Idling Violations Compared to PM2.5 Pollution Levels

Data and method

• PM2.5. The “PM 2.5” layer in the Air Quality group of the EJNYC Mapping Tool (ArcGIS item 85973791088e4d0ba4727a19e03281db, owner mocej.nyc.data), field aa_pm_25_t, 2,324 census tracts, retrieved 8 October 2026. The item description says the data comes from the DOHMH NYCCAS Air Pollution Rasters on NYC Open Data in processed form, and reads: “It displays data for the year 2026 and at the Census Tract level.” Values in the layer run from 5.08 to 11.30.
• Units. The layer does not state a unit. NYCCAS publishes PM2.5 in µg/m³, and the labels here use that unit on that basis.
• What NYCCAS values are. The NYC Open Data listing describes the rasters as annual-average surfaces predicted by a land-use regression model, and says they are not comparable to regulatory monitoring.
• NOVs. cacp_map_data_20261006.csv: 342,485 tickets with ticket number, violation year, latitude and longitude. 1 ticket has no coordinates and is left out. The slider adds one year of tickets at each stop. Its first stop, 2019, also includes the 17 tickets dated before 2019. The 420 tickets dated 2026 and the 67 with no year are added only at the last stop, “All”.
• Matching. Each ticket is assigned to the tract polygon that contains its coordinates. 297 tickets fall outside every tract polygon. They are drawn as dots and left out of the tables.
• Class breaks and area. The seven PM2.5 classes in the dot view are set for this page. They are not the EJNYC tool’s own classes. Tract area is computed from the layer’s polygons, which total 782.3 km².
• Council districts. Hovering a tract shows its City Council district and member. District boundaries are the City Council District layer in the EJNYC Mapping Tool (51 districts, retrieved 8 October 2026). Member names are as listed on council.nyc.gov on 8 October 2026, without leadership titles. A tract is matched to every district that covers at least a tenth of it, measured by sampling points across the tract; 320 of the 2,324 tracts fall in more than one district, and for those the share of the tract in each district is shown.
• Other air pollutants. The street view can also show the nitrogen dioxide, nitric oxide and black carbon layers from the Air Quality group of the EJNYC Mapping Tool (census-tract values, retrieved 8 October 2026). The tool’s descriptions say the nitrogen dioxide and nitric oxide layers show data for the year 2026, processed from the DOHMH NYCCAS Air Pollution Rasters; the black carbon layer has no description. The layers state no units; the labels use the units in the NYCCAS annual report (parts per billion for nitrogen dioxide and nitric oxide, micrograms per cubic metre for black carbon). For each of these pollutants the seven classes are cut at the same percentile ranks of tracts as the PM2.5 classes (the 6.6th, 27th, 59th, 81st, 95th and 97.3rd), so the three warm colors always mark roughly the top fifth of tracts. One tract in the PM2.5 layer has no value in these three layers and is left unfilled.
• Violations and pollution by census tract. Tracts are ranked once by PM2.5 and once by NOVs (by number, or per km² of tract area). A tract is highlighted when it is at or above the cut-off value for the chosen top share on both rankings. The cut-off values are shown under the map. Tracts tied at the cut-off are all included, and a tract with no NOVs is never counted as high for NOVs. The table under the map ranks tracts by PM2.5 alone. For the top 10%, 20% and 30% of tracts it gives the lowest PM2.5 value in the group, the group’s share of total tract area and its share of the violations matched to a tract.
• Violations and pollution by street. Each ticket is drawn as one dot on the street segment it was assigned to (see below). Its position along the segment is random, as is a sideways offset of up to about 5 m. Half of the dots are within 30 m of the ticket’s recorded coordinates and 95% within 137 m; on long segments the distance is greater. A ticket at an intersection is drawn on one of the segments meeting there, picked at random. The 125 tickets more than 50 m from any segment are drawn at their recorded coordinates.
• Street segments. The dot view uses the Department of City Planning’s LION file (ArcGIS layer “LION”, last edited 21 August 2026, retrieved 8 October 2026), limited to public and private streets (FeatureTyp 0 and 6) in the roadbed representation (RB_Layer B and R): 154,156 segments, each running from one LION node to the next.
• Assigning NOVs to segments. Each ticket goes to the nearest segment. Half of all tickets lie within 0.6 m of a segment and 99% within 11 m. A ticket with more than one segment within 1 m of the nearest, which is the case at intersections, could belong to any of them (51,438 tickets).
• No street basemap. The maps draw tract outlines only. Hover or tap a tract for its number, PM2.5 value and NOV count.