A very initial look at 2010 bike crash data for Chicago


The intersection of Grand/Milwaukee/Halsted has the third highest incidence of collisions between automobiles and bicycles at Milwaukee Avenue intersections. Will bicycle crash data help city planners focus their attention on improving safety at the spots with the most frequent crashes? 

I recently obtained from the Illinois Department of Transportation (IDOT) the 2010 vehicle crash data, which includes collisions between automobile drivers, bicyclists, pedestrians. I plan to update the Crash Portal with this information. But I also plan to do something more than make a map; Derek Eder*, myself, and others will dig deeper into the data to see what story we can tell with it. We’ll do that in addition to listing and visualizing statistics that citizen cyclists are more accustomed to, like the change in crash rates year after year.

So what happened in 2009?

In 2009, there were 1,484 reported crashes involving bicyclists. Six bicyclists died in these crashes.

IDOT will not be reporting dooring crashes prior to 2010; it’s unclear if they even collected this information prior to 2010.

And what’s happened in 2010?

In 2010, there were 1,643 reported crashes involving bicyclists. Five bicyclists died in these crashes.

When I posted this on my personal Twitter on Tuesday, someone asked, “Is the increase because of doorings?”

Good question and I didn’t know the answer. But I would quickly find out, by asking IDOT, that the crash dataset does NOT include instances of doorings – those are listed in a separate report and the datasets are exclusive of each other. That report, which you can access yourself after receiving the login credentials from IDOT, shows 127 reported doorings.

Add this to the non-dooring crashes and there were 1,770 reported crashes involving bicyclists.

It’s important to know that Active Transportation Alliance, Jon Hilkevitch at the Chicago Tribune, and possibly my own blogging, prompted Governor Quinn in April 2011 to direct IDOT to collect and report information about dooring-type crashes.

What about doorings in 2011?

I checked the report online Tuesday, September 6, 2011, and data was current up until August 8, 2011. There were 164 reported dooring crashes in that time period. This year is on track to see more reporting dooring crashes than last year. This could indicate that 2011 will also have more reported crashes than 2010. If that rate continues (0.75 reported doorings per day), then 2011 will see 273 doorings, or more than twice as many as were reported in 2010.

You can avoid being doored by watching for people in cars (which could mean they may be getting out of the car) and ride outside the door zone. The door zone is equal to a width of an open car door. This may mean the entire width of many bike lanes in Chicago!


Mockup of a pavement marking that might appear in the bike lane to warn bicyclists of the door zone. Photo by Gary Kavanagh. 


Would these markings in the bike lane encourage bicyclists to ride outside the door zone? San Francisco hopes to find out in this experiment. What can we do to reduce the incidence at crashes where they most often occur, at intersections? See photo below. Photo by Lee Dennis.

Why the increase between 2009 and 2010?

The first explanation I proffer is that more crashes are being reported than before. Perhaps people are convinced of the value in reporting crashes (I doubt this, as it’s hard to explain with sufficient persuasion). There is no research that can validate this.

The second is that more people are bicycling in 2010 than 2009 and while road users are adjusting to each other’s presence, the crash rate rises with the bicycling rate. However, we have no data yet, or even a dataset acting as a proxy, that reports on ridership in Chicago in 2010. There is data for 2009, but it only reports on people 16 and older who bicycle to work (from the American Community Survey). I’ve written on Steven Can Plan about this need for more information on bicycle ridership, research that goes beyond information about the journey to work, and that includes information about all the reasons for trips people make (shopping, social, school, etc.).



To reduce the incidence of the most common location and moment of crash, during a turn at an intersection, Chicago planners could adopt many of the features they first implemented in the Kinzie Street protected bike lane. These features were inspired by the National Association of City Transportation Officials’ (NACTO) “Urban Bikeway Design Guide.” Chicago is a founding member of NACTO. 

Notes on the data

Data in this post may be different than that found in the data table that supports the first bike crash map. This is because I now have the full dataset from IDOT and I’m creating my own database join, which may be different than the method IDOT used to create its “pedalcyclist extracts.” I do this because the method IDOT uses left out one bicyclist fatality in 2009 because the bicyclist was not the first point of impact in the crash.

I join the Crash and Persons table based on their common field of “casenumber.” I search the Persons table for a Person Type of “3” (pedalcyclist). With the resulting casenumbers, I then search the Crash table. This method returns ALL crashes in which pedalcyclists were involved, whether or not they were the first point of impact in the crash.

I am not allowed to share the complete dataset with anyone – each researcher has to individually accept the privacy laws that controls the release of this data. You can obtain the dataset yourself from IDOT. If you are interested in a project on bicyclist or pedestrian crash data, I will help you obtain it. You may ask me for the exact queries I used to extract the figures in this article.

*Derek and I worked on the crash data after I created the first Chicago bike crash map.

8 thoughts on “A very initial look at 2010 bike crash data for Chicago”

  1. This is great that you are taking initiative to take a look at the data.  I have live in a neighborhood where there are fireman and paramedics. What they told me is more times than not when they respond to collisions between bike and car is that the cyclist was found to be intoxicated. Not to say that the driver may be on the straight but I found it interesting hearsay.  Perhaps there can be more data regarding this revelation?

    Also is there any data on collisions between bikes and pedestrians on the bike path? I bike to volleyball on North Ave Beach and I can’t keep count of how many times there is an ambulance for the crashes that occur in the more populated areas of the bike path.

    1. I will check the crash data to see if it mentions alcohol in the cyclist. I know it does for the driver, but the crash reports always collect more information about the people sitting in or driving a car. 

      The data only includes crash reports where cars are involved, so no bike-bike, bike-ped, ped-ped crashes. I submitted a Freedom of Information Act (FOIA) request to the Chicago Police Department asking for crash reports between bicyclists and pedestrians and they could not provide the data (I don’t recall the exact response, or if they said why they couldn’t provide it – it’s probably in a letter on my desk somewhere). 

      Another data source I haven’t attempted to collect is that of EMT responses. This is how the Boston Cyclists Union built its bike crash map, using data from hospitals and ambulance services. 

  2. My unofficial estimate, based on my experience is that close to 1/3 of all bicycle collisions in Chicago are doorings.  From your post, it isn’t clear the percentage that doorings would compromise of all bicycle collisions, but it looks like it is substantially less than 1/3.  Is it possible that we’re still having problems getting doorings reported to IDOT?

    1. There may be a problem of getting ALL kinds of bicycle crashes reported to the police. Dooring crashes may be underreported compared to non-dooring crashes. If you compare how many crashes occur with how many crashes are reported, then you would have a solid inference on how many crashes are not reported. But without a survey of a random sampling of people in Chicago who ride bicycles about their crashes, a sample that would be very hard to obtain, we cannot know how many crashes actually occur. 

      Reporting a crash is a very personal issue. There are very personal reasons involved for reporting it or not reporting it. Some factors are time available to report a crash, injury severity, convenience or inconvenience of reporting, fear of repercussions, lack or presence of health insurance, etc…

      “Dooring crashes made up 7.2% of reported crashes involving bicyclists in 2010, in the Chicago city limits.” That’s an objective statement describing what happened in 2010 regarding dooring crashes. 

  3. Very nice work. I think more detailed crash data would be very useful for many reasons. I have been comparing this type of data from NYC, NC, and Orlando, and the results were highly counter-intuitive. The percent deaths from dooring was 0.4%, 0.2%, and 0% respectively.

    I see that post on the internet focus on the door zone without discussing how absurdly rare it is for someone to die of it. In NYC, for roughly 800,000 cyclists, a single person was door in a decade!

    Traffic data is ever changing, and no one set of data is definitive. Thus, I’d like to see more information on this topic.

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