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Frequently Asked Questions
What is TRAP (Traffic-Related Air Pollution)?
TRAP is a screening index based on proximity to roads, weighted by estimated traffic volume (AADT).
Higher values indicate greater potential exposure to vehicle emissions. This is a relative index, not an absolute health risk measurement.
What is Raw vs Net Air Pollution?
Raw: TRAP exposure based only on road proximity and traffic volume.
Net: Raw TRAP minus a tree canopy mitigation factor (trees absorb pollutants). Net values can be lower where tree cover is high.
What is the Urban Heat Island (UHI) Index?
The Urban Heat Island (UHI) Index estimates relative heat exposure based on land cover classification (ESA WorldCover), NOT measured temperatures.
Impervious surfaces (roads, buildings) score higher; tree canopy scores lower. It indicates potential heat exposure, not actual temperature.
What do FEMA flood zones mean?
100-year zone: 1% annual chance of flooding (Zone AE).
500-year zone: 0.2% annual chance (Zone X shaded).
Red overlay shows where school property parcels intersect flood zones.
Are these absolute risk assessments?
No. All indices are comparative screening tools for identifying areas of potential concern.
They should not be interpreted as definitive health or safety risk levels. Professional assessments require site-specific data collection.
Urban Heat Island (Index)
Cool → Hot
Land-cover proxy, NOT measured temperature