ThatCarHitMe.com
An Injuria.ai Company
YEAR-OVER-YEAR CRASH REPORT · CHICAGO, IL · DECEMBER 2021
Purpose: Machine-readable JSON endpoint for AI agents, LLMs, researchers, and programmatic consumers. Returns all underlying crash data and AI-generated commentary without HTML.
Authentication: None required. Public endpoint.
GET: https://thatcarhitme.com/api/crash-data/reports/data/illinois/chicago/december-2021-report
Monthly Traffic Safety Analysis
8,512 CRASHES IN
CHICAGO, IL
DECEMBER 2021
Total crashes in Chicago increased by 17.34% year-over-year, rising from 7254 in December 2020 to 8512 in December 2021. Fatalities also saw an increase of 13.33%, from 15 to 17, and injuries rose by 22.91%, from 1366 to 1679. The most notable shift was a 51.75% increase in pedestrian crashes, which rose from 143 to 217.
8,512
▲ 17.3%was 7,254
Total Crash Events
17
▲ 13.3%was 15
Persons Killed
1,679
▲ 22.9%was 1,366
Persons Injured
2,916
▲ 13.9%was 2,561
Hit-and-Run Crashes
Note: "Persons Killed" (17) counts individual fatalities across all crash events. "Fatal" in the severity table below (15) counts crash events where at least one fatality occurred. A single crash can result in multiple fatalities. 19 crashes with unreported severity are not shown in the severity breakdown.
Source: Chicago Traffic Crashes · Socrata Open Data · 2021-12-01 to 2021-12-31 · Aggregate counts from crash, person, and vehicle records
Trend Summary
Overall, crash data indicates an upward trend year-over-year, with total crashes increasing by 1258, representing a 17.34% rise. Total fatalities also increased by 2, a 13.33% change, and total injuries rose by 313, marking a 22.91% increase. These figures suggest a general worsening of traffic safety metrics in December 2021 compared to the prior year.
2,916
Hit-and-Run Crashes — December 2021
▲ 13.9% vs prior (2,561)
The number of hit-and-run crashes increased by 355, rising from 2561 in December 2020 to 2916 in December 2021. However, the overall hit-and-run rate decreased by 1.0 percentage point, from 35.3% of all crashes to 34.3%.
Vulnerable Road User Casualties
5
Pedestrians Killed
1
Cyclists Killed
11
Motorists Killed
0
Other Killed
204
Pedestrians Injured
46
Cyclists Injured
1,428
Motorists Injured
1
Other Injured
Source: Chicago Traffic Crashes · Socrata Open Data · 2021-12-01 to 2021-12-31 · Mode classified from person records (driver/passenger → motorist; pedestrian; bicyclist → cyclist; in-line skater / unspecified → other)
When Crashes Happen
The peak day for crashes shifted from Tuesday in December 2020 (1240 crashes) to Friday in December 2021 (1653 crashes), with Friday seeing a 54.5% increase year-over-year. While the peak hour remained 5 PM in both periods, the number of crashes during this hour decreased slightly from 683 to 637. Notably, Tuesday was the only day to experience a decrease in crashes, falling by 16.3% from 1240 to 1038.
Source: Chicago Traffic Crashes · Socrata Open Data · 2021-12-01 to 2021-12-31 · Crash date field aggregated by weekday
Source: Chicago Traffic Crashes · Socrata Open Data · 2021-12-01 to 2021-12-31 · Crash time field aggregated by hour (0-23)
Crash Severity Breakdown
The fatal crash rate remained stable at 0.2% of total crashes in both periods, despite an increase of 2 fatal crashes. The share of minor injury crashes increased from 7.4% to 8.5% of total crashes, representing an increase of 184 minor injury crashes. Conversely, the proportion of crashes resulting in no injuries decreased slightly from 85.7% to 85.1%.
Severity is per crash event (most severe injury). 15 fatal crash events resulted in 17 persons killed.
Outcome by Severity (Crash Events)
Source: Chicago Traffic Crashes · Socrata Open Data · 2021-12-01 to 2021-12-31 · KABCO injury classification scale
Severity Distribution
Source: Chicago Traffic Crashes · Socrata Open Data · 2021-12-01 to 2021-12-31 · Most severe injury per crash record
Top Contributing Factors
The top two contributing factors, "FAILING TO YIELD RIGHT-OF-WAY" and "FOLLOWING TOO CLOSELY", remained the same, increasing by 248 and 156 crashes respectively. "IMPROPER OVERTAKING/PASSING" saw a substantial increase of 147 crashes, a 48.5% count increase, rising from the fourth to the third most common factor. Conversely, "WEATHER" as a contributing factor decreased by 71 crashes, a 36.8% count decrease.
Officer-Reported Primary Contributing Cause
Source: Chicago Traffic Crashes · Socrata Open Data · 2021-12-01 to 2021-12-31 · Officer-reported primary contributory cause per crash
Road & Environmental Conditions
There was a notable shift in weather conditions, with crashes in 'SNOW' decreasing by 284, from 438 to 154. Correspondingly, crashes on 'SNOW OR SLUSH' road surfaces also decreased by 311, from 433 to 122. Conversely, crashes occurring in 'RAIN' increased by 310, while crashes on 'WET' road surfaces increased by 448.
Weather
Source: Chicago Traffic Crashes · Socrata Open Data · 2021-12-01 to 2021-12-31 · Weather condition at time of crash
Lighting
Source: Chicago Traffic Crashes · Socrata Open Data · 2021-12-01 to 2021-12-31 · Lighting condition field
Road Surface
Source: Chicago Traffic Crashes · Socrata Open Data · 2021-12-01 to 2021-12-31 · Road surface condition field
Vehicles & Demographics
The total number of vehicles involved in crashes increased by 2632, from 14737 to 17369, representing a 17.86% rise. The number of pedestrians involved increased by 83, from 150 to 233, marking a 55.3% increase. Similarly, bicycle involvement rose by 16, from 52 to 68, a 30.8% increase. The top five vehicle makes involved in crashes remained consistent, with Chevrolet, Toyota, and Ford continuing to be the top three.
Top Vehicle Makes (17,369 vehicles)
Source: Chicago Traffic Crashes · Socrata Open Data · 2021-12-01 to 2021-12-31 · Vehicle unit records
5,868 persons with unknown or unrecorded age excluded from age chart. Age=0 in Chicago records is a sentinel for unknown/unrecorded age (not infants) and is grouped with nulls.
Sex Distribution (18,081 persons with recorded sex)
Source: Chicago Traffic Crashes · Socrata Open Data · 2021-12-01 to 2021-12-31 · Person-level records linked to crash events
Speed Limit Zones
Crashes in 30 mph zones increased by 973, from 5304 to 6277, and the fatal crash rate in these zones slightly increased from 0.17% to 0.207%. In 35 mph zones, the number of crashes remained relatively stable, decreasing by 3 from 564 to 561, but the fatal crash rate in these zones increased from 0.177% to 0.357%. Notably, speed zones of 10 mph, 20 mph, and 25 mph all saw their fatal crash rates drop to 0% in the current period, down from 0.488%, 0.33%, and 0.219% respectively.
Fatal crashes by zone: 30 mph: 13 of 6,277 (0.207%) · 35 mph: 2 of 561 (0.357%)
Source: Chicago Traffic Crashes · Socrata Open Data · 2021-12-01 to 2021-12-31 · Posted speed limit at crash location
Data Sources & Methodology
Primary Data Source
All crash data in this report is sourced from Chicago Traffic Crashes, accessed programmatically via the Socrata Open Data API (SODA). This dataset contains official police-reported motor vehicle traffic crash records maintained by the reporting jurisdiction's law enforcement agency. Records are published to the open data portal by the municipality and are subject to the portal's terms of use.
Data Retrieval
- Access method: Socrata Open Data API (SoQL queries)
- Data format: Structured JSON via REST API
- Record types queried: Crash events, person records, and vehicle unit records
- Date filter applied: 2021-12-01 through 2021-12-31
- Report generated: June 1, 2026
Data Coverage
- Reporting period: 2021-12-01 through 2021-12-31 (31 days)
- Geographic scope: Chicago, IL
- Total crash records analyzed: 8,512
- Total persons involved: 18,433
- Total vehicles involved: 17,369
Analytical Methodology
- Severity classification: Uses the KABCO injury scale (K=Fatal, A=Incapacitating injury, B=Non-incapacitating injury, C=Possible injury, O=No injury/property damage only), the standard classification in U.S. Model Minimum Uniform Crash Criteria (MMUCC). Severity is assigned per crash event based on the most severe injury in that crash. A single fatal crash (K) may involve multiple fatalities; therefore the "Persons Killed" count in the headline KPIs may differ from the "Fatal" crash count in the severity breakdown.
- Contributing factors: Reflect the officer-determined primary contributory cause recorded at the time of the crash report. These are preliminary determinations and may not reflect final investigation findings.
- Hit-and-run classification: Based on the hit-and-run indicator field in the official crash report, as determined by the responding officer at the scene.
- Temporal analysis: Day-of-week and hour-of-day distributions are computed from the crash date/time timestamp in each record.
- Demographics: Age and sex distributions are drawn from person-level records linked to each crash event. A single crash may involve multiple persons.
- Vehicle data: Make information is drawn from vehicle unit records linked to each crash event.
- AI commentary: Narrative sections are generated by Google Gemini (large language model) based on the structured data. Commentary is descriptive, not predictive, and should not be interpreted as expert opinion.
Limitations & Disclaimers
- Only crashes reported to and documented by law enforcement are included. Minor incidents, unreported crashes, and near-misses are not captured in this dataset.
- Data reflects conditions at the time of the initial police report and may be subject to subsequent corrections, reclassifications, or supplements by the reporting agency.
- Open data portal records may experience a publication lag - recently occurring crashes may not yet appear in the dataset at the time of report generation.
- AI-generated commentary is produced by a large language model and is intended to highlight patterns in the data. It does not constitute legal, medical, or professional analysis.
- Percentages are calculated from reported data and are subject to rounding.
Non-Affiliation Disclosure
This report is produced independently by ThatCarHitMe.com (Injuria.ai). It is not affiliated with, endorsed by, or produced in partnership with any law enforcement agency, municipal government, state department of transportation, or the National Highway Traffic Safety Administration (NHTSA). Data is sourced from publicly available government open data portals.
Data License
The underlying crash data is provided under the municipality's Open Data Terms of Use and is made available to the public for unrestricted use. This analysis and report is © 2026 Injuria.ai and may be cited with attribution using the suggested citation below.
Corrections & Feedback
If you believe any data in this report is inaccurate or have questions about our methodology, please contact: data@injuria.ai. We are committed to accuracy and will issue corrections promptly.
Suggested Citation
ThatCarHitMe.com (Injuria.ai). "Chicago, IL Crash Intelligence Report." Published June 1, 2026. Data source: Chicago Traffic Crashes, Socrata Open Data. Available at: https://thatcarhitme.com/crash-data/illinois/chicago/december-2021-report
About the Publisher
ThatCarHitMe.com is a crash data intelligence platform developed by Injuria.ai, a legal technology company specializing in traffic safety analytics. We aggregate and analyze publicly available government crash data to produce structured intelligence reports for communities, researchers, journalists, and legal professionals. Our reports combine programmatic data retrieval from official open data portals with AI-assisted narrative analysis.
Questions about this report's data or methodology: data@injuria.ai
ThatCarHitMe.com · An Injuria.ai Company
ThatCarHitMe.com
An Injuria.ai Company
Crash Data Intelligence
Data: Chicago Traffic Crashes · Socrata
Period: 2021-12-01 – 2021-12-31
Generated: June 1, 2026 · All rights reserved