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Historical Crash and Transportation Data for Safety Analysis

See how we examined crash and demographic data from the City of Chicago with Ecopia’s high-precision geospatial data to better understand transportation safety in the region.

This blog covers key findings from a StoryMap where Ecopia AI (Ecopia) layered 2023 crash data from the City of Chicago with demographic data from the US Census Bureau and Advanced Transportation Feature infrastructure data from Ecopia to understand where crashes occurred, what conditions contributed to those crashes, and which communities have the most traffic risk.

Rising traffic fatalities in the US: a growing concern

According to the US Department of Transportation (DOT), over 350,000 people lost their lives in motor vehicle accidents between 2011 and 2020. While the final figures are still being tallied for 2023, 2022 recorded 42,795 deaths—the highest figure since 2005. These deaths account for 95% of all fatalities related to US transportation infrastructure, and disproportionately impact disadvantaged communities.

A bar graph illustrating the steady increase in traffic fatalities since 2011; source: US DOT.
Traffic fatalities have been steadily increasing since 2011; source: US DOT.

Fatalities do not only include motorists; too often, pedestrians and cyclists are also killed or injured in traffic accidents. Pedestrian and bicyclist fatalities account for almost 20% of all traffic deaths each year. Additionally, about 76,000 pedestrians and 47,000 bicyclists are injured in roadway crashes annually.

Motor vehicle crashes have overall been increasing across the country. US DOT data shows that in 2021 there were over 6.1 million police-reported traffic crashes, representing an 8.7% increase since 2012. Nearly 30% of these crashes resulted in injuries.

Given these alarming trends in traffic safety, it's no surprise that state DOTs and metropolitan planning organizations (MPOs) are devoting more and more resources to understanding - and preventing - crashes. Initiatives like Vision Zero are growing in popularity, while data and analytics are providing an unprecedented level of insight into traffic safety conditions nationwide.

Geospatial data plays a particularly important role in helping DOTs and MPOs not only understand traffic safety, but also design and implement strategic mitigation efforts to reduce traffic incidents. Layering multiple geospatial datasets together to derive these insights is critical, as many community characteristics contribute to transportation safety.

Where did crashes occur in 2023?

Our analysis began by examining the locations of the 109,597 police-reported motor vehicle crashes that occurred in the City of Chicago in 2023. Next, we looked at the breakdown of total crashes by census block group (CBG) to better understand the geographic distribution of these crashes, and where they are most likely to occur. As can be expected, more crashes occurred in the downtown Chicago area, although there are also hot spots near O'Hare airport and along major roadways.

Map showing 2023 motor vehicle crashes in Chicago, broken down by census block group.
A sample map illustrating 2023 motor vehicle crashes in Chicago by census block group.

An interactive version of the map can be explored here, where you can click on each CBG to discover detailed information about the types of crashes that occurred in 2023, along with insights into the local population and the demographic factors that may influence crash risk.

After establishing a baseline understanding of where crashes occurred, we examined what types of crashes are more common in certain geographic areas. In 2023, 140 fatal crashes occurred in the City of Chicago. We mapped these incidents to highlight the precise locations where they took place. Next, we visualized this data by CBG. The map below shows where fatal crashes are more likely to occur. In 2023, the vast majority of CBGs in our study area reported no fatal crashes, with most experiencing no more than two. However, a few hotspots for fatal crashes emerged, notably in downtown Chicago as well as in neighborhoods like Pilsen and South Deering.

Map showing 2023 fatal crashes by census block group in the Chicago region.
A sample map illustrating 2023 fatal crashes by census block group in the Chicago region.

Next, our team mapped the 16,620 crashes involving injuries, revealing a more even distribution across the city, similar to the overall crash map. Although these incidents account for only about 15% of all crashes, the visualization indicates there is no discernible geographic pattern. Similarly, when visualizing by CBG, the map generally shows the same hotspots for crashes with injuries as overall crashes, as illustrated below. 

Map showing 2023 crashes involving injuries by census block group in the Chicago region.
A sample map illustrating 2023 crashes involving injuries by census block group in the Chicago region.

The next part of the analysis involved mapping the 2,722 pedestrian-involved crashes. As expected, the majority of these crashes are clustered in downtown Chicago, reflecting higher pedestrian activity in the area. However, when mapping these crashes by CBG, a clear pattern emerges: pedestrian-involved crashes are most likely to occur in the urban downtown section of the city. By overlaying these crashes with daytime population density, we can clearly see that they tend to happen in areas with higher concentrations of people during the day.

Map showing that 2023 pedestrian-involved crashes are most likely to occur in the urban downtown area of Chicago.
A sample map illustrating that 2023 pedestrian-involved crashes are most likely to occur in the urban downtown section of Chicago.

When our team mapped the 1,931 crashes involving cyclists, a clear trend emerged: these incidents were concentrated in downtown Chicago, with a higher likelihood of crashes occurring in the northern parts of the city compared to the southern. This pattern is further confirmed when visualized by CBG, showing that while some cyclist-involved crashes happen in the northern areas, the vast majority are clustered in the downtown core.

Map showing 2023 crashes involving cyclists by census block group in the Chicago region.
A sample map illustrating 2023 crashes involving cyclists by census block group in the Chicago region.

You can explore the data in greater detail, along with all the interactive versions of the maps featured in this section here.

How do demographic characteristics relate to crashes?

Layering census data with historical crashes provides deeper context about who lives and works in the areas experiencing crashes. This insight can be used to inform decision-making about where to focus resources aimed at enhancing traffic safety.

Understanding commuting beavior

Census data can also be used to understand how people living in each CBG commute to work, and how that relates to crash incidents. The data shows that CBGs with "walking" cited as the predominant commute type have 2.5x more crashes on average. These CBGs experienced 1.5x more fatal crashes, 2x more crashes with injuries, 3.7x more pedestrian-involved crashes, and 3.6x more bike-involved crashes. You can explore the full map in detail here to gain insights into how commuting behavior varies across different locations.

Map showing how commuting behavior varies by location in the Chicago region.
A sample map illustrating how commuting behavior varies by location in the Chicago region.

What role does race play in traffic safety?

Layering demographic data into our analysis can help us better understand how race relates to the likelihood of traffic incidents. We first mapped CBGs by predominant race and quantified the crashes that occurred in each in 2023. What we found is that 65% of crashes in 2023 took place in CBGs with a predominantly non-white population. On average, these CBGs each experienced 8.5 more crashes than predominantly white CBGs. 

In fact, CBGs with a majority non-white population experienced more crashes involving fatalities and injuries. These CBGs also had more crashes citing 'no traffic controls' as a contributing cause. In majority non-white CBGs, 39,512 crashes happened in locations with no traffic controls, while in majority white CBGs only 20,328 of these crashes occurred. Likewise, crashes in majority non-white CBGs areas cited 'worn reflective material' on traffic signage as a contributing factor 2x more often. Crashes caused by obstructed crosswalks also occurred 6x more often in majority non-white CBGs.

Map showing 2023 crashes in the Chicago region broken down by race.
A sample map illustrating how 2023 crashes in the Chicago region by race.

You can view the full interactive map here.

What role does income play in traffic safety?

To explore the impact of income on traffic safety, we conducted a similar analysis using median household income. We began by classifying each census block group (CBG) into income quintiles and then quantified the crashes that occurred in each quintile in 2023. The differences in crash occurrence between CBGs in the top and bottom 20% of median household income are less stark, but still significant. Over 31% of all crashes in 2023 took place in CBGs in the bottom 20% of income, compared to 19% in the top 20%. That amounts to a difference of more than 13,000 crashes per year.

Map showing the classification of census block groups by median household income quintiles, used to analyze the relationship between income levels and traffic crashes in 2023.
A sample of the map showing the classification of census block groups by median household income quintiles, used to analyze the relationship between income levels and traffic crashes in 2023.

Diving deeper, lower income CBGs were found to have 2x more fatal crashes on average than higher income CBGs. However, crashes involving cyclists are more than 3x as common in higher income CBGs.

Our findings also revealed that In lower-income CBGs, 19,315 crashes happened in locations with no traffic controls, while in higher-income CBGs only 10,472 of these crashes occurred. Moreover, lower-income CBGs noted worn road surfaces as a contributing cause in 2.8 more crashes than higher-income CBGs. Similarly, lower-income CBGs had 4x more crashes citing "worn reflective material" on traffic signage as a contributing factor.

You can explore these findings in more detail, along with interactive versions of the maps, by clicking here. 

Analyzing transportation infrastructure with historical crash data

These statistics show how traffic and pedestrian infrastructure play a key role in transportation safety. While some crashes occur due to driver behavior and weather, many are caused by inadequate or nonexistent safety infrastructure.

To better understand how crashes relate to existing infrastructure, more and more DOTs and MPOs are digitizing transportation features into vector data. This data can then be layered with historical crash and census data to dive deeper into where and why crashes are most likely to occur.

Leveraging our artificial intelligence (AI)-based mapping systems, Ecopia recently digitized Advanced Transportation Features across the entire City of Chicago. Click here to pan around an interactive version of the map and explore how transportation infrastructure varies throughout the city. 

Map showing a sample of Ecopia’s Advanced Transportation Feature data extracted in Chicago.
A sample of Ecopia’s Advanced Transportation Feature data extracted in Chicago.

We layered in 2023 crash data to better visualize and understand what pedestrian and traffic infrastructure exists near crash locations. This can help determine where to make improvements that will reduce the likelihood of future crashes in these areas.

Map showing a sample of Ecopia’s Advanced Transportation Feature data overlaid with 2023 historical crash data in Chicago.
A sample of Ecopia’s Advanced Transportation Feature data overlaid with 2023 historical crash data in Chicago.

Layering demographic, infrastructure, and historical crash data for decision-making

Sidewalks are a critical component of pedestrian infrastructure that can play a key role in enhancing pedestrian safety, accessibility, and equity. However, incomplete or poorly connected sidewalks create hazards by forcing pedestrians to share roadways with vehicles, significantly increasing the risk of accidents. The issue goes beyond the absence of infrastructure—existing sidewalks can also be problematic. For example, sidewalks that are too narrow or obstructed can further elevate the risk of accidents.

To better understand how infrastructure relates to the population, we examined how sidewalk availability varies by CBG.

Map showing how sidewalk availability varies by census block group (CBG) in Chicago.
A sample map illustrating how sidewalk availability varies by census block groups in Chicago.

We then overlayed crash data involving pedestrians to see how these relate to the amount of sidewalks per CBG. Overall, while pedestrian crashes are dispersed throughout the city, there seems to be a relationship between the number of these crashes and the amount of sidewalks in northeastern CBGs.

If we visualize the total amount of sidewalks per CBG by the number of crashes in that CBG involving pedestrians, we can see where a lack of sidewalks may be leading to more pedestrian-involved crashes. This confirms our observation that sidewalk coverage is related to pedestrian crashes in the northeastern part of the city.

Map examining how sidewalk availability varies by census block group (CBG) in Chicago.
A sample map examining how sidewalk availability varies by census block group in Chicago.

Our earlier census data analysis highlighted that CBGs where walking to work is the most popular commuting method are more likely to have crashes, so we can also layer in historical crash data to find hot spots (dark purple) where pedestrians are most at risk for crashes due to lack of sidewalk access. Again, the northeastern part of the city seems to be a good candidate for sidewalk infrastructure improvements to reduce the likelihood of pedestrian crashes.

Map comparing sidewalk availability per census block group (CBG) to pedestrian-involved crashes and populations walking to work.
A sample map comparing sidewalks per census block group to crashes involving pedestrians and populations walking to work.

Our team conducted a similar analysis on another critical piece of pedestrian infrastructure: crosswalks. We found that, particularly in the northeastern part of the city, many pedestrian-involved crashes occurred in CBGs with fewer crosswalks. When we visualized the crosswalk data alongside pedestrian-related crashes, the same hotspots emerged. Additionally, by integrating commuter data, we began to identify areas where the lack of crosswalks poses a greater risk to walking commuters. To explore our findings and data in greater detail, click here.

Overall, layering demographic data with historical crash data and infrastructure maps provides incredibly valuable insights into where improvements can be made to enhance transportation safety.

Digitize transportation infrastructure with AI for deeper analysis and insights

The examples presented in this blog are just a few of the many safety analytics use cases unlocked with high-precision transportation vector layers. At Ecopia, we work with MPOs and DOTs across the US, as well as leading transportation authorities around the world, to create comprehensive, accurate, and up-to-date maps for strategic decision-making. This data opens up new opportunities for analysis and improvements in infrastructure not possible without a digital source of truth for current transportation networks. What's more, our AI-based mapping systems can produce GIS-professional quality maps across an entire city or state in just a matter of weeks without any resources spent on manual digitization.

Whether you're working on active transportation planning, multimodal network analysis, Americans with Disabilities Act (ADA) compliance, green infrastructure creation, or another use case requiring high-precision geospatial data, let Ecopia scale your data creation so you can focus on what really matters: analyzing information and implementing positive changes. Our team also regularly works with government organizations to align federal funding opportunities with geospatial data creation initiatives. For more information, get in touch

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