for tracking. For ease of use, a quick reference field grouping options has been created specifically for the Health Impact Model. Simply select “Public Health” and then click “Apply” and all the relevant fields will be tracked.
Step 2: Attribute Synchronization
In order to ensure that all attributes are correctly synchronized with your scenario, perform a “full sync”. This will ensure that new values are written to the featureclass correctly, and that any old values are removed.
Step 3: Scenario Aggregation
Users will need to use the Envision Tomorrow Scenario Aggregator in order to translate their parcel-based land use scenario to census block groups. The Scenario Aggregator can be accessed via the ET File Menu as shown below:
Once activated, the user is then prompted to select a “neighborhood layer.” The neighborhood layer should be the census block group featureclass that you wish to run through the Health Assessment Model. Using the drop-down menu, select the relevant block group featureclass from the map document.
The user is then prompted to choose which variables to track. Select variables by selecting the check box in the “Track” column. For the Health Assessment Model, it is important that all input fields follow the correct naming convention. Refer to the following cross-walk table for Health Assessment Model variable names and how they correspond to default Envision Tomorrow outputs then re-name them as appropriate in the “Total Field Name” column*.
|ET Default Variable Name||Health Assessment Model Variable Name|
* Note: it is acceptable for the input census block group featureclass to contain fields which do not match the Health Assessment Model schema. Any fields not required by the model will be excluded from the analysis when the model is run.
Before running the Envision Tomorrow Scenario Aggregator, ensure that you have made the same selections as appear in the figure below.
As it runs, the Scenario Aggregator will append the relevant fields as named in the “Total Field Name” column to your input block group featureclass. Once complete, users will use this augmented featureclass as an input to the Health Assessment Model.
Step 4: Run Model with Scenario Alternatives.
Similar to the baseline analysis process described above, the augmented block group featureclass resulting from the Scenario Aggregator run can now be used as an input for the Health Assessment Model. Use the ET file menu to initialize the Health Assessment Model user interface.
Step 5: Scenario/Baseline Selection
Select the “scenario” radio button and using the drop down menu, select the appropriate scenario to which to write your results. This distinction is made in order to distinguish which scenario column will be used in the Health Assessment Model Excel file and how output features are named. If results for a given scenario already exist within the output workspace or workbook, they will be overwritten.
Step 6: Input Features
Select the census block group featureclass produced by the Scenario Aggregator from the map document
Step 7: Excel File
Specify the file path for the Health Assessment Model Excel File
Step 8: Model Run