Methodology & Sources

About 311info

311info publishes 311 service request counts from 32 cities in the US and Canada.Each city page reports total requests, monthly volume, and per-category breakdowns derived from that city’s open data portal. 311info is an independent project and is not affiliated with any government agency. The site, including its service category mappings and data pipeline, was built with the assistance of Claude (Anthropic).

About 311

311 is the non-emergency service request system used by most North American cities for issues such as potholes, noise complaints, illegal parking, sanitation, and graffiti. Residents file requests by phone, mobile app, or web form. Each request is published as a row in the city’s open dataset with a category, a location, and a creation timestamp.

Data sources

Data is pulled directly from each city’s open data portal (Socrata, ArcGIS, CKAN, Carto, OpenDataSoft). Fields are normalized across portal types for cross-city comparisons. No third-party aggregators are used. Each city page links to the underlying dataset on the city’s portal.

Update frequency

Data is updated on the 2nd of each month, covering the previous calendar month. Each city page shows its exact data coverage window; the “Data through” stamp in each page header reflects the most recent record in the dataset.

Computation

Every count on this site is a row count over a filter:

• Total requests is the count of every 311 row the city has published within the coverage window.
• Monthly volume groups those rows by the month the request was created in the city’s local time.
• Per-category counts use an AI-generated mapping from each city’s raw service-type string to a normalized cross-city category (e.g. Noise, Potholes & Roads, Trash & Recycling, Graffiti). Requests whose raw type does not match any known category fall into other.
• Resolution time and closure rate are only displayed when the underlying sample meets a quality threshold: at least 5,000 requests with a real closed-date timestamp AND at least 50% of the city’s requests containing resolution data. Cities that do not publish reliable close-dates have these metrics hidden.

Service category mapping → Full table of how raw service types map to normalized categories. CSV download available.

Noise map methodology

Each city’s noise map (linked from its city page) shows complaint density as a heatmap. Tapping any block or searching an address returns a “complaints per week within a block” count — the raw, unweighted number of 311 noise complaints filed within 150 metres of that point over the trailing 12 months, divided down to a weekly rate.

Computation

1. Every geocoded 311 noise complaint from the last 12 months is placed at its reported lat/lng.
2. Each complaint is weighted by type and time of dayfor the heatmap density layer only. Construction and amplified-music complaints weight 1.3×, vehicle/car-alarm complaints 1.1×, generic street/sidewalk reports 0.9×, most others 1.0×. The per-type weights are grounded in the Miedema & Vos (1998) dose–response curves for community noise annoyance.
3. Complaints filed between 10pm and 7am local time count 2× in the heatmap layer to reflect the disproportionate health impact of nighttime noise exposure documented by the WHO Environmental Noise Guidelines (2018) and Basner et al., Lancet 2014.
4. The city is tiled into a regular 200m grid. Each cell’s density is the sum of Gaussian kernel contributions from every complaint within 600m (3σ), with bandwidth σ = 200m. The 200m bandwidth is a fixed choice grounded in urban ground-level noise propagation (Murphy & King, 2014; EEA Good Practice Guide on Noise Mapping, 2008).
5. For a tapped or searched address, the complaints-per-week count is an inverse-distance-weighted average of the four nearest grid cells within 2× cell size. Addresses beyond that radius are reported as “outside data coverage” rather than extrapolated.
6. The count displayed is a raw, unweighted total — no kernel smoothing, no severity weights, no time-of-day multiplier. It is directly verifiable against the city’s raw open data feed.

What this count is not

• It is not a decibel reading. The count is based on reports that residents chose to file with the city. Complaint volume reflects reporting behavior, not ambient decibel levels.
• It is not comparable across cities in absolute terms. Cities differ in population density, reporting culture, and 311 system design.
• It is not a real-estate recommendation. Noise is one of many inputs to residential quality of life and the count is deliberately scoped to what 311 complaint records can tell us.
• Cities whose 311 noise data lacks coordinates (notably Chicago, whose noise data is all aircraft-noise complaints reported without point locations) don’t get a map.

Citations

• Basner, M., et al. (2014). “Auditory and non-auditory effects of noise on health.” Lancet, 383(9925), 1325–1332.
• World Health Organization Regional Office for Europe. (2018). Environmental Noise Guidelines for the European Region. Copenhagen: WHO Regional Office for Europe.
• Miedema, H. M. E., & Vos, H. (1998). “Exposure–response relationships for transportation noise.” Journal of the Acoustical Society of America, 104(6), 3432–3445.
• Murphy, E., & King, E. A. (2014). Environmental Noise Pollution: Noise Mapping, Public Health, and Policy. Elsevier.
• European Environment Agency. (2008). Good Practice Guide for Strategic Noise Mapping and the Production of Associated Data on Noise Exposure.

Citation format

Suggested citation format for articles and research:

311info, "Chicago 311 service requests," data through May 2026,
derived from the City of Chicago open 311 service request data.
https://311info.com/city/chicago/

Each city page links to the underlying dataset on the city’s portal, which may be cited as the primary source.

Cities tracked

32 cities, alphabetical: