Embedded Files
The purpose of a site impact study is to quantify the traffic impacts of land use developments. These developments are typically limited to a small number of zones and the analysis involves conducting a link-level comparison of the model results.
There are two major challenges with using SERPM 8 for this type of analysis:
- A full rerun of the population synthesizer (PopSyn) may result in changes outside the study area
- The default sampling rate of the model (25%) may lead to link level results inconsistent with input changes on a small number of zones.
A solution developed under SERPM 7 and integrated into SERPM 8 involves the following major steps:
- Manage synthetic population changes
- Develop site impact scenario synthetic population (requires full run of PopSyn).
- Assemble a synthetic population utilizing the base population for all except the impacted zones. Insert population and households from the impacted zones from the site impact scenario synthetic population.
- Design and apply a sampling rate such that the impacted zones are sampled at 100% with sample rates in other zones negatively correlated to the highway distance from the impacted zones
Preparing for a site impact study in SERPM 8
Preparing for a site impact study in SERPM 8
The modeler should first generate a synthetic population and prepare the updated MAZ layer (see Land Use for guidance on preparing these inputs). The zones changed due to the site impact need to be recorded in a CSV file listing zones (by Regional TAZ) and a comment (an example file is provided in the model Inputs\SEData\example_devSiteTAZList.csv).
Open the model, select the base scenario (i.e. the scenario most similar to the site impact study) and navigate to the Utilities->Site Impact Study Preparation application group
Generate integrated site impact synthetic population
Generate integrated site impact synthetic population
- Double click the first Pilot program to create a site impact population.
- First, select the Household and Persons file from the BASE scenario
- Next, select the Household and Persons file from the Site Impact scenario
- Finally, select the file containing the list of TAZs that are included in the site impact study area
- The program will generate the integrated synthetic population files as hhFile_SI_all.csv and personFile_SI_all.csv in the inputs\SEData folder. The SI_all suffix indicates that these synthetic population files are the site impact (SI) population with all records included. The next step will select a sample of the synthetic population according to the distance to the site impact zones.
Set geographic sampling rate (to be done for both the Base and Site Impact scenarios)
Set geographic sampling rate (to be done for both the Base and Site Impact scenarios)
- Double click the Matrix program to export zone-zone distances (see Note 2).
- Double click the second Pilot program to produce a sampled population dataset.
- First, select the Household and Persons file developed from the previous step (hhFile_SI_all.csv, personFile_SI_all.csv)
- Next, select the MAZ data file with the updated households and employment
- Next, select the file containing the list of TAZs that are included in the site impact study area
- The program will generate in the SEData\Inputs folder
- the sampled synthetic population files as hhFile_SI_smp.csv and personFile_SI_smp.csv
- the MAZ data file with sample rate recorded as maz_data_SI_smp.csv
- an image of the sampled zones as SamplingRate.png
Notes:
- The geographic sampling by distance is set in the SEData\Inputs\samplingCutoff.csv file.
- The base scenario AM seed skim is used for zone to zone distances.
Create scenario for the site impact study
Create scenario for the site impact study
If you haven't already, create a new scenario as a child to the base scenario (i.e. the scenario most similar to the site impact study). The following keys must be updated:
- Under Land Use Inputs, update all three keys to point to the new MAZ data file and synthetic population files generated in the above step.
- Under System Configuration->Activity-Based Model Controls select 1 under the Apply Geographic Sampling key
Troubleshooting
Troubleshooting
- Confirm that the TAZ list file is properly formatted (TAZ, comment).
- See the _logs\site_impact_log.txt file for a report of any errors running the procedure.
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