--- title: "Chicago crash map coverage and missing locations" description: "Compare a broad Chicago crash map with its full filtered table. Keep unmapped records, location rules, coverage dates, and source revisions visible" canonical: "https://scalewithsearch.com/articles/chicago-crash-map-missing-location-coverage" --- ## Site navigation - [Scale With Search](https://scalewithsearch.com/) - Services - Services - [AI systems](https://scalewithsearch.com/ai-systems) - [Site build](https://scalewithsearch.com/work#site-build) - [Whole website fix](https://scalewithsearch.com/work#whole-website-fix) - [Content library with SEO](https://scalewithsearch.com/work#content-library) - [Working session](https://scalewithsearch.com/audit) - Start here - [Send your brief](https://scalewithsearch.com/work#send-your-brief) - [Example scope](https://scalewithsearch.com/work#review-the-example-scope) - [Prices and terms](https://scalewithsearch.com/work#prices-and-terms) - Industries - Real estate - [Real estate agents and teams](https://scalewithsearch.com/for/real-estate) - [Platforms, ownership, and IDX](https://scalewithsearch.com/for/real-estate/real-estate-website-platforms-ownership-idx) - [Search, content, and AI](https://scalewithsearch.com/for/real-estate/real-estate-search-content-ai) - [Inquiries, campaigns, and handoffs](https://scalewithsearch.com/for/real-estate/real-estate-website-inquiries-campaigns-handoffs) - [Buyer, seller, and local pages](https://scalewithsearch.com/for/real-estate/real-estate-buyer-seller-local-resources) - [Rules, privacy, and trust](https://scalewithsearch.com/for/real-estate/real-estate-website-rules-privacy-trust) - Browse by business - [Trades and home services](https://scalewithsearch.com/for/#group-trades) - [Health, wellness, and animal care](https://scalewithsearch.com/for/#group-practices) - [Law, finance, and IT](https://scalewithsearch.com/for/#group-professional) - [Marketing and SEO agencies](https://scalewithsearch.com/for/#group-agencies) - [Shops and manufacturers](https://scalewithsearch.com/for/#group-manufacturing) - [Restaurants, shops, studios, and nonprofits](https://scalewithsearch.com/for/#group-local-services) - Chiropractic practices - [Chiropractic and wellness practices](https://scalewithsearch.com/for/chiropractic-and-wellness-practices) - [Chiropractic and physical therapy clinics](https://scalewithsearch.com/for/chiropractic-and-physical-therapy-clinics) - [All industries](https://scalewithsearch.com/for/) - Resources - Free tools - [AI readiness check](https://scalewithsearch.com/check) - [Free tools](https://scalewithsearch.com/tools/) - [Free Starter Kit](https://scalewithsearch.com/kit/business-memory-starter-kit.zip) - Guides - [AI-native library](https://scalewithsearch.com/ai-native) - [Industry intelligence](https://scalewithsearch.com/intelligence) - [Office job guides](https://scalewithsearch.com/guides/) - [Business memory](https://scalewithsearch.com/articles/business-memory-for-ai-agents-guide) - [Agent governance](https://scalewithsearch.com/articles/ai-agent-governance-guide-small-business) - [Migration and ownership](https://scalewithsearch.com/articles/leaving-vendor-ai-memory-guide) - Articles - [All articles](https://scalewithsearch.com/articles/) - [What changed](https://scalewithsearch.com/changes/) - About - Evidence - [Proof](https://scalewithsearch.com/proof) - Scale With Search - [About](https://scalewithsearch.com/about) - [How it works](https://scalewithsearch.com/how-it-works) # Chicago crash maps: keep missing locations in the coverage count A broad-area crash map shows the records its location rule can place. The full filtered table may contain additional records that cannot enter that map. Keep those records in a separate coverage count before discussing a geographic pattern. For a personal injury firm's research meeting, the useful deliverable is a reconciled map and table. State the total eligible records, the mapped subset, and the unresolved remainder. Explain which date and source edition govern the comparison. The [personal injury firm overview](/for/personal-injury-law-firms) addresses the firm's information workflow. The [public-evidence intelligence guide](/intelligence/personal-injury-law-firms) introduces broad aggregate research. This guide explains how to document location coverage without identifying individual incidents or treating a map as a demand forecast. ## Establish what Chicago's source covers Chicago describes the dataset as traffic crashes on city streets within city limits and under CPD jurisdiction. It excludes crashes where another agency handles the report, including typical interstate, ramp, and boundary-road cases. This is a source boundary to preserve in the map caption. [Chicago dataset description, checked October 28, 2026](https://data.cityofchicago.org/Transportation/Traffic-Crashes-Crashes/85ca-t3if). Do not title the map “all Chicago crashes.” A more defensible title describes the selected records from this source. Keep the jurisdiction limitation beside the graphic rather than expecting the reader to discover it elsewhere. The publisher reports partial district availability in 2015 and citywide availability beginning in September 2017. A map using the early period needs that coverage distinction. Equal calendar lengths do not make those historical windows equivalent citywide observations. [Chicago historical coverage description, checked October 28, 2026](https://data.cityofchicago.org/api/views/85ca-t3if.json). Choose the research window before examining the pattern. Record its start and end boundaries and the selected date field. If the purpose changes, document a revised selection instead of quietly moving the window to obtain a clearer picture. ## Read where the location fields come from The dictionary describes `latitude`, `longitude`, and `location` as crash-location fields derived from the reported crash address. It attributes location determination to the reporting officer. The `location` field supports mapping and geographic analysis in the portal software. [Chicago location-field dictionary, checked October 28, 2026](https://data.cityofchicago.org/api/views/85ca-t3if.json). These definitions describe a published derivation. They do not establish independently measured coordinates for every record. Do not label the fields as verified device positions or assume that a populated coordinate proves exact placement. The publisher links the IDOT reporting manual for the underlying form. Its 2019 edition includes address and roadway-location instructions, including instruction 8 on the nearest address number. That context supports reading location as reported information. [IDOT SR 1050 instruction manual, 2019, instruction 8](https://idot.illinois.gov/content/dam/soi/en/web/idot/documents/transportation-system/manuals-guides-and-handbooks/safety/illinois-traffic-crash-report-sr-1050-instruction-manual-2019.pdf). For this broad-area research task, retain the source definitions and use aggregate outputs. Exact incident plotting, reconstructed addresses, and attempts to identify people are outside the worksheet's purpose. ## Define eligibility before requiring coordinates Begin with the full table that meets the agreed non-location filters. Those filters might describe a reporting period and an injury measure. Write them down without adding a coordinate requirement at this first stage. Call this the eligible-record denominator. Next apply the documented location rule. The mapped subset consists of eligible records that pass that rule and receive a broad-area assignment. The rest remain eligible records with unresolved map placement. This order makes coverage visible. If the first filter removes missing coordinates, the resulting table cannot tell the reader how many eligible records disappeared. A map built from that subset alone needs a separate count from the original selection. Keep each stage's unit unchanged. These counts concern crash records. They do not become injured-person counts, residents, vehicle trips, or potential legal matters because they appear on a map. Where the map also uses injury fields, retain the exact injury selection. The companion [injury-measurement guide](/articles/chicago-crash-injury-severity-person-counts) distinguishes crash severity from reported injured-person totals. A location rule should not erase that distinction. ## Work through a synthetic coverage table All numbers below are invented for a worksheet exercise. They describe no current Chicago period, neighborhood, incident, or missing-location fraction. No individual records or precise locations are shown. Suppose the non-location filters produce 1,000 eligible crash records. The exercise's location rule requires usable coordinates and a successful assignment to the selected broad-area boundaries. The team records three mutually exclusive outcomes. | Synthetic coverage outcome | Crash records | Share of all eligible records | | --- | --- | --- | | Assigned to a broad area and included in the map | 870 | 87% | | Required location information unavailable | 100 | 10% | | Location present but broad-area assignment unresolved | 30 | 3% | | All eligible records | 1,000 | 100% | The map contains 870 records. The full filtered table contains 1,000. Its coverage is 870 divided by 1,000, or 87 percent under this exercise's rule. The remaining 130 records still belong in the research note. Do not merge the last two outcomes without an explanation. Missing required information and unresolved boundary assignment are different review tasks. A boundary-assignment problem should not be described as a publisher's missing coordinate. The arithmetic must reconcile: 870 plus 100 plus 30 equals 1,000. A failure to balance signals an incomplete classification or overlapping groups in the worksheet. Resolve that accounting before showing the geographic graphic. ## Keep the map denominator beside area shares Imagine one broad synthetic area contains 174 of the 870 mapped records. It accounts for 20 percent of the mapped subset. It represents 17.4 percent of all 1,000 eligible records as currently assigned. Those percentages answer different questions. The first describes distribution within the mapped subset. The second describes the assigned area's known share of the full eligible table. Neither assigns any of the 130 unresolved records to that area. Do not spread unresolved records evenly across areas to complete the picture. Such an allocation would be an assumption. This worksheet leaves their geography unknown and shows the remainder beside the map. A reader also needs the denominator behind any color scale. State whether a shaded area shows a record count or a share of mapped records. Avoid labels that suggest resident risk, travel risk, or legal demand. This exercise supplies no exposure measure, such as travel volume. Its geographic count therefore cannot establish that one broad area is more dangerous for a comparable journey. It also cannot identify where people will seek counsel. ## Use location checks as documented review rules Write down the rule used to call location information usable. For a coordinate-based map, the review can distinguish absent values, invalid numeric inputs, and records that fail the chosen boundary assignment. These are proposed checks, not claims about current Chicago defects. Keep original source values separate from derived review outcomes. If a record fails placement, record the reason in the aggregate reconciliation. Do not replace the source location with a guess that makes the map look complete. If a table offers both coordinates and a point-type field, choose the controlling input before processing. State how conflicting inputs will be handled. The dictionary describes their purpose but does not resolve every possible inconsistency in a research workflow. Have the reviewer inspect the boundary reference too. A broad-area map depends on which boundaries and edition the team selected. A revised boundary file can change assignment even when the source coordinates remain the same. A failed assignment does not prove that a crash occurred outside the source's coverage. It establishes that the chosen mapping process has not assigned the record. Preserve that narrower meaning until the discrepancy is resolved. ## Separate time coverage from location coverage A complete-looking map can still compare unequal historical coverage. Confirm the source window before using mapped counts across years. The partial early district period and the later citywide period need separate treatment. Within an agreed common window, calculate map coverage for each comparison group. Consider a synthetic second period with 1,000 eligible records and 950 mapped records. Its 95 percent coverage differs from the first exercise's 87 percent. That difference affects how the maps should be read. A change in mapped totals could reflect changed geographic completeness as well as changed eligible counts. The worksheet does not determine which explanation applies without additional source review. Report the two denominators side by side. Keep the selected date field and map rule consistent. If they change, explain the change before presenting a trend. Do not infer why location information is unavailable from an empty field. The dictionary establishes field meanings, not the cause of every missing value. A valid research outcome can state that the reason remains unverified. ## Preserve the access date and source edition Chicago says reports are added when finalized and can change through amendments. A map's extraction date therefore belongs in the research record, separately from the selected crash period. [Chicago publication and amendment description, checked October 28, 2026](https://data.cityofchicago.org/api/views/85ca-t3if.json). Record a source snapshot reference and retain the definitions used for that edition. Do not label an access timestamp as the time every incident occurred or the date every location was checked. When repeating the research, compare eligible, mapped, unavailable, and unresolved-assignment counts. If the result changes, preserve both versions. Identify whether filters, boundary references, mapping rules, or source records changed where the evidence allows. The [business-memory guide](/articles/business-memory-for-ai-agents-guide) explains how source notes and corrections support later work. Store the accepted map definition with the aggregate. A future researcher needs the counting rules as well as the graphic. ## Prepare a broad-area review worksheet Use the following questions before a practice partner reads the map. They are suggested review controls for aggregate research, not a Chicago publication requirement. | Worksheet item | Required research note | | --- | --- | | Source boundary | Dataset, CPD jurisdiction scope, and historical coverage limitation | | Selection | Date field, interval, and every non-location filter | | Full denominator | All eligible crash records before location exclusions | | Map rule | Required location fields and broad-area assignment rule | | Coverage accounting | Mapped, unavailable, unresolved, and reconciled total | | Geography reference | Broad-area boundary source and edition | | Display meaning | Count or mapped-subset share, with denominator | | Version | Access date, snapshot reference, and known revisions | The partner's research question should remain broad. For example: “Which geographic completeness limits affect this comparison of our service area?” The map should not become a list of incidents or a basis for contacting injured people. For a written handoff, attach the coverage table beside the map. Keep the full denominator visible when the graphic is copied into a meeting document. The map and its accounting describe one result. Scale With Search can define the source boundary, coverage worksheet, and acceptance checks for a bounded research function. Start with the aggregate question and the information the function is allowed to retain. [Define the scope](/work) Continue the website review: [AI-native injury law firms: the first functions to build](/articles/ai-native-injury-law-first-functions); [Chicago crash injuries: distinguish the most severe category from the number of people](/articles/chicago-crash-injury-severity-person-counts); [Injury law firm AI rules: data, approvals, and spend](/articles/injury-law-firm-ai-rules-data-approvals-spend); [NHTSA complaint dates: separate the incident, receipt, and file addition](/articles/nhtsa-complaint-incident-received-added-dates); [NHTSA complaint counts: distinguish ODI references from component rows](/articles/nhtsa-complaint-odi-reference-component-row-counts); [Injury firm rebrand: map old website pages first](/articles/personal-injury-firm-rebrand-website-redirects); [AI gets your injury firm wrong: check the source facts](/articles/personal-injury-firm-wrong-ai-answer-facts); [Injury law firm virtual offices and Google profiles](/articles/personal-injury-law-firm-virtual-office-profile); [Injury website settlement calculators: check the promise](/articles/personal-injury-settlement-calculator-website-review); [Spanish injury firm pages: review the whole inquiry path](/articles/personal-injury-spanish-website-page-review); [Personal injury website leads: test the case review path](/articles/personal-injury-website-case-review-delivery); [Injury firm website fees: explain costs separately](/articles/personal-injury-website-contingency-fee-costs); [Injury website form spam: protect the real inquiry path](/articles/personal-injury-website-form-spam-control-review); [Injury website file uploads: define the private handoff](/articles/personal-injury-website-medical-record-upload-brief); [Personal injury settlement results on your website](/articles/personal-injury-website-settlement-results); [Injury website thank-you pages: keep the receipt plain](/articles/personal-injury-website-thank-you-page-privacy). [personal injury law firms](/for/personal-injury-law-firms): website and search resources. ## Related: personal injury law firms - [Injury law firm AI rules: data, approvals, and spend](/articles/injury-law-firm-ai-rules-data-approvals-spend) - [NHTSA complaint dates: separate the incident, receipt, and file addition](/articles/nhtsa-complaint-incident-received-added-dates) - [NHTSA complaint counts: distinguish ODI references from component rows](/articles/nhtsa-complaint-odi-reference-component-row-counts) ---- ```text .|########||. .|########||. .|########||. |##||. .||##|. |##||. .||##|. |##||. .||##|. |#|. .|#|. |#|. .|#|. |#|. .|#|. |#| |#| |#| |#| |#| |#| .#| |#. .#| |#. .#| |#. .#. .#| .#. .#| .#. .#| |#. .#| |#. .#| |#. .#| |# ...... #| |# ...... #| |# ...... #| .# ||#########| #| .# ||#########| #| .# ||#########| #| .#. |######||######|. .#. .#. |######||######|. .#. .#. |######||######|. .#. #. .##|###|##|#|######| .# #. .##|###|##|#|######| .# #. .##|###|##|#|######| .# || |##|#||||||||||||#||#| || || |##|#||||||||||||#||#| || || |##|#||||||||||||#||#| || # |#||||||||||||||||||||#| #. # |#||||||||||||||||||||#| #. # |#||||||||||||||||||||#| #. || |#||||||||||||||||||||||#| || || |#||||||||||||||||||||||#| || || |#||||||||||||||||||||||#| || # .#||||||||||||||||||||||||#| # # .#||||||||||||||||||||||||#| # # .#||||||||||||||||||||||||#| # || ....|||#||||||##|#|||#|#||##||||....|. || || ....|||#||||||##|#|||#|#||##||||....|. || || ....|||#||||||##|#|||#|#||##||||....|. || #. . ....|# ....#||| ||| .#||| ....#. .# #. . ....|# ....#||| ||| .#||| ....#. .# #. . ....|# ....#||| ||| .#||| ....#. .# # . ||||#| .#####|| . .#| .#||| ||||# #. # . ||||#| .#####|| . .#| .#||| ||||# #. # . ||||#| .#####|| . .#| .#||| ||||# #. .| ||||| #. |#|||||. || #. |#||. .||||| || .| ||||| #. |#|||||. || #. |#||. .||||| || .| ||||| #. |#|||||. || #. |#||. .||||| || || |.... #. ....|#. |. ...|. ....|| || || |.... #. ....|#. |. ...|. ....|| || || |.... #. ....|#. |. ...|. ....|| || #. .||||||##||||||##||####|||||||#||||||#| .# #. .||||||##||||||##||####|||||||#||||||#| .# #. .||||||##||||||##||####|||||||#||||||#| .# # .||####|###########################|. # # .||####|###########################|. # # .||####|###########################|. # # .#||||||.#.|| # |. ..# #| #|||||#| # # .#||||||.#.|| # |. ..# #| #|||||#| # # .#||||||.#.|| # |. ..# #| #|||||#| # # .#|||||| .. |# ## |#| ...#|#|||#| # # .#|||||| .. |# ## |#| ...#|#|||#| # # .#|||||| .. |# ## |#| ...#|#|||#| # # .#|||#|# .# .#| #| ##|.#..#|||||#| # # .#|||#|# .# .#| #| ##|.#..#|||||#| # # .#|||#|# .# .#| #| ##|.#..#|||||#| # # .#||||||############|######|||||#| # # .#||||||############|######|||||#| # # .#||||||############|######|||||#| # # |...||#||||||#||||#|#||||||#|||||#||| |.| # # |...||#||||||#||||#|#||||||#|||||#||| |.| # # |...||#||||||#||||#|#||||||#|||||#||| |.| # #. .. ||||# .|||##|. |#| .|| || .|||#. #| # .# #. .. ||||# .|||##|. |#| .|| || .|||#. #| # .# #. .. ||||# .|||##|. |#| .|| || .|||#. #| # .# || | ...|| ...##| | #| .|. |. ##### .. .| || || | ...|| ...##| | #| .|. |. ##### .. .| || || | ...|| ...##| | #| .|. |. ##### .. .| || || ||||| || ||||#| . |. |. |#. ||||| |#| || || || ||||| || ||||#| . |. |. |#. ||||| |#| || || || ||||| || ||||#| . |. |. |#. ||||| |#| || || .# |.....#|....|#.||||.|||##.|#|....||.#||.#. #. .# |.....#|....|#.||||.|||##.|#|....||.#||.#. #. .# |.....#|....|#.||||.|||##.|#|....||.#||.#. #. #.|||||||#############################| ||| .# #.|||||||#############################| ||| .# #.|||||||#############################| ||| .# || ##||#||#||||||#||#||#||#||##. || || ##||#||#||||||#||#||#||#||##. || || ##||#||#||||||#||#||#||#||##. || # .#|||||||||#||#|||||||||||#| # # .#|||||||||#||#|||||||||||#| # # .#|||||||||#||#|||||||||||#| # || |#||||||||||||||||||||||#| || || |#||||||||||||||||||||||#| || || |#||||||||||||||||||||||#| || .# |#||||||||||||||||||||#| #. .# |#||||||||||||||||||||#| #. .# |#||||||||||||||||||||#| #. || |#||||||||||||||||||#| || || |#||||||||||||||||||#| || || |#||||||||||||||||||#| || #. .######|#|#########| .# #. .######|#|#########| .# #. .######|#|#########| .# .#. |#####||||#####| .#. .#. |#####||||#####| .#. .#. |#####||||#####| .#. |# ||########|| #. |# ||########|| #. |# ||########|| #. |# ...... #| |# ...... #| |# ...... #| |#. .#| |#. .#| |#. .#| |#. .#. |#. .#. |#. .#. .#| |#. .#| |#. .#| |#. |#| |#| |#| |#| |#| |#| .|#|. .|#|. .|#|. .|#|. .|#|. .|#|. |##||. .||##| |##||. .||##| |##||. .||##| .||########||. .||########||. .||########||. 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