Median Response · All Calls
—
Citywide
Median Response · Priority 1
—
Emergencies only
Daytime Response
—
6am – 6pm
Nighttime Response
—
6pm – 6am
Total 911 Calls
—
2022 police-dispatched
Census Tracts
—
Wayne County
Police Response Deserts
Mapping 911 Call Response Time Inequality Across Detroit Neighborhoods
Research Question
When you call 911, how quickly police arrive depends enormously on where you live. This project
uses real Detroit 911 call-for-service records with timestamps to calculate
actual median response times at the census tract level, maps the spatial inequality, and tests
whether response time correlates with race and income after controlling for call volume and
station proximity.
Methodology
- Downloaded 297,417 Detroit 911 police calls from 2022 via ArcGIS REST API
- Filtered to valid response times (0–240 minutes), retaining 281,725 calls
- Spatially joined call locations to 627 Wayne County census tracts (TIGER/Line)
- Aggregated by tract: median response, 90th percentile, day/night splits, call volume
- Joined ACS 2022 demographics: % non-white (B03002), median income (B19013)
- Computed distance from each tract centroid to nearest police precinct
- Ran OLS multivariate regression to test equity predictors
Regression Results
OLS regression: dependent variable = tract median Priority 1 response time (n=270 tracts)
| Variable |
Coefficient |
p-value |
Result |
| Distance to nearest precinct (km) |
+0.654 |
<0.001 |
★ Significant |
| Median household income |
−0.147 |
0.048 |
★ Significant |
| % Non-white population |
−0.142 |
0.068 |
Marginal (p<0.10) |
| Call volume per tract |
+0.029 |
0.693 |
Not significant |
| Population density |
−0.012 |
0.869 |
Not significant |
R² = 0.257 · Model explains 26% of variance in tract-level response times
Key finding: After controlling for distance to the nearest precinct (the strongest
operational predictor), lower-income tracts still receive statistically slower response
(p=0.048). The race coefficient trends in the same direction but falls just short of
conventional significance (p=0.068), consistent with partially income-mediated racial
disparities in service access.
About This Project
Built as a portfolio data project demonstrating spatial analysis, equity research methodology,
and full-stack GIS web development. All data is publicly available. Analysis code is available
in the repository's notebooks/ folder.
Data year: 2022 · City: Detroit, Michigan · Boundaries: Wayne County Census Tracts (TIGER 2020)